Antioxidative Sirt1 and the Keap1-Nrf2 Signaling Pathway Impair Inflammation and Positively Regulate Autophagy in Murine Mammary Epithelial Cells or Mammary Glands Infected with Streptococcus uberis.

Streptococcus uberis mastitis in cattle infects mammary epithelial cells. Although oxidative responses often remove intracellular microbes, S. uberis survives, but the mechanisms are not well understood. Herein, we aimed to elucidate antioxidative mechanisms during pathogenesis of S. uberis after isolation from clinical bovine mastitis milk samples. S. uberis's in vitro pathomorphology, oxidative stress biological activities, transcription of antioxidative factors, inflammatory response cytokines, autophagosome and autophagy functions were evaluated, and in vivo S. uberis was injected into the fourth mammary gland nipple of each mouse to assess the infectiousness of S. uberis potential molecular mechanisms. The results showed that infection with S. uberis induced early oxidative stress and increased reactive oxygen species (ROS). However, over time, ROS concentrations decreased due to increased antioxidative activity, including total superoxide dismutase (T-SOD) and malondialdehyde (MDA) enzymes, plus transcription of antioxidative factors (Sirt1, Keap1, Nrf2, HO-1). Treatment with a ROS scavenger (N-acetyl cysteine, NAC) before infection with S. uberis reduced antioxidative responses and the inflammatory response, including the cytokines IL-6 and TNF-α, and the formation of the Atg5-LC3II/LC3I autophagosome. Synthesis of antioxidants determined autophagy functions, with Sirt1/Nrf2 activating autophagy in the presence of S. uberis. This study demonstrated the evasive mechanisms of S. uberis in mastitis, including suppressing inflammatory and ROS defenses by stimulating antioxidative pathways.

Quercetin protects cadmium-induced renal injuries in mice by inhibiting cell pyroptosis.

The toxic heavy metal cadmium (Cd) has a significant impact on kidney health. Documents manifested that non-toxic flavonoid quercetin can reduce Cd-induced kidney damage by reducing oxidative stress and inhibiting apoptosis, while the effect of quercetin on Cd-induced renal cell pyroptosis has not been elucidated. In this study, we established a model of Cd poisoning treated with quercetin both in vitro and in vivo. Results revealed that quercetin effectively reversed the decrease in Cd-induced cell viability. Furthermore, Cd increased blood urea nitrogen while reducing GPX and SOD levels, caused histopathological injuries in kidney with a significantly elevated cell pyroptosis characterized by enhanced levels of proteins representing assembly (NLRP3) and activation (pro IL-1ß, cleaved IL-1ß, and IL-18) of NLRP3 inflammasome as well as pyroptosis executor (pro caspase-1, cleaved caspase-1). However, quercetin administration alleviated kidney injuries above by decreasing cell pyroptosis. Overall, it suggests that kidney cells are susceptible to pyroptotic cell death due to Cd exposure; while quercetin exhibits protective effects through cell pyroptosis inhibition.

Fungi, including Pithomyces chartarum cause facial eczema and inflammation in grazing sheep in Western China.

Facial eczema is often found in flocks of grazing sheep in China. To investigate fungi species those cause disease and pathological roles. Forage and soil samples were collected during the pathogenic season and cultured. Samples were collected from regions with and without facial eczema affected sheep. Fungal isolation and identification, statistical analysis of fungal species and distribution were performed. Pathological changes, biochemical parameters of serum liver function and protection of inflammatory factors that tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-12 (IL-12) were observed. Fungal cultivation and identification showed that separation rate of Alternaria, Pithomyces chartarum, Fusarium and Aspergillus were higher, particularly, Pithomyces chartarum was significantly identical. Pathological anatomy and histology indicated that the disease likely attacked merino ewes with the age of 6 months old. The clinical manifestations were characterized by inflammational edema in face (ears and eyelids) and mandibular area. Postmortem examination of dead lambs showed enlargement of liver with yellow white patchs of necrotic lesion and tuberous sclerosis and fibrosis on section. Histologic examination of liver showed extravasated blood, severe lesion of liver cells and bile duct, and fatty degeneration. In sheep, fungal toxin induced the secretion of TNF-α, IL-6 and IL-12. These results revealed that Pithomyces chartarum maybe caused facial eczema and inflammation in sheep. The facial eczema was allergic eczema caused by hepatic dysfunction and hepatonecrosis.

