Prevalence of and outcomes from Staphylococcus aureus pneumonia among hospitalized patients in the United States, 2009-2012.

BACKGROUND: The burden of Staphylococcus aureus pneumonia is unknown despite being a major cause of mortality. We investigated national estimates of methicillin-resistant S aureus (MRSA) and methicillin-susceptible S aureus (MSSA) pneumonias and predictors of in-hospital mortality and hospital length of stay (LOS).

METHODS: This was a retrospective analysis of the National Inpatient Sample from 2009-2012. Adult patients with an ICD-9-CM primary diagnosis code for MRSA or MSSA pneumonia were included. Data weights were used to derive national estimates. Prevalence rates were reported per 100,000 hospital discharges, with trends presented descriptively.

RESULTS: There were 104,562 patients who had a primary diagnosis of S aureus pneumonia, with 81,275 from MRSA. MRSA pneumonia prevalence decreased steadily from 2009 (75.6 cases per 100,000 discharges) to 2012 (56.6 cases per 100,000 discharges), with MSSA pneumonia experiencing a slight decrease. Mortality rates decreased between 2009 and 2012 for MRSA pneumonia (7.9% to 6.4%) and MSSA pneumonia (6.9% to 4.7%; P = .008). LOS was higher for MRSA (6.9-7.8 days) compared with MSSA (6.1-6.4 days).

CONCLUSIONS: The prevalence of MRSA pneumonia has decreased among hospitalized adults in the United States in recent years accompanied by improvements in mortality and LOS. Although the prevalence of MRSA pneumonia is declining, national vigilance is still warranted.