Context: Mastitis is the most expensive disease in the dairy cattle industry and results in decreased reproductive performance. Streptococcus, especially Streptococcus agalactiae, possesses a variety of virulence factors that contribute to pathogenicity. Objective: Streptococcus isolated from mastitis was tested to assess the prevalence of antimicrobial resistance and distribution of antibiotic resistance-and virulence-related genes. Materials and methods: Eighty-one Streptococcus isolates were phenotypically characterized for antimicrobial resistance against 15 antibiotics by determining minimum inhibitory concentrations (MIC) using a micro-dilution method. Resistance-and virulence-related genes were detected by PCR. Results: High percentage of resistance to b-lactams, along with tetracycline and erythromycin, was found. Resistance to three or more of seven antimicrobial agents was observed at 88.9%, with penicillin-tetracycline-erythromycin-clindamycin as the major profile in Streptococcus isolates. Resistant genes were detected by PCR, the result showed that 86.4, 86.4, 81.5, and 38.3% of isolates were mainly carrying the pbp2b, tetL, tetM, and ermB genes, respectively. Nine virulence genes were investigated. Genes cyl, glnA, cfb, hylB, and scaA were found to be in 50% of isolates, while 3.7, 21, and 4.9% of isolates were positive for bca, lmb, and scpB, genes, respectively. None of the isolates carried the bac gene. Discussion and conclusion: This study suggests the need for prudent use of antimicrobial agents in veterinary clinical medicine to avoid the increase and dissemination of antimicrobial resistance arising from the use of antimicrobial drugs in animals.

Clinical endometritis is an important disease of dairy cattle and results in decreased reproductive performance. This disease is caused by contamination of the uterus with a broad spectrum of microorganisms after calving. In this study, staphylococcal isolates from the uterus of dairy cows with clinical endometritis were tested for their distribution of superantigen (SAg) genes and antimicrobial resistance. Between the 127 staphylococcal isolates collected in this study, 10 species were identified. The predominant strain identified was Staphylococcus aureus (n=53), followed by Staphylococcus saprophyticus (n=38) and Staphylococcus chromogenes (n=22). PCR analysis demonstrated that most isolates (63.0 per cent) harboured at least one SAg gene. The most commonly observed SAg gene and genotype was selj (38.6 per cent) and sec-selj-seln (24.0 per cent), respectively. Most isolates were resistant to penicillin (79.5 per cent), ampicillin (71.7 per cent), erythromycin (56.7 per cent), and tetracycline (52.0 per cent). PCR analysis demonstrated that the antimicrobial resistance determinants ermA, ermB, ermC, tetK, tetM and blaZ were detected in 0 per cent, 44.4 per cent, 51.4 per cent, 68.2 per cent, 13.6 per cent and 86.1 per cent of the erythromycin, tetracycline and β-lactam resistant isolates, respectively. There were 22 (17.3 per cent of all isolates) coagulase-negative staphylococci shown to be methicillin resistant. In the methicillin-resistant isolates, significant resistances to ampicillin, erythromycin and penicillin were observed (P<0.01). The results of this study demonstrate that staphylococci recovered from dairy cows with clinical endometritis contain an extensive and complex prevalence of SAg genes. Significant resistances to antibiotics were also seen, highlighting the need for the rational appliance of antibiotics in veterinary medicine.

BACKGROUND: Rice is the major food resource for nearly half of the global population; however, insect infestation could severely affect the production of this staple food. To improve rice insect resistance and reduce the levels of Bt toxin released into the environment, the Cry1Ab gene was conjugated to the rice rbcS promoter to express Bt toxin in specific tissues of transgenic plants. RESULTS: Eight marker‐free, T2 lines were separated from the T0 cotransformants. Using RT‐PCR, high levels of Cry1Ab expression were detected in the leaf but not in the seed. The Cry1Ab protein level ranged from 1.66 to 3.31 µg g−1 in the leaves of four transgenic lines, but was barely detectable in their seeds by ELISA. Bioassays showed that the mortality rate of silkworm larvae feeding on mulberry leaves dipped in transgenic rice flour and pollen was less than that of the positive control (KMD), and that their average weight was higher than that of KMD, suggesting that the Cry1Ab protein was not expressed in the seed and pollen. CONCLUSION: The transgene conferred a high level of resistance to insects and biosafety to the rice plants, which could be directly used in rice breeding. Copyright © 2012 Society of Chemical Industry