Antibiotic Susceptibility And Genetic Characteristics Of Campylobacter Isolated In China

Campylobacter is the major cause of human food-borne diseases, the common symptoms of campylobacteriosis is acute bacterial gastroenteritis in humans, which is usually mild, self-limiting and there’s no need of antibiotic treatment. Severe or prolonged infections can occur, in these circumstances, therapeutic intervention is usually necessary. For clinical treatment of campylobacteriosis, quinolones and macrolides are often prescribed; however, the resistance of Campylobacter to clinically important antibiotics is increasingly. For quinolones, the resistance rate has been nearly 100%, which has negative effects for the clinical treatment of campylobacteriosis and sharpen the disease burden. Development and transmission of antibiotic-resistant Campylobacter is complicated by the fact that Campylobacter is a zoonotic pathogen and exposed to antibiotics used in both animal production and human medicine, and these may add the resistance to some extent. To obtain the antibiotic resistance characteristics and the variation trend, the MICs (minimum inhibitory concentration) of 858 Campylobacter jejuni (C.jejuni) and Campylobacter coli (C.coli) strains isolated in China were determined by agar dilution method, the result shows that the resistance rate of quinolones is nearly 95%. We compared the resistance rate of 12 antibiotics of C.jejuni and C.coli, it shows that the resistance rate of erythromycin, streptomycin, and so on is higher in C. coli than in C.jejuni. The comparison result of the resistance rate of the four time periods from 1994 to 2013 shows that, the resistance rate of the isolates in our country is on rising, and this tendency is serious. Our study provided the data supporting to the surveillance of the antibiotic resistance Campylobacter in our country and it will do benefit to provide guidance for clinical treatment.The related mechanisms of antibiotic resistance in Campylobacter have been detected and the research of the prevention and control of diseases caused by Campylobacter on gene level is significant. The mechanisms of macrolide resistance have been identified as:modification of target sites by mutation (23S rRNA and ribosomal proteins L4 and L22), multidrug efflux pump CmeABC and the horizontally transmissible resistance mechanism——rRNA methylase gene ermB which was lately reported in 2013. In this study, we analyzed the mutations on 23S rRNA gene and the ermB gene on 158 erythromycin resistant isolates,82.91% (131/158) have the 23S rRNA A2075G mutation,18.99%(30/158) have detected the ermB gene,9 of the 30 ermB. positive C.coli have already know the type of the MDRGIs (multidrug resistance genomic islands),3 C.coli have completed the whole genome sequencing and the relative analysis, the analysis of 8 C.coli are in progress and another 10 C.coli are in the process of whole genome sequencing. The arising of the ermB gene and the relative MDRGI (multidrug resistance genomic islands) indicate that Campylobacter may be the antibiotic resistance gene pool in the intestinal tract. The result shows that the 23 S rRNA A2075G mutation and the ermB gene can acquire nearly 100%of the resistance characteristics of the Campylobacter isolates in China, we can design Real-time PCR to carry out tests of the stool samples from the diarrhea patients, then we can determin whether the isolate is resistant to antibiotics as well as identify the species. We also analysed the aadE-sat4-aphA-3 gene cluster on 221 streptomycin resistant isolates,10.86%(24/221) were positive, these will provide the theoretical foundation to the study of resistance mechanism and the basis to monitor of important resistance C.jejuni and C.coli strains.Genotyping is easy to be standardized and automated. In these years, with the developing of the microbiology, the differentiate technology has no longer been limited in the traditional phenotyping, PFGE, MLST have been widely used in the detection of the break out and the trace to the source. MLST has the advantages of high resolution, good repeatability, data standardization, the ability to compare and share with the international database and the process is simple and convenient. The aim of this study was to understand that if there were noteworthy clonal complex and genetic correlation among the antibiotic resistance Campylobacter and if there were special STs of isolates from poultry and livestock are closely related to the isolates from human. Our study carried out molecular sub-typing to 158 erythromycin resistance strains from different sources and 100 streptomycin resistance strains and the result shows that most of the C.coli strains from diarrhea patients and the strains from chicken have the similar genotype and antibiotic resistance, the resistance strains have not been gathered to noteworthy clonal complexes. The ST6322 and the ST1145 of the 158 erythromycin resistance strains have the ermB gene both, it reminded that maybe there are some correlation between these two STs, and further analysis is needed by adding more strains. The results of this study will benefit the surveillance and related food safety of Campylobacter in our country.