The emerging hypermucoviscous Klebsiella oxytoca poses a major threat to public health and this emerging strain is unique from classic Klebsiella strains by producing increased capsule formation. In this study, a total of 42 Klebsiella species obtained from various diagnostic centers in Tamil Nadu were analyzed for multidrug resistance by performing disc diffusion and minimum inhibitory concentration (MIC), hypermucoviscous phenotype by string test and biofilm formation by crystal violet staining assay. Based on colony morphology and Vitek identification system, it was found that 12/42 (28%) were Klebsiella oxytoca and 30/42 (71%) were found to be Klebsiella pneumoniae. Antibiotic susceptibility testing reveals that 92% were multidrug-resistant (MDR) by the disc diffusion method. All the K. oxytoca (n=12) and K. pneumoniae (n=30) isolates were found to be resistant to colistin by MIC broth dilution. Among the colistin resistant K. oxytoca isolates, 4/12 were found to be hypermucoviscous phenotypically by string test whereas none of the K. pneumoniae were positive for string test and the biofilm forming categories was evaluated. Our study highlights the phenotypic emergence of colistin resistant hypermucoviscous Klebsiella oxytoca which is an emerging nosocomial pathogen among Enterobacteriaceae family and also reveals phenotypic variation in clinical isolates to be explored in molecular level to prevent its spread.

Keywords: Biofilm, colistin, hypermucoviscous, Klebsiella species.