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Unit 4 Chapter 19
Enterobacteriaceae
Question | Answer |
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key characteristics of the Family Enterobacteriaceae | gram-negative, non-spore-forming, faculatively anaerobic bacilli; can appear as coccobacilli or as straight rods; can produce large mucoid colonies, large moist, gray colonies |
Enterobacteriaceae *virulence factors* | ability to adhere, colonize, produce toxins, and invade tissue; some species harbor plasmids that can provide antimicrobial resistant genes; produce plasmid-mediated extended spectrum β-lactamase |
Enterobacteriaceae *antigenic factors* | O antigen, H antigen, K antigen |
E. coli *colony morphology* | motile, generally possess adhesive fimbriae and sex pili and O, H, and K antigens; usually appears as a lactose-positive colony with a surrounding area of precipitated bile salts on MAC agar, green metallic sheen on EMB, facultatively anaerobic |
E. coli *gram stain results* | gram-negative rods |
E. coli *testing results* | fermentation of glucose, lactose, trehalose, and xylose; production of indole from tryptophan; glucose fermentation by the mixed acid pathway: methyl red positive and Voges-Proskauer-negative; does not produce H2S, DNase, urease, orphenylalanine deaminase |
E. coli *virulence factors* | enteropathogenic, enterotoxigenic, enteroaggreative |
E. coli *epidemiology* | intestinal tract of humans and many other animals |
E. coli *infections* | UTI, infantile diarrhea, hemorrhagic diarrhea, colitis, HUS, dysentry, traveler's diarrhea, persistent pediatric diarrhea, pediatric diarrhea, septicemia and menegitis |
uropathogenic E. coli | widely recognized as most common cause of UTIs in humans |
enteradherent pathogens EPEC, EHEC, EIEC, ETEC | EPEC: pathogenicity islands (infantile diarrhea); EHEC: shinga toxin/ verotoxin (hemorrhagic diarrhea, colitis, HUS); EIEC: invasion (dysentry); ETEC: LT, ST (traveler's diarrhea) |
enteradherent pathogens EAEC and DAEC | EAEC: AAF fimbriae Afa/Dr adhesions, AIDA-1, pathogenicity islands (persistent pediatric diarrhea); DAEC: (pediatric diarrhea, UTIs) |
Klebsiella *colony morphology* | variable motility, grow on Simmons citrate and in potassium cyanide broth, moist mucoid colonies |
Klebsiella *gram stain results* | gram-negative bacilli |
Klebsiella *testing results* | non produce H2S, few hydrolyze urea slowly, mthyl red-negative, Voges-Proskauer-positive, no indole is produced from tryptophan |
Klebsiella *virulence factors* | large polysaccharide capsule |
Klebsiella *epidemiology* | usually found in the GI tract of humans and animals |
Klebsiella *infections* | wound infections, UTIs, liver abscesses, and bacteremia |
Enterobacter, Cronobacter, Pantoea *colony morphology* | resembles Klebsiella on MAC agar, grow on Simmons citrate and in potassium cyanide broth, yellow pigment |
Enterobacter, Cronobacter, Pantoea *gram stain results* | |
Enterobacter, Cronobacter, Pantoea *testing results* | methyl red-negative, Voges-Proskauer-positive, usually produceornithine decarboxylase; Lysine decarboxylase |
Enterobacter, Cronobacter, Pantoea *virulence factors* | produce ornithine decarboxylase |
Enterobacter, Cronobacter, Pantoea *epidemiology* | isolated from human sources such as blood, wounds, and sputum |
Enterobacter, Cronobacter, Pantoea *infections* | meningitis, bacterimia |
Serratia *colony morphology* | red pigment when growing at room temp |
Serratia *gram stain results* | gram-negative rod |
Serratia *testing results* | positive ONPG, positive for sucrose (biogroup 1), raffinose, and ornithine, (biogroup 2) indole-positive |
Serratia *virulence factors* | DNase, highly resistant to antimicrobials |
Serratia *epidemiology* | isolated from human sources |
Serratia *infections* | nosocomial infections of the urinary tract, respiratory tract, bacteremia |
Hafnia *colony morphology* | Motility occurs at 30 degrees C. by peritrichous flagella; Colonies are non-lactose-fermenters and may resemble Salmonellae. Most strains are translucent or colorless; rare strains may produce red or pink colonies on media containing sucrose. |
Hafnia *gram stain results* | gram-negative rod |
Hafnia *testing results* | Oxidase-negative; Catalase-positive; Lysine- and ornithine-decarboxylase-positive; H 2 S (Triple Sugar Iron - TSI)-negative; Urease-negative; Indole-negative; DNase-negative; ONPG-positive; Reduces Nitrate to Nitrite |
Hafnia *virulence factors* | no capsules or spores |
