Therefore, animal farm workers are at an elevated risk of acquiring and being carriers of ARB and ARG. Being exposed to ARB might pose risks to farm workers when injured, and bacteria might enter the wound, which can lead to complications or severe illnesses among workers. Moreover, farmworkers might then further disseminate ARB to the public; therefore, identifying more AMR reservoirs and occupational exposure routes to AMR is crucial in mitigating AMR among farm workers. At present, while there are studies that have addressed occupational exposure to ARB in farm workers in swine, poultry, and cattle farms , the actual burden of AMR among farm workers who work in different areas of animal agriculture is largely unknown. The studies referenced in the previous sentence reported that farm environment and/or dust or aerosols might be reservoirs of ARB that might be transmitted to farm workers. But still, there is a lack of knowledge about potential reservoirs of AMR in farm environments such as farm facility doors or cages. Moreover, the personal protective equipment of workers at animal farms is a potential reservoir of ARB that has been largely neglected. To date, vertical farming supplies there are only a few studies that characterized antimicrobial resistance patterns from farm workers’ PPE, such as outwear and boots . Also, there is a lack of literature that examines patterns and dynamics of AMR in animal farm environments.
Identifying the specific factors that facilitate AMR transmission among animal farm workers is a necessary step toward mitigating exposure. Additionally, finding new reservoirs of AMR in farm settings and characterizing AMR patterns is very important. The systematic literature review conducted by Tang et al. revealed that ARB can be transmitted from food animals to farm workers, but still, there is weaker evidence of transmission of ARB from food animals and farm workers. However, farm workers in different types of animal farming, depending on the type of animals, might have different risks of exposure to ARB or ARG. Therefore, more research on occupational exposure of farm workers to AMR is crucial.Meat and meat products are vital energy and protein sources widely consumed worldwide . Moreover, with the increasing world population and affluence in developing countries, meat consumption is increasing rapidly . Chicken consumption is growing at a very fast speed due to its low production cost, low fat, and lack of cultural and religious barriers . Food animals are considered one of the primary sources of ARB . ARB in food animals can be transmitted to meat during slaughter from the surrounding environment containing ARB, animal skin, cross-contamination equipment or workers, inadequate evisceration, and poor sanitation .
Contaminated meat with ARB serves as a vehicle for the transmission of AMR along the food chain . Consequently, meat consumption is one of the vital transmission pathways of ARB to enter humans . The prevalence of ARB in retail meat varies depending on the meat type, bacteria present, country of origin, type of antimicrobial used in food animal production, type of production , season, geographic location, meat types and production practices, regulations, surveillance programs, meat sampling methods and bacteria isolation protocols . Additionally, antimicrobial resistance prevalence is strongly correlated with the development statutes of countries as most of the developing countries have not banned the usage of antimicrobial agents as growth promoters. Every meat type is harbored by different types of bacteria, and different types of bacteria develop resistance to antimicrobials differently . For example, Salmonella is common in chicken and pork compared to other types of meat , and beef is a reservoir for Shiga toxin-producing Escherichia coli . Among the different kinds of bacteria family, members of the Enterobacteriaceae family, including Salmonella and E. coli, are commonly associated with foodborne outbreaks worldwide and develop resistance to medically important drugs, especially MDR strains, which challenge the treatments of infectious diseases. For example, in China, between 1994 and 2005, 16.73 % of all foodborne disease outbreaks were caused by Salmonella and accounted for 22.16 of illnesses .
Escherichia coli is a gram-negative bacteria member of the Enterobacteriaceae family, commonly inhabiting human and animal guts . Most of the strains of E. coli are commensal and they are unharmful to their host. However, commensal E. coli can become opportunistic pathogens by acquiring virulence factors and genetic elements and can trigger infections in the urinary tract or the sites of surgical wounds . E. coli has been most prevalent in ground beef compared to other meat types. It is likely that E. coli present in intestinal tracts of cattle can be transferred during the slaughter or other meat handling processes. Moreover, the grinding process further contributes to the highest prevalence of E. coli in beef. Eshireshia coli is considered the most common Gram-negative bacteria, which can potentially cause a wide range of clinical infections among the resistant bacteria .Over the last two decades, multidrug resistance in E. coli has been an alarming worldwide issue in human and veterinary medicine . Especially, MDR of E. coli to therapeutically important drugs such as cephalosporins, fluoroquinolones, carbapenem, and colistin has been a serious problem since MDR in E. coli limits the effectiveness of these clinically essential, frontline antimicrobials. Also, Extended-spectrum β-lactamases , enzymes produced by some strains of E. coli, are a serious threat and lead to higher rates of treatment failures . In order to survive the constant toxic pressure of different antimicrobials provided to host the animals, E. coli uses MDR as a tool . E. coli mainly uses efflux pumps and mobile-resistant mechanisms to cope with arrays of different antimicrobials. Previous studies reported that the most common MDR pattern in E. coli has been resistance to aminoglycosides, β-lactams, sulfonamides, and tetracyclines. . Major resistant genes found in E. coli from animals were ampicillin , tetracycline [tet and tet], streptomycin/spectinomycin , sulfamethoxazole , and trimethoprim . It is known that horizontal gene transfer is the main factor in gaining MDR in bacteria . E coli has a robust ability to acquire resistance easily due to genetic flexibility and adaptability to the environment . Mobile genetic elements are thought to carry the majority of resistance genes . The insident of antimicrobial resistance in E. coli from humans and food animals has been increasing steadily since half of the last century . Resistant rates in E. coli might differ depending on factors such as usage of antibiotics, virulencefactors, food sources, and molecular epidemiology . Since E. coli is ubiquitous in food animals and considered a potential reservoir of resistant determinants, E. coli has been used for surveillance and monitoring as an indicator of AMR in many countries, including the U.S. . For example, in the U.S., the CDC established multiple surveillance programs Surveillance to track the resistance patterns and trends of infections of E. coli .Antimicrobial resistance patterns and prevalence of resistance of Salmonella in retail meat differ by country and geographical location. This difference might be due to different factors such as regulations, cannabis indoor greenhouse antimicrobial usage policies, livestock production practices, veterinary practices, consumer preferences and demands, antibiotic stewardship, and funding mechanisms to develop new classes of antibiotics . For example, a study examining antimicrobial resistance in Salmonella in retail meat in the U.S. between 2002-2017 found that Salmonella isolates from Northwestern parts of the country were more resistant to antimicrobials .
