119 Questions
What is the function of the capsule produced by Staph. Aureus?
To mask the recognition of antibodies by the host immune system
What is the primary role of the protein A expressed on the surface of Staph. Aureus?
To bind to immunoglobulins and prevent opsonization
Which type of toxin produced by Staph. Aureus is responsible for causing food poisoning?
Enterotoxins
What is the primary function of the enzyme coagulase produced by Staph. Aureus?
To convert fibrinogen into fibrin, creating clots
What is the primary role of the enzyme hyaluronidase produced by Staph. Aureus?
To break down hyaluronic acids in host connective tissues
What is the typical outcome of Streptococcus equi infection in horses?
Uncomplicated recovery
Which of the following is a common site of Streptococcus canis infection in cats?
Lymph nodes
What is the primary mode of transmission of Streptococcus suis in pigs?
Respiratory and oral routes
What is the optimal temperature to kill Streptococcus suis?
55-60°C for 30 minutes
Which of the following antibiotics is effective against Streptococcus suis?
None of the above
Which type of anaerobic environment do members of the genus Staphylococcus typically prefer?
Facultative anaerobes
What differentiates coagulase tests among species of Staphylococcus?
Strain-dependent reactions
Which of the following features is associated with the virulence of Staphylococcus aureus?
Accessory genes
Where does Staphylococcus typically colonize in mammals and birds?
Various sites including nasal cavity, skin, and naso-pharynx
Which characteristic distinguishes Coagulase +’ve staphylococcus species from Coagulase -’ve species?
Primary pathogenicity
Which host proteins do MSCRAMM proteins primarily bind to?
Collagen and Fibrinogen
What is a significant economic consequence of staphylococcal mastitis in the dairy industry?
Reduced yield
Which is a common predisposing factor for staphylococcal infections?
Malnutrition
Which of the following conditions is caused by Staphylococcus pseudintermedius in dogs?
Both B and C
What is a typical form of Staphylococcus hyicus infection in pigs?
Exudative epidermitis
Which disease is most clinically relevant in canine pyoderma caused by pseudintermedius?
Superficial pyoderma
What is required for the pathogenesis of pseudintermedius infections?
Genetic traits shared among all strains
What feature characterizes β(beta) haemolytic streptococcal colonies?
Lysis of erythrocytes producing a zone of hemolysis
Which streptococcal protein specifically binds to fibrinogen and confers antiphagocytic properties?
M Protein
Which bacteria predominantly forms pairs when smeared from colonies?
Streptococcus pneumoniae
Which component of the Streptococcus species is poorly antigenic and does not readily bind to complement components?
Hyaluronic acid
Which Streptococcal surface protein has an analogous counterpart known as SzP in Streptococcus equi zooepidemicus?
M Protein
Which of the following factors does not contribute to staphylococci's evasion of the immune system?
Latex agglutination
Which enzyme produced by Streptococci converts plasminogen to plasmin and aids in fibrin clot degradation?
Streptokinase
What is the role of the Streptococcal biofilm regulatory protein A, specifically in Streptococcus agalactiae?
Promotes establishment of infection and improves antibiotic resistance
Which Enterococcus species is most commonly associated with infections in mammals and birds?
Enterococcus faecalis
What role does the aggregation substance play in Enterococcus pathogenicity?
Promotes adherence to epithelial surfaces and other enterococci
What distinguishes enterococci in terms of antibiotic resistance?
Intrinsic resistance to beta lactam antibiotics, aminoglycosides, clindamycin, fluoroquinolones, and trimethoprim-sulfonamides
Which virulence factor is responsible for cytolysin production in Enterococcus species?
Cell wall peptidoglycan
What is the role of pili in Enterococcus species?
Promotes adhesion to multiple types of cells and biofilm formation
What is the primary transmission route for causing environmental contamination of mastitis pathogens among cattle?
Fecal shedding and milk leakage from infected udders
Which factor does NOT predispose cattle to mastitis?
Use of dry cow antibiotic therapy
Which subspecies of Streptococcus is associated with insect bites leading to mastitis in cattle?
Streptococcus dysgalactiae
What is a common factor that increases the risk of older cattle contracting mastitis caused by Streptococcus uberis?
Heavy environmental soiling with fecal matter
How long can Streptococcus equi equi persist in contaminated water or feed?
Short or longer periods, depending on conditions
What is a primary function of the polysaccharide microcapsule produced by Staph. Aureus?
