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Enterobacteriaceae
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- 1Enterobacteriaceae- gram negative rods
- facultative anaerobes
- many are not pathogenic, but may be opportunists
- many are normal gastrointestinal flora - 2Common infections caused by enterobacteriaceaeUrinary tract infections, wound infections, bacteremia, and gastroenteritis
- 3Media commonly used for enterobacteriaceae- blood agar (as large, dull gray colonies, variable hemolysis)
- isolation on MacConkey (see if bacteria is a lactose fermenter)
- also EMB, HE, XLD - 4Enterobacteriaceae 3 common characteristics- ferment glucose
- reduce nitrate to nitrite
- oxidase negative
- (most are motile and possess flagella) - 5Antigenic determinants- O (somatic or cell wall)
- K (capsule or envelope)
- H (flagella) - 6O(somatic or cell wall) - also known as lipopolysaccharide (LPS), released on cell lysis as endotoxin
- 7K(capsule or envelope) - consist of capsular polysaccharide that surrounds cell wall
- ex. Vi antigen found on Salmonella typhi - 8H(flagella) - found only in motile bacteria, heat labile
- 9Organisms identified serologicallyE. coli, Klebsiella, Shigella, Salmonella
- esp. E. coli 0157:H7 - 10IMViC reactions- set of biochemical tests used for E. sp. identification
- indole, methyl red, Voges-Proskauer, citrate reactions - 11Indole- bacteria has tryptophanase to convert tryptophan to ammonia and indole
- E. coli is positive
- Klebsiella is negative - 12Methyl Red- organism can convert glucose to pyruvic acid
- E. coli is positive
- Klebsiella is negative - 13Voges-Proskauer- organism can convert glucose to acetoin
- E. coli is negative
- Klebsiella is positive - 14Citrate- organism utilizes citrate as its sole source of carbon
- E. coli is negative
- Klebsiella is positive - 15Carbohydrate fermentationlactose, sucrose, mannose, sorbitol, mannitol, trehalose, etc.
- 16TSI agar (triple sugar iron)- tube media used to show if the bacteria utilizes glucose, lactose, and sucrose
- gas and/or hydrogen sulfide producer - 17LIA (lysine iron agar)- determine if organism can deaminate or decarboxylate lysine
- 18TSI and KIA- determines if an organism produces hydrogen sulfide
- 19SIM (sulfide, indole, motility) media- determines if an organism can produce hydrogen sulfide
- determines if bacteria has tryptophanase to convert tryptophan to ammonia and indole
- determines if organism is motile - 20ONPG reaction- test used to look for slow or late lactose fermenters
- Citrobacter is positive - 21Urease test- if organism produces this enzyme it can convert urea into ammonia, carbon dioxide and water
- if positive, urea tube turns hot pink
- Proteus is rapid producer
- Klebsiella is slow producer - 22Motility Test- MIO or SIM
- most enterobacteriaceae are mobile
- except Klebsiella and Shigella - 23Nitrate Reduction Test- determines if the organism can reduce nitrates to nitrite
- 24Positive Nitrate Reduction Test- development of red color after adding reagents A and B
- 25Negative Nitrate Reduction Test- no color change after adding reagents A and B
- development of red after addition of zinc - 26Deaminase Test (PAD)- amino acid (phenylalanine) utilization
- able to deaminate phenylalanine
- produces phenylalanine deaminase
- Proteus, Morganella, and Providencia are positive
- Green color - positive
Yellow color (no change) - negative - 27Decarboxylase Test- amino acid utilization
- lysine, ornithine, and arginine
- if positive, bacteria can break down the respective amino acid
- positive - blue-purple color
- negative - yellow color (no change) - 28DNase Test- tests DNase activity in aerobic bacteria
- Staph. aureus and Serratia marcescens are positive
- positive - pink around colony
- negative - no color change - 29E. coli- pink colonies on Mac (lactose positive)
- green metallic sheen on EMB
- indole +
- methyl red +
- citrate -
- H2S -
- Urea - - 30Klebsiella- most common: K.pneumoniae & K. oxytoca
- pink colonies on Mac (lactose positive)
- non-motile
- production of a capsule - 31opportunistic enterobacteriaceaeEscherichia, Klebsiella, Enterobacter, Pantoea, Serratia, Hafnia, Proteus, Morganella, Providencia, Edwardsiella, Citrobacter
- 32Every Kind Eager Person Secretly Has Plans Making Careless People EngageEscherichia, Klebsiella, Enterobacter, Pantoea, Serratia, Hafnia, Proteus, Morganella, Citrobacter, Providencia, Edwardsiella
- 33Enterobacter- most common: E. aerogenes and E. cloacae
- lactose fermenterP - 34Pantoea- very rarely encountered in lab
- 35Serratia- most common: S. marcescens and S. liquefaciens
- slow lactose fermenter (ONPG +) - 36Hafnia- only H. alvei
- rarely seen in clinical lab
- slow citrate + - 37Proteus- most common: P. vulgaris and P. mirabilis
- lactose negative
- swarming colonies on BAP
- "chocolate cake" smell
- urinary tract infections - 38Morganella- only M. morganii
- urinary tract infection & other body infections
- lactose negative - 39Providencia- most common: P. rettgeri and P. stuartii
- seen in immunocompromised patients & urinary tract infections
- lactose negative - 40Edwardsiella- only E. tarda
- wound infections & septicemia - 41Citrobacter- most common: C. freundii
- lactose fermenter
- urinary tract infections, respiratory infections & endocarditis - 42Urinary tract infections- enterobacteriaceae most common cause
- endogenous infection (normal flora)
- most common type of nosocomial infections - 43Urine culture specimen- first morning, clean catch urine
- 44Urine culture- colony count (# of colonies per ml)
- pre-calibrated loop delivers .001ml to inoculate BAP and Mac
- determine # of different types of bacteria
- ID with antimicrobial susceptibility testing - 45Colony Count- number of colonies per ml of urine
- greater than 100,000 colonies per ml is standard for automatic work up - 46Contamination of urine specimen- 3 or more types of bacteria are seen
- 47Stool specimen- usually plated on combination of plates like BAP, Mac/EMB, HE/XLD/S-S (SSA), and sometimes SMac, CIN, and Campy
- fresh stool or placed in a transport medium - 48GI Infections- caused by pathogenic Enterobacteriaceae
- contaminated food or water - 49E. coli 0157:H7- SMac medium (does not use sorbitol)
- serology testing for definitive answer
- EHEC (Enterohemorrhagic E. coli) - 50Yersinia enterocolitica- CIN agar is used to isolate
- colonies are target shaped
- rarely seen in GI infections
- diarrhea cases in young children - 51Campylobacter agar- selective for Campylobacter jejuni
- 52GI infection enterobacteriaceaeSalmonella, Shigella, Yersinia, and Escherichia coli O157:H7
- 53Salmonella- worst is S. typhi
- most common is gasroenteritis
- most infections are self limiting but can progress to septicemia - 54Salmonella typhi- causes typhoid fever
- serology testing based on O, H, K antigens - 55S- non lactose fermenter (clear on Mac)
- green with black centers on HE
- Motility +
- indole -
- Lysine +
- urease -
- TSI: K/A h2s+ - 56Shigella- lactose negative
- non motile
- green colonies on HE
- red colonies on XLD - 57Shigella speciesA = S. dysenteriae
B = S. flexneri
C = S. boydii
D = S. sonnei - 58—
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- Microbiology Fichas sobre Enterobacteriaceae, creado por Lola McCoy el 25/09/2016.
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- Lola McCoy
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