Edmond MB, Wenzel RP. N Eng J Med. 29 May 2013. doi:10.1056/NEJMe1304831.
Available at http://www.nejm.org/doi/full/10.1056/NEJMe1304831
Excerpt. One of the most controversial concepts in health care epidemiology during the past decade has been the active detection and isolation of patients with methicillin-resistant Staphylococcus aureus (MRSA) colonization. The basic strategy is to screen inpatients for MRSA, typically with a polymerase-chain-reaction–based technology, in order to rapidly identify patients colonized with the organism and then initiate contact precautions (place them in a private room and require gowns and gloves on room entry). This approach has been used for decades to control outbreaks caused by epidemiologically important pathogens. As MRSA became endemic in hospitals, studies began to appear suggesting that active detection and isolation reduced health care–associated infections. However, the vast majority of the studies were single-center, observational, nonrandomized, before-and-after evaluations, which yielded low-quality evidence and precluded the establishment of causality. Nonetheless, most hospitals adopted programs of active detection and isolation, and nine states mandated MRSA screening of inpatients.
Buyukcangaz E, Velasco V, Sherwood J, et al. Foodborne Pathogens and Disease. 2 May 2013. doi:10.1089/fpd.2012.1427.
Available at http://online.liebertpub.com/doi/abs/10.1089/fpd.2012.1427
Abstract. The objective of this study was to determine the prevalence and molecular typing of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in food-producing animals and retail meat in Fargo, North Dakota. A two-step enrichment followed by culture methods were used to isolate S. aureus from 167 nasal swabs from animals, 145 samples of retail raw meat, and 46 samples of deli meat. Positive isolates were subjected to multiplex polymerase chain reaction in order to identify the genes 16S rRNA, mecA, and Panton-Valentine Leukocidin. Pulsed-field gel electrophoresis and multilocus sequence typing were used for molecular typing of S. aureus strains. Antimicrobial susceptibility testing was carried out using the broth microdilution method. The overall prevalence of S. aureus was 37.2% (n=133), with 34.7% (n=58) of the animals positive for the organism, and the highest prevalence observed in pigs (50.0%) and sheep (40.6%) (p<0.05); 47.6% (n=69) of raw meat samples were positive, with the highest prevalence in chicken (67.6%) and pork (49.3%) (p<0.05); and 13.0% (n=6) of deli meat was positive. Five pork samples (7.0%) were positive for MRSA, of which three were ST398 and two were ST5. All exhibited penicillin resistance and four were multidrug resistant (MDR). The Panton-Valentine Leukocidin gene was not detected in any sample by multiplex polymerase chain reaction. The most common clones in sheep were ST398 and ST133, in pigs and pork both ST398 and ST9, and in chicken ST5. Most susceptible S. aureus strains were ST5 isolated from chicken. The MDR isolates were found in pigs, pork, and sheep. The presence of MRSA, MDR, and the subtype ST398 in the meat production chain and the genetic similarity between strains of porcine origin (meat and animals) suggest the possible contamination of meat during slaughtering and its potential transmission to humans.
Cheng CVV, Tai JWM, Wong ZSY, et al. BMC Infectious Diseases. 6 May 2013. 13:205. doi:10.1186/1471–2334-13–205.
Available at http://www.biomedcentral.com/1471–2334/13/205/abstract
Background. The relative contribution of long term care facilities (LTCFs) and hospitals in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) is unknown.
Methods. Concurrent MRSA screening and spa type analysis was performed in LTCFs and their network hospitals to estimate the rate of MRSA acquisition among residents during their stay in LTCFs and hospitals, by colonization pressure and MRSA transmission calculations.
Results. In 40 LTCFs, 436 (21.6%) of 2020 residents were identified as ‘MRSA-positive’. The incidence of MRSA transmission per 1000-colonization-days among the residents during their stay in LTCFs and hospitals were 309 and 113 respectively, while the colonization pressure in LTCFs and hospitals were 210 and 185 per 1000-patient-days respectively. MRSA spa type t1081 was the most commonly isolated linage in both LTCF residents (76/121, 82.8%) and hospitalized patients (51/87, 58.6%), while type t4677 was significantly associated with LTCF residents (24/121, 19.8%) compared with hospitalized patients (3/87, 3.4%) (p < 0.001). This suggested continuous transmission of MRSA t4677 among LTCF residents. Also, an inverse linear relationship between MRSA prevalence in LTCFs and the average living area per LTCF resident was observed (Pearson correlation –0.443, p = 0.004), with the odds of patients acquiring MRSA reduced by a factor of 0.90 for each 10 square feet increase in living area.
Conclusions. Our data suggest that MRSA transmission was more serious in LTCFs than in hospitals. Infection control should be focused on LTCFs in order to reduce the burden of MRSA carriers in healthcare settings.