Enterobacteriaceae PDF

# Enterobacteriaceae ## General Characteristics * Gram-negative bacilli * Aerobic and facultatively anaerobic * Non-spore-forming * Non-motile or peritrichously flagellated * Oxidase-negative * Produce acid fermentatively from glucose * Reduce nitrates to nitrites ## Hospital Acquired Infections...

# Enterobacteriaceae ## General Characteristics * Gram-negative bacilli * Aerobic and facultatively anaerobic * Non-spore-forming * Non-motile or peritrichously flagellated * Oxidase-negative * Produce acid fermentatively from glucose * Reduce nitrates to nitrites ## Hospital Acquired Infections * Antibiotic resistant genera * Citrobacter * Enterobacter * Serratia ## Diarrhea * Shigella spp. * Salmonella spp. * E. coli (enterohemorrhagic [Shiga toxin producing], enterotoxigenic, enteroinvasive, enteropathogenic, enteroadherent) * Yersinia spp. ## Donovanosis * Klebsiella granulomatis ## Virulent Factors * Endotoxins * Lipopolysaccharides * K1 antigen * E. coli causing neonatal meningitis * Capsule * Vi antigen * Salmonella serotype typhi ## Pathogenesis * **Urinary tract, those frequently isolated are:** * E. coli * Proteus mirabilis * Klebsiella pneumoniae * **Pneumonia** * Klebsiella pneumoniae * **Bacteremias** * E. coli * Proteus mirabilis * Klebsiella pneumoniae * **Hospital acquired infections** (antibiotic resistant genera) * Citrobacter, Enterobacter, and Serratia ## Media of Choice * **Eosin Methylene Blue (EMB)** * Lactose fermenter - red or black * Non-fermenter - colorless * **MacConkey** * Lactose fermenter - red * Non-fermenter - colorless * **Xylose Lysine Deoxycholate (XLD)** * Xylose fermenter - yellow * Sucrose fermenter - red * **Hektoen Enteric (HE)** * Lactose fermenter - green, blue - green * Salicin fermenter - yellow-orange * **Salmonella-Shigella (SS)** * Lactose fermenter - red * Non-fermenter - colorless * **Bismuth Sulfite (BS)** * Glucose fermenter - black * **Thiosulfate Citrate Bile Salts Sucrose (TCBS)** * Sucrose fermenter - yellow * Non-Fermenter - colorless ## Biochemical Tests * **Oxidase Test** * Principle: Cytochrome oxidase participates in electron transport and in nitrate metabolism. * Reagent: 1% tetramethyl-p-phenylenediamine dihydrochloride * Positive: dark blue. * Enterobacteriaceae = Oxidase negative. * **Nitrate Reduction** * Principle: The organisms produce nitrate reductase, which converts the nitrate (NO3) to nitrite (NO2). * Nitrite + SULFANILIC ACID = diazonium salt, diazonium salt + alphanaphthylamine = red, water-soluble azo dye (+) * **Triple Sugar Iron Agar Test** * Principle: Determine whether a gram-negative rod utilizes glucose, and lactose or sucrose fermentatively and forms hydrogen sulfide. * **Indole** * Principle: tryptophanase * Reagent: 1% paradimethyaminocinnamaldehyde * Positive: blue within 20 seconds. * **Spot Indole Test** * Principle: determine the presence of the enzyme tryptophanase. * **Indole Production (Tube)** * Reagent: (dimethylamine-benzaldehyde and hydrochloride) * **Methyl Red /Voges Proskauer (MR/VP)** * Principle: Determine the ability of an organism to produce and maintain stable acid end products from glucose fermentation. * **Citrate Utilization Test** * Principle: Using sodium citrate as the sole carbon source and inorganic ammonium salts as the sole nitrogen source. * **H2S Production in SIM** * Principle: Determine the ability to reduce sulfur into H2S. * **Urease Test** * Principle: Detects the enzyme urease. * **Motility test** * Principle: To determine whether an enteric organism is motile. * **Phenylalanine Deaminase** * Principle: Microorganisms that produce phenylalanine deaminase remove the amine (NH2) from phenylalanine. * **Lysine Iron Agar (LIA)** * Principle: Differentiate gram-negative bacilli based on decarboxylation or deamination of lysine and the formation of hydrogen sulfide. * **o-Nitrophenyl-ß-D-Galactopyranoside (ONPG) Test** * Principle: Used to determine the ability of an organism to produce ß-galactosidase * **4-Methylumbelliferyl-ß-D-Glucuronide (MUG) Test** * Principle: Used to presumptively identify various genera of Enterobacteriaceae and verotoxin-producing Escherichia coli. * **Salmonella-Shigella** * Principle: Contains bile salts as its gram-positive bacteriostatic agent; selective for Salmonella species & some strains of Shigella * **Xylose-Lysine Deoxycholate** * Principle: Selective media use to isolate Salmonella and Shigella species from stool and other species containing mix flora. * **TSBS (Thiosulfate citrate bile salts sucrose)** * Principle: More or less use for differentiation of Vibrio instead of Enterobacteriaceae; Vibrio species are differentiated whether they ferment sucrose and not lactose. ## Enterobacteriaceae Chart | Genus | LDC | ODC | ADH | IMVIC | |-----------------|-----|-----|-----|-------| | *Escherichia* | + | + | + | ++-- | | *Klebsiella* | + | + | + | ++-- | | *Proteus* | - | + | + | -+- | | *Serratia* | - | + | + | -++ | | *Citrobacter* | - | + | + | -+- | | *Enterobacter* | + | + | + | -++ | | *Salmonella* | - | + | + | -+- | | *Shigella* | - | - | - | +++ | This is a comparison chart to distinguish between genera in the Enterobacteriaceae family using biochemical tests. The chart provides a guide for differentiating between bacteria based on their biochemical characteristics. The genus *Enterobacter* is positive for lysine decarboxylase while the Genus *Citrobacter* is negative. The Genus *Proteus* is negative for decarboxylase but it is positive for other tests. The Genus *Serratia* is negative for decarboxylase and its IMVIC result is -++. ## Common Enteric Pathogens * **Enterotoxigenic Escherichia coli (ETEC)** * Traveler's diarrhea (Montezuma's revenge) * Profuse watery diarrhea with no blood nor leukocytes and abdominal cramping * The stool looks like rice water just like cholera! * **Enteroinvasive Escherichia coli (EIEC)** * Diarrhea is bloody with white blood cells. * Like shigellosis! * **Enterohemorrhagic Escherichia coli (EHEC)** * Shiga toxin-producing E. coli (STEC) * Verocytotoxin-producing E. coli (VTEC) * This pathotype is the one most commonly heard about in the news in association with foodborne outbreaks. * Hemorrhagic colitis. * Hemolytic uremic syndrome (HUS) * Escherichia coli 0157:H7 * **Enteropathogenic Escherichia coli** * Non-invasive * Produces no toxin * Nosocomial * Watery diarrhea with mucus but no blood * **Klebsiella pneumoniae** * Friendlander's bacillus * Lactose positive mucoid colonies * **E. sakazaki** * Enterobacter * Yellow pigmentation that intensifies at 25C The document also covers other important Enterobacteriaceae genera like *Proteus*, *Shigella*, *Yersinia*, *Hafnia*, *Plesiomonas*, and *Edwardsiella*. These sections provide detailed information on their characteristics, distinctive features, and clinical significance.