A cross-sectional molecular epidemiological study of biofilm-producing methicillin-resistant Staphylococcus aureus

Abstract

There is growing concern regarding biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) due to the sudden rise in infection rates and associated morbidity and mortality. Therefore, epidemiological studies, including molecular typing and correlation analysis, are essential for understanding this pathogen. This cross-sectional study investigated epidemiological factors and correlations in MRSA isolates. A total of 300 clinical samples were collected between January and March 2023 from 2 healthcare facilities, including various sample types such as sputum, blood, urine, pus, wound swabs, and other body fluids. This study employed various phenotypic and genotypic methodologies, including adherence assays using standard microtiter plates, the Congo red agar method, antimicrobial resistance and virulence profiling, and multi-locus sequence typing. Among 300 clinical samples from 2 healthcare facilities in Egypt, 94 MRSA isolates were confirmed as biofilm producers. Phylogenetic analysis revealed 8 distinct sequence types (ST8, ST80, ST239, ST15, ST22, ST113, ST398, ST984), found in surgical unit samples across both facilities. Notably, ST22-MRSA was present in all departments, indicating its widespread nature and potential for cross-departmental transmission. ST239-MRSA, the most prevalent strain (22.3%), was found in all departments except burn units. Alarmingly, 95.7% of isolates exhibited multidrug-resistant patterns. However, resistance to vancomycin and imipenem was low among biofilm-producing isolates. The high diversity of MRSA strains suggests multiple sources of infection rather than a single origin. Although most isolates were unrelated, the presence of 2 ST80 isolates in sputum samples from the same unit underscores the importance of targeted infection control within and between hospital areas. ST8-MRSA strains carrying the vanA gene were predominantly identified in body fluid samples, highlighting the need for regular testing in such cases. The diversity of MRSA strains across hospital departments indicates a complex infection landscape with no single source. Although certain genetic markers are linked to specific sequence types, they are not reliable indicators of MRSA clonality. These findings emphasize the need for strict infection control measures and regular testing, particularly for ST8-MRSA in body fluids.