Mastitis In China Research Articles

Occurrence of antimicrobial resistance and class 1 integrons in Staphylococcus aureus isolated from bovine mastitis in China.

Integrons are important genetic elements that allow easy acquisition and dissemination of antimicrobial resistance genes. Studies reporting occurrence of integrons in Staphylococcus aureus (S. aureus) isolated from bovine mastitis in large dairy farms across China are scarce. The aim of this study was to investigate the occurrence of class 1 integrons (intI1), antimicrobial resistance (AMR) and associated genes in S. aureus isolated from bovine mastitis and their associations. Minimum inhibitory concentrations (MICs) were determined to evaluate the AMR phenotypes, whereas PCR was carried out to assess the occurrence of AMR genes and intI1. In addition, index cluster analysis was used to estimate associations between AMR phenotype, genotype and intI1 in 103 isolates. Overall, 83% of S. aureus were intI1-positive and 5 types of gene cassettes were detected. Susceptibility against single antimicrobial agents ranged from 0% (erythromycin), 12% (ampicillin) and 16% (penicillin G) to 96% (gentamicin). Most isolates (64%) were intermediate-resistant against erythromycin, whereas resistance against ceftriaxone (22%), clindamycin (4%), cefotaxime (2%), tetracycline (1%) and ciprofloxacin (1%) were relatively uncommon. The predominant resistant gene was blaZ gene (n = 88, 85%) followed by tetD gene (n = 85, 83%). With an estimated prevalence of 12% of the mecA gene, methicillin-resistant S. aureus isolates had higher MIC50 and MIC90 for majority of antimicrobials than methicillin-susceptible S. aureus isolates. Presence of the ermC gene was associated with erythromycin resistance. Ampicillin, erythromycin and penicillin G resistance were associated with intI1. The data presented in our study indicated that class 1 integron-mediated resistance possibly plays an important role in dissemination of AMR in S. aureus isolated from bovine mastitis.

Four novel Acinetobacter lwoffii strains isolated from the milk of cows in China with subclinical mastitis

BackgroundAcinetobacter lwoffii (A. lwoffii) is a Gram-negative bacteria common in the environment, and it is the normal flora in human respiratory and digestive tracts. The bacteria is a zoonotic and opportunistic pathogen that causes various infections, including nosocomial infections. The aim of this study was to identify A. lwoffii strains isolated from bovine milk with subclinical mastitis in China and get a better understanding of its antimicrobial susceptibility and resistance profile. This is the first study to analyze the drug resistance spectrum and corresponding mechanisms of A. lwoffii isolated in raw milk.ResultsFour A. lwoffii strains were isolated by PCR method. Genetic evolution analysis using the neighbor-joining method showed that the four strains had a high homology with Acinetobacter lwoffii. The strains were resistant to several antibiotics and carried 17 drug-resistance genes across them. Specifically, among 23 antibiotics, the strains were completely susceptible to 6 antibiotics, including doxycycline, erythromycin, polymyxin, clindamycin, imipenem, and meropenem. In addition, the strains showed variable resistance patterns. A total of 17 resistance genes, including plasmid-mediated resistance genes, were detected across the four strains. These genes mediated resistance to 5 classes of antimicrobials, including beta-lactam, aminoglycosides, fluoroquinolones, tetracycline, sulfonamides, and chloramphenicol.ConclusionThese findings indicated that multi-drug resistant Acinetobacter lwoffii strains exist in raw milk of bovine with subclinical mastitis. Acinetobacter lwoffii are widespread in natural environmental samples, including water, soil, bathtub, soap box, skin, pharynx, conjunctiva, saliva, gastrointestinal tract, and vaginal secretions. The strains carry resistance genes in mobile genetic elements to enhance the spread of these genes. Therefore, more attention should be paid to epidemiological surveillance and drug resistant A. lwoffii.

