ENTEROBACTERIACEAE

1. ENTEROBACTERIACEAE B.A.Fontanilla, MD Department of Microbiology and Parasitology

2. GENERAL CHARACTERISTICS • Taxonomy • Morphology • Physiology • Antigenic Structure • Determinants of Pathogenicity • Clinical Infection

3. ENTEROBACTERIACEAE • Large number of closely related species - found in soil, water, decaying matter - found in large intestines of human, animals and insects ----”enterics” or “enteric bacilli” - includes causative agents of gastrointestinal diseases - causative agents of nosocomial infections

4. ENTEROBACTERIAECEAETAXONOMY • Cedecea • Citrobacter • Edwardsiella • Enterobacter • Escherichia • Ewingella • Hafnia • Klebsiella • Kluyvera • Morganella • Proteus • Providencia • Rhanella • Salmonella • Serratia • Shigella • Yersinia • Enteric group

5. ENTEROBACTERIACEAEMORPHOLOGY • Small 0.5 x 3.0 µ • Gram-negative • non-spore-forming bacilli • May be motile or non-motile If motile – peritrichous flagella nonmotile – Shigella and Klebsiella

6. ENTEROBACTERIACEAE • Biochemically diverse • Facultative organisms • When grown in anaerobic or low O2 - ferment carbohydrates • When grown in sufficient O2 - utilize the TCA cycle and the electron transport system for energy production

7. ENTEROBACTERIACEAEPHYSIOLOGY • Ferment glucose • Reduce nitrates to nitrite • Do not liquify alginate • Oxidase negative • Basis for speciation within a family - differences in carbohydrate they ferment - variations in end-product production - variation in substrate utilization

8. ENTEROBACTERIACEAECULTURAL CHARACTERISTICS • On non differential or nonselective media blood agar or infusion agar - no species distinction - appear as moist, smooth, gray colonies • Selective media -To isolate Shigella and salmonella from fecal matter • Differential media – selectively inhibit gram-positive organisms and to separate enterics in broad categories

9. ENTEROBACTERIACEAEANTIGENIC STRUCTURE • In serologic typing, antigenic structures are used for classification and epidemiologic studies - Capsular (K) antigens - Flagellar (H) antigens - Somatic (O) antigens

10. ENTEROBACTERIACEAEANTIGENIC STRUCTURE • Capsular (K) antigens - Klebsiella species has a well defined polysaccharide capsule - in other genera, amorphous slime layer surrounding the bacterial cell - in E.coli – proteins and form fimbriae not capsules - Vi antigen of Salmonellatyphi

11. ENTEROBACTERIACEAEANTIGENIC STRUCTURE • Flagellar antigens - proteins -antigenic variation is due fo differences in amino acid sequences -antigenic typing of Salmonella is based on serologic typing of flagellar antigens

12. ENTEROBACTERIACEAEANTIGENIC STRUCTURE • Somatic antigens - O antigens is the most external part of the cell wall lipopolysaccharide (LPS) - may enhance the establishment of the organism in the host.

13. ENTEROBACTERIACEAEANTIGENIC STRUCTURE • Flagellar (H) antigens - proteins - antigenic variation of various flagellar types due to differences in amino acid sequences - serologic typing of flagellar antigens – basis for antigenic typing of Salmonella typhi

14. ENTEROBACTERIACEAEDETERMINANTSOFPATHOGENICITY 1. ENDOTOXIN - LPS (review structure p. 26 Jawetz) - resides in the lipid A portion of the LPS - produces, fever, fatal shock, leukocytic alterations, regression of tumors, alteration in host response to infection - pooling of blood in the microcirculation - causing cellular hypoxia and metabolic failure due to inadequacy of blood in vital organs

15. ENTEROBACTERIACEAEDETERMINANT OF PATHOGENICITY 2. ENTEROTOXIN -Toxins that affect the small intestines - transduction of fluid in the lumen –diarrhea 3. SHIGA TOXINS AND SHIGALIKE TOXINS (Verotoxins) – actions on Vero (African green monkey) tissue culture cells - Shigella – toxin that interferes with protein synthesis of cells - E.coli – hemolytic diarrhea

