Study of antibiotic susceptibility against the main pathogens involved in fattening lambs digestive and respiratory pathology in Spain and Portugal.

The increase of the antimicrobials resistance has become a global public health problem. In the EU, reduction policies have been implemented under the "One Health" concept that implies human and animal health. The monitoring of resistance in different animal species has become a priority within the strategies of fighting against resistance. Four hundred and twelve cases were analyzed from 2015 to 2019, coming from 121 lamb feedlot farms in Spain and Portugal. Several studies were carried out to obtain practical knowledge in order to reduce the use of antimicrobials as much as possible. Firstly, several comparative studies were carried out between samples from nasotracheal lavages and those obtained from lung tissue ("in farm examination necropsy") in order to check the suitability of this type of samples in monitoring the susceptibilities of the pathogens (Pasteurella multocida, Mannehimia haemolitica and Biberstenia threalosi) involved in respiratory problems. Secondly, another study was carried out in order to know the evolution along the years of the susceptibilities to some antibiotics of the most important pathogens (P. multocida, M. haemolitica, B. threalosi and Escherichia coli) involved both in respiratory and digestive diseases. Finally, a "map" of the susceptibilities of pathogens to a significant number of antibiotics available in the market were obtained. Similar results in susceptibility were found in most of the pathogens studied comparing lavages and tissue samples. Besides, similar evolution in susceptibility of pathogens to most antibiotics checked was observed, with an increment during 2018 and 2019. In general, tetracycline (very used by oral supply) gave less susceptibility than others did. On the opposite way, amoxicillin could be an antibiotic available for further oral use. In conclusion, the nasotracheal lavages are an efficient and valid method of taking suitable respiratory samples in practical conditions of monitoring. Besides, there is a tendency to the increment of the susceptibility of pathogens to a large part of antibiotics, in parallel to the reduction of the actual use of antimicrobials. Finally, the maps of susceptibilities provide very useful epidemiological information to be used in the strategies of antibiotic pressure reduction. [ABSTRACT FROM AUTHOR]