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 (D 85 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%).

Camel meat is one of the most consumed meats in Arab countries. The use of natural antimicrobial agents to extend the shelf life of fresh camel meat, control Campylobacter jejuni contamination, and preserve meat quality is preferred. In this study, we determined the antimicrobial effects of using 1% or 2% Citrox alone or in combination with 1% chitosan on the survival of C. jejuni in vitro and on camel meat samples during storage at 4 or 10 °C for 30 days in vacuum packaging. We determined the total viable count (TVC (cfu/g)), total volatile base nitrogen (TVB-N) content, and pH of the treated camel meat samples every three days during storage. The shelf lives of camel meat samples treated with 2% Citrox alone or in combination with 1% chitosan were longer than those of camel meat samples treated with 1% Citrox alone or in combination with 1% chitosan at both the 4 and 10 °C storage temperatures, with TVCs of <100 cfu/g after the first ten days and six days of storage at 4 and 10 °C, respectively. The addition of Citrox (1% and 2%) and 1% chitosan to camel meat samples and the application of vacuum storage were more effective than using Citrox (1% and 2%) alone and led to a reduction in C. jejuni in approximately 4.0 and 3.5 log cycles at 4 and 10 °C, respectively. The experimental results demonstrated that using a Citrox-chitosan combination improved the quality of camel meat and enhanced the long-term preservation of fresh meat for up to or more than 30 days at 4 °C.

Milk pasteurization eliminates vegetative pathogenic microorganisms and reduces microorganisms associated with spoilage. Camel milk is a well-accepted, traditionally consumed food in Arab countries. The present study aimed to investigate the microflora of pasteurized camel milk sold in Riyadh City, Saudi Arabia. The heat resistance of the microflora was tested in culture medium and lab-sterilized milk, and its composition was verified by multiplex polymerase chain reaction (PCR) using specific primers. Further verification was performed by using separate specific primers. The identified strain survived heat treatment at 65, 72, 80, 85, and 90°C for 30, 15, 10, 5, and 2 min, respectively. An unanticipated result was obtained when an enterotoxin producing strain of Staphylococcus aureus showed abnormal resistance to heat treatment. The enterotoxin gene within the PCR fragment was identified as enterotoxin C by DNA sequencing. During Basic Local Alignment Search Tool (BLAST) analysis, the isolated enterotoxin C genes showed >99% similarity to published database sequences of the Staphylococcus aureus strain SAI48 staphylococcal enterotoxin C variant v4 (sec) gene. The decimal reduction value (D-value) at 90°C (D90) was determined after 10 s. This is the first time to report this abnormally heat resistant and enterotoxin-producing strain of Staphylococcus aureus. The use of ultra-high temperatures (UHTs) is preferable for reducing or killing bacteria in camel milk, especially if this problem is encountered in many camel milk factories.

Antibiotic- and heat-resistant bacteria in camel milk is a potential public health problem. Staphylococcus aureus (S. aureus) is an opportunistic pathogen in humans, dairy cattle and camels. We characterized the phenotype and genotype of methicillin-resistant staphylococcal strains recovered from pasteurized and raw camel milk (as control) distributed in the retail markets of Saudi Arabia. Of the 100 samples assessed between March and May 2016, 20 S. aureus isolates were recovered from pasteurized milk, 10 of which were resistant to cefoxitin, and as such, were methicillin-resistant. However, raw camel milk did not contain methicillin-resistant S. aureus (MRSA). Antimicrobial susceptibility tests showed that the resistance ratio for other antibiotics was 60%. We performed a polymerase chain reaction (PCR) assay using primers for the methicillin-resistant gene mecA and nucleotide sequencing to detect and verify the methicillin-resistant strains. Basic local alignment search tool (BLAST) analysis of the gene sequences showed a 96–100% similarity between the resistant isolates and the S. aureus CS100 strain’s mecA gene. Ten of the methicillin-resistant isolates were heat-resistant and were stable at temperatures up to 85°C for 60 s, and three of these were resistant at 90°C for 60 or 90 s. The mean decimal reduction time (D85-value) was 111 s for the ten isolates. Sodium dodecyl sulfate (SDS)/polyacrylamide gel electrophoresis (PAGE) showed that there was no difference in the total protein profiles for the ten methicillin heat-resistant S. aureus (MHRSA) isolates and for S. aureus ATCC 29737. In conclusion, a relatively high percentage of the tested pasteurized camel milk samples contained S. aureus (20%) and MHRSA (10%).