16. ENTEROBACTERIACEAEDETERMINANTS OF PATHOGENICITY 4. COLONIZATION FACTORS - cellular surface factors: capsule – Klebsiellapneumoniae “Vi” antigen – S. typhi 5. Other Factors - ability to penetrate epithelial lining – E.coli - Shigella - Salmonella

17. ESCHERICHIA

18. ESCHERICHIA • Includes 6 species • 5 species associated with human disease Escherichiablattae Escherichiacoli Escherichiafergusonii Escherichia hermanii Escherichia vulneris

19. ESCHERICHIA COLI • Grows well on commonly used media • On enteric isolation media – lactose fermenting colonies • On blood agar – β-hemolytic (assoc with UTI) • Majority – non-pigmented, motile • Produce lysine decarboxylase, use acetate as carbon source, hydrolysis of tryptophan to indole

20. ESCHERICHIA COLI • Serologic typing is based on the determination of the O antigen type, the H antigen type and when applicable the K antigen type. - 164 O antigens - 100 K antigens - 50 H antigens Example: Serotype O157:H7 – hemorrhagic colitis Serotype O124:H30 –enteroinvasive; bacillary dysentery

21. ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY • Surface Factors a. K1 capsule – E.coli with K1 capsule cause neonatal meningitis b. O antigen c. S fimbriae 2. Enterotoxins –produces watery diarrhea caused by the outpouring of fluids and electrolytes - plasmid mediated

22. ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY 2. Enterotoxin – produces watery diarrhea - plasmid mediated a. LT enterotoxin - similar to enterotoxin of Vibrio cholera - stimulates adenylate cyclase in the epithelial cells of the small intestines, increasing perrmeability of the intestinal lining, resulting to loss of fluids and electrolytes

23. ESCHERICHIA COLIDETERMINANTS OF PATHOGENICITY 2. Enterotoxin b. ST enterotoxin – ST producing E.coli do not cause diarrhea • Verotoxins (Shigalike Toxins) - associated with 3 human syndrome: - diarrhea, hemorrhagic colitis, hemolytic uremic syndrome - inhibit protein synthesis similar to Shigatoxin

24. ESCHERICHIA COLIDETERMINANT OF PATHOGENICITY 4. Other factors a. Enteroinvasiveness – strains have large plasmids that encode for O antigens b. Hemolytic – strains are nephropathogenic

25. ESCHERICHIA COLICLINICAL MANIFESTATION • Pulmonary infections – nosocomial pneumonia - most patients are 50 yrs or oldeer - with underlying chronic disease - main source: endogenous aspiration of oral secretions containing E.coli 2. Neonatal meningitis – with subsequent neurologic or developmental abnormalities

26. ESCHERICHIA COLICLINICAL MANIFESTATION 3. Wound infections – especially occurring in the abdomen 4. Sepsis – can invade the bloodstream from any of the primary infection sites

27. ESCHERICHIA COLICLINICAL MANIFESTATIONS 5. Diarrheal disease a. Enteropathogenic E.coli (EPEC) - cause of infantile diarrhea - adhere to mucosal cells of small bowell - loss of microvilli - produce watery diarrhea

28. ESCHERICHIA COLICLINICAL MANIFESTATION 5. Diarrheal disease b. Enterotoxigenic E.coli – common cause of travelers diarrhea - some strains produce LT, plasmid mediated - toxin activates adenylyl cyclase - intense and prolonged hypersecretion of water and chlorides and inhibits reabsorption of sodium

29. ESCHERICHIA COLICLINICAL MANIFESTATION 5. Diarrheal disease c. Enterohemorrhagic E. coli (EHEC) - produces verotoxin - associated with hemorrhagic colitis and hemolytic uremic syndrome - serotype O157:H7 – most common

