OBJECTIVES: To determine the risk factors associated with vancomycin treatment failure in adult patients with methicillin-resistant Staphylococcus aureus (MRSA) infection using electronic medical records.

METHODS: In a case-control design study, all adult patients hospitalized between January 2015 and December2021 with MRSA infection with confirmed MRSA microbiological isolation were included. Cases were those patients with therapeutic failure to vancomycin (as defined by mortality, no clinical improvement, change of antibiotic required, early relapse, or persistence of positive blood cultures) while controls were those who had a good clinical response. The significant variables of the bivariate analysis were included in a multiple analysis with an asymmetric logistic regression model.

RESULTS: A total of 105 patients (28 cases and 77 controls) were included. Median age was 49 years, and 59 (56%) were males. Age (OR 1.034; 95% CI 1.007-1.061, p = 0.011), osteomyelitis/septic arthritis (OR 6.035; 95% CI 2.282-15.956, p = 0.000) and minimum inhibitory concentration (MIC) (OR 5.971; 95% CI) 1,321-26,979, p = 0.020), were independent risk factors associated with vancomycin treatment failure. Vancomycin trough levels (measured in only 47 patients) were not different between cases and controls (OR 0.976; 95% CI 0.911-1.044, p = 0.478).

CONCLUSIONS: In our cohort, only three variables were found to be significant risk factor for therapeutic failure to vancomycin in MRSA infected patients: age, osteomyelitis/septic arthritis and MIC. Due to sample size limitation, other risk factors described in the literature might have gone undetected.