Factors associated with methicillin resistance in Staphylococcus aureus: a case-case-control analysis of AMR...

This study examined clinical, demographic, and geographic factors associated with methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA and MSSA) isolation in a global surveillance dataset.

We analyzed Antimicrobial Testing Leadership and Surveillance (ATLAS) data (2004-2021) from 61 countries using a case-case-control design comparing MRSA and MSSA cases with Enterococcus spp.

Multivariable regression assessed factors associated with isolation. Model performance was assessed using VIF (< 2), Hosmer-Lemeshow tests (p > 0.05), and ROC-AUC (> 0.94).

We analyzed 155,482 isolates (54,599 MRSA, 63,101 MSSA, 37,782 Enterococcus). Models showed excellent discrimination (ROC-AUC: 0.945 for MRSA, 0.943 for MSSA). Substantial variation in isolation patterns was observed across countries. Compared with the United States, the relative MRSA odds were higher in Venezuela (OR = 1.66), Colombia (OR = 1.63), and Taiwan (OR = 1.57), while MSSA odds were higher in India, Kuwait, Brazil, Chile, Taiwan, and Israel. Compared with infants aged 0-2, children aged 3-12 and adolescents aged 13-18 years had higher odds of both MRSA and MSSA isolation. Relative to general surgery units, both MRSA and MSSA were more frequently isolated from the emergency and general medicine units. Compared with abdominal fluid samples, MRSA odds were highest in sputum (OR = 28.68), while MSSA showed a similar pattern in sputum (OR = 31.60), lower respiratory tract samples (OR = 26.26), abscesses (OR = 11.79), and wound samples (OR = 7.38). MRSA isolates also showed higher odds of levofloxacin co-resistance (OR = 11.19).

This analysis describes variation in MRSA and MSSA characteristics across ATLAS settings. These findings may inform region-specific infection control strategies and highlight the need for continued global antimicrobial resistance surveillance.