Masks recognition of antibodies for the cell wall, avoiding complement activation
What is a characteristic of biofilm formation in Staph. Aureus?
It is facilitated by surface proteins
What is the primary function of Protein A in Staph. Aureus?
Binds to immunoglobulins to prevent recognition, opsonization, and innate immune system avoidance
What is a role of leukocidins in Staph. Aureus?
Killing phagocytes and avoiding the host innate immune system
What is the primary role of α(alpha) haemolysin in Staph. Aureus?
Creating pores in cell membranes, leading to cell lysis
What is the function of clumping factor (bound coagulase) in Staph. Aureus?
Not mentioned in the text
What is a characteristic of the biofilm matrix in Staph. Aureus?
It is composed of polysaccharides
What is the role of δ(delta) haemolysin in Staph. Aureus?
Cytotoxic to neutrophils
What is the primary mechanism of Streptococcus equi infection in horses?
Formation of abscesses with long chains of extracellular Streptococcus
What is the typical incubation period for Streptococcus equi infection in horses?
3-14 days
What is the primary site of Streptococcus canis infection in dogs?
Oropharynx
What is the primary mode of transmission for Streptococcus equi in horses?
Contaminated water or feed
What is the characteristic of Streptococcus equi zooepidemicus that makes it a significant pathogen?
Its wide host range and opportunistic nature
What is the typical duration of nasal shedding of Streptococcus equi in horses?
4-14 days
What is the primary site of Streptococcus equi infection in horses that can lead to metastasis?
Guttural pouch
What is the characteristic of Streptococcus canis that makes it a significant pathogen?
Its wide host range and opportunistic nature
What is a characteristic evolution of lesions in pigs infected with Staphylococcus hyicus?
Progression to yellowish-brown crusts in specific areas
What is a major predisposing factor for greasy pig disease in sows?
Agalactia
What can happen 24 hours to 10 days after crusting in greasy pig disease?
Fatal results caused by dehydration
What is the morbidity rate typically seen in exudative epidermitis in pigs?
20%
Which anatomical sites are commonly isolated for Staphylococcus pseudintermedius in dogs?
Mouth and perineum
What type of bacteria is Staphylococcus pseudintermedius considered among dogs?
Normal part of microbiota
What proportion of pigs affected by greasy pig disease can reach up to 90%?
Mortality rates
Which condition in pigs can be exacerbated by inappropriate housing materials?
Exudative epidermitis
Which genetic trait is essential for the pathogenicity of pseudintermedius infections in dogs?
Biofilm formation ability
What underlying condition DOES NOT initiate pseudintermedius-associated canine pyoderma?
Immunodeficiency
Which specific antimicrobial resistance gene is responsible for rendering pseudintermedius methicillin-resistant?
mecA
Which strain type frequently displays resistance to multiple antimicrobial agents in pseudintermedius infections?
Methicillin-resistant strains
What type of pyoderma is most clinically relevant in dogs?
Superficial pyoderma
Which breed is NOT listed as being predisposed to pseudintermedius infections?
Labrador Retriever
Which condition is NOT caused by pseudintermedius in dogs?
Pneumonia
Which evasion factor produced by pseudintermedius inhibits the function of immune cells in dogs?
Leukocidins
Which type of staphylococcal species is generally related to veterinary diseases?
Coagulase -’ve (CoNS)
What is a primary consequence of chronic intramammary Staphylococcus aureus infections in dairy cattle?
Chronic, low-grade or subclinical infections
Which livestock is most commonly affected by botryomycosis due to Staphylococcus aureus?
Horses
Which animal is primarily affected by 'greasy pig disease' caused by Staphylococcus hyicus?
Pigs
Which diagnostic test is used to detect subclinical mastitis involving an elevated somatic cell count?
California mastitis test
In the pathogenesis of staphylococcal mastitis, what is formed after the bacteria rapidly replicate?
Biofilm
What symptom is associated with severe and peracute clinical mastitis caused by Staphylococcus aureus?
Tachycardia
Which of the following is the natural site of Staphylococcus hyicus in pigs where it can be transmitted to piglets?
Vaginal mucosa
What is the primary site of Streptococcus pyogenes infection in cows?
Mammary glands
What is the typical manifestation of Streptococcus agalactiae infection in dogs?
Neonatal septicemia
Which species of Streptococcus is commonly associated with strangles in horses?
