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Detection of antimicrobial resistance and virulence-related genes in Streptococcus uberis and Streptococcus parauberis isolated from clinical bovine mastitis cases in northwestern China
ZHANG Hang, YANG Feng, LI Xin-pu, LUO Jin-yin, WANG Ling, ZHOU Yu-long, YAN Yong, WANG Xu-rong, LI Hong-sheng
2020, 19 (11): 2784-2791.   DOI: 10.1016/S2095-3119(20)63185-9
Abstract118)      PDF in ScienceDirect      
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.
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Penicillin-resistant characterization of Staphylococcus aureus isolated from bovine mastitis in Gansu, China
YANG Feng, LIU Long-hai, WANG Ling, WANG Xu-rong, LI Xin-pu, LUO Jin-yin, ZHANG Zhe, ZHANG Shi-dong, YAN Zuo-ting, LI Hong-sheng
2017, 16 (08): 1874-1878.   DOI: 10.1016/S2095-3119(16)61531-9
Abstract1414)      PDF in ScienceDirect      
    Bovine mastitis caused by Staphylococcus aureus is difficult to treat because of increasing resistance against antibiotics, especially penicillin. β-Lactamase and biofilm are responsible for penicillin resistance of S. aureus. The aim of this study was to investigate the β-lactamase activity and biofilm formation capacity of 37 penicillin-resistant S. aureus strains (35 were blaZ positive and 2 were blaZ negative) from bovine mastitis in Gansu Province, China, as well as to measure the intercellular adhesion genes icaA and icaD of these strains. β-Lactamase Test Kit was used to determine the β-lactamase activity, biofilm formation was tested by semi-quantitative adherence assay method. Moreover, the presence of icaA and icaD were measured by PCR. A total of 32 penicillin-resistant S. aureus strains, including the two blaZ-negative strains, were identified as β-lactamase producers. All tested S. aureus isolates produced biofilm in the microtiter plate assay. Meanwhile, all these strains were PCR-positive for the ica locus, icaA and icaD. The study indicated high prevalence of β-lactamase activity, biofilm-forming capacity, and the ica genes among the penicillin-resistant S. aureus isolates, and implied that S. aureus resistant to penicillin was attributed to multiple mechanisms.
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Genetic characterization of antimicrobial resistance in Staphylococcus aureus isolated from bovine mastitis cases in Northwest China
YANG Feng, WANG Qi, WANG Xu-rong, WANG Ling, LI Xin-pu, LUO Jin-yin, ZHANG Shi-dong, LI Hong-sheng
2016, 15 (12): 2842-2847.   DOI: 10.1016/S2095-3119(16)61368-0
Abstract1119)      PDF in ScienceDirect      
    Staphylococcus aureus is the most common etiological pathogen of bovine mastitis. The resistant strains make the disease difficult to cure. The aim of this study was to characterize the genetic nature of the antimicrobial resistance in S. aureus cultured from bovine mastitis in Northwest China in 2014. A total of 44 S. aureus were isolated for antimicrobial resistance and resistance-related genes. Antimicrobial resistance was determined by disc diffusion and the corresponding resistance genes were detected by PCR. Phenotype indicated that S. aureus isolates were resistant to penicillin (84.09%), erythromycin (20.45%), tetracycline (15.91%), gentamicin (9.09%), tobramycin (6.82%), kanamycin (6.82%) and methicillin (2.27%). 9.09% of the S. aureus isolates were classified as multidrug resistant. In addition, genotypes showed that the isolates were resistant to rifampicin (100%, rpoB), penicillin (95.45%, blaZ), tetracycline (22.73%, tetK, tetM, alone or in combination), erythromycin (22.73%, ermB or ermC), gentamicin/tobramycin/kanamycin (2.27%, aacA-aphD), methicillin (2.27%, mecA) and vancomycin (2.27%, vanA). Resistance to tetracycline was attributed to the genes tetK and tetM (r=0.558, P<0.001). This study noted high-level geno- and phenotypic antimicrobial resistance in S. aureus isolates from bovine mastitis cases in Northwest China.
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