Evaluation of the TPX MRSA assay for the detection of methicillin-resistant Staphylococcus aureus.

The aim of this study was to evaluate a new type of assay for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). The assay is based on a point-of-care compatible two-photon excitation fluorescence detection technology (TPX). A collection of 243 epidemic MRSA isolates was tested in addition to 138 sporadic MRSA and 101 negative control strains. The assay proved to be both sensitive (97.9%) and specific (94.1%) in the identification of MRSA, with adequate positive (98.4%) and negative (92.2%) predictive values. The time required for obtaining a positive test result was less than 14 h for 99.0% of the MRSA true-positive samples. After a test run, the selectively enriched reaction mixtures may be recovered and further studied by molecular or standard phenotypic methods. The main benefits of the TPX methodology include a simple assay procedure, low reagent consumption, and a high-throughput capacity.

Prevalence of pilus-encoding islets and clonality of pneumococcal isolates from children with acute otitis media.

We characterized the prevalence of pilus islets 1 (PI-1) and 2 (PI-2) and the clonality of Streptococcus pneumoniae isolates taken from children with acute otitis media (AOM) to study the association between pilus existence and AOM disease potential prior to pneumococcal conjugate vaccine and increased antimicrobial resistance. The study material consisted of 75 pneumococcal isolates cultured from the middle ear fluid and/or nasopharyngeal aspirate of 56 children with AOM in Finland during the period 1990-1992. Isolates were studied for antimicrobial susceptibility and were serotyped, genotyped by multilocus sequence typing (MLST), and tested for the presence of pneumococcal PI-1 and PI-2 genes. All isolates were susceptible to penicillin, 14 different serotypes were found, and 20% of the isolates were positive for PI-1 genes. PI-2 genes were not found. MLST showed high heterogeneity: 52 AOM isolates belonged to 18 known clonal complexes (CC). PI-1 was associated with serotypes 6A, 6B, and 9V, and genotype CC490. In the time prior to 7-valent pneumococcal conjugate vaccine (PCV7) and increased antimicrobial resistance, pneumococcal AOM isolates carried PI-1 genes at a rather low prevalence. PI-2 genes were not detected. PI-1 was related to serotype rather than genotype. The importance of PI-1 in AOM infections and its association with the spread of antimicrobial resistance requires further research.

First isolations of KPC-2-carrying ST258 Klebsiella pneumoniae strains in Finland, June and August 2009.

The first two Klebsiella pneumoniae carbapenemase-producing (KPC) type 2 strains carrying ST258 were detected in Finland in June and early August 2009. They were found colonising two patients transferred from the Mediterranean; one patient referred from a hospital in Greece where isolates were first found in 2007 and another from Italy where the first isolates have been described only very recently.