5 mM of dNTPs, 1.25 μM of each primer and 1.5 U of Taq polymerase (Bangalore Genei). PCR

amplification was carried out on a Eppendorf thermocycler (Germany) with cycling conditions: initial denaturation at 94 °C for 5 min followed by 32 cycles each of denaturation (94 °C for 45 s), annealing (53 °C for 45 s), extension (72 °C Crizotinib chemical structure for 60 s) and final extension (72 °C for 7 min), for the amplification of qnrA, qnrB and qnrS genes. The PCR products were analyzed in 1% (w/v) agarose gel containing 25 μg of ethidium bromide in Tris–EDTA buffer and the gel was photographed under ultraviolet illumination using gel documentation system (Bio-Rad, USA). After electrophoresis, density of PCR product bands were measured by ImageJ software. Susceptibility to various classes of antibiotics were done by two methods: MIC and AST. MIC was determined by the agar dilution method according to the CLSI guidelines.25 The MIC was defined as the lowest concentration of antibiotic that completely inhibited visible bacterial growth. Working solution of each drug was prepared in M–H broth at a concentration ranging from 0 to 2048 μg/ml, and from these working solutions, serial two fold dilutions were made using CAMH (Cation-Adjusted Mueller–Hinton, Himedia, Bombay, India) broth in wells of 96-well plate. E. coli ATCC25922 was used as MIC and AST reference

strain. AST was determined KPT-330 chemical structure by the disk diffusion method as described in CLSI guidelines.15 The test was performed by applying a bacterial inoculum of approximately 1–2 × 108 CFU/ml. The antibiotic discs contained the following antibiotic concentrations: potentox 40 μg cefoperazone plus sulbactam 105 μg, cefepime 30 μg, piperacillin plus tazobactam 110 μg, amoxicillin plus clavulanic acid 30 μg, moxifloxacin 5 μg, levofloxacin 5 μg, amikacin 10 μg, meropenem 10 μg and imipenem 10 μg. All of the discs were obtained from Himedia Laboratories

Pvt. Ltd., Mumbai, India. Interpretation of results were done using the zone of inhibition sizes. Zone sizes were interpreted using standard recommendation of CLSI guidelines. Conjugation experiments were carried out by a broth mating method as described earlier18 using azide resistant E. coli J53AzR as the recipient and qnrB positive E. coli as the donor. E. coli J53AzR crotamiton was kindly gifted by Dr. N.D. Chaurasiya (National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA). Transconjugants were selected on MacConkey agar plates containing sodium azide (100 μg/ml) and streptomycin (100 μg/ml). To assure whether quinolone resistance was co-transferred, colonies were replica-plated on to MacConkey agar plates supplemented with and without ciprofloxacin (0.06 μg/ml). To assess the effect of EDTA disodium and drugs on conjugation, different concentrations of EDTA including 1.0, 3.0, 5.0, 7.0 and 10.