| Background and ObjectivesThe dissemination of extended-spectrum p-lactamase(ESBL)-producing Escherichia coli from food-producing animals to the surrounding environment hasattracted much attention.Most of the studies have been focused on the investigation of the use of antibiotics andperformed to characterizeESBL-producing Enterobacteriaceae in large-scale farms.Lack of research on households feeding,defined ashouseholds with backyard pig farms.The aim of the present study was to assess the occurrence of ESBL-producing Enterobacteriaceae and to further characterizethedisseminationofESBL-producingEnterobacteriaceaefromfeedingwastestosurrounding environment(soil and aquatic environment).MethodsDuring 19 to 24,July 2015,feeding wastes samples(pig fecal,waste water and outlet sediment)and surrounding environment samples(soil and vegetables,river water,river sediment and well water)were collected from 12 villages inruralareaofhouseholds with backyard pig farms in Shandong province;Confirmation of species was obtained by matrix-assisted laser desorption ionization-time of flight mass spectrometry(MALDI-TOF-MS).Antimicrobial susceptibility profiles were determined using the agar dilution method recommended by the Clinical and Laboratory Standards Institute(CLSI,2016)and the EUCAST criteria(http://www.eucast.org/clinical_breakpoints/).The gene-groups blaCTX-Mwere screenedfor using PCR;Cloning and homology analysis were performed by multiocus sequence typing(MLST)and pulsed field gel electrophoresis(PFGE).Results1.45 ESBL-producing E.coli(47.87%)were detected in feeding wastes,and the detection rate of pig fecal was significantly higher than that of waste water and outlet sediments.The antimicrobial susceptibility results showed that the multidrug resistance rate of the strains was 100%,with high resistance to cefotaxime(97.78%),tetracycline(95.56%),trimethoprim/sulfamethoxazole(86.67%)and florfenicol(80%)especially.None strains were resistant to meropenem and tigecycline.Overall,6blaCTX-M subtypes were detected,of those,the most common bblaCTX-M genotypes were blaCTX-M-65(12 isolates)and blaCTX-M-14(11 isolates).27 STs were detected in 45 ESBL-producing strains,ST 10 type and its complex were most prevalent that only 24.44%(11/45).2.None ESBL-producing E.coli was detected in vegetable samples.4 ESBL-producing E.coli(16.67%)were detected in soil samples.The antimicrobial susceptibility results showed that the multidrug resistance rate of the strains was 100%,the characters of antimicrobial resistance strains were same between soil and feeding wastes.Overall,onlyblaCTX-M-65,belonged CTX-M group 9,was detected;According toPFGE analysis,3strains homologous to the isolates fromfeeding waste(>80%similarity)were considered to be related.3.The detection rate ofESBL-producing E.colifrom river water(64%)and river sediment(76.47%)was higher than those in well water(23.26%).The antimicrobial susceptibility results showed that the drug resistance characters of isolates from aquatic environmentwere the same to those in feeding wastes,and the multidrug resistance rate was]00%.PCRs and DNA sequencing indicated that of the 6 ST types detection,blaCTX-M-14 was the dominant gene that belonged to CTX-M-9 group.A majority of the E.coli isolates showed unique PFGE profiles and,as a result,were unlikely to be the cause of an epidemic,as the same time,we also found 7 isolates from river water and 3 isolates from well water homologous to the isolates fromfeeding waste(>80%similarity)carrying same CTX-M gene or belong to same CTX-M group,were considered to be related.Conclusions1.Inrural area of households with backyard pig farms in Shandong Province,the ESBL-producing E.coli were widespread in feeding wastes and its surrounding environment(soil and water environment),except for vegetables.2.In rural area of households with backyard pig farms in Shandong Province,the molecular typing of ESBL-producing E.coli from feedingwastes and its surroundings(soil and water environment)showed diversity,and no evolutionary convergent relationship.3.The animal-producing sources CTX-M genes,blaCTX-M-65 and blaCTX-M-14.were the most prevalent CTX-M gene in feeding wastes and its surrounding environment(soil and water environment)in this area,overall,the ST10 type and its complex,which widespread in livestock and poultry werealso quite popular in the surrounding environment,isolates from soil and water environment showed homologous to that fromfeeding waste,the results proved the transmissionof antibiotics resistance from the feeding waste to its surrounding environment. |
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