Gram Pos, Catalase Neg, Aerobic Cocci Flashcards
Lower respiratory tract: normal flora?
No. Typically sterile
Streptococci spp. are _____ ______
facultative anaerobes
Streptococci spp cat? oxidase?
Catalase -
Oxidase -
Which two may require increased CO2 for growth?
S. Pneumoniae and viridans strep
Susceptibility testing is needed for:
Strep pneumoniae and viridans strep
*as a result of antibiotic resistance to PENICILLIN and CEPHALOSPORINS.
Susceptibility testing is not needed for:
Strep pyogenes, Strep agalactiae, Groups C, F, and G
- Penicillin is drug of choice*
- If allergic, erythromycin is drug of choice but requires susceptibility testing as resistance has been discovered.*
Which organisms are considered normal flora?
Strep agalactiae (female genitourinary tract, lower GI)
Lancefield groups C,F, and G (skin, nasopharynx, GI, GU)
Strep pneumoniae (nasopharynx)
Viridans strep (oral cavity, GI, female genital)
Enterococcus (E.faecalis and E. faecium- GI and female GU)
Which organism is not normal flora?
Strep pyogenes
What hemolysis is displayed by Viridans strep?
Alpha hemolysis (green color)
What hemolysis is displayed by Enterococcus spp?
Gamma hemolysis
Which of the Lancefield groups are clinically significant?
Groups A,B,C,D,F, and G
Group A contains group A antigen…..
Who is in group A and hemolysis
Strep pyogenes-beta hemolysis
Who is in group B and hemolysis
Strep agalactiae- beta hemolysis
Who is in group C and hemolysis
S. equisimilis- most common group C in humans
S. zooepidemicus- animal diseases. Humans can get through unpasteurized milk and cheeses
Beta hemolysis
Who is in group D and hemolysis
S. bovis
S. equinus
alpha or gamma hemolysis
What is the hemolysis of Strep pneumoniae?
Alpha
Which strep species is the common cause of dental carries?
Strep mutans
Which strep group is susceptible to Bacitracin?
Group A (S. pyogenes) *Not recommended anymore due to groups C and G also being susceptible.*
Which organism is susceptible to optochin?
S. pneumoniae
What does the bile solubility test detect? Which organism is it diagnostic for? How are positive positive tests indicated by?
It detects amidaae enzyme. Diagnostic for S. pneumoniae. Positive tests are indicated by cell lysis.
Which organisms are PYR +
Group A (S. pyogenes) and Enterococcus spp
Explain the concept of the PYR test
Substrate L-pyrrolidonyl-b-napthlyamide is hydrolyzed by the enzyme pyrrolidonyl arylamidase (PYR) to create beta -napthylamide which changes color when PYR reagent added forming a pink/ red color.
What organisms are ID by the hippurate hydrolysis? How does it work?
Group B Strep, Gardnerella vaginalis, Campylobacter jejuni, and Listeria monocytogenes
Hydrolyzes sodium hippurate due to presence of enzyme hoppuricase forming a purple color.
What organism is differentiated from other strep spp. using the CAMP test?
S. agalactiae
Which organisms are positive when incubated in bile esculin agar?
Group D (S. bovis and Enterococci) *Pos= blackening of the media*
How does the bile esculin agar work?
If pos, organism has the ability to grow in bile and hydrolyze esculin to esculetin which reacts with Fe in the medium forming dark precipitate.
What is the salt tolerance test used for?
To differentiate Enterococci (pos) from Group D Strep (neg).
Broth starts purple. Positive turns yellow or turbid.
How do slide agglutination kits work?
Latex beads are coated with group specific anti-serum, which clump when mixed with a small amount of colony from the specific Strep spp.
What organism has colonies that are gray-white and surrounded by large zones of beta hemolysis?
Strep pyogenes
Which organism is a common pathogen in throat swabs?
Strep pyogenes
*Throat swabs: inoculate to SBAP with SXT (trimethoprim-sulfamethoxazole) which inhibits growth of normal flora.
What are the virulence factors of Strep pyogenes?
Streptolysin O- causes lysis of erythrocytes, leukocytes, and platelets. Oxygen liable. Will see clearing in the subsurface adjacent to the stab marks. Antigenic
Streptolysin S- causes lysis of erythrocytes, leukocytes, and platelets. Oxygen stable. Produces hemolysis on BAP. Non-antigenic.
M protein- Induce antibody formation
Streptococcal pyrogenic exotoxins (SPE’s)- Induce fever and inflammation with release of many immune mediators which can induce shock and organ failure.
What are some diseases from Strep pyogenes?
Necrotizing Fasciitis (flesh eating bacteria)- affects deep subcutaneous tissues; death of muscle, skin, and fat.
Streptococcal Toxic Shock Syndrome induced by SPE’s- Patients are bacterimic and have necrotizing fasciitis.
Acute exudative pharyngitis (strep throat)- complication in children is glomerulonephritis.
Which organism is the leading cause of morbidity and mortality in neonates in the US?
Strep agalactiae
Exposed during birthing process once membranes rupture.
What are pregnant women screened for? What samples are used?
Group B strep. If pos, they’ll receive intravenous antibiotics during labor.
Vaginal and rectal swabs (need both)
Which organism is alpha hemolytic, small gray colonies with central depression that develops with age (doughnut)?
Strep pneumoniae
Which organism is the leading cause of bacterial pneumonia and meningitis?
Strep pneumoniae
Who is most at risk from Strep pneumoniae?
Children under 2 and adults over 65
What is the vaccine for Strep pneumoniae for children called?
PCV 13
What is the vaccine for Strep pneumoniae for the elderly or adults with asthma or who smoke called?
PPSV23
True/ false? Viridans strep are bile esculin pos.
False. They’re neg which differentiates from Enterococcus and Group D Strep.
Viridans strep possess non group ____
Antigens
Enterococcus spp. are resistant to:
Cephalosporins and aminoglycosides
Becoming increasingly resistant to Vancomycin (VRE’s)
Most infections of Enterococcus are:
Hospital aquired UTI’s (nosocomial)
What is the treatment for Enterococcus spp?
Combination of vancomycin and an aminoglycoside.
What does the pyruvate broth differentiate?
E. faecalis (pos) and E. faecium (neg)
Which organism is the only Catalase neg cocci that are vancomycin resistant, PYR and Leucine aminopeptidase test (LAP) neg that produce CO2 from glucose?
Leuconostoc spp.
What is the natural habitat of Leuconostoc spp?
Plants, veggies, and dairy products.
Rarely a pathogen (immunocompromised)
1st considered a contaminant
What are all spp of Leuconostoc resistant to?
Vancomycin
