Efficacy of Benzylkonium and Clorhexidine against Clinical Isolates of Pseudomonas Sp. from Dhaka, Bangladesh

The opportunistic pathogen Pseudomonas aeruginosa has been recognized as a major cause of nosocomial infection due to resistance to multiple classes of antibiotics. This study reports presence of carbapenem resistance genes in clinical Pseudomonas isolates from Dhaka, Bangladesh, as well as their resistance to some common disinfectants (benzylkonium chloride and chlorhexidine gluconate). Twenty three samples were collected from two hospitals and one diagnostic center from different locations in Dhaka city. Among these, 16 isolates were identified as Pseudomonas sp. from growth on Cetrimide Agar, standard biochemical tests (catalase, oxidase and triple sugar iron, urea, Sulphur Indole Motility medium, Lysine Iron Agar, Methyl Red-Voges Proskaeur medium, nitrate, citrate) and IasL/R-gene targeted PCR. Molecular characterization revealed three of the isolates contained 2.3kb to 2.5 kb plasmids. The genome of 6 isolates contained blaGIM gene encoding metallo-beta-lactamase variant (German), but none of isolates were resistant against imipenem group of antibiotics (meropenem, gentamicin, cefixime, imipenem). Therefore the isolates are genetically potent to resist antibiotics belonging to imipenem group, but are still sensitive to the antibiotics in culture. 3% Benzylkonium chloride and 0.5% chlorhexidine gluconate has slightly synergistic effect in inhibiting Pseudomonas sp. in representative isolates as their Fractional Inhibitory Concentration Index value ranges between 0.22 and 0.5. Taken together, Pseudomonas sp. isolates harboring potential virulent genes and imipenem-resistance genes could be inhibited more effectively in vitro if more than one suitable disinfectants are applied combinedly.