Characterization of Heterogeneous Drug-resistant Escherichia coli and Its Drug-resistant Subpopulations from Milk Sources
The aim of this study was to investigate whether heteroresistance exists in milk-derived Escherichia coli,and to characterize the biology of heteroresistance E.coli and its resistant sub-groups,in order to explore possible heteroresistance mechanisms.The minimum inhibitory con-centration(MIC)of one E.coli strain named D1 which isolated from raw cow's milk was deter-mined by micro broth dilution method.The heteroresistance of E.coli was initially screened by the K-B paper diffusion method,and confirmed by the population analysis profile(PAP),and the heteroresistance characteristics of E.coli were investigated by resistance stability test and bio-film assay,finally,the mechanism of heterogeneous resistance was analyzed by whole genome se-quencing and resequencing.The results showed that this E.coli was intermediary to polymyxin E,resistant to sulfisoxazole,and showed sensitivity to the rest of the antibiotics,and two E.co-li-antimicrobial heteroresistance combinations were screened out by K-B paper diffusion assay.PAP confirmation showed that the MIC/maximum noninhibitory concentration(MNIC)ratio of E.coli was 8,and the occurence frequency of the resistant subgroups was 2.45×10-6,confir-ming D1 to be a heteroresistance doxycycline-resistant strain.The stability of transmission showed that the resistant subpopulation could not be inherited stably,while there was no growth lag in the growth test,and the biofilm production of the resistant subpopulation was significantly greater than that of the parental strain.Whole genome sequencing revealed that there was a gene mutation between the resistant subpopulation and the parental strain,and the mutant gene txR is a specific transcriptional regulator that may lead to heteroresistance to doxycycline in E.coli.In conclusion,the existence of heteroresistance to doxycycline in E.coli from milk sources suggests that doxycycline antibiotics should be used rationally in the clinic,therefore,more attention should be paid to the occurrence of heteroresistance when using doxycycline in clinical treatment,and effective detection methods need to be used to provide guidance for clinical prevention and control and rational use of antibiotics.
万方数据
维普