The prevalence of coagulase-negative staphylococcus associated with bovine mastitis in China and its antimicrobial resistance rate: a meta-analysis.

To contribute to the treatment decision and optimize coagulase-negative staphylococcus (CNS) control programs, we conducted a meta-analysis to investigate the epidemiology and antimicrobial resistance rates of coagulase-negative staphylococcus associated with bovine mastitis in China. Three databases (PubMed, Google scholar and China National Knowledge Infrastructure database) were utilized to obtain relevant publications. A total of 18 publications were included in our research, and 3 of them included antimicrobial resistant (AMR) test. The pooled prevalence of coagulase-negative staphylococcus was 17.28%. Subgroup analysis revealed that the prevalence was higher in South China than in North China, was higher in 2011-2020 than in 2000-2010 and was higher in clinical bovine mastitis cases than in subclinical cases. The pooled AMR were most resistant to ß-lactams, followed by tetracyclines, quinolones, nitrofurans, lincosamides, sulfonamides, amphenicol and aminoglycosides. The pooled AMR rate of coagulase-negative staphylococcus was lower in 2011-2020 than in 2000-2010. Although the prevalence of CNS showed an increasing trend over 20 years, the AMR rate showed a decreasing trend, and the clinical type of mastitis was the most frequent and the prevalence was highest in South China. Finally, CNS was most resistant to ß-lactams amongst the eight groups of antimicrobial agents.

The prevalence of bovine mastitis-associated Staphylococcus aureus in China and its antimicrobial resistance rate: A meta-analysis.

In this study, to optimize the Staphylococcus aureus control program, a meta-analysis was conducted to investigate the epidemiology and antimicrobial resistance (AMR) profile of S. aureus-associated bovine mastitis in China from 2000 to 2020. A total of 33 publications from PubMed, Google Scholar, and China National Knowledge Infrastructure (CNKI) database were included in our research, among which nine publications included the AMR test. The pooled prevalence of S. aureus was 36.23%, and subgroup analysis revealed that the prevalence dropped from 2000-2010 to 2011-2020, which shows that China is on the right track. The pooled AMR rate indicate isolates were most resistant to ß-lactams (50.68%), followed by quinolones (36.23%), macrolides (34.08%), sulfonamides (32.25%), tetracyclines (27.83%), aminoglycosides (26.44%), lincosamides (23.39%), and amphenicol (10.33%). Both the pooled prevalence and AMR of S. aureus in China are higher than those in Western countries, such as Germany, Belgium, Ireland, and the United States-countries with a long animal husbandry history and good management. Thus, there is still room to improve the treatment of S. aureus-associated bovine mastitis in China.

The Prevalence of Klebsiella spp. Associated With Bovine Mastitis in China and Its Antimicrobial Resistance Rate: A Meta-Analysis.

Understanding distribution of bovine mastitis pathogen Klebsiella spp. can contribute to the treatment decision and the control within programs of bovine mastitis, we conducted a meta-analysis to investigate the epidemiology and antimicrobial resistance rates of Klebsiella spp. associated with bovine mastitis in China. Three databases, namely, PubMed, Google scholar, and China National Knowledge Infrastructure database, were utilized to obtain relevant publications. According to PRISMA reporting standards, a total of 38 publications were included in the research, among them, 7 papers included an AMR test. The pooled prevalence of Klebsiella spp. was 5.41% (95% CI: 3.87-7.50%). Subgroup analysis revealed that the prevalence was higher in South China (8.55%, 95% CI: 3.57-19.09%) than in North China (4.22%, 95% CI: 2.46-7.14%), in 2010-2020 (7.45%, 95% CI: 5.29-110.40%) than in 2000-2010 (3.14%, 95% CI: 1.90-15.14%), and in the clinical bovine mastitis cases (7.49%, 95% CI: 3.71-14.54%) than in the subclinical cases (4.03%, 95% CI: 1.55-10.08%). The pooled AMR rate revealed that Klebsiella spp. were most resistant to sulfonamides (45.07%, 95% CI: 27.72-63.71%), followed by tetracyclines (36.18%, 95% CI: 23.36-51.34%), aminoglycosides (27.47%, 95% CI: 17.16-40.92%), ß-lactams (27.35%, 95% CI: 16.90-41.05%), amphenicol (26.82%, 95% CI: 14.17-44.87%), lincosamides (21.24%, 95% CI: 7.65-46.75%), macrolides (20.98%, 95% CI: 7.20-47.58%), polypeptides (15.51%, 95% CI: 6.46-32.78%), and quinolones (7.8%, 95% CI: 3.25-17.56%). The climate difference between South and North China and the natural pathogenicity of Klebsiella spp. may be the primary reasons for its distribution, and the prevalence of Klebsiella spp. indicated that the genus is an increasing hazard to the dairy industry. The prevalence of AMR in China is commonly higher than in the European countries and Canada, this is a very important concern for strategy programs to control bovine mastitis caused by Klebsiella spp. in China.

