Podcast
Questions and Answers
What is the optimal environment for the growth of Clostridium species on enriched media?
What is the optimal environment for the growth of Clostridium species on enriched media?
- 15-25% CO2
- 5-15% CO2
- 10-20% O2
- 2-10% CO2 (correct)
What differentiates neurotropic Clostridium species from other types?
What differentiates neurotropic Clostridium species from other types?
- Exogenous infections via respiratory contamination
- Production of endotoxins specific to the intestinal tract
- Non-invasive action with neurotoxin targeting neuronal cells (correct)
- Invasive properties with high-potency exotoxins
Which species of animal is most susceptible to Tetanus?
Which species of animal is most susceptible to Tetanus?
- Horses (correct)
- Birds
- Sheep
- Carnivores
How does Tetanus toxin (TeNT) travel to the CNS?
How does Tetanus toxin (TeNT) travel to the CNS?
Where are Clostridium species commonly found causing exogenous infections?
Where are Clostridium species commonly found causing exogenous infections?
What characterizes spastic paralysis caused by Tetanus toxin?
What characterizes spastic paralysis caused by Tetanus toxin?
What is a common mode of Tetanus infection in animals?
What is a common mode of Tetanus infection in animals?
Which statement is true about Clostridium tetani?
Which statement is true about Clostridium tetani?
Why do Clostridium endospores bulge the mother cell?
Why do Clostridium endospores bulge the mother cell?
What is the primary route for Tetanus spore entry into the body?
What is the primary route for Tetanus spore entry into the body?
What is a characteristic clinical sign of systemic tetanus?
What is a characteristic clinical sign of systemic tetanus?
Which of the following mechanisms is primarily inhibited by botulinum toxin, resulting in paralysis?
Which of the following mechanisms is primarily inhibited by botulinum toxin, resulting in paralysis?
Opisthotonus, seen in systemic tetanus, is best described as what?
Opisthotonus, seen in systemic tetanus, is best described as what?
In local tetanus, what type of autonomic nervous system symptoms can be observed?
In local tetanus, what type of autonomic nervous system symptoms can be observed?
Which animal is considered a natural reservoir for botulism?
Which animal is considered a natural reservoir for botulism?
What is a significant predisposing factor for toxico-infection botulism in animals?
What is a significant predisposing factor for toxico-infection botulism in animals?
Foals with Shaker Foal Syndrome predominantly exhibit what symptom?
Foals with Shaker Foal Syndrome predominantly exhibit what symptom?
How does botulism primarily cause respiratory failure?
How does botulism primarily cause respiratory failure?
Botulism in animals is primarily characterized by which of the following signs?
Botulism in animals is primarily characterized by which of the following signs?
Why does botulism affect only the motor systems and not the sensory systems?
Why does botulism affect only the motor systems and not the sensory systems?
What is the primary source of clostridial infections?
What is the primary source of clostridial infections?
What is the primary effect of the toxins produced by Clostridioides difficile?
What is the primary effect of the toxins produced by Clostridioides difficile?
What is the primary route of transmission of Clostridioides difficile?
What is the primary route of transmission of Clostridioides difficile?
What is the characteristic histopathological finding in Clostridioides difficile infections?
What is the characteristic histopathological finding in Clostridioides difficile infections?
What is the primary factor that predisposes to enteric clostridial infections?
What is the primary factor that predisposes to enteric clostridial infections?
What is the primary mode of action of pore-forming toxins?
What is the primary mode of action of pore-forming toxins?
What is the primary effect of toxins produced by C. perfringens?
What is the primary effect of toxins produced by C. perfringens?
What is the characteristic clinical sign of Clostridioides difficile infections in horses?
What is the characteristic clinical sign of Clostridioides difficile infections in horses?
What is the primary mechanism of action of the toxins produced by Clostridioides difficile?
What is the primary mechanism of action of the toxins produced by Clostridioides difficile?
What is the primary difference between Clostridioides difficile and C. perfringens?
What is the primary difference between Clostridioides difficile and C. perfringens?
Which proteins are essential for membrane fusion and docking of vesicles involved in neurotransmission?
Which proteins are essential for membrane fusion and docking of vesicles involved in neurotransmission?
What is the primary result of Botulinum toxin's action at motor neuron endings?
What is the primary result of Botulinum toxin's action at motor neuron endings?
Which protein involved in neurotransmission is anchored specifically to the synaptic vesicle membrane?
Which protein involved in neurotransmission is anchored specifically to the synaptic vesicle membrane?
What mechanism allows clostridial neurotoxins to block exocytosis of neurotransmitters?
What mechanism allows clostridial neurotoxins to block exocytosis of neurotransmitters?
Where is SNAP25 anchored in the process of neurotransmission?
Where is SNAP25 anchored in the process of neurotransmission?
How do Botulinum and Tetanus toxins become active neurotoxins?
How do Botulinum and Tetanus toxins become active neurotoxins?
Which structure links the light and heavy chains in active clostridial neurotoxins?
Which structure links the light and heavy chains in active clostridial neurotoxins?
What is the primary effect of Tetanus toxin on central inhibitory interneurons?
What is the primary effect of Tetanus toxin on central inhibitory interneurons?
Which vesicle docking protein is anchored to the plasma membrane?
Which vesicle docking protein is anchored to the plasma membrane?
What role do the L chains of clostridial neurotoxins play in their mechanism of action?
What role do the L chains of clostridial neurotoxins play in their mechanism of action?
Which Clostridium species is associated with abomasitis and enterotoxemia in sheep when they feed on frozen grass during winter?
Which Clostridium species is associated with abomasitis and enterotoxemia in sheep when they feed on frozen grass during winter?
What is the role of cytotoxin CctA produced by C. chauvoie in infected animals?
What is the role of cytotoxin CctA produced by C. chauvoie in infected animals?
What triggers the dormancy of Clostridium spores in infected tissues until favorable conditions arise?
What triggers the dormancy of Clostridium spores in infected tissues until favorable conditions arise?
Which Clostridium species produces alpha and beta toxins that are lethal and necrotizing, as well as pore-forming cytolysins?
Which Clostridium species produces alpha and beta toxins that are lethal and necrotizing, as well as pore-forming cytolysins?
Which feature is characteristic of C. chauvoie infection concerning tissue lesions?
Which feature is characteristic of C. chauvoie infection concerning tissue lesions?
Which condition is necessary for the spores of C. septicum to germinate and cause malignant edema?
Which condition is necessary for the spores of C. septicum to germinate and cause malignant edema?
How are the toxins produced by enteropathogenic Clostridium species absorbed and what do they cause?
How are the toxins produced by enteropathogenic Clostridium species absorbed and what do they cause?
What event can trigger the germination of Clostridium perfringens endospores in an animal's GI tract?
What event can trigger the germination of Clostridium perfringens endospores in an animal's GI tract?