Prevalence and molecular characterization of multi-resistant Escherichia coli isolates from clinical bovine mastitis in China

Different antibiotics are used to treat mastitis in dairy cows that is caused by Escherichia coli (E. coli). Antimicrobial resistance in food-producing animals in China has been monitored since 2000. Surveillance data have shown that the prevalence of multiresistant E. coli in animals has increased significantly. This study aimed to investigate the occurrence and molecular characteristics of resistance determinants in E. coli strains (n = 105) obtained from lactating cows with clinical bovine mastitis (CBM) in China. A total of 220 cows with clinical mastitis, which has swollen mammary udder with reduced and red or gangrenous milk, were selected from 5000 cows. The results showed 94.3% of the isolates were recognized as multidrug resistant. The isolates (30.5%) were positive for the class I integrase gene along with seven gene cassettes that were accountable for resistance to trimethoprim resistance (dfrA17, dfr2d and dfrA1), aminoglycosides resistance (aadA1 and aadA5) and chloramphenicol resistance (catB3 and catB2), respectively. The bla TEM gene was present in all the isolates, and these carried the bla CTX gene. A double mutation in gyrA (i.e., Ser83Leu and Asp87Asn) was observed in all fluoroquinolone-resistant isolates. In total, nine fluoroquinolone-resistant E. coli isolates were identified with five different types of mutations in parC. In four (44.4%) isolates, Ser458Ala was present in parE, and in all nine (9/9) fluoroquinolone-resistant isolates, Pro385Ala was present in gyrB. Meanwhile, fluoroquinolone was observed as highly resistant, especially in isolates with gyrA and parC mutations. In summary, the findings of this research recognize the fluoroquinolone resistance mechanism and disclose integron prevalence and ESBLs in E. coli isolates from lactating cattle with CBM.

Comparative genomic analyses of Klebsiella pneumoniae K57 capsule serotypes isolated from bovine mastitis in China

Klebsiella pneumoniae can cause severe clinical mastitis in dairy cows, with K. pneumoniae type K57 (K57-KP) being the most common capsular serotype. To identify virulence factors and antimicrobial-resistance (AMR) genes of K57-KP with varying virulence, Galleria mellonella (greater wax moth) larvae were infected as a screening model to characterize virulence of 90 K57-KP strains, with 10 and 11 strains defined as virulent or attenuated, respectively, based on larval survival rates. Next, virulence of these 21 isolates was subsequently confirmed in adhesion and lactate dehydrogenase release assays, using bovine mammary epithelial cells cultured in vitro. Finally, genes associated with virulence and AMR were characterize with whole-genome sequencing. These 21 K57-KP strains were designated into 16 sequence types based on multi-locus sequence typing and allocated in phylogenetic analysis based on single nucleotide polymorphisms. We found great genetic diversity among isolates. In addition, adhesion-associated genes (e.g., fimA, sfaA, and focA) aminoglycoside-resistance genes (aph(6)-Id, strAB) were associated with virulence. This study provided new knowledge regarding virulence of K57-KP associated with bovine mastitis, which may inform development of novel diagnostic tools and prevention strategies for bovine mastitis.

Antimicrobial resistance and virulence profiles of staphylococci isolated from clinical bovine mastitis.

Staphylococci, mainly including Staphylococcus aureus and coagulase-negative staphylococci (CNS), are one of the most common pathogens causing bovine mastitis worldwide. In this study, we investigated the antimicrobial resistance and virulence profiles of staphylococci from clinical bovine mastitis in Ningxia Hui Autonomous Region of China. Antimicrobial resistance was determined by disc diffusion combined with E-test method. Genes of antimicrobial resistance and virulence factors were determined by PCR. A total of 332 staphylococcal isolates were confirmed from 1,519 mastitic milk samples, including 172 S. aureus and 160 CNS isolates. Fifteen CNS species were identified, with S. chromogenes being the most frequent found (49.4%), followed by S. equorum (13.8%). Noticeably, 2 S. agnetis isolates were found among the CNS isolates. To our knowledge, this is the first report documenting the presence of S. agnetis from bovine mastitis in China. The S. aureus and CNS isolates showed high resistance against penicillin, followed by erythromycin and tetracycline. Multidrug resistance was found in 11.6 and 16.3% of the S. aureus and CNS isolates, respectively. Resistance to penicillin was attributed to the presence of blaZ, erythromycin resistance to ermC (alone or combined with ermB) and tetracycline resistance to tetK (alone or combined with tetM). Notably, one S. equorum isolate and one S. saprophyticus isolate were both methicillin-resistant and mecA positive. Additionally, all S. aureus isolates carried the adhesin genes fnbpA, clfA, clfB, and sdrC, and most of them contained cna and sdrE. Conversely, only a few of the CNS isolates carried clfA, cna, and fnbA. Regarding toxin genes, all S. aureus isolates harbored hlb, and most of them were hlg positive. The lukE-lukD, lukM, sec, sed, sei, sen, seo, tst, seg, seh, and sej were also detected with low frequencies. However, no toxin genes were observed in CNS isolates. This study reveals high species diversity of staphylococci from clinical bovine mastitis in Ningxia Hui Autonomous Region of China. The findings for the genetic determinants of antimicrobial resistance and virulence factor provide valuable information for control and prevention of staphylococcal bovine mastitis.

