Effectiveness of cefazolin versus anti-staphylococcal β-lactam for treating methicillin-susceptible Staphylococcus aureus pneumonia in critically ill patients admitted to intensive care units: a multicenter cohort study

Critically ill patients carry a high risk of infections and related complications, which significantly increase mortality. For patients with confirmed methicillin-susceptible Staphylococcus aureus (MSSA) pneumonia, the optimal definitive β-lactam therapy remains controversial. To date, clinical evidence comparing the effectiveness of cefazolin against other antistaphylococcal β-lactam antibiotics in the intensive care unit (ICU) setting is limited. Therefore, this study aimed to evaluate the clinical effectiveness of cefazolin versus non-cefazolin β-lactam antibiotics for treating MSSA pneumonia in critically ill adults. We conducted a multicenter, retrospective cohort study from January 2016 to July 2021 at three tertiary hospitals in Saudi Arabia. The study included adult intensive care unit (ICU) patients with confirmed MSSA respiratory infections who received definitive, targeted anti-MSSA β-lactam therapy. Eligible patients were categorized into two groups based on the specific antibiotic received (cefazolin vs. non-cefazolin β-lactam antibiotics). The primary outcome was treatment failure, while all other endpoints were considered secondary. Logistic, linear, and negative binomial regression analyses were utilized to analyze the study’s endpoints, as appropriate. A total of 54 patients were included in the study, evenly distributed with 27 patients in the cefazolin group and 27 in the alternative anti-MSSA β-lactam group. The treatment failure rate was significantly higher in the cefazolin group compared to the non-cefazolin β-lactam antibiotics group (OR 5.73; 95% CI (1.303–25.191), p = 0.02). Moreover, the rate of re-escalation to other antibiotics was higher in the cefazolin group (OR 17.98; 95% CI (2.731–118.425), p = 0.002). No significant difference was found in time to defervescence, or MSSA recurrence infection rate within three months. In addition, in-hospital and 30-day mortality rates, ICU re-admission, length of stay, and ventilator-free days were not statistically significant different between the two groups. In critically ill patients with MSSA pneumonia, cefazolin was associated with higher rates of treatment failure and re-escalation compared to non-cefazolin β-lactams antibiotics. Further studies with a larger sample size are needed to validate these findings.