What is the clinical presentation of animals affected by blackleg caused by C. chauvoie?
What is the clinical presentation of animals affected by blackleg caused by C. chauvoie?
Why do pathogens of Clostridium species remain highly persistent in the environment?
Why do pathogens of Clostridium species remain highly persistent in the environment?
What is the primary characteristic of the Enterobacteriaceae family?
What is the primary characteristic of the Enterobacteriaceae family?
What is the arrangement of flagella in motile Enterobacteriaceae species?
What is the arrangement of flagella in motile Enterobacteriaceae species?
What is the primary habitat of Enterobacteriaceae species?
What is the primary habitat of Enterobacteriaceae species?
What is the term for species that ferment lactose in the Enterobacteriaceae family?
What is the term for species that ferment lactose in the Enterobacteriaceae family?
Which of the following is not a characteristic of the genus Escherichia?
Which of the following is not a characteristic of the genus Escherichia?
What is the concentration of E. coli in the large intestine?
What is the concentration of E. coli in the large intestine?
What is the primary disease caused by E. coli in neonates?
What is the primary disease caused by E. coli in neonates?
Which of the following is not a pathogenic species in the Enterobacteriaceae family?
Which of the following is not a pathogenic species in the Enterobacteriaceae family?
What is the primary difference between pathogenic and opportunistic pathogens in the Enterobacteriaceae family?
What is the primary difference between pathogenic and opportunistic pathogens in the Enterobacteriaceae family?
How do Enterobacteriaceae species reduce nitrates?
How do Enterobacteriaceae species reduce nitrates?
What is the primary cause of shock in enteric colibacillosis?
What is the primary cause of shock in enteric colibacillosis?
Which epithelial cells are affected by enterotoxins produced by ETEC strains?
Which epithelial cells are affected by enterotoxins produced by ETEC strains?
What is the primary route of entry for E. coli in enteric colibacillosis?
What is the primary route of entry for E. coli in enteric colibacillosis?
What is the primary role of adhesins produced by ETEC strains?
What is the primary role of adhesins produced by ETEC strains?
What is the characteristic clinical sign of enteric colibacillosis?
What is the characteristic clinical sign of enteric colibacillosis?
Why are fimbrial adhesins F4, F5, F6, and F41 host and species specific?
Why are fimbrial adhesins F4, F5, F6, and F41 host and species specific?
What is the primary mechanism of action of enterotoxins produced by ETEC strains?
What is the primary mechanism of action of enterotoxins produced by ETEC strains?
What is the primary result of enteric colibacillosis complicated by shock?
What is the primary result of enteric colibacillosis complicated by shock?
What is the primary difference between enteric colibacillosis and uncomplicated enteric colibacillosis?
What is the primary difference between enteric colibacillosis and uncomplicated enteric colibacillosis?
What is the primary role of lipopolysaccharides in enteric colibacillosis?
What is the primary role of lipopolysaccharides in enteric colibacillosis?
What is the primary critical virulence factor of EHEC?
What is the primary critical virulence factor of EHEC?
What is the characteristic clinical presentation of pigs affected by edema disease?
What is the characteristic clinical presentation of pigs affected by edema disease?
What is the primary mechanism of Shiga toxin action in endothelial cells?
What is the primary mechanism of Shiga toxin action in endothelial cells?
What is the primary receptor for Shiga toxin on erythrocytes?
What is the primary receptor for Shiga toxin on erythrocytes?
What is the primary predisposing factor for STEC infections in pigs?
What is the primary predisposing factor for STEC infections in pigs?
What is the primary site of Shiga toxin absorption in pigs?
What is the primary site of Shiga toxin absorption in pigs?
What is the primary consequence of Shiga toxin action on endothelial cells?
What is the primary consequence of Shiga toxin action on endothelial cells?
What is the primary difference between EHEC and STEC?
What is the primary difference between EHEC and STEC?
What is the primary consequence of edema disease in pigs?
What is the primary consequence of edema disease in pigs?
What is the primary site of Shiga toxin binding in the body?
What is the primary site of Shiga toxin binding in the body?
Which animal experiences diarrhea caused by Enteropathogenic E.coli within 3-12 days of birth with a mortality rate of up to 100%?
Which animal experiences diarrhea caused by Enteropathogenic E.coli within 3-12 days of birth with a mortality rate of up to 100%?
What is the primary cause of diarrhea in animals affected by Enteropathogenic E.coli?
What is the primary cause of diarrhea in animals affected by Enteropathogenic E.coli?
Which protein interaction is crucial for creating intimate contact between Enteropathogenic E.coli and host cells?
Which protein interaction is crucial for creating intimate contact between Enteropathogenic E.coli and host cells?
What type of lesions are primarily seen under the microscope in cases of Enteropathogenic E.coli infection?
What type of lesions are primarily seen under the microscope in cases of Enteropathogenic E.coli infection?
What role does the Type III secretion system (T3SS) play in Enteropathogenic E.coli infections?
What role does the Type III secretion system (T3SS) play in Enteropathogenic E.coli infections?
In Enteropathogenic E.coli pathogenesis, what structure forms as a result of cytoskeletal rearrangement?
In Enteropathogenic E.coli pathogenesis, what structure forms as a result of cytoskeletal rearrangement?
In Enteropathogenic E.coli infections, which cellular structure is reabsorbed, leading to the effacement of microvilli?
In Enteropathogenic E.coli infections, which cellular structure is reabsorbed, leading to the effacement of microvilli?
Which animals are commonly associated with Enteropathogenic E.coli induced diarrhea in pet stores and kennels?
Which animals are commonly associated with Enteropathogenic E.coli induced diarrhea in pet stores and kennels?
What is the primary reason Enteropathogenic E.coli does not produce typical enterotoxins?
What is the primary reason Enteropathogenic E.coli does not produce typical enterotoxins?
What type of intestinal changes cause diarrhea in Enteropathogenic E.coli infections?
What type of intestinal changes cause diarrhea in Enteropathogenic E.coli infections?
What is the primary function of siderophores in ExPEC?
What is the primary function of siderophores in ExPEC?
How do ExPEC strains gain access to the body?
How do ExPEC strains gain access to the body?
What is the result of insufficient passive immunity in animals?
What is the result of insufficient passive immunity in animals?
What is the outcome of ExPEC proliferation in lymphatics and bloodstream?
What is the outcome of ExPEC proliferation in lymphatics and bloodstream?
What is the role of adhesins in ExPEC pathogenesis?
What is the role of adhesins in ExPEC pathogenesis?
What is the outcome if antibacterial therapy and immune system are unable to remove ExPEC?
What is the outcome if antibacterial therapy and immune system are unable to remove ExPEC?
Which of the following is NOT a virulence factor of ExPEC?
Which of the following is NOT a virulence factor of ExPEC?
