Related Experiment Video
Updated: May 14, 2026
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR (RS-PCR)
Published on: November 4, 2016
Prevalence and characterization of methicillin-resistant Staphylococcus aureus isolates from retail meat and humans
Charlene R Jackson1, Johnnie A Davis, John B Barrett
1Bacterial Epidemiology and Antimicrobial Resistance Research Unit, USDA-ARS, Russell Research Center, Athens, Georgia, USA. charlene.jackson@ars.usda.gov
Abstract:
There is increasing interest in the presence of Staphylococcus aureus, specifically methicillin-resistant S. aureus (MRSA), on retail meat products. In this study, staphylococci were isolated from retail pork and retail beef in Georgia, and MRSA from the products was compared to human MRSA from the same geographic area using broth microdilution antimicrobial susceptibility testing, multilocus sequence typing (MLST), spa typing, SCCmec typing, and pulsed-field gel electrophoresis (PFGE). S. aureus was isolated from 45% (45/100) of pork products and 63% (63/100) of beef products; mecA was detected in S. aureus from both pork (3/100; 3%) and beef (4/100; 4%). Fifty percent (50/100) of human S. aureus also contained mecA. Multidrug resistance was detected among MRSA from all sources. All MRSA (n = 57) was SCCmec type IV, and nine different spa types were present among the isolates (t002, t008, t012, t024, t179, t337, t548, t681, and t1062). Four sequence types (ST5, ST8, ST9, and ST30) were detected using MLST; the majority of MRSA isolates belonged to ST8, followed by ST5. One retail beef MRSA isolate belonged to ST8, while the remaining three were ST5. In retail pork MRSA, ST5, ST9, and ST30 were observed. The majority of human MRSA isolates belonged to ST8. Thirty-seven MRSA isolates, one of which was a retail beef MRSA isolate, were pvl(+). Using PFGE, MLST, and spa typing, three retail beef MRSA isolates were found to be identical in PFGE pattern, ST, and spa type to two human clonal MRSA isolates (USA100 and USA300). One additional retail beef MRSA isolate had a PFGE pattern similar to that of a human MRSA isolate, whereas none of the retail pork MRSA isolates had PFGE patterns similar to those of human MRSA isolates. These data suggest that the retail beef samples were contaminated by a human source, possibly during processing of the meat, and may present a source of MRSA for consumers and others who handle raw meat.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) was found in retail beef and pork. Genetic analysis revealed retail beef MRSA likely originated from human contamination during processing, posing a risk to consumers.
Area of Science:
- Microbiology
- Food Safety
- Public Health
Background:
- Increasing concern regarding Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), in retail meat products.
- MRSA poses a significant public health threat due to its antibiotic resistance.
Purpose of the Study:
- To investigate the presence and characteristics of MRSA in retail pork and beef in Georgia.
- To compare MRSA isolates from meat products with human MRSA isolates from the same region.
- To determine potential sources of MRSA contamination in the food supply chain.
Main Methods:
- Isolation of staphylococci from retail pork and beef samples.
- Antimicrobial susceptibility testing using broth microdilution.
- Molecular typing including multilocus sequence typing (MLST), spa typing, SCCmec typing, and pulsed-field gel electrophoresis (PFGE).
Main Results:
- Staphylococcus aureus detected in 45% of pork and 63% of beef samples; MRSA found in 3% of pork and 4% of beef.
- Human MRSA isolates showed similar multidrug resistance patterns and SCCmec type IV as meat isolates.
- Genetic analysis indicated that some retail beef MRSA isolates were indistinguishable from human MRSA strains (USA100 and USA300), suggesting human contamination during processing.
Conclusions:
- Retail beef, and to a lesser extent pork, can harbor MRSA.
- Evidence suggests human handling and processing are likely sources of MRSA contamination in retail beef.
- Contaminated meat products may represent a potential source of MRSA transmission to consumers and food handlers.
Related Concept Videos
01:25Clinical Significance of Antibiotic Resistance
01:25Mechanism of Antibiotic Resistance in MRSA
01:29Staphylococcal Skin Infections