Relationship between Phage Lytic Spectra and Sequence Types in Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated in Japan

The lytic spectrum of phages is usually limited to only a few strains of the same bacterial species that can lyse. In clinical molecular epidemiology, bacterial strains are commonly classified into sequence types (STs) using the multilocus sequence typing (MLST) approach. The aim of this study was to determine the association between the phage lytic spectrum and STs. MLST analysis of 11 extended-spectrum (beta-lactamase (ESBL)-producing Escherichia coli clinical isolates revealed that most belonged to ST73 or ST131, with four isolates each. Phages were isolated from sewage samples using various E. coli strains as hosts. The relationship between phage lytic spectra of ESBL-producing E. coli isolates ST73 and ST131 and STs was evaluated using Fisher's exact test. The lytic spectra of phages were significantly dependent on the ST classification of ST73 or ST131, suggesting that a phage lysing an isolate belonging to a particular ST could lyse other isolates of the same ST. We successfully isolated wide -host-range phages lysing all clinical isolates belonging to two clinically important ST types (ST73 and ST131).