What is the mechanism of ExPEC entry into lymphatics?
What is the mechanism of ExPEC entry into lymphatics?
What is the outcome of ExPEC infection in animals?
What is the outcome of ExPEC infection in animals?
What is a characteristic of Septicemic E. coli (SEPEC)?
What is a characteristic of Septicemic E. coli (SEPEC)?
Which characteristic is most commonly associated with Uropathogenic E.coli (UPEC) infections in dogs?
Which characteristic is most commonly associated with Uropathogenic E.coli (UPEC) infections in dogs?
What is a notable histopathological feature in ruminants affected by coli strains in their early days of life?
What is a notable histopathological feature in ruminants affected by coli strains in their early days of life?
What predisposing factor is commonly associated with cystic endometrial hyperplasia in bitches during UPEC infections?
What predisposing factor is commonly associated with cystic endometrial hyperplasia in bitches during UPEC infections?
Which clinical syndrome is NOT commonly associated with Avian Pathogenic E.coli (APEC) infections?
Which clinical syndrome is NOT commonly associated with Avian Pathogenic E.coli (APEC) infections?
What is a common presentation of E.coli mastitis in dairy cattle two weeks post parturition?
What is a common presentation of E.coli mastitis in dairy cattle two weeks post parturition?
Which factor commonly affects the nature of E.coli mastitis developed in dairy cattle?
Which factor commonly affects the nature of E.coli mastitis developed in dairy cattle?
Which description best fits the pathogenesis of Uropathogenic E.coli (UPEC) in dogs?
Which description best fits the pathogenesis of Uropathogenic E.coli (UPEC) in dogs?
Which systemic effect is primarily attributed to absorbed E.coli lipopolysaccharide (LPS) in UPEC infections?
Which systemic effect is primarily attributed to absorbed E.coli lipopolysaccharide (LPS) in UPEC infections?
Which effect is commonly seen during the periparturient period in cows with E.coli mastitis?
Which effect is commonly seen during the periparturient period in cows with E.coli mastitis?
What distinguishes Uropathogenic E.coli strains causing pyometra in canines?
What distinguishes Uropathogenic E.coli strains causing pyometra in canines?
What is the primary purpose of serotyping in E. coli differentiation?
What is the primary purpose of serotyping in E. coli differentiation?
What is the primary role of adhesins in E. coli?
What is the primary role of adhesins in E. coli?
Which of the following is NOT a type of adhesin in E. coli?
Which of the following is NOT a type of adhesin in E. coli?
What is the primary association of F4 adhesin in E. coli?
What is the primary association of F4 adhesin in E. coli?
What is the primary role of fimbrial antigens in E. coli?
What is the primary role of fimbrial antigens in E. coli?
How many virulence factors are associated with E. coli?
How many virulence factors are associated with E. coli?
What is the primary association of F17 adhesin in E. coli?
What is the primary association of F17 adhesin in E. coli?
What is the primary role of enterotoxins in E. coli?
What is the primary role of enterotoxins in E. coli?
What is the primary association of F165 adhesin in E. coli?
What is the primary association of F165 adhesin in E. coli?
What is the primary characteristic of F6 adhesin in E. coli?
What is the primary characteristic of F6 adhesin in E. coli?
Which type of toxin causes disturbances in the intestinal fluid metabolism without causing morphological lesions in the mucosa?
Which type of toxin causes disturbances in the intestinal fluid metabolism without causing morphological lesions in the mucosa?
What is the mechanism of action of Shiga toxin in endothelial cells?
What is the mechanism of action of Shiga toxin in endothelial cells?
Which enterotoxin opens enterocyte calcium channels leading to an influx of Ca2+?
Which enterotoxin opens enterocyte calcium channels leading to an influx of Ca2+?
Which heat-labile enterotoxin causes permanent activation of adenylyl cyclase?
Which heat-labile enterotoxin causes permanent activation of adenylyl cyclase?
What is the primary effect of heat-labile enterotoxin on enterocytes?
What is the primary effect of heat-labile enterotoxin on enterocytes?
Which toxin does not cause diarrhea on its own and requires the secretion of other toxins?
Which toxin does not cause diarrhea on its own and requires the secretion of other toxins?
Which cyclomodulin is known to inhibit the cell cycle?
Which cyclomodulin is known to inhibit the cell cycle?
Which of the following is a common result of hemolysins' action on red blood cells?
Which of the following is a common result of hemolysins' action on red blood cells?
What is the primary consequence of shiga toxin upregulating proinflammatory cytokines in monocytes?
What is the primary consequence of shiga toxin upregulating proinflammatory cytokines in monocytes?
What is the primary impact of high intracellular cAMP concentration caused by heat-labile enterotoxins?
What is the primary impact of high intracellular cAMP concentration caused by heat-labile enterotoxins?
What is the primary purpose of serotyping in E.coli?
What is the primary purpose of serotyping in E.coli?
What type of antigens is used for identification and characterization of E.coli strains?
What type of antigens is used for identification and characterization of E.coli strains?
What is the role of adhesins in E.coli?
What is the role of adhesins in E.coli?
Which adhesin is commonly found in E.coli strains that cause urinary tract infections (UTIs)?
Which adhesin is commonly found in E.coli strains that cause urinary tract infections (UTIs)?
Which of the following adhesins is associated with E.coli strains that cause colibacillosis in animals?
Which of the following adhesins is associated with E.coli strains that cause colibacillosis in animals?
What is the primary function of enterotoxins produced by E.coli?
What is the primary function of enterotoxins produced by E.coli?
How are enterotoxins encoded in E.coli?
How are enterotoxins encoded in E.coli?
What is the primary characteristic of F6 adhesin?
What is the primary characteristic of F6 adhesin?
Which adhesin is associated with E.coli strains that cause septicemia in calves?
Which adhesin is associated with E.coli strains that cause septicemia in calves?
What is the primary difference between F4 and F5 adhesins?
What is the primary difference between F4 and F5 adhesins?
What is the main effect of heat-stable enterotoxins (STa) on enterocytes?
What is the main effect of heat-stable enterotoxins (STa) on enterocytes?
Which factor is NOT directly associated with the mechanism of Shiga toxins?
Which factor is NOT directly associated with the mechanism of Shiga toxins?
How does heat-labile enterotoxin LT1 primarily cause diarrhea?
How does heat-labile enterotoxin LT1 primarily cause diarrhea?
Which enterotoxin is noted for increasing the permeability of the intestinal epithelium and causing loss of villous epithelial cells?
Which enterotoxin is noted for increasing the permeability of the intestinal epithelium and causing loss of villous epithelial cells?
Regarding the stability of enterotoxins under heat, which statement is MOST accurate?
Regarding the stability of enterotoxins under heat, which statement is MOST accurate?
What is the role of hemolysins in bacterial infections?
What is the role of hemolysins in bacterial infections?
