Title:Isolation, Diversity And Integron Analysis Of The Antibiotic Resistant Escherichia Coli In Jinan Aquatic Environment

Since antibiotics were discovered, more and more antibiotics are widely used in various infections, treatment and livestock production and have become a powerful weapon of thepeople to fight bacteria. However, due to people’s irrational use and even abuse of antibiotics, the phenomena of bacterial resistance become more acute and bacterial resistance and multipledrug resistance result in serious consequences, for example the journal of The Lancet Infectious Diseases has reported super bacteria NDM-1(called the New Delhimetallo-s-lactamase-1, NewDelhi metallo-β-lactamase1) in2010. This superbug is able to withstand almost all antibiotics, and is expected that in10years no drug can resist it. With the increasing of severe bacterial resistance and drug-resistant infections, the study of bacterial resistance mechanisms and their mode of transmission have become a hot research.Escherichia coli is the normal habitat of the intestines in human and animals and also an important pathogen that can cause intestinal or extraintestinal infectious. E. coli is widely distributed in the surrounding water environment, and can infect humans or animals through the food chain. The species E. coli comprehends different phylogenetic lineages, often with distinct patterns of distribution among human populations, animals or the environment. Currently with the extensive use of antibiotics, E. coli resistance is increasingly grim. Foreign studies have reported different sources of E. coli, wheres there is little research about it in China’s water environment.Among the mechanisms of E. coli resistance, integron as a carrier in horizontal gene transfer mechanism plays an important role, and it can carry resistance genes to spread among the same species and or different genus. Integrons are mobile DNA elements that can capture and excise genes, particularly those responsible for antibiotic resistance (AR) and usually are located on the chromosome or the removable components. While integrons mobilize AR gene cassettes, they themselves are not mobile; however, they are frequently associated with transposons or transferable plasmids that allow them to spread among bacterial populations. On the basis of integrase amino acid sequence similarity, integrons are divided into five classes. Research conducted over the past decade suggests that class1integrons play a vital role in the dissemination of antibiotic resistance, class2integrons are found less because of its integrase containing a stop codon, and class3integrons have reported only four cases until2010. Gene cassettes often carry antibiotic resistance genes and provide this resistant resource through the expression of cassette-associated genes by an integron-borne promoter cassettes array. At present, more than100gene cassettes have been discovered.This experiment was to study the distribution of integrons among E. coli isolated from the water environment in Jinan, Shandong Province, China. Because of many antibiotics used in the hospitals, this study mainly collected samples from the hospitals, as well asnon-hospital environment, Xiaoqing River in Jinan. The work was to investigate the distribution of phylogenetic lineages and integrons among the drug-resistant E. coli.In this study, we isolate418E. coli strains from the wastewater samples of several hospitals and XiaoQing River. Among them,323was detected class1integron,10within class2integron and class3integron was not detected. The prevalence of integrons of HWW (hospital waste water) was higher than that of XQRWW (XiaoQing River waste water). Phylogenetic assay showed that most isolates belonged to subgroups A, followed by group B1and group B2and D were least. The gene cassettes of integrons are usually involved in antibiotic resistance. These gene cassettes resulted in fifteen types of gene cassette arrays associated with class1integron and they were orfl; dhfrⅦ; aadA2; dfrA25; aadA23; dfrA1-orfC; arr-3-dfrA27; dfrA5-ereA2; dfrA1-aadAl; dfrA17-aadA5; dfrA12-orfF-aadA2; aacA4-cmlA1-variant; aacA4-catB3-dfrA1; aadB-cat-blaOXA-10-aadA1; aac(6’)-Ib-blaoxa-30-catB3-arr3and also one gene cassette array of class2integron were identified----dfrA1-sat1-aadA1.