Risk factors of methicillin-resistant Staphylococcus aureus bacteremic pneumonia in the emergency department

The infection rate of methicillin-resistant Staphylococcus aureus (MRSA) has increased worldwide and MRSA bacteremic pneumonia is associated with a high mortality rate. This is a retrospective study conducted at a university hospital in Korea involving adult patients diagnosed as bacteremic pneumonia caused by S. aureus in the ED between January 2009 and December 2019. We compared MRSA bacteremic pneumonia patients (n = 56) to methicillin-susceptible S. aureus bacteremic pneumonia patients (n = 49). Our study showed that that underlying hypertension (OR = 5.68; 95% CI = 2.00-16.11; p = 0.001) and cerebrovascular disease (OR = 3.54; 95% CI = 1.06-11.75; p = 0.038), recent intravenous therapy within 1 month (OR = 8.38; 95% CI = 2.88-24.38; p = 0.0001), and pleural effusion on chest radiography (OR = 5.77; 95% CI = 1.79-18.57; p = 0.003) were independent risk factors for MRSA bacteremic pneumonia presenting to the ED. Although MRSA infection has been more frequently derived from the community than before, inappropriate empiric antibiotic treatment was overwhelmingly observed in the majority of patients in our study. Considering the resistance of MRSA to the typical empiric regimen prescribed for community-acquired pneumonia, emergency physicians should pay attention to the predictors for MRSA bacteremic pneumonia including pleural effusion on chest radiography when deciding on the appropriate empiric antimicrobial therapy for pneumonia patients in the ED.