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 profitability^1,2,3. 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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2. WALLER et al. Effect of periparturient diseases accompanied by excessive vulval discharge and weaning to mating interval on sow reproductive performance. Aust Vet J, 80:545–549, 2002.

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4. de WINTER et al. Bacterial endometritis and vaginal discharge in the sow: prevalence of different bacterial species and experimental reproduction of the syndrome. Anim Reprod Sci 37:325–335, 1995.

5. PIESSENS et al. Validation of amplified fragment length polymorphism genotyping for species identification of bovine associated coagulase-negative staphylococci. J Microbiol Methods 80:287–294, 2010.

6. WEGENER et al. Antimicrobial susceptibility of Staphylococcus hyicus isolated from exudative epidermitis in pigs. J Clin Microbiol 32:793–795, 1994.