This thesis is presented in three articles that represent three parallel studies on the use of antimicrobials and antimicrobial resistant bacteria (ARB) in pigs and the local environment in Peru. The overall aim of these three studies is to provide information, for the first time, on the occurrence of antimicrobial resistant bacteria and on the use of antimicrobials in pig farms in Peru. Since their discovery, antimicrobials have played a critical role in protecting human health. Resistance to antimicrobials is a consequence of the use of antimicrobials and, to a certain extent, is unavoidable because of bacteria's evolutionary capacity to survive. Antimicrobial use in the food animal industry, however, should be limited to those not critical for human use. Also, antimicrobial use and ARB should be controlled and monitored where continued use of antimicrobials takes place. Surveillance and monitoring networks are implemented in a number of developed countries, but developing countries generally lack policies and regulations to monitor and control this crisis. In order to provide information on the use of antimicrobials and ARB in pig farming in Peru, three studies were carried out. The first study aimed to provide information on antimicrobial use in pork production in Peru. The second study aimed to determine the presence of methicillin-resistant Staphylococcus aureus (MRSA) in pig farms in Peru. The third study aimed to determine the presence of vancomycin-resistant Enterococci (VRE) in pig farms and the surrounding environment in Lima, Peru.
In the first study, preliminary information regarding the consumption of antimicrobials in the swine industry in Peru was provided through four different sources. First, information on the quantities of imported antimicrobials was collected and collated from the Peruvian National Tax Administration (SUNAT). Second, data on registration of antimicrobials for animal use were obtained from the Agency for Animal Health (SENASA) for comparison purposes. Third, data on the general use of and farmers' attitudes about antimicrobial drugs in pigs were also obtained by interviewing swine farmers; also, use of antimicrobials was indirectly ascertained sampling feces of pigs for antimicrobial resistance (ampicillin, tetracycline, gentamycin, streptomycin, chloramphenicol, ciprofloxacin, cefoxitin) in bacteria (E. coli). Fourth, a pilot study evaluated the presence of antimicrobials in commercially farmed pork meat sampled at a slaughterhouse. The results of this study indicated that antimicrobials are used in pig farms and that ARB, specifically multi-drug resistant E. coli, is prevalent in pig farms in Peru.
The second study examined nasal swabs in ready-to-market pigs in Peru in large-scale confined pig production (LSCPP) and scavenging pigs (SP), as defined by the Food and Agriculture Organization , and found MRSA on both an LSCPP farm and an SP farm. Interestingly, MRSA isolates from the LSCPP farm were genetically identified as species type 398 (ST398), a livestock-associated MRSA (LA-MRSA) strain, and varied significantly from MRSA isolated from the SP farm, genetically identified as USA300 (ST8), a community-associated MRSA (CA-MRSA). These findings are the first to document ST398 in pigs in South America. In addition, finding ST8 in pigs in rural Peru elucidates a potential emerging zoonosis.
Finally, the third study showed for first time the presence of vancomycin-resistant Enterococci (VRE) in fecal samples of pigs and wilds birds in the surrounding environment in Lima, Peru. Vancomycin is the drug of choice for methicillin-resistant infections in humans, and finding VRE in pigs and wild birds creates some questions for future research: What is the prevalence of VRE in pig farms in Peru? Where is VRE coming from? How is VRE spreading in the environment? Who are the people at risk of acquiring VRE?
With the future aim of continuing to study antimicrobial resistance in Peru and with the ultimate goal of impacting agricultural policies for antimicrobial use in Peru, I present these three studies that reveal an emerging antimicrobial resistance threat in Peru.