Enterobacteriaceae

E. coli

• Primary marker for fecal contamination in water

Disease Association

• Most common cause of nosocomial infections

Meningitis/sepsis-associated E. coli

Infection

• Meningitis

Virulence Factor

• K1 antigen – identical capsule to N. meningitis

Enteropathogenic E. coli (EPEC)

Infection

• Infantile diarrhea
  
  • without blood
  • large amounts of mucus

Virulence Factor

• Adhesive properties
  
  • Pili and intimin
  • no exotoxins.

Enterohemorrhagic E. coli (EHEC) (Serotoxigenic/verotoxigenic)

Infection

• Bloody diarrhea
  
  • NO WBCs
• Associated with
  
  • HUS & TTP

Virulence Factor

• Cytotoxin 
  
  • Verotoxins I & II 
    
    • produces damage to vero cells.
• Most common serotypes – O157:H7

Enterotoxigenic E. coli (ETEC)

Infection

• Traveler’s diarrhea / Montezuma’s revenge
• Watery diarrhea

Virulence Factor

• Cholera-like toxin Heat-labile enterotoxin (LT);
• Heat-stable (ST) toxin

Enteroinvasive E. coli (EIEC)

Infection

• Dysenrery-like / shigella-like infection
• Watery Diarrhea
  
  • With WBC’s

Virulence Factor

• Direct invasion
• HEp-2 cells 
  
  • used to detect invasiveness
  • stacked-brick pattern

Enteroaggregative E. coli (EAEC)

Infection

• Watery diarrhea

Virulence Factor

• Global aggregative regular gene,
  
  • AggR, responsible for cellular adherence

Uropathogenic E. coli (UPEC)

Infection

• MOST COMMON CAUSE OF UTI
• Considered cause of diarrhea in HIV patients.

Virulence Factor

• Pili
  
  • Primary virulence factor to cause UTI
• Cytolysins 
  
  • Kill phagocytes.
• Aerobactin 
  
  • Chelates iron

Citroacter spp.

Disease Association

• Septicemia
• menigitis
• brain abscesses

Description

• C. freundii 
  
  • may harbors inducible AmpC genes
    
    • encode resistance to ampicillin and first-generation cephalosporin
• endocarditis in intravenous drug abusers

Cronobacter sakazakii

Disease Association

• Bacteremia,
• causes neonatal meningitis from powdered infant 
• necrotizing colitis in neonates;

Description

• Produces yellow pigment that is enhanced by incubation @ 25°C

Edwardsiella tarda

Disease Association

• Gastroenteritis

Description

• Associated with harboring fish or turtles

Enterobacter spp

Disease Association

• Healthcare – associated infection (contaminated medical device)

Hafnia alvei

Disease Association

• Gastrointestinal infection

Description

• Motile
• non-lactose fermenter
• DELAYED CITRATE POSITIVE REACTION

Klebsiella pneumoniae (Friedlander’s Bacillus)

Disease Association

• Lobar pneumoniae 
  
  • currant jelly sputum

Description

• K1 capsular – containing Mucoid colonies 
  
  • tends to string

Morganella spp.

Disease Association

• Normal inhabitants of gastrointestinal tract
• neonatal sepsis

Description

• Resembles E.coli in IMVIC patter

Proteus spp.

Disease Association

• Associated with UTI
• P. mirabilis 
  
  • most common isolate
• Causes struvite kidney stones 
  
  • due to urease activity

Description

• Swarming Odor: chocolate cake or burnt chocolate smell
• Swimmers – standard vegetative cells
• Swarmers – hyper flagellated; capable of coordinated movement

Providencia spp.

Disease Association

• Most commonly associated with UTI (P. retgerii) and the feces of children with diarrhea

Description

• P. stuartii – outbreaks in burn units

Serratia spp.

Disease Association

• Colonization and cause of pathogenic infection in healthcare setting

Description

• PRODIGIOSIN – red pigment produced by Serratia.

Salmonella spp.

Disease Association

• Acute gastroenteritis or food poisoning 
• Enteric fever (Typhoid Fever) associated with Typhi & Paratyphi
• Isolated in
  
  • blood (1 – 2 weeks) 
  • urine (3 – 4 weeks) 
  • stool (2 – 3 weeks)

Description

• Diagnosed with Widal’s Test
• Fimbriae – initiates intestinal infection 
• Ability to traverse intestinal mucosa 
• enterotoxin

Shigella spp.

Disease Association

• Bacterial dysentrery 
  
  • Blood 
  • Pus 
  • Mucus

Description

• Non-motile
• low infectious dose (100- 200)

Yersinia pestis

Disease Association

• Plague
• Only species that is transmitted from animals by bite of an insect vector (Xenopsylla cheopis)

Description

• non-motile 
• Grows best @ 25°C – 30°C 
• Colonies: pinpoint @ 24 hrs.
  
  • but resemble those of other Enterobacteriaceae after 48 hrs.
• cauliflower appearance @ 48 hrs in SBA 
• Stalactite pattern in broth culture

Yersinia enterocolitica

Disease Association

• Acute enteritis (enterocolitis) – most common form
• Arthritis & Erythema nodosum – mimics appendicitis

Description

• 8 hrs. incubation @ RT in CIN 
  
  • develops bull’s eye colonies

K. oxytoca

• Associated with antibiotic-associated hemorrhagic colitis
• Indole (+)

K. pneumoniae subsp. Rhinoscleromatis

• Isolated from patient’s with rhinoscleroma

K. pneumoniae subsp. Ozaenae

• Causes atrophic rhinitis 
• Associated with presence of plasmid – mediated ESBLs

K. granulomatis

• Causes donovanosis

Species

• Salmonella enterica
• Salmonella bongori

Salmonella enterica SUBSPECIES

Salmonella enterica seroptypes

• Typhi
• Choleraesuis
• Paratyphi

Other facts

• Causes Typhoid fever   
  
  • Typhi
• Causes Enteric fever
  
  • Choleraesuis 
  • Paratyphi
• Salmonellosis infective dose – 10^6 bacteria
• Development of typhoid fever is 9-14 days
• Gallbladder – Site of CHRONIC CARRIAGE
• Vi antigen – Important in identifying Salmonella Typh

SEROGROUP

First man who isolated Shigella – Kiyoshi Shiga

FORMS OF PLAGUE

• Bubonic / Glandular 
  
  • most common
  • high fever with BUBOES
• Septicemic
• Pneumonic

Y. pseudotuberculosis

• 1° pathogen of rodents
• causes caseous swelling (pseudotubercles) 
• typically looks like plague bacillus

BIPOLAR STAINING 

• Wayson stain 
• Methylene blue