Transmission of drug resistance was first observed in (AIIMS May 2012)
a. This extrachromosomal mechanism of drug resistance was first reported by Japanese workers (1959) investigating the sudden increase in infections caused by the Shigella stains, resistant simultaneously to Sulphonamides, Streptomycin, Chloramphenicol and Tetracycline.
b. Resistance is plasmid mediated and is transferred by conjugation.