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Pre-emptive isolation of suspected methicillin-resistant Staphylococcus aureus (MRSA) carriers is considered essential for controlling the spread of MRSA, but noncolonized patients will be isolated unnecessarily as a result of a delay in diagnosis of 3-5 days with conventional cultures. We determined costs per isolation day avoided, and incremental costs of rapid MRSA screening tests when added to conventional screening, but with decisions on isolation measures based on PCR results. A prospective multicentre study evaluating BD GeneOhm MRSA PCR (`IDI') (BD Diagnostics, San Diego, CA, USA), Xpert MRSA (`GeneXpert') (Cepheid, Sunnyvale, CA, USA) and chromogenic agar (MRSA-ID) (bioMérieux, Marcy-l'Etoile, France) was performed in 14 Dutch hospitals. Among 1764 patients at risk, MRSA prevalence was 3.3% (n=59). Duration of isolation was 19.7 and 16.1 h with IDI and GeneXpert, respectively, and would have been 30.0 and 76.2 h when based on chromogenic agar and conventional cultures, respectively. Negative predictive values (at a patient level) were 99.5%, 99.1% and 99.5% for IDI, GeneXpert and chromogenic agar, respectively. Numbers of isolation days were reduced by 60% and 47% with PCR-based and chromogenic agar-based screening, respectively. The cost per test was €56.22 for IDI, €69.62 for GeneXpert and €2.08 for chromogenic agar, and additional costs per extra isolation day were €26.34. Costs per isolation day avoided were €95.77 (IDI) and €125.43 (GeneXpert). PCR-based decision-making added €153.64 (IDI) and €193.84 (GeneXpert) per patient to overall costs and chromogenic testing would have saved €30.79 per patient. Rapid diagnostic testing safely reduces the number of unnecessary isolation days, but only chromogenic screening, and not PCR-based screening, can be considered as cost saving., (© 2010 The Authors. Journal Compilation © 2010 European Society of Clinical Microbiology and Infectious Diseases.)

A 59-year-old man was hospitalised because of dyspnoea, productive cough, fever, chills and malaise. Severe community-acquired pneumonia was diagnosed. Legionella urinary antigen testing, which can only detect serogroup 1, and the first culture ofa bronchoalveolar lavage (BAL) fluid sample were negative for Legionella. However, L. pneumophila DNA was detected by PCR in the BAL washing sample. Eventually, L. pneumophila serogroup 3 was isolated from this specimen by repeated culture. Although, in The Netherlands, legionellosis is caused by L. pneumophila serogroup 1 in more than 90% of all cases, this case demonstrates that a negative result of urinary antigen testing does not necessarily exclude this diagnosis. It is therefore advocated to expand the diagnostics to a Legionella PCR on respiratory material of patients with clinical signs of Legionella pneumonia in whom the urinary antigen test is negative.

During summer and fall, enterovirus infections are responsible for a considerable proportion of hospitalizations of young infants. We prospectively studied the incidence of enterovirus infections via real-time polymerase chain reaction (PCR) in blood, feces, and cerebrospinal fluid samples from infants

In this study we compared interphase fluorescence in situ hybridization (I-FISH) with reverse transcription polymerase chain reaction (RT-PCR) for the molecular analysis of hematopoietic colonies derived from patients with chronic myeloid leukemia (CML). Molecular analysis of individual colonies is often performed to monitor purging efficacy in CML. We harvested individual colony-forming unit granulocyte-macrophage (CFU-GM) colonies. One half was analyzed with I-FISH, for the presence of bcr-abl fusion gene. The other half was analyzed with RT-PCR for the presence of the bcr-abl mRNA. We wanted to address the following questions: (1) is the bcr-abl gene always expressed in CFU-GM colonies and (2) which technique has to be preferred to analyze individual CFU-GM colonies? In total, 133 colonies, derived from six CML patients, could be analyzed both with I-FISH and RT-PCR. We found a positive correlation in 89% of the cases: 118 colonies showed the same results with both techniques. However, 15 of the 106 I-FISH-positive colonies were negative in the RT-PCR. Serial analysis of the cDNA derived from 22 colonies showed in each round of amplification 21-29% RT-PCR-negative but I-FISH-positive colonies. However, all I-FISH-positive colonies showed at least one positive RT-PCR, either in the first, second or third round of amplification. These results indicate that the bcr-abl gene is probably always transcriptionally active in CFU-GM colonies. Reliable analysis with RT-PCR is possible but likely to generate false negative results. We conclude that: (1) I-FISH offers a reliable alternative to RT-PCR for analyzing individual hematopoietic colonies and (2) results obtained with RT-PCR should only be interpreted with caution. [ABSTRACT FROM AUTHOR]