Which confirmatory sign of epithelial cell damage is linked to Shiga toxin's action?
Which confirmatory sign of epithelial cell damage is linked to Shiga toxin's action?
Which component is common between East1 and STa toxins?
Which component is common between East1 and STa toxins?
What effect does STb (T2) have on intracellular processes in enterocytes?
What effect does STb (T2) have on intracellular processes in enterocytes?
Which condition is primarily caused by the action of heat-labile enterotoxins resulting in metabolic acidosis and death?
Which condition is primarily caused by the action of heat-labile enterotoxins resulting in metabolic acidosis and death?
What is the primary reason why neonates under 1 week of age are more susceptible to E. coli infection?
What is the primary reason why neonates under 1 week of age are more susceptible to E. coli infection?
Which of the following is NOT a method of controlling and preventing E. coli infection?
Which of the following is NOT a method of controlling and preventing E. coli infection?
What is the primary function of commercially produced preparations containing monoclonal antibodies to ETEC adhesins?
What is the primary function of commercially produced preparations containing monoclonal antibodies to ETEC adhesins?
What is the primary characteristic of the genus Salmonella?
What is the primary characteristic of the genus Salmonella?
What is the primary reservoir for Salmonella species?
What is the primary reservoir for Salmonella species?
What is the primary reason why Salmonella species are important?
What is the primary reason why Salmonella species are important?
What is the primary difference between S. enterica subsp. enterica and other subspecies of Salmonella?
What is the primary difference between S. enterica subsp. enterica and other subspecies of Salmonella?
What is the primary method of prevention and control of E. coli infections?
What is the primary method of prevention and control of E. coli infections?
What is the primary reason why E. coli infections are more common in intensive husbandry practices?
What is the primary reason why E. coli infections are more common in intensive husbandry practices?
What is the primary reason why E. coli bacteria can survive for weeks to months in moist, shaded environments?
What is the primary reason why E. coli bacteria can survive for weeks to months in moist, shaded environments?
In what environmental conditions can Salmonellae survive for nine months or more?
In what environmental conditions can Salmonellae survive for nine months or more?
Which host factor does NOT affect the outcome of salmonellosis?
Which host factor does NOT affect the outcome of salmonellosis?
Which serotype of Salmonella affects cattle specifically?
Which serotype of Salmonella affects cattle specifically?
What pathologic change is seen in the septicemic form of salmonellosis?
What pathologic change is seen in the septicemic form of salmonellosis?
What is the primary method of transmission for Salmonella?
What is the primary method of transmission for Salmonella?
Which factor primarily influences the severity of a Salmonella infection?
Which factor primarily influences the severity of a Salmonella infection?
What clinical sign is typically observed in acute enteritis with septicemia caused by salmonellosis?
What clinical sign is typically observed in acute enteritis with septicemia caused by salmonellosis?
What host cell interaction is crucial for the pathogenesis of Salmonella?
What host cell interaction is crucial for the pathogenesis of Salmonella?
Which of the following is a common clinical sign of salmonellosis in young ruminants?
Which of the following is a common clinical sign of salmonellosis in young ruminants?
What is a typical feature of acute enteritis without septicemia in salmonellosis?
What is a typical feature of acute enteritis without septicemia in salmonellosis?
Which of the following serovars is less virulent in chicks, but can colonize the intestine and cause human food poisoning?
Which of the following serovars is less virulent in chicks, but can colonize the intestine and cause human food poisoning?
What is the primary mode of transmission of S.Pullorum?
What is the primary mode of transmission of S.Pullorum?
What is the primary clinical sign of Fowl typhoid caused by S.Gallinarum?
What is the primary clinical sign of Fowl typhoid caused by S.Gallinarum?
What is the outcome for birds that survive Pullorum disease?
What is the outcome for birds that survive Pullorum disease?
What is the primary route of infection for S.Gallinarum?
What is the primary route of infection for S.Gallinarum?
What is the primary difference between Pullorum disease and Fowl typhoid?
What is the primary difference between Pullorum disease and Fowl typhoid?
What is the primary effect of S.Pullorum infection in breeding stock?
What is the primary effect of S.Pullorum infection in breeding stock?
What is the primary consequence of S.Gallinarum infection in adult birds?
What is the primary consequence of S.Gallinarum infection in adult birds?
Study Notes
Genus Clostridium
- Widely distributed in soil, freshwater, and marine sediments globally
- Many pathogenic strains are normal inhabitants of intestinal tracts and cause endogenous infections
- Others are present in soil and cause exogenous infections via wound contamination
- 14 species are significant in veterinary medicine
- Most produce ≥1 exotoxins with varying potency
Characteristics
- Gram +’ve
- Large rods
- Anaerobic
- 2-10% CO2 is optimal environment for growth on enriched media
- Endospore producing
- Endospores usually bulge the mother cell
Classification of Clostridia
- Based on potency and the invasive ability of the toxins
- Three different classifications:
- Neurotropic
Clostridium Tetani
- Produces potent non-invasive neurotoxins
- Colonizes hosts to a limited extent
- Toxins specifically target neuronal cells in animals and humans
- Causes spastic paralysis
- Acts at inhibitory interneurons
- Tetanus toxin only produced by C.tetani
- Ubiquitous organism in soils globally
- Horses are most susceptible species, carnivores less-so, and birds are resistant
- Tetanus in animals is mostly seen in horses and sheep, and is almost always fatal
- Wound contamination from spores in the soil, feces, dust, contaminated equipment
- Sporadic infections most stemming from poor management practices
- Tetanus only occurs through wound contamination
Tetanus Infection
- Spores germinate into vegetative cells where they begin to multiply and produce the neurotoxin
- Toxin (TeNT) enters peripheral nerve endings and proceeds to the CNS via retrograde axonal transport
- Once it reaches the CNS it inhibits the release of inhibitory neurotransmitters causing spastic paralysis
- Characterized by hyperactivity of voluntary muscles leading to rigidity and tetanic spasms
- Tonic, involuntary, and prolonged muscle contractions
- Spasms- shorter lasting muscle contractions triggered by sensory stimuli (light, touch, noise)
Clinical Signs of Tetanus
- Can present locally or systemically
- Systemic tetanus:
- Increased spasticity of masticatory muscles followed by progressively more spastic paralysis of the trunk and limb muscles
- Rigidity of masseter and temporal muscles→ inability to open mouth
- Spastic paralysis of extensors of the back and neck are accompanied by Opisthotonus (abnormal, extremely arched posture caused by muscle spasms)
- Local tetanus:
- Muscles of affected limb or region become painful and eventually spastic
- Seen in animals that are more resistant to tetanus toxin (dogs, cats, etc.)
