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Fluoroquinolones are frequently used to treat infectious disease that is caused by Escherichia coli in dairy cattle. However, fluoroquinolone resistance occurs and is due either to chromosomal mutations in the bacterial topoisomerase genes and/or to plasmid-mediated resistance genes. The purpose of this study was to determine the prevalence and molecular characteristics of fluoroquinolone resistance determinants in E. coli strains ( n=148) isolated from dairy cattle with bovine endometritis in Inner Mongolia (China). Analysis of the mutations in the quinolone resistance-determining regions of resistant E. coli isolates confirmed previously reported substitutions in the GyrA and ParE. However, we identified additional substitutions in the ParC and GyrB that have not been reported earlier. No plasmid-mediated quinolone resistance genes in any of the isolates were found. The number of point mutations found per isolate correlated with an increase in the minimum inhibitory concentration of ciprofloxacin. Overall, 45.5% of the isolates were positive for the class I integrase gene along with four gene cassettes that were responsible for resistance to trimethoprim ( dfr1 and dfrA17) and aminoglycosides ( aadA1 and aadA5), respectively. The prevalence of extended-spectrum β-lactamases (ESBLs) was 100%, and the blaTEM gene was predominant in all of the isolates. In conclusion, our results identify the mechanism of quinolone resistance for the first time and reveal the prevalence of integron and ESBLs in E. coli isolates from dairy cattle with bovine endometritis in China after 20 years of quinolone usage in cattle. [ABSTRACT FROM AUTHOR]

Abstract: The composition and characterization of dissolved organic matter (DOM) and colloid organic matter (COM) in the coastal surface waters of Qingdao, China were examined. Water samples were collected in Spring 2008 from the Jiaozhou Bay and its adjacent area and fractionated into total dissolved (<0.45μm), colloidal (10kDa–0.45μm) and cutoff (<10kDa) fractions with the cross-flow ultrafiltration (CFF) system. The excitation–emission-matrix (EEM) spectral properties, the absorbance values at 254nm (A 254) and dissolved organic carbon (DOC) of the DOM were observed having the colloidal ratios of 8.7%, 6.2%, and 2.2%, respectively, and exhibiting a decreasing trend. Total dissolved carbohydrates (TCHO) and total hydrolysable amino acids (THAA) comprised 24% of the bulk DOC. Among them, the free monosaccharides (MCHO) and dissolved combined amino acids (DCAA）were the major fractions, followed by polysaccharides (PCHO) and dissolved free amino acids (DFAA). Colloidal TCHO and THAA concentrations were 3.2µM C and 0.3µM, respectively. They comprised ∼35% of the colloid organic carbon (COC), among which PCHO and DCAA were the dominating fractions. The dissolved carbohydrates and amino acids are mostly concentrated in the cutoff fraction. The A 254 values and DOC concentrations inside the Jiaozhou Bay were apparently higher than those outside, while pH and salinity were slightly lower, which might be due to the influence of terrestrial input and the semi-enclosed bay. The distribution pattern of TCHO was found having basically the same as the distributions of A 254 and DOC. [Copyright &y& Elsevier]