9. Family Enterobacteriaceae (I) Flashcards
Microscopic appearance of the family Enterobacteriaceae
Gram-negative bacilli
Oxygen requirements for the family Enterobacteriaceae
Facultative anaerobes
Colony morphology for most Enterobacteriaceae
Large
Gray
Spreading colonies
2 genera of the family Enterobacteriaceae that generally differs in colony morphology
Klebsiella
Enterobacter
Colony morphology of Klebsiella and Enterobacter
Mucoid
Carbohydrate fermented by all Enterobacteriaceae
Glucose
Nitrate reduction characteristics of Enterobacteriaceae
Reduces nitrates to nitrites (with rare exceptions)
Oxidase reaction of Enterobacteriaceae
Oxidase negative
Motility of Enterobacteriaceae
Most are motile by peritrichous flagella
Cell-associated antigens of the family Enterobacteriaceae
O: somatic antigen (heat stable)
K: capsular antigen (heat labile)
H: flagellar antigen (heat labile)
Cell-associated antigen associated with endotoxin release
O
Which cell-associated antigen when present, causes the strains to be more pathogenic?
K
Cell-associated antigen responsible for motility
H
Which cell-associated antigen(s) is/are heat stable?
O
Which cell-associated antigen(s) is/are heat labile?
K
H
Which of the Enterobacteriaceae are primary intestinal pathogens?
Plesiomonas
Salmonella
Shigella
Yersinia enterocolitica
PSSY
Which of the Enterobacteriaceae are opportunistic?
Proteus Providencia Escherichia Morganella Citrobacter Hafnia Edwardsiella Enterobacter Klebsiella Serratia
PPEMCHEEKS
Media used to recover Enterobacteriaceae
MacConkey agar
XLD
Hektoen
Carbohydrate used for initial differentiation of Enterobacteriaceae
Lactose
Food-borne enteric pathogens
Salmonella
E. coli
Campylobacter
Yersinia
SECY
Human to human enteric pathogens
Shigella
Salmonella typhi
Helicobacter pylori
SSH
Water-borne enteric pathogens
Vibrio
Aeromonas
Plesiomonas
VAP
Salmonella heat sensitive antigens for serotyping
H antigens
Salmonella virulence antigens for serotyping
Vi (K) antigens
Salmonella antigens that may mask O antigens
Vi (K) antigens
How to remove Vi (K) antigens so that it will not mask O antigens?
Boiling
Most common illness caused by Salmonella
Gastroenteritis
Salmonella spp. that causes bacteremia/septicemia
Salmonella choleraesuis
Disease caused by S. typhi
Enteric fever: Typhoid fever
Culture(s) used to diagnose S. typhi infection
Blood culture: + during first week
Stool culture: + during second week
Culture(s) used to diagnose gastroenteritis caused by Salmonella
Positive stool cultures
Culture used to diagnose infection with S. choleraesuis
Positive blood culture
Disease caused by S. choleraesuis
Bacteremia/septicemia
Serotyping of Shigella species based on O antigen
A: S. dysenteriae
B: S. flexneri
C: S. boydii
D: S. Sonnei
Which Shigella spp. are physiologically similar?
S. dysenteriae (A)
S. flexneri (B)
S. boydii (C)
How do you differentiate S. sonnei (Group D) from Groups A-C?
Biochemical tests
MOT of Shigella spp.
Fecal-oral route (human to human)
True/False. Shigella spp. are vulnerable to gastric acidity.
False. Shigella spp. are resistant to gastric acids
Toxin by Shigella spp. that causes inflammation and ulcerative lesions
Shiga toxin (cytotoxin)
Lactose ferementation characterictics of Shigella spp.
Lactose negative
TSI characteristics of Shigella spp.
Alkaline/acid
No gas
No H2S
Urease characteristics of Shigella spp.
Urease negative
Most important E. coli
Enterohemorrhagic E. coli (EHEC)
Enterohemorrhagic E. coli is also known as
E. coli O157:H7
Carbohydrates fermented by E. coli
Glucose
Lactose
Xylose
Indole reaction of E. coli
Indole positive
Methyl Red (MR) reaction of E. coli
MR positive
H2S production of E. coli
No H2S
Urease production of E. coli
No urease
Citrate reaction of E. coli
Citrate negative
Media used for E. coli O157:H7
MacConkey with Sorbitol (SMAC)
Colony morphology of E. coli on SMAC
Clear (does not ferment sorbitol)
Lactose fermentation characteristics of Salmonella
Lactose negative
H2S production of Salmonella
H2S positive
The family Enterobacteriaceae is normal flora in the
GI tract
