Antibiotic resistance and its transfer among clinical and nonclinical Klebsiella strains in botanical environments

Abstract

A total of 183 isolates of Klebsiella from drinking water, market vegetables, wood, sawdust, industrial effluents, and human and animal origin were examined for susceptibility to 10 antibacterial agents. Incidence of resistance to two or more antibiotics tested was: 65% of the human clinical isolates, 59% among bovine mastitis, and 24% among the nonclinical isolates. The five different multiple resistance patterns among nonclinically derived Klebsiella were also found among the human and bovine mastitis isolates. Statistical analyses revealed that patterns of resistance among Klebsiella isolates from drinking water, market vegetables, and industrial effluents were highly correlated with each other and with resistance patterns of human clinical isolates. Antibiotic resistance was transferred between Klebsiella growing in two habitat-simulated environments (growing radish plants and aqueous sawdust suspensions). Transconjugants were detected in 5 of 21 and 6 of 21 mating pairs, respectively. Average transconjugants/donor ranged from 10(-3) to 10(-6) in Penassay broth, from 10(-6) to 10(-7) on radish plants, and from 10(-5) to 10(-8) in sawdust suspensions. Although antibiotic resistance transfer under simulated environmental conditions can occur, regrowth of clinical strains is probably the major cause for the widespread occurrence of antibiotic-resistant Klebsiella in the nonclinical environment.