Multiple drug resistance is transferred through:

Conjugation Sexual contact through the formation of a bridge or sex pilus is common among gram-negative bacilli of the same or another species. This may involve chromosomal or extrachromosomal (plasmid) DNA. The gene carrying the &;resistance&; or &;R&; factor is transferred onlv if another &;resistance transfer factor&; (F) is also present. Conjugation frequently occurs in the colon where large variety of gram-negative bacilli come in close contact. Even nonpathogenic organisms may transfer R factor to pathogenic organisms, which may become widespread by contamination of food or water. Chloramphenicol resistance of typhoid bacilli, streptomycin resistance of E. coli, penicillin resistance of Haemophilus and gonococci and many others have been traced to this mechanism. Concomitant acquisition of multidrug resistance has ocurred by conjugation. Thus, this is a very impoant Mechanism of horizontal transmission of resistance. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:671