Phenotypic ESBL and non-phenotypic ESBL isolates ofKlebsiella pneumoniaeexhibit differing responses to induced antimicrobials resistance and subsequent antibiotic cross-resistance

Abstract

AbstractAimTo investigate the effect of adapting Klebsiella pneumoniae clinical isolates harboring ESBL genes to cetrimide (CT) in terms of subsequent cross-resistance to other biocides and antibiotics, and to investigate changes to virulence markers, such as biofilm formation and efflux activity. The changes between phenotypic extended spectrum β-lactamases (pESBL) expressing isolates and non-phenotypic ESBL (npESBL) isolates was compared.Methods and resultsKl. pneumoniae isolates (14 pESBL and 17 npESBL) were adapted to increasing concentrations of CT, until 4 × MIC was reached. The MIC of the adapted isolates was tested against chloroxylenol (CX) and chlorhexidine. Disk diffusion techniques were used to determine the susceptibility of the isolates to different antibiotics. Biofilm formation was assessed for the isolates using the crystal violet method and efflux pump activity was studied using the ethidium bromide assay. After CT adaptation, 100% of npESBL isolates and 85.7% of pESBL isolates showed increase in CT MIC after CT adaptation. While 41.2% of npESBL and 57.1% of the pESBL isolates showed a cross-resistance with chlorhexidine. CT adaptation resulted in a significant decrease in the susceptibility of npESBL isolates to aztreonam and cefotaxime compared to pESBL isolates, which could be linked to the increase in efflux activity of npESBL compared to pESBL. Biofilm formation was significantly increased after CT adaptation regardless of the type of isolate.ConclusionsThe extensive use of biocides in the environment can induce cross-resistance to other biocides and antibiotics, and can increase the ability of bacteria to form biofilms. The response of bacteria to biocide adaptation differs between pESBL and npESBL isolates, although the effect is strain specific.