What are the advantages of i Liquid culture broth ii Pour Pl

What are the advantages of i) Liquid culture (broth) ii) Pour Plate iii) Streak Plate iv) Slants Describe the basis for selectivity of EMB agar Mac Con key agar and mannitol Salt agar. Aurine with UTI (Urinary track infection) should be plated on MacConkey Agar. Why?

Solution

Advantages of 1.) It can easily identify the type of bacteria on the basis of oxygen consumption. Just below the surface of broth only obligate aerobic bacteria and at bottom of test tube only obligate anareobic bacteria will grow, facultaive and aerotolerant will be through out thebroth in test tube, however facultative will have little bit higer density near surface.

Used to identify the motility of bateria for example if bacteria have falgella then whole broth will be cloudy.

2) Pour plate: a) Easy for quantification b) no need of spreader c) if bacteria will grow inside the agar then they are anareobi aand if they form colony on surface that indicates they need oxygen for their survival (aerobic)

3) streak plate: used for qualitative studies and bacteria can be isolated in distinct colonies.

4) Slant: a) provide more surface arear for growth of bacteria or plant. b)provide bacteria storage for extended peroid, probability of contamination is less.

Question 9. EMB agar: Selective for gram negative strains. Stains used re eosin and methylene blue which slightly inhibit the growth of gram positive bacteria. Also they can differentiate between lactose fermenting bacteria from those who can\'t ferment lactose

Mac Con key agar: crystal voilet and bile salt present in this agar inhibit the growth of gram positive bacteria and factilitate the growth of gram negative bacteria at nutritional point of view. Lactose fermenting bacteria form colonies in various forms of red because neutral red dye color changes with acidic pH (pH changes with the acid produced by the bacteria during fermentation)

Mannitol salt agar: High concentrtion of salt (NaCl) make it selective for gram positive bacteria. Organisms who can ferment mannitol and result into acid byproduct, they can turn phenol red into yellow in agar.

Question 10) The detection of E coli, enterococci and Roteus sp, is easy on chromogeniccmedium for direct identification, thus MacConkey agar is most suitable as its color changed can be identified easily.

The plates are incubated overnight   (16h, at 37 degree)