Anti-methicillin-resistant Staphylococcus aureus (MRSA) therapy in addition to standard pneumonia therapy does not improve mortality, according to results of a study published in JAMA Internal Medicine.
In the United States, the leading cause of death from infection is pneumonia. Currently, timely empiric antibiotic therapy against the most likely pathogens is the cornerstone of care; however, the causative pathogens are rarely identified, which creates uncertainty in choosing an empiric therapy. This uncertainty has been magnified among patients who are hospitalized for community-onset pneumonia with the emergence of resistance organisms, like MRSA. Although fewer than 5% of hospitalized patients have resistant organisms, more than one-third have received broad-spectrum antibiotics.
The association of empiric anti-MRSA therapy with outcomes among patients with pneumonia remains unknown with some studies suggesting that empiric broad-spectrum therapy is harmful. In addition, it is unclear which patients would benefit from empirical treatment with broad-spectrum agents. Therefore, this retrospective multicenter cohort study compared 30-day mortality rates among patients hospitalized for pneumonia receiving empiric anti-MRSA therapy vs standard empiric antibiotic regimens.
In total, 88,605 hospitalized patients with community-onset pneumonia between 2008 and 2013 from the Veterans Health Administration healthcare system were included in the study. Patients received either empirical anti-MRSA therapy plus standard pneumonia therapy (n=33,632) or standard therapy alone (n=54,973) within the first day of hospitalization for community-onset pneumonia. The primary objective was the risk for 30-day all-cause mortality after adjustment for patient comorbidities, vital signs, and laboratory results. The secondary outcomes included the development of kidney injury and secondary infections. Patients were also analyzed in the following subgroups: initial intensive care unit admission, MRSA risk factors, positive results of a MRSA surveillance test, and positive results of MRSA admission culture.
The results suggested that empiric anti-MRSA therapy was not associated with reduced mortality in the management of patients with pneumonia. Of the patients who received empiric anti-MRSA therapy, 8929 (10%) died within 30 days. Empiric anti-MRSA therapy plus standard therapy was associated with an increased adjusted risk for death (adjusted risk ratio [aRR], 1.4), kidney injury (aRR, 1.4), secondary Clostridioides difficile infections (aRR, 1.6), secondary vancomycin-resistant Enterococcus spp infections (aRR, 1.6), and secondary gram-negative rod infections (aRR, 1.5). In addition, similar associations were seen between anti-MRSA therapy and 3-day mortality by instrumental variable analysis (aRR, 1.6) among patients admitted to the intensive care unit (aRR, 1.3), those with MRSA detected on surveillance testing (aRR, 1.6), and patients with a high risk for MRSA (aRR, 1.2). There was no significant favorable association between empiric anti-MRSA therapy and death among patients with culture-detected MRSA observed (aRR, 1.1)
The study authors concluded that, “These results contribute to a growing body of evidence that questions the value of empirical use of anti-MRSA therapy using existing risk approaches.”
Jones BE, Ying J, Stevens V, et al. Empirical anti-MRSA vs standard antibiotic therapy and risk of 30-day mortality in patients hospitalized for pneumonia. JAMA Intern Med. doi:10.1001/jamainternmed.2019.7495