Studies on the Epidemiology of Resistance (R) Factors

In a nosocomial outbreak due to multidrug-resistant Klebsiella, resistance (R) factors were found to mediate drug resistance in 90% of the isolates tested. An analysis of Klebsiella isolates and a prospective study of interbacterial transfer of R factors in hospital patients both suggested that environmental selection by antibiotics and colonization of patients with resistant organisms are of far greater epidemiological significance than transfer of R factors in the gastrointestinal tract. The public health implications are discussed.