Photobacterium damselae subsp. piscicida (Pdp) is one of the major bacterial pathogens affecting marine aquaculture worldwide. This study presents, to our knowledge, the first comparative genomic characterization of a Pdp strain (KLC25) isolated in Türkiye in the context of publicly available genomes from different geographic regions. Average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) analyses supported the taxonomic assignment of KLC25 to P. damselae. Whole-genome phylogeny positioned KLC25 closest to the isolates MT1415 (Italian) and DI21 (Spanish), whereas core genome phylogeny clustered it with the Cypriot strain BIC8 and the Greek strain GalP1, revealing differences in clustering between whole- and core-genome approaches. Plasmid-associated sequences homologous to pPHDP10, pPHDP70 and pPHDPT3 were also detected in KLC25. Comparative analysis of the prophage regions predicted in KLC25 revealed similarities to phages from different Pdp strains, with most regions showing their highest sequence similarity to phages associated with different strains. While virulence-related determinants were highly conserved across the analyzed genomes, anti-phage defense systems and acquired antimicrobial resistance genes exhibited greater variability. Overall, this study expands our understanding of the genomic diversity and evolution of Pdp and provides a valuable resource for future investigations into its pathogenicity and epidemiology.
Staphylococcus pseudintermedius (SP) is an important opportunistic pathogen in companion animals, and the increasing prevalence of antimicrobial-resistant strains highlights the need for alternative approaches to local infection control. This study evaluated a topical hydrogel containing feline-derived Lactiplantibacillus plantarum ZYpet-014 and Aloe vera polysaccharides (AVEs) for the treatment of SP-infected wounds. AVEs promoted LP growth and organic-acid production and improved short-term LP viability within the carbomer hydrogel. The LP+AVE-hydrogel inhibited planktonic SP growth and biofilm formation in vitro and caused pronounced morphological disruption of SP cells. Therapeutic efficacy was further evaluated using a full-thickness murine wound model challenged with SP. LP+AVE treatment accelerated wound closure, reaching 95.75% by day 14, while qualitative histological observations suggested improved tissue organization and differences in collagen-associated staining patterns. Treatment was also associated with reduced TNF-α, IL-1β, and IL-6 levels and increased IL-4, IL-10, TGF-β1, and serum VEGF concentrations. In wound tissues, LP+AVE treatment decreased CD80 and increased CD206 immunoreactivity, consistent with a shift in macrophage-associated responses toward a reparative profile. Moreover, 16S rRNA gene sequencing showed reduced relative abundance of Staphylococcus and increased relative abundance of Lactobacillus in treated wounds. Together, these findings demonstrate antibacterial and antibiofilm activities against SP in vitro, accompanied by improved wound healing, modulation of inflammatory responses, and changes in wound microbial composition in vivo, although direct reduction in SP burden in wound tissue remains to be established.
Mare’s milk and fermented mare’s milk are potential sources of yeasts for probiotic screening. This study evaluated the in vitro probiotic potential of 23 yeast isolates from these sources. MALDI-TOF MS preliminarily identified 15 isolates as Kluyveromyces marxianus, four as Pichia manshurica, two as Pichia fermentans, one as Saccharomyces cerevisiae and one as Yarrowia lipolytica. Stress tolerance, solvent affinity, autoaggregation, coaggregation, hemolytic activity, and cell-free supernatant-mediated antibacterial activity were assessed. Relative viable counts, calculated against corresponding controls at the same 4-h endpoint, averaged below 6% under 0.3% bile salt exposure and below 1% at pH 2. Responses at pH 3 and elevated temperatures were variable. Solvent affinity ranged from 2.50% to 95.07%, with differences among isolates within each solvent (all p < 0.001). Autoaggregation ranged from 7.50% to 95.40% after 4 h. Coaggregation reached approximately 55% with Escherichia coli, 49% with Salmonella Enteritidis, and 50% with Staphylococcus aureus. Supernatants from 10 isolates inhibited at least one indicator bacterium, and six inhibited all three. R3-4 produced the numerically largest mean inhibition zone against S. aureus (19.3 ± 1.2 mm). No detectable hemolysis was observed. An exploratory five-domain score highlighted R3-4 (putative Y. lipolytica) and four putative K. marxianus isolates, without indicating superiority across all traits. These phenotypic profiles inform further screening, molecular confirmation, comprehensive safety assessment, and equine-relevant functional validation remain necessary.
Erysipelothrix rhusiopathiae causes sporadic, often fatal septicaemia in cetaceans; published cases rest almost entirely on cultured isolates, and none has included post-mortem imaging. We investigated a juvenile male short-beaked common dolphin (Delphinus delphis) stranded on Jeju Island, Republic of Korea, using post-mortem computed tomography (PMCT) of the frozen carcass, necropsy, histopathology and tiered molecular testing. Rhomboid skin lesions extended through the skin into the blubber. PMCT documented gravity-dependent pulmonary opacification, fluid in the trachea and bronchi, peritoneal effusion, no decomposition gas and a gastric fishing hook, confirmed at necropsy. Culture was not attempted because the carcass had been stored frozen. Erysipelothrix spp. DNA was detected by broad-range 16S rRNA sequencing in 11 of 12 tissues, and E. rhusiopathiae was identified by species-specific PCR and amplicon sequencing in all 12 tissues, yielding one identical 356-bp sequence. Histopathology showed epidermal coagulative necrosis with septal panniculitis and abundant Gram-positive bacteria throughout the lesion, pulmonary haemorrhage and oedema, interstitial nephritis and reactive lymphadenitis, consistent with fatal septicaemia. The case provides imaging correlates of erysipelas, a culture-independent diagnostic framework for frozen carcasses and a tissue-by-tissue molecular dataset; the relationship of the strain to other Korean cetacean isolates remains to be established genomically.
Diarrheic calves can harbor E. coli with diverse antimicrobial resistance and virulence characteristics, complicating disease treatment and control. This study characterized antimicrobial resistance, resistance and virulence genes, phylogenetic groups, and experimental mouse lethality of E. coli isolated from diarrheic calves on two large-scale cattle farms in Hebei Province, China. Fecal samples from 102 diarrheic calves were examined. Antimicrobial susceptibility was tested by the Kirby–Bauer disk diffusion method, resistance and virulence genes and phylogenetic groups were determined by PCR, and lethality was evaluated in a mouse challenge model. Forty-five E. coli isolates were recovered (44.1%), mainly from phylogroup B1 (64.4%), followed by A (22.2%) and B2 (13.3%). Resistance was highest to ceftriaxone (26.7%), followed by ceftazidime (24.4%), ampicillin (22.2%) and tetracycline (13.3%), and 15.6% of isolates were multidrug resistant. blaTEM was detected in all isolates, based on generic PCR detection, while sul1, tetA, blaCTX-M-1, tetB, blaCTX-M-55, and qnrS occurred at 2.2–17.8%. Based on PCR detection of toxin-associated markers, isolates were assigned as molecular ETEC (n = 9), molecular STEC (n = 10), molecular ETEC/STEC hybrids (n = 6), or Other (n = 20). Twenty isolates (44.4%) showed high lethality in mice. These findings reveal substantial heterogeneity in antimicrobial resistance, virulence, and experimental lethality among calf-derived E. coli.
