Evaluation of Swine Protection with Three Commercial Foot-and-Mouth Disease Vaccines against Heterologous Challenge with Type A ASIA/G-VII Lineage Viruses.

Outbreaks caused by foot-and-mouth disease (FMD) A/ASIA/G-VII lineage viruses have often occurred in Middle Eastern and Southeast Asian countries since 2015. Because A/ASIA/G-VII lineage viruses are reported to have distinct antigenic relatedness with available commercial FMD vaccine strains, it is necessary to investigate whether inoculation with vaccines used in Korea could confer cross-protection against A/ASIA/G-VII lineage viruses. In the present study, we conducted two vaccination challenge trials to evaluate the efficacy of three commercial FMD vaccines (O/Manisa + O/3039 + A/Iraq, O/Campos + A/Cruzeiro + A/2001, and O/Primorsky + A/Zabaikalsky) against heterologous challenge with ASIA/G-VII lineage viruses (A/TUR/13/2017 or A/BHU/3/2017 strains) in pigs. In each trial, clinical signs, viremia, and salivary shedding of virus were measured for 7 days after challenge. In summary, the O/Campos + A/Cruzeiro + A/2001 vaccine provided full protection against two A/ASIA/G-VII lineage viruses in vaccinated pigs, where significant protection was observed. Although unprotected animals were observed in groups vaccinated with O/Manisa + O/3039 + A/Iraq or O/Primorsky + A/Zabaikalsky vaccines, the clinical scores and viral RNA levels in the sera and oral swabs of vaccinated animals were significantly lower than those of unvaccinated controls.

Escherichia coli Isolated from Bovine Sources Encoding the Fosfomycin Resistance Gene fosA7.5.

Dairy animals are reservoirs of antimicrobial-resistant Escherichia coli that are frequently resistant to tetracycline, aminoglycoside, ß-lactam, sulfonamide, and macrolide-lincosamide-streptogramin B antibiotics. However, resistance to other classes of antimicrobials is less frequently observed, and resistance to fosfomycin is rarely observed in E. coli. In this study, we describe the genomic characteristics of E. coli encoding fosA7.5 that have been recovered from bovine sources in the United States. Most isolates only encoded the fosA7.5 gene, whereas 37% encoded at least one other resistance gene, and 25% were genotypically multidrug-resistant. Most (112 isolates, 93%) belonged to phylogenetic group B1 and were assigned to 19 sequence types (STs), the most frequently identified being ST1727, ST2307, and ST3234. Results of this study indicate that fosA-encoding E. coli from bovine sources is very rare in the United States with isolates demonstrating a high level of similarity across a broad geographic region.

Microdiversity of Salmonella Kentucky During Long-Term Colonization of a Dairy Herd.

Salmonella enterica subsp. enterica serovar Kentucky was repeatedly isolated from a commercial dairy herd that was enrolled in a longitudinal study where feces of asymptomatic dairy cattle were sampled intensively over an 8-year period. The genomes of 5 Salmonella Kentucky isolates recovered from the farm 2 years before the onset of the long-term colonization event and 13 isolates collected during the period of endemicity were sequenced. A phylogenetic analysis inferred that the Salmonella Kentucky strains from the farm were distinct from poultry strains collected from the same region, and three subclades (K, A1, and A2) were identified among the farm isolates, each appearing at different times during the study. Based on the phylogenetic analysis, three separate lineages of highly similar Salmonella Kentucky were present in succession on the farm. Genomic heterogeneity between the clades helped identify regions, most notably transcriptional regulators, of the Salmonella Kentucky genome that may be involved in competition among highly similar strains. Notably, a region annotated as a hemolysin expression modulating protein (Hha) was identified in a putative plasmid region of strains that colonized a large portion of cows in the herd, suggesting that it may play a role in asymptomatic persistence within the bovine intestine. A cell culture assay of isolates from the three clades with bovine epithelial cells demonstrated a trend of decreased invasiveness of Salmonella Kentucky isolates over time, suggesting that clade-specific interactions with the animals on the farm may have played a role in the dynamics of strain succession. Results of this analysis further demonstrate an underappreciated level of genomic diversity within strains of the same Salmonella serovar, particularly those isolated during a long-term period of asymptomatic colonization within a single dairy herd.

Virulome analysis of Escherichia coli ST117 from bovine sources identifies similarities and differences with strains isolated from other food animals.

Escherichia coli ST117 is a pandemic extraintestinal pathogenic E. coli (ExPEC) causing significant morbidity globally. Poultry are a known reservoir of this pathogen, but the characteristics of ST117 strains from other animal sources have not been adequately investigated. Here we characterize the genomes of 36 ST117 strains recovered primarily from preweaned dairy calves, but also from older postweaned calves and lactating cows, in the context of other bovine-associated strains and strains from poultry, swine, and humans. Results of this study demonstrate that bovine-associated ST117 genomes encode virulence factors (VFs) known to be involved in extraintestinal infections, but also occasionally encode the Shiga toxin, a virulence factor (VF) involved in severe gastrointestinal infections and more frequently identified in E. coli from ruminants than other animals. Bovine-associated ST117 genomes were also more likely to encode afa-VIII (adhesins), pap (P-fimbriae), cdt (cytolethal distending toxin), and stx (Shiga toxins) than were poultry and swine-associated genomes. All of the ST117 genomes were grouped into seven virulence clusters, with bovine-associated genomes grouping into Clusters 1, 2, 4, 5, but not 3, 6, or 7. Major differences in the presence of virulence factors between clusters were observed as well. Antimicrobial resistance genes were detected in 112 of 122 (91%) bovine-associated genomes, with 103 of these being multidrug-resistant (MDR). Inclusion of genomes that differed from ST117 by one multi-locus sequence type (MLST) allele identified 31 STs, four of these among the bovine-associated genomes. These non-ST117 genomes clustered with the ST117 genomes suggesting that they may cause similar disease as ST117. Results of this study identify cattle as a reservoir of ST117 strains, some of which are highly similar to those isolated from other food animals and some of which have unique bovine-specific characteristics.