Epidemiology and antimicrobial resistance of methicillin-resistant Staphylococcus aureus isolates colonizing pigs with different exposure to antibiotics

Autoři: Elizeth Lopes aff001;  Teresa Conceição aff001;  Laurent Poirel aff002;  Hermínia de Lencastre aff001;  Marta Aires-de-Sousa aff001
Působiště autorů: Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal aff001;  Emerging Antibiotic Resistance Unit, Medical and Molecular Microbiology, Department of Medicine, University of Fribourg, Fribourg, Switzerland aff002;  French INSERM European Unit, University of Fribourg (LEA-IAME), Fribourg, Switzerland aff003;  National Reference Center for Emerging Antibiotic Resistance, Fribourg, Switzerland aff004;  Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, New York, United States of America aff005;  Escola Superior de Saúde da Cruz Vermelha Portuguesa, Lisbon, Portugal aff006
Vyšlo v časopise: PLoS ONE 14(11)
Kategorie: Research Article
doi: 10.1371/journal.pone.0225497



In 2016, very high rates of methicillin-resistant Staphylococcus aureus (MRSA)-ST398 (99%) were found in Portuguese pig farms that used colistin, amoxicillin, and zinc oxide as feed additives. Since then, farms A and B banned the use of colistin, and farm C banned the use of both antibiotics.


The aim of the present study was to evaluate the impact of the ban of colistin and amoxicillin on pig MRSA carriage rates, clonal types and antimicrobial resistance, compared to the results obtained in 2016.


In 2018, 103 pigs (52 from farm B using amoxicillin only as a feed additive and 51 from farm C where no antibiotics were included in the feed regimen) were nasally swabbed for MRSA colonization. Isolates were tested for antimicrobial susceptibility, and characterised by spa typing, SCCmec typing and MLST. Whole genome sequencing (WGS) was performed for representative isolates.


Overall, 96% of the pigs swabbed in 2018 carried MRSA, mostly ST398-SCCmec V-spa types t011/t108. MRSA from pigs not receiving antibiotics in the feed regimen showed susceptibility to a higher number of antibiotics, namely erythromycin, ciprofloxacin, gentamicin, and chloramphenicol. Notably, most of these isolates (n = 52) presented an unusual erythromycin-susceptibility/clindamycin-resistance phenotype. WGS showed that these isolates lacked the erm and the lnu genes encoding resistance to macrolides and lincosamides, respectively, but carried the vgaALC gene encoding resistance to lincosamides, which is here firstly identified in S. aureus ST398.


After two years the ban of colistin and amoxicillin as feed additives had no significant impact on the MRSA nasal carriage rates. Nevertheless, the MRSA strains circulating in those farms showed resistance to a lower number of antibiotic classes.

Klíčová slova:

Antibiotic resistance – Antibiotics – Antimicrobial resistance – Antimicrobials – Farms – Methicillin-resistant Staphylococcus aureus – Swine – Chloramphenicol


1. Aires de Sousa M. Methicillin-resistant Staphylococcus aureus among animals: current overview. Clin Microbiol Infect. 2016;23(6):373–80. doi: 10.1016/j.cmi.2016.11.002 27851997

2. Conceição T, de Lencastre H, Aires de Sousa M. Frequent isolation of methicillin resistant Staphylococcus aureus (MRSA) ST398 among healthy pigs in Portugal. PLoS One. 2017;12(4):e0175340. doi: 10.1371/journal.pone.0175340 28399155

3. Direção Geral de Alimentação e Veterinária Ministério da Agricultura e do Mar. Plano de ação nacional para a redução do uso de antibióticos nos animais. 2014.

4. Blake DP, Humphry RW, Scott KP, Hillman K, Fenlon DR, Low JC. Influence of tetracycline exposure on tetracycline resistance and the carriage of tetracycline resistance genes within commensal Escherichia coli populations. Journal of applied microbiology. 2003;94(6):1087–97. Epub 2003/05/20. doi: 10.1046/j.1365-2672.2003.01937.x 12752819.

5. Gellin G, Langlois BE, Dawson KA, Aaron DK. Antibiotic resistance of gram-negative enteric bacteria from pigs in three herds with different histories of antibiotic exposure. Appl Environ Microbiol. 1989;55(9):2287–92. Epub 1989/09/01. 2802608; PubMed Central PMCID: PMC203070.

6. Bibbal D, Dupouy V, Ferre JP, Toutain PL, Fayet O, Prere MF, et al. Impact of three ampicillin dosage regimens on selection of ampicillin resistance in Enterobacteriaceae and excretion of blaTEM genes in swine feces. Appl Environ Microbiol. 2007;73(15):4785–90. Epub 2007/06/15. doi: 10.1128/AEM.00252-07 17557857; PubMed Central PMCID: PMC1951005.

