Multilaboratory study of the Biomic automated well-reading instrument versus MicroScan WalkAway for reading MicroScan antimicrobial susceptibility and identification panels.

This study compared the Biomic automated well reader results to the MicroScan WalkAway results for reading MicroScan antimicrobial susceptibility and identification panels at four different sites. Routine fresh clinical isolates and quality control (QC) organisms were tested at each study site. A total of 46,176 MicroScan panel drug-organism combinations were read. The Biomic category agreement for 3,117 Gram-negative bacteria was 98.4%, with 1.4% minor and 0.2% major discrepancies. The Biomic category agreement for 5,233 Gram-positive bacteria was 98.7%, with 0.9% minor, 0.3% major, and 0.1% very major errors. Essential agreement, defined as Biomic results that were within ±1 2-fold dilution of the MicroScan results, was 99.3% for Gram-negative bacteria and 98.3% for Gram-positive bacteria. Biomic reading of MicroScan identification panels provided an overall agreement (first- and second-choice organism match) of 99.5% with 846 Gram-negative isolates and 99.5% with 430 Gram-positive isolates. These results suggest that the Biomic automated reader can provide accurate reading of MicroScan panels and has the capability of a visual panel read for manual adjustment of results.

Multicenter evaluation of the LightCycler MRSA advanced test, the Xpert MRSA Assay, and MRSASelect directly plated culture with simulated workflow comparison for the detection of methicillin-resistant Staphylococcus aureus in nasal swabs.

Rapid detection of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) followed by appropriate infection control procedures reduces MRSA infection and transmission. We compared the performance and workflow of two Food and Drug Administration-approved nucleic acid amplification assays, the LightCycler MRSA Advanced Test and the Xpert MRSA test, with those of directly plated culture (MRSASelect) using 1202 nasal swabs collected at three U.S. sites. The sensitivity of the LightCycler test (95.2%; 95% CI, 89.1% to 98.4%) and Xpert assay (99%; 95% CI, 94.8% to 100%) did not differ compared with that of culture; the specificity of the two assays was identical (95.5%; 95% CI, 94.1% to 96.7%) compared with culture. However, sequencing performed on 71 samples with discordant results among the three methods confirmed the presence of MRSA in 40% of samples that were positive by both molecular methods but negative by culture. Workflow analysis from all sites including batch runs revealed average hands-on sample preparation times of 1.40, 2.35, and 1.44 minutes per sample for the LightCycler, Xpert, and MRSASelect methods, respectively. Discrete event simulation analysis of workflow efficiencies revealed that the LightCycler test used less hands-on time for the assay when greater than eight batched samples were run. The high sensitivity and specificity, low hands-on time, and efficiency gains using batching capabilities make the LightCycler test suitable for rapid batch screening of MRSA colonization.

Pharmacokinetics of topical and intravenous cefazolin in patients with clean surgical wounds.

BACKGROUND: Surgical-site infection is a common postoperative nosocomial infection. Surgeons frequently treat operative patients with protective antibiotics and often choose cefazolin as the drug. Treatment schemes include both preoperative intravenous dosing and intraoperative dosing by irrigation. This study was designed to measure cefazolin concentrations both in serum and in wound drain fluid after intravenous dosing and after irrigation. METHODS: The authors conducted an institutional review board-approved study involving randomized allocation of breast reduction patients to group 1 (preoperative intravenous dosing) or group 2 (intraoperative dosing by irrigation). Each patient had serum and wound drainage specimens measured over time for cefazolin concentrations. Cefazolin dosing was based on preparations commonly used in the authors' hospital. Results from 24 patients are reported. RESULTS: Patients treated by conventional preoperative intravenous dosing displayed the expected serum degradation curve. These patients also demonstrated wound drainage concentrations (peak, 22.49 microg/ml) for approximately 4 to 5 hours. Measured concentrations were above the minimum therapeutic concentration (8 microg/ml) for Staphylococcus aureus. Patients treated by wound irrigation also demonstrated serum concentrations above minimum therapeutic concentration. In addition, these patients' wound drain fluid demonstrated very high cefazolin concentrations (peak, 4185.93 microg/ml), which remained high for 24 hours. CONCLUSIONS: Protective cefazolin concentrations in the wound can be achieved by both intravenous and irrigation delivery. Wound irrigation produces higher concentrations for longer periods of time.

Comparison of the Binax NOW Flu A enzyme immunochromatographic assay and R-Mix shell vial culture for the 2003-2004 influenza season.

The Binax NOW Flu A enzyme immunochromatographic assay was compared to viral culture with R-Mix shell vials for 455 nasal-wash or nasal-aspirate specimens. The overall sensitivity, specificity, positive predictive value, and negative predictive value of the assay were 64.9%, 98.4%, 89.3%, and 93.2%, respectively. However, the assay sensitivity decreased significantly with increasing patient age.

Delayed-onset mycobacterial keratitis after LASIK.

PURPOSE: To describe the time course, diagnosis, clinical features, and treatment of seven patients with Mycobacterium szulgai keratitis that developed from 7 to 24 weeks after laser in situ keratomileusis (LASIK). METHODS: Seven of 30 eyes of 18 patients were identified with keratitis after LASIK. The first two patients presented 12 to 14 weeks after LASIK; nontuberculous mycobacteria were identified 1 month after the flaps were cultured. Patient recall identified three additional cases by culture and two cases by clinical features alone. Pulsed-field gel electrophoresis (PFGE) was used to type the isolates, and treatment was modified based on susceptibilities. RESULTS: M. szulgai was identified in five patients for whom cultures were performed, but response to empiric therapy based on cultures proved unsatisfactory. The keratitis resolved in all patients with treatment including clarithromycin based on susceptibilities. Medical therapy was sufficient, although one patient required flap amputation. Six of seven patients recovered best-corrected visual acuity (BCVA), while one patient lost one line of BCVA. Two patients lost one line of postoperative uncorrected visual acuity (UCVA), two patients gained one line of UCVA, and three patients recovered postoperative UCVA. PFGE analysis revealed that the M. szulgai strains were identical, and the infection source was contaminated ice used to chill syringes for saline lavage. CONCLUSIONS: Nontuberculous mycobacterial keratitis after LASIK is a diagnostic and management challenge, but outcomes can be preserved with treatment based on susceptibilities. This cluster underscores the importance of adherence to sterile protocol during LASIK.

A Cluster of cases of Mycobacterium szulgai keratitis that occurred after laser-assisted in situ keratomileusis.

Laser-assisted in situ keratomileusis (LASIK) is a recently developed ophthalmic procedure. When 2 patients developed keratitis caused by Mycobacterium szulgai after they underwent LASIK surgery, we conducted a retrospective cohort study of all LASIK procedures performed at Scott & White Clinic (Temple, Texas) during a 4.5-month period. Seven patients had compatible symptoms and signs, 5 of whom had confirmed M. szulgai keratitis. Five cases occurred among 30 procedures performed by doctor A, and there were no cases among 62 procedures performed by doctor B (approximate relative risk, 12.0; 95% confidence interval, 1.6-679.0; P=.0029). Doctor A had chilled syringes of saline solution in ice for intraoperative lavage-the only factor that differentiated the procedures of the 2 surgeons. Cultures of samples from the source ice machine's drain identified M. szulgai; the strain was identical to isolates recovered from all confirmed cases and differed from 4 standard M. szulgai strains, as determined by pulsed-field gel electrophoresis. Intraoperative contamination from ice water apparently led to M. szulgai keratitis in these patients.