S.equi s.equi
What is the primary reason for examining Streptococcus samples immediately?
To prevent desiccation
What is the primary difference between Streptococcus dysgalactiae and Streptococcus equisimilis?
Disease manifestations
What is the primary purpose of using transport medium for Streptococcus samples?
To preserve the sample
Which of the following is NOT a common site of Streptococcus canis infection in dogs?
Lungs
What is the primary difference between Streptococcus pneumoniae and Streptococcus suis?
Host range
What is the characteristic arrangement of staphylococci in stained smears?
Pairs, tetrads, or irregular grape-like clusters
What is the optimal temperature range for the growth of staphylococci?
30-37°C
What is the characteristic of the colony morphology of staphylococci on NA?
Round, pigmented, and butyrous
What is the purpose of the catalase test in the identification of staphylococci?
To differentiate staphylococci from streptococci
What is the characteristic haemolysis produced by coagulase-positive staphylococci on BA?
β-haemolysis
What is the purpose of the modified oxidase test in the identification of staphylococci?
To distinguish between staphylococci and micrococci
What is the characteristic of staphylococci in terms of oxygen requirements?
Facultative anaerobes
What is the characteristic of staphylococci in terms of salt tolerance?
Tolerant to high salt concentrations
Which group of streptococci is characterized by the production of CAMP factor?
Group B streptococci
What is the primary method of identification for precise species identification of streptococci?
MALDI TOF MS or PCR
Which Enterococcus species is associated with opportunistic infections in poultry, including urinary tract infections and hepatic abscesses?
E. faecium
What is the primary purpose of using a Gram stain and catalase test in the identification of Enterococcus?
To identify the genus Enterococcus
Which medium is used to selectively isolate Enterococcus from a mixed culture?
SBA or ESA
What is the primary characteristic that distinguishes Enterococcus from group D streptococci?
Reclassification as a separate genus
Which of the following is NOT a common site of Enterococcus infection in animals?
Respiratory tract
What is the primary role of Lancefield grouping system in the identification of streptococci?
To identify specific streptococcal species
Which medium is used as a selective-differential media for inoculation of staphylococcal samples?
Mannitol Salt Agar (MSA)
Staphylococcus felis commonly causes which condition in cats?
Otitis externa
Which species of Staphylococcus is most likely to cause pyogenic wound infections primarily in dogs and cats?
Staphylococcus pseudintermedius
What type of sample is usually sent to the laboratory for examining clinical and subclinical mastitis?
Milk
Which test is NOT commonly used to identify the genus and/or species of staphylococcal infections after obtaining a pure culture?
Methylene blue reduction test
Which Staphylococcus species is associated with exudative epidermitis in piglets and polyarthritis in birds?
Staphylococcus hyicus
Which condition is least associated with Staphylococcus aureus in various animal species?
Exudative epidermitis
Which type of medium is Columbia Naladixic Acid agar (CNA) classified as?
Selective medium
Which agar is used as a selective-differential medium for isolating Streptococcus species?
Chromogenic Streptococcus Agar (CSA)
What is the morphology of Streptococcus colonies after 24 hours of incubation?
Round, non-pigmented, smooth, convex, shiny colonies with a diameter of 0.5-1 mm
Which condition is optimal for the growth of Streptococcus species during cultivation?
Aerobically with reduced O2 and 5% CO2
What method can be used to differentiate Streptococcus from other gram-positive cocci?
Catalase test
What is the significance of colony morphology on selective-differential media?
Identifying the species
Which testing method is used after obtaining a pure culture to identify the genus of Streptococcus?
Catalase test
Which of the following describes the arrangement of Streptococcus agalactiae in stained smears?
