Tag Archives: MRSA

Screening Inpatients for MRSA — Case Closed

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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.

 

Molecular Typing of Staphylococcus aureus and Methicillin-Resistant S. aureus (MRSA) Isolated from Animals and Retail Meat in North Dakota, United States

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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.

 

Transmission of methicillin-resistant Staphylococcus aureus in the long term care facilities in Hong Kong

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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.