Enterococci

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When was Enterococci reclassified into the genus Enterococcus?

1984

after ____ incubation, Enterococci forms _____ colonies

24hour; large colonies

How many species does Enterococcus have?

38

Enterococci generally ________________ being engulfed and killed by phagocytic cells

Enterococci generally cannot avoid

Which Enterococcus species are most commonly isolated and clinically important?

Enterococcus faecalis Enterococcus faecium

What is aggregation substance? What is the biological effect?

Hairlike protein embedded in cytoplasmic membrane that facilitates plasmid exchange and binding to epithelial cells

Where is Enterococci found?

Normal flora of human and animal GI tract Common in water sources

What kind of diseases are caused by Enterococci?

UTI wound infections (peritonitis; particularly intraabdominal and usually polymicrobic) bacteremia endocarditis

What is Enterococci associated peritonitis? who are at risk?

abdominal swelling and tenderness after abdominal trauma or surgery patients are typically acutely ill, febrile, and have positive blood cultures

What factors contributes to Enterococci's virulence?

ability to adhere to host surfaces, secrete cytoysins and proteases that causes localized tissue damage, and resist antibiotic treatment

What are the surface adhesins of Enterococci?

aggregation substance enterococcal surface protien carbohydrate adhesins

What does Enterococci's cell wall structure, typical of gram-postive bacteria, allow it to do?

allows Enterococci to survive on environmental surfaces for prolonged periods

What is Enterococci resistant to?

aminoglycosides, beta-lactams, and vancomycin

What kind of Enterococci infections are not treatable with any antibiotics?

antibiotic resistant and infections with many isolates (particularly E. faecium)

What is the mechanism of action of Enterococci in the host?

binds to the cells lining the human intestine and vaginal host tissues via surface adhesin proteins secrete proteins with hemolytic activity (cytolysin) and proteolytic activity (e.g., gelatinase, serine protease).

What is the temperature range in which Enterococci can grow?

broad temperature range of 10 to 45 degree Celsius

What kind of growing environment, regarding oxygen, is required for Enterococci?

can grow aerobically and anaerobically

What is the biological effect of pheromone?

chemo-attractant for neutrophils; may regulate inflammatory reactions

What is the morphology of Enterococci? Similar to which other bacteria?

cocci arranged in pairs and short chains, similar to Streptococcus pneumoniae

What is enterococcal surface protein?

collagen-binding adhesin present in E. faecalis

Where is Enterococci colonized? what causes it to spread?

colonizes the gastrointestinal tracts of humans and animals spreads to other mucosal surfaces if broad spectrum antibiotics eliminate the normal bacterial population

Where are Enterococci found on the human body?

common colonizers of the human intestinal tract

What kind of nutrients does Enterococci require? What can it grow in?

complex nutritional needs can grow in high NaCl concentrations and bile salts

What are the secreted factors of Enterococci?

cytolysin pheromone gelatinase

What does UTI of Enterococci cause? Who are at risk?

dysuria and pyuria most commonly in hospitalized patients with indwelling urinary catheter and receiving broad-spectrum cephalosporin antibiotics

Is Enterococci gram-positive or gram-negative?

gram-positive

How was Enterococci previously classified? Why?

group B streptococci because they possess the group D cell wall antigen, a glycerol teichoic acid that is associated with the cytoplasmic membrane

What is present of the cell wall of Enterococci?

group-specific antigen (group D glycerol teichoic acid)

What kind of media does Enterococci require?

grows readily on common, nonselective media

What does gelatinase do?

hydrolyzes gelatin, collagen, hemoglobin, and other small peptides

What are the clinical presentation of Enterococci associated endocartitis?

infection of the heart endothelium or valves; associated with persistent bacteremia; can present acutely or chronically

Enterococci is either _______ resistant to _________________ or ___________________

inherently resistant to many commonly use antibiotics (e.g., oxacillin, cephalosporins) or have acquired resistance genes (e.g., to aminoglycosides)

What are Enterococci resistant to?

inherently vancomycin resistant (VRE)

What is the Enterococci threshold according to the EPA?

level below 104colonies/100mL

How does most Enterococci infections occur?

most infections from patient's bacterial flora some caused by patient-to-patient spread

What are the factors that make Enterococci resistant?

multiple plasmid and chromosome genes

Who are at increased risk of Enterococci infection?

patients hospitalized for prolonged periods and treated with broad-spectrum antibiotics (particularly cephalosporins, to which enterococci are naturally resistant)

Where can carbohydrate adhesins be found and what does it do?

present in individual bacterium in multiple types; mediate binding to host cells

What is the cytolysin? biological effect?

protein bacteriocin that inhibits growth of gram-positive bacteria (facilitates colonization); induces local tissue damage

How many of the Enterococcus species are important human pathogens?

relatively few species

What is the treatment of serious Enterococci infections?

requires combination of an aminoglycoside with a cell-wall-active antibiotic (penicillin, ampicillin, or vancomycin); newer agents include linezolid, quinupristin/dalfopristin, and selected fluoroquinolones

How can Enterococci be differentiated from related organisms?

simple tests: 1. Catalse negative 2. PYR positive 3. Resistant to bile and optochin

Why are Enterococci typically considered to have a limited potential for causing disease? So when is Enterococci a concern?

they do not have a potent toxin or other well-defined virulence factors; however, life-threatening disease with antibiotic-resistant strains has become a serious problem in hospitalized patients


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