Post-weaning diarrhea commonly occurs in piglets and results in significant economic loss to swine producers. non-antibiotic measures for managing post-weaning diarrhea are critically needed. Duannai-An, a probiotic produced from the yeast fermentation of egg whites, was previously shown to optimize intestinal flora and reduce the incidence of clinical diarrhea in weaning piglets. To study the effects of Duan-Nai-An on mucosal integrity and immunity in pig intestine, we examined the microstructure and ultrastructure of the intestines of weaned pigs with or without Duan-nai-An as a feed supplement. the piglets of the Duan-nai-An-fed group developed intestines with intact columnar epithelia covered by tightly packed microvilli on the apical surface. However, piglets of the control group (no supplement) showed villous atrophy and thinning, microvillus slough, and in the severe cases, damage of intestinal epithelia and exposure of the underlying lamina propria. Moreover, piglets of the Duan-nai-An-fed group showed apparent plasmocyte hyperplasia, increased lymphoid nodule numbers, well-developed peyer's patchs, and apparent germinal centers. the lymphoid tissues of the control group were far less developed, showing lymph node atrophy, lymphocyte reduction, degeneration, and necrosis. these results indicate that Duan-nai-An improves the development of the intestinal structures and lymphoid tissues and promotes intestinal health in weaned piglets. The gastrointestinal (GI) tract is the largest immune organ in the body 1,2. The epithelial lining of the GI tract is the surface that is in close contact with the external environment. The GI tract also provides the microenvironment for the development and differentiation of the intestinal immune cells. The intestinal epithelial cells play important roles not only in food digestion and nutrient absorption, but also in immune defense and immune tolerance 3. More than 50% of the body's lymphoid tissue is distributed in the intestinal mucosa, bearing an important immune function and constituting the body's first barrier against pathogenic microorganism invasions 4. A diverse and large number of microorganisms are found in the GI tract. Gut microbiota play very important roles in the growth, anti-infection, immune regulation, metabolism and intestinal health of the host 5-8 , and most studies mainly focused on evaluating the impact of bacterial flora on animal nutrition 9-11. Recently, more and more work has been devoted to understanding the microbiota-intestinal mucosa interaction, how the interaction form a mechanical, immunological, and biological barrier against pathogen invasion and endotoxin translocation, and how gut microbiota modulates the development and function of the mucosal immune system 5,12-15. Weaning is one of the most stressful events in the swine production process and disturbs the intestinal flora of piglets, often compromising the intestinal structure and mucosal barrier 16. Because of the disruption, weaning piglets may have decreased intestinal mucosal im...

IntroductionNon-aureus Staphylococcus (NAS) species are currently the most commonly identified microbial agents causing sub-clinical infections of the udder and are also deemed as opportunistic pathogens of clinical mastitis in dairy cattle. More than 10 NAS species have been identified and studied but little is known about S. haemolyticus in accordance with dairy mastitis. The present study focused on the molecular epidemiology and genotypic characterization of S. haemolyticus isolated from dairy cattle milk in Northwest, China.MethodsIn this study, a total of 356 milk samples were collected from large dairy farms in three provinces in Northwest, China. The bacterial isolation and presumptive identification were done by microbiological and biochemical methods following the molecular confirmation by 16S rRNA gene sequencing. The antimicrobial susceptibility testing (AST) was done by Kirby-Bauer disk diffusion assay and antibiotic-resistance genes (ARGs) were identified by PCR. The phylogenetic grouping and sequence typing was done by Pulsed Field Gel Electrophoresis (PFGE) and Multi-Locus Sequence Typing (MLST) respectively.ResultsIn total, 39/356 (11.0%) were identified as positive for S. haemolyticus. The overall prevalence of other Staphylococcus species was noted to be 39.6% (141/356), while the species distribution was as follows: S. aureus 14.9%, S. sciuri 10.4%, S. saprophyticus 7.6%, S. chromogenes 4.2%, S. simulans 1.4%, and S. epidermidis 1.1%. The antimicrobial susceptibility of 39 S. haemolyticus strains exhibited higher resistance to erythromycin (92.3%) followed by trimethoprim-sulfamethoxazole (51.3%), ciprofloxacin (43.6%), florfenicol (30.8%), cefoxitin (28.2%), and gentamicin (23.1%). All of the S. haemolyticus strains were susceptible to tetracycline, vancomycin, and linezolid. The overall percentage of multi-drug resistant (MDR) S. haemolyticus strains was noted to be 46.15% (18/39). Among ARGs, mphC was identified as predominant (82.05%), followed by ermB (33.33%), floR (30.77%), gyrA (30.77%), sul1 (28.21%), ermA (23.08%), aadD (12.82%), grlA (12.82%), aacA-aphD (10.26%), sul2 (10.26%), dfrA (7.69%), and dfrG (5.13%). The PFGE categorized 39 S. haemolyticus strains into A-H phylogenetic groups while the MLST categorized strains into eight STs with ST8 being the most predominant while other STs identified were ST3, ST11, ST22, ST32, ST19, ST16, and ST7.ConclusionThese findings provided new insights into our understanding of the epidemiology and genetic characteristics of S. haemolyticus in dairy farms to inform interventions limiting the spread of AMR in dairy production.