Enterobacteriaceae

1. Enterobacteriaceae • Family Enterobacteriaceae (Escherichia, Klebsiella, Proteus, Enterobacter, Serratia, Citrobacter, Morganella, Providencia, and Edwardsiella)

2. MacConkey agar plate inoculated with the gram-negative lactose fermenter and the gram-negative non-lactose fermenter

3. Enteric Gram Negative rods • Lactose Fermenting • Escherichia Coli • Klebsiella • Enterobacter • Citrobacter • Lactose Non Fermenting • Salmonella • Shigella • Morganella • Providencia • Serratiia

4. E.ColiUTI, travellers’ diarrhea, haemorrhagic colitis, haemolytic uraemic syndrome

5. Morphology • gram-negative bacilli • Motile • Facultative anaerobe Named for Theodor Escherich. German physician (ca. 1885). Demonstrated that particular strains were responsible for infant diarrhea and gastroenteritis

6. selective media MacConkey,s Agar culture

8. Antigenic structure • O antigen • Somatic (on LPS) • 171 antigens • H antigen • Flagella • 56 antigens • K antigen • Capsule and or fimbrial antigen • 80 antigens • O18ac:H7:K1 18th O antigen 1st K antigen 7th H antigen

9. Pathogenesis • Adhesion of the microorganisms to the intestinal epithelial cells • Production of enterotoxins Heat labile (LT) and Heat stable (ST) • Verotoxin production of cytopathic effects in green monkey kideny cells • Invasion of epithelial cells

10. Adherence Fimbriae Urovirulence Factors Hemolysis a b Capsule K antigens Resist phagocytosis Resist complement proteins Aerobactin Siderophore Endotoxin

11. E. coli Sepsis For people with inadequate host defenses, e.g. the newborns. Usually originates from UT or GI infections. Some infections may be endogenous. Meningitis E. coli (particularly K1 strains) and S. agalactiae are the leading causes of meningitis in infants. Bacteremia

12. E. coli Pathogenesis and clinical diseases Urinary tract infection E. coli is the most common cause of urinary tract infection. Community- vs. hospital-acquired UT infection Most infections originate from colon; the bacteria contaminate the urethra, ascend into the bladder, and may migrate into the kidney or prostate. Symptoms: urinary frequency, dysuria, hematuria, and pyuria. Can result in bacteremia and sepsis. Uropathogenic E. coli strains produce P (Pyelonephritis-associated) pili, which is associated with renal colonization and may induce protective immunity, and hemolysin HlyA.

13. Intestinal affections

14. E. coli • Certain strains of E. coli • ingested in sufficient quantities by host. • enteritis, enterocolitis, and colitis • pathogenic strains of E. coli which cause disease in the intestine are obligate pathogens.

15. six distinct "pathotypes" of E. coli (which cause disease in intestine) • Enteropathogenic E. coli (EPEC), • Enterotoxigenic E. coli (ETEC), • Shiga toxin-producing E. coli (STEC)/enterohemorrhagic E. coli (EHEC), Verocytotoxin-producing E. coli (VTEC) • Enteroinvasive E. coli (EIEC), • Enteroaggregative E. coli (EAEC) (EAggEC) • diffusely adherent E. coli (DAE)

16. Enteropathogenic E. coli • EPEC is an important cause of infant diarrhea • Breast-feeding diminishes the incidence of EPEC infection. • Rapid person-to-person spread may occur. • After infection with EPEC there is loss of microvilli. • Sometimes the EPEc enter the intestinal cells.

17. Enterotoxigenic E. coli • ETEC is a major cause of endemic diarrhea in children during the first 3 years of life. • ETEC is the most common agent of traveler's diarrhea, • There is production enterotoxin • two components

18. Enterotoxigenic E. coli  • heat-labile toxin (LT) and/or a heat-stable toxin (ST) • fluid secretion via activation of adenylate cyclase (LT) and • or guanylate cyclase (ST) in the jejunum and ileum; the result is watery diarrhea accompanied by cramps. • The disease spectrum ranges from a mild illness to a life-threatening cholera-like illness.

19. Where are the genes for LT and ST • Plasmid • Can be transferred to any E.coli • These genes also code for colonization factors.

