Antibiotic resistance and ndvB gene expression among biofilm producing Pseudomonas aeruoginosa isolates
A novel antibiotic resistant mechanism among biofilms is glucan-mediated sequestration in which ndvB gene encodes a glucosyltransferase involved in the formation of this glucans. We studied the biofilm formation and antibiotic susceptibility pattern of P. aeruginosa isolated from clinical samples, and measured the expression of ndvB gene among biofilm forming isolates and their planktonic counterparts. The study was conducted on 92 P. aeruginosa isolates. Biofilm was measured using tissue culture plate method. Antibiotic susceptibility of biofilm positive isolates and planktonic counterparts for ciprofloxacin, tobramycin and gentamycin was tested using tube microdilution method. Expression of ndvB gene was measured using Syper green real time PCR. We found that 44 isolates (47.8%) of P. aeruginosa were biofilm positive. The biofilm formation was high among urine, endotracheal tube aspirate and burn isolates compared to isolates of wound specimens, with statistically nonsignificant differences. None of biofilm forming isolates was susceptible to the 3 antibiotics compared to the presence of susceptible isolates among the planktonic counterpart (18/40.9% for ciprofloxacin, 12/27.3% for tobramycin and 13/29.5% for gentamycin). Expression of ndvB gene was significantly high in biofilm isolates than their corresponding counterpart, with significant correlations with minimal biofilm inhibitory concentration (MBIC) values of cibrofloxacin (r=+ 0.65, p< 0.05 ), tobramycin (r= + 0.54 p< 0.05 ) and gentamycin (r=+ 0.77, p< 0.001 ).From this study we concluded that biofilm formation is an important character of P. aeruginosa that is a main cause of antibiotic resistance especially in isolates from catheterized urine , wound and endotracheal tube aspirate. NdvB gene expression is a mechanism of resistance to antibiotics in P. aeruginosa biofilms.
Keywords: P. aeruginosa, biofilm, antibiotic resistance and ndvB gene