Background and Aim: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most recognized "superbugs" and a common cause of community-associated and nosocomial infections; furthermore, when chicken meat is considered a good growth medium for S. aureus to make a plausible vehicle to propagate MRSA, then this study was conducted to evaluate the efficiency of ozonated water (0.5 ppm) in the elimination or reduction of MRSA contaminating fresh and frozen chicken meat sold in local markets in the Wasit Province.

Materials and Methods: A total of 72 samples of fresh and frozen chicken meat were randomly collected from dissimilar native markets: Fresh chicken meat (n=32) and frozen chicken meat (n=40). Isolation and identification of MRSA isolates were conducted using standard bacteriological, biochemical, RapID™ Staph Plus System (Remel, R8311009), and latex agglutination tests such as Dry SPOT Staphytect Plus (Oxoid, DR0100M) and PBP2' Test Kit (Oxoid, DR0900A). The generation of ozone (O₃) was carried out using O₃ generator (A2Z/AQUA-6, USA), and its concentration (ppm) in water was determined using CHE-Mets^®-Kit, USA.

Results: A total of 39 (54.2%) of 72 fresh and frozen chicken meat were positive for S. aureus; of those 39 positive samples, 13 (33.3%) were identified as MRSA. The antibiotic sensitivity test results revealed that all MRSA isolates had multiple resistance to at least four antimicrobial agents for which these isolates had 12 antibiotic resistance patterns. Results of O₃ treatment in MRSA isolate contaminating 13 of both fresh and frozen chicken meat samples showed that, after treatment with ozonated water (0.5 ppm/4°C), the overall negative samples were 23.1% and 69.2% for 30 and 45 min, respectively. The decrease in the percentage of positive samples was very significant from a public health perspective. Furthermore, the antimicrobial efficacy of ozonated water (0.5 ppm) on the reduction of the MRSA count (log₁₀ colony-forming units [CFU]/ml) was assessed in four positive samples of fresh and frozen chicken meat, and the results revealed that, after treatments, the overall reduction was 2-4 log₁₀ (CFU/ml) after 45 min. This reduction is highly significant from a public health perspective.

Conclusion: From the data obtained from this study, it can be concluded that fresh and frozen chicken meat sold in the different markets of Wasit Province was highly contaminated by S. aureus during the study period with a total prevalence of 54.2%; among those, 33.3% were recognized as MRSA. Under the conditions described in the present study, O₃ at the concentration of 0.5 ppm is highly effective in reducing the number of MRSA-positive samples and the number decreased with increased exposure time to ozonated water at the same concentration. These findings indicated that O₃ treatment might constitute the basis for an alternative method to reduce meat contamination with foodborne pathogens such as MRSA.

Keywords: antibacterial effect, chicken meat, methicillin-resistant Staphylococcus aureus, ozonated water, Wasit Province.

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