The purpose of this study was to evaluate the impact of the emergence of animal related methicillin resistant Staphylococcus aureus ST398 in an area with a high density of pig farms. A retrospective analysis was performed of all MRSA isolates in the laboratory database . This is a 925% increase of which 82% (108/132) was due to ST398. The majority (74%) came from targeted screening but 7% was due to unexpected findings. A wide range of infections with ST398 occurred in patients with and without contact with livestock varying from post-operative wound infections to sepsis and post-trauma osteomyelitis with an overrepresentation of spa type t567 among the clinical isolates. ST398 isolates were more often multi-resistant than isolates of other spa-types. The emergence of MRSA ST398 led to an increase in both MRSA carriers and MRSA infections.
Moraxella catarrhalis is a bacterial species that has been implicated in 15^20% of all cases of otitis media in the USA and the complementresistant variant of M. catarrhalis has been considered particularly pathogenic. A collection of geographically diverse, complement-sensitive (n = 28) and -resistant strains (n = 47) of M. catarrhalis was assembled in order to analyse the bacterial population structure. All strains were identified as M. catarrhalis by conventional microbiological and biochemical methods. Amplification of the small subunit (ssu) ribosomal RNA gene followed by restriction fragment length polymorphism (RFLP) analysis did not reveal consistent differences between serumsusceptible and -resistant M. catarrhalis isolates. Interestingly, upon automated ribotyping using the Qualicon RiboPrinter0 microbial characterisation system, the complement-sensitive and -resistant strains segregated into two groups. This suggested the existence of two clearly distinguishable lineages within the species M. catarrhalis. This observation was corroborated by pulsed field gel electrophoresis (PFGE) of DNA macro-restriction fragments, a non-ribosomal PCR RFLP procedure and random amplification of polymorphic DNA (RAPD) analysis. All procedures grouped the two variants similarly. Redefinition of the taxonomic status of complement-resistant M. catarrhalis or even the definition of a new species may be opportune. ß
In order to perform a cost-effective search and destroy policy for methicillin-resistant Staphylococcus aureus (MRSA), a quick and reliable typing method is essential. In an area with a high level of animal-related MRSA ST398, pulsed field gel electrophoresis (PFGE) typing and spa-typing are not sufficient to discriminate between co-incidental findings and true transmission of MRSA. This study is the first to retrospectively show the performance of Raman spectroscopy in 16 well-documented outbreaks. We analysed 525 isolates, 286 MRSA ST398 and 239 from other PFGE clusters with Raman spectroscopy. When epidemiologically linked isolates from the outbreaks were analysed with PFGE as the reference standard, Raman spectroscopy correctly identified 97% of cases that were indistinguishable from the index case. With Raman cluster analysis, the most dominant distinction was between MRSA ST398 and other MRSA of human clonal lineages. Within MRSA ST398, 22 different Raman clusters were identified. Raman typing correctly identified an ST398 (spa type t567) outbreak in a hospital setting. No direct correlation was observed between Raman clusters and spa types. We conclude that Raman spectroscopy is a quick and reliable method of MRSA typing, which can be used in outbreak settings and it is comparable to PFGE, with the added advantage that PFGE non-typeable isolates can also be readily typed using the same sample preparation protocol.
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