Bacteriology

Question 1

what hair/skin samples can be tested for bacteria? how should these samples be taken?

Answer 1

impression and direct smears
swabs
concentrated urine sediment

taken from the affected site
- asap following clinical signs
collected as aseptically as possible
collected before any treatment
- test to tailor antibiotics

Question 2

how do you culture a sample?

Answer 2

label a petri dish
- date, sample, agar type, incubation, temperature and initials

sterilise loop wire in Bunsen burner flame
- allow to cool then pick up some sample

smear sample on one side of the plate
- creates a well
- then resterilise loop

make 3-4 strokes (same direction) away from the well
- don’t break medium
- continue around the plate - sterilising between each group

Question 3

what conditions are needed for bacteria culturing?

Answer 3

nutrients and moitsure
- provided by agar

temp to encourage growth
- bacteria dependent

neutral pH - for most
- stomach bacteria need acidic settings

+/- oxygen
- obligate aerobes need oxygen
- obligate anaerobes need no oxygen
- facultative anaerobes can grow with or without

Question 4

how to tell the difference between positive and negative gram bacteria?

Answer 4

gram-negative = pink
- less dye absorbed

gram-positive = purple
- more dye absorbed

Question 5

what are the different types of bacteria?

Answer 5

spherical - cocci
rod - bacilli
spiral - spirilla
comma - vibrios
corkscrew - spirochaetes