16. enterobacteriaceae
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The document discusses the taxonomy, characteristics, and clinical significance of the family Enterobacteriaceae. It describes key genera including Citrobacter, Enterobacter, Klebsiella, and their roles as normal gut flora but also opportunistic pathogens. Klebsiella pneumoniae is highlighted as an important cause of nosocomial infections like pneumonia, meningitis, and sepsis. Laboratory identification involves culture-based methods and biochemical tests to distinguish lactose fermenters from non-fermenters. Treatment requires combination antibiotics and is guided by susceptibility testing due to rising multidrug resistance.
16. enterobacteriaceae
- 1. ENTEROBACTERIACEAE KIMAIGA H.O MBChB (University of Nairobi)
- 2. Taxonomical Classification Two important classifications • Based on taxonomy • Kingdom- Bacteria • Phylum- Proteobacteria • Class- Gammaproteobacteria • Order- Enterobacteriales • Family – Enterobacteriacaea • Based on lactose fermentation
- 3. TRIBE GENUS I Escherichieae Escherichia, shigella II Edwardsielleae Edwardsiella II Klebsielleae Klebsiella, Enterobacter, Edwardsiella, Hafnia, Serratia III Salmonelleae Salmonella, Arizona IV Citrobactereae Citrobacter IV Protease Proteus, Providencia, Morganella V Yersineae, Yersinia, Pasteurella Erwinieae Erwinia, Pectobacterium TAXONOMY (Ewing) • Tribe concept proposed by Ewing group in genera that share similar biochemical reactions and diagnostic importance (7 Tribes)
- 4. Classification based on lactose fermentation Lactose fermenters (LF) • Citrobacter • Enterobacter • Escherichia coli • Klebsiella Non lactose fermenters (NLF) • Salmonella • Shigella • Yersinia • Proteus • Serratia Late lactose fermenters • Shigella sonnei • Edwardsiella,, Citrobacter, Arizona,Providencia, Erwinia
- 6. General characteristics • Primarily normal flora in intestinal tract of humans and animals and others found in water and soil. Also called coli forms or enteric bacteria • Gram negative rods • Ferment carbohydrates/glucose with acid production • Most are oxidase –ve (lack cytochrome oxidase) • Catalase +ve • Facultative anaerobes • Non-capsulated except Klebsiella • Non-spore forming • Some motile by peritrichous flagella few genera non motile e.g Klebsiella • Contain endotoxin in cell wall • Most reduce nitrate to nitrite via nitrate reductase • Grow in media with bile salts (MacConkey) • Combinations of chromosomal & plasmid-mediated drug resistance hence importance of in-vitro susceptibility testing
- 7. • Media used to distinguish Lactose fermenters and Non-Lactose Fementers • MacConkey agar - LF-colored/pink, NLF- colorless colonies • Eosin Methylene Blue (EMB) agar • Salmonella Shigella (SS) agar • Triple Sugar Iron (TSI)agar - Slant, butt, gas, H2S
- 10. CITROBACTER • Normal intestinal flora may cause opportunistic infections. • NLF, Associated with nosocomical UTI and respiratory infections, Endocarditis, neonatal meningitis and brain abscesses • Treatment • Multidrug resistance • Aminoglycosides/ carbapenems/ quinolones/ antipseodomonal penicillins
- 11. Enterobacter species • Previously known as aerobacter spp • Compromised of 12 species; E. cloacae and E. aerogenes are most common Characteristics • Cononies resemble Klebsiella • Motile peritrichous flagella • IMViC--++
- 12. Clinical manifestations • Commensals in the human gut • Most strains cause infections in immunocompromised individual- hospital impatients • Cause wound infections, burn infection, pneumonia, UTI, Intra-abdominal infections, neonatal Resistance • 1st generation cephalosporins • -lactamase production – resistance to many cephalosporins Treatment • Carbapenams,4th generation cephalosporins • Ampicillin and gentamicin- E.sakazakii
- 13. KLEBSIELLA SPECIES • Klebsiella pneumonia – Lobar pneuomina , Most common • K. oxytoca.- Lobar pneumonia • K. ozaenae – atrophic rhinitis (ozena) • K. rhnosceleromatis- rhinoscleroma (Granuloma of the nose and pharynx) • K. granulomatis- Granuloma inguinale/ donovanosis- painless, non-purulent genital ulcer • Klebsiella, Citrobacter, Hafnia, Serratia • Habitat – large intestines, soil, H2O
- 14. Pathogenesis Virulence factors • Large polysaccharide capsule. Capsular K antigen- antiphagocytic capsule • Synthesis of siderophores, that are capable of competitively taking up iron bound to proteins • Pili – adherence to respiratory and urinary epithelia • Endotoxin – The carry plasmids that code for heat labile and heat stable toxins. Gram negative septic shock
- 15. CLINICAL PRESENTATION • Pulmonary infections- pneumonia lobar; • High fatality • Predisposing factors : elderly, chronic respiratory dx, diabetes, alcoholism • Extensive necrosis and hemorrhage resulting in thick, mucoid, brink red sputum currant jelly like. • Extrapulmonary infections • Meningitis and enteritis in infants • UTI • Septicemia/Bacteremia • Cholecystis, cholangitis, otitis media, sinusitis, peritonitis, wound/ burn infections, • AN important cause of nosocomial infections • K.rhinoscleromaticus – inflammatory granulomatous lesions of nose, pharynx, etc
- 16. LAB DIAGNOSIS • Specimens - urine, pus, blood, sputum, CSF • Gram –ve rods • Culture:- MAC , CLED, or BA:— • Growth conditions, 350C ,18-24 hrs • Mucoid colonies, pink(LF) in MAC and CLED • LF thus yellow in CLED and pink in McC • Non motile • Biochemical tests • IMViC(--++) • Urease positive • TSI- acid slant, acid butt, gas, no H2S • KSM positive • K pneumoniae can liquefy gelatin. • Short and plump- Capsule swelling (Quellung reaction)– Typing based on about 90 capsular (K) antigens there are three types – K2,K3 and K21. Rapid identification.
- 17. Gram –ve Klebsiella rods
- 18. Klebsiella on MAC Klebsiella Spp BA
- 19. Klebsiella on NA Klebsiella on CLED
- 21. Klebsiella_Citrate test Indole test
- 22. Klebsiella ferments inositol but E. coli does not
- 23. TREATMENT • Hospital- acquired infections – resistance to multiple antibiotics • Based on antibiotics susceptibility tests • Beta lactam + beta lactamase inhibitior combination • 3rd generation of cephalosporins e.g cefataxime, ceftriaxone + aminoglycoside