Avian Scavengers as Bioindicators of Antibiotic Resistance due to Livestock Farming Intensification

Antimicrobial resistance patterns of bacteria isolated from chicks of Canarian Egyptian vultures (Neophron percnopterus majorensis): A "one health" problem?

Antimicrobial resistance in Gram-negative bacteria isolated from cloacal samples of chicks of Canarian Egyptian vultures was investigated. Prevalence of Salmonella was also studied. Forty-seven isolates, obtained from 23 animals, were analysed. Escherichia coli (n = 29), Proteus mirabilis (n = 17) and Salmonella spp. (n = 1) were identified using API 20E system. Antimicrobial susceptibility to 13 antibiotics included in nine different categories was determined using disk-diffusion technique. The higher percentages of susceptible E. coli isolates were found for aminoglycosides and cefoxitin, and the lower ones were found for ampicillin, enrofloxacin and tetracycline. Proteus mirabilis isolates were susceptible to most of antimicrobials tested. Multidrug resistance patterns were found in 13 E. coli and four Proteus mirabilis. Salmonella spp. was detected in one chick (4.37%), and the isolate was also resistant to ampicillin and tetracycline. Thirteen E. coli isolates and four Proteus isolates showed a multidrug-resistance pattern, being resistant at least to one antibiotic in three or more different antimicrobial categories. This high level of antibiotic resistance in chickens of an endangered bird may be a limitation for possible treatments of infections in this species, as well as representing a source of resistant bacteria for animal care staff and for other animals in wildlife recovery centres. A "One Health" approach to this problem is necessary to reduce the levels of antimicrobial resistance in wild birds.

Аntibiotic resistance of bacterial cultures isolated from the feral pigeon (Columba livia) and starling (Sturnus vulgaris) at a solid waste landfill

Resistance to antibiotics is well-known global phenomenon. There are places contributing to the development of antibiotic resistance such as waste landfills, especially ones that accept medical waste which did not undergo disinfection and livestock waste with bacteria not sensitive to antibiotics. An extensive system of transfer of antibiotic resistant microorganisms is formed on these territories (zoochory, groundwater, transport etc.). The aim of the research was to determine the species composition of bacteria isolated from birds of Derhachi municipal solid waste landfills in Kharkiv city, Ukraine. Also, we determine the sensitivity of bacterial isolates to a number of standard antibiotic drugs. We collected droppings of feral pigeons (Columba livia Gmelin, 1789; Columbidae) and starlings (Sturnus vulgaris Linnaeus, 1758; Sturnidae) during the winter period in 2020/2021; both species are dominants of waste landfills. We isolated 15 bacteria species of 4 families by bacteriological methods (growing on simple and selective media and identification by biochemical properties): Enterobacteriaceae (Enterobacter asburiae, E. dissolvens, E. cancerogenus, E. cloacae, E. sakazakii, Escherichia coli, Klebsiella terrigena, K. ornithinolytica, Citrobacter freundii, Proteus mirabilis), Yersiniaceae (Serratia ficaria, S. rubidaea, S. entomophila), Morganellaceae (Providencia stuartii) and Pseudomonadaceaе (Pseudomonas aeruginosa). Sensitivity was determined by the disk-diffusion method to 18 antibiotics. Ten isolates turned out to be multiresistant-resistant to three or more classes of antimicrobial drugs. A promising direction for future research is the determination of the pathogenicity of the isolates and checking the roles of birds of Derhachi solid waste landfills as reservoirs of pathogens. Currently, it can be assumed that large concentrations of synanthropic birds (especially those that forage on solid waste landfills) with a high probability are reservoirs of many bacteria, in particular those that have developed resistance to drugs.

Eurasian griffon vultures carry widespread antimicrobial resistant Salmonella and Campylobacter of public health concern

The global emergence of antimicrobial-resistant (AMR) strains of Salmonella and Campylobacter is a serious public health concern. Both bacteria are leading causes of human gastrointestinal foodborne infections and the two most reported zoonoses in the European Union. By feeding on livestock carcasses, especially from intensive farming, as well as on landfill sites, obligate avian scavengers can become infected with zoonotic pathogens and AMR strains, and can be considered large-scale sentinels of the environmental burden. In this study, we assessed the occurrence and AMR of Salmonella spp. and Campylobacter spp. in 218 Eurasian griffon vultures (Gyps fulvus) captured in north-eastern Spain. We isolated Salmonella from 8.1 % of individuals and Campylobacter lari from 4.7 %. Among the 10 different Salmonella serovars found, monophasic S. Typhimurium was the most frequent. Genotyping analysis revealed same strains of monophasic S. Typhimurium shared by gulls, livestock and humans. Isolates from both bacterial species presented AMR to important antimicrobials (tetracyclines, fluoroquinolones and β-lactams). In conclusion, this study shows that Eurasian griffon vultures in north-eastern Spain are carriers of widespread AMR zoonotic Salmonella and Campylobacter. More comprehensive analyses are still needed to understand the potential risk of spill-over from those wild birds to humans.