Autophagy Promotes α-Amanitin-Induced Apoptosis of Hepa1-6 Liver Cells.

It is estimated that 90% of deaths from food poisoning in China can be attributed to Amanita poisoning, whose main toxin is α-amanitin. Studies showed that apoptosis plays a critical role in liver injuries induced by α-amanitin. Although the relationship between autophagy and apoptosis in different liver models has been addressed many times, whether autophagy plays a pro or con effect on α-amanitin-induced apoptosis has not been clarified. Therefore, this study was conducted to explore the effect of autophagy in α-amanitin-induced apoptosis in Hepa1-6 liver cells. A 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was applied to determine cell viability, a 2',7'-dichlorofluorescin diacetate probe was used to monitor reactive oxygen species (ROS) levels, a flow cytometer and dansylcadaverine (MDC) staining were used to observe α-amanitin-induced apoptosis and autophagy, respectively, and apoptosis and autophagy proteins were assessed by western blotting. The results showed that α-amanitin suppressed cell viability in a time- and concentration-dependent manner. Moreover, the release of ROS was increased with increasing α-amanitin amount. Cell apoptosis and autophagy were noticed and characterized by the increased apoptosis rate and autophagic vesicles under a fluorescence microscope as well as upregulation of Bax/Bcl-2, cleaved caspase-3, and LC3-II/I and downregulation of p62. Further, the autophagy activator rapamycin (Rap) and the inhibitor 3-methylademine (3-MA) were introduced, which showed that the apoptosis rate and the ratio of Bax/Bcl-2 as well as the protein expression level of cleaved caspase-3 increased significantly with the pretreatment of Rap and decreased remarkably with the pretreatment of 3-MA. Moreover, cell viability was found to decrease further with the promotion of autophagy. Notably, the ROS level was attenuated after autophagy was elevated. In conclusion, autophagy could promote α-amanitin-induced Hepa1-6 cell apoptosis, and the process is unassociated with ROS levels. This research provides a theoretical basis for the study of the toxicological mechanism of α-amanitin-induced liver injuries.

The prevalence, molecular characterization and antimicrobial resistance profiling of Streptococcus agalactiae isolated from clinical mastitis cases on large dairy farms in China.

This research communication aims to characterize the prevalence, molecular characterization and antimicrobial resistance profiling of Streptococcus agalactiae isolated from clinical mastitis in China. A total of 140 Strep. agalactiae isolates were identified from 12 out of 201 farms in 6 provinces, overall herd prevalence was 18.6% and the MLST analysis showed clonal complexes (CC) 103 and CC 67 were present in these herds with CC 103 predominant, accounting for 97.9%. Isolates were mostly sensitive to the tested antimicrobials: penicillin, ceftiofur, amoxi/clav, cefquinome, and vancomycin (100%), followed by cefalexin (97.9%), oxacillin (96.4%), enrofloxacin (95.7%), erythromycin (89.3%), and clindamycin (88.6%). Only 19.3 and 0.7% of isolates were sensitive to tetracycline and daptomycin, respectively, and sequence type (ST) 103 was most resistant to antimicrobials. In conclusion, CC 103 was the predominant subgroup of bovine mastitis Strep. agalactiae in China, and most antimicrobials apart from tetracycline and daptomycin were effective.

