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Open Access Research article

Livestock-associated methicillin-resistant Staphylococcus aureus responsible for human colonization and infection in an area of Italy with high density of pig farming

Monica Monaco1*, Palmino Pedroni2, Andrea Sanchini134, Annalisa Bonomini2, Annamaria Indelicato2 and Annalisa Pantosti1

Author affiliations

1 Department of Infectious, Parasitic and Immuno-mediated Diseases, Istituto Superiore di Sanità, viale Regina Elena, 299, Rome, Italy

2 Presidio Ospedaliero Manerbio-Leno, Azienda Ospedaliera Desenzano del Garda, Lungomella Valsecchi, Brescia, Italy

3 Present address: Robert Koch-Institut (ZBS 1), Nordufer 20 D-13353 Berlin-Wedding, Berlin, Germany

4 Present address: European Public Health Microbiology Training Programme (EUPHEM), European Centre for Disease Prevention and Control (ECDC), Tomtebodavägen 11a, 171 83, Stockholm, Sweden

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Citation and License

BMC Infectious Diseases 2013, 13:258  doi:10.1186/1471-2334-13-258

Published: 3 June 2013

Abstract

Background

Livestock-Associated MRSA (LA-MRSA) belonging to ST398 lineage, common among pigs and other animals, emerged in Central and Northern Europe, becoming a new risk factor for MRSA among farm workers. Strains belonging to ST398 can be responsible for human colonization and infection, mainly in areas with high livestock-farming. The aim of this study was to investigate the occurrence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) human colonization and infections in an area of the Lombardy Region (Italy), the Italian region with the highest density of pig farming.

Methods

In the period March-April 2010, 879 nasal swabs were taken from subjects at admission to a local hospital serving an area of the Lombardy Region devoted to agriculture and farming. In the period March 2010-February 2011, all MRSA strains from community-acquired infection (CAI) observed in the same hospital, were collected. Molecular characterization of the isolates included SCCmec typing, spa typing and multilocus sequence typing (MLST).

Results

Out of 879 nasal swabs examined, 9 (1%) yielded MRSA. Five strains were assigned to sequence type (ST)398 (spa t899, 3 isolates; t108 and t2922, 1 isolate each) and were therefore categorized as LA-MRSA. The other 4 isolates were likely of hospital origin. No strains were positive for Panton-Valentine Leukocidin genes. Twenty MRSA isolates were detected from CAI, 17 were from skin and soft-tissue infections and 3 from other infections. An MRSA isolate from otitis externa was t899/ST398 and PVL-negative, hence categorized as LA-MRSA. Four isolates were assigned to t127/ST1. Eight strains were PVL-positive community acquired (CA)-MRSA and belonged to different clones, the most frequent being ST8.

Conclusions

In an area of Italy with high density of pig farming, LA-MRSA is able to colonize the population and rarely to produce infections. Typical CA-MRSA is more common than LA-MRSA among CAI.

Keywords:
Livestock-associated (LA)-MRSA; Colonization, Community-acquired infections; Pigs; ST398