Wildlife and Antibiotic Resistance

Antibiotic resistance is a major human health problem. While health care facilities are main contributors to the emergence, evolution and spread of antibiotic resistance, other ecosystems are involved in such dissemination. Wastewater, farm animals and pets have been considered important contributors to the development of antibiotic resistance. Herein, we review the impact of wildlife in such problem. Current evidence supports that the presence of antibiotic resistance genes and/or antibiotic resistant bacteria in wild animals is a sign of anthropic pollution more than of selection of resistance. However, once antibiotic resistance is present in the wild, wildlife can contribute to its transmission across different ecosystems. Further, the finding that antibiotic resistance genes, currently causing problems at hospitals, might spread through horizontal gene transfer among the bacteria present in the microbiomes of ubiquitous animals as cockroaches, fleas or rats, supports the possibility that these organisms might be bioreactors for the horizontal transfer of antibiotic resistance genes among human pathogens. The contribution of wildlife in the spread of antibiotic resistance among different hosts and ecosystems occurs at two levels. Firstly, in the case of non-migrating animals, the transfer will take place locally; a One Health problem. Paradigmatic examples are the above mentioned animals that cohabit with humans and can be reservoirs and vehicles for antibiotic resistance dissemination. Secondly, migrating animals, such as gulls, fishes or turtles may participate in the dissemination of antibiotic resistance across different geographic areas, even between different continents, which constitutes a Global Health issue.

Antibiotic Resistance Genes in Lemur Gut and Soil Microbiota Along a Gradient of Anthropogenic Disturbance

The overuse of man-made antibiotics has facilitated the global propagation of antibiotic resistance genes in animals, across natural and anthropogenically disturbed environments. Although antibiotic treatment is the most well-studied route by which resistance genes can develop and spread within host-associated microbiota, resistomes also can be acquired or enriched via more indirect routes, such as via transmission between hosts or via contact with antibiotic-contaminated matter within the environment. Relatively little is known about the impacts of anthropogenic disturbance on reservoirs of resistance genes in wildlife and their environments. We therefore tested for (a) antibiotic resistance genes in primate hosts experiencing different severities and types of anthropogenic disturbance (i.e., non-wildlife animal presence, human presence, direct human contact, and antibiotic treatment), and (b) covariation between host-associated and environmental resistomes. We used shotgun metagenomic sequencing of ring-tailed lemur (Lemur catta) gut resistomes and associated soil resistomes sampled from up to 10 sites: seven in the wilderness of Madagascar and three in captivity in Madagascar or the United States. We found that, compared to wild lemurs, captive lemurs harbored greater abundances of resistance genes, but not necessarily more diverse resistomes. Abundances of resistance genes were positively correlated with our assessments of anthropogenic disturbance, a pattern that was robust across all ten lemur populations. The composition of lemur resistomes was site-specific and the types of resistance genes reflected antibiotic usage in the country of origin, such as vancomycin use in Madagascar. We found support for multiple routes of ARG enrichment (e.g., via human contact, antibiotic treatment, and environmental acquisition) that differed across lemur populations, but could result in similar degrees of enrichment. Soil resistomes varied across natural habitats in Madagascar and, at sites with greater anthropogenic disturbance, lemurs and soil resistomes covaried. As one of the broadest, single-species investigations of wildlife resistomes to date, we show that the transmission and enrichment of antibiotic resistance genes varies across environments, thereby adding to the mounting evidence that the resistance crisis extends outside of traditional clinical settings.

Multidrug-Resistant Phenotypes of Escherichia coli Isolates in Wild Canarian Egyptian Vultures (Neophron percnopterus majorensis)

Simple Summary

Increasing antimicrobial resistance is a global problem for both human and animal health. Escherichia coli is frequently used as a “sentinel” for antimicrobial resistance and as an indicator of faecal contamination of the environment. This study is a characterisation of the antimicrobial resistance phenotypes of E. coli isolates obtained from cloacal samples of Canarian Egyptian vultures. A total of 65 chickens and 38 adult and immature birds were studied. Antimicrobial susceptibility to 16 antibiotics of 12 different categories was determined in 103 E. coli isolates. We found a 39.8% prevalence of multidrug-resistant (MDR) E. coli. Almost all MDR phenotypes found included resistance to tetracycline, an antibiotic widely used in veterinary medicine. Resistance has also been found to chloramphenicol (13 MDR phenotypes), imipenem (5 MDR phenotypes) and others. Wild birds can act as reservoirs and disseminators of MDR E. coli, transferring them via faeces to the environment, feed or water. Our results highlight the need to minimise exposure of wild birds to antimicrobials from human activities to avoid the spread of antimicrobial resistance.

