Coinfection with influenza virus and methicillin-resistant Staphylococcus aureus (MRSA) causes life-threatening necrotizing pneumonia in children. Sporadic incidence precludes evaluation of antimicrobial efficacy. We assessed the clinical characteristics and outcomes of critically ill children with influenza–MRSA pneumonia and evaluated antibiotic use.

We enrolled children (<18 years) with influenza infection and respiratory failure across 34 pediatric intensive care units 11/2008–5/2016. We compared baseline characteristics, clinical courses, and therapies in children with MRSA coinfection, non-MRSA bacterial coinfection, and no bacterial coinfection.

We enrolled 170 children (127 influenza A, 43 influenza B). Children with influenza–MRSA pneumonia (N = 30, 87% previously healthy) were older than those with non-MRSA (N = 61) or no (N = 79) bacterial coinfections. Influenza–MRSA was associated with increased leukopenia, acute lung injury, vasopressor use, extracorporeal life support, and mortality than either group (P ≤ .0001). Influenza-related mortality was 40% with MRSA compared to 4.3% without (relative risk [RR], 9.3; 95% confidence interval [CI], 3.8–22.9). Of 29/30 children with MRSA who received vancomycin within the first 24 hours of hospitalization, mortality was 12.5% (N = 2/16) if treatment also included a second anti-MRSA antibiotic compared to 69.2% (N = 9/13) with vancomycin monotherapy (RR, 5.5; 95% CI, 1.4, 21.3; P = .003). Vancomycin dosing did not influence initial trough levels; 78% were <10 µg/mL.

Influenza–MRSA coinfection is associated with high fatality in critically ill children. These data support early addition of a second anti-MRSA antibiotic to vancomycin in suspected severe cases.