Title 16. MICROBIOLOGICAL CULTURE SENSITIVITY TESTS.pdf ✅

PHARMD GURU Page 3  The working stock disc should be warmed to room temperature, avoid keeping in direct sunlight. ANTIMICROBIAL RESISTANCE:  Antimicrobial resistance can arise in bacteria in several ways.  Microbes acquire resistance after a change in their DNA. Such changes may occur by: a) Genetic mutation i.e. by alteration in the structure of their own DNA. b) Genetic exchange i.e. by acquisition of extra- chromosomal DNA from other bacteria. DRUG RESISTANCE: It refers to unresponsiveness of a micro-organism to an antimicrobial agent. They are of 3 types: 1) Natural resistance 2) Acquired resistance 3) Cross resistance. 1) NATURAL RESISTANCE:  Some microbes have always been resistant to certain AMA.  They lack the metabolic process or the target site which is affected by the particular drug. Ex: a) gram negative bacilli are normally unaffected by Pencillin G b) M.tuberculosis is insensitive to tetracyclines. 2) ACQUIRED RESISTANCE: It is the development of resistance by an organism (which was sensitive before) due to the use of an AMA over a period of time. 3) CROSS RESISTANCE:  Cross-resistance is the tolerance to a usually toxic substance as a result of exposure to a similarly acting substance.  It is a phenomenon affecting e.g. pesticides and antibiotics as an example.
PHARMD GURU Page 4