Study of the association between the colony morphology, biofilm formation ability of Staphylococcus aureus isolates, and their resistance patterns

Background and objectives. Staphylococcus aureus is implicated in a wide range of infectious diseases. Previous studies have recognized that colony characteristics of Staphylococcus aureus might be useful in identifying methicillin-resistant Staphylococcus aureus (MRSA), particularly in resource-limited settings. However, the correlation between MRSA colony characteristics and biofilm formation has not been fully assessed. This study aimed to investigate the presence of dome-shaped (T2) and target-shaped (T1) colony morphology among MRSA isolated from clinical samples and to evaluate the correlation between these morphologies and biofilm-forming ability. Materials and methods. A total of 14 S. aureus isolates were analyzed. Identification was confirmed using the VITEK® 2 system. Isolates were obtained from clinical swabs at Al-Kafeel Hospital between November 2023 and February 2024. Colony morphology was determined by culturing on blood and nutrient agar. Antimicrobial susceptibility testing was performed using the disk diffusion method to detect MRSA. The biofilm-forming capacity of the isolates was also assessed. Results. All 14 isolates were identified as MRSA. Half of the isolates displayed target-shaped morphology (T1), and half displayed dome-shaped morphology (T2). T2 isolates exhibited a trend toward greater biofilm-forming capacity than T1 isolates; however, the difference was not statistically significant (p > 0.05). These findings highlight the need for larger studies to determine whether a significant association exists. Conclusions. In this small sample, colony morphology was visually distinct but not significantly associated with biofilm-forming capacity. Interestingly, T1 isolates demonstrated slightly greater biofilm formation than T2 isolates. Further research with larger sample sizes is required to clarify these observations.