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Updated: Dec 22, 2025
Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
Prevalence of methicillin-resistant (mecA gene) and heat-resistant Staphylococcus aureus strains in pasteurized camel
Hany M Yehia1, Abdulrahman H Al-Masoud2, Khaloud M Alarjani3
1Food Science and Nutrition Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; Food Science and Nutrition Department, Faculty of Home Economics, Helwan University, P.O. Box 11611, Cairo, Egypt.
Abstract:
Staphylococcus aureus is a significant opportunistic pathogen in humans, dairy cattle, and camels. The presence of antibiotic-resistant and heat-resistant bacteria in camel milk has become a potential public health issue. The phenotypic and molecular characterization of methicillin-resistant staphylococcal strains recovered from pasteurized camel milk distributed in retail markets of Saudi Arabia was assessed. A total of 100 samples were collected between March and May 2017. Out of the 20 S. aureus isolates that were recovered from the pasteurized camel milk, 10 were found to be resistant to cefoxitin (30 µg) and, thus, were designated as methicillin-resistant strains. The resistance ratio of methicillin-resistant S. aureus isolates for a different class of antibiotics was determined by performing the antimicrobial susceptibility test and was estimated to be approximately 60%. Polymerase chain reaction assay was performed to amplify the methicillin-resistant gene mecA, and furthermore, nucleotide sequencing was performed to detect and verify the presence of methicillin-resistant strains. Upon sequencing the putative S. aureus methicillin-resistant strains, we obtained 96 to 100% similarity to the penicillin-binding protein 2a gene (mecA) of the S. aureus strain CS100. Moreover, the 10 methicillin-resistant S. aureus isolates were also identified to be heat resistant and were stable at temperatures up to 85°C for 60 s, with 3 isolates being heat resistant even at 90°C for 60 or 90 s. The mean decimal reduction time (D85 value) was 111 s for all the 10 isolates. No difference was observed in the profile of total protein between the 10 methicillin- and heat-resistant S. aureus isolates and the S. aureus strain ATCC 29737, which was determined by sodium dodecyl sulfate-PAGE analyses. Therefore, we could conclude that a relatively high percentage of the tested pasteurized camel milk samples were contaminated with S. aureus (20%) and methicillin- and heat-resistant S. aureus (10%).
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) found in pasteurized camel milk in Saudi Arabia is heat-resistant, posing a public health risk. This study identified 10% of samples containing these resistant and heat-stable bacteria.
Area of Science:
- Food Microbiology
- Antimicrobial Resistance
- Public Health
Background:
- Staphylococcus aureus is an opportunistic pathogen found in humans and animals.
- Antibiotic-resistant and heat-resistant bacteria in camel milk present a public health concern.
- Pasteurized camel milk may harbor resistant strains.
Purpose of the Study:
- To characterize methicillin-resistant Staphylococcus aureus (MRSA) strains from pasteurized camel milk.
- To assess the antibiotic resistance and heat resistance of these MRSA strains.
- To determine the prevalence of MRSA in Saudi Arabian retail markets.
Main Methods:
- Phenotypic and molecular characterization of S. aureus isolates.
- Antimicrobial susceptibility testing and polymerase chain reaction (PCR) for the mecA gene.
- Heat resistance testing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for protein profiling.
Main Results:
- Out of 100 samples, 20% yielded S. aureus, with 10% identified as methicillin-resistant (MRSA).
- MRSA isolates showed approximately 60% resistance to various antibiotics and were heat-resistant up to 85°C.
- Sequencing confirmed the presence of the mecA gene in MRSA isolates, showing 96-100% similarity to reference strains.
Conclusions:
- Pasteurized camel milk in Saudi Arabia is contaminated with both S. aureus and heat- and antibiotic-resistant MRSA.
- The identified MRSA strains exhibit significant heat stability, posing a potential food safety risk.
- Further surveillance and control measures are necessary to mitigate the public health threat posed by resistant bacteria in dairy products.