Mycoplasma bovis subverts autophagy to promote intracellular replication in bovine mammary epithelial cells cultured in vitro.

Mycoplasma species are the smallest prokaryotes capable of self-replication. To investigate Mycoplasma induced autophagy in mammalian cells, Mycoplasma bovis (M. bovis) and bovine mammary epithelial cells (bMEC) were used in an in vitro infection model. Initially, intracellular M. bovis was enclosed within a membrane-like structure in bMEC, as viewed with transmission electron microscopy. In infected bMEC, increased LC3II was verified by Western blotting, RT-PCR and laser confocal microscopy, confirming autophagy at 1, 3 and 6 h post-infection (hpi), with a peak at 6 hpi. However, the M. bovis-induced autophagy flux was subsequently blocked. P62 degradation in infected bMEC was inhibited at 3, 6, 12 and 24 hpi, based on Western blotting and RT-PCR. Beclin1 expression decreased at 12 and 24 hpi. Furthermore, autophagosome maturation was subverted by M. bovis. Autophagosome acidification was inhibited by M. bovis infection, based on detection of mCherry-GFP-LC3 labeled autophagosomes; the decreases in protein levels of Lamp-2a indicate that the lysosomes were impaired by infection. In contrast, activation of autophagy (with rapamycin or HBSS) overcame the M. bovis-induced blockade in phagosome maturation by increasing delivery of M. bovis to the lysosome, with a concurrent decrease in intracellular M. bovis replication. In conclusion, although M. bovis infection induced autophagy in bMEC, the autophagy flux was subsequently impaired by inhibiting autophagosome maturation. Therefore, we conclude that M. bovis subverted autophagy to promote its intracellular replication in bMEC. These findings are the impetus for future studies to further characterize interactions between M. bovis and mammalian host cells.

Facile hydrothermal synthesis of Ti3C2Tx-TiO2 nanocomposites for gaseous volatile organic compounds detection at room temperature.

The gaseous volatile organic compounds (VOCs) sensors with high-selectivity and low-power consumption have been expected for practical applications in environmental monitoring and disease diagnosis. Herein, we demonstrate a room-temperature VOCs gas sensor with enhanced performance based on Ti3C2Tx-TiO2 nanocomposites. The Ti3C2Tx-TiO2 nanocomposites with regular morphology are successfully synthesized via a facile one-step hydrothermal synthesis strategy by using Ti3C2Tx itself as titanium source. Attributed to the formation of interfacial heterojunctions and the modulation of carrier density, the Ti3C2Tx-TiO2 sensor exhibits about 1.5-12.6 times enhanced responses for the detection of various VOCs at room temperature than pure MXene sensor. Moreover, the nanocomposite sensor has better response to hexanal, both an air pollutant and a typical lung cancer biomarker. The gas response of the Ti3C2Tx-TiO2 sensor towards 10 ppm hexanal is about 3.4%. The hexanal gas sensing results display that the nanocomposite sensor maintains a high signal-to-noise ratio and the lower detection limit to hexanal gas is as low as 217 ppb. Due to the low power consumption and easy fabrication process, the Ti3C2Tx-TiO2 nanocomposite sensor is promising for application in IoT environmental monitoring as well as real-time health monitoring.

Association of NOS2A gene polymorphisms with susceptibility to bovine tuberculosis in Chinese Holstein cattle.