Comparative Genomic Analyses of Lactococcus garvieae Isolated from Bovine Mastitis in China.

Lactococcus garvieae is an emerging zoonotic pathogen, but there are few reports regarding bovine mastitis. The prevalence of L. garvieae represents an increasing disease threat and global public health risk. Thirty-nine L. garvieae isolates were obtained from 2,899 bovine clinical mastitis milk samples in 6 provinces of China from 2017 to 2021. Five clonal complexes were determined from 32 multilocus sequence types (MLSTs) of L. garvieae: sequence type 46 (ST46) was the predominant sequence type, and 13 novel MLSTs were identified. All isolates were resistant to chloramphenicol and clindamycin, but susceptible to penicillin, ampicillin, amoxicillin-clavulanic acid, imipenem, ceftiofur, enrofloxacin, and marbofloxacin. Based on genomic analyses, L. garvieae had 6,310 genes, including 1,015 core, 3,641 accessory, and 1,654 unique genes. All isolates had virulence genes coding for collagenase, fibronectin-binding protein, glyceraldehyde-3-phosphate dehydrogenase, superoxide dismutase, and NADH oxidase. Most isolates had lsaD and mdtA antimicrobial resistance (AMR) genes. Based on COG (Clusters of Orthologous Genes database) results, the functions of defense, transcription and replication, and recombination and repair were enhanced in unique genes, whereas functions of translation, ribosomal structure, and biogenesis were enhanced in core genes. The KEGG functional categories enriched in unique genes included human disease and membrane transport, whereas COG functional categories enriched in core genes included energy metabolism, nucleotide metabolism, and translation. No gene was significantly associated with host specificity. In addition, analysis of core genome single nucleotide polymorphisms (SNPs) implied potential host adaptation of some isolates in several sequence types. In conclusion, this study characterized L. garvieae isolated from mastitis and detected potential adaptations of L. garvieae to various hosts. IMPORTANCE This study provides important genomic insights into a bovine mastitis pathogen, Lactococcus garvieae. Comprehensive genomic analyses of L. garvieae from dairy farms have not been reported. This study is a detailed and comprehensive report of novel features of isolates of L. garvieae, an important but poorly characterized bacterium, recovered in the past 5 years in 6 Chinese provinces. We documented diverse genetic features, including predominant sequence type ST46 and 13 novel MLSTs. Lactococcus garvieae had 6,310 genes, including 1,015 core, 3,641 accessory, and 1,654 unique genes. All isolates had virulence genes coding for collagenase, fibronectin-binding protein, glyceraldehyde-3-phosphate dehydrogenase, superoxide dismutase, and NADH oxidase and resistance to chloramphenicol and clindamycin. Most isolates had lsaD and mdtA antimicrobial resistance genes. However, no gene was significantly associated with host specificity. This is the first report that characterized L. garvieae isolates from bovine mastitis and revealed potential host adaptations of L. garvieae to various hosts.

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 β-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 β-lactams amongst the eight groups of antimicrobial agents.

Prevalence, Virulence, and Antibiotics Gene Profiles in Lactococcus garvieae Isolated from Cows with Clinical Mastitis in China.

Lactococcus garvieae (L. garvieae) is a pathogenic gram-positive, catalase-negative (GPCN) bacterium that causes bovine mastitis. A total of 49 L. garvieae isolates were identified from 1441 clinical mastitis (CM) samples. The pathogenic effects of L. garvieae were studied with two infection models: bovine mammary epithelial cells cultured in vitro and murine mammary infections in vivo. The overall farm prevalence was 15.5% (13/84 farms in 9/19 provinces) and sample prevalence was 3.40% (49/1441). Post-treatment somatic cell count (SCC) post L. garvieae infection was significantly higher than the other GPCN pathogens isolated, and the bacteriological cure fraction was 41.94% (13/31) after intramammary antibiotic treatment. All L. garvieae isolates were resistant to rifaximin, 12.24% of isolates were resistant to cephalexin, and 10.20% (5/49) were multidrug-resistant (MDR). The most prevalent virulence genes were Hemolysin 1 (hly1)(100%), Hemolysin 2 (hly2) (97.96%), NADH oxidase (NADHO) (100%), Superoxide dismutase (SOD) (100%), Adhesin Pav (Pav) (100%), Adhesin PsaA (PsaA) (100%), Enolase (eno) (100%), Adhesin cluster 1(AC1) (100%), Adhesin cluster 2 (AC2) (100%), and several exopolysaccharides. L. garvieae rapidly adhered to bovine mammary epithelial cells, resulting in an elevated lactate dehydrogenase release. Edema and congestion were observed in challenged murine mammary glands and bacteria were consistently isolated at 12, 24, 48, 72, and 120 h after infection. We concluded that L. garvieae had good adaptive ability in the bovine and murine mammary cells and tissue. Given the resistance profile, penicillin and ampicillin are potential treatments for CM cases caused by L. garvieae.

