| Campylobacter jejuni and Campylobacter coli are most common food-borne pathogens.Macrolides are one of the primary antimicrobials of choice for the treatment of campylobacteriosis.However,the extensive use of antimicrobial agents has facilitated the macrolides resistance rate in Campylobacter in the past few years.Additionally,the emergence of the rRNA methylase gene ermB in Campylobacter potentially compromises the efficacy of antimicrobial treatment for human infections.With the feature of stabilized horizontal transfer,the ermB-positive Campylobacter can pose a risk for dissemination.Thus,this study is to investigate the epidemiological characteristics of ermB gene in Campylobacter isolates in China,and explore the fitness changes and mechanisms of ermB-positive Campylobacter.Among a total of 1134 cecal or feces samples collected from chickens(n=590)and swine(n=544)from Shandong,Guangdong,and Shanghai in 2015,370 Campylobacter isolates were obtained and the overall isolation rate was 32.6%.37 ermB-positive C.coli were identified.Combined with the epidemiological data in 2013 and 2014,the prevalence of ermB gene increased gradually over three successive years and the positive rate were 2.1%?8.2%?10.0%,separately.The rates of ermB-positive Campylobacter in Guangdong(15.1%)was higher than that in Shanghai(3.3%)and Shandong(1.1%),and increased remarkably over the experimental period.Expansion of the ermB in Campylobacter with similar type from chicken isolates from Shanghai and Guangdong to human isolates identified previously in Shanghai was also observed.Due to the rising rate of ermB in Campylobacter,we speculated that the fitness of Campylobacter has changed by ermB gene.To explore the fitness changes of ermB-positive Campylobacter,the growth determinations and pairwise competitions in vitro and in vivo were examined using two pairs of clonally related and isogenic ermB engineering Campylobacter.Compared with the susceptible strains,the ermB-positive strains showed significant cost of fitness both in vitro and in vivo.Meanwhile,the fitness compensation occurred during the pairwise competitions in vivo.The tendency of the fitness changes in ermB-positive Campylobacter,which showed down first and then up,was different with the Ery-resistant strains which carried 23S rRNA mutant.Meanwhile,the compensation occurred exactly in the compensatory strain by the verification test(in vitro and in vivo).To understand the mechanisms of fitness changes in ermB-positive strains,quantitative proteomic analysis methods iTRAQ and 2D-DIGE were used to compared the difference among the susceptible strain,resistant strain and compensated strain in the protein level.Compared with the susceptible strains,a total of 123 differential proteins were selected in resistant strain through iTRAQ,while 25 differential proteins were selected between compensated and resistant strain.Additionally,we also selected 13 differential proteins through 2D-DIGE.Analysis by GO,Pathway and COG,these proteins influenced on metabolic pathway and colonization ability of Campylobacter.Further analysis showed that the fitness cost of Campylobacter might be related to the deficiency of motility and energy conversion,because the over expression of ErmB protein and flagella proteins might consume additional energy of strain.Meanwhile,the strain could restore the ability of energy utilization and compensate the proteins related to motility by itself during the competition in vivo.In summary,the increasing prevalence and transmission of ermB gene both in animal and human were observed in Campylobacter among part regions of China.Apart from the pressure of antimicrobial agents,the fitness compensation of ermB-positive Campylobacter may also be an essential factor which attributed to the dissemination.All the study results developed the understanding of the epidemiology of ermB-positive Campylobacter and provided a scientific basis on exploring the new way to control and prevent the dissemination of resistant Campylobacter. |
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