Bovine tuberculosis (bTB) is a global zoonotic disease that has detrimental economic impacts worldwide. The NOS2A gene plays a key role in immunological control of many infectious diseases. However, research on the association between NOS2A polymorphisms and bTB infection in Holstein cattle reared on the Yunnan-Guizhou plateau of China is scarce. This study investigated a possible linkage between NOS2A polymorphisms and risk of developing bTB in Chinese Holstein cattle. The NOS2A gene was genotyped in 144 bTB-infected Holstein cows and 139 healthy controls were genotyped through nucleotide sequencing. Ten single-nucleotide polymorphisms (SNPs) were detected, six of which were associated with susceptibility/resistance patterns of bTB. Furthermore, the C/T genotypes of 671 and 2793, and T/T genotype of E22 (+15) were significantly associated with susceptibility risk; the G/A genotype of 2857, T/T genotype of E9 (+65), and C/C genotype of E9 (+114) probably increased resistance to bTB. In addition, the haplotypes of NOS2A-2 and NOS2A-9 were risk factors for bTB susceptibility, while the NOS2A-5 and NOS2A-8 haplotypes were contributing protective variants against tuberculosis. There is a significant association between variation in SNPs of NOS2A and tuberculosis susceptibility/resistance pattern. These findings suggest that substitution of genetic selection would be helpful for eradicating bTB. However, further investigation is required to study the underlying mechanism through which NOS2A polymorphisms affect bTB infection.

Enhanced ammonia sensing performance based on MXene-Ti3C2Tx multilayer nanoflakes functionalized by tungsten trioxide nanoparticles.

Low-power consumption and high sensitivity are highly desirable for a vast range of NH3 sensing applications. As a new type of two-dimension (2D) material, Ti3C2Tx is extensively studied for room temperature NH3 sensors recently. However, the Ti3C2Tx MXene based gas sensors suffer mainly from low sensitivity. Herein, we report a sensitive Ti3C2Tx/WO3 composite resistive sensor for NH3 detection. The Ti3C2Tx/WO3 composite consisting of WO3 nanoparticles anchored on Ti3C2Tx nanoflakes were synthesized successfully with a facile ultra-sonication technique. The composite sensor with optimized components exhibits a high sensitivity of 22.3% for 1 ppm NH3 at room temperature, which is 15.4 times higher than the pure Ti3C2Tx sensor. Furthermore, the composite sensor has excellent reproducibility, good long-term stability, and high selectivity to NH3. The relative humidity influence on NH3 gas sensing properties of the sensors was systematically studied. This research provides an efficient route for the preparation of novel MXene-based sensitive materials for high-performance NH3 sensors.

Biological Characteristics and Pathogenicity of Helcococcus ovis Isolated From Clinical Bovine Mastitis in a Chinese Dairy Herd.

Helcococcus ovis (H. ovis) was first reported in ovine subclinical mastitis milk and post-mortem examination organs in Spain and the United Kingdom in 1999; subsequently, it appeared in cattle, horse, goat, and human. However, isolation and characterization of the pathogen from clinical bovine mastitis is unknown. The objective of this study was to identify the pathogen in clinical bovine mastitis. A total of four strains were isolated from bovine mastitis milk samples from a Chinese dairy farm, and they were identified as H. ovis by microscopic examination and 16S rRNA gene sequencing. Phylogenetic tree was constructed using 16S rRNA gene, and the isolates were closely related to other China strains and strains from Japan. The growth speed of the H. ovis isolated was relatively slower than Streptococcus agalactiae, and the phenotypic characteristics were similar to H. ovis CCUG37441 and CCUG39041 except to lactose. The isolates were sensitive to most of the common used antimicrobials. The H. ovis isolates could lead to mild murine mastitis alone and induce severe mastitis when co-infected with Trueperella pyogenes in the murine mammary infection model constructed.

Characterization of Streptococcus lutetiensis isolated from clinical mastitis of dairy cows.