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.

Comparative Genomic Analysis of Streptococcus dysgalactiae subspecies dysgalactiae Isolated From Bovine Mastitis in China.

Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) is one of the most prevalent pathogens causing bovine mastitis worldwide. However, there is a lack of comprehensive information regarding genetic diversity, complete profiles of virulence factors (VFs), and antimicrobial resistance (AMR) genes for SDSD associated with bovine mastitis in China. In this study, a total of 674 milk samples, including samples from 509 clinical and 165 subclinical mastitis cases, were collected from 17 herds in 7 provinces in China from November 2016 to June 2019. All SDSD isolates were included in phylogenetic analysis based on 16S rRNA and multi-locus sequence typing (MLST). In addition, whole genome sequencing was performed on 12 representative SDSD isolates to screen for VFs and AMR genes and to define pan-, core and accessory genomes. The prevalence of SDSD from mastitis milk samples was 7.57% (51/674). According to phylogenetic analysis based on 16S rRNA, 51 SDSD isolates were divided into 4 clusters, whereas based on MLST, 51 SDSD isolates were identified as 11 sequence types, including 6 registered STs and 5 novel STs (ST521, ST523, ST526, ST527, ST529) that belonged to 2 distinct clonal complexes (CCs) and 4 singletons. Based on WGS information, 108 VFs genes in 12 isolates were determined in 11 categories. In addition, 23 AMR genes were identified in 11 categories. Pan-, core and accessory genomes were composed of 2,663, 1,633 and 699 genes, respectively. These results provided a comprehensive profiles of SDSD virulence and resistance genes as well as phylogenetic relationships among mastitis associated SDSD in North China.

Multidrug resistance analysis method for pathogens of cow mastitis based on weighted-association rule mining and similarity comparison

Mastitis is one of the most common diseases and causes the greatest economic loss in dairy farming. Antibiotics are the most effective drugs to prevent and treat bacterial infection of mastitis. However, yet the growing problem of drug resistance, especially multidrug resistance (MDR), poses a great threat to disease control. To understand the MDR rules in bacteria of cow mastitis from national level, the main bacteria from cows with mastitis in large-scale farms were isolated and identified in China, and then drug sensitivity tests were conducted to establish a drug resistance data set. Aiming at the problem of numerous and disordered drug resistance data and lack of extensive correlations, a weighted Apriori association rule mining algorithm in conjunction with the bacterial drug resistance prevalence is proposed. We analyzed the associations between different antibiotics of key bacteria, extracted and visualized the key trends of high resistance prevalence and frequent occurrence, and discovered MDR patterns. Finally, a similarity comparison method based on Euclidean measurement was proposed to compare the relative MDR rules of different bacteria from the overall level with support, confidence, and promotion as characteristic parameters. The drug resistance data set showed that staphylococcus were the main bacteria isolated from dairy cow mastitis in China. Then based on the association rule algorithm, the important rules between different antibiotics resistance in this dataset were identified. In addition, the MDR patterns of different bacteria were visualized and analyzed by using the chord diagram. The results showed the bacteria are highly resistant to penicillin, gentamicin, and ampicillin, and most other antibiotics were linked with these three antibiotics. Finally, the high correlations and main rules in different bacteria were confirmed by a similarity comparison method. The assessment model and conclusions of this study are potentially valuable for assessing the evolution of MDR patterns, providing a scientific basis for relevant authorities to guide the rational use of antibiotics in the farming industry.

Risk factors for lactation mastitis in China: A systematic review and meta-analysis.

