microbio exam Flashcards
What species are often found on the skin?
Propionibacterium
Staphylococcus
Methylophilus
How is mannitol salt agar selective and differential
Selective- has high salt concentration, salt loving species are able to grow
differential- bacteria capable of fermenting mannitol change the medium from red to yellow
Why is mannitol salt agar selective media for normal skin microbiota
many organisms on the skin are resistant to high salt conditions so they will grow on mannitol
How is mannitol salt agar differential for staph aureus
Staph aureus ferments mannitol and will change the medium from red to yellow. Coagulase postiive staph will will ferment mannitol while coagulase negative will not
What two groups do a catalase test differentiate
Catalase positive- staph and micro
catalase negative- strepto and entero
What characteristics can characterize staph aureus
positive coagulase, forms golden yellow colonies on agar, gram positive
What characteristics characterize s pyogeness
beta hemolytic, produces streptolysins, are catalase negative
What characteristics characterize s pneumoniae
alpha hemolytic, optochin sensitive
bile soluble
How are blood agar and hemolytic reactions used to differentiate streptococcal species
No change around the inoculation usually indicates gamma hemoylsis
Green and cloudy inoculum usually indicates alpha (strept)
minimal green change is usually beta and is pathogenic
are streptococci gram pos or neg and catalase neg or pos
gram positive
catalase negative
where on the body is staphylococci
arm or finger
where would one find streptococci
warmer wetter places like the armpit
