Outcomes associated with bacteremia in the setting of methicillin-resistant Staphylococcus aureus pneumonia: a retrospective cohort study

Abstract

IntroductionMethicillin-resistant Staphylococcus aureus (MRSA) remains an important pathogen in pneumonia. Bacteremia may secondarily complicate MRSA pneumonia. The epidemiology and outcomes associated with bacteremia in the setting of MRSA pneumonia are unknown. We sought to describe the prevalence of bacteremia in MRSA pneumonia and its impact on hospital mortality and length of stay (LOS).MethodsWe conducted a single-center retrospective cohort study (2008–2013) including adult patients hospitalized with pneumonia caused by MRSA. We defined pneumonia based on clinical criteria and all cases were culture confirmed. MRSA bacteremia was identified based on positive blood cultures. Pneumonia was categorized as either community-onset (CO, occurring at presentation or within 2 days of admission) or hospital-onset (HO, occurring > 2 days after admission). We compared bacteremic and non-bacteremic groups with respect to their demographic and clinical characteristics and outcomes. A logistic regression and a generalized linear model (GLM) were constructed to examine the impact of bacteremia on hospital mortality and post-pneumonia onset LOS, respectively.ResultsAmong the 765 patients with MRSA pneumonia (33.1 % CO), 93 (12.2 %) had concurrent bacteremia (37.6 % CO). Patients with bacteremia were similar to non-bacteremic subjects based on demographic and clinical characteristics with the exception of frequency of a hospitalization within prior 180 days (48.4 % bacteremic and 37.7 % non-bacteremic, p = 0.047), prevalence of chronic liver disease (17.2 % vs. 9.5 %, p = 0.030), and the mean APACHE II score at the onset of pneumonia (17.5 ± 6.0 vs. 16.1 ± 6.0, p = 0.045). Both unadjusted mortality (33.7 % vs. 23.8 %, p = 0.067) and median post-pneumonia LOS (18.2 vs. 12.2 days, p < 0.001) were greater in the bacteremic than the non-bacteremic group. In a logistic regression, bacteremia showed a trend toward an association with increased mortality (odds ratio 1.56, 95 % confidence interval 0.93 to 2.61). Concomitant bacteremia was independently associated with a 10.3-day increase in the post-pneumonia hospital LOS (95 % confidence interval 6.7 to 13.9 days).ConclusionsConcurrent bacteremia occurred with moderate frequency in the setting of hospitalization with MRSA pneumonia. Although bacteremia did not appear to independently impact mortality, this was likely due to our study’s limited sample size. However, bacteremia complicating MRSA pneumonia added between 1 and 2 weeks to the hospital LOS.

Clinical outcomes after initial treatment of methicillin-resistant <em>Staphylococcus aureus</em> infections

“… 14 In addition, an analysis of variables associated with clinical success, using data from a randomized trial, found that treatment with linezolid was more likely to be successful (OR=1.55; 95% CI=1.01–2.34). 15 The results of our study, which confirmed the efficacy of antimicrobials other than vancomycin as initial treatment of MRSA infections, of the lung in particular, are concordant with the results of these meta-analyses.…”

Multicenter Observational Study of Ceftaroline Fosamil for Methicillin-Resistant Staphylococcus aureus Bloodstream Infections

“…Comparison with data from previous daptomycin studies is challenging due to the exclusion of BSI secondary to pneumonia from these studies (9-11). One-third of this cohort was comprised of patients with a lower respiratory tract source of infection, which carries a high risk of mortality (25,26). Nonetheless, the proportion of patients who experienced failure was similar to that in a recently reported evaluation of daptomycin for MRSA BSI (11).…”

Estimating the burden of antimicrobial resistance: a systematic literature review

“…4 Estimates of Excess Length of Stay of Hospital/ICU Stay Caused by Antimicrobial Resistance. (i) - (iii) denote different methods used in a single study [ 48 – 51 , 58 , 59 , 76 , 122 , 123 , 132 , 133 ] …”

“…For those that did estimate excess length of stay, it was expected (given previous literature [ 28 ]) that multistate model length of stay estimates compared to those found using alternative methods would be more conservative. However, this review found that multistate model estimates for length of stay for MRSA infection and MRSA bloodstream infection were higher than those using stepwise analysis and regression analysis [ 48 , 50 , 58 , 59 ]. This is likely due to the fact that the described studies were set in different countries (Australia, Germany, Switzerland and US) and were mainly single centre studies, and so less externally valid.…”