30. ESCHERICHIA COLICLINICAL MANIFESTATION 5. Diarrheal diseases d. Enteroinvasive E. coli (EIEC) - cause bacillary dysentery in all age groups - disease is very similar to shigellosis - occurs most commonly in children - invade intestinal mucosal cells

31. ESCHERICHIA COLICLINICAL MANIFESTATION 5. Diarrheal diseases f. Enteroaggregative E.coli (EAEC) - causes acute and chronic diarrhea in persons in developing countries - produce ST-like toxins

32. To be continued….

33. KLEBSIELLA

34. KLEBSIELLATAXONOMY Klebsiella pneumoniae (Friedlander’s bacillus) Klebsiella oxytoca – Klebsiella ozeana – Klebsiella rhinoscleromatis

35. KLEBSIELLABIOCHEMICAL AND CULTURAL CHARACTERISTICS • Appear as lactose fermenting colonies on differential enteric media • Non-motile • Large capsule – colonies appear large, moist and mucoid

36. KLEBSIELLAANTIGENIC STRUCTURE • Possess O and K antigens • K antigens are most useful in serologic typing

37. KLEBSIELLADETERMINANTS OF PATHOGENICITY • Capsule – resist phagocytosis - encapsulated strains are more virulent 2. Endotoxin 3. Enterotoxin – isolated in patients with tropical sprue - similar to E.coli ST and LT - plasmid mediated

38. KLEBSIELLACLINICAL INFECTION • Klebsiella pneumoniae - cause primary community-acquired pneumonia - typical patient: middle or older aged with underlying medical problems – alcoholism, chronic bronchopulmonary disease, diabetes mellitus - most patients – thick, non-putrid bloody sputum – necrosis and abscess formation

39. KLEBSIELLACLINICAL INFECTION • Klebsiella pneumonia - can cause urinary tract infection -wound infections, bacteremia, meningitis 2. Klebsiella oxytoca – causes chronic atrophic rhinitis – fetid odor 3. Klebsiella rhinoscleromatis – infects nose and pharynx; produces granulomatous inflammation

40. ENTEROBACTER

41. ENTEROBACTER Enterobacter cloaca Enterobacter aerogenes • Non motile • Isolated less frequently than Klebsiella and E.coli - Capable of infecting any tissue in the body - Frequently associated with urinary tract infection

42. ENTEROBACTER • Most infections occur in patients with underlying problems • Usually nosocomial • Among elderly • Risks for development of Enterobacter bacteremia - long hospitalization, placement of intravenous catheters, respiratory colonization, use of antibiotics

43. ENTEROBACTER Enterobacter cloaca Enterobacter aerogenes

44. ENTEROBACTERBIOCHEMICAL AND CULTURAL CHARACTERISTICS • Motile • Grows on media used for the isolation of enterics • Rapid lactose fermenters and produce pigmented colonies

45. ENTEROBACTERANTIGENIC STRUCTURE - Antigenic subgrouping not as developed as E.coli and Klebsiella

46. ENTEROBACTERCLINICAL INFECTION • Isolated less frequently than E. coli and Klebsiella • Capable of infecting any tissue • Most frequently associated with urinary tract infection • Most infections occur in patients with underlying problems – nosocomial • Risks: long term hospitalization, plac ement of intravenous catheters, respiratory colonization; prior use of antibiotics,

47. SERRATIA

48. SERRATIA Serratia marcescens Serratia liquifaciens • Can be differentiated from other members of the Enterobacteriaceae by: - ability to produce extracellular deoxyribonuclease (Dnase), lipase and gelatinase - resistance to colistin and cephalosporin

49. SERRATIA • O and A antigens are important epidemiologic markers • All Serratia infections – associated with underlying disease, changing physiologic patterns, immunosuppressive therapy or mechanical manipulations - 90% are hospital acquired: UTI, wound infections, pneumonia, septicemia

50. PROTEUS