Staphylococci

Staphylococcus aureus is coagulase positive whereas staphylococcus epidermidis is coagulase negative.
Other coagulase negative staphylococci are S haemolyticus, S saccharolyticus, S hominis, S schleiferi, S lugdunensis and S simulans.

Ref: Textbook of Microbiology and Immunology By Parija, Pages 188-190

Both are catalase positive. This is the incorrect pair: S. aureus is catalase-positive, but S. pyogenes (like all streps) is catalase-negative. This is an important point in diagnosis in the lab. 

Ans. is ‘a’ i.e., Gram – positive cocci

Gram positive bacteria

.    There are 6 classic grain positive bacteria that cause human disease.

.     Of these 2 are cocci

1. Staphylococci
2. Streptococci (including anaerobic peptostreptococci)

.  Other 4 are bacilli

1. Corynebacterium                         3. Clostridium
2. Bacillus                                      4. Listeria

Ans. is ‘c’ i.e., Expression of methicillin resistance in staph aureus increases when it is incubated at 37°C on blood agar

.   Coagulase test is used to differentiate the different species of staphylococci (staph aureus, staph. epidermidis).

Ans. is ‘a’ i.e., Streptococcus; ‘b’ i.e., Staphylococcus aureus; ‘c’ i.e., Candida albicans

Normal Microbial flora or normal commensal flora or indigenous flora

.Normal microbial flora term is used to describe microorganisms that are frequently found in particlar anatomic sites in healthy individuals.

.  Perhaps one of the most important roles of the normal microbial flora is to help prevent infectious disease following exposure to potential microbial pathogens. The normal commensal has the physical advantage of previous occupancy, especially on skin and mucous membrane.

.   The normal flora of the intestine plays an important role in human nutrition and metabolism.

Normal microbial flora of skin –