Vancomycin minimal inhibitory concentration from broth microdilution and Etest in respiratory tract samples of patients with ventilation-associated pneumonia.

additive effect on quinolone susceptibility.7 Though Qnr proteins and Aac(60)-Ib-cr only induce low level quinolone resistance, they are known to facilitate selection of resistancemutations in the presence of concentrations of quinolone antibiotics.8 We describe an isolate of K. pneumoniae isolate carrying three plasmid-mediated quinolone-resistant genes (qnrB, qnrS and aac (60)-Ib-cr variant) together with a novel variant of gyrA gene that has not been reported previously. These mechanisms were likely to have contributed individually to the high level ciprofloxacin and levofloxacin resistance.