1. Enterobacteriaceae I: Opportunistic Pathogens

2. Enterobacteriaceae Opportunistic Pathogen: Intestinal Pathogen:
Escherichia
Klebsiella
Proteus
Enterobacter
Serratia
Edwardsiella
Citrobacter
Intestinal Pathogen:
Salmonella
Shigella
Yersinia

3. Enterobacteriaceae: General Characteristics
Gram (-) rod
Catalase(+)
Oxidase(–)
Ferment glucose
Reduce nitrate
Motile by peritrichous flagella (except Klebsiella, Shigella, Yersinia)

4. General Characteristics
Facultative anaerobes
Normal inhabitants of intestinal tract humans, other animals
Enteric pathogen
Some are urinary, respiratory tract pathogen
Differentiate by biochemical test and antigenic structure

5. Lab Culture Media CBA: Selective Media: Differential:
Colonies large, dull gray
± hemolysis
Selective Media:
Dye, bile salt inhibit G(+) MO
EMB, Mac - selective for Enterobacteriaceae:
SS, HE, XLD - highly selective for enteric pathogens, inhibit NF
Differential:
Lactose fermentation
H2S production

6. Serologic ID: Major Antigens
O - Somatic LPS antigen
Major cell wall antigen
Heat stable polysaccharide
Component of endotoxin
H - Flagellar antigen
Protein
Heat labile
K - Capsule antigen
Polysaccharide
Vi (virulence) antigen in Salmonella typhi
I.D. pathogenic E. coli O157:H7 strain

7. Biochemical Tests
TSI (Triple Sugar Iron Agar) – glucose, lactose, sucrose, H2S indicator
LIA (Lysine Iron Agar)
lysine deaminase – aerobic, slant
Lysine decarboxylase – anaerobic, butt
H2S indicator – anaerobic, butt
Motility – soft (0.4%) agar
1% Glucose broth (MR-VP) – acid or neutral metabolic end product
Citrate – use as sole C source
Indole – tryptone product
Urea – hydrolysis by urease
PAD – phenylalanine deaminase

8. Virulence Factors Endotoxin – Gram(-) cell wall:
LPS release upon cell death
Symtoms by Lipid A - fever, leukopenia, cytokine action
Immune and inflammatory response
Vasodilation, capillary leakage
Disseminated Intravascular Coagulation (DIC); blood coagulation, decreased circulation
Hypotension, shock, death
Capsule – prevent phagocytosis, resist serum killing by C’

9. Virulence Factors: Enterotoxin
Movement of water & ions from tissue to bowel resulting in watery diarrhea
Two types of enterotoxin:
Heat-stable (ST) – activate cGMP
Heat-labile (LT) – activate cAMP
Shiga toxin – inhibit protein synthesis:
Enterohemorrhagic strains of E. coli (EHEC)
Cytotoxic, enterotoxic, neurotoxic
Diarrhea, ulceration of G.I. tract
Enteroaggregative toxin - produced by E. coli (EAEC), causes watery diarrhea

10. Virulence Factors Hemolysin – cytotoxin to RBC’s, leukocytes
Enterochelin - capture iron
Outer membrane proteins – attachment, initiate endocytosis for cell invasion
Adhesions – pili, fimbriae, non-fimbrial factors for host cell (GI, urinary, CNS) attachment; antibodies to adhesions may protect from colonization

11. Sites of Infection Central Nervous System (CNS)
Escherichia
Lower Respiratory Tract (LRT)
Klebsiella
Enterobacter
Bloodstream
Salmonella

12. Sites of Infection Gastrointestinal (GI) Tract Urinary Tract (UT)
Salmonella
Shigella
Yersinia
Escherichia
Urinary Tract (UT)
Proteus
Klebsiella
Providencia

13. Escherichia coli
Normal inhabitant G.I. tract, present in water, vegetation
Various forms of gastroenteritis
Major cause of:
Urinary tract infection
Neonatal meningitis
Septicemia
Transmission:
Endogenous spread in susceptible patient
Ingest contaminated food or water
Nosocomial infection

14. Escherichia coli: Biochemical Test ID
May be hemolytic on CBA, more common in pathogenic strains
Key Test:
TSI = A/A + gas
LIA = K/K
IMViC = (++--)

15. Escherichia coli: Infections
Neonatal Meningitis - leading cause, along with Strep Gp. B
Septicemia - GU infection or own GI NF, high mortality
Urinary Tract Infection – leading cause, by own NF:
acute cystitis (bladder infection)
pyelonephritis (kidney infection)

16. Escherichia coli: Gastroenteritis
ETEC (Enterotoxigenic E. coli) – infant diarrhea, Traveler’s diarrhea
EPEC (Enteropathogenic E. coli ) – infant diarrhea
EAEC (Enteroaggregative E. coli) – chronic diarrhea in children
EIEC (Enteroinvasive E. coli) – dysentery in children and adults
EHEC (Enterohemorrhagic E. coli) – hemorrhagic colitis, hemolytic uremic syndrome

17. ETEC (Enterotoxigenic E. coli)
Traveler’s diarrhea
Diarrhea of children in developing countries
These strains rare in U.S.
MO attaches to intestinal mucosa, liberates enterotoxin
Disease characterized:
Watery diarrhea
Nausea
Abdominal cramps
Low-grade fever for 1-5 days
Transmission via contaminated food or water

