Emerging resistance to florfenicol in Actinobacillus pleuropneumoniae isolates on two Italian pig farms.

Actinobacillus pleuropneumoniae is responsible for porcine pleuropneumonia, a highly contagious lung infection. The control of this respiratory disease remains heavily reliant on antibiotics, with phenicols being one of the primary classes of antibiotics used in pig farming. In the present study, we describe three isolates (B2278, B2176 and B2177) of A. pleuropneumoniae resistant to florfenicol attributed to the presence of the floR gene, which were obtained from two pig farms in Italy. Florfenicol susceptibility tests indicated that B2176 exhibited an intermediate susceptibility profile, while B2177 and B2278 were resistant. All three isolates belonged to serovar 6 and tested positive for the presence of the floR gene. Whole genome sequencing analysis revealed that isolates B2176, B2177 and B2278 harbored genes encoding the toxins ApxII and ApxIII, characteristic of strains with moderate virulence. Moreover, phylogenetic analysis demonstrated that these isolates were closely related, with single nucleotide polymorphisms (SNPs) ranging from 8 to 19. The floR gene was located on a novel 5588 bp plasmid, designated as pAp-floR. BLASTN analysis showed that the pAp-floR plasmid had high nucleotide identity (99 %) and coverage (60 %) with the pMVSCS1 plasmid (5621 bp) from Mannheimia varigena MVSCS1 of porcine origin. Additionally, at least under laboratory conditions, pAp-floR was stably maintained even in the absence of direct selective pressure, suggesting that it does not impose a fitness cost. Our study underscores the necessity of monitoring the spread of florfenicol-resistant A. pleuropneumoniae isolates in the coming years.

First detection of porcine circovirus type 2e in Europe.

Porcine circovirus 2 (PCV-2) infections are among the most economically important in swine farming. Because of the high evolutionary rate of PCV-2, several variants have emerged and are currently classified into several genotypes. However, only three (i.e. PCV-2a, PCV-2b, and PCV-2d) have a worldwide distribution, with other genotypes restricted to certain geographical regions and/or for limited time periods. Underdiagnosis or underreporting of these genotypes cannot be excluded. This is the first report of the detection and genetic characterisation of the PCV-2e genotype in Europe, from sows on a farm in Italy showing no clinical evidence of porcine circovirus disease. A follow-up study demonstrated persistent subclinical evidence of PCV-2e on the farm, at low frequency and viral load. This incidental finding emphasises the need for more intensive routine monitoring activities involving asymptomatic animals, coupled with DNA sequencing and data sharing. Considering the relevant genetic and phenotypic divergence of such genotypes, the actual efficacy of currently applied vaccines and diagnostic assays should be further evaluated.