Question

Talk specifically about the differential and selective media( MSA and EMB) and also address TSA which would be used as a control. You should discuss how they work, what they assess for: both cellular characteristics and metabolic characteristics. Including figures of pathways.

Answer 1

Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms. The selectivity is accomplished in several ways. For example, organisms that can utilize a given sugar are easily screened by making that sugar the only carbon source in the medium

Differential media are used to differentiate closely related organisms or groups of organisms.

MSA Mannitol salt agar is a selective medium used for the isolation of pathogenic staphylococci. The medium contains mannitol, a phenol red indicator, and 7.5% sodium chloride. The high salt concentration inhibits the growth of most bacteria other than staphylococci.

EMB Eosin methylene blue agar is a differential medium used for the detection and isolation of Gram-negative intestinal pathogens. A combination of eosin and methylene blue is used as an indicator and allows differentiation between organisms that ferment lactose and those that do not. Saccharose is also included in the medium because certain members of the Enterobacteria or coliform group ferment saccharose more readily than they ferment lactose.

TSA  Tryptic Soy Agar (TSA), is recommended for use as a general growth medium for the detection and enumeration of microorganisms from non-clinical samples (except G60, G60BX, and J330) as specified by the United States Pharmacopoeia

(TSA) is a solid mediumrecommended for use in qualitative procedures for the isolation and cultivation of a wide variety of organisms. Tryptic Soy Agar slants may be used to cultivate, store, and ship bacterial cultures.

WORK

1. Obtain or pour plate of specified type of selective or differential media

2. Inoculate plate using a loop, swab or hockey stick.

3. Incubate 24-48 hours at optimal growth temperature of organism

4. Observe plates for appropriate reactions

CAN ANSWER FIRST FOUR ONLY THIS IS WHAT WE HAVE BEEN INSTRUCTED TO DO