Enterobacteriaceae Flashcards
Enterobacteriaceae - members (8), morphology, metabolic requirements & habitat
Escherichia, Klebsiella, Enterobacter, Serratia, Citrobacter, Salmonella, Proteus, Yersinia
Gram - rods
Facultative anaerobes
Saprophytes or commensal of GIT/UGT
Colibacillosis - agent + VFs (4)
Escherichia coli
O Ag = LPS sugars
K Ag = capsule
H Ag = flagella
F Ag = fimbria (attachment proteins)
Colibacillosis - clinical manifestations
Enteritis = ETEC > EPEC/EHEC > EIEC/EAEC
- diarrhoea ± enterotoxaemia, oedema disease, bacteraemia
Extra-intestinal E. coli:
- Mastitis (cows)
- Pyometra (dogs)
- Respiratory colibacillosis (birds)
- Septicaemia
- UTIs
Enteritis via ETEC - VFs (2)
Fimbriae K88/K99 etc. = attachment to cilia
Enterotoxins = heat labile (LT)/heat stable (ST)
ETEC enteritis - pathogenesis
Agent ingested (by young esp)
> attach to cilial receptors via fimbriae
> enterotoxin =↑ adenylate cyclase in epithelial cells = ↑ cAMP
> Dysreg of ion pump
> Electrolyte loss into GI lumen
> secretory diarrhoea
> dehydration/death
ETEC enteritis - host factors (2)
Receptor prevalence ∝ sp. + age
- Po = K88/P987
- Rum = K99/F41
- ↓ receptor prevalence w age
Anti-fimbriae Ab is protective (colostrum/milk)
ETEC enteritis - mgt factors (2)
Intensive conditions = ↑ environmental contam
↓ body T = ↓ gut motility
ETEC enteritis - immunity, tx, dx
Fimbrial vax (po/bo)
Supportive therapy only - don’t use antimicrobials
isolate agent + show toxin elaboration potential
EPEC/EHEC enteritis - pathogenesis
Agent ingestion (poorly cooked meat)
> attachment via pilus
> type III secretion system delivers Tir into epithelial cell membranes = actin reorganisation = shape change + attachment
> EHEC secretes shiga-like toxin (↑ vasc perm) = epithelial dmg + enterotoxaemia
> haemolytic-uraemic syndrome
EIEC enteritis - pathogenesis
Enteroinvasive E. coli
Agent ingested
> invades GI epithelial cells + replicates
> cell lysis = colonic ulceration
EAEC enteritis - pathogenesis
Enteraggregative E. coli
Agent ingested
> attachment via fimbriae + aggretation on epithelial surface
> enterotoxin + Fe-binding gene elaborated
Oedema disease - agent + pathogenesis
E. coli (VTEC)
Ingestion + colonisation of intestine > oedema disease toxin into circ > ↑ vasc perm of small aa. (GI/subQ/brain) > oedema > death w neuro signs
Oedema disease - VFs (2)
Toxin-EDP = disrupts cellular protein synthesis
Specific fimbriae/adhesins
Oedema disease - host factors (2)
Weanling pigs w loss of lactogenic immunity
Assoc w rapid growth, change in diet, mild diarrhoea
Gram negative mastitis - agent + origin
E. coli
Environmental organism
Gram neg mastitis - mgt factors (3)
Poor milking hygiene
Vacuum fluctuations
Poor intramammary prep admin at drying off
Respiratory disease in birds - agent + VFs(3)
Avian pathogenic E. coli (APEC)
Adhesins = colonise RT
Fe-scavenging systems
Complement resistance
Respiratory disease of birds - route of inf + pathogenesis
Inhalation of faecally-contam dust > adhere to RT via adhesins > airsacculitis + bacteraemia > GI/liver/lung granulomas > sudden death
Respiratory disease of birds - host factors (2)
Broilers > layers
Prior RT dmg (immunosuppressive viruses, ↑ [NH3], variable T) may impair MCC
E. coli UTI/pyometra - origin/host sp + type of infection
Commensal of lower UGT in dogs/cats
> Ascending UTI of endogenous org’s
E. coli UTI/pyometra - predisposing factors (7)
Relaxed host defences/immunosuppression Δ urine composition (DM) Abnormal micturition (bladder atony) Oliguric renal failure P4 stimulation of endometrium/myometrium Calculi (reservoir/result of infection) F > M dt short/wide urethra + proximity to anus
E. coli UTI/pyometra - VFs (3)
Receptor-specific fimbriae/pili = adhesion
Haemolysin
Cytotoxic necrotising factor
Bacteraemia/sepsis dt E. coli - predisposing factors + route of infection/pathogenesis
Neonates (esp w FPT/poor hygiene)
Entry via umbilicus > multiplication in lymph/blood > endotoxaemia + localisation
Klebsiella pneumoniae - habitat, diseases caused (3)
Commmensal of intestine (survives in moist environment e.g. wood shavings as bedding)
Opportunistic pathogen
- cystitis (ca), mastitis (bo), metritis/endometritis (eq.)
