Effect of polymyxin resistance (pmr) on biofilm formation of Cronobacter sakazakii.

Cronobacter sakazakii (C.sakazakii) has been identified as a wide-spread conditioned pathogen associated with series of serious illnesses, such as neonatal meningitis, enterocolitis, bacteremia or sepsis. As food safety is concerned, microbial biofilm has been considered to be a potential source of food contamination. The current study aims to investigate the ability of biofilm formation of two C. sakazakii strains (wild type BAA 894 and pmrA mutant). Crystal violet (CV), XTT (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino carbonyl)-2H-(tetrazolium hydroxide)] assays, and scanning electron microscopy (SEM) are performed on different time points during biofilm formation of C. sakazakii strains. Furthermore, RNA-seq strategy is utilized and the transcriptome data is analyzed to study the expression of genes related to biofilm formation along with whole genome sequencing. For biomass, in the first 24 h, pmrA mutant produced approximately 5 times than wildtype. However, the wild type exhibited more biomass than pmrA mutant during the post maturation stage (7-14 d). In addition, the wildtype showed higher viability than pmrA mutant during the whole biofilm formation. This study represents the first evidence on the biofilm formation of C. sakazakii pmrA mutant, which may further aid in the prevention and control for the food contamination caused by C. sakazakii.