Streptococcus lutetiensis, previously termed Streptococcus bovis type II/1, has rarely been associated with bovine mastitis. The objectives of this work were to characterize the molecular diversity, antimicrobial resistance profiles, virulence genes of Strep. lutetiensis (n = 37) isolated from bovine clinical mastitis, as well as its pathogenic effects in a murine mastitis model. Genetic relationships of isolates were determined by random amplified polymorphic DNA (RAPD)-PCR, virulence genes were detected by PCR. Antimicrobial susceptibility testing was carried out by broth microdilution technique. The pathogenic effects of Strep. lutetiensis were studied with 2 infection models: bovine mammary epithelial cells cultured in vitro and murine mammary infection in vivo. Streptococcus lutetiensis isolates were clustered into 5 RAPD-types (A-E), with a dominant type A representing 84% of isolates. Eighteen (49%), 16 (43%), and 9 (24%) isolates were resistant to ceftiofur, tetracycline, and erythromycin, respectively. Prevalence of multidrug resistance (resistant to ≥3 classes of antimicrobials) was 24% (9/37). The most prevalent virulence genes were bca (100%), speG (100%), hly (97%), scpB (95%), and ssa (95%). There was no difference between isolates from mild and moderate cases of bovine mastitis in prevalence of virulence genes. Streptococcus lutetiensis rapidly adhered to and subsequently invaded (1 and 3 h after infection, respectively) bovine mammary epithelial cells, resulting in elevated lactate dehydrogenase release (4 h after infection). Edema and hyperemia were observed in challenged mammary glands and bacteria were consistently isolated at 12, 24, and 48 h after infection. In addition, numerous neutrophils migrated into gland alveoli and interstitium of infected mammary tissue. We concluded that Strep. lutetiensis had potential to spread within a dairy herd and good adaptive ability in bovine mammary cells or tissue, which are generally characteristics of a contagious mastitis pathogen.

Mycoplasma bovis-generated reactive oxygen species and induced apoptosis in bovine mammary epithelial cell cultures.

Mycoplasma bovis is an important cause of bovine mastitis in China and worldwide. We hypothesized that M. bovis damages bovine mammary epithelial cells (bMEC), with the degree of damage varying among field isolates. Our objective was to evaluate 2 novel sequence type (ST) field strains of M. bovis (ST172 and ST173) for their ability to induce oxidative stress, cytotoxicity, pathomorphological changes, and apoptosis in bMEC, as a model for pathogenesis of M. bovis-induced bovine mastitis. Cytotoxicity (as indicated by release of lactate dehydrogenase, LDH) from bMEC depended on multiplicity of infection (MOI), with a high MOI (1:1,000) being required to induce cytotoxicity. Morphological changes in bMEC, including shrinkage, loss of cell integrity, and heavy staining (hematoxylin and eosin) of cytoplasm were apparent 24 h after infection with ST172 or ST173 M. bovis, with more severe changes being induced by the latter strain. Adhesion and invasion assays both had curvilinear patterns, peaking 12 h after infection with MOI of 1:1,000. Both production of reactive oxygen species (ROS) and proportion of apoptotic cells increased with time after infection. Increased Bax/Bcl-2 ratios and activation of caspase-3 implied involvement of mitochondria-dependent pathways of apoptosis. Furthermore, intracellular ROS generation, apoptosis, and cleaved caspase-3 were mitigated by N-acetyl-l-cysteine, a ROS scavenger. Both interleukin (IL)-1ß and IL-6 were significantly upregulated by ST172 and ST173 M. bovis, with little change in expression of tumor necrosis factor-α. One ST173 M. bovis isolate had the greatest cytotoxicity of all of our field isolates, with the highest LDH release, adhesion, invasion, ROS production, and apoptosis. In conclusion, our hypothesis was supported: M. bovis damaged bMEC by generating ROS and initiating a mitochondria-dependent pathway of apoptosis, with the degree of damage varying among field isolates. This study provided new knowledge regarding pathogenesis of M. bovis-induced bovine mastitis.

Antimicrobial resistance profiles of 5 common bovine mastitis pathogens in large Chinese dairy herds.

