LAUSR

The phage lytic spectrum is usually limited to only a few strains of the same bacterial species that it can lyse. Bacterial strains in a species are commonly classified into a sequence type (ST) using the multilocus sequence typing (MLST) approach in clinical molecular epidemiology. The aim of this study is to determine whether the phage lytic spectrum is associated with STs. An MLST analysis of 11 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli clinical isolates revealed that the most common isolates belonged to ST73 or ST131, with four isolates each. Phages were isolated from a sewage sample using various E. coli strains as hosts. The relationship between phage lytic spectra with ESBL-producing E. coli ST73 and/or ST131 isolates and STs was evaluated using Fisher's exact test. The lytic spectra of phages were found to be significantly dependent on ST classification of ST73 or 131, suggesting that a phage lysing an isolate belonging to a particular ST could lyse other isolates belonging to the same ST. Furthermore, we successfully isolated wide-host-range phages lysing all clinical isolates in this study belonging to two clinically important ST types (ST73 and ST131).