Transcript
Genera Genus species
Morphology
Shigella Sh. Dysenteriae (gpA) Sh. Boydii (gpB) Sh. Flexneri (gpC) Sh. Sonnei (gpD) Non motile Slender Yg culture: cocobacilla Convex, circular, transparent colonies with intact edges Reach diameter=2mm in 24hrs
Non- sporing, Facultatively anaerobic, Gram -ve bacilli, Enterobacteriaceae (SSKYPPE) Salmonella Klebsiella Yersinia Proteus S. Paratyphi A K. pneumoniae Y. pestis Pr. Vulgaris S. Paratyphi B K. ozaenae Y. enterocolitica Pr. Mirabilis S. Choleraesuis (C1) K. rhinoscleromatis Y. pseudotuberculosis (most common) S. Typhi (D) Motile w peritrichous Non-motile Short, pleomorphic, exhibit Highly motileflagella Have thick bipolar staining (Giemsa stain) xhibt ‘swarming May lose H Ag & become polysaccharide capsule growth x-motile phenomenon’ May lose O Ag: Δ from smooth→ rough colony ‘swarming growth phenmnn’ concentric zones of growth around centre of inoculation on enriched solid culture media -LPS that have endotoxic xtvt -Envelope contains protein (fraction I) that is produced at 37°C- antiphagocytosis -Y. pestis: V-W Ag Non-lactose fermenting Oxidase -ve Catalase +ve Facultative intracellular Grows at 28°C, 2-5 days to develop colony
Providencia
Escherichia
Agnc structure
Culture
Typicl
O Ag (LPS): > 40 types *used for serotyping Shiga Toxin
Vi Ag- evade phagocytosis
EHEC: O157: H7
Growth Characteristic
Glucose fermenter (xcpt Sh. Sonnei) Non lactose fermenter Anaerogenic (form acid from C’hydrte, rarely produce gas) Grow best aerobically Oxidase -ve
Non-lactose/ sucrose fermenter Many produce H2S Survive in freezing water Oxidase -ve
Lactose- fermenter Oxidase -ve
Non-lactose fermenter Oxidase -ve
Oxidase -ve
EHEC isolatd on sorbitol MacConkey agar Oxidase -ve
Enzymes & others
Production
Y. pestis Isocitrate lyase Coagulase (at 28°C)
Urease-splits urea into ammonia that alakalinize surrounding medium
Toxin
Endo Exo
LPS (contributes to the irritation of bowel wall)
Sh. dysenteriae: Shiga Toxin heat labile similar to verotoxin of E. coli (production limitd to Sh. dysenteriae type 1 which cause most severe disease)
Toxin that produce betaadrenrgc blockade (cardiotoxic in animal only) Bacteriocin (pesticin)
EHEC: Verotoxin EAEC: produce exotoxin (unspecified) ETEC: LT & ST exotoxins LT: heat labile, ↑cAMP ST: heat stable, ↑cGMP
Habitat
Intestine of human
Animal gut (zoonosis) S. Typhi & S. Paratyphi are strict human pathogen
Intestinal tract of human & animal In feces & URT of healthy individuals Some- saprophytes in soil & water
Y. pestis Rodent. Vector: flea (Xenopsiella cheopis)
Human & animal intestine
Epidemiology
Aetiology
Transmission: 4Fs- Food, finger, feces, flies Control: isolatn of pt & disinfctn of excreta Long term carriage is unusual Infectve dose: 103 Plasmid-coded Ag Mediate enterinvasiveness Shiga Toxin(enterotoxn) Affect gut, CNS
EPEC: infant ETEC & EIEC: various age gp esp infants & travelers to endemic area Infctve dose: 105- 108 Contaminatd food/ drink Transmttd from poultry/ egg K. pneumoniae K. ozaenae- ozena K. rhinoscleromatis rhinoscleroma Y. pestis -Bubonic plague- flea bite -Primary pneumonic plagueinhalatn of infctve droplet from pt w pneumonia EHEC: undercooked ground beef Virulence factors causing diarrhea: ETEC: enterotoxin (exo) Adhesins EIEC: enteroinvasiveness EHEC: verotoxin; serovar O157:H7 EPEC: attaching-effacing mchnsm
Pathogenesis