Lactation mastitis (LM) affects approximately 3% to 33% of postpartum women and the risk factors of LM have been extensively studied. However, some results in the literature reports are still not conclusive due to the complexity of LM etiology and variation in the populations. To provide nationally representative evidence of the well-accepted risk factors for LM in China, this study was aimed to systematically summary the risk factors for LM among Chinese women and to determine the effect size of individual risk factor. Six major Chinses and English electronic literature databases (PubMed, Web of Science, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, Wan fang Database and China Science Technology Journal Database) were searched from their inception to December 5st, 2020. Two authors extracted data and assessed the quality of included trials, independently. The strength of the association was summarized using the odds ratio (OR) with 95% confidence intervals (CI). The population attributable risk (PAR) percent was calculated for significant risk factors. Fourteen studies involving 8032 participants were included. A total of 18 potential risk factors were eventually evaluated. Significant risk factors for LM included improper milking method (OR 6.79, 95%CI 3.45-13.34; PAR 59.14%), repeated milk stasis (OR 6.23, 95%CI 4.17-9.30; PAR 49.75%), the first six months postpartum (OR 5.11, 95%CI 2.66-9.82; PAR 65.93%), postpartum rest time less than 3 months (OR 4.71, 95%CI 3.92-5.65; PAR 56.95%), abnormal nipple or crater nipple (OR 3.94, 95%CI 2.34-6.63; PAR 42.05%), breast trauma (OR 3.07, 95%CI 2.17-4.33; PAR 15.98%), improper breastfeeding posture (OR 2.47, 95%CI 2.09-2.92; PAR 26.52%), postpartum prone sleeping position (OR 2.46, 95%CI 1.58-3.84; PAR 17.42%), little or no nipple cleaning (OR 2.05, 95%CI 1.58-2.65; PAR 24.73%), primipara (OR 1.73, 95%CI 1.25-2.41; PAR 32.62%), low education level (OR 1.63, 95%CI 1.09-2.43; PAR 23.29%), cesarean section (OR 1.51, 95%CI 1.26-1.81; PAR 18.61%), breast massage experience of non-medical staff (OR 1.51, 95%CI 1.25-1.82; PAR 15.31%) and postpartum mood disorders (OR 1.47, 95%CI 1.06-2.02; PAR 21.27%). This review specified several important risk factors for LM in China. In particular, the incidence of LM can be reduced by controlling some of the modifiable risk factors such as improper breastfeeding posture, improper milking method, repeated milk stasis, nipple cleaning, breast massage experience of non-medical staff and postpartum sleeping posture.

Molecular epidemiology, antimicrobial activity, and virulence gene clustering of Streptococcus agalactiae isolated from dairy cattle with mastitis in China

Streptococcus agalactiae is a contagious pathogen that causes bovine mastitis worldwide, resulting in considerable economic losses. In this study, we isolated 42 S. agalactiae strains in 379 milk samples from cows with subclinical mastitis on 15 dairy farms in 12 Chinese provinces. Analysis based on capsular typing and multilocus sequence typing, combined with patterns of virulence gene scanning and antimicrobial resistance, identified the lineages and populations of the isolates. We grouped the 42 isolates into 7 sequence types belonging to 6 clonal complexes, mainly CC103 (31/42 isolates; 73.8%). We identified an ST-23 strain named Sa 129 for the first time on Chinese dairy farms-this strain is usually associated with human isolates. Capsular types Ia and II were predominant in capsular typing. The prevalence of virulence profile 1 (bibA, cfb, cspA, cylE, fbsA, fbsB, hylB, and pavA) was 64.3%, and represented the main trend in China. With respect to antimicrobial resistance, most isolates were susceptible to β-lactams, rifamycin, glycopeptides, and oxazolidone; resistance to several antimicrobial agents, including lincomycin, clindamycin, and doxycycline, varied in 4 different regions. Our research provides a profile for the molecular epidemiology, multilocus sequence typing, antimicrobial resistance, and virulence gene clustering of S. agalactiae, and may be beneficial for the clinical monitoring, prevention, and control of mastitis in dairy cattle.

Clinical efficacy of intravaginal recombinant lysostaphin administration on endometritis in sows.

