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Abstract Background MRSA is a significant contributor to prolonged hospital stay, poor clinical outcome and increased healthcare costs amongst surgical patients. A PCR test has been developed for rapid detection of MRSA in nasal swabs. The aims of this study are (1) to estimate the effectiveness of screening using this rapid PCR tests vs culture in reducing MRSA cross-infection rates; (2) to compare the cost of each testing strategy, including subsequent health care costs; and (3) to model different policies for the early identification and control of MRSA infection in surgical patients. Methods/Design The study is a prospective two-period cross-over study set in 7 surgical wards covering different surgical specialities. A total of 10,000 patients > 18 years will be tested over 16 months. The only difference between the two study periods is the method used for the detection of MRSA in each ward (rapid v conventional culture), with all other infection control practices remaining consistent between the arms. The study has been designed to complement routine practice in the NHS. Outcomes are MRSA cross-infection rates (primary outcome) and need for antibiotic therapy and MRSA-related morbidity. Parallel economic and modelling studies are being conducted to aid in the interpretation of the results and to evaluate the cost-effectiveness of the rapid PCR screening strategy. Discussion This paper highlights the design, methods and operational aspects of a study evaluating rapid MRSA screening in the surgical ward setting.

The early identification of outbreaks is crucial for the control of Clostridium difficile infection. This study aimed to determine if the number of hospital-acquired C. difficile infections could be reduced by rapidly typing C. difficile strains using multiple-locus variable-number tandem-repeat analysis (MLVA) compared to typing using PCR ribotyping. A total of 16 hospitals were recruited to the study, and all periods of increased incidence (PIIs) of C. difficile infection were identified. The hospitals were randomized into two study arms, the test and the control, with all isolates typed in the test using MLVA and in the control using PCR ribotyping. Following a PII, each hospital received a structured questionnaire regarding control measures implemented or stopped prior to or following the typing results. During the study period, there were a total of 1,682 hospital-apportioned C. difficile toxin-positive cases, with 868 in the control and 814 in the test, with modeling demonstrating no differences between the two arms. A total of 245 PIIs occurred, involving 785 patients. There was a significant difference in the mean turnaround time between the ribotyping and MLVA typing (13.6 and 5.3 days, respectively [P < 0.001]). The discriminatory ability of MLVA was greater than ribotyping, with 85 outbreaks being confirmed by ribotyping and 62 by MLVA. In the test arm, 40.6% of respondents strongly agreed that the typing result had aided their management of clusters, as opposed to 9.9% in the control. The study demonstrated the utility of rapidly typing C. difficile strains, demonstrating that it aided the management of clusters, enabling effective targeting of infection control resources.

A novel multiplex PCR assay is described (CTX-Mplex PCR) that allows rapid detection of bla(CTX-M) genes and discrimination between groups 1, 2, 9 and 25/26. The specificity and sensitivity of the assay were evaluated with 10 control strains and then applied to 62 clinical isolates. The multiplex PCR detected and classified bla(CTX-M) genes with 100 % accuracy. The utilization of a denaturing HPLC WAVE system to size the PCR products automatically from the multiplex PCR enhances the assay by saving time and costs.