Detection, molecular characterization, and clonal diversity of methicillin-resistant Staphylococcus aureus CC398 and CC97 in Spanish slaughter pigs of different age groups
Related Experiment Video
Updated: Jun 10, 2026
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR (RS-PCR)
Published on: November 4, 2016
Elena Gómez-Sanz1, Carmen Torres, Carmen Lozano
1Departamento de Agricultura y Alimentación, Universidad de La Rioja, Madre de Dios 51, Logroño, Spain.
Abstract:
The objective of this study was to determine the frequency of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) in slaughter pigs, to characterize the recovered isolates, and to investigate their genomic relatedness. Nasal swabs were collected from 53 finishing-pigs (F-pigs) and 53 suckling-piglets (S-piglets) at two different abattoirs in La Rioja (Northern Spain) coming from six production holdings. MRSA isolates were characterized by spa−, agr−, SCCmec−, and multilocus sequence typing, pulsed-field gel electrophoresis (PFGE)-ApaI, toxin gene profiling, antimicrobial susceptibility, and determination of antimicrobial resistance genes. MRSA isolates were recovered from 11 F-pigs (14 isolates) and 26 S-piglets (30 isolates). Forty of the 44MRSA presented the spa-types t011, t108, t1197, and t2346, which corresponded to the sequence type ST398 and to the clonal complex CC398. Interestingly, the remaining four isolates from F-pigs presented the spa-type t3992, and they were ascribed to a new sequence type named ST1379 (a single-locus variant of ST97), which was included in clonal complex CC97. Five PFGE-ApaI clusters with up to nine individual patterns detected among our MRSA and low genomic relatedness was observed between F-pig and S-piglet isolates. All MRSA were positive for hla, hld, and hlg hemolysin genes. ST1379 isolates harbored eta, lukE/D, and hlg-2 toxin genes, whereas ST398 isolates were positive for hlb. A great variety of distinct resistance gene patterns were observed, most of them coming from F-pig isolates. MRSA virulence properties seem to be dependent of the isolate clonal lineage. This study showed that slaughter pigs are frequently colonized by MRSA CC398; moreover, the detection of strains belonging to CC97 underlines that other lineages are also able to spread in livestock. Further studies should assess the risk of CC398 and non-CC398 MRSA to enter the food chain as well as the human health implications.
Insights
Slaughter pigs frequently carry methicillin-resistant Staphylococcus aureus (MRSA), particularly CC398 strains. Other MRSA lineages, like CC97, also circulate in livestock, posing potential food chain and human health risks.
Area of Science:
- Veterinary Microbiology
- Food Safety
- Genomics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant public health concern.
- Livestock, particularly pigs, can act as reservoirs for MRSA transmission.
- Understanding MRSA prevalence and diversity in pigs is crucial for risk assessment.
Purpose of the Study:
- To determine the frequency of MRSA nasal carriage in slaughter pigs.
- To characterize MRSA isolates by spa-typing, multilocus sequence typing, and other genomic methods.
- To investigate the genomic relatedness of MRSA isolates from pigs.
Main Methods:
- Nasal swabs collected from finishing pigs and suckling piglets at abattoirs.
- MRSA characterization using spa-typing, agr-typing, SCCmec-typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE).
- Toxin gene profiling, antimicrobial susceptibility testing, and antimicrobial resistance gene determination.
Main Results:
- MRSA was recovered from 11/53 finishing pigs and 26/53 suckling piglets.
- Dominant MRSA strains belonged to ST398/CC398 (spa-types t011, t108, t1197, t2346).
- A novel ST1379/CC97 lineage was identified in finishing pigs; low genomic relatedness observed between piglet and finishing pig isolates.
Conclusions:
- Slaughter pigs are frequently colonized by MRSA, predominantly CC398.
- The presence of CC97 MRSA strains indicates the spread of other lineages in livestock.
- Further research is needed to assess food chain entry risks and human health implications of MRSA in pigs.
Related Concept Videos
01:25Clinical Significance of Antibiotic Resistance
01:25Mechanism of Antibiotic Resistance in MRSA
01:29Modern Molecular Taxonomy