VPBacteriology_Bacteriology_Pathogenic_Bacteria_DrGutierrez_Spring2024.pdf

VPRP096 Introduction to Microbiology: Pathogenic bacteria I & II Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Defining pathogenic bacteria infectious agent, a microorganism that can cause disease upon colonization of the host. PATHOG...

VPRP096 Introduction to Microbiology: Pathogenic bacteria I & II Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Defining pathogenic bacteria infectious agent, a microorganism that can cause disease upon colonization of the host. PATHOGEN They harbor the required virulence genes for infection (e.g. adherence, invasion and evasion of immune system and/or toxins) OBLIGATE PATHOGEN FACULTATIVE PATHOGEN OPPORTUNISTIC PATHOGEN microorganism which must infect a host and cause disease in order to multiply and be transmitted from one host to another. microorganism which can infect and multiply in hosts but is also capable of multiplying in the environment. microorganism which does not ordinarily cause disease but under certain conditions (e.g. impaired host immunity) becomes pathogenic Defining Definingpathogenic pathogenic bacteria bacteria OBLIGATE INTRACELULAR ▪ Can only reproduce inside the infected host cell FACULTATIVE INTRACELULAR ▪ Can survive and multiply intra- and extracellularly (e.g. Mycobacterium, Salmonella) EXTRACELULAR (e.g. Rickettsia, Ehrlichia, Mycoplasma, Chlamydia) ▪ Can survive and multiply extracellularly in the periphery of host cells (e.g. Streptococc group A) Defining pathogenic bacteria Gram Staining Pink: Gram-Negative Purple: Gram-Positive Defining pathogenic bacteria Important pathogens (non-excl.) Extracellular & Facultative Obligate intracellular Rickettsia, Chlamydia, Ehrlichia, Mycoplasma Gram-positive Gram-negative Mycobacteria Spirochetes Borrelia Cocci Bacilli Staphylococci Streptococci Cocci & Bacilli Treponema coccobacilli Enterobacteriaceae Leptospira Haemophilus Enterococci Bordetella Aerobes Anaerobes Listeria Clostridia Bacillus Actinomycetes Corynebacterium Brucella Pasteurella Neisseria Pseudomonads Legionella Vibrio Campylobacter Helicobacter Gram-positive cocci Gram-positive bacteriacocci Gram-positive bacteria Staphylococcus ▪ Reservoir: on skin and mucus membranes of animals and humans ▪ → commensals! ▪ Upper respiratory tract (nose!) ▪ Lower urogenital tract ▪ Gastrointestinal tract ▪ Species of clinical importance ▪ S. aureus (humans & animals) ▪ S. pseudintermedius (dogs & cats) ▪ S. hyicus (pigs) ▪ Pyogenic infections: suppurative infections with pus-filled lesions (~abscess) S. aureus in plasma in the presence of extracellular fibrinogen binding protein (SEM) Gram-positive bacteria- cocci Staphylococcus pseudointermedius Pyoderma, Otitis Externa ▪ Host: dog, cat ▪ Pyoderma (local suppurative skin infections) ▪ Otitis externa (ear infections): main cause often parasites, food allergies, foreign bodies with staphylococci as secondary infections Gram-positive bacteria- cocci Bacterial pyoderma is usually Any skin disease that changes the normally dry, triggered by OVERGROWTH of desert-like environment to a more humid normal RESIDENT or transient environment can predispose the host to bacterial skin microbiota over-colonization. Gram-positive bacteria- cocci Staphylococcus Bovine staphylococcal mastitis ▪ S. aureus ▪ Host: Cattle, small ruminants ▪ Contagious mastitis ▪ Majority not cleared by immune system -> chronic, low-grade or subclinical -> production losses! ▪ Ranging from peracute gangrenous mastitis to chronic mastitis Gram-positive bacteria- cocci Streptococcus ▪ Reservoir: on mucus membranes of animals and humans → commensals!* ▪ Upper respiratory tract ▪ Lower urogenital tract ▪ Bacteria have capsule to evade phagocytosis ▪ Species of clinical importance ▪ S. pyogenes (humans) ▪ S. agalactiae (cattle) -> contagious mastitis (milk ducts) ▪ S. dysgalactiae (cattle) -> environmental mastitis (skin, buccal cavity) ▪ S. equi subsp. equi (horses) -> strangles ▪ Host-specific suppurative infections, local and systemic including septicemia, throat and adjacent lymph node infections Gram-positive bacteria Streptococcus Strangles = equine distemper ▪ S. equi subsp. equi, not a commensal ▪ Host: equines ▪ Highly contagious febrile disease involving the upper respiratory tract with abscessation of regional lymph nodes in equines → swollen lymph nodes can cause airway obstruction leading to death (~ strangles) ▪ Transmission: direct or indirect contact with purulent exudates ▪ Notifiable disease in many states of the US. Gram-positive bacteria- cocci Streptococcus Streptococcal mastitis ▪ Host: cattle, small ruminants ▪ S. agalactiae colonizes milk ducts -> persistent infection with intermittent bouts of acute mastitis ( ~ chronic mastitis) ▪ S. dysgalactiae colonizes buccal cavity, genitalia and skin of mammary gland -> acute mastitis Gram-positive rods/bacilli Gram-positive bacteria- bacilli Listeria monocytogenes ▪ Reservoir: Ubiquitous in the environment (herbage, sewage effluent, fresh water, feces from healthy animals) ▪ Psychrophilic -> growth in fridge! ▪ Facultative intracellular bacteria that can persist in macrophages ▪ Uses actin filaments to travel through cells ▪ Listeriosis with three clinical symptoms, rarely overlap ▪ Septicemia ▪ Abortion ▪ Encephalitis Gram-positive bacteria- bacilli Listeria monocytogenes Circling disease, silage disease, listeriosis ▪ Host: cattle, small ruminants ▪ Encephalitis is the most readily recognized form of listeriosis in ruminants ▪ Affecting all ages, both sexes ▪ Winter-spring disease of feedlot or housed ruminants: less acidic pH of spoiled silage enhances multiplication of L. monocytogenes Gram-positive bacteria- bacilli Listeria monocytogenes Circling disease, silage disease, listeriosis Gram-positive bacteria- bacilli Listeria monocytogenes Circulation of Listeria in environment When food bites back. How safe is your food?! Gram-positive bacteria- bacilli Erysipelothrix rhusiopathiae ▪ Reservoir: widespread in tonsils and intestines of many species ▪ Up to 50% of healthy pigs harbor E. rhusiopathiae in tonsillar tissues ▪ Susceptible animals: pigs 3 months to 1 year old (stress factors) ▪ Four syndromes ▪ Septicemia ▪ Arthritis ▪ Endocarditis ▪ Dermatopathy ▪ Diamond skin disease in swine or swine erysipelas Gram-positive bacteria- bacilli Corynebacterium pseudotuberculosis ▪ Reservoir: soil, mucus membranes → commensals ▪ Host: small ruminants ▪ Facultative intracellular pathogens that survive in macrophages ▪ Caseous lymphadenitis: abscessation and enlargement of superficial or internal lymph nodes in sheep and goats Gram-positive bacteria- bacilli Bacillus anthracis ▪ Aerobes or facultative anaerobes, obligate mammalian pathogen, endospore-forming ▪ Reservoir: ubiquitous in soil ▪ Anthrax: mostly restricted to cattle, source of infection is soil contaminated with spores Coat ▪ Virulence factors ▪ Bacillus anthracis capsule ▪ Tripartite anthrax toxin ▪ Protective Antigen: cell-binding factor ▪ Edema factor: disturbance of water homeostasis -> edema ▪ Lethal factor: cell death and hypoxia-induced tissue injury -> necrosis and hemorrhage Gram-positive bacteria- bacilli Bacillus anthracis Per acute septicemia in ruminants ▪ Rapidly fatal disease with respiratory distress and shock ▪ Bleeding from orifices ▪ Postmortem: dark unclotted blood incomplete rigor mortis, splenomegaly Gram-positive ANAEROBIC rods/bacilli Gram-positive bacteria- anaerobic bacilli Clostridium ▪ Obligate anaerobes and powerful toxin producers ▪ Endospore-forming ▪ Widespread in soil, gastro-intestinal tract of animals and humans and in feces Group Pathogenic effect Members Disease Neurotoxic clostridia Affect neuromuscular function without inducing observable tissue damage C. tetani C. botulinum Tetanus Botulism Histotoxic clostridia Localized lesions in muscle and liver, subsequently causing toxemia C. chauvoei Blackleg C. septicum Malignant edema C. novyi type A and B Black disease Enteropathogenic and enterotoxaemia-producing clostridia Infers with protein synthesis in cells C. perfringens type (A-E) C. difficile Enterotoxaemia Pseudomembranous colitis Gram-positive bacteria- anaerobic bacilli Clostridium Tetanus ▪ C. tetani ▪ Reservoir: soil, mammalian intestines ▪ Host: equines, humans ▪ Acute, potentially fatal intoxication with neurotoxic clostridia causing spastic paralysis (after growth of bacteria in contaminated wounds e.g.) ▪ Produces tetanospasmin, a potent neurotoxin and tetanolysin, a haemolysin destructing tissues Gram-positive bacteria- anaerobic bacilli Clostridium Botulism ▪ C. botulinum ▪ Reservoir: soil ▪ Serious, potentially fatal intoxication by ingestion of pre-formed neurotoxin (food intoxication) ▪ Causes flaccid paralysis ▪ Germination of endospores with growth of vegetative cells and toxin production in rotting carcasses, decaying vegetation