Overview Of Microbiology And Infectious Disease Introduction Flashcards
How will gram positive bacteria stain?
Purple
How does gram negative bacteria stain
Red
What are the gram positive bacteria in clusters
Staphylococcus
What are the common staphylococci and where are they most commonly found
- Staph aureus
*nasal, skin flora, mucus membranes - S. Epidermidis
*skin flora, mucus membrane - S. Saprophyticus
*genital, perineum flora
How will each straphylococci react to a a coagulate test
+ staph aureus
- s.epidermidis, s, saprophyticus
What are gram positive bacteria in pairs and chains
Streptococci
What are the alpha hemolytic streptococci and where are they found?
- Viridians streptococci
- Strep pneumonia (diplococci)
*colonize in oral cavity, URT
What are the beta hemolytic streptococci and where are they found?
- S. Pyogenes (group A)
- S. Agalactiae (group B)
*GBS vaginal / GI flora
What are y-hemolytic streptococci and where are they found?
- Enterococci (E. Faecalis E. Faecium)
*GI flora
What are the gram positive bacteria bacilli
- Listeria
- Corynebacterium
- Bacillus
What are the gram positive anaerobes
- Peptostreptococcus
- Clostridium spp.
- Propionibacterium
- Lactobacillus
What is the coagulase test used for ?
- Used to differentiate S.aureus from coagulase negative staphylococci
*S. Aureus (+)
*S. epidermidis (-)
*S. Saprophyticus (-)
Wha is MSSA/MSSE?
Methicillin susceptible (staph aureus / epidermidis)
1. Cant destroy structurally resistant B-lactams, and can be neutralized by B-lactamase inhibitors
What is MRSA / MRSE?
Methicillin-resistant
1. Changes in the penicillin binding proteins, the target site of B lactams, coded by the mcA gene
What is MLSb resistant
Macrolide / Lincosamide / Streptogramin B resistant
1. One of macrolide resistance mechanisms in staphylococci is ‘methylation of 23s rRNA’
2. Results in cross-resistance to macrolides, Clindamycin, and type B streptogramin
What is the problem with inducible MLSb resistance?
- Staphylococci with inducible MLSb resistance will be shown as resistant to macrolides but susceptible to Clindamycin
Failure to identify inducible MLSb resistance can lead to what?
- Failure of therapy
How to test for inducible resistance Clindamycin
D Test
1. Used to test S.aureus isolates that appears erythromycin resistant and Clindamycin susceptible during C&S testing
2. + test means the presence of Clindamycin resistance to staph aureus
How to differentiate the streptococci
- Hemolysis on blood agar
*alpha beta, y-hemolytic - Type of cell wall carbohydrates
*A, B, C, D
What are the different type of alpha hemolytic streptococci and how will they look on a blood agar
- Viridians streptococci
*normal mouth flora
*can cause oral/dental infection, endocarditis - S. Pneumonia
*encapsulated virulent
*colonize in the URT
**partial hemolysis
**looks greenish on blood agar
What are the different types of beta hemolytic streptococci and how will it look on a blood agar
- S. Pyogenes (group A strep, GAS)
*virulent - S. Agalactiae (group B strep, GBS)
*female vaginal a/o GI flora
**complete hemolysis
**clear area on red plate
What are the Y-hemolytic streptococci and how will they look on the blood agar
- Enterococci (E. Faecalis MC, E. Faecium LC)
*normal GI flora
*opportunistic tend to be in patients with co-morbidities
*no hemolysis
*blood agar stays red
Which Y-hemolytic streptococci is more severe or resistant
E. Faecalis
*more common
*less resistant
E. Faecium
*less common
*more resistant
What are different organisms of the clostridium spp
- C. Perfringes
*gas gangrene
*cellulitis - C. Difficile
*diarrhea
*colitis
**gram positive anaerobes (use soap and water)