- Autonomic nervous system is affected and causes tachycardia, hypertension, sweating, and then alternates with bradycardia, hypotension due to respiratory failure
- Respiratory failure caused by diaphragmatic, laryngeal, and respiratory muscle spasms
Clostridium Botulinum
- Produces potent non-invasive neurotoxins
- Acts at motor neuron endings
- Causes flaccid paralysis
- Botulinum toxin is also produced by C.butyricum and C.baratii
- Widespread in soils, lake, and sea sediments
- Toxins are divided into 9 types based on antisera and biological effects (A, B, C, D, E, F, G, H, J, X) and 40 subtypes
- Variations may affect biological functions
- Recognition, invasion efficiency, persistence, enzymatic activity
- Most common in cattle, horses, and birds
- Birds are considered botulism reservoirs in nature
Botulism
- Botulism in animals has 3 forms:
- Toxico-infection (intestinal infection)
- Food-borne intoxication
- Wound Contamination
- Botulism is not contagious but can occur in groups of animals that are exposed to the same environments
- Botulism clinical signs usually present in animals affected by botulinum toxin types C and D
- No fever (afebrile)
- Progressive, symmetrical, flaccid paralysis and limb weakness
- Recumbency
- Respiratory difficulty
- Death occurring due to respiratory arrest
- Sensory nervous systems are unaffected, only motor
- No visible pathological changes
Clinical Signs of Botulism
- Cattle and Horses:
- Dysphagia
- Hypersalivation
- Decreased tongue tone
- Anorexia
- Constipation or Diarrhea
- Colics
- Foals (Shaker Foal Syndrome):
- Weakness and tremors of muscles in the limbs
Botulinum and Tetanus Toxins
- Share a common structure and are released from the bacterium
- Synthesized as a precursor, activated by proteolytic activity of Clostridium proteases or exogenous proteases (intestinal)
- Consist of a light chain and heavy chain linked by a disulfide bridge
Neurotransmission at the Neuromuscular Junction
- Peptide neurotransmitters are synthesized in the endoplasmic reticulum of neurons and stored in synaptic vesicles
- Vesicles move to the active zone (presynaptic) and dock close to calcium channels, ready for membrane fusion and release of neurotransmitters
- Three critical proteins involved in calcium-mediated exocytosis: VAMP, SNAP25, and Syntaxin, which form the SNARE Complex
- SNARE Complex brings the plasma membrane and vesicle into close contact for fusion and release of neurotransmitters
Mechanism of Action of Clostridial Neurotoxins
- Light chains of clostridial neurotoxins drive intracellular activity in target neurons
- Light chains cleave one of the three SNARE complex proteins, blocking exocytosis of neurotransmitters by impairing fusion of vesicles to the plasma membrane
- Botulinum toxins act at motor neuron endings, resulting in flaccid paralysis
- Tetanus toxin acts at central inhibitory interneurons, causing spastic paralysis
Histotoxic Clostridium (Gas Gangrene)
- Produce less potent but invasive toxins, causing histotoxic infections that destroy living tissues
- Enzymes and toxins cause damage
C.chauvoie (Blackleg)
- Causes disease in cattle between 2-24 months globally
- Rapid progression and high mortality
- Animals found dead without clinical signs
- May present with difficulty walking, recumbency before death
- Bacteria produce cytotoxin CctA, which is pore-forming and causes lesions
- Lesions typically in skeletal muscles in the leg or neck, can also develop in the diaphragm, tongue, or heart
C.septicum (Malignant Edema/Gas Gangrene/Braxy)
- Affects cattle, sheep, pigs, horses, and other animals of different ages
- Sheep: Abomasitis (braxy) and Enterotoxemia after feeding on frosted root crops and frozen grass during winter months
- Damage to mucosal epithelium of the abomasum allows for colonization and causes abomasitis and enterotoxemia
- Malignant edema (myositis): Introduction of the pathogen to an open wound, requiring an anaerobic environment
- Lesions begin with rapid swelling at the wound site, becoming distended by gas
- Swelling caused by inflammation and bloody subcutaneous edema fluid
- Gas caused by fermentation of sugars and compounds by Clostridium
- Diseased animals will become systemically ill and die within 36 hours of first lesion development, especially if left untreated
Other Clostridium Species
- C.novyi (Types A & B)
- C.haemolyticum
- Paeniclostrium sordellii
- C.perfringens (Type A)
Pathogenesis
- Spores are ingested and begin to colonize the intestinal tract
- Spores are carried from the intestine to tissues through the bloodstream or lymphatic system
- Spores remain dormant in tissues until conditions change, activating germination into vegetative cells
- Proliferation occurs in tissues as long as the environment remains anaerobic
C.perfringens
- Found in nature, present in soil, sewage, and contaminated foods
- Normal intestinal habitant, aerotolerant
- Can survive on aerobic surfaces and oxygen-exposed tissues, facilitating interhost transmission
- Highly persistent in the environment due to aerotolerance and heat-resistant endospores
- Germination triggered by biliary acids in the GI tract of mammals
- Secondary bile acids produced by resident commensal bacteria inhibit germination, proliferation, and colonization
Virulence Factors
- Toxins and non-toxin tissue-degrading enzymes with strain variations
- Toxins: Alpha (CPA), Beta (CPB) & Beta2 (CPB2), Enterotixin (CPE), Epsilons (ETX), Iota (ITX), Perfringolysins O (PFO)
- Enzymes: Sialidase, collagenase, proteases, hyaluronidase, etc.