and contaminated canned foods Gram-negative rods/bacilli Gram-negative bacteria - bacilli Enterobacterales Group of the Enterobacterales ▪ Reservoir: Present in water, soil and GI tract ▪ “Coliform bacteria” ▪ Important major pathogens ▪ Escherichia coli ▪ Salmonella serotypes ▪ Yersinia spp. ▪ Opportunistic pathogens ▪ Proteus spp. ▪ Klebsiella pneumoniae ▪ Enterobacter aerogenes Gram-negative bacteria - bacilli Escherichia coli ▪ Reservoir: commensal of the GI tract of many animals/humans ▪ Opportunistic infections in extra-intestinal locations e.g., mammary gland, urinary tract, sepsis Neonatal colisepticemia in calves/lambs/poultry ▪ Invasion of bloodstream ▪ Acute fatal disease with depression, weakness, tachycardia, hypothermia, diarrhea Gram-negative bacteria - bacilli Escherichia coli Edema disease in piglets ▪ Toxemia occurring 1 to 2 weeks after weaning in rapidly growing pigs ▪ Toxin produced and in blood, damage endothelial cells with perivascular edema Coliform mastitis ▪ Fecal contamination of the mammary gland is the source! ▪ Mammary secretions watery with white flecks Gram-negative bacteria - bacilli Salmonella ▪ Majority of veterinary important strains belong to S. enterica subsp. enterica ▪ Serotypes occur worldwide in many mammals, birds and reptiles and are excreted in feces ▪ > 2500 serotypes e.g. Typhimurium, Newport, Enteritidis, Dublin, … ▪ S. Enteritidis: infects ovaries of chicken and can be isolated from eggs ▪ S. Dublin in cattle: causes wide range of diseases including septicemia, abortion, osteomyelitis, subclinical fecal excretors (intermittently in feces) and latent carriers (Salmonella in gall bladder, no excretion) ▪ Enteritis, septicemia and abortion. ▪ Zoonotic serotypes! Gram-negative bacteria - bacilli Brucella ▪ Brucella spp. predilection for both female and male reproductive organs ▪ Reservoir: infected animals serve as reservoirs ▪ Bacteria survive in macrophages ▪ Important pathogens causing brucellosis ▪ B. abortus: abortion in cattle ▪ B. melitensis: abortion in sheep ▪ B. canis: abortion, epididymitis, sterility in dogs ▪ B. suis: abortion, orchitis, arthritis, infertility in pigs ▪ Zoonotic disease ▪ Direct contact with secretions or excretions of infected animals (skin, inhalation, ingestion) ▪ Raw milk and dairy products made with unpasteurized milk! Gram-negative bacteria - bacilli Brucella Brucella abortus life host cycle Gram-negative bacteria - bacilli Bordetella bronchiseptica Kennel cough in dogs = canine infectious tracheobronchitis ▪ Co-infection with canine Adenovirus ▪ Coughing, gagging, oculo-nasal discharge ▪ Intranasal vaccines induce local protective immunity Atrophic rhinitis in pig ▪ May facilitate colonization by toxigenic Pasteurella multocida -> severe atropic rhinitis and distortion of the snout Spirochetes Spirochetes Leptospira ▪ Gram-negative bacteria ▪ Spirochete = spiral motile bacteria with endoflagella ▪ Labile in the environment and sensitive to desiccation ▪ Saprophytes: free living in ponds, rivers, surface waters, moist soil ▪ Multiple reservoir animals ▪ Pathogenic leptospiral spp. persist in renal tubules or genital tract ▪ Widespread and underdiagnosed zoonotic disease (St Kitts!) ▪ Epidemics following natural disasters Spirochetes Leptospira Leptospirosis in pigs, cattle, dogs, horses ▪ Reproductive failure, abortions, stillbirths ▪ Acute septicemic disease Leptospirosis in humans (zoonosis) ▪ Influenza-like illness, occasionally liver or kidney disease Spirochetes Borrelia burgdoferi ▪ Spirochete causing Lyme disease in animals and humans ▪ Vector: ticks (Ixodes) ▪ Most infections are subclinical ▪ Clinical disease is reported frequently in dogs: fever, lethargy, arthritis cardiac, renal or neurological disturbance Mycoplasma Mycoplasma Spirochetes Mycoplasma ▪ Smallest free-living prokaryotic microorganisms that lack cell wall ▪ Not susceptible to penicillin ▪ Mastitis, contagious bovine pleuropneumonia and arthritis in cattle ▪ Stance with head and neck extended and elbows abducted ▪ Expiratory grunting and mucopurulent nasal discharge ▪ Enzootic pneumonia in pigs Rickettsiales Obligate intracellular bacteria Rickettsiales ▪ Obligate intracellular bacteria ▪ Rickeetsia spp. and Ehrlichia spp. ▪ Transmitted through ticks ▪ Systemic diseases (targeting blood cells) in humans and animals in defined geographical regions ▪ Canine cyclic thrombocytopenia ▪ Ehrlichiosis ▪ Heartwater in ruminants