Question

How many types of DNA in Bacteria and what type do we extract for antimicrobial resistance ?

Answer 1

DNA IN BACTERIA

-Bacteria has two types of DNA: -

1.Chromosomal DNA - Single molecule of double stranded, circular DNA in the bacterial nuclei

2.Extrachromosomal DNA – Plasmid or Episome found in cytoplasm (a bacterial cell may have a single plasmid or even up to > 40 plasmids)

-Plasmids also contain double stranded circular DNA which is in free state. These may integrate with the chromosomal DNA and such a form is called Episome. Plasmids are not essential for life of a bacteria. They confer some properties to the bacteria like antimicrobial resistance, toxigenicity, etc

ANTIMICROBIAL RESISTANCE

-This is of two types:

1.Intrinsic resistance – a bacteria’s innate ability to resist the action of a particular antibiotic class

2.Acquired Resistance – a bacteria acquires drug resistance by:

   a) Mutation – chromosomal mutation

   b) Gene transfer – by Conjugation (most important) or by Transduction

-Conjugation is the most important method of drug resistance and it occur by transfer of Plasmids called Resistance Factor (R Factor)

-Antimicrobial susceptibility Testing can be done by various methods like:

a) Disk diffusion Methods

b) Dilution Tests

c) Respirometer Test

d) Automated Tests like VITEK 2, MicroScan, etc

e) Molecular Methods like PCR (Polymerase Chain Reaction)