Staphylococcus aureus (S. aureus) is an important causative agent in human infections. Biofilm-production is an important virulence factor of many pathogens, often leading to chronic infections. There has been significant interest in assessing the possible relationship between the multidrug-resistant (MDR) status and the biofilm-producer phenotype. In the present study, the biofilm-production rates in clinical methicillin-susceptible [MSSA] and resistant [MRSA] S. aureus isolates were characterized; in addition, the correlation between their antibiotic resistance and biofilm-forming capacity was also assessed. A total of three hundred (n=300) S. aureus isolates (MSSA and MRSA isolates in equal measure) were included in this study. Identification of the isolates was carried out using the VITEK 2 ID/AST automated system and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method and E-tests. Biofilm-production was assessed using phenotypic methods, including the crystal violet (CV) tube-adherence method and the Congo red agar (CRA) plate method. There were significant differences among MSSA and MRSA isolates regarding susceptibility-levels to commonly-used antibiotics (erythromycin, clindamycin and ciprofloxacin: p<0.001, gentamicin: p=0.023, sulfamethoxazole/trimethoprim: p=0.027, rifampin: p=0.037). In the CV tube adherence-assay, 37% (n=56) of MSSA and 39% (n=58) of MRSA isolates were positive for biofilm-production, while during the use of CRA plates, 41% (n=61) of MSSA and 44% (n=66) of MRSA were positive. Biofilm-positive isolates were most common from catheter-associated infections. Overall, no associations were found between methicillin-resistance and biofilm-production; however, resistance to erythromycin, clindamycin and rifampin was associated with biofilm-positivity (p=0.004, p<0.001 and p<0.001, respectively). The relationship between the MDR phenotype and biofilm-positivity in S. aureus has been studied extensively, but the results available in the literature are still inconclusive.
Correlation between biofilm-formation and antibiotic resistance in Staphylococcus aureus: an in vitro study using phenotypic methods
Published: 03 May 2021 by MDPI in The 1st International Electronic Conference on Antibiotics—The Equal Power of Antibiotics And Antimicrobial Resistance session Antimicrobial Resistance Mechanisms and Intrinsic Microbial Factors Contributing to Resistance
https://doi.org/10.3390/ECA2021-09746 (registering DOI)
Keywords: Staphylococcus aureus; MSSA; MRSA; biofilm; antibiotic resistance; crystal violet; Congo red agar; phenotypic assay