Long chains with up to 40 cocci
Study Notes
Genus Staphylococcus
- Over 70 species and subspecies
- Wide host range, with most species being commensal and only some causing opportunistic infections
- Found naturally worldwide in mammals and birds
- Colonizes in nasal cavity, naso-pharynx, skin, mucous membranes, and gastrointestinal tract (transiently)
Characteristics
- Gram-positive cocci, often in grape-like clusters
- Facultative anaerobes, with one anaerobic subspecies and one microaerophilic species
- Catalase-positive
- Coagulase tests are variable by species and are used to differentiate between Staphylococcus species
Virulence Factors
- Staphylococcus aureus: opportunistic pathogen with a broad range of virulence factors
- Cell wall-associated structures: MSCRAMM (Microbial Surface Components Recognizing Adhesive Matrix Molecules) for cell surface attachment, colonization, and invasion
- Capsule: most strains do not produce large capsules, but produce a polysaccharide microcapsule
- Biofilm: plays a role in bacterial resistance to antibiotic treatments
- Protein A: binds to immunoglobulins to prevent recognition and opsonization
- Exotoxins: haemolysins, leukocidins, and enterotoxins
- Enzymes: facilitate dissemination and enhance toxicity
Infections
- Comparatively stable in the environment, allowing for indirect transmission
- Pyogenic bacteria, often causing suppurative lesions
- Coagulase-positive (CoPS) are primary pathogenic Staphylococcus species, while coagulase-negative (CoNS) are important in veterinary-related diseases
- Predisposing factors: injury to the skin, respiratory infections, immunosuppression, malnutrition, disruption of normal flora, and large exposure dose
Staphylococcal Mastitis
- Mammary gland inflammation, causing significant economic loss in the dairy industry
- Staphylococcus aureus is the primary pathogen for mastitis in dairy cattle
- Can be carried on teat skin, nasal cavity, and rectum
- Transmission: primarily from udder to udder during milking
- Pathogenesis: bacteria colonize the teat, leading to rapid replication, biofilm formation, and degradation of epithelial cells
Other Diseases
- Skin infections, folliculitis, and impetigo in cattle
- Mastitis in small ruminants, poultry, and rabbits
- Botryomycosis in horses
- Staphylococcus hyicus: primary cause of 'greasy pig disease' (exudative epidermitis)
- Staphylococcus pseudintermedius: normal part of canine microbiota, causing canine pyoderma, otitis externa, and other infections
Antimicrobial Resistance
- Significant problem with Staphylococcus aureus and pseudintermedius
- Methicillin-resistant strains are frequently resistant to other antimicrobial agents
- Methicillin-resistant Staphylococcus aureus (MRSA) has been isolated from various animal species
Control and Prevention
- Focus on prevention, as Staphylococcus can survive and remain virulent for weeks
- Susceptible to disinfectants and antiseptics
- Killed rapidly at high temperatures and in certain pH environments
Genus Streptococcus
- 103 recognized species, with 9 subspecies
- Worldwide distribution, with most species being of interest in veterinary medicine
- Opportunistic pathogens and non-pathogenic commensals in humans and animals
- Transmission: inhalation, ingestion, sexual activity, congenital, and indirect via hands and fomites
Characteristics
- Gram-positive, cocci, with small size (less than 2 μm)
- Non-motile, catalase-negative, and facultative anaerobes
- Require addition of blood or serum to culture media for growth in vitro
- Susceptible to desiccation
Classification
- Based on haemolysis (α, β, and γ)
- Based on cell wall carbohydrates (Lancefield Group A-H and K-V)
Virulence Factors
- Adhesins: MSCRAMM, M protein, FbsA, FOG, and SzP
- Capsule: some species form capsules, which protect from phagocytosis
- Streptococcal pyrogenic toxin superantigens (SPEs): pyrogenic, fever-inducing, and causing immune malfunction
- Streptolysins (haemolysins): Streptolysin O and S
- Streptokinase: enzyme that activates conversion of plasminogen to plasmin
Characteristics of Streptococcal Infections
- Most disease-causing streptococci are commensal and only cause disease when stress or internal conditions allow
- Pyogenic infections, often with febrile symptoms
- Locally affected areas exhibit pus formation, and if drainage is prevented, abscess formation
- Hematogenous spread of primary infection may result in septicemia
Pathogenic Species
- Streptococcus agalactiae: invasive disease in camels, and occasionally in dogs, fish, cats, and hamsters
- Streptococcus dysgalactiae: opportunistic pathogen causing diseases in various species
- Streptococcus uberis: opportunistic pathogen causing diseases in various species
- Streptococcus pneumoniae: causative agent of pneumonia and other diseases
- Streptococcus suis: opportunistic pathogen causing diseases in pigs### Subspecies of Streptococcus
- Dysgalactiae: Lancefield group C, alpha-haemolytic, causes acute and subclinical mastitis in cattle, associated with insect bites or teat/udder epithelial injury.
- Equisimilis: Lancefield groups A, C, G, or L, beta-haemolytic, disease-causing in various species, including humans.
