1. Investigación

Salmonella spp. is one of the most important zoonotic pathogens with economic impact in public health worldwide. The relevance of Salmonella increases with the appearance of resistant strains. The aim of this study was to determine the level of antimicrobial resistance in 332 Salmonella isolates selected from 3 different poultry productive orientations in Eastern Spain during 3 yr (2015−2017). Antimicrobial susceptibly was evaluated by broth microdilution method using 14 antibiotics. Epidemiological cut-off values (ECOFF) were used to evaluate the microbiological resistance to antibiotics. The rates of Salmonella resistance at least to one antibiotic were 96, 98, and 56% in broilers, turkeys, and layers, respectively. Regarding multidrug resistance, all productive orientations seems to present a decreasing trend along the study, being the mean rates 80% in turkeys followed by broilers (40%) and layers (6%). Throughout the study, the highest percentage of resistance was found to sulfamethoxazole in all productive orientations. Strains from broilers showed the highest resistance rates to sulfamethoxazole (73%), gentamicin (57%), ciprofloxacin (50%), nalidixic acid (29%), and tetracycline (24%). Relative to turkeys the highest resistance rates were to sulfamethoxazole (76%), ciprofloxacin (69%), tetracycline (75%), nalidixic acid (63%), and ampicillin (63%). Layers presented the most elevated resistance rates to sulfamethoxazole (39%) and tetracycline (13%). Regarding serovars the most MDR common serovars to the 3 productive orientations were S. Kentucky and S. Hadar. In the other hand, high MDR rates were found in other serovars like S. Infantis and S. Typhimurium in broilers and turkeys. Results shown in the present study suggest that the reduction in the use of antibiotics begins to be reflected in the reduction of the number of MDRs, especially in layers, with no MDR Salmonella strains in the last period. However, the level of resistances found in this study suggests the necessity of continuing working on the limitation of the use of antimicrobials in poultry to achieve (as in layers) the control of MDRs.

Salmonella is mostly noted as a food-borne pathogen, but contact with chelonians has also been reported as a source of infection. Moreover, high levels of antimicrobial resistance (AMR) have been reported in Salmonella isolated from wild and captive reptiles. The aim of this study was to assess the occurrence of Salmonella AMR carriage by chelonians admitted to two zoological institutions in Spain, characterizing the isolates to assess the Salmonella AMR epidemiology in wildlife. To this end, 152 chelonians from nine species were sampled upon their arrival at the zoological nuclei. Salmonella identification was based on ISO 6579-1:2017 (Annex D), isolates were serotyped and their AMR analysed according to the EU Decision 2013/652. Moreover, the genetic relationship of the isolates was assessed by pulsed-field gel electrophoresis (PFGE). Results showed 19% (29/152) of the chelonians positive to Salmonella, all of them tortoises. For all isolates, 69% (20/29) were resistant and 34% (10/29) multidrug-resistant (MDR) strains. PFGE clustered isolates according to the serovar, confirming a low genetic diversity. In conclusion, this study shows a high presence of MDR Salmonella strains in tortoises at their entry into zoological nuclei. This condition highlights the need to establish Salmonella detection protocols for the entry of animals into these centres.

Campylobacteriosis is the most commonly reported gastrointestinal disease in humans in the EU, mainly from poultry meat consumption. C. jejuni is the main species involved in the human disease. However, little is known about the role of swine meat in its epidemiology. Thus, the aim of this study was to assess the epidemiology and antimicrobial resistance of C. jejuni on swine processing at the slaughterhouse. To this end, a total of 21 pig herds were intensively sampled at the slaughterhouse. Campylobacter isolation was based on official method ISO 10272-1:2018, speciation was determined by the hippurate hydrolysis test, and antibiotic susceptibility was performed according to standard disc diffusion assay. The results showed that all batches shed Campylobacter in faeces upon arrival at the slaughterhouse and remained positive at the end of the slaughtering process (42.8%). Moreover, 41.5% of Campylobacter strains isolated were C. jejuni and all of them were resistant to at least one antibiotic, and 96.3% were multidrug-resistant strains. In conclusion, the high level of multidrug-resistant C. jejuni swine batch contamination at the slaughterhouse makes it necessary to include the swine sector in national control programmes to reduce the bacterium and its resistance.

Thermophilic Campylobacter spp. are recognized as a major cause of acute bacterial diarrhea in humans, with broiler meat being the most common source of human infection. Antibiotic therapy is usually necessary for severe or prolonged infections, especially in immunocompromised populations such as young or elderly individuals. However, different studies have demonstrated a close association between antibiotic use in animal production and antimicrobial resistance (AMR) in humans. In this sense, there is social pressure to reduce antibiotic administration and find adequate alternatives to control the presence of bacterial infections in farms. However, there is a lack of information related to Campylobacter AMR dynamics through the entire production system from breeders to their progeny. It is unknown if resistance genes are a result of adaptation through chromosomal mutation or through horizontal gene transfer, instead of vertical transmission of DNA from the parent to their progeny. Thus, the main objectives of this study were to assess the main AMR rates present in a poultry production system, to study the relationship between Campylobacter AMR profiles from breeders and their progeny, and to study the presence and distribution of antibiotic resistance genes in poultry production. Regarding AMR rates, ciprofloxacin was classified as extremely high, followed by nalidixic acid and tetracyclines that were classified as very high. Moreover, this study demonstrated a relationship between theAMR patterns and genes found from Campylobacter strains isolated in breeders and those present in their progeny.

Antimicrobial resistance (AMR) is an important threat to public health worldwide. Furthermore, different studies have demonstrated a close association between antibiotic use in animal production and AMR in humans. It is well known that it is necessary to reduce antibiotic administration in farms by finding effective alternative treatments, using more resistant breeds and improving animal welfare.However, to be able to assess the alternatives proposed, it is essential to study the epidemiology ofAMRunder production conditions.Hence, the aim of this study was to investigate the AMR dynamic in 2 genetic poultry breeds during the growing period. The study was performed in 2 experimental poultry houses to simulate real production conditions, and no antibiotics were administered during the growing period. In addition, 2 poultry breeds were used, fast-growing and slow-growing. To evaluate AMR evolution, Escherichia coli was selected as indicator bacterium. To this end, animals from each experimental groupwere sampled at different times: on day of arrival, at mid-period, and at slaughter day. In the laboratory, cecal content was removed and inoculated in selective media. Then, biochemical tests were performed to confirm E. coli. Finally, antibiotic susceptibility was assessed according toDecision 2013/653.At the onset of the cycle, significant differences were observed between breeds, as the E. coli strains isolated from fast-growing 1-day-oldchicks showed higherAMRrates.However, at the end of the period, no significant differences were found between breeds and their presence of resistant bacteria (above 95%). Therefore, although no antibiotics were administered during the growing period, a high level ofAMRat slaughter day was demonstrated. Further studies are necessary to determine the main risk factors that increase the level of AMR throughout the productive cycle in broiler chickens. In conclusion, it is important to highlight that although it is crucial to control both antibiotic use and animal welfare during the growing period, measures should be taken at all levels of the production chain.