Abstract

The presence of multidrug-resistant (MDR) Escherichia coli in cloacal samples from Canarian Egyptian vultures was investigated. Samples were obtained from chicks (n = 65) and from adults and immature birds (n = 38). Antimicrobial susceptibility to 16 antibiotics included in 12 different categories was determined for 103 E. coli isolates. MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories. Forty-seven different resistance phenotypes were detected: 31 MDR (41 isolates) and 16 non-MDR (62 isolates). One isolate was resistant to all 12 antimicrobial categories and 2 phenotypes included resistance to 9 antimicrobial categories. Imipenem resistance was included in five MDR phenotypes, corresponding to five different isolates. Statistically significant differences in prevalence of MDR-phenotypes were found between chicks in nests and the rest of the animals, probably due to the shorter exposure time of chicks to antimicrobials. The main risk derived from MDR bacteria in scavengers is that it threatens the treatment of wild animals in rescue centres and could be transferred to other animals in the facilities. In addition to this, it could pose a health risk to veterinarians or other staff involved in wildlife protection programmes.

Seasonal and spatial occurrence of zoonotic Salmonella serotypes in griffon vultures at farmland environments: Implications in pathogen pollution and ecosystem services and disservices

Livestock production is a large source of microbial, pharmaceutical, and antimicrobial pollution worldwide. Vultures are one group of birds with particularly high exposure to food-borne pathogens due to frequent consumption of infected livestock carcasses. The potential origin and spatial-temporal shedding patterns of livestock-adapted Salmonella serotypes of zoonotic importance were evaluated in adult and nestling Griffon vultures (Gyps fulvus). We specifically assessed the exposure source and subsequent elimination of Salmonella-infected carcasses (ecosystem services) or transmission back to livestock (ecosystem disservices) by vultures, thus contributing respectively to disease mitigation or amplification in natural and farmed environments. The results show a seasonal high occurrence and turnover of a high variety of serotypes, especially swine-adapted ones isolated at high frequency. This suggests that vultures can be reservoirs and long-distance carriers of faecal Salmonella shed in supplementary feeding stations and breeding colonies. Contrary to their conservation purposes, feeding stations can act as Salmonella hotspots and reservoirs. However, a role for vultures in the transmission back to food-producing animals seems impossible because they do not come into contact at indoor farms, while transmission to free-ranging ruminants was not supported by the presence of ruminant-adapted serotypes in the vultures. Therefore, vultures do not promote disservices associated with the re-infection of livestock with Salmonella, but can provide quantitatively important ecosystem services by removing carrion contaminated with these and other zoonotic pathogens potentially affecting their health. Sanitary vigilance of the farms authorised to provide food for avian scavengers should avoid the disposal of swine and poultry carcasses with Salmonella and the antibiotics used to treat it. Extensive free-ranging livestock and their carcasses exploited in the countryside should be a priority for the conservation of vultures and their ecological function as cleaners and disease mitigators.

Intensive farming as a source of bacterial resistance to antimicrobial agents in sedentary and migratory vultures: Implications for local and transboundary spread

The role of wild birds in the carriage and transmission of human and food animal bacteria with resistant genotypes has repeatedly been highlighted. However, few studies have focussed on the specific exposure sources and places of acquisition and selection for antimicrobial-resistant bacteria in vultures relying on livestock carcasses across large areas and different continents. The occurrence of bacterial resistance to antimicrobial agents was assessed in the faecal microbiota of sedentary Griffon vultures (Gyps fulvus) and trans-Saharan migratory Egyptian vultures (Neophron percnopterus) in central Spain. High rates (generally >50%) of resistant Escherichia coli and other enterobacteria to amoxicillin, cotrimoxazole and tetracycline were found. About 25-30% of samples were colonised by extended-spectrum beta-lactamases (ESBL) producing bacteria, while 5-17% were positive for plasmid mediated quinolone resistance (PMQR) phenotypes, depending on vulture species and age. In total, nine ESBL types were recorded (7 in griffon vultures and 5 in Egyptian vultures), with CTX-M-1 the most prevalent in both species. The most prevalent PMQR was mediated by qnrS genes. We found no clear differences in the occurrence of antimicrobial resistance in adult vultures of each species, or between nestling and adult Egyptian vultures. This supports the hypothesis that antimicrobial resistance is acquired in the European breeding areas of both species. Bacterial resistance can directly be driven by the regular ingestion of multiple active antimicrobials found in medicated livestock carcasses from factory farms, which should be not neglected as a contributor to the emergence of novel resistance clones. The One Health framework should consider the potential transboundary carriage and spread of epidemic resistance from high-income European to low-income African countries via migratory birds.