Level of biofilm production by Staphylococcus aureus isolates is critical for resistance against most but not all antimicrobial drugs

Background and Objective: Staphylococcal biofilms cause a wide range of acute and chronic infections, both in hospital and community settings across the world. This study explores biofilm forming propensity among Staphylococcus aureus clinical isolates from Faisalabad, Pakistan and their association with antimicrobial drug resistance.

Methods: The study was conducted during July to December 2020. The biofilm forming ability of S. aureus isolates was assessed by crystal violet staining in 96 well plates. Antimicrobial susceptibility was determined by disk diffusion method against ten antimicrobials representing whole spectrum of antimicrobial drugs.

Results: All the isolates (n=22) produced biofilm; 14 (63.6%) were strong, and 8 (36.4%) moderate biofilm producers. Comparative data were obtained for moderate and strong biofilm producers. Increased biofilm production did not affect azithromycin, clindamycin and mupirocin. However, stronger biofilm production significantly increased resistant isolates in case of augmentin (23.2%), cefoxitin (17.9%), levofloxacin (26.8%), tetracycline (23.2%), vancomycin (14.3%) and trimethoprim (21.4%).

Conclusions: Our findings indicate that the ability to produce large amount of biofilm is an important factor, and S. aureus isolates with this ability, do not require acquisition of drug resistance genes from other bacteria. Our study also provides a guideline for selection of antimicrobials which are not adversely affected by level of biofilm production by various strains of S. aureus.