OBJECTIVES: Emerging evidence shows that methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates with higher vancomycin MICs within the susceptibility range are associated with adverse outcomes. No study, however, has examined different susceptibility tests in predicting treatment outcomes of MRSA infections. METHODS: This retrospective cohort study included 393 patients with MRSA bacteraemia. Vancomycin MICs for all MRSA isolates were determined simultaneously by agar dilution and the Etest, and using the MicroScan, VITEK-2 and Phoenix automated systems, and categorized into low- and high-MIC isolates at a breakpoint of ≥ 2 mg/L. The essential and categorical agreement between testing methods was compared. The method-specific ability to predict in-hospital mortality was examined by multivariate logistic regression analysis controlling for other potential confounders using clinical data from 310 vancomycin-treated MRSA bacteraemia patients. RESULTS: The agar dilution, Etest, MicroScan, VITEK-2 and Phoenix methods assessed 14.2% (56/393), 9.7% (38/393), 28.8% (113/393), 22.6% (89/393) and 3.1% (12/393) of MRSA isolates as having high (≥ 2 mg/L) vancomycin MICs. The essential and categorical agreement between testing methods ranged from 98.5% to 100% and from 73.8% to 91.9%, respectively. High vancomycin MICs for isolates determined using agar dilution and the Etest independently predicted mortality when controlling for confounding factors [adjusted OR, 2.321; 95% CI, 1.160-4.641; and adjusted OR, 3.121; 95% CI, 1.293-7.536, respectively]. High vancomycin MICs determined using all three automated systems failed to predict mortality. CONCLUSIONS: Vancomycin MICs generated by the agar dilution and Etest methods, but not the automated systems, independently predicted mortality among vancomycin-treated MRSA bacteraemia patients. Clinicians should incorporate this information with clinical assessment for decisions on appropriate anti-MRSA treatment.
OBJECTIVES: Emerging evidence shows that methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates with higher vancomycin MICs within the susceptibility range are associated with adverse outcomes. No study, however, has examined different susceptibility tests in predicting treatment outcomes of MRSA infections. METHODS: This retrospective cohort study included 393 patients with MRSA bacteraemia. Vancomycin MICs for all MRSA isolates were determined simultaneously by agar dilution and the Etest, and using the MicroScan, VITEK-2 and Phoenix automated systems, and categorized into low- and high-MIC isolates at a breakpoint of ≥ 2 mg/L. The essential and categorical agreement between testing methods was compared. The method-specific ability to predict in-hospital mortality was examined by multivariate logistic regression analysis controlling for other potential confounders using clinical data from 310 vancomycin-treated MRSA bacteraemiapatients. RESULTS: The agar dilution, Etest, MicroScan, VITEK-2 and Phoenix methods assessed 14.2% (56/393), 9.7% (38/393), 28.8% (113/393), 22.6% (89/393) and 3.1% (12/393) of MRSA isolates as having high (≥ 2 mg/L) vancomycin MICs. The essential and categorical agreement between testing methods ranged from 98.5% to 100% and from 73.8% to 91.9%, respectively. High vancomycin MICs for isolates determined using agar dilution and the Etest independently predicted mortality when controlling for confounding factors [adjusted OR, 2.321; 95% CI, 1.160-4.641; and adjusted OR, 3.121; 95% CI, 1.293-7.536, respectively]. High vancomycin MICs determined using all three automated systems failed to predict mortality. CONCLUSIONS:Vancomycin MICs generated by the agar dilution and Etest methods, but not the automated systems, independently predicted mortality among vancomycin-treated MRSA bacteraemiapatients. Clinicians should incorporate this information with clinical assessment for decisions on appropriate anti-MRSA treatment.
Authors: Kimberly C Claeys; Evan J Zasowski; Anthony M Casapao; Abdalhamid M Lagnf; Jerod L Nagel; Cynthia T Nguyen; Jessica A Hallesy; Mathew T Compton; Keith S Kaye; Donald P Levine; Susan L Davis; Michael J Rybak Journal: Antimicrob Agents Chemother Date: 2016-09-23 Impact factor: 5.191
Authors: Sean B Sullivan; Eloise D Austin; Stephania Stump; Barun Mathema; Susan Whittier; Franklin D Lowy; Anne-Catrin Uhlemann Journal: Antimicrob Agents Chemother Date: 2017-06-27 Impact factor: 5.191
Authors: Sanjiv M Baxi; Angelo Clemenzi-Allen; Alice Gahbauer; Daniel Deck; Brandon Imp; Eric Vittinghoff; Henry F Chambers; Sarah Doernberg Journal: Antimicrob Agents Chemother Date: 2016-08-22 Impact factor: 5.191
Authors: Masayuki Nigo; Lorena Diaz; Lina P Carvajal; Truc T Tran; Rafael Rios; Diana Panesso; Juan D Garavito; William R Miller; Audrey Wanger; George Weinstock; Jose M Munita; Cesar A Arias; Henry F Chambers Journal: Antimicrob Agents Chemother Date: 2017-02-23 Impact factor: 5.191
Authors: Guillermo Cuervo; Mariana Camoez; Evelyn Shaw; María Ángeles Dominguez; Oriol Gasch; Belén Padilla; Vicente Pintado; Benito Almirante; José Molina; Francisco López-Medrano; Enrique Ruiz de Gopegui; José A Martinez; Elena Bereciartua; Fernando Rodriguez-Lopez; Carlos Fernandez-Mazarrasa; Miguel Ángel Goenaga; Natividad Benito; Jesús Rodriguez-Baño; Elena Espejo; Miquel Pujol Journal: BMC Infect Dis Date: 2015-10-30 Impact factor: 3.090