Erythromycin Susceptibility and Genomic Regions Characterization of Campylobacter coli

turkeys;intervening sequence;MLST;erythromycin susceptibility;Campylobacter coli

Chan, Kamfai ; Todd Klaenhammer, Committee Member,Fred Breidt, Committee Member,Sophia Kathariou, Committee Chair,Craig Altier, Committee Member,Chan, Kamfai ; Todd Klaenhammer ; Committee Member ; Fred Breidt ; Committee Member ; Sophia Kathariou ; Committee Chair ; Craig Altier ; Committee Member

University:North Carolina State University

关键词: turkeys;    intervening sequence;    MLST;    erythromycin susceptibility;    Campylobacter coli;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/3717/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

Campylobacter jejuni and Campylobacter coli are major bacterial food-borne pathogens that cause enteric diseases worldwide, resulting in significant public health and economic burden. These two closely related species colonize a wide range of farm animals including turkeys, pigs, chickens, and cattle. Consumption of meat (especially poultry) contaminated with C. jejuni or C. coli has been implicated as the major route of infection. When needed, antibiotics used for treatment are fluoroquinolones or macrolides such as erythromycin.Recent studies have shown that the percentage of C. coli that have resistance to antimicrobials, including those typically used for treatment of human campylobacteriosis, has increased, making it a top priority to investigate themechanisms for acquisition and dissemination of antimicrobial resistance in these pathogens. Certain Campylobacter strains harbor a transcribed intervening sequence (IVS) in their 23S rRNA genes. Following transcription, the IVS is excised, leading to fragmentation of the 23S rRNA. The origin and possible functions of the IVS are unknown. Furthermore, the distribution of IVS-harboring strains within Campylobacter populations is poorly understood. In this study, strains of Campylobacter coli from turkeys, representing numerous different multilocus sequence typing (MLST)-based sequence types (STs), were characterized in terms of IVS content and erythromycin susceptibility. We identified strains that harbored IVSs in all three 23S rRNA genes, as well as strains lacked IVSs from at least one of the genes.The STs of the latter strains belonged to an unusual cluster of C. coli STs ('cluster II'), earlier found primarily in turkey strains, and characterized by presence of the C. jejuni aspA103 allele. The majority of strains harboring IVSs in all three 23S rRNA genes were resistant to erythromycin.In contrast, cluster II strains, which harbored at least one IVS-free 23rRNA gene, were susceptible to the antibiotic.Cluster II strains could be transformed to erythromycin resistance with genomic DNA from C. coli that harbored IVS and the A2075G transition in the 23S rRNA gene, associated with resistance to erythromycin in Campylobacter. Erythromycin-resistant transformants harbored both the A2075 transition and IVS.The findings suggest that absence of IVS in C. coli from turkeys is characteristic of a unique clonal group of erythromycin-susceptible strains, and that IVS can be acquired by these strains via natural transformation to erythromycin resistance.Analysis of C. coli and C. jejuni strains isolated from broilers, turkeys and swine has shown the association of the lack of IVS and erythromycin susceptibility is unique to C. coli from turkeys.The presence of the C. jejuni aspA103 allele in the chromosome of cluster II C. coli strains is a unique characteristic of this clonal group.To further characterize the genome composition in the aspA region in cluster II strains, we determined the corresponding DNA sequences from two turkey-derived cluster II C. coli strains (6979 and 7474, of ST-1150 and ST-1161, respectively).Genomic organization upstream of the aspA gene was divergent between these two cluster II strains and the reference strain C. coli RM2228, the genome sequence of which has been completed. Genes encoding a putative Crp-family transcriptional regulator (CCO0137) and a conserved hypothetical protein (CCO0138) that were present in C. coli RM2228 and C. coli 6818 were not found in the same genomic region in C. coli 6979 or C. coli 7474. Moreover, single nucleotide polymorphism (SNP) analysis revealed that genes encoding subunit II of cytochrome d ubiquinol oxidase (cydB) and a putative aspartate racemase (CJ0085c) harbored numerous C. jejuni-specific SNPs.Interestingly, genes encoding subunit I of cytochrome d ubiquinol oxidase (cydA) and uracil-DNA glycosylase (ung) harbored C. coli-specific SNPs in their 5' portions but C. jejuni-specific SNPs in their 3' portions, suggesting that these may be hybrid genes that were originated from C. jejuni and C. coli.Our data suggest the presence of recombination events in the genomic region between cydA and ung in cluster II strains of C. coli. Such genomic features may contribute to the observed prevalence of cluster II strains among C. coli from turkeys, and to the characteristic susceptibility to erythromycin exhibited by these strains.