Predisposition via heavy AM use
Lactose fermenting Enterobacteriaceae
E. coli Klebsiella pneumoniae Enterobacter Serratia Citrobacter
Non-lactose fermenting Enterobacteriaceae
Salmonella
Proteus mirabilis/P. vulgaris
Shigella
Yersinia pestis/Y. pseudotuberculosis/Y. enterocolitica/Y. yuckeri
Salmonellosis - disease manifestations (3)
Enteritis
Septicaemia > pneumonia/meningitis/polyarthritis
Abortion
Salmonellosis - transmission (mammals + birds)
Inapparent carries w intermittent/long-lasting shedding (induced by stress)
Birds (S. gallinarum/pullorum) = transovarial
Enteric salmonellosis - serovar + pathogenesis
S. typhimurium
Faecal contamination > inf by ingestion (dose-dependent)
> colonise/invade GI epithelium
> intracellular multiplication + cell-cell spread
> Inflamm response (PG = hypersecretion + ↑ vasc perm TF fluid exsorption)
> Ileitis/colitis
> spread to mesenteric LNs
> bacteraemia/septicaemia w endotoxaemia
> hypovolaemia shock, fever, coagulopathies, hypoglycaemia, death
> localisation to cause abortion, meningitis etc.
Salmonellosis - VFs (4 + 5)
Multifactorial (> 80 genes for survival, chemotaxis etc.)
LPS (endotoxin) = pyrogen, shock
Adhesins (flagella - non-motile)
Salmonella Pathogenicity Islands (SPI)
- SPI-1 = type III secretion for invasion of GI epithlium
- SPI-2 = type III secretion for survival
- SPI-3/4 = survival in MP
- SPI-5 = intestinal phase
Salmonellosis - host factors (2)
Carrier state = persistent active/intermittent latent excretion induced by stress
Stress > ↑ susceptibility to inf
Salmonellosis - mgt factos (3)
↑ stocking density = ↑ env contam + stress
Nosocomial inf common
Faecal contam of food/water = ↑ ingested dose
Salmonellosis - immunity + vax type
CMI + humoral
Live attenuated vax
Salmonellosis - tx
Multiple drug resistance is common (chloramphenicol)
AM tx of intestinal cases > enhanced dz
Salmonellosis - dx (2)
Selective enrichment from faecal samples
Serology (agglutination)
Pathogenic Proteus spp. (2)
Diseases caused by Proteus (2)
Proteus mirabilis > P. vulgaris
Opportunistic UTI/cystitis in small animals
Diarrhoea in pups/kittens
Pathogenic Yersinia spp. + disease caused (4)
Y. pestis - bubonic plague (human)
Y. pseudotuberculosis - systemic dz or enteritis (rum.)
Y. enterocolitica = enteritis (humans/rum)
Y. yuckeri = enteric redmouth (fish)
Yersinia pseudotuberculosis - route of infection + pathogenesis
Ingestion of agent > adhesion/invasion of GI epithelium > mesenteric LNs > MP attracted but killed by Yop effectors (t3SS) > LN abscessation > liver/spleen inf then abscessation > bacteraemia, death
Yersinia pestis - reservoir + route of inf + pathogenesis
Reservoir in rats
> Infection by flea bites = direct inoculation into tissue (TF no GI phase)
> LNitis (buboes) + lung abscesses (prone to rupture > transmission by aerosols)
Yersinia pseudotuberculosis VFs (4)
Adhesins = colonisation of GI
T3SS = delivers Yop effectors into MP
- Secretion induced by shift to 37 deg C/contact w host cells
Yersinia pestis VFs (2 plasmids)
Bacteriocin//plasminogen activator = ↑ invasiveness Murine toxin (exotoxin)/capsular Ag
Yersinia pseudotuberculosis - epidemiology
Wild bird/rodent reservoir
Diarrhoea in 1-2yo sheep/calves in winter-spring
Yersinia tx
Tetracycline
may induced reactivated excretion
