Effect of sub-inhibitory concentrations of cefepime on biofilm formation by .

This study investigated the effect of cefepime at sub-minimum inhibitory concentrations (sub-MICs) on in vitro biofilm formation (BF) by clinical isolates of . The effect of cefepime at sub-MIC levels (½-/ MIC) on in vitro BF by six clinical isolates of was phenotypically assessed following 24 and 48 h of challenge using the tissue culture plate (TCP) assay. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to observe the change in expression of three biofilm-related genes, namely, a protease-encoding gene (), fimbrial protein-encoding gene (), and alginate-encoding gene (), in a weak biofilm-producing strain of following 24 and 48 h of challenge with sub-MICs of cefepime. The BF morphology in response to cefepime was imaged using scanning electron microscopy (SEM). The TCP assay showed strain-, time-, and concentration-dependent changes in in vitro BF in following challenge with sub-MICs of cefepime, with a profound increase in strains with inherently no or weak biofilm-producing ability. RT-PCR revealed time-dependent upregulation in the expression of the investigated genes following challenge with ½ and ¼ MIC levels, as confirmed by SEM. Cefepime at sub-MICs could upregulate the expression of BF-related genes and enhance BF by clinical isolates.