Disodium edetate as a conjugation inhibitor: A novel approach to curb growing conjugal transfer of vanA in gram-positive bacteria

Abstract

ObjectiveThe aim of the present study was to identify the vanA gene among clinical isolates of vancomycin-resistant Staphylococcus aureus (VRSA). Thereafter, transfer of vanA gene through conjugation from vanA positive VRSA to a vancomycin-sensitive S. aureus was evaluated. Next, we examined the effect of various concentrations of chemicals including ethylenediaminetetraacetic acid (disodium edetate), ethylene glycol tetraacetic acid (EGTA) and boric acid on conjugation. MethodsA total of fourteen clinical isolates of VRSA were analyzed for the presence of vanA gene using previously reported primer by polymerase chain reaction (PCR). The vanA positive isolate of VRSA served as donor and vancomycin-sensitive S. aureus (vanA negative) served as recipient. Conjugation was carried out according to the broth mating method in the absence and presence of various concentrations of chemicals. ResultsThe vanA gene was detected in eight of the clinical isolates of VRSA. Findings of our study revealed that vanA gene was successfully transferred in-vitro from VRSA donor to vancomycin-sensitive recipient S. aureus by a broth making procedure suggesting possibility of horizontal gene transfer (HGT). Of the evaluated chemicals on conjugation, disodium edetate and EGTA found to be inhibiting the conjugal transfer of vanA gene from donor to recipient. Interestingly, it was observed that disodium edetate at a concentration of 10 mM and above strongly inhibited conjugal transfer of vanA gene from donor to recipient while EGTA inhibited the same at 120 mM. However, boric acid failed to prevent conjugal transfer of vanA gene from donor to recipient. ConclusionBacteria transfer antibiotic resistance from one gram-positive species of bacteria to other bacterial species and thus generating multi-drug resistant bacterial strains. From above study, it can be conclude that disodium edetate at 10 mM and above exhibited a potential effect on the inhibition of transfer of vancomycin resistant gene vanA from vancomycin-resistant S. aureus to vancomycin-sensitive S. aureus. Therefore, the inhibition of conjugation process by 10 mM EDTA can be potentially a novel approach to combat spreading of antibiotic resistant gene.