Genetic diversity and antimicrobial resistance of Staphylococcus hyicus isolated from sows with purulent vulvar discharge
Published:January 19, 2022
By:André P. Poor 1, Luisa Z. Moreno 1, Carlos E. C .Matajira 1, Matheus S. Monteiro 1, Maurício C. Dutra 1, Andressa C. Dalmutt 1, Beatriz M. Parra 1, Vasco T. M. Gomez 1, Ana P. S. Silva 1, Andrea M. Moreno 1 / 1 Faculdade de Medicina Veterinária e Zootecnia– Universidade de Sao Paulo (USP) – Sao Paulo, SP – Brazil.
Introduction
Vulvar discharges are related to reproductive tract infections that can lead to decreased sow fertility and other impairments in zootechnical indices, which reduces profitability1,2,3. However, knowledge about metrite causative agents in sows is still very superficial. Staphylococcus hyicus – a Gram-positive, coagulase variable, facultative anaerobic, catalase-positive, non-hemolytic, non-motile bacteria - may be able to cause metritis in sows4, but there is still little information on the genetic behavior and antimicrobial resistance patterns of this agent in Brazilian farms. Thus, in this work strains isolated from sows with purulent vulvar discharge were identified and analyzed for their genetic diversity. Also, the minimal inhibitory concentration (MIC) for various antimicrobials used in pig farming was determined for all strains.
Materials and Methods
Results and discussion
A total of 38 (19,1%) sows were positive for isolation of S. hyicus. The SE-AFLP enabled the formation of 15 profiles (B1-B15) with at least 90% of genetic similarity. B1 is the largest profile, containing 26.3% (10/38) of the samples and with strains from three herds. Its evident the high heterogeneity of S. hyicus strains, even within animals from the same herd. Due to this high heterogeneity, there is no clear association of these profiles with other epidemiological variables such as origin of strains, parity order, phase of the cycle, year or MIC profile. Low genetic similarity between S. hyicus strains was also found in another study5.
High resistance levels were detected among the strains analyzed (Table 1). All strains were resistant to spectinomycin, clindamycin and tiamulin. Most strains were also resistant to quinolones, tetracyclines, beta-lactams and sulfadimethoxine, while the antimicrobials with best action against the strains were ceftiofur, gentamicin and sulfonamide/trimethoprim. However, all strains can be classified as multidrug-resistant. Similar results were found by Wegener et al. (1994) for spectinomycin, tetracyclines, penicillin and ceftiofur, but not for fluorquinolones6. One possible explanation for the increased resistance would be the intense use of these antimicrobials in Brazilian herds, which are under high selection pressure by these drugs.
Conclusions
Staphylococcus hyicus was found in a considerable portion of the sampled females with vulvar discharge and presented high genotypic diversity. Other genetic elements that may explain this heterogeneity have yet to be researched, such as virulence genes. Furthermore, the strains also presented high and alarming resistance levels to the main antimicrobials used in pork production, showing that S. hyicus cannot be neglected in reproductive infections of sows.
Acknowledgements The authors would like to acknowledge the financial support provided by São Paulo Research Foundation (FAPESP grant 2017/09515-4 and 2019/01192-7).
References
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