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.

Forty-eight Pasteurella multocida isolates were recovered from porcine pneumonic lungs collected from farms in “Castilla y León” (north-western Spain) in 2017–2019. These isolates were characterized for their minimal inhibition concentrations to twelve antimicrobial agents and for the appearance of eight resistance genes: tetA, tetB, bla_ROB1, bla_TEM, ermA, ermC, mphE and msrE. Relevant resistance percentages were shown against tetracyclines (52.1% for doxycycline, 68.7% for oxytetracycline), sulphamethoxazole/trimethoprim (43.7%) and tiamulin (25.0%), thus suggesting that P. multocida isolates were mostly susceptible to amoxicillin, ceftiofur, enrofloxacin, florfenicol, marbofloxacin and macrolides. Overall, 29.2% of isolates were resistant to more than two antimicrobials. The tetracycline resistance genes (tetA and tetB) were detected in 22.9% of the isolates, but none were positive to both simultaneously; bla_ROB1 and bla_TEM genes were found in one third of isolates but both genes were detected simultaneously in only one isolate. The ermC gene was observed in 41.7% of isolates, a percentage that decreased to 22.9% for msrE; finally, ermA was harbored by 16.7% and mphE was not found in any of them. Six clusters were established based on hierarchical clustering analysis on antimicrobial susceptibility for the twelve antimicrobials. Generally, it was unable to foresee the antimicrobial susceptibility pattern for each family and the association of each particular isolate inside the clusters established from the presence or absence of the resistance genes analyzed.

Aims To perform the molecular characterization of 23 Staphylococcus aureus isolates from pigs with signs of infections recovered in Spanish farms during 2018–2019. Methods and Results The antimicrobial resistance pattern and virulence profile were determined. The molecular typing was performed by different molecular techniques. The transferability of the cfr gene was assessed by conjugation and its genetic environment was determined by PCR mapping. In all, 21 isolates were methicillin‐resistant S. aureus (MRSA) carrying the mecA gene (SCCmecV or non‐typeable SCCmec), whereas the remaining two were methicillin‐susceptible (MSSA). All but one MRSA isolates (n = 20) belonged to the CC398, being the spa t011 the most prevalent (n = 11). The remaining MRSA and the two MSSA isolates were ascribed to ST9/CC9. The S. aureus isolates exhibited resistance to (number of resistant isolates): β‐lactamics (21), erythromycin and/or clindamycin (20), aminoglycosides (7), tetracycline (22), fluoroquinolones (14), chloramphenicol (5) and linezolid (1). The S. aureus isolates did not carry any of the virulence genes studied. One MRSA belonging to the CC398 showed linezolid resistance mediated by the cfr gene. The cfr gene was co‐located with fexA in the Tn558 variant previously reported in the S. aureus plasmid pSCFS7. Conclusions Two major livestock‐associated genetic lineages were detected among pigs with signs of infection in Spain. The presence of the cfr gene among LA‐MRSA‐CC398 is of great concern not only for veterinary medicine, but also for humans in close contact. Significance and Impact of the Study This work describes the molecular characterization of S. aureus isolates recovered from pigs with signs of infection and we report, as far as we know, the first description of MRSA‐CC9 from pigs in Spain. Moreover, the detection of a MRSA‐CC398 isolate carrying the multiresistance cfr gene highlights the need for continuous surveillance and awareness of LA‐MRSA.

The aim of this study was to set up antimicrobial stewardship for swine respiratory pathogens following the recommendation from the European Medicine Agency. The obtained antimicrobial susceptibility pattern recommended using antimicrobial stewardship for each clinical case instead of treatment guidelines focused on pathogens. Thus, the bacteria are isolated and the MIC values, the clinical interpretation for each antimicrobial (susceptible or resistant), additional information about the distance between the MIC obtained and the clinical breakpoint, and set up for each drug, are represented in the report provided for veterinarians. A graph from green (susceptible) to red (resistant) is enclosed for each antimicrobial and microorganism in the report. The greener, the more susceptible is the strain, and the redder, the less susceptible is the strain for each particular antimicrobial. This information could help veterinarians to select the most suitable antimicrobial from first, second, or last option antimicrobials. Thus, veterinarians should choose the antimicrobial, inside each option, with the best antimicrobial susceptibility pattern that corresponds with the greener status in the report. The information provided in the report could be useful for all clinical cases, caused by a certain bacterium within the same pig production system, if an epidemiological link could be established.

Serovar detector is a new bioinformatic tool for determining the serovar of Actinobacillus pleuropneumoniae using whole genome sequencing. The composition of cps genes of isolates is compared to those of the serovar reference strains, and the outcome is determined both by the number of common genes and the similarities between the homologous genes. The validation of the bioinformatic tool utilized a broad collection of 732 isolates, including representatives from all described serovars. The isolates included had been characterized by conventional serotyping, PCR tests or different bioinformatic tools. The collection also includes isolates that have been difficult to allocate to a serovar using serology to test the performance of the Serovar detector when potential new varieties or combinations of cps genes are present. Out of the 732 isolates included in the investigation, only 36 isolates (4.9%) could not be allocated to the 19 recognized serovars. The validation showed that the Serovar detector is a robust method for determining the serovar of an isolate and a valuable tool for further characterization of the genetic heterogeneity both within serovars and within the A. pleuropneumoniae species.

The objective of the study was to analyse the antimicrobial susceptibility trends of Spanish porcine bacteria to quinolones, cephalosporins and polymyxins. Isolates of Actinobacillus pleuropneumoniae, Pasteurella multocida, and Escherichia coli were isolated from sick pigs from 2019 to 2022. Antimicrobial susceptibility test was determined by minimal inhibitory concentration (MIC) following internationally accepted methodology. MIC categorization was based on distributing the range of MIC values in four categories being category one the most susceptible (lowest MIC value) and four the less susceptible one (highest MIC value). Moreover, clinical susceptibility (susceptible/resistant) was also determined according to CLSI and EUCAST clinical breakpoints. A logistic and multinomial logistic regression model was used to analyze the susceptibility data for dichotomized and categorized MIC data, respectively for any pair of antimicrobial/microorganism. In general terms, the antimicrobial susceptibility of pig bacteria to these antimicrobials remained stable or increased in the last four years in Spain. In the case of A. pleuropneumoniae and quinolones, it was observed a significant temporal trend where isolates from 2020 had significantly increased odds of being more susceptible than isolates from 2019. In the case of E. coli and polymyxins, a significant temporal trend was observed where isolates from 2020 and 2021 had significantly increased odds of being more susceptible than isolates from 2019 and 2020, respectively. Finally, a significant odd of being less susceptible was only observed for cephalosporins and E. coli for 2020 versus 2019, stagnating for the rest of study period. These results provide sound data on critical important antimicrobials in swine medicine.