In vitro biofilm formation by Staphylococcus aureus isolated from wounds of hospital-admitted patients and their association with antimicrobial resistance

Abstract

Introduction

Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) has the propensity to form biofilms, and causes significant mortality and morbidity in the patients with wounds. Our aim was to study the in vitro biofilm-forming ability of S. aureus isolated from wounds of hospitalized patients and their association with antimicrobial resistance.

Materials and methods

Forty-three clinical isolates of S. aureus were obtained from 150 pus samples using standard microbiological techniques. Biofilm formation in these isolates was detected by tissue culture plate (TCP) method and tube adherence method (TM). Antimicrobial susceptibility test was performed using the modified Kirby–Bauer disk diffusion method as per Clinical and Laboratory Standards Institute guidelines. MRSA was detected using the cefoxitin disk test.

Results

Biofilm formation was observed in 30 (69.8%) and 28 (65.1%) isolates of S. aureus via TCP method and TM, respectively. Biofilm-producing S. aureus exhibited a higher incidence of antimicrobial resistance when compared with the biofilm nonproducers (P<0.05). Importantly, 86.7% of biofilm-producing S. aureus were multidrug resistant (MDR), whereas all the biofilm nonproducers were non-MDR (P<0.05). Large proportions (43.3%) of biofilm producers were identified as MRSA; however, none of the biofilm nonproducers were found to be MRSA (P<0.05).

Conclusion

Both the in vitro methods showed that S. aureus isolated from wound infection of hospitalized patients have high degree of biofilm-forming ability. Biofilm-producing strains have very high tendency to exhibit antimicrobial resistance, multidrug resistance and methicillin resistance. Regular surveillance of biofilm formation by S. aureus and their antimicrobial resistance profile may lead to the early treatment of the wound infection.

Keywords:

• biofilm
• multidrug resistant
• methicillin-resistant Staphylococcus aureus

Supplementary material

Table S1 Grading of biofilm producers by two different methods

Acknowledgments

The authors are grateful to the laboratory staff and management of CMCTH for their help and cooperation during the study.

Author contributions

P Neopane and Y Abiko conceived the design of the study. P Neopane and O Uehara were involved in laboratory procedure, data collection and analysis. P Neopane, Y Abiko, R Shrestha and HP Nepal prepared the manuscript. Y Abiko and O Uehara did interpretation of data and statistical analysis. All authors contributed toward data analysis, drafting and revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.