The prevalence of antimicrobial resistance (AMR) is increasing in human and animal pathogens, becoming a concern worldwide. However, prevalence and characteristics of AMR of bovine mastitis pathogens in large Chinese dairy herds are still unclear. Therefore, our objective was to determine the AMR profile of bacteria isolated from clinical mastitis in large (>500 cows) Chinese dairy herds. A total of 541 isolates of the 5 most common species, Staphylococcus aureus (n = 103), non-aureus staphylococci (NAS; n = 107), Streptococcus species (n = 101), Klebsiella species (n = 130), and Escherichia coli (n = 100), isolated from bovine clinical mastitis on 45 dairy farms located in 10 provinces of China were included. Presence of AMR was determined by minimum inhibitory concentrations using the microdilution method. Prevalence of multidrug resistance (resistance to >2 antimicrobials) was 27% (148/541). A very wide distribution of minimum inhibitory concentrations was screened in all isolates, including Staph. aureus isolates, which were resistant to penicillin (66%). In addition, NAS (30%) were more resistant than Staph. aureus to oxacillin (84%), penicillin (62%), tetracycline (34%), and clindamycin (33%). Prevalence of resistance to tetracycline was high (59%) in Streptococcus spp. Additionally, prevalence of resistance of both E. coli and Klebsiella spp. was high to amoxicillin/clavulanate potassium (81 and 38%, respectively), followed by tetracycline (only Klebsiella spp. 32%). A high proportion (27%) of isolates were multidrug resistant; the most frequent combinations were clindamycin-cefalexin-tetracycline or enrofloxacin-cefalexin-penicillin patterns for Staph. aureus; enrofloxacin-oxacillin-penicillin-tetracycline patterns for NAS; clindamycin-enrofloxacin-tetracycline patterns for Streptococcus spp.; amoxicillin/clavulanate potassium-ceftiofur-polymyxin B patterns for Klebsiella spp.; and amoxicillin/clavulanate potassium-ceftiofur-polymyxin B patterns for E. coli. Resistance for 4 kinds of antimicrobials highly critical for human medicine, including daptomycin, vancomycin, imipenem, and polymyxin B, ranged from 0 to 24%. In conclusion, prevalence of AMR in mastitis pathogens was high on large Chinese dairy farms, potentially jeopardizing both antimicrobial efficacy and public health. Results of this study highlighted the need for improvements in antimicrobial stewardship and infection control programs in large Chinese dairy farms to reduce emergence of AMR.

The Characteristics of Staphylococcus aureus Small Colony Variant Isolated from Chronic Mastitis at a Dairy Farm in Yunnan Province, China.

Staphylococcus aureus is a major causative agent leading to bovine mastitis and has specific phonotypical characteristics including small colony, slow growth, and decreased hemolysis, therefore named as the small colony variants (SCVs). Out of 30 tested samples of the chronic S. aureus cases, one strain of SCVs (S. aureus SCV22) was isolated along with its parental strains (S. aureus11). S. aureus SCV22 showed a slow growth rate when it is compared with the parental strain. However, their resistant patterns were similar. Meanwhile, S. aureus SCV22 depicted the lower rate of apoptosis in bovine mammary epithelial cells. These findings of the present study presented the unique characteristics of S. aureus SCV22 for the first time in Yunnan province, which provided a prophase foundation for further study about the pathogenesis of S. aureus SCVs in chronic mastitis.

Sodium fluoride modulates caprine osteoblast proliferation and differentiation.

The cellular and molecular pathways of fluoride toxicity in osteoblasts are not very well understood. Therefore, the objective of the present study was to evaluate the effects of sodium fluoride (NaF) on caprine osteoblasts cultured in vitro. Caprine osteoblasts at 2.0 x 10(-4) cells/ml were incubated in vitro with NaF at 0, 10(-8), 10(-7), 10(-6), 10(-5), 10(-4), 5.0 x 10(-4), and 10(-3) M, and then proliferation, differentiation, apoptosis, calcification, and alkaline phosphatase activity were examined. Also, the effect of NaF on osteoblastic cell viability and the molecular events leading to apoptosis were determined. Electron microscopy revealed cytoplasmic and nuclear alterations in the ultrastructure of osteoblasts exposed to various NaF concentrations. A cell-based quantitative evaluation of the MTT assay showed that NaF at concentrations of 10(-8) to 10(-5) M promoted cell proliferation, whereas at 10(-4) to 10(-3) M it suppressed cell proliferation and induced apoptosis. Alkaline phosphatase (ALP) activity and mineralization ability increased in cells treated at 10(-8) to 10(-5) M with sodium versus the controls, but decreased at 5.0 x 10(-4) to 10(-3) M dosage. The highest incidence of early apoptotic cells and late apoptotic cells was reached (3.33% and 2.92%, respectively) under NaF concentration of 10(-4) M. In conclusion, results of this study indicated that NaF modulates osteoblast proliferation and differentiation in a dose-dependent manner and modified osteoblast metabolism bidirectionally, suggesting NaF may play a significant role in osteoblast physiology.