Abstract
BackgroundHaemophilus parasuis is a common porcine respiratory pathogen that causes high rates of morbidity and mortality in farmed swine. We performed a molecular characterization of antimicrobial resistance genes harbored by H. parasuis from pig farms in China.MethodsWe screened 143 H. parasuis isolates for antimicrobial susceptibility against six fluoroquinolone antibiotics testing by the broth microdilution method, and the presence of 64 antimicrobial resistance genes by PCR amplification and DNA sequence analysis. We determined quinolone resistance determining region mutations of DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE). The genetic relatedness among the strains was analyzed by pulsed-field gel electrophoresis.ResultsSusceptibility test showed that all isolates were low resistance to lomefloxacin (28.67%), levofloxacin (20.28%), norfloxacin (22.38%), ciprofloxacin (23.78%), however, high resistance levels were found to nalidixic acid (82.52%) and enrofloxacin (55.94%). In addition, we found 14 antimicrobial resistance genes were present in these isolates, including blaTEM-1, blaROB-1, ermB, ermA, flor, catl, tetB, tetC, rmtB, rmtD, aadA1, aac(3′)-llc, sul1, and sul2 genes. Interestingly, one isolate carried five antibiotic resistance genes (tetB, tetC, flor, rmtB, sul1). The genes tetB, rmtB, and flor were the most prevalent resistance genes in H. parasuis in China. Alterations in the gyrA gene (S83F/Y, D87Y/N/H/G) were detected in 81% of the strains and parC mutations were often accompanied by a gyrA mutation. Pulsed-field gel electrophoresis typing revealed 51 unique patterns in the isolates carrying high-level antibiotic resistance genes, indicating considerable genetic diversity and suggesting that the genes were spread horizontally.DiscussionThe current study demonstrated that the high antibiotic resistance of H. parasuis in piglets is a combination of transferable antibiotic resistance genes and multiple target gene mutations. These data provide novel insights for the better understanding of the prevalence and epidemiology of antimicrobial resistance in H. parasuis.
Highlights
Haemophilus parasuis is the etiological agent of Glässer’s disease that causes significant morbidity and mortality as well as economic losses in the global pig industry(Oliveira & Pijoan2004)
Antimicrobial therapy is used to prevent and control this infection even though antimicrobial agents are used for growth promotion in pigs(Lancashire et al 2005)
We examined 143 H. parasuis strains and 16 (11.2%) carried βlactamases including TEM-1 and ROB-1
Summary
Haemophilus parasuis is the etiological agent of Glässer’s disease that causes significant morbidity and mortality as well as economic losses in the global pig industry(Oliveira & Pijoan2004). Haemophilus parasuis is the etiological agent of Glässer’s disease that causes significant morbidity and mortality as well as economic losses in the global pig industry(Oliveira & Pijoan. Increases in antibiotic resistance among bacteria is most often the result of antibiotic resistance gene (ARG) transfer mediated by mobile DNA elements such as plasmids, transposons and integrons in Gram-negative bacteria(Lancashire et al 2005; San Millan et al.2007). The most prominent ARG types associated with resistance in H. parasuis include ROB-1, tetB, tetL, qnrA1, qnrB6, aac(6’)-Ib-cr, lnu(C) and flor(Dayao et al 2016; Guo et al 2011; Kehrenberg et al 2005; Lancashire et al 2005; Li et al 2015; San. Haemophilus parasuis is a common porcine respiratory disease that causes high rates of morbidity and mortality in farmed swine. We performed a molecular characterization of antimicrobial resistance genes harbored by H. parasuis from pig farms in China
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