A fast method for large-scale isolation of phages from hospital sewage using clinical drug-resistant Escherichia coli

With the continued emergence of multi-drug resistant genes and drug-resistant bacteria, the functions and applications of traditional antibiotics are challenged. Thus, products that can be combined with existing antibiotics or replace them are of great interest to the research and medical communities. As a natural parasite of bacteria, phages have been reconsidered for use in treating super or drug-resistant bacterial infections. The main aim of this study was to isolate new phages from hospital sewage, especially those with broad-spectrum infectivity for the establishment of an Escherichia phage library. According to differences in their infection spectrum, bacteriophages were identified using a plaque method. In total, 18 E. coli phages were isolated from hospital sewage. The characteristics of the wide host spectrum E. coli bacteriophage E12P1 were further studied. Electronic micrographs indicated that phage E12P1 had a cubic symmetry and a long tail. The growth curve suggested the incubation time was 30 min, the burst phase was 20 min, and the burst size was 43. This plaque-forming method could be adopted to isolate E. coli phage easily, rapidly and in large quantities. Among the 18 isolated E. coli phages, 10 of them had a broad host range in E. coli and warrant further study. Key words : Escherichia coli phages, large-scale isolation, drug resistance, biological properties.