- Three major classes based on their mode of action: Enzymes acting on cell surface, pore-forming toxins, and toxins acting in the cytoplasm (locally or systemically)
Predisposing Factors
- Enteric clostridial infections usually require predisposing conditions modifying the GI environment
- Nutrition (protein-rich, high digestible carbohydrate concentration in diet)
- Enhanced availability of nutrients through malabsorption or intestinal damage by other microorganisms
- Use of antibiotics
- Environmental contamination
- Increased gastric intestinal pH
Other C.perfringens Caused Diseases
- Fecal shedding is the main source of clostridial infections
- Bacterium can survive in the environment for years
- Acute severe hemorrhagic and necrotic enteritis in young animals, often fatal
Clostridioides difficile (formerly Clostridium difficile)
- Strict anaerobe, highly resistant spores
- Widespread in the large intestine of humans, animals, and fecally contaminated environments
- Transmission: Fecal-oral route, infections associated with antibiotic treatment
- Typhlocolitis: common hospital-acquired infections in humans
- Caused by the absence of microbial competition due to antibiotic treatments
- Two toxins (TcdA and TcdB) cause cell rounding and death, interfere with actin polymerization, causing fluid loss and diarrhea
Other Clostridioides difficile Caused Diseases
- Infections typically characterized by diarrhea, dehydration, toxemia, severe inflammation of the colon and cecum
- Especially occurs in animals with expanded and large intestines (horses)
- Mesocolic edema is characteristic in piglets
- Histopathologically, necrotizing and hemorrhagic defocalitis
Family Enterobacteriaceae
- 33 genera, 140 species
- Distributed in soil, water, on plants, insects, and intestinal tracts
- Some species cause significant intestinal or extraintestinal disease in most animals and humans
- Extraintestinal infections usually involve urinary tract, respiratory tract, systemic circulation, and wounds
- Species that ferment lactose are called Coliforms
- Important pathogenic species include Citrobacter, Cronobacter, Enterobacter, Escherichia, Klebsiella, Kluyvera, Raoultella, Salmonella, and Shigella
Characteristics of Enterobacteriaceae Family
- Gram negative, medium-sized rods
- Peritrichous arrangement of flagella if motile
- Facultatively anaerobic, glucose fermenters
- Catalase +ve, Oxidase -ve
- Capable of reducing nitrates to nitrites
- Grows on non-enriched media (e.g., Nutrient agar)
Genus Escherichia
- Gram negative enteric rod
- Family of Enterobacteriaceae
- 6 species (type genus of family with type species of genus)
- Only pathogenic species of importance in animals
- Dominant organism recovered facultatively anaerobic bacterium in most animal intestinal tracts
- Present at a level of 10^7-10^9 organisms per gram of feces
- Exception is birds, where E. coli is recovered in very low percentage of healthy birds
- Concentration of E. coli increases progressively from small to large intestine with the largest concentration being in large intestines
E. coli
- Causes septicemia in neonates in most species, especially in cows, dogs, kittens, pigs, lambs, and foals
- Causes opportunistic septicemia in older, immunocompromised animals
- In avian species, it causes sacculitis, omphalitis, and other systemic infectious manifestations
- Classification of E. coli: pathogenic strains are classified into pathotypes based on virulence factors and disease-causing mechanisms
Diarrheagenic E. coli
- Diarrheagenic strains (DEC) are economically important in porcine, cattle, and sheep industries
- E. coli causes septicemia in neonatal piglets, cows, and lambs
- Post-weaning diarrheal infections are most important in piglets
- Enterotoxigenic E. coli (ETEC) causes diarrheal disease in neonatal and weanling piglets, calves, lambs, dogs, and horses
- Most common E. coli strain in farm animals (enteric colibacillosis)
Pathogenesis of ETEC
- Entrance via oral route
- Colonize in small intestine once sufficient number is reached
- Proliferation occurs rapidly
- Enterotoxins produced and stimulate water and electrolyte secretion into the intestinal lumen
- Excess fluid in small intestine and lack of absorption in large intestine → Diarrhea
Enteric Colibacillosis
- Severe, watery, non-bloody diarrhea
- Requires treatment and correction of electrolyte and fluid imbalances to avoid fatalities due to dehydration and metabolic acidosis
- Infection may progress so rapidly that death may occur before clinical signs of diarrhea develop
- Especially in pigs
- Rarely microscopic lesions
- In uncomplicated cases, bacteria will be observed histologically coating the villi of mid-distal portions of the small intestines
Enteropathogenic E. coli (EPEC)
- Causes diarrhea in all animal species and humans
- Reservoirs: healthy cattle, sheep, pigs, dogs, and cats
- Most affected species: rabbits
- Suckling rabbits: diarrhea at 3-12 days of age (mortality up to 100%)
- Weanling rabbits: diarrhea at 5-14 days after weaning (mortality 5-50%)
- Pigs and dogs are also affected
Pathogenesis of EPEC
- Bacterial colonization of small and large intestines by formation of attaching and effacing lesions
- Lesions develop in 3 stages:
- Initial adherence: interaction between adhesins and host epithelial cells
- Type III secretion system (T3SS): secretion of several proteins into the enterocyte
- Host cell undergoes substantial cytoskeletal rearrangement and forms cup-like pedestals
- Microvilli are effaced, and bacteria are intimately attached to the apical plasma membrane of host cells
- Loss of absorptive microvilli leads to diarrhea due to malabsorption
Microscopic Lesions
- Light to moderate inflammation of lamina propria
- Enterocyte desquamation and mild ulceration
- Light-moderate villous atrophy in small intestine
- Extensive multifocal bacterial colonization of surface epithelium
Shiga Toxin-producing E. coli (STEC) and Enterohemorrhagic E. coli (EHEC)
- Greater virulence due to ability to produce attaching and effacing lesions plus Shiga toxin
- STEC that produce intimin and other LEE products are called EHEC (enterohemorrhagic E. coli)
- Shiga toxin (Stx) is the critical virulence factor
EHEC Infections
- Can cause hemolytic uremic syndrome (HUS) in dogs, which occurs occasionally as a consequence to bloody diarrhea in young dogs
- Bloody diarrhea is followed by thrombocytopenia, hemolytic anemia, and acute anuric renal failure
- Renal proximal tubular necrosis, hemorrhages, glomerular lesions, fibrin thrombi, and fibrinoid necrosis of blood vessels
Edema Disease in Pigs
- Caused by STEC
- Affected pigs become depressed, develop swelling of eyelids and forehead, peculiar squealing due to laryngeal edema, incoordination, and respiratory distress
- Some pigs may die before presentation of clinical signs
- Form of shiga toxemia that results in severe edema in specific sites in pigs where the toxin has been absorbed
- Causative strains: certain serotypes expressing α-hemolysin, F18ab fimbria
Gross Lesions in Edema Disease
- Subcutaneous tissues of eyelids and forehead
- Greater curvature of the stomach
- Cerebellum (infarction of brain and brainstem)
- Mesenteric lymph nodes
- Colonic mesentery
Predisposing Factors for Edema Disease
- Intestinal colonization aided by environmental and host factors
- Weaning: intestinal epithelial cells undergo changes, receptors for F18 fimbriae (found in STECs) are expressed
- High protein diets: optimal STEC proliferation environment
- Fastest growing pigs in a litter are most susceptible
ExPEC (Extraintestinal Pathogenic Strains)
- Found in normal intestinal microbiota
- Possess multiple virulence factors, including:
- Siderophores
