Enterococci
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