Hafnia *epidemiology* | occurs in man and animals and birds, and in natural environments such as soil, sewage and water; found in clinical specimens, especially from feces, occasionally blood, sputum, urine, and wounds, abscesses, the throat, abdominal cavity and autopsies. |
Hafnia *infections* | H. alvei seem to be opportunistic pathogens which produce infections in patients with underlying illnesses; a possible causative agent of intestinal disorders; no conclusive evidence has been obtained regarding its enteropathogenicity |
Proteus *colony morphology* | produces swarming colonies on SBA |
Proteus *gram stain results* | gram-negative rod |
Proteus *testing results | some are negative for H2S, differentiated by indole and ornithine decarboxylase tests, |
Proteus *virulence factors* | have numerous factors including fimbriae, flagella, outer membrane proteins, lipopolysaccharide, capsule antigen, urease, immunoglobulin A proteases, hemolysins, amino acid deaminases, and, finally, the most characteristic attribute of Proteus |
Proteus *epidemiology* | isolated from urine, wounds, and ear and bacteremic infections |
Proteus *infections* | responsible for 3% of all hospital acquired infections particularly UTIs, causes lower and upper urinary tract infection, |
Morganella *colony morphology* | facultative anaerobes, motile |
Morganella *gram stain results* | Gram-negative bacillus |
Morganella *testing results* | oxidase negative and catalase positive. acid and gas from the metabolism of D-glucose, indole positive, VP negative, MR positive, can be grown in KCN, urease positive, |
Morganella *virulence factors* | enzyme, that is resistant to some urease. While, they are resistant to amoxicillin-clavulanic acid, cephalothin, gentamicin, penicillin, piperacillin, tetracycline, and trimethoprim-sulfomethaxzole. |
Morganella *epidemiology* | intestinal tract of humans and other mammals and reptiles |
Morganella *infections* | endophthalmitis, central nervous system infections, Ludwig’s angina, bacteremia, and urinary tract infection |
Providecia *colony morphology* | All are motile, with peritrichous flagella, |
Providecia *gram stain results* | gram-negative rod |
Providecia *testing results* | oxidatively deaminate phenylalanine hydrolyze urea |
Providecia *virulence factors* | invasive isolates |
Providecia *epidemiology* | The modes of transmission may include nosocomial sources, such as hospital food and equipment, intravenous solutions and human contact through contaminated sk in surfaces. Long-term indwelling catheters are a prime site of colonization and |
Providecia *infections* | UTI |
Edwardsiella *colony morphology* | MacConkey agar they form pale coloured colonies which can become pink on further incubation due to fermentation of lactose which can be late. |
Edwardsiella *gram stain results* | Gram-negative, facultatively anaerobic, rod-shaped bacteria |
Edwardsiella *testing results* | slow or weak fermentation of sugars by this organism. Only glucose and maltose are fermented. It is indole positive, utilise citrate, urease negative. |
Edwardsiella *virulence factors* | non-capsulated, motile, produce hydrogen sulphide in KI medium |
Edwardsiella *epidemiology* | Normal habitat is intestine of cold blooded animals and fresh water. It is mainly pathogenic to water animals |
Edwardsiella *infections* | causes occasional infection in humans. Its pathogenic role is uncertain but it has been isolated from wound, urine, blood and CSF |
Erwinia *colony morphology* | appear as white, smooth colonies; may be domed, shining, mucoid-type colonies with radial striations or appear smooth with entire edges. Craters may form around the colonies on some media. Pigments ranging from cream, pale yellow-light pink. |
Erwinia *gram stain results* | gram-negative rods, pairs or chains |
Erwinia *testing results* | Catalase-positive. PYR-positive. (Pyrrolidonyl-beta-naphthylamide). ONPG-positive (beta-galactosidase). Acid produced from carbohydrates. Oxidase-negative. Nitrates are not reduced. Moeller's-decarboxylase-negative. |
Erwinia *virulence factors* | Type III secretion system (T3SS), the exopolysaccharide (EPS) amylovoran, biofilm formation, and motility |
Erwinia *epidemiology* | major global threat to commercial apple and pear production |
Erwinia *infections* | plant pathogens, are not significant in human infections |
Pectobacterium *colony morphology* | n Logan’s medium and did not produce blue pigmented indigoidine on GYCA medium nor “fried egg” colonies on PDA. |
Pectobacterium *gram stain results* | non-fluorescent, gram-negative, facultative anaerobes |
