Nasal Carriage of Epidemic Methicillin-Resistant Staphylococcus aureus 15 (EMRSA-15) Clone Observed in Three Chicago-Area Long-Term Care Facilities.

The spread of pandemic methicillin-resistant Staphylococcus aureus (MRSA) clones such as USA300 and EMRSA-15 is a global health concern. As a part of a surveillance study of three long-term care facilities in the Greater Chicago area, phenotypic and molecular characterization of nasal MRSA isolates was performed. We report a cluster of pandemic EMRSA-15, an MRSA clone rarely reported from the United States, detected during this study.

Prospective observational study on central line-associated bloodstream infections and central venous catheter occlusions using a negative displacement connector with an alcohol disinfecting cap.

BACKGROUND: Major complications of central venous catheter (CVC) use include bloodstream infection and occlusion. We performed a prospective, observational study to determine the rate of central line-associated bloodstream infection (CLABSI) and CVC occlusion using a negative displacement connector with an alcohol disinfecting cap. METHODS: Patients were followed from the time of CVC insertion through 2 days after removal, at the time of hospital discharge if there was no documentation of removal, or 90 days after the insertion of the CVC if it was not removed. CLABSI was defined using National Healthcare Safety Network criteria. Data for evidence of lumen occlusions were extracted from the electronic health record. Direct observations were performed to assess adherence to hospital policy regarding CVC insertion practice. RESULTS: A total of 2,512 catheters from 2,264 patients were enrolled for this study. There were 21 CLABSIs (0.84%; 95% confidence interval [CI], 0.48%-1.19%; 0.62 per 1,000 line days) and 378 occlusions (15.05%; 95% CI, 13.65%-16.45%; 11.23 per 1,000 line days). Eighty-five direct observations demonstrated insertion protocol adherence in 881 of 925 (95.24%; 95% CI, 93.87%-96.61%) measured criteria. CONCLUSIONS: Lines placed following a standardized protocol using a negative displacement connector with an alcohol cap have low rates of infection compared with historically published findings. We also established that the occlusion rate is >15-fold the CLABSI rate.

Evaluation of multiple real-time PCR tests on nasal samples in a large MRSA surveillance program.

OBJECTIVES: We evaluated the LightCycler MRSA Advanced Test (Roche Molecular Diagnostics, Pleasanton, CA), the BD MAX MRSA assay (Becton Dickinson, Franklin Lakes, NJ), and the Xpert MRSA assay (Cepheid, Sunnyvale, CA) on nasal samples using the same population. METHODS: Admission and discharge nasal swabs were collected from inpatients using a double-headed swab. One swab was plated onto CHROMagar MRSA (CMA; Becton Dickinson, Sparks, MD) and then broken off into tryptic soy broth (TSB) for enrichment. TSB was incubated for 24 hours and then plated to CMA. The molecular tests were performed on the second swab. We analyzed the cost benefit of testing to evaluate what parameters affect hospital resources. RESULTS: A total of 27,647 specimens were enrolled. The sensitivity/specificity was 98.3%/98.9% for the LightCycler MRSA Advanced Test and 95.7%/98.8% for the Xpert MRSA assay, but the difference was not significant. The positive predictive value was 86.7% for the LightCycler MRSA Advanced Test, 82.7% for the Xpert MRSA assay (P > .1), and 72.2% and for the BD MAX MRSA test (P < .001 compared with the LightCycler MRSA Advanced Test). All three assays were cost-effective, with the LightCycler MRSA Advanced Test having the highest economic return. CONCLUSIONS: Our results suggest that the performance of the three commercial assays is similar. When assessing economic cost benefit of methicillin-resistant Staphylococcus aureus screening, the two measures with the most impact are the cost of the test and the specificity of the assay results.

Investigation of tigecycline bactericidal activity: Optimisation of laboratory testing.

The objectives of this study were to optimise the conditions for bactericidal testing of tigecycline and to investigate its bactericidal activity against clinical isolates of Gram-positive and Gram-negative bacteria. Tigecycline is the first in a new class of glycylcycline antibiotics exhibiting in vitro activity against a broad range of bacteria, including multidrug-resistant organisms. Its bactericidal activity in vitro has not been extensively investigated using multiple test conditions. Five growth media comprising Mueller Hinton broth, Minimum Essential Medium of Eagle, Ham F-12, RPMI 1640 and Iso-Sensitest broth (ISB) with and without surfactant (Tween 80) were investigated in vitro to assess tigecycline bactericidal activity. Clinical isolates of meticillin-resistant Staphylococcus aureus, meticillin-susceptible S. aureus, Escherichia coli, Klebsiella pneumoniae and Enterococcus spp., representing the majority of clinically relevant bacteria, were evaluated for the impact of test conditions on the tigecycline minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), ISB with 0.02% Tween 80 most efficiently demonstrated the bactericidal action of tigecycline when evaluated in 64 well-characterised clinical isolates and was considered as the optimal bactericidal test medium. Using this condition, tigecycline approached 56% bactericidal activity with 3log10 reduction in CFUs at 72h incubation. Bactericidal action increased to 80% of strains when 2log10 reduction was used as the endpoint. Only Enterococcus spp. showed no bactericidal response in this analysis. Tigecycline exhibited a bactericidal effect in vitro against Gram-positive and Gram-negative bacteria. At the tested in vitro conditions, tigecycline MICs were unchanged regardless of the different test media used.

Performance of the Cepheid Xpert® SA Nasal Complete PCR assay compared to culture for detection of methicillin-sensitive and methicillin-resistant Staphylococcus aureus colonization.

Sensitivity, specificity, positive predictive value, and negative predictive value for the Cepheid Xpert® SA Nasal Complete detection (N = 971) of methicillin-sensitive Staphylococcus aureus was 86.5%, 98.5%, 94.6%, and 96.1%; detection of methicillin-resistant S. aureus was 89.3%, 97.9%, 79.8%, and 99.0%, respectively. Our results show that testing on long-term care facility patients had lower sensitivity and specificity compared to acute care patient results.