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10 Cards in this Set

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  • Back
1. What are group D streptococci?
1. These are alpha hemolytic bacteria divided into 2 subgroups;
Enterococci(comprised of Enterococcus faecalis and faecium;
Non enterococci comprised of many, including Strep bovis/strep equinus.
List several facts about Enterococcus(faecalis and faecium).
2. They take up residence in the human intestine and are normal bowel flora;
Alpha hemolytic;
grow well in 40% bile or 6.5% NaCl;
Found in urinary/biliary infections;
Can cause SBE;
prey on weak hospitalized patients.
How is Enterococcus treated?
3. Many strains are now resistant to ampicillin and aminoglycosides. Vancomycin has also been used, but appears to be less effective due to new resistance strains(vancomycin resistant enterococcus,VRE).
Enterococcus with this resistance gene alter their cell wall dipeptide d-alanine-d-alanine(target for vancomycin) changing it to d-alanine lactate.
Are there any newer drugs on the horizon for enterococcus/
The pristinomycins(dalfopristin)(Synercid+Quinopristin. These drugs cause occasionally painful arthralgias and venous irritation.
Metronidazole must be used for Clostridium difficile pseudomembranous colitisnstead of vancomycin.
An important unique property is that there is a remarkable association between S. bovis infection and colon cancer. TRUE/FALSE
True. In some series, 50% of people with S. bovis bacteremia have a colonic malignancy. Whether S. bovis is a cause of colon cancer or a marker of the disease is still controversial.
What are some characteristics of Strep. pneumoniae?
It is a major cause of bacterial pneumonia and meningitis in adults, and otitis media in children.
What is the major virulence factor of pneumococcus?
polysaccharide capsule-which protects it from phagocytosis. the capsule is antigenic, and antibodies specific for the capsule can neutralize the pneumococcus. There are however 84 different capsule serotypes, so surviving an infection with this organism only provides immunity to 1 out of 83 possible capsule types.
What are the 2 important lab tests used to diagnose pneumococcus?
1. Quellung reaction
2. Optochin sensitivity.
What is the pneumococcal vaccine(pneumovax)?
it has 25 of the most common capsular polysaccharide antigens. A new heptavalent conjugate vaccine has 7 capsular polysaccharide antigens from serotypes 4, 6B, 9V 14, 18C, 19F and 23F conjugated with a non toxic diptheria toxin protein to increase its immunogenicity.
What is Optochin sensitivity?
Strep pneumoniae is alpha hemolytic, but strep viridans is also alpha hemolytic. To differentiate, a disc impregnated with optochin is placed on the agar dish. The growth of Strep. pneumoniae will be inhibited, while Strep viridans will continue to grow.