Antimicrobial Susceptibility Pattern of Porcine Respiratory Bacteria in Spain

Abstract

The monitoring of antimicrobial susceptibility of pig pathogens is critical to optimize antimicrobial treatments and prevent development of resistance with a one-health approach. The aim of this study was to investigate the antimicrobial susceptibility patterns of swine respiratory pathogens in Spain from 2017 to 2019. Bacterial isolation and identification were carried out following standardized methods from samples coming from sacrificed or recently deceased pigs with acute clinical signs compatible with respiratory tract infections. Minimum inhibitory concentration (MIC) values were determined using the broth microdilution method containing a total of 10 and 7–8 antimicrobials/concentrations respectively, in accordance with the recommendations presented by the Clinical and Laboratory Standards Institute (CLSI). The obtained antimicrobial susceptibility varies between pig respiratory pathogens. Actinobacillus pleuropneumoniae (APP) and Pasteurella multocida (PM) were highly susceptible (≥90%) to ceftiofur, florfenicol and macrolides (tilmicosin, tildipirosin and tulathromycin). However, the antimicrobial susceptibility was intermediate (>60% but <90%) for amoxicillin and enrofloxacin in the case of APP and sulfamethoxazole/trimethropim and tiamulin in the case of PM. Both bacteria showed low (<60%) antimicrobial susceptibility to doxycycline. Finally, Bordetella bronchiseptica was highly susceptible only to tildipirosin and tulathromycin (100%) and its susceptibility for florfenicol was close to 50% and <30% for the rest of the antimicrobial families tested. These results emphasize the need of determining antimicrobial susceptibility in pig respiratory cases in order to optimize the antimicrobial treatment in a case-by-case scenario.

Antimicrobial Stewardship for Respiratory Pathogens in Swine

“…400 samples were received from wean-to-finish and fattening farms across Spain of sow suffering clinical respiratory cases from 2017 to 2019. Bacterial isolation, as previously described in our former paper [ 15 ], was only possible in 80.3% (321/400) of the cases, and in 22% (88/400) of them, it was possible to isolate more than one bacterium. Finally, 162, 130, and 29 strains of APP, PM, and BB were included in this research work because it was not possible to determine the MIC value for GP due to the impossibility for this bacterium to grow with the microdilution technique.…”

“…Thus, Vilaro et al (2020) has recently established that there are still many options to treat infections by APP and PM with antimicrobials, but the presence of strains resistant to tetracyclines, aminopenicillins, and quinolones in the case of APP and tetracyclines, sulfamides and pleuromutilins in the case of PM should be taken into account to select the most suitable antimicrobial for each clinical case. Moreover, Bordetella bronchiseptica was highly susceptible only to tildipirosin and tulathromycin and its susceptibility for florfenicol was close to 50% and <30% for the rest of antimicrobials tested [ 15 ].…”

“…The distribution of antimicrobial susceptibility observed for these respiratory pathogens clearly shows that a proper diagnostics and sensitivity testing should be performed for each clinical case. On the other hand, it could be possible to propose general antimicrobial stewardship, not based on a case by case scenario, for any APP and/or PM strain, but this proposal must exclude doxycycline for both bacteria, aminopenicillins, and quinolones for APP and pleuromutilins and sulfamides for PM in order to obtain a good clinical outcome in almost all the clinical cases [ 15 ]. Unfortunately, this proposal would discard three antimicrobials (doxycycline, amoxicillin, and sulfamethoxazole/trimethoprim) that should be chosen as first option therapy if the MIC value is below their clinical breakpoints because they belong to D category, according to EMA [ 6 ].…”

“…For this reason, instead of proposing general antimicrobial stewardship for APP and PM, we propose to carry out a microbiological diagnosis for each clinical case to select the most suitable antimicrobials as first, second and last option therapy according to their MIC value and the European legislation about prudent use of antimicrobials [ 4 ]. In the case of BB, the number of antimicrobial options to treat this bacterial infection are very limited [ 15 ], and the antimicrobial stewardship based on each clinical case is the only option to select the most suitable antimicrobial treatment. Finally, antimicrobial susceptibility patterns can change with time [ 20 ], and it is one of the reasons to monitor it across time.…”

“…Samples were drawn from diseased or recently deceased pigs from farms across Spain showing acute clinical signs of respiratory tract infections that had not been exposed to antimicrobial treatment for at least, 15 days before sampling, between the years 2017 and 2019, as detailed in a previous paper of our research group [ 15 ].…”