Streptococcus uberis
- No Lancefield group, commensal in cattle, found in tonsils, intestines, mucous membranes, and skin.
- Causes 20-30% of clinical mastitis cases, often opportunistic invasions of the mammary gland.
- Environmental mastitis pathogen, more common in older cattle, associated with heavy environmental soiling with fecal matter.
Streptococcus equi equi
- Lancefield group C, obligate parasite/primary pathogen, causes Strangles.
- Highly contagious nasopharyngeal infection, also impacting associate lymph nodes.
- Transmission sources: nasal discharge, pus from an abscess, contaminated water, feed, or fomites.
- Animals can be carriers for short or longer periods.
Pathogenesis of Streptococcus equi equi
- Enters via mouth or nose, attaches to cells in the crypts of oral tonsils and cilia of nasopharyngeal tonsils.
- Clumps of Streptococcus equi visible in lamina propria after 48 hours, leading to abscess formation.
- Potential to metastasize and form abscesses in other organs (brain, thoracoabdominal lymph nodes).
Clinical Signs and Prognosis of Streptococcus equi equi
- Incubation period: 3-14 days, fever, lassitude, nasal discharge, cough, difficulty swallowing, swelling of mandibular lymph nodes.
- Potential metastasis, nasal shedding begins at 4-14 days and ceases between 3-6 weeks post-acute infection phase.
- Most cases are uneventful and quick, but infection may persist in guttural pouch after clinical recovery.
Streptococcus equi zooepidemicus
- Lancefield group C, mucosal commensal with wide range of opportunistic diseases, especially in stressed hosts.
- Most frequently isolated pathogen from opportunistic infections in horses.
- Can cause peracute and fatal hemorrhagic pneumonia in animals, shelters, kennels, and laboratory colonies.
Streptococcus canis
- Lancefield group G, sporadic, opportunistic purulent infections in multiple sites.
- Infects dogs, cats, mink, possums, aquatic mammals, and humans.
- Found in anal mucosa, oropharynx, urogenital tract, and parts of canine and feline skin.
Streptococcus canis in Cats
- Commonly isolated from skin and lymph node abscesses in cats.
- Causes mastitis, conjunctivitis, metritis, and septicemia in kittens.
- Local abscess forms, leading to bacterial thrombi in various body sites, death within a week.
- Older queens may pass immunity to kittens, making them more resistant.
Streptococcus suis
- Lancefield groups D, R, S, and T, wide range of clinical syndromes, serious zoonotic pathogen in humans.
- Pigs are primary carriers, transmission by respiratory and oral routes.
- Causes septicemia, meningitis, endocarditis, bronchopneumonia, and polyarthritis in pigs.
Control and Prevention of Streptococcus suis
- Survives in dry pus for weeks, killed at 55-60°C in 30 minutes.
- Inhibited by 6.5% NaCl, 40% bile, low and high temperatures.
- Resistant to antibiotics, including tetracycline, benzopenicillin, clindamycin, tilmicosin, norfloxacin, and erythromycin.
Genus Enterococcus
- Possess phenotypic traits that set them apart, previously classified as group D streptococci.
- 60 species, most found in intestinal tracts of mammals and birds, mainly opportunistic.
- Infect compromised sites, virulence factors include multiple MSCRAMMs, aggregation substance, pili, capsule, cytolysin, and gelatinase.
Transmission and Pathogenesis of Enterococcus
- Endogenous enterococci contaminate and infect compromised sites.
- Cell wall peptidoglycan and lipoteichoic acids initiate inflammatory response, while capsule, cytolysin, and other virulence factors promote further inflammatory response.
Disease-causing Enterococcus Species
- Intestinal diseases (diarrhea in young animals), other infections, including otitis externa, lower UTIs, and bacterial endocarditis.
- Enterococcus durans, Enterococcus faecalis (~95%), Enterococcus hirae, Enterococcus faecium (~5%), and Enterococcus villorum.
Resistance of Enterococcus
- Grows in 6.5% NaCl, 40% bile, high and low temperatures, intrinsically resistant to beta-lactam antibiotics, aminoglycosides, clindamycin, fluoroquinolones, and trimethoprim-sulfonamides.
- Vancomycin-resistant strains of enterococci are a serious health problem in human medicine.
Learn about the characteristics and habitats of Staphylococcus genus, including its species, host range, and growth conditions. Get familiar with the different species, their occurrence, and colonized areas.
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