7. Langlois BE, Cromwell GL, Stahly TS, Dawson KA, Hays VW. Antibiotic resistance of fecal coliforms after long-term withdrawal of therapeutic and subtherapeutic antibiotic use in a swine herd. Appl Environ Microbiol. 1983;46:1433–4. 6660878

8. Okuma K, Iwakawa K, Turnidge JD, Grubb WB, Bell JM, O'Brien FG, et al. Dissemination of new methicillin-resistant Staphylococcus aureus clones in the community. J Clin Microbiol. 2002;40(11):4289–94. doi: 10.1128/JCM.40.11.4289-4294.2002 12409412

9. Aires-de-Sousa M, Boye K, de Lencastre H, Deplano A, Enright MC, Etienne J, et al. High interlaboratory reproducibility of DNA sequence-based typing of bacteria in a multicenter study. J Clin Microbiol. 2006;44(2):619–21. doi: 10.1128/JCM.44.2.619-621.2006 16455927.

10. Enright MC, Day NP, Davies CE, Peacock SJ, Spratt BG. Multilocus sequence typing for characterization of methicillin- resistant and methicillin-susceptible clones of Staphylococcus aureus. J Clin Microbiol. 2000;38(3):1008–15. 10698988

11. Milheiriço C, Oliveira DC, de Lencastre H. Update to the multiplex PCR strategy for assignment of mec element types in Staphylococcus aureus. Antimicrob Agents Chemother. 2007;51(9):3374–7. doi: 10.1128/AAC.00275-07 17576837.

12. Zankari E, Hasman H, Cosentino S, Vestergaard M, Rasmussen S, Lund O, et al. Identification of acquired antimicrobial resistance genes. J Antimicrob Chemother. 2012;67(11):2640–4. Epub 2012/07/12. doi: 10.1093/jac/dks261 22782487; PubMed Central PMCID: PMC3468078.

13. Jia B, Raphenya AR, Alcock B, Waglechner N, Guo P, Tsang KK, et al. CARD 2017: expansion and model-centric curation of the comprehensive antibiotic resistance database. Nucleic Acids Res. 2017;45(D1):D566–D73. Epub 2016/10/30. doi: 10.1093/nar/gkw1004 27789705; PubMed Central PMCID: PMC5210516.

14. Cavaco LM, Hasman H, Stegger M, Andersen PS, Skov R, Fluit AC, et al. Cloning and occurrence of czrC, a gene conferring cadmium and zinc resistance in methicillin-resistant Staphylococcus aureus CC398 isolates. Antimicrob Agents Chemother. 2010;54(9):3605–8. Epub 2010/06/30. doi: 10.1128/AAC.00058-10 20585119; PubMed Central PMCID: PMC2934997.

15. Kehrenberg C, Schwarz S. Distribution of florfenicol resistance genes fexA and cfr among chloramphenicol-resistant Staphylococcus isolates. Antimicrob Agents Chemother. 2006;50(4):1156–63. Epub 2006/03/30. doi: 10.1128/AAC.50.4.1156-1163.2006 16569824; PubMed Central PMCID: PMC1426988.

16. Argudin MA, Tenhagen BA, Fetsch A, Sachsenroder J, Kasbohrer A, Schroeter A, et al. Virulence and resistance determinants of German Staphylococcus aureus ST398 isolates from nonhuman sources. Appl Environ Microbiol. 2011;77(9):3052–60. Epub 2011/03/08. doi: 10.1128/AEM.02260-10 21378035; PubMed Central PMCID: PMC3126402.

17. Fessler A, Scott C, Kadlec K, Ehricht R, Monecke S, Schwarz S. Characterization of methicillin-resistant Staphylococcus aureus ST398 from cases of bovine mastitis. J Antimicrob Chemother. 2010;65(4):619–25. Epub 2010/02/19. doi: 10.1093/jac/dkq021 20164198.

18. Trong HN, Prunier AL, Leclercq R. Hypermutable and fluoroquinolone-resistant clinical isolates of Staphylococcus aureus. Antimicrob Agents Chemother. 2005;49(5):2098–101. Epub 2005/04/28. doi: 10.1128/AAC.49.5.2098-2101.2005 15855537; PubMed Central PMCID: PMC1087674.

19. Novotna G, Janata J. A new evolutionary variant of the streptogramin A resistance protein, Vga(A)LC, from Staphylococcus haemolyticus with shifted substrate specificity towards lincosamides. Antimicrob Agents Chemother. 2006;50(12):4070–6. Epub 2006/10/04. doi: 10.1128/AAC.00799-06 17015629; PubMed Central PMCID: PMC1693986.

