Potential of phage cocktails in the inactivation of Enterobacter cloacae—An in vitro study in a buffer solution and in urine samples

• The growth of the E. cloacae was inhibited by the three phages, resulting in a decrease of ≈3 log in buffer and of ≈2 log in urine.
• The use of cocktails with two or three phages was significantly more effective (≈4 log).
• Both phages were considered safe to inactivate the bacteria (no integrase and toxin codifying genes).
• Some bacteria remained viable in the presence of the phages, but their colonