Original articleMethicillin-resistant Staphylococcus aureus in swine housed indoors in Galicia, SpainStaphylococcus aureus resistente a la meticilina en cerdos estabulados en Galicia, España
Introduction
In 2005 a methicillin-resistant Staphylococcus aureus (MRSA) strain associated with pig farming was identified in France and The Netherlands.1, 2 The MRSA strain belonged to sequence type (ST) 398 clone which has also been further identified in animals and humans worldwide.3, 4, 5, 6 Indeed, 20% of all MRSA identified in humans in The Netherlands belonged to the ST398, documenting the importance of considering livestock and other animals when studying the epidemiology of MRSA.7
Spain is the fourth porcine producer in the world and the second in Europe behind Germany.8 The current information about MRSA colonization in live swine in Spain is scarce. Porrero et al.9 studied the MRSA epidemiology in free living Iberian pigs and Reynaga et al.3 studied MRSA colonization in farm pigs. Other Spanish studies were done in slaughter pigs10 and food samples.11 Nevertheless, pigs could have become MRSA colonized during transportation from farm to slaughterhouse12 not representing the real farm prevalence.
In 2006, ST398 MRSA was first isolated from patients with different infections in our hospital.13 We concluded that the ST398 clone was part of the MRSA population in Galician region (Spain), hypothesizing that pigs could be a potential reservoir of MRSA from a public health perspective.
The aim of this study was to determine the prevalence of nasal MRSA carriage in live swine hosted in indoor production systems in Galician region, Spain. The isolates were genetically classified and the antimicrobial resistance was studied. The cleaning procedures used in each of the studied farms were questioned.
Section snippets
Farms description
The four sampled farms were located in an area of 80 km2 in Galicia (Spain). From March to April 2010 we collected a total of 197 nasal swabs from two farrow-to-rearing farms (farms A and B, pigs were up to 8 weeks), a rearing farm (farm C; 8–24 weeks, at the moment of the study the pigs were 16 weeks), and a farrow-to-finish farm (farm D; 90 sows, 140 piglets 3 weeks old, 170 grower pigs 12–24 weeks old). The sample comprised 28 piglets 3 weeks old, 45 weaned piglets 8 weeks old, 10 grower pigs
Detection of MRSA in the studied samples, cleaning procedures used, pig's origin, and antimicrobial consumption
Nasal swabs were taken from 197 swine hosted in four farms representing 6 different age groups (Table 1). The overall prevalence was 12.7% (n = 25). Swine younger than 16 weeks old had higher odds of MRSA colonization 22.9 vs 3.5% (OR, 8.16; 95% CI, 2.47–29.79; p < 0.01, Chi square test) when compared to swine older than 16 weeks. No MRSA was isolated in the farm C where all the pigs were 16 weeks old.
The cleaning procedure used in farm C included farm emptying, wash using high-pressure water,
Discussion
Galicia is one of the western regions in the European Union. The overall prevalence of MRSA carriage in pigs (12.7%) was lower to the one reported by other series.3, 4, 5, 26 Remarkably, no MRSA was identified in farm C were all pigs were 16 weeks old. In this production, pigs were hosted for four months before being delivered for consumption. Once the facility was totally emptied, an intensive cleaning procedure was always performed with cheap products like water, bleach and quicklime
Sources of financing
This work was financed by grants from Fondo de Investigaciones Sanitarias and Fondo Europeo para el Desarrollo Regional (FEDER) (07-0812) and Consejería de Sanidad de La Junta de Galicia (PS08/34).
Conflict of interest
The authors declare that there are not any conflicts of interest of any nature.
This work was partially presented at the 21st European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) Milan, Italy.
Acknowledgments
We are grateful to farm workers and veterinarians for their help.
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