Question | Answer |
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 | |
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