Multidrug resistant gram-negative bacteria in clinical isolates from Karachi.

A total of 54 gram-negative bacteria obtained from various pathological labs and hospitals of Karachi were screened for their resistance to ampicillin, chloramphenicol, gentamycin, kanamycin, neomycin, streptomycin and tetracycline antibiotics. Of the 54 bacteria, 50 were resistant to one or more antibiotics. Among the resistant bacteria, 13 out of 28 were found to transfer their resistances by conjugation. This indicates that at least 46% of clinical gram-negative bacteria in Karachi possess various types of transferable R plasmids, such as pAK5, pAK9, pAK10, pAK11, pAK12, pAK13, pAK14, pAK15, pAK16, pAK17, pAK18, pAK19, pAK20 and pAK21. The non-conjugative R plasmids included pMT14 and pZ26. Only pAK15 showed 26% segregation even after 20 consecutive transfers in plain broth (spontaneous segregation) whereas only pAK15 and pAK16 showed any significant loss of their markers in curing by acridine orange. The stability of R plasmids is more dangerous from clinical point of view.