Abstract

BackgroundThe emergence of livestock-associated MRSA has become a growing public health concern worldwide. Studies elucidating the population structure, as well as resistance phenotypes and virulence gene profiles of livestock-associated MRSA strains are needed to improve risk assessment and to develop effective control measures. The objective of this study therefore was to determine i) clonal complexes and spa types, as well as ii) resistance phenotypes and iii) virulence and resistance gene profiles of livestock-associated MRSA isolated from Finnish fattening pigs at slaughter.MethodsFifty MRSA isolates collected from Finnish fattening pigs at slaughter were characterized by spa typing and DNA microarray profiling. In addition, antimicrobial susceptibility testing was performed using the Kirby Bauer disk diffusion method.ResultsMRSA isolates were assigned to clonal complexes CC1 (n = 4) and CC398 (n = 46). One dominant spa type (t2741) was present in 33 out of 50 investigated isolates, originating from 15 out of 18 farms. The remaining isolates were assigned to spa types t034 (n = 7), t108 (n = 5), and t011 (n = 1). Although each herd exhibited isolates assigned to one clonal complex only, five herds harbored MRSA isolates of either two or three different spa types. All tested MRSA isolates were phenotypically resistant to penicillin, oxacillin, cefoxitin, and tetracycline. With the exception of the isolates assigned to t108, all isolates exhibited resistance to clindamycin. On the genomic level, all isolates exhibited mecA, blaZ/I/R, and tetK, and were assigned to SCCmec type V. Many isolates also harbored tetM (46/50 isolates), lnuB (41/50 isolates), ermB (26/50 isolates), and one isolate was positive for aadD. DNA microarray profiling showed that all isolates of the dominant CC398/t2741 MRSA-V type belonged to agr type I, capsule type 5, and were negative for fnbB. Interestingly, one isolate of CC398/t2741 MRSA-V was agr negative and also lacked hld.ConclusionsA new dominant LA-MRSA clone (CC398/t2741, SCCmec type V) was identified among fattening pigs in Finland. This is the first study identifying t2741 as a common spa type in LA-MRSA in pigs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13756-016-0105-8) contains supplementary material, which is available to authorized users.

Highlights

  • The emergence of livestock-associated Methicillin-resistant Staphylococcus aureus (MRSA) has become a growing public health concern worldwide

  • This study aimed to determine i) clonal complexes and spa types, as well as ii) resistance phenotypes and iii) virulence and resistance gene profiles of LA-MRSA isolated from Finnish fattening pigs at slaughter

  • The 50 MRSA isolates were assigned to clonal complexes CC1 (n = 4) and CC398 (n = 46), comprising isolates of highly similar resistance and virulence gene profiles (Fig. 1)

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Summary

Introduction

The emergence of livestock-associated MRSA has become a growing public health concern worldwide. Studies elucidating the population structure, as well as resistance phenotypes and virulence gene profiles of livestockassociated MRSA strains are needed to improve risk assessment and to develop effective control measures. The objective of this study was to determine i) clonal complexes and spa types, as well as ii) resistance phenotypes and iii) virulence and resistance gene profiles of livestock-associated MRSA isolated from Finnish fattening pigs at slaughter. LA-MRSA are mostly associated with clonal complex CC398 and can be found at especially high prevalence rates in pigs [3,4,5,6]. Data on the prevalence and population structure of Finnish LA-MRSA isolates from pigs is extremely limited. Seven porcine CC398 isolates obtained in 2008 and 2009 were typed and were exclusively assigned to spa type t108 [7]

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