Abstract
Numerous studies have been conducted to examine the molecular mechanism of Haemophilus parasuis resistance to antibiotic, but rarely to tildipirosin. In the current study, transcriptional profiling was applied to analyse the variation in gene expression of JS0135 and tildipirosin-resistant JS32. The growth curves showed that JS32 had a higher growth rate but fewer bacteria than JS0135. The cell membranes of JS32 and a resistant clinical isolate (HB32) were observed to be smoother than those of JS0135. From the comparative gene expression profile 349 up- and 113 downregulated genes were observed, covering 37 GO and 63 KEGG pathways which are involved in biological processes (11), cellular components (17), molecular function (9), cellular processes (1), environmental information processing (4), genetic information processing (9) and metabolism (49) affected in JS32. In addition, the relative overexpression of genes of the metabolism pathway (HAPS_RS09315, HAPS_RS09320), ribosomes (HAPS_RS07815) and ABC transporters (HAPS_RS10945) was detected, particularly the metabolism pathway, and verified with RT-qPCR. Collectively, the gene expression profile in connection with tildipirosin resistance factors revealed unique and highly resistant determinants of H. parasuis to macrolides that warrant further attention due to the significant threat of bacterial resistance.
Highlights
The pathogen Haemophilus parasuis (HPS) is among the most commonly identified Gram-negative bacteria mainly causing serofibrinous polyserositis and arthritis which leads to major economic losses in the swine industry worldwide[1,2,3]
The serovars of JS0135, JS32 and HB32 were amplified by PCR with the appropriate primers listed in Table 1 and were identified as serovars 4, 4 (320 bp) and 13 (840 bp), respectively (Supplementary Figure S1)
JS32 was induced from JS0135 and could grow well on tryptone soy agar containing 256 Minimal inhibitory concentration (MIC) tildipirosin
Summary
The pathogen Haemophilus parasuis (HPS) is among the most commonly identified Gram-negative bacteria mainly causing serofibrinous polyserositis and arthritis which leads to major economic losses in the swine industry worldwide[1,2,3]. The resistance of Pasteurella multocida (PM) to macrolides including tildipirosin, tilmicosin and gamithromycin has previously been reported. The resistance characteristics of HPS to different antibiotics including fluoroquinolone, marcolides, tetracycline and beta-lactam has been investigated in previously described reports and some classical resistant genes such as acrAB, Tet B, Tet A, ErmB, etc[16,17,18,19]. Several resistance HPS strains were isolated in diseased swine and induced in lab, and a transcriptomic approach was applied to achieve a genetically tildipirosin-resistant characteristic and revealed promising therapeutic targets to combat resistance[20]. Transcriptional profiling analysis provides distinct and detailed genomic-level information related to specific pathogenic mechanisms involving virulence factors and resistance genes[8, 21]. A systematic approach of transcriptional profiling may aid the discovery of the resistance mechanisms of HPS to tildipirosin
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