Enter M cells of large bowel by inducd phagocytosis ↓ Escapes from phagosome Shiga Toxin inhibits protein synthesis ↓ Coz dissemintd endothll damge ↓ Intravascular coagulant, hemolysis, renal failure ↓ Hemolytic Uremic syndrome Shiga Toxin inhibts sugar & aa absorptn in SI • produces diarrhea w same mechanism w E. coli verotoxin • act as neurotoxin Limited to GIT Microabscess in terminal ileum & LI wall Necrosis of mucous membrane Superficial ulceration Haemorrhage Bactaerimia is rare •
Y. pestis Flea feeds on blood of infctd rodents ↓ Organism multiply in gut, produce coagulase & fibrin clot that blocks proventriculus ↓ Infctd flea bites uninfctd rodent/ human. Aspiratd blood become contamintd & regurgitatd into bite d/t blocked flea gut (biting frenzy) ↓ Organism multiply locally in man mΦ (but phagocytosed by PMN) ↓ Produce fraction I ↓ Spread via lymphatic to LN
Lesion
Enteric fever (typhoid fever) Hepatitis Hyperplasia + necrosis of lymphoid t/s Splenomegaly Hepatomegaly Liver focal necrosis Cholecystitis Septicemia Focal lesion in lungs, bones, meninges Enterocolitis
K. pneumoniae UTI Septicemias Bacterial meningitis Pneumonia (rare) K. rhinoscleromatis Destructive granuloma of nose & pharynx
Y. pestis Hemorrhagic necrotizing inflammtn of LN Y. enterocolitica, Y. pseudotuberculosis Enteritis w ulceration Mesenteric lymphadenitis
• UTI Alkalinization oof urine by ammonium salts predispose to urinary calculi (phosphate stone in particular)
Sepsis • • • • •
UTI Wound ifxn Peritonitis Biliary tract ifxn Septicemia
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Particip ate in mixed ifxn: wounds, burns, pressure
Neonatal meningitis (75% E coli isolated have K1 Ag whch cross-reacts w gp B meningococcal polysaccharide Ag) ETEC
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Inflammatory lesion of SI & LI
sores, chronic otitis media • Septice mias
Bacteria multiply in small bowel EIEC • Severe systmc toxicity • Bacteria multiply in colon EPEC Adhere tightly to intestinl mucosal cell→ effacement of microvilli EHEC • Haemorrhgc colitis
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PMN in stool
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Hemolytic uraemic syndrome
Clinicl signs
Incbtn prd: 1-2 days Sudden abdominal pain, fever, watery diarrhea. After a day or so, stool↑, less liquid + blood + mucus Tenesmus (rectal spasms)→ lower abdmnl pain
Enteric fever After incbtn period (10-14 days): Fever, malaise, headache, constipation, bradycardia, myalgia Rose spots on abdominal & chest skin (rare) Septicemia Early invasion of blood stream Intestinal manifsttn absent Enterocolitis After incbtn prd (848hrs): Nausea, headache, vomiting, profuse diarrhea, low grade fever -resolve in 2-3 days
Y. pestis Incubtn period: 2-7 days Bubonic plague High fever Enlarged tender regional LN (buboes) in axilla & groin Vomiting, diarrhea Hemorrhagic manifsttn & hypotension d/t DIC leading to multiple organ failure Y. enterocolitica, Y. pseudotuberculosis Abdominal pain resemble appendicitis
ETEC • Severe watery diarrhea • Min abdmnl pain & cramping EIEC • Dysentery • Fever • Severe abdmnl pain & cramping • Tenesmus • PMN in stool EAEC • Acute/ chrnc diarrhea EPEC • Watery diarrhea
Complication
As process subsides, granulatn t/s fills the ulcers, scar forms Fever diarrhea subside spontnsly 2-5 days. In chldrn & elderly, loss of water & electrolytes→ dehydration, acidosis, fatal Most remain s carrier
Y. pestis Septicemia, disseminated ifxn leading to DIC & septic shock Terminally ill pt develop pneumonia, meningitis Mortality: very high unless treatd promptly
Diagnosis
Treatment
Prevention
Ciprofloxacin Ampicillin Doxycycline Trimethoprimsulfamethoxazole Ab x prtct against reinfection
Chlormphenicol Ampicillin Cotramixazole 3rd gen cephalosporin
Streptomycin Tetracycline