Pectobacterium *testing results* | oxidase-negative and catalase-positive; did not produce acid from α -methyl glucoside, sorbitol and maltose, nor reducing substances from sucrose, but utilized lactose and trehalose, and did not produce indole or lecithinase. |
Pectobacterium *virulence factors* | type II secretion system (T2SS) , adhesions , metalloproteases , and a type III secretion system (T3SS) |
Pectobacterium *epidemiology* | ubiquitous in soil, wa ter, and atmospheric samples worldwide and can infect species from 24 orders of plants |
Pectobacterium *infection* | soft rot disease |
Citrobacter *colony morphology* | grow well on ordinary media producing smooth, convex, non pigmented 2-3 mm colonies |
Citrobacter *gram stain results* | gram negative bacilli, motile with peritrichous flagella, non-sporing, non-acid fast |
Citrobacter *testing results | indole= + except C.freundii, MR= +, VP = neg, Citrate positive, urease weakly positive, H2S is produced by C.freundii. Mannitol fermentation- positive. Lactose fermentation-positive variable, always produce β-galactosidase (ONPG positive). |
Citrobacter *virulence factors* | endotoxins, O (somatic) and H (flagellar) antigen, capsular antigen, adhesion proteins produced by bacteria. |
Citrobacter *epidemiology* | normal commensals of human gastrointestinal tract |
Citrobacter *infections* | They can cause UTI, infection of gall bladder, middle ear. C.koseri may occasionally cause neonatal meningitis. |
primary intestinal pathogens from the Enterobacteriaceae | Salmonella, Shigella, Yersinia |
Salmonella *colony morphology* | faculatively anaerobic, clear colorless, nonlactose fermenting with black centers |
Salmonella *gram stain results* | gram-negative bacilli |
Salmonella *testing results* | do not ferment lactose; indole negative; Voges-Proskauer negative; phenylalanine deaminase negative; urease negative; produce H2S (except Salmonella Paratyphi A); do not grow with potassium cyanide |
Salmonella *virulence factors* | fimbriae in adherance, ability to transverse intestional mucosa |
Salmonella *epidemiology* | found in cold-blooded animals as well as in rodents and birds |
Salmonella *infections* | acute gastroenteritis (food poisoning); Typhoid fever; Nontyphoidal bacterimia; carrier state following infection |
Shigella *colony morphology* | clear, non-lactose-fermenting |
Shigella *gram stain results* | Gram-negative, nonmotile, nonspore forming, rod-shaped |
Shigella *testing results* | nonmotile; only S. flexneri produce gas from glucose; do not hydrolyze urea; do not produce H2S; do not decarboxylate lysine; |
Shigella *virulence factors* | acid tolerance; effector proteins; the Mxi-Spa T3SS, toxins; motility; adherence; |
Shigella *epidemiology* | humans are reservoir though can be transmitted by flies, fingers, and food or contaminated water |
Shigella *infections* | dysentry; fever watery diarrhea; gastroenteritis; |
Yersinia pestis *colony morphology* | gray-white translucent on BAP and chocolate; may appear opaque and yellow in 48hrs; "fried egg" or "hammered copper" on Ba in older cultures; Clear or white on MAC at 48hrs |
Yersinia pestis *gram stain results* | gram-negative, short plump bacillis |
Yersinia pestis *testing results* | non-motile; catalase positive; oxidase negative; urease negative; indole negative; flocculent or "stalacite" growth in broth |
Yersinia pestis * virulence factors* | encoded with plasmids; codes for phospholipase; codes for a protease, activates plasminogen in human hosts; encode several proteins; adhesion; multiply in macrophages; produce pro-inflammatory cytokines |
Yersinia pestis *epidemiology* | inhalation, flea bites |
Yersinia pestis *infections* | plague, bubonic, gladular, septicemic, and pneumonic |
Yersinia enterocolitica *colony morphology* | motile at 25°C/nonmotile 36°C non-spore-forming, faculatively anaerobic |
Yersinia enterocolitica *gram stain results* | gram-negative coccobacillus |
Yersinia enterocolitica *testing results* | Glucose fermenation without gas production, urea usually positive (about 75%), H2S negative. Lactose negative (but ONPG positive), sucrose and mannnitol positive. |
Yersinia enterocolitica *virulence factors* | some strains can produce small amount of ga |
Yersinia enterocolitica *epidemiology* | zoonotic disease occurring in humans as well as a wide array of animals such as cattle, deer, pigs, and birds. |
Yersinia enterocolitica *infections* | usually lead to mild self-limiting enterocolitis or terminal ileitis in humans |
screening stool cultures for pathogens | |