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Gram Neg Rods

Microbiology

QuestionAnswer
Medically important Gram Negative rod genera Bordetella, Campylobacter, Eikenella, Enterobacteriaceae, Salmonella, Shigella, Yersinia, Haemophilus, Helicobacter pylori, Legionella, Pseudomonas aeruginosa, Vibrio, HACEK group
Gram negative bacillus; 16 species (most associated with human disease) Enterobacteriaceae spp
Most common illnesses caused are gastroenteritis, sepsis, spontaneous abortion Enterobacteriaceae spp
GNR; microaerophilic; this delayed discovery of their importance but is now “exploited” in the lab Campylobacter
Human infection results from ingestion of contaminated food, milk, or water; also fecal/oral route Campylobacter
At risk for Campylobacter jejuni Ingestion of large numbers of organisms or those lacking in gastric acid
GNR: Disease is usually self-limiting but antibiotic therapy is given for severe infections Campylobacter jejuni
First discovered in 1984 and named “dysgonic fermenter” (DF) by the CDC because of its slow growth Capnocytophaga canimorsus
Found in respiratory tract and saliva of human (DF-1) and dogs/cats (DF-2) Capnocytophaga canimorsus
Mild to deadly infection: immunosuppression increases risk (asplenic patients can have severe sepsis Capnocytophaga canimorsus
Discovered in 1960s at CDC; originally given name HB group Eikenella corrodens
GNR; risk of serious complications in patients who are immunocompromised Eikenella corrodens
Most diverse group of medically important gram negative, medium-sized bacilli Enterobacteriaceae
GNR; infection via animal reservoir, human carrier, or endogenous; many are opportunistic, nosocomial Enterobacteriaceae
Only about 20 species account for nearly all infections in this group The Enterobacteriaceae
Ubiquitous (soil, water, vegetation); normal flora of human GI tract Enterobacteriaceae
Transmission via fecal contamination of urethra or catheter use (hospitalized patients E. coli
Five “sub-divisions” of E. coli gastroenteritis Enterotoxigenic; enteropathogenic; enteroadherent; enterohemorrhagic; enteroinvasive
E. coli subdivisions found in small bowel Enterotoxigenic; enteropathogenic; enteroadherent
E. coli subdivisions implicated in disease of large intestine/colon (cause bloody diarrhea) Enterohemorrhagic; enteroinvasive
The only E. coli that occurs with any frequency in US (eventually leads to renal failure) Enterohemorrhagic (H7:157)
Implicated in aspiration pneumonia in chronic alcoholics or gastric bypass patients Klebsiella
Member of Enterobacteriaceae; important cause of nosocomial UTIs Providencia stuartii
GNR; important cause of nosocomial patients, especially neonates, immunocompromised patients Enterobacter spp
The individual serotypes are now written with the serotype name capitalized and not italicized Salmonella
4 possible clinical manifestations of Salmonella Gastroenteritis, Sepsis, Enteric fever (= typhoid), Carrier (asymptomatic dx)
GNR; animal reservoir is mostly responsible for disease transmitted by ingestion of contaminated food (eggs, poultry, dairy products) (large inoculum required for infection) Salmonella
GNR; serotypes that only infect humans and are transmitted by fecal-oral spread (small inoculum required for infection) Salmonella Typhi and Salmonella Paratyphi
4 species/groups of Shigella Dysenteriae (A); flexneri (B); boydii (C); sonnei (D)
GNR; infection common in children (daycare centers) and those in custodial facilities Shigella
GNR; common animal pathogen; humans infrequently infected as result of consuming contaminated food Y. pseudotuberculosis
3 Yersinia spp associated with human disease Y. pestis; Y. enterocolitica; Y. pseudotuberculosis
GNR; species have genes that code for adherence, phagocytic inhibition and inhibition of platelet aggregation Yersinia
GNR; virulence factors include capsule & resistance to serum killing Yersinia pestis
GNR; virulence factors include LPS, endotoxin, polysaccharide capsule Haemophilus
3 organisms most causative of OM Strep pneumo, Moraxella catarrhalis; Haemophilus influenzae
Human GI tract is only reservoir (transmission is likely via fecal-oral route) Helicobacter pylori
Associated with gastritis, PUD, gastric malignancies & enteric disease Helicobacter pylori
GNR; virulence factors: urease, motility, adhesion factor, flagella, LPS Helicobacter pylori
Most important Legionella spp (accounts for 85% of all Legionella infections) L. pneumophilia
GNR found on human skin and mucosa (upper respiratory infections limited to ear and eye) Pseudomonas aeruginosa
Virulence factors: exotoxins, endotoxins, pili, polysaccharide capsule Pseudomonas aeruginosa
GNR; important nosocomial pathogen; antibiotic overuse drives this Pseudomonas aeruginosa