Even in one country, antimicrobial resistance patterns change over time due to regulations, consumer demand and regulations, and advancement in veterinary medicine, research, and surveillance. For example, in the U.S., the Food and Drug Administration implemented regulations and changes due to antimicrobial resistance concerns between 1977 and 2017. These changes include banning certain antibiotics, phasing out some antibiotics, banning antibiotics for growth promotion, and approving new antibiotics . Additionally, collaborations between stakeholders, researchers, industries, and consumers might affect changing antimicrobial resistance patterns in retail meat . Recent studies and reports show that in the U.S., antimicrobial resistance patterns in retail meat in Salmonella depend on many factors, such as location antimicrobial usage claim . For example, Nyirabahizi et al. reported that antimicrobial-resistant Salmonella was more prevalent in the Northeastern part of the U.S. compared to other parts of the U.S.Antimicrobial susceptibility testing for detecting antimicrobial resistance in bacteria has served well for over 90 years since its invention . AST has been a foundation for therapy in medicine therapy and monitoring AMR trends . However, the antimicrobial susceptibility tests have the following limitations: long turnaround times ranging between 24 and 72 h, only selective antimicrobial agents can be tested, sometimes failure to detect resistance mechanisms, yield false-negative results, errors arising in inoculum preparation or culture conditions . Also, in some cases, assessing phenotypic resistance might not be sufficient to determine the risks of AMR. More advanced methods are needed to evaluate the underlying genetic factors and discover previously unknown resistant mechanisms, genetic variants, and mutations to control AMR and make decisions in therapeutic drug prescriptions . In recent years, with the cost of sequencing going down dramatically and quality improvement of sequencing, whole genome sequencing has become an essential and invaluable tool in tracing antimicrobial resistance, identifying resistance mechanisms, studying the evolution of resistance in real-time under a variety of conditions, design clinical trials, developing novel antibiotics and diagnostic tests . Countless studies, antimicrobial resistance monitoring programs, and government agencies worldwide have proved the effectiveness of WGS in confirming, tracking and controlling antimicrobial-resistant bacteria . Additionally, WGS has allowed investigation of the history and spread of antibiotic resistance Every disruptive technology also has flaws that need improvement and WGS is not an exception. Some studies identified the flaws of WGS in detecting and tracking AMR. They are the following: despite the price decrease, WGS is still relatively expensive, the data analysis process is very complex and time-consuming, undiscovered resistant mechanisms may not be found by existing databases and some mobile genetic elements cannot be captured . Application of WGS in routine health care has been slow due to its high cost . It is expected that the cost of sequencing will go down further, and sequencing technologies will improve over time . Therefore, there is a great chance that WGS will be gradually adopted as a universal tool for tracking and controlling AMR around the world.California is the most populated state in the U.S., with a population of nearly 40 million people, and is the fifth economy in the world. The population is diverse, and the Southern part of the state is densely populated compared to the Northern part of the state. California is the nation’s #1 agricultural state and livestock commodities account for 27% of it . Among the foodborne pathogens, Salmonella has been the leading cause of outbreaks and hospitalizations. Salmonella serotypes vary depending on geographic locations or places which is why 1475 of all serotypes have been given location names . This also means that antimicrobial patterns of Salmonella are different depending on geographic locations. To the best of our knowledge, only two studies characterized the antimicrobial pattern of Salmonella in California . However, the study conducted by was conducted 17 years ago, and only two sites in California had been sampled. Additionally, since that that time, many regulations have been issued by the FDA, banning antimicrobials as growth promoters and prohibiting the counter sale of some antimicrobials. The study conducted by has limitations because of the small sample size that prevented comprehensively characterizing Salmonella’s antimicrobial resistance patterns in California. Therefore, there is an urgent need for a thorough characterization of resistance patterns of Salmonella in California.WHO has been coordinating a global action plan on antimicrobial resistance to optimize the usage of antimicrobials in human and veterinary medicine. Also, the World Organization for Animal Health has devised a strategy for antimicrobial resistance and controlled use of antimicrobials in order to support the global action plan . Additionally, governments around the world also contribute to this plan by implementing a One Health approach to control and monitor AMR. For example, In 2007, the U.S. One Health Office was established in order to promote the One Health approach. The collaborative actions between CDC, the FDA, and the USDA have played a crucial role in addressing antimicrobial resistance. NARMS was established as part of the One Health approach to track resistance in Salmonella, Campylobacter, Escherichia coli, Enterobacteria, and other foodborne bacteria by sampling food-producing animals, retail meats and infectiously diseased humans .