Gram negative bacilli
- 1. GRAM –ve Bacteria: BACILLI ENTEROBACTERIACEAE ‘Coliforms’ BACTERIA Salmonella Escherichia Campylobacter S.enterica E.coli C.jejuni C.fetus PATHOGENISIS Primary pathogen Acute enteritis and systemic infection (septicemia/abortion) Phagocytosed: Facultative intracellular Salmonellosis 1°/Opportunistic UTI, Pyometra (dog/cat) Acute mastitis Avian colibacillosis Colisepticemia Thermophillic Humans: Enteric disease C.jejuni: enteropathogen of man and animal; food poising -‐> Collitis Non-‐thermophilic Sheep & Cattle: Infertility and abortion C.coli Pigs TOXIN Cytotoxicity for enterocytes (diarrhea) α-‐haemolysin High affinity Fe-‐a (Aerobactin) K-‐antigens: capsules (prevent phag/mimic antigen) ETEC: Enterotoxin (LT & ST) EPEC: effacing lesions EHEC: SLT; haemorragic Verotoxin: Oedema & haem: pigs Colonisation, attachment, invasion and toxin production Colon damage = necrosis of absorptive epi cells, erosion of mucosa, crypt abscesses and infiltration of inflame cells Functional flagella: Virulence factors (non-‐flagellate do not colonise in vivo) SPREAD Persist in gut/gall bladder: con’t excreted in faeces after clinical recovery/stress Flora of colon (L.I): abundant in faeces Extraintestinal Blood -‐> septicemia Cattle, sheep, dog, chickens, wild birds carry C.jejuni in intestines – Hyperendemic on farms Alimentary tract of reptiles and mammals CHARACTERISTICS/ STERILISATION Facultative anaerobe Classification: O (group) and H (serovar) agglutination with known antiserum Grouped: Kauffmann-‐White scheme* Aerobic O and H antigens AND K (fimbrial) Classification: Antigen combinations Fimbriae: adhesion Curved G-‐ve Microaerophilic = hard to grow V.sensitive to drying Active immunity can develop, but sterile env means not exposed. TRANSMISSION Faecal-‐Oral route: large dose due to gastric acidity & gut flora/fauna Faeces Respiratory Blood Fecal-‐oral and passive (colostrum) DIAGNOSIS Isolate; enrichment (selenite broth); incubate to inc N0; inc sensitivity; strong selective medium (XLD) Urease -‐ve Indole -‐ve Non-‐lactose fermenter Utilise citrate as sole C Produce H2S (Black colonies) Lactose fermenter (Yellow) Vaccination (passive;colostrum) – insufficient=overgrowth in S.I. endotoxin absorption and death (watery mouth in lambs) Oxidase test: -‐ve Reduce NO3 -‐ to NO2 -‐ Proteolytic digestion of gelatine Identify with API 20E system of 20 biological tests ETEC: Enterotoxigenic EPEC: Enteropathogenic EHEC: Enteroheamoragic
- 2. GRAM –ve Bacteria: BACILLI NON-‐ENTERIC BACTERIA Psudomonas Brucella Bordatella Pasturella Mannheimia Mycoplasma P.aeruginosa B.abortus B.bronchispetica B.avium P.multocida M.haemolytica Spirochaetes: swine dysnentry, lyme disease, leptospirosis Rickettsia: Tick & Louse borne Chlamydophilia: live in cells, look viral; enzootic abortion, feline conjunctivitis *No cell wall peptidoglycan PATHOGENISIS Opportunistic Facultative intracellular Brucellosis Disease when infects LOWER RESP tract Brodatellosis Kennel Cough Rhinotra cheitis in poultry 1°: Fowl cholera (septicemia) and epizootic haem sep (cattle – not in UK) Atrophic.r (pigs) Snuffles; pasteurellosis (rabbits) 2°: LUNGS following mycoplasmal; Pig enzootic pneumonia/ wound infections Previously Pasteurella haemolytica Epizootic pneumonia (cattle) and sheep; pasteurellosis Severe mastitis (sheep/goats) Colonise (use pili) in ciliated tracheal epithelium: exudate; nasal discharge TOXIN Secretes pyocyanin (green/blue puss) Fimbria Exotoxin A (inhib host protein syn), Elastase (destroy elastin), proteases, hydrolytic enzymes Penetrate mucosa; Phagocytosed; Granulomatou s inflame reactions Adenylate cyclase cytolysin: (w/RTX): immobilises neutrophils LT dermonecrotic toxin: turbinate atrophy in pigs Fimbriae, filamentous haemaglutanin = adhesion 5 capsular serotypes (A,B,D,E,F) A&D; normal flora. Some produce osteolytic toxin B&E; haem sept cattle Cytotoxin; leukotoxin: RTX group toxins: crucial for pathogenicity in septicaemia and pneumonia SPREAD Look like enterobacteria Free living Smell! Multiple antibiotic resistance – plasmids w/R-‐factors and chromosomally-‐ encoded efflux pump genes Grow on MacConkey Spleen, liver, lymphatics UPPER RESP tract of dogs, cats, pigs, rabbits (*NOT ruminants) UPPER RESP mucosa and GI tracts of domestic and wild animals CHARACTERISTICS Small G-‐ve coccobacilli Major O-‐ antigen Eradicated in UK Grow on MacConkey Short rods Some coccobaccili Bipolar staining Catarrhal odour Large, grey colonies on blood agar Do NOT grow on MacConkey Stains β-‐haemolytic on blood agar Grows weakly in MacC DIAGNOSIS TREAT: Gentamicin/Tobramy cin/ 3 rd generation cephalosporins (fluorinated 4-‐ quinolones)/surgery Serological tests (milk ring) Non-‐fermenters: Strict aerobes Respiratory metabolism Glucose fermenters Oxidase +ve (cytochrome C) -‐> O2
- 3. GRAM –ve Bacteria: BACILLI