Clinical and Laboratory Characteristics of Invasive Infections Due to Methicillin-Resistant Staphylococcus aureus Isolates Demonstrating a Vancomycin MIC of 2 Micrograms per Milliliter: Lack of Effect of Heteroresistant Vancomycin-Intermediate S. aureus Phenotype
ABSTRACT We describe clinical and laboratory characteristics of invasive methicillin-resistant Staphylococcus aureus (MRSA) infections with vancomycin MICs of 2 μg/ml and compare heteroresistant-intermediate S. aureus (hVISA) to non-hVISA. Health care-associated community-onset infections were the most common and resulted in frequent complications and relapses. hVISA-infected patients were more likely to have been hospitalized in the year prior to MRSA culture.
Full-textDOI: · Available from: Ghinwa Dumyati, Jun 27, 2015
- Clinical Infectious Diseases 03/2012; 54(6):772-4. DOI:10.1093/cid/cir932 · 9.42 Impact Factor
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ABSTRACT: The clinical implications of reduced vancomycin susceptibility amongst methicillin-resistant Staphylococcus aureus (MRSA) are controversial, and crossresistance to daptomycin amongst such strains has been reported. As a consequence of 'MIC creep', higher trough levels were recommended for serious infections. This review focusses on the new data published in the past 18 months that pertain to these issues. Heteroresistant vancomycin-intermediate Staphylococcus aureus reduces the clinical response rates to vancomycin in bacteraemic MRSA patients without impacting on mortality as opposed to 'MIC creep' with vancomycin minimum inhibitory concentration (MIC) levels of ≥1.5 mg/l that are significantly associated with mortality. Although daptomycin resistance is rare, 'concomitant MIC creep' amongst MRSA isolates with increasing vancomycin MICs may occur or exist concurrently amongst such strains. The aggressive vancomycin dosing regimens are still associated with unacceptable high microbiological failure rates and it is not currently possible to achieve probability of target attainment at higher vancomycin MICs of 2 mg/l. The nephrotoxic impact of high-dose vancomycin therapy has been confirmed. Continued monitoring of patients on aggressive vancomycin dosing schedules is advised. Unless alternative dosing strategies prove otherwise efficacious, an alternative antibiotic should be considered for severe MRSA infections with vancomycin MICs greater than 1 mg/l. The utility of vancomycin may be waning but will depend on the prevalence of resistant MRSA phenotypes in a specific ICU.Current opinion in critical care 08/2012; 18(5):451-9. DOI:10.1097/MCC.0b013e3283578968 · 3.18 Impact Factor
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ABSTRACT: A total of 434 methicillin-resistant Staphylococcus aureus (MRSA) baseline isolates were collected from subjects enrolled in a prospective, double-blind randomized trial comparing linezolid versus vancomycin for the treatment of nosocomial pneumonia. Isolates were susceptibility tested by broth microdilution, examined for inducible clindamycin resistance by D-test, and screened for heterogeneous resistance to vancomycin (hVISA) by the Etest macromethod. All strains were subjected to Panton-Valentine leukocidin (PVL) screening, and SCCmec, pulsed-field gel electrophoresis (PFGE), and spa typing. Selected strains were evaluated by multilocus sequence typing (MLST). Clonal complexes (CCs) were assigned based on the spa and/or MLST results. Most strains were CC5 (56.0%), which originated from North America (United States) (CC5-MRSA-SCCmec II/IV; 70.0%), Asia (CC5-MRSA-II; 14.0%) and Latin America (CC5-MRSA-I/II; 12.3%). The second- and third-most-prevalent clones were CC8-MRSA-IV (23.3%) and CC239-MRSA-III (11.3%), respectively. Furthermore, the CC5-MRSA-I/II clone predominated in Asia (50.7% within this region) and Latin America (66.7%), followed by CC239-MRSA-III (32.8% and 28.9%, respectively). The European strains were CC8-MRSA-IV (34.5%), CC22-MRSA-IV (18.2%), or CC5-MRSA-I/II/IV (16.4%), while the U.S. MRSA isolates were CC5-MRSA-II/IV (64.4%) or CC8-MRSA-IV (28.8%). Among the U.S. CC8-MRSA-II/IV strains, 73.7% (56/76 [21.2% of all U.S. MRSA strains]) clustered within USA300. One strain from the United States (USA800) was intermediate to vancomycin (MIC, 4 μg/ml). All remaining strains were susceptible to linezolid, daptomycin, vancomycin, and teicoplanin. hVISA strains (14.5%) were predominantly CC5-MRSA-II, from South Korea, and belonged to a single PFGE type. Overall, each region had two predominant clones. The USA300 rate corroborates previous reports describing increased prevalence of USA300 strains causing invasive infections. The prevalence of hVISA was elevated in Asia, and these strains were associated with CC5.Journal of clinical microbiology 09/2012; 50(11):3694-702. DOI:10.1128/JCM.02024-12 · 4.23 Impact Factor