20. Tang Y, Larsen J, Kjeldgaard J, Andersen PS, Skov R, Ingmer H. Methicillin-resistant and -susceptible Staphylococcus aureus from retail meat in Denmark. Int J Food Microbiol. 2017;249:72–6. Epub 2017/03/23. doi: 10.1016/j.ijfoodmicro.2017.03.001 28324679.

21. van Alen S, Ballhausen B, Peters G, Friedrich AW, Mellmann A, Köck R, et al. In the centre of an epidemic: Fifteen years of LA-MRSA CC398 at the University Hospital Munster. Vet Microbiol. 2016;200:19–24. doi: 10.1016/j.vetmic.2016.01.021 26878970

22. Wulf MW, Sorum M, van Nes A, Skov R, Melchers WJ, Klaassen CH, et al. Prevalence of methicillin-resistant Staphylococcus aureus among veterinarians: an international study. Clin Microbiol Infect. 2008;14(1):29–34. Epub 2007/11/08. doi: 10.1111/j.1469-0691.2007.01873.x 17986212.

23. Agency EM. Sales of veterinary antimicrobial agents in 30 European countries in 2016—Trends from 2010 to 2016 Eighth ESVAC report. 2018.

24. Monecke S, Slickers P, Gawlik D, Muller E, Reissig A, Ruppelt-Lorz A, et al. Variability of SCCmec elements in livestock-associated CC398 MRSA. Vet Microbiol. 2018;217:36–46. Epub 2018/04/05. doi: 10.1016/j.vetmic.2018.02.024 29615254.

25. Larsen J, Clasen J, Hansen JE, Paulander W, Petersen A, Larsen AR, et al. Copresence of tet(K) and tet(M) in livestock-associated methicillin-resistant Staphylococcus aureus clonal complex 398 is associated with increased fitness during exposure to sublethal concentrations of tetracycline. Antimicrob Agents Chemother. 2016;60(7):4401–3. Epub 2016/05/11. doi: 10.1128/AAC.00426-16 27161637; PubMed Central PMCID: PMC4914685.

26. Fessler A, Kadlec K, Wang Y, Zhang WJ, Wu C, Shen J, et al. Small antimicrobial resistance plasmids in livestock-associated methicillin-resistant Staphylococcus aureus CC398. Frontiers in microbiology. 2018;9:2063. Epub 2018/10/05. doi: 10.3389/fmicb.2018.02063 30283407; PubMed Central PMCID: PMC6157413.

27. Lozano C, Aspiroz C, Ara M, Gomez-Sanz E, Zarazaga M, Torres C. Methicillin-resistant Staphylococcus aureus (MRSA) ST398 in a farmer with skin lesions and in pigs of his farm: clonal relationship and detection of lnu(A) gene. Clin Microbiol Infect. 2011;17(6):923–7. Epub 2011/06/21. doi: 10.1111/j.1469-0691.2010.03437.x 21682806.

28. Lozano C, Aspiroz C, Saenz Y, Ruiz-Garcia M, Royo-Garcia G, Gomez-Sanz E, et al. Genetic environment and location of the lnu(A) and lnu(B) genes in methicillin-resistant Staphylococcus aureus and other staphylococci of animal and human origin. J Antimicrob Chemother. 2012;67(12):2804–8. Epub 2012/08/18. doi: 10.1093/jac/dks320 22899804.

29. Qin X, Poon B, Kwong J, Niles D, Schmidt BZ, Rajagopal L, et al. Two paediatric cases of skin and soft-tissue infections due to clindamycin-resistant Staphylococcus aureus carrying a plasmid-encoded vga(A) allelic variant for a putative efflux pump. Int J Antimicrob Agents. 2011;38(1):81–3. Epub 2011/05/10. doi: 10.1016/j.ijantimicag.2011.03.007 21549571.

30. Otarigho B, Falade MO. Analysis of antibiotics resistant genes in different strains of Staphylococcus aureus. Bioinformation. 2018;14(3):113–22. Epub 2018/05/23. doi: 10.6026/97320630014113 29785070; PubMed Central PMCID: PMC5953858.

31. Hau SJ, Bayles DO, Alt DP, Frana TS, Nicholson TL. Complete genome sequence of a livestock-associated methicillin-resistant Staphylococcus aureus Sequence Type 5 Isolate from the United States. Genome Announc. 2017;5(32). Epub 2017/08/12. doi: 10.1128/genomeA.00791-17 28798188; PubMed Central PMCID: PMC5552997.

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2019 Číslo 11