Characterization of Methicillin-Resistant Staphylococcus aureus Isolates from Pig Carcasses in Hong Kong

J. Ho, Margaret May O'Donoghue, L. Guardabassi, A. Moodley, M. Boost

Research output: Journal article publicationJournal articleAcademic researchpeer-review

25 Citations (Scopus)


This study describes the isolation and characterization of methicillin-resistant Staphylococcus aureus (MRSA) from slaughtered pigs sampled from local markets in Hong Kong. The nares of 400 slaughtered pigs were cultured and MRSA isolates characterized for the presence of antibiotic-resistance determinants, toxins and SCCmec and spa types using PCR. Clonality was investigated using PFGE and MLST. The prevalence of MRSA colonization of slaughter pigs was 39.3%, the majority (92%) harbouring SCCmec type IVb. Of the 157 samples yielding MRSA, 13 had two distinct MRSA strains present. Spa type t899 was predominant, with only 5/170 isolates displaying closely related types (t4474, t1939, t2922 and t5390). PFGE with sma1 and MLST confirmed the strains as ST9. Most isolates were multidrug resistant. Tetracycline resistance (97%) was mainly attributable to tet(K) with only 3% of isolates additionally harbouring tet(M). Resistance to erythromycin (89%) and chloramphenicol (71%) was associated with the presence of erm(C), and fex(A), respectively. No strains carried cfr and there was no resistance to linezolid, although minimum inhibitory concentration (MICs) were close to the resistance break point. Resistance to clindamycin (99%), ciprofloxacin(78%), quinopristin-dalfopristin (44%) and cotrimoxazole (32%) was common, but remained low for fusidic acid (4%) and rifampicin (2%). All strains were negative for PVL, exfoliative, and enterotoxins. This survey confirmed the uniformity of MRSA isolates in pigs from several regions of China, in contrast to more diversified characteristics reported in European studies. Colonization rates were higher than previously reported. Isolates were resistant to a wide range of antibiotics, but resistance was not detected to linezolid, nitrofurantoin, vancomycin or tigecycline. Although the clinical importance of ST9 in humans is uncertain, continued surveillance, in particular of those occupationally-exposed, is recommended.
Original languageEnglish
Pages (from-to)416-423
Number of pages8
JournalZoonoses and Public Health
Issue number6
Publication statusPublished - 1 Sept 2012


  • Genotyping
  • Hong Kong
  • Methicillin-resistant Staphylococcus aureus
  • Phenotyping
  • Pig carcasses

ASJC Scopus subject areas

  • Epidemiology
  • General Immunology and Microbiology
  • General Veterinary
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases


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