- Capsule
- 𝛼-hemolysin
- Commonly cause infections in:
- Urinary tract
- Umbilicus
- Lungs
- Blood
- Wounds
- Strains are increasingly resistant to antimicrobials
- Includes E. coli, which is implicated in various infections, such as septicemia, urogenital infections, respiratory infections, and mammary gland infections
Pathogenesis
- Insufficient passive immunity leaves animals susceptible
- Strains enter the body via conjunctival, umbilical, or intestinal tissues
- Adherence and self-induced uptake via endocytosis allow for infiltration of intestinal epithelial cells
- After traversing epithelial surface, expression of adhesins is repressed, reducing binding with host phagocytic immune cells
- Subsequent entry into lymphatics and bloodstream, where they proliferate, leading to endotoxemia
- Death of host if antibacterial therapy and immune system are unable to remove the organism
Septicemic E. coli (SEPEC)
- Causes septicemia in pigs, usually in neonates and less frequently in suckling animals
- Characterized by acute, generalized infection, sometimes with diarrhea at the terminal stage
- Signs of shock, often fatal within 3-8 hours, with a mortality rate of up to 100%
- Also occurs in ruminants, typically in the first few days of life in calves and within the first 2-3 weeks in lambs
- Histopathological changes include inflammatory changes in liver, spleen, joints, meninges, and hemorrhages on the pericardium, peritoneal surfaces, and adrenal cortices
Uropathogenic E. coli (UPEC)
- Frequently implicated in UTIs in dogs, cats, and humans
- Infections often manifest as:
- Cystitis
- Urethritis
- Pyelonephritis
- Prostatitis
- Rarely ascends to the kidneys
- Isolated from 58-88% of canine pyometra cases (accumulation of pus in the uterus)
- Bitches are most susceptible during early stages of metestrus when serum progesterone levels are high
- Cystic endometrial hyperplasia caused by high progesterone is a predisposing factor
- E. coli recovered from cases are usually hemolytic and have the same characteristics as UPEC
- Systemic effects are attributed to absorbed E. coli lipopolysaccharide (LPS)
- Renal damage and dysfunction have been documented
Pathogenesis of UPEC
- UPEC from feces colonizes the periurethral area and migrates up the urethra
- Adheres to bladder epithelial cells, triggering a strong neutrophil response
- Damage to bladder epithelium leads to systemic effects
Avian Pathogenic E. coli (APEC)
- Invasive extraintestinal strains of E. coli that are usually specific serotypes
- Disease-causing in fowl
- Colibacillosis has various clinical forms depending on the age of the host and mode of infection
- Egg infections occur when bacteria penetrate the egg shell and infect the yolk sac, leading to embryo death or death within 3 weeks of hatching
- Respiratory and septicemic disease can be rapidly fatal or chronic, with clinical signs including debilitation, diarrhea, and respiratory distress
- Common presentations include air sacculitis and pneumonia
Mammary Pathogenic E. coli (MPEC)
- E. coli mastitis can develop in any host species, but most commonly in dairy cattle two weeks post-parturition
- Environmental mastitis pathogens
- Host factors impact the nature of developed mastitis, including:
- Nutritional status
- Immune status
- Genetic makeup
- Parity
- Lactation stage
- Pathogenesis involves:
- E. coli from the environment contaminating the teat orifice
- Bacteria ascending into the teat canal to the gland lumen
- Dry period: robust immune response often leads to elimination of the organism with little to no disease
- Periparturient period: cows are immunosuppressed, with low levels of lactoferrin, delayed PMN leukocyte response, and LPS-induced local inflammatory response and toxemia
- Mastitis presentation
Serotyping of E. coli
- Serotyping is used to differentiate between pathogenic and non-pathogenic E. coli strains and for epidemiological investigations.
- It is based on the presence of O or H antigens in the lipopolysaccharide layer and flagellar antigens.
- Cells may also express a Capsular (K antigen), flagella (H antigen), adhesins, and fimbrial antigens.
Virulence Factors of E. coli
- There are over 7 virulence factors associated with E. coli, including:
Adhesins
- Mediate attachment to host tissues.
- Can be assembled into organelles such as pili and fimbriae or consist of a single outer membrane protein.
- Types of adhesins include:
- F1: most E. coli produce type Fimbriae 1 (F1), plays a role in UTIs by binding to uroplakin and uroepithelium.
- F4, F5, F6, F11, F17, F18, F41, and F165: associated with E. coli that cause colibacillosis in animals.
Toxins
- Some pathogenic strains produce one or more enterotoxins, which are protein exotoxins encoded by genes on transmissible plasmids.
E. coli Enterotoxins (ETEC)
- Cause disturbances in intestinal fluid metabolism, but do not cause morphological or pathological lesions in the mucosa.
Heat-Stable Toxins
- Low molecular weight, poorly antigenic, and inactivated at 100°C after 15 minutes.
- Include:
- STa (ST1): causes release of Cl- and HCO3- into the intestinal lumen, inhibits Na+ reabsorption, and triggers fluid secretion by enterocytes.
- STb (T2): opens enterocyte calcium channels, triggers fluid secretion, and increases permeability of intestinal epithelium.
- EAST1: same mechanism of action as STa, but does not induce diarrhea alone.
Heat-Labile Toxins
- Produced and secreted in the small intestine only, increase intestinal epithelium permeability, and have immunomodulatory effects.
- Include:
- LT1 and LT2: cause permanent activation of adenylyl cyclase, increased secretion of Cl- and HCO3- into the intestinal lumen, and decreased reabsorption of Na+.
Shiga Toxins
- Also known as verotoxins, belong to a large family of ribosome-inactivating toxins, and are associated with STEC and EHEC groups.
- Include:
- Stx 1 and Stx 2: inhibit protein synthesis, induce host cell apoptosis signaling pathways, and cause vascular damage.
Hemolysins
- Pore-forming protein toxins that damage RBCs to obtain iron and impair leukocyte functions.
- Include:
- α-hemolysin, Enterohemolysin (EHEC toxin), Cytolysin A.
Cyclomodulins
- Family of bacterial toxins and effector proteins that interfere with the eukaryotic cell cycle.
- Include:
- CNF: stimulates cellular proliferation.
- CDT: inhibits cell cycle.
- Cif: inhibits cell cycle.
- Colibactin: causes cell death or impaired cell function by interfering with the cell cycle.
Serotyping of E. coli
- Serotyping is used to differentiate between pathogenic and non-pathogenic E. coli strains and for epidemiological investigations.
- It is based on the presence of O or H antigens in the lipopolysaccharide layer and flagellar antigens.
- Cells may also express a Capsular (K antigen), flagella (H antigen), adhesins, and fimbrial antigens.
Virulence Factors of E. coli
- There are over 7 virulence factors associated with E. coli, including:
Adhesins
- Mediate attachment to host tissues.
- Can be assembled into organelles such as pili and fimbriae or consist of a single outer membrane protein.
- Types of adhesins include:
- F1: most E. coli produce type Fimbriae 1 (F1), plays a role in UTIs by binding to uroplakin and uroepithelium.
- F4, F5, F6, F11, F17, F18, F41, and F165: associated with E. coli that cause colibacillosis in animals.
Toxins
- Some pathogenic strains produce one or more enterotoxins, which are protein exotoxins encoded by genes on transmissible plasmids.
E. coli Enterotoxins (ETEC)
- Cause disturbances in intestinal fluid metabolism, but do not cause morphological or pathological lesions in the mucosa.
Heat-Stable Toxins
- Low molecular weight, poorly antigenic, and inactivated at 100°C after 15 minutes.
