Bacteriology

Mycoplasma

Mycoplasma

Because of their small size and lack of a cell wall, mycoplasmas vary from other bacteria. Mycoplasmas are distinguishable from other bacteria in the Mollicutes (mollis, soft; cutis, skin, in Latin) class by their lack of cell walls in taxonomy. Nocard and Roux isolated Mycoplasma mycoides spp. mycoides from pleuropneumonia in calves in 1898. Pleuropneumonia-like…

Triple Sugar Iron Agar

Triple Sugar Iron Agar

Triple Sugar Iron (TSI) Agar and iron Agar (KIA) from Kligler are useful in the presumptive identification of gram-negative enteric bacteria, especially in the screening for intestinal pathogens. The formulae for TSI agar and KIA are identical except that in addition to glucose and lactose, TSI agar contains sucrose. TSI forms hydrogen sulfide (H2S) and…

Antimicrobial mechanism of action

Antimicrobial mechanism of action

Introduction Clinically effective antimicrobial agents exhibit selective toxicity towards the microbe rather than the host, a feature which distinguishes them from the disinfectants. Selectivity is described in most cases by action on microbial processes or structures which differ from those of mammalian cells. For eg, some agents operate on synthesis of bacterial cell walls (an…

Catalase Test

Catalase Test

PRINCIPLE Bacteria that produce the enzyme catalase break down hydrogen peroxide into water and gaseous oxygen, allowing gas bubbles to escape. Most bacteria can be identified using this test. REAGENTS AND SUPPLIES A.Hydrogen peroxide reagent 30% For Neisseria30 percent H2O2 is highly caustic to the skin, so use caution. If you come into contact with…