C. jejuni and S. typhimurium are the leading causes of bacterial food contamination in chicken carcasses. Contamination is particularly associated with the slaughtering process. This study isolated C. jejuni and S. typhimurim from fifty chicken carcass samples, all of which were acquired from different companies in Riyadh, Saudi Arabia. The identification of C. jejuni was performed phenotypically by using a hippurate test and genetically using a polymerase chain reaction with primers for 16S rRNA and hippurate hydrolase (hipO gene). For the dentification of S. typhimurim, a serological Widal test was carried out using serum antiS. typhimurium antibodies. Samonella genetically detected using invA gene primers. The positive isolates for C. jejuni showed a specific molecular size of 1448 bp for 16S rRNA and 1148 bp for hipO genes. However, the positive isolates of the invA gene exhibited a specific molecular size at 244 bp using polymerase chain reaction. Comparing sequencing was performed with respect to the invA gene and the BLAST nucleotide isolates that were identified as Salmonella enterica subsp. enterica serovar typhimurium strain ST45, thereby producing a similarity of 100%. The testing identified C. jejuni for hippuricase, GenBank: Z36940.1. Many isolates of Salmonella spp. that contained the invA gene were not necessarily identified as S. typhimurim, the limiting factor for the Widal test used antiS. typhimurum antibodies. The multidrug resistance of C. jejuni isolates in chickens was compared with the standard C. jejuni strain ATCC 22931. Similarly, S. typhimurium isolates were compared with the standard S. typhimurium strain ATCC 14028.

Nisin and reuterin are used in processed foods as preservatives. They are considered to be potential sources of natural antibiotics for the treatment of food contaminated by antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus. We try to compare the best effect of both nisin and reuterin on the growth of methicillin-resistant S. aureus (MRSA) and S. aureus ATCC 25923. The results indicated that nisin at different concentrations inhibited the growth of methicillin-resistant S. aureus after 4 h, whereas after 12 and 24 h, the bacteria have regrown and reactivated. S. aureus ATCC 25923 was not affected by nisin concentration and has continuously grew at all times. Reuterin at different concentrations gradually inhibited the growth of methicillin-resistant S. aureus and S. aureus ATCC 25923 and declined after 12 h for both. Therefore, it can be deduced that nisin alone exerts a bacteriostatic effect on methicillin-resistant S. aureus but not on S. aureus ATCC 25923. Reuterin is considered as bactericidal effect on both microorganisms. The combination of nisin at a concentration of 25.6 and reuterin at a concentration of 5.2 mg/mL exerted a bactericidal effect on both microorganisms. By mixing nisin with reuterin, it can be more active against both microorganisms.

Natural antibacterial agents such as citrox are effective against many foodborne pathogens and foods contaminated with bacteria. We studied the antimicrobial effects of citrox solutions (1% and 2%) on the total viable counts of methicillin-resistant Staphylococcus aureus (MRSA) in chicken meat fillets. The total coliform group counts found in the chicken samples were also determined. The samples were treated with S. aureus at a concentration of 106 colony-forming units (cfu)/g of meat and vacuum-packed (VP) at 4 °C for 3, 6, 9, 12, 15, 18, and 21 days. We also studied the effect of citrox on the total volatile basic nitrogen (TVBN) content and pH changes during the storage period of the meat samples. The results revealed that citrox inhibited the growth of MRSA in the chicken fillets. The total viable counts of MRSA decreased after treatment with 2% citrox in all treated samples that were stored at 4 °C by approximately 2 log units compared with the samples inoculated with S. aureus (Chicken-Staph groups) after 3, 6, 9, and 12 days of storage, and by approximately 1 log unit compared with the control samples treated with salt (Chicken-Salt groups) after 3, 6, and 9 days of storage. TVBN was reduced in the Chicken-Citrox-treated samples stored at 4 °C compared with the Chicken-Staph- and Chicken-Salt-treated samples. The results indicated that citrox is effective in reducing the total counts of MRSA and in improving the quality of chicken during the first three days of storage by reducing the number of bacteria by 1 log unit and extending the shelf life of chicken.

Citrox has natural antibacterial effect against many foodborne pathogens and contaminated bacteria. Ot mainly contains citric acid, ascorbic acid, and malic acid. We studied the antimicrobial effects of citrox solution (1% and 2%) on the total viable count of methicillin-resistant Staphylococcus aureus (MRSA) on chicken meat fillet. The samples were treated with 10 6 CFU/g of meat, vacuum-packed (VP), and 4 °C for 3, 6, 9, 12, 15, 18, 21 days. We have also studied the effect of citrox on the total volatile basic nitrogen (TVBN) content and pH changes during the storage periods. The results revealed that citrox inhibited the growth of methicillin-resistant S. aureus (MRSA), in the chicken fillet. The total viable count of MRSA gradually decreased in all treated samples that were stored at 4 °C about 2 log cycle than Chicken-Staph groups after 3, 6, 9, and 12 days and about 1 log cycle than Chicken-Salt group after 3, 6, and 9 days of storage. Total volatile base nitrogen (TVB-N) were observed to be reduced in Chicken-Citrox-treated samples stored at 4 °C than Chicken-Staph, and Chicken-Salt treated samples. The results indicated that citrox is effective to reduce the total count of S. aureus (MRSA) in the first three days of storage by a reduction in the number of bacteria 1 log cycle.