Effect of biofilm formation by clinical isolates of on the efflux-mediated resistance to commonly used antibiotics.

AIM

To evaluate the role of biofilm formation on the resistance of () to commonly prescribed antibiotics, the expression rates of resistance genes in biofilm-forming and planktonic cells were compared.

METHODS

A collection of 33 isolates from children and adult patients with chronic infection were taken for the present study. The isolates were screened for biofilm formation ability, as well as for polymerase chain reaction (PCR) reaction with and efflux pump genes. Susceptibilities of the selected strains to antibiotic and differences between susceptibilities of planktonic and biofilm-forming cell populations were determined. Quantitative real-time PCR (qPCR) analysis was performed using gene as a -specific primer, and two efflux pumps-specific primers, and .

RESULTS

The strains were resistant to amoxicillin, metronidazole, and erythromycin, except for one strain, but they were all susceptible to tetracycline. Minimum bactericidal concentrations of antibiotics in the biofilm-forming cells were significantly higher than those of planktonic cells. qPCR demonstrated that the expression of efflux pump genes was significantly higher in the biofilm-forming cells as compared to the planktonic ones.

CONCLUSION

The present work demonstrated an association between biofilm formation and decreased susceptibility to all the antibiotics tested. This decreased susceptibility to antibiotics was associated with enhanced functional activity of two efflux pumps: and .