Characteristics of enterotoxin-producing methicillin-resistant Staphylococcus aureus strains isolated from meat in Tehran, Iran

Methicillin- and Vancomycin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci Isolated from Hospital Foods: Prevalence and Antimicrobial Resistance Patterns

This study aimed to investigate the prevalence of Methicillin- and Vancomycin-Resistant Staphylococcus aureus (MRSA, VRSA) and Vancomycin-Resistant Enterococcus (VRE) of hospital food samples in Mashhad, Iran. A total of 357 hospital food samples were collected from 13 hospitals. Enterococcus spp. and Staphylococcus aureus were identified using conventional cultural techniques following genotypic confirmation by PCR. The antibiotic resistance patterns of MRSA, VRSA, and VRE strains were analyzed using the disk diffusion methods. The prevalence of S. aureus and MRSA were 24.37% (87/357) and 22.98% (20.87), respectively. In addition, the vanB gene involved in vancomycin resistance was detected in 1.14% of the S. aureus strains. Enterococci and VRE had a prevalence of 15.4% (55/357) and 21.81% (12/55), respectively. Meat, chicken barbecues, and salad were the most commonly contaminated samples with S. aureus, MRSA, Enterococci, and VRE. PCR detected two vancomycin resistance genes, including vanA (1.81%, 1.55) and vanC2 (20%, 11.55) genes. MRSA strains revealed the highest resistance against penicillin, erythromycin, clindamycin, azithromycin, tetracycline, and gentamicin. The VRSA isolates were resistant to penicillin, ampicillin, oxacillin, cefoxitin, clindamycin, erythromycin, gentamicin, and trimethoprim-sulfamethoxazole. Furthermore, VRE isolates exhibited the highest resistance against quinupristin-dalfopristin, erythromycin, and tetracycline. The results of this study indicated that hospital foods might act as a reservoir of Enterococci spp. and S. aureus strains, which can transfer antibiotic resistance. Moreover, multidrug resistance (MDR) in some MRSA, VRSA, and VRE isolates represents a serious threat to susceptible persons in hospitals.

Hazard of Staphylococcal Enterotoxins in Food and Promising Strategies for Natural Products against Virulence

Staphylococcal enterotoxins (SEs) secreted by Staphylococcus aureus frequently contaminate food and cause serious foodborne diseases but are ignored during food processing and even cold-chain storage. Notably, SEs are stable and resistant to harsh sterilization environments, which can induce more serious hazards to public health than the bacterium itself. Therefore, it is necessary to develop promising strategies to control SE contamination in food and improve food safety. Natural products not only have various pharmaceutical properties, such as antimicrobial and antitoxin activities, but they are also eco-friendly, safe, nutritive, and barely drug-resistant. Here, the hazards of SEs and the promising natural compounds with different inhibitory mechanisms are summarized and classified. The key points of future research and applications for natural products against bacterial toxin contamination in food are also prospected. Overall, this review may provide enlightening insights for screening effective natural compounds to prevent foodborne diseases caused by bacterial toxins.

Antimicrobial-resistant foodborne pathogens in the Middle East: a systematic review

Foodborne pathogens are known as significant public health hazards worldwide, particularly in the Middle East region. Antimicrobial resistance (AMR) among foodborne pathogens becomes one of the top challenges for the environment, public health, and food safety sectors. However, less is known about antimicrobial-resistant foodborne pathogens in the Middle East region. Possibly because of the lack of surveillance, documentation, and reporting. This review focuses on the current status of antimicrobial resistance profiling among foodborne pathogens in the Middle East. Therefore, PubMed and other relevant databases were searched following PRISMA guidelines. Subject heading and texts were searched for "antimicrobial resistances," "foodborne," and "Middle East" to identify observational studies on AMR foodborne pathogens published during the last 10 years (2011 to 2020). Article retrieval and screening were done using a structured search string and strict inclusion/exclusion criteria. Median and interquartile ranges of percent resistance were calculated for each antibiotic-bacterium combination. A total of 249 articles were included in the final analysis from ten countries, where only five countries had more than 85% of the included articles. The most commonly reported pathogens were Escherichia coli, Salmonella spp. Staphylococcus aureus, and Listeria spp. An apparent rise in drug resistance among foodborne pathogens was recorded particularly against amoxicillin-clavulanic acid, ampicillin, nalidixic acid, streptomycin, and tetracycline that are commonly prescribed in most countries in the Middle East. Besides, there is a lack of standardization and quality control for microbiological identification and susceptibility testing methods in many of the Middle East countries.

Characterization of methicillin-resistant Staphylococcus aureus strains in sewage treatment plants in Tehran, Iran

Multidrug-resistant Staphylococcus aureus strains have been commonly found in hospitals and communities causing wide ranges of infections among humans and animals. Typing of these strains is a key factor to reveal their clonal dissemination in different regions. We investigated the prevalence and dissemination of different clonal groups of S. aureus with resistance phenotype to multiple antibiotics in two sewage treatment plants (STPs) in Tehran, Iran over four sampling occasions. A total of 576 S. aureus were isolated from the inlet, sludge and outlet. Of these, 80 were identified as methicillin-resistant S. aureus (MRSA) and were further characterized using a combination of Phene Plate (PhP) typing, staphylococcal cassette chromosome mec (SCCmec), ccr types, prophage and antibiotic-resistant profiling. In all, eight common type (CT) and 13 single PhP type were identified in both STPs, with one major CT accounting for 38.8% of the MRSA strains. These strains belonged to three prophage patterns and five prophage types with SCCmec type III being the predominant type. Resistance to 11 out of the 17 antibiotics tested was significantly (P < 0.0059) higher among the MRSA isolates than methicillin-sensitive S. aureus (MSSA) strains. The persistence of the strains in samples collected from the outlet of both STPs was 31.9% for MRSA and 23.1% for MSSA. These data indicated that while the sewage treatment process, in general, is still useful for removing most MRSA populations, some strains with SCCmec type III may have a better ability to survive the STP process.