HACEK group Haemophilus aphrophilus; Actinobacillus actinomycetemcomitans; Cardiobacterium hominis; Eikenella corrodens; Kingella kingae
GNR; can cause sub-acute endocarditis in patients with pre-existing heart disease HACEK group
Haemophilus species most commonly associated with disease Haemophilus influenzae
Most prevalent Shigella spp S. sonnei
Causes whooping cough Bordetella pertussis
Comma shaped Gram negative bacillus Enterobacteriaceae spp
GNR; microaerophilic; need small amount of CO2 Campylobacter
Most common cause of bacterial gastroenteritis in USA Campylobacter jejuni
Campylobacter jejuni worldwide distribution Increased incidence in warm weather
Corrodes agar medium Eikenella corrodens
Smells like bleach as it grows Eikenella corrodens
GNR: normal flora of upper respiratory tract of humans Eikenella corrodens
Implicated in bite infections Eikenella corrodens; Capnocytophaga canimorsus
Endocarditis in patients with pre-existing heart disease Eikenella corrodens
Account for 1/3 of all septicemias and 2/3 of all UTIs The Enterobacteriaceae
>40 genera, >150 species Enterobacteriaceae
GNR: grow readily on simple media Enterobacteriaceae
aka “coliforms” or enteric bacteria Enterobacteriaceae
GNR; ferment wide variety of carbohydrates Enterobacteriaceae
No. 1 cause of UTIs (community & nosocomial) E. coli
Women at increased risk of infection due to short urethra E. coli
Infecting strains originate from GI tract E. coli
Strains associated with gastroenteritis subdivided into 5 groups E. coli
GNR: etiologic agent of bacteremia, sepsis, neonatal meningitis E. coli
GNR: numerous virulence factors: adhesins & exotoxins E. coli
GNR Increased resistance to multiple antibiotics is problem E. coli
The only E. coli that is exogenously acquired (traveler’s diarrhea) Enterotoxigenic
Klebsiella virulence factors Endotoxin (LPS), capsule, beta-lactamase, urease
Most important & most commonly isolated Klebsiella spp K. pneumoniae
GNR; causes lobar pneumonia Klebsiella spp
GNR; important nosocomial pathogen Klebsiella spp
Important Proteus species mirabilis vulgaris
GNR; common pathogen in community acquired UTIs Proteus spp
Contribute to renal calculi Proteus spp
“Swarmy” growth on culture media with putrid odor Proteus spp
GNR; produce large amounts of urease Proteus spp
“taxonomic nightmare” Salmonella
GNR; 1 species (enterica) with more than 2500 serotypes Salmonella
Commonly divided into typhoid and nontyphoid serotypes Salmonella
Can colonize nearly any animal Salmonella
GNR; chronic carrier state common Salmonella Typhi and Salmonella Paratyphi
GNR; infections occur worldwide; increased in warmer months Salmonella
GNR; at risk: travelers to SE Asia, Africa, Latin America Salmonella
This genus is actually serologically distinct E.coli Shigella
most prevalent Shigella species Shigella sonnei (D)
GNR; human GI tract is reservoir Shigella
GNR; 11 species (3 are associated with human disease) Yersinia
Etiologic agent of plague Y. pestis
GNR; nfrequent cause of gastroenteritis Y. enterocolitica
GNR; capable of growth at cold temperatures Yersinia enterocolitica
Small GNR (sometimes pleomorphic) Haemophilus
Virulent type B now rarely seen due to vaccine Haemophilus influenzae
At risk: asplenic persons, elderly, unvaccinated children Haemophilus influenzae
Beta-lactamase resistance can be a problem Haemophilus influenzae
Etiologic agent of chancroid (soft chancre) Haemophilus ducreyi
Ulcerative venereal disease Haemophilus ducreyi
Most common in Africa/Asia Haemophilus ducreyi
GNR; beginning to be seen in large urban areas in US Haemophilus ducreyi
Etiologic agent of chancroid (soft chancre) Haemophilus ducreyi
Ulcerative venereal disease Haemophilus ducreyi
Most common in Africa/Asia Haemophilus ducreyi
GNR; beginning to be seen in large urban areas in US Haemophilus ducreyi
Comma shaped GNR Helicobacter pylori
GNR; morphologically similar to Campylobacter Helicobacter pylori
Pleomorphic GN bacteria first discovered in 1976 Legionella
1 genus, 48 species Legionella spp
GNR; fastidious, aquatic saprophyte Legionella
Can parasitize amoebae and replicate in alveolar macrophages Legionella
Can survive for years on biofilms formed on water pipes Legionella
GNR; blue/green color on agar with distinctive odor Pseudomonas aeruginosa
GNR; Can grow in tap water (and DI water) Pseudomonas aeruginosa
At risk: immunosuppressed patients Pseudomonas aeruginosa
Can cause swimmers ear Pseudomonas aeruginosa
GNR; more than 60 species; found commonly in water Vibrio spp
GNR; cause mostly GI disease via contaminated water Vibrio spp
Medically important Vibrio spp V. cholerae; V. parahemolyticus; V. vulnificus
Group of fastidious GNRs that colonize human oropharynx HACEK group
Created by: Abarnard