Ten years later: still a high prevalence of MRSA in slaughter pigs despite a significant reduction in antimicrobial usage in pigs the Netherlands.
In 2005, 39% of pigs and 81% of the slaughter batches at Dutch slaughterhouses were MRSA positive. The objective of the present study was to investigate whether the 50% reduction of antimicrobial usage in finishing pigs in 2014 compared with 2009 in the Netherlands has led to a lower MRSA prevalence among Dutch slaughter pigs.



Nasal swabs from eight slaughter batches of on average 10 animals at seven slaughterhouses were taken and cultured using method 1, which was used in 2005, and method 2, using high-salt pre-enrichment. Suspected isolates were confirmed by PCR for two Staphylococcus aureus-specific DNA fragments and the mecA gene. A subset of MRSA isolates were further investigated using spa typing, multiple-locus variable number of tandem repeat analysis (MLVA) and antimicrobial susceptibility testing.



Using methods 1 and 2, we found 461 of 558 (83%) and 552 of 558 (99%) of the pigs to carry MRSA in their nares, respectively. All 56 slaughter batches were MRSA positive. All MRSA isolates belonged to the livestock-associated MLVA complex 398, had a non-WT phenotype for tetracycline and spa type t011 predominated.



A very high prevalence of nasal MRSA carriage was found in Dutch slaughter pigs and therefore the reduction in antimicrobial usage at the national level has not yet had an effect on the MRSA carriage rate of pigs entering the slaughterhouse. Therefore, there is still an increased risk of MRSA carriage for personnel working at pig slaughterhouses, particularly those having contact with living animals. Method 2, using high salt pre-enrichment, detected more MRSA-positive pigs and is currently the preferred method for screening of MRSA in livestock in the Netherlands.
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
Cindy M
CM
Dierikx
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
Paul D
PD
Hengeveld
Central Veterinary Institute (CVI) of Wageningen UR, Lelystad, The Netherlands.
Kees T
KT
Veldman
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
Angela
A
de Haan
Netherlands Food and Consumer Product Safety Authority, Utrecht, The Netherlands.
Sanne
S
van der Voorde
Netherlands Food and Consumer Product Safety Authority, Utrecht, The Netherlands.
Petra Y
PY
Dop
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
Thijs
T
Bosch
National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands engeline.van.duijkeren@rivm.nl.
Engeline
E
van Duijkeren
D000003:Abattoirs; D000822:Animal Husbandry / Q000379:methods* / Q000592:standards; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001431:Bacteriological Techniques; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D016000:Cluster Analysis; D004363:Drug Utilization / Q000592:standards*; D005838:Genotype; D006291:Health Policy; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D025202:Molecular Diagnostic Techniques; D058889:Molecular Typing; D009296:Nasal Cavity / Q000382:microbiology; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D013552:Swine / Q000382:microbiology*
D000900:Anti-Bacterial Agents