Methicillin-resistant Staphylococcus aureus in swine housed indoors in Galicia, Spain

Abstract

Introduction

Livestock are known reservoirs of methicillin-resistant Staphylococcus aureus (MRSA) and this constitutes an important public health issue. The prevalence of nasal MRSA carriers in swine housed indoors in Galicia, Spain, was studied.

Methods

197 samples from swine aged three, eight, 12, 16 and 24 weeks, and from adult pigs, were obtained from four farms. The cleaning procedures implemented to clean the barns and antimicrobial consumption were analyzed. Antimicrobial susceptibility and antimicrobial resistance genes were studied. PFGE, spa typing and MLST were used to classify the isolates. SCCmec, agr and pvl were analyzed.

Results

MRSA prevalence was 12.7%. Swine younger than 16 weeks had a higher colonization rate; 22.9% vs 3.5% (OR, 8.16; 95% CI, 2.47–29.79; p < 0.01). The only farm found to be MRSA-free used disinfectants as part of its cleaning procedure. All MRSA were tetracycline-resistant (identifying the tetK and tetM genes), 80% were resistant to erythromycin and clindamycin and 16% were only clindamycin-resistant. The ermC and vgaA genes were identified in these two phenotypes. A single genotype (PFGE type A) and ST398 – spa t011 (84%) and t1451 (16%) were identified. SCCmec type V and agrI were identified in all isolates, and all were pvl-negative.

Conclusion

A correlation between swine age and MRSA colonization was observed. Appropriate cleaning procedures could have an impact on MRSA colonization in farming. Resistance to antibiotics used in human health was identified. Clinicians should be aware if their patients have come into contact with farm animals.

Resumen

Introducción

Los animales de granja son reservorios de Staphylococcus aureus resistente a la meticilina (SARM), y constituyen un problema de salud pública. Se estudia la prevalencia de portadores nasales de SARM en cerdos estabulados en Galicia, España.

Métodos

En 4 explotaciones se obtuvieron 197 muestras de cerdos con edades en semanas de 3, 8, 12, 16, 24 y adultos. Se analizaron los métodos empleados para limpiar los establos y el consumo de antimicrobianos. Se estudió la resistencia a antimicrobianos, y los genes involucrados en esta. Los aislamientos fueron clasificados mediante PFGE, spa y MLST. Se analizaron SCCmec, agr y pvl.

Resultados

La prevalencia de SARM fue del 12,7%. Los cerdos de < 16 semanas presentaron las frecuencias de colonización más elevadas 22,9 vs. 3,5% (OR: 8,16; IC 95%: 2,47-29,79; p < 0,01). En la única explotación libre de SARM se empleaban desinfectantes en la limpieza. Todos los SARM fueron resistentes a tetraciclina identificándose los genes tetK y tetM, el 80% fueron resistentes a eritromicina y clindamicina, y el 16% fueron únicamente resistentes a clindamicina. Se identificaron los genes ermC y vgaA en estos 2 fenotipos. Se identificó un único genotipo (PFGE-A) y ST398, siendo spa t011 (84%) y t1451 (16%). En todos los aislamientos se identificó SCCmec V y agrI, siendo estos pvl negativos.

Conclusiones

Se observó la asociación entre edad y colonización SARM. La limpieza adecuada podría modificar la colonización por SARM. Se detectaron resistencias a antibióticos empleados en humanos. Los médicos deberían conocer si los pacientes tienen contacto con animales de granja.