To identify important risk factors for recurrent methicillin-resistant Staphylococcus aureus (MRSA) to assist clinicians in identifying high-risk patients for continued surveillance and follow-up.

In this retrospective cohort study, we examined patients with MRSA bacteremia at 122 Veterans Affairs medical facilities from January 1, 2003, through December 31, 2010. Recurrent MRSA bacteremia was identified by a positive blood culture result from 2 to 180 days after index hospitalization discharge. Subset analyses were performed to evaluate risk factors for early-onset (2–60 days after discharge) and late-onset (61–180 days after discharge) recurrence. Risk factors were evaluated using Cox proportional hazards regression.

Of 18,425 patients, 1,159 (6.3%) had recurrent MRSA bacteremia. The median time to recurrence was 63 days. Longer duration of index bacteremia, increased severity of illness, receipt of only vancomycin, community-acquired infection, and several comorbidities were risk factors for recurrence. Congestive heart failure, hypertension, and rheumatoid arthritis/collagen disease were risk factors for early-onset but not late-onset recurrence. Geographic region and cardiac arrhythmias were risk factors for late-onset but not early-onset recurrence.

Risk factors for recurrent MRSA bacteremia included comorbidities, severity of illness, duration of bacteremia, and receipt of only vancomycin. Awareness of risk factors may be important at patient discharge for implementation of quality improvement initiatives including surveillance, follow-up, and education for high-risk patients.

Infect Control Hosp Epidemiol 2015;00(0): 1–7

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is changing, with USA300 emerging first in community and then in healthcare settings. We performed nationwide surveillance to assess recent trends in the molecular epidemiology of MRSA.

One hundred consecutive unique clinically significant S. aureus isolates were recovered from patients at each of 43 US centers between July 1, 2011, and December 31, 2011. Susceptibility testing, pulsed-field gel electrophoresis (PFGE), staphylococcal protein A gene (spa) and staphylococcal cassette chromosome mec typing, and Panton-Valentine leukocidin detection were performed on all MRSA isolates.

Of 4,131 isolates collected, 2,093 (51%) were MRSA. Specimen sources of MRSA isolates included wound or abscess (54%), blood (24%), lower respiratory tract (11%), and other sterile site (10%). Thirty percent were isolated more than 48 hours after hospital admission (ie, were associated with nosocomial acquisition of infection). USA300 was the most common PFGE type (1,269 isolates; 61%), overall and in all regions, followed by USA100 (368 isolates; 18%). Among 173 spa types found, the most common were t008 (51%) and t002 (18%); no other spa type accounted for more than 2% of isolates. One strain type (USA300/t008/IV) constituted almost half of all MRSA isolates (1,005 isolates; 48%) and was the most common at all body sites, causing 37% of MRSA bloodstream infections (BSIs) and 38% of nosocomial MRSA infections. Multidrug-resistant phenotypes were found among 34 USA300 isolates (3%) from 18 states.

The USA300 PFGE type continues to advance nationwide. A single strain type (USA300/t008/IV) predominates in all regions and infection sites and is now more common than USA 100 as a cause of MRSA BSI and nosocomial infections. Although most USA300 retain typical susceptibility profiles, multidrug-resistant phenotypes are emerging.

The literature is conflicted as to whether people colonized with Staphylococcus aureus are at an increased risk of mortality. The aim of this meta-analysis was to review and analyze the current literature to determine whether prior history of S. aureus colonization is associated with mortality among S. aureus-infected patients.

The PUBMED databases were searched with keywords related to S. aureus colonization and mortality. After reviewing 380 article abstracts and 59 articles in detail, only 7 studies had data on the association between S. aureus colonization and mortality among S. aureus-infected patients. Crude estimates of study odds ratios (ORs) were calculated on the basis of data from subset analyses. We pooled crude ORs from the 7 studies using a random-effects model. Woolf's test for heterogeneity was assessed.

When all studies were pooled in a random-effects model, no association between S. aureus colonization and mortality among S. aureus-infected patients was seen (pooled OR, 1.08 [95% confidence interval (CI), 0.32–3.66]; n = 7; heterogeneity P = .05). When the analyses were restricted to infection-attributable mortality, the association between colonization and mortality among S. aureus-infected patients was not statistically significant (pooled OR, 0.42 [95% CI, 0.15–1.21]; n = 4; heterogeneity P = .28).

S. aureus colonization was not associated with mortality among patients who developed an S. aureus infection. Interventions to decolonize S. aureus carriers may prevent S. aureus infections but may not be sufficient to prevent mortality.