Recombinant lysostaphin has been used for the treatment of cow endometritis and mastitis in China. To our knowledge, no scientific effort has been made to evaluate the efficacy of lysostaphin in sows with clinical endometritis. Lysostaphin, loaded in effervescent tablets that were completely foamed and dissolved within 30 min in the presence of water or body fluids and released active lysostaphin, were administered vaginally on endometritis sows in this study. The clinical recovery, bacterial clearance and reproductive performance of sows with endometritis were investigated. We found that the 400U dosage (400U lysostaphin/pill/time, repeat once on the third day, a total of two times, with 10% oxytetracycline uterine injection as a control) is the most effective treatment. Staphylococcus aureus was the most prevalent finding (34%, n = 188), followed by Streptococcus (32%, n = 181), Escherichia coli (19%, n = 104) and other bacilli (15%, n = 83) before treatment by drugs. Administration of lysostaphin resulted in an extremely significant (p < .01) reduction in S. aureus (0.18 ± 0.25 from 4.57 ± 0.33) and Streptococcus (0.11 ± 0.14 from 3.88 ± 0.29), as well as a significant (p < .05) reduction in E. coli (0.55 ± 0.42 from 3.11 ± 0.14). Mixed infections (83%) were predominant before treatment, in contrast to single infections (61%) after treatment. Large‐scale trials were conducted to verify the clinical efficacy of lysostaphin on sow endometritis. The average cure rate of 400u lysostaphin on sow endometritis(82.5%) was higher than the antibiotic group(72.17%). In addition, our results revealed that intravaginal administration of lysostaphin had no adverse effect on the reproductive performance of sows. Thus, this lysostaphin has potential application value as a new method alternative to antibiotics to treat endometritis in sows.

Genetic Polymorphisms of Staphylococcus aureus Isolated from Bovine Mastitis in China

Genetic Polymorphisms of Staphylococcus aureus Isolated from Bovine Mastitis in China

Detection of antimicrobial resistance and virulence-related genes in Streptococcus uberis and Streptococcus parauberis isolated from clinical bovine mastitis cases in northwestern China

The objectives of this study were to investigate antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from cows with bovine clinical mastitis in China and to examine the distribution of resistance- and virulence-related gene patterns. Antimicrobial susceptibility was determined by the E-test. Genes encoding antimicrobial resistance and invasiveness factors were examined by PCR. A total of 27 strains were obtained from 326 mastitis milk samples. Streptococcus parauberis isolates (n=11) showed high resistance to erythromycin (90.9%), followed by tetracycline (45.5%), chloramphenicol (36.4%) and clindamycin (27.3%). Streptococcus uberis isolates (n=16) were highly resistant to tetracycline (81.3%) and clindamycin (62.5%). Both species were susceptible to ampicillin. The most prevalent resistance gene in S. uberis was tetM (80.0%), followed by blaZ (62.5%) and ermB (62.5%). However, tetM, blaZ, and ermB genes were only found in 27.3, 45.5, and 27.3%, respectively, of S. parauberis. In addition, all of the isolates carried at least one selected virulence-related gene. The most prevalent virulence-associated gene pattern in the current study was sua+pauA/skc+gapC+hasC detected in 22.2% of the strains. One S. uberis strain carried 7 virulence-associated genes and belonged to the sua+pauA/skc+gapC+cfu+hasA+hasB+hasC pattern. More than 59.3% of analysed strains carried 4 to 7 virulence-related genes. Our findings demonstrated that S. parauberis and S. uberis isolated from clinical bovine mastitis cases in China exhibited diverse molecular ecology, and that the strains were highly resistant to antibiotics commonly used in the dairy cow industry. The data obtained in the current study contribute to a better understanding of the pathogenesis of bacteria in mastitis caused by these pathogens, and the findings are relevant to the development of multivalent vaccines and targeted prevention procedures.

In vitro immune responses of bovine mammary epithelial cells induced by Escherichia coli, with multidrug resistant extended-spectrum β-lactamase, isolated from mastitic milk