- Include:
- STa (ST1): causes release of Cl- and HCO3- into the intestinal lumen, inhibits Na+ reabsorption, and triggers fluid secretion by enterocytes.
- STb (T2): opens enterocyte calcium channels, triggers fluid secretion, and increases permeability of intestinal epithelium.
- EAST1: same mechanism of action as STa, but does not induce diarrhea alone.
Heat-Labile Toxins
- Produced and secreted in the small intestine only, increase intestinal epithelium permeability, and have immunomodulatory effects.
- Include:
- LT1 and LT2: cause permanent activation of adenylyl cyclase, increased secretion of Cl- and HCO3- into the intestinal lumen, and decreased reabsorption of Na+.
Shiga Toxins
- Also known as verotoxins, belong to a large family of ribosome-inactivating toxins, and are associated with STEC and EHEC groups.
- Include:
- Stx 1 and Stx 2: inhibit protein synthesis, induce host cell apoptosis signaling pathways, and cause vascular damage.
Hemolysins
- Pore-forming protein toxins that damage RBCs to obtain iron and impair leukocyte functions.
- Include:
- α-hemolysin, Enterohemolysin (EHEC toxin), Cytolysin A.
Cyclomodulins
- Family of bacterial toxins and effector proteins that interfere with the eukaryotic cell cycle.
- Include:
- CNF: stimulates cellular proliferation.
- CDT: inhibits cell cycle.
- Cif: inhibits cell cycle.
- Colibactin: causes cell death or impaired cell function by interfering with the cell cycle.
Predisposing Factors to Infection
- Insufficient passive immunity from colostrum in neonates can lead to infection
- Factors that contribute to infection include:
- Quantity or quality of colostrum
- Age of neonates (under 1 week)
- Normal intestinal flora not fully established
- Naive immune system
- Presence of receptors for specific adhesins
- Intensive husbandry practices with rapid spread of E. coli strains
- Poor hygiene
- Stress (environmental changes, weaning, rapid diet change, etc.)
Control & Prevention
- Enterobacteriaceae family is susceptible to killing via:
- Sunlight
- Drying
- Pasteurization
- Common disinfectants (chlorine, phenol, and quaternary ammonium-based compounds)
- Bacteria can survive for weeks to months in:
- Moist, shaded environments
- Pastures
- Manure
- Litter
- Bedding
- Sound husbandry practices are key in prevention and control of E. coli related infections
- Commercially produced preparations containing monoclonal antibodies to ETEC adhesins can be given to neonatal animals to reduce severity and mortality
Genus Salmonella
- Gram-negative bacilli belonging to the family Enterobacteriaceae
- Motile, non-spore forming, and facultatively anaerobic
- Three species: S. subterranea, S. bongori, and S. enterica
- S. enterica is divided into six subspecies, with S. enterica subsp. enterica being the most important
- S. enterica subsp. enterica includes over 2600 serotypes/serovars
- Natural habitat is the intestinal tract of warm-blooded and cold-blooded animals
- Salmonellae can survive for nine months or more in the environment in sites such as:
- Moist soil
- Water
- Fecal particles
- Animal feed
- Foods
Epidemiology of Salmonellosis
- Some serotypes are relatively host-specific, while others affect a wide host range
- Clinical outbreaks are correlated with:
- Depressed immune system
- Newborn animals
- Stressed adult animals
- Parturient cows
- Equine surgical patients
- Swine with systemic viral disease
- Risk increases if intestinal microbiota is disrupted (e.g., from stress or use of antibiotics)
Pathogenesis of Salmonellosis
- Transmission occurs through the fecal-oral route, often through ingestion of contaminated food and water
- Outcome of the interaction between the host and Salmonella depends on:
- Host factors (state of colonization resistance, immune status, age, concurrent disease)
- Infectious dose
- Serotype of Salmonella
- Adhesion to target cells occurs in the distal small intestine and upper large bowel
- Salmonellae are internalized, leading to apoptosis of target cells, and inflammatory response
- Diarrhea is thought to result from prostaglandin synthesis and activation of different signaling pathways
Salmonellosis: Clinical Signs and Pathologic Changes
- Clinical signs include:
- Depression
- Fever
- Diarrhea
- Tenesmus
- Mortality may reach 100%
- Pathologic changes include:
- Fibrinosuppurative, necrotizing, and hemorrhagic inflammation of the distal small intestine and large bowel
- Multifocal necrotizing hepatitis
- Fibrinoid changes in blood vessels, vasculitis, thromboembolism, hemorrhages, and infarcts in the septicemic form
Salmonellosis in Ruminants and Other Animals
- Affects young and adult animals, causing enteritis, enterocolitis, or septicemia
- Abortions may follow septicemia
- S. Dublin, S. Typhimurium, and S. Newport are commonly isolated serotypes from cattle
- S. Typhimurium is the main serotype affecting sheep
- In pigs, the disease can present as acute, fulminating septicemia or chronic debilitating intestinal disease
- In horses, diarrhea, but occasionally septicemia, can occur
- In dogs and cats, salmonellosis is uncommon and usually associated with a common source
Salmonellosis in Poultry
- Salmonellosis in poultry is a major threat to bird health, welfare, and the local economy, caused by non-motile strains S.Gallinarum and S.Pullorum.
- Other serovars, such as S.Enteritidis and S.Typhimurium, can cause clinical salmonellosis in very young birds, especially in high ambient temperatures and low biosecurity conditions.
- Serovars like Heidelberg, Seftenberg, Infantis, Motevideo, and Menston are less virulent in chicks but can colonize the intestine and cause human food poisoning.
Sources of Infections
- Poultry themselves can be a source of infection.
- Feed can also be a source of infection.
- The environment can be a source of infection.
- Vertical transmission occurs in the case of S.Gallinarum and S.Pullorum.
Pullorum Disease
- Pullorum disease is caused by S.Pullorum.
- It infects the ova of turkeys and chickens, and the embryos are already infected when the eggs are hatched.
- Environmental contamination occurs as a result.
- Mortality is highest in the 2nd-3rd weeks of life and is due to septicemia.
- Surviving birds become carriers and shed the organism in feces only periodically.
- The organism circulates in the spleen despite high numbers of antibodies, and it is not eliminated for months.
- When hens become sexually active, the organism multiplies and spreads to other tissues like the reproductive tract and ovaries, where eggs become infected.
Fowl Typhoid
- Fowl typhoid is caused by S.Gallinarum.
- It is either an acute septicemic or chronic disease of domesticated adult birds, mainly chickens.
- Horizontal transmission occurs through the fecal-oral route.
- The organism colonizes the gut poorly but multiplies in monocytes and macrophage cell lineage in the spleen and liver.
- This leads to ensuing bacteremia and localizes in the wall, causing sterile necrosis in the myocardium.
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Description
Bacteriology exam prep Clostridium, Enterobacteriaceae ,Escherichia, Salmonella