Prevalence and clonality of methicillinresistant

Authors: T Conceição A Tavares M Miragaia K Hyde M AiresdeSousa H de Lencastre

Publish Date: 2010/03/13

Volume: 29, Issue: 5, Pages: 543-550

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Abstract

In order to obtain insights into the methicillinresistant Staphylococcus aureus MRSA population structure in the Azores archipelago 106 MRSA isolates were collected from patients attending an Azorean central hospital between January 2007 and February 2008 Antimicrobial resistance was determined for all isolates Molecular typing was performed by pulsedfield gel electrophoresis PFGE spa typing multilocus sequence typing MLST staphylococcal chromosome cassette mec SCCmec typing and the presence of Panton–Valentine leukocidin PVL The majority of the isolates 87 n = 92 belonged to the EMRSA15 clone ST22 SCCmecIVh followed by the Pediatric clone ST5VI/IVc 11 n = 12 The Berlin clone ST45IVa and a new clone spa type t1839 ST1339 and SCCmec V variant were represented by single isolates All of the isolates carried SCCmec types IV V or VI and a nonmultiresistant antibiotic profile resembling the currently emerging community MRSA Moreover PVL was described for the first time to be associated with the Pediatric clone carrying SCCmec type VI We provided the first description of the population structure of MRSA in the Azores islands which seems to be shaped by genetic events occurring locally as well as by the regular population exchange between the islands continental Portugal the United Kingdom and the United StatesMethicillinresistant Staphylococcus aureus MRSA is a major pathogen associated with both nosocomial and communityacquired infections hospitalacquired HA MRSA and CAMRSA respectively 1 MRSA are believed to have emerged by the acquisition of the staphylococcal cassette chromosome mec SCCmec the mobile genetic element carrying the determinant of methicillin resistance mecA into methicillinsusceptible S aureus MSSA Eight different SCCmec types I to VIII have been described so far in S aureus differing in their structure and size Epidemiological studies using molecular typing methods showed that the massive geographical spread of MRSA in hospitals results from the dissemination of a few highly epidemic clones These major epidemic clones resulted from a limited number of independent acquisitions of SCCmec into welldefined genetic backgrounds i New York/Japan clone sequence type ST 5 SCCmec II ii Pediatric clone ST5IV/VI iii Brazilian clone ST239III/IIIA iv Iberian clone ST247IA v EMRSA15 ST22IV vi EMRSA16 ST36II and vii Berlin clone ST45IV 2 3 4The MRSA prevalence in European hospitals varies from less than 30 in the Nordic Countries and The Netherlands to over 50 in southern European countries and the United Kingdom Despite the significant decrease in MRSA incidence in a few countries France Slovenia Belgium Cyprus and Turkey due to improved infection control the incidence has increased in other countries including Portugal where the MRSA proportion is nowadays over 50 being one of the highest in Europe 1 5Surveillance studies have been conducted in Portugal since the early 1990s showing temporal waves of MRSA clonal prevalence In the most recent survey conducted in 2006 EMRSA15 ST22IVh was found to be the most prevalent clone in Portuguese hospitals followed by the New York/Japan clone ST5II 5 6Information about the epidemiology of CAMRSA is still scarce and nonexistent in Portugal Unlike HAMRSA CAMRSA are usually only resistant to betalactams and one or two additional antimicrobial classes and carry mainly SCCmec types IV and V the smallest in size which are believed to be more mobile CAMRSA frequently harbour Panton–Valentine leukocidin PVL but the toxin has also been detected in the hospital environment 7 8 Similarly to HAMRSA CAMRSA epidemic clones have been described 9 However a much larger genetic diversity in the genetic backgrounds of CAMRSA has been observed suggesting a high number of SCCmec acquisitions in the community Recent data indicates that MRSA epidemiology is suffering a new change and that the boundaries between the hospital and the community are blurring As a result clones traditionally linked to the hospital like the EMRSA15 clone were found to be aetiologic agents of infection in the community 10 and clones specific to the community were observed as causing infections in hospitals as is the case of the USA300 strain 11 12 A common trait to these clones that can survive in both environments appears to be the presence of SCCmec type IV that is nowadays prevalent among the current overall MRSA population 5 6 13 14 15Hospital do Divino Espírito Santo HDES is a 390bed central hospital located in Ponta Delgada São Miguel island that services an outpatient population of 138000 inhabitants from the two most populous Azorean islands S Miguel and Santa Maria The hospital the largest in the archipelago includes medicine and surgery as principal wards and a large outpatient ambulatory unit

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