Bovine mastitis is an inflammatory condition of mammary glands causing huge economic losses for dairy industries. Infection with extended-spectrum β-lactamase (ESBL)-producing sequence types (ST) 410-Escherichia coli (ESBL-ST410 E. coli) is considered a leading cause of bovine mastitis in China. However, pathogenic effects of these strains in an in vitro model, e.g. bovine mammary epithelial cells (bMECs), are unknown. Therefore, our objectives were to explore pathogenesis (adhesion and invasion, inflammation, oxidative stress and apoptosis) of ESBL-E. coli (highly prevalent in bovine mastitis) in bMECs. Non-pathogenic E. coli DH5α and a prototypical E. coli P4 were included as negative and positive controls, respectively. The bMECs were infected with our isolated ST410 strains, plus DH5α and P4, with assessment of the following end points: adhesive and invasive capabilities; lactate dehydrogenase (LDH) activities; inflammatory responses, including concentrations of interleukin-1β (IL-1β), IL-6, IL-10 and tumor necrosis factor-α; oxidative stress including intracellular reactive oxygen species production, malondialdehyde concentrations, activities of glutathione peroxidase and superoxide dismutase; and apoptosis. All ST410 strains had greater adhesive and invasive capabilities and increased LDH release, with varying degrees of inflammatory responses, oxidative stress and apoptosis compared to blank and DH5α groups, similar to P4-infected bMECs. In particular, ST410(4) was more likely than the other 3 isolates to adhere to and invade bMECs and increase LDH activities, cytokine release, oxidative stress and apoptosis. Thus, ST410 isolates had pathogenic manifestations of adhesive and invasive capabilities; furthermore, they induced inflammation, oxidative stress and apoptosis in bMECs. Finally, ST410(4) was the most pathogenic strain.

Studies of nursing in acute mastitis in China: Bibliometric analysis

Objective: To analyze the research hotspots of nursing related to lactation acute mastitis in China and provide guidance and reference for nursing researchers. Methods: Papers from China National Knowledge Infrastructure, Wanfang Data, VIP Data, and SinoMed are collected. All papers were imported into Noteexpress software in the form of bibliography to check again and delete duplicate references. The remaining literature was screened by reading the title and abstract and finally included by reading the full text. The paper's information was analyzed using SPSS 22.0. Results: 1275 papers are searched and 531 papers are included at last. Periodical literature accounted for the highest proportion, 96.80%. Moreover, the journal with the largest number of entries is China Health Care and Nutrition. In 2007, the number of literatures related to acute mastitis nursing began to increase rapidly, and the most articles were published in Henan. Among the literature types, the majority are literatures expert experience. Only 18 literature reports were funded. Conclusions: Papers on acute mastitis nursing are increasing year by year and gradually become a research hotspot. However, the development of this study is uneven in different regions, with little financial support, and randomized controlled trials are still to be carried out.

Short communication: Detection and molecular characterization of methicillin-resistant Staphylococcus aureus isolated from subclinical bovine mastitis cases in China

This study investigated the antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) isolated from cases of subclinical bovine mastitis in China, as well as resistance mechanisms and virulence genes encoding adhesins and toxins. We determined antimicrobial susceptibility using the disk diffusion method, and analyzed resistance, adhesin, and toxin genes using PCR. We confirmed MRSA in 73 of 498 (14.7%) Staph. aureus isolates recovered from subclinical mastitic milk samples. All isolates were positive for mecA. The MRSA isolates showed high resistance to penicillin (100.0%), gentamicin (100.0%), and tetracycline (98.6%). All MRSA isolates harbored resistance genes blaZ (penicillin), aacA/aphD (gentamicin), and tetM (alone or in combination with tetK, tetracycline). Moreover, all isolates carried the adhesin genes fnbpA, clfA, clfB, cna, sdrE, and map/eap, and most carried sdrC (98.6%), sdrD (95.9%), bbp (94.5%), and ebpS (80.8%). The toxin genes seh, hla, and hld were present in all isolates, and most isolates carried sea (71.2%), seg (84.9%), sei (82.2%), lukE-lukD (97.3%), and hlg (72.6%). These findings of high-level resistance to antimicrobials commonly used in dairy cattle should lead to calls for antibiogram analysis before antimicrobial therapy. The high frequency of adhesin and toxin genes in MRSA indicates their potential virulence in bovine mastitis in China.

The status of Mycoplasma bovis infection in clinical mastitis cases in China

In this study, ELISA and PCR were used to examine paired serum and milk samples (n = 850) from China and milk samples (n = 860) from the Inner Mongolia Autonomous Region from 2008 to 2015. The annual proportion of Mycoplasma bovis‐positive mastitis samples in China and Inner Mongolia Autonomous Region fluctuated inexplicably, with total average positivity value of 53.0% and 34.2%, respectively. We propose that the monthly variation in the proportion of M. bovis‐positive mastitis milk in Inner Mongolia Autonomous Region is related to the pathogen's survival in the environment, which requires further confirmation. The results highlight the severity of M. bovis infection in clinical mastitis in China.