Influence of subinhibitory-concentration (sub-MIC) Cefetoxime on biofilm formation. SEM study of ESBL-producing Salmonella typhi

Abstract

Objectives: In the present study, we have analyzed ESBL-producing S. typhi’s capability in forming a significant amount of biofilm on plastic and glass surface, and the influence of cefetoxime on biofilm development at subinhibitory (Sub-MIC) concentration. Methods: Nine strains of cefetoxime-mediated ESBL-producing S. typhi were used in the study. S. typhi formed biofilm on plastic and glass materials; it was demonstrated using micro titre plate (MTP) and standard test tube methods. Comparative study of the influence of cefetoxime on biofilm formation in its MIC (128 µg/ml) and at sub-MIC (64 µg/ml) was demonstrated by microtitre plate method. The biofilm production was observed in SEM images, statistical analysis (ANOVA) showed significant increase in cell surface and volume due to the influence of Cefetoxime. Results: Of the nine selected isolates, two S. typhi strains, namely BST 51 and BST 130, produced relatively strong biofilm in the presence of cefetoxime at sub-MIC level (64 µg/ml), comparatively weak biofilm formation at MIC level (128 µg/ml). Typical morphological changes were observed in cefetoxime-resistant strains, S. typhi BST 51 and BST 130, in comparison to cefetoxime-sensitive strain S. typhi BST 63 used as a control. We found an increase in surface and volume of a cell in response to cefetoxime and statistical data (ANOVA) proved that resistant strains were significantly different from control strains. Conclusion: The above study clearly shows that cefetoxime at sub-MIC level efficiently induces biofilm formation and promotes changes in morphology of the cell. J Microbiol Infect Dis 2017; 7(2): 67-75