18. EPEC (Enteropathogenic E. coli )
Bundle forming pili attachment intestinal mucosa
Effacement of microvilli, exact pathogenesis unclear
Diarrhea, large amounts mucous, no blood or pus, vomiting, malaise, low grade fever
Outbreaks in nurseries and day care centers

19. EAEC (Enteroaggregative E. coli)
Bacteria associated autoagglutinins cause aggregation in “stacked-brick” arrangement at cell surface of mucus biofilm
Process mediated by bundle-forming pili (BFP)
MO attach and liberate cytotoxin
Symptoms include watery diarrhea, vomiting, occasional abdominal pain, dehydration >14 days
Chronic diarrhea and growth retardation of children in developing countries

20. EIEC (Enteroinvasive E. coli)
MO attaches to intestinal mucosa; direct penetration, invasion of intestinal cells, destruction of intestinal mucosa
Lateral movement of MO from one cell to adjacent cells
Symptoms include fever, severe abdominal cramps, malaise, watery diarrhea, followed by scanty stools containing blood, mucus, leukocytes and pus
Person to person transmission via fecal-oral route

21. EHEC (Enterohemorrhagic E. coli)
Attach to intestinal mucosa, liberates Shiga toxin, also termed Verotoxin (cytopathic to Vero monkey kidney cell culture)
Watery diarrhea, progress to bloody diarrhea without pus, crampy abdominal pain, ±low-grade fever
May progress to hemolytic uremic syndrome (HUS):
Anemia, kidney failure
Highly fatal - infants (<5 yrs.), elderly
By E. coli O157:H7 serotype
Epidemics traced to consumption of undercooked beef, unpasteurized juice

22. Summary: E.coli Gastroenteritis

23. E. coli: Treatment and Control
Susceptible to variety of antibiotics
Drug resistant strains increasing, need susceptibility testing
Hospital infection control important
Education to improve hygiene, hand washing

24. Klebsiella: ID NF of GI tract, potential pathogen in other sites
TSI = A/A + gas
LIA = K/K
Urea (+)
Citrate (+)
MR(-), VP(+)
Motility (–)

25. Klebsiella: Infections
Virulence factors:
Capsule
Adhesions
Iron capturing ability
Clinical significance:
Pneumonia - mostly immunocompromised hosts; permanent lung damage frequent occurrence (rare in other bacterial pneumonia)
Major cause of nosocomial infection – septicemia, meningitis

26. Proteus: ID NF of GI tract Motile, with swarming on CBA
TSI = K/A + H2S (similar to Salmonella)
LIA = R/A (lysine deamination)
PAD = (+) (phenylalanine deamination)
Urea = strongly (+) for Proteus
Indole – only P. mirabilis is (-)

27. Proteus: Infections Virulence factors Clinical Significance
Urease – ammonia produced may damage epithelial cells of UT
Clinical Significance
UT infections; also pneumonia, septicemia, wound infections

28. Enterobacter: ID & Infections
NF of GI tract
TSI = A/A
LIA = K/K
IMViC = (--++)
Clinical significance:
Nosocomial infections
Bacteremia in burn patients

29. Serratia: ID & Infections
Free-living saprophyte
TSI = K/A
LIA = K/K
Citrate (+)
Urea (±)
Has been found in RT and UT infections
Resistant to many antibiotics

30. Edwardsiella: ID & Infections
TSI = K/A + gas, H2S
LIA = K/K +H2S
Urea(–)
Citrate(–)
Indole(+)
Clinical significance – causes GI disease in tropical and subtropical countries

31. Citrobacter: ID & Infections
TSI = K/A or A/A both + gas, H2S
LIA = K/A + H2S
Citrate (+)
Urea usually (+)
Opportunistic pathogen causing urinary tract or respiratory tract infections; occasionally wound infections, osteomyelitis, endocarditis, meningitis

32. Lab: Enterobacteriaceae I Group Unknowns
TSI LIA
Escherichia A/A K/K
Shigella K/A K/A
Enterobacter A/A K/K
Klebsiella A/A K/K

33. Class Assignment Textbook Reading: Chapter 19 Enterobacteriaceae
Key Terms
Learning Assessment Questions

34. Case Study 3 -Enterobacteriaceae
A 25-year-old previously healthy woman came to the emergency room for the evaluation of bloody diarrhea and diffuse abdominal pain of 24 hours’ duration.
She complained of nausea and had vomited twice.
She reported no history of inflammatory bowel disease, previous diarrhea, or contact with other people with diarrhea.

35. Case Study 3
The symptoms began 24 hours after she had eaten an undercooked hamburger at a local fast food restaurant.
Rectal examination revealed watery stool with gross blood.
Sigmoidoscopy showed diffuse mucosal erythema and petechiae with a modest exudation but no ulceration or pseudomembranes.

36. Case Study 3 - Questions
1. Name four genera of Enterobacteriaceae that can cause gastrointestinal disease. Name two genera that can cause hemolytic colitis.
2. What virulence factor mediates this disease?
3. Name the five groups of E. coli that can cause gastroenteritis. What is characteristic of each group of organisms?
4. Differentiate between disease caused by S. typhi and that caused by S. sonnei.

37. Lecture Exam I Thursday, Feb. 2, 2012
Introduction thru Enterobacteriaceae
Lecture, Reading (Chap. 14, 15, 17, 19), Key Terms, Learning assessment Questions, Case Study 1,2,3
Exam Format:
Multiple Choice
Terms
True/False Statements
Short Essay
Review, Review, Review!