20. EHEC • undercooked ground beef is usually the vehicle of infection. • O157:H7 is the most prominent serotype which produce the verotoxin

21. EHEC • In contrast to the other pathotypes, STEC/EHEC/VTEC causes infections more frequently in developed countries, • the consumption of processed foods is more common than in developing regions • The vero toxin resembles the shiga toxin produced by shigella dysenteriae

22. Haemolytic uremic syndrome (HUS) • Haemolytic anaemia • Acute renal failure • Thrombocytopenia The verotoxin enters the blood stream

23. Enterotoxigenic E. coli /how to detect L.Toxin • Accumulation of fluid in the intestine of lab.animals • Bringing of typical cytological changes in tissue culture • Stimulation of steroid production in cultured adrenal cells . • Immunological assays with antisera.

24. EHEC • Produce verotoxin-CPE in vero cell line African green monkey kidney cells • an emerging group of pathogens • can cause hemorrhagic colitis and the hemolytic-uremic syndrome (HUS). • undercooked ground beef is usually the vehicle of infection. • O157:H7 is the most prominent serotype which produce the verotoxin

25. Enteroinvasive E. coli  EIEC • a relatively uncommon cause of diarrhea, • EIEC shares many genetic and clinical features with Shigella • The disease resembles the shigellosis • The difference • EIEC produces disease only at a large inoculum (108 to 1010 CFU8), with onset generally occurring after an incubation period of 1 to 3 days.

26. Enteroaggregative and Diffusely Adherent E. Coli  EAEC and DAEC • primarily in developing countries and in young children. • These strains can cause traveler's diarrhea. • A large inoculum is required for infection. • In vitro, the organisms exhibit a diffuse or "stacked-brick" adherence pattern.

27. Lab Diagnosis

28. specimens • Urine • Stools • Blood • Csf

29. Microscopy • The enterobacteriacae resemble each other • E.coli can not be differentiated from other genera morphologically

30. Culture • The specimens cultured on to selective and differential media or combination of selective and differential media. • Typical lactose fermenting colonies are picked up sub cultured on to non selective media • Subjected to biochemical test/semi automated identification systems

31. Lab Diagnosis • Potentially pathogenic E. coli cannot be distinguished from non pathogenic E. coli by routine culture

32. Identification of serotypes/pathotypes • Usually performed at reference lab • The E. coli isolate treated ,standardized and allowed to react with antisera (known antibodies) in antigen antibody reactions • and designated • Special tests to detect LT and ST are not available in most clinical laboratories

33. Lab Diagnosis/non specific • make distinction is between inflammatory and noninflammatory disease.

34. Lab Diagnosis • Grossly bloody or mucoid stool suggests an inflammatory process. • A test for fecal leukocytes (preparation of a thin smear of stool on a glass slide, addition of a drop of methylene blue, and examination of the wet mount) can suggest inflammatory disease in patients presenting with diarrhea, • A test for fecal lactoferrin, which is a marker of fecal leukocytes, is more sensitive and is available in latex agglutination and enzyme-linked immunosorbent assay formats.

36. o-Nitrophenyl-f8-D-galactosidase ONPG Arginine dihydrolase ADH Lysine decarboxylase LDC Ornithine decarboxylase ODC Citrate utilization CIT H2S production H2S Urease URE Tryptophan deaminase TDA Indole production IND Acetoin production VP Gelatinase GEL Glucose fermentation GLU Mannitol fermentation MAN Inositol fermentation INO Sorbitol fermentation SOR Rhamnose fermentation RHA Sucrose fermentation SAC Melibiose fermentation MEL Amygdaline fermentation AMY Arabinose fermentation ARA

37. Antimicrobial resistance • They are susceptible to a number of antimicrobials • MDR resistance strains have evolved • Antimicrobial sensitivity performed • Antibiotic policy • Antibiotic policy evolved keeping in mind a number of factors • Cost • Sensitivity patterns • Convenience of the patient

38. Principles of treatment • In addition of antimicrobials • Restoration of fluid and electrolyte balance • Treatment of DIC

39. Prevention of Traveller,s diarrhea • be careful in endemic areas of food and water • Ingestion of daily subsalicylate which inactivates the E. coli enterotoxin • Ingestion of prophylactic antimicrobials • They are not fully successful