Background Swine dysentery (SD) is a severe infectious disease with a relevant impact on pig production usually caused by Brachyspira hyodysenteriae, although B. hampsonii causes an identical clinical picture. SD control relies on antimicrobials, good management practices and strict biosecurity with cleaning and disinfection as crucial tools to avoid the pathogen transmission. This study evaluates the in-vitro efficacy of an array of commercial disinfectants against a collection of B. hyodysenteriae isolates using broth tests. The efficacy of cleaning and disinfection protocols was also evaluated on two farms with endemic SD using surface swabs collected in emptied pens before and after cleaning and disinfection procedures, using both real-time PCR and bacterial microbiological culture. Results Most of the commercial disinfectants evaluated were effective against all B. hyodysenteriae isolates tested, with a reduction of more than 5.00 log10 CFU/mL (bactericidal efficacy of 99.999%). However, some isolates exhibited reduced susceptibility to Virkon-S and Limoseptic disinfectants. The evaluation of cleaning and disinfection protocols on farms with SD outbreaks showed that approximately half the pens tested (n = 25) were positive by real-time PCR after pigs removal (mean B. hyodysenteriae counts 5.72 ± 1.04 log10 CFU/mL) while almost 20% of the pens remained positive after cleaning (n = 7) and disinfection (n = 5) procedures although with significantly lower, mean estimates (4.31 ± 0.43 log10 CFU/mL and 4.01 ± 0.55 log10 CFU/mL, respectively). Conclusions These results show the efficacy of disinfectants against B. hyodysenteriae but also stress the need to implement adequately the cleaning and disinfection protocols on pig farms and review and revise their efficiency periodically.

The aim of this study was to characterize the infection of weaned pigs with swine enteric coronavirus (SeCoV) – a chimeric virus most likely originated from a recombination event between porcine epidemic diarrhoea virus (PEDV) and transmissible gastroenteritis virus, or its mutant porcine respiratory coronavirus – and two PEDV G1b variants, including a recently described recombinant PEDV‐SeCoV (rPEDV‐SeCoV), as well as to determine the degree of cross‐protection achieved against the rPEDV‐SeCoV. For this purpose, forty‐eight 4‐week‐old weaned pigs were randomly allocated into four groups of 12 animals. Piglets within each group were primary inoculated with one of the investigated viral strains (B: PEDV; C: SeCoV and D: rPEDV‐SeCoV) or mock‐inoculated (A), and exposed to rPEDV‐SeCOV at day 20 post‐infection; thus, group A was primary challenged (‐/rPEDV‐SeCoV), groups B and C were subjected to a heterologous re‐challenge (PEDV/rPEDV‐SeCoV and SeCoV/rPEDV‐SeCoV, respectively), and group D to a homologous re‐challenge (rPEDV‐SeCoV/rPEDV‐SeCoV), Clinical signs, viral shedding, microscopic lesions and specific humoral and cellular immune responses (IgG, IgA, neutralizing antibodies and IgA and IFN‐γ‐secreting cells) were monitored. After primo‐infection, all three viral strains induced an undistinguishable mild‐to‐moderate clinical disease with diarrhoea as the main sign and villus shortening lesions in the small intestine. In homologous re‐challenged pigs, no clinical signs or lesions were observed, and viral shedding was only detected in a single animal. This fact may be explained by the significant high level of rPEDV‐SeCoV‐specific neutralizing antibodies found in these pigs before the challenge. In contrast, prior exposure to a different PEDV G1b variant or SeCoV only provided partial cross‐protection, allowing rPEDV‐SeCoV replication and shedding in faeces.

Background The treatment of swine dysentery (SD) has become constrained in recent years due to the limited availability of effective drugs combined with a rise in antimicrobial resistance. Gentamicin, an aminoglycoside antibiotic, is authorised for the control of this disease in several European countries but has not been extensively used so far. In this study, the in vitro susceptibility of 56 Brachyspira hyodysenteriae field isolates was evaluated against gentamicin using a broth microdilution test. The molecular basis of decreased susceptibility to gentamicin was also investigated by sequencing the 16S rRNA gene and phylogenetic relatedness by multiple-locus variable number tandem-repeat analysis (MLVA). Results Most B. hyodysenteriae isolates presented low minimum inhibitory concentration (MIC) values to gentamicin, with a mode of 2 µg/mL, a median or MIC50 of 4 µg/mL and percentile 90 or MIC90 of 16 µg/mL. The distribution of these values over the period studied (2011–2019) did not show a tendency towards the development of resistance to gentamicin. Differences in susceptibility among isolates could be explained by two point-mutations in the 16S rRNA gene, C990T and A1185G, which were only present in isolates with high MICs. These isolates were typed in three different MLVA clusters. Analyses of co-resistance between gentamicin and antimicrobials commonly used for the treatment of SD revealed that resistance to tiamulin and valnemulin was associated with low MICs for gentamicin. Conclusions The results provide an accurate characterisation of antimicrobial sensitivity to gentamicin and possible mechanisms of resistance in Spanish B. hyodysenteriae isolates. These findings allow us to propose gentamicin as an alternative in the antibiotic management of SD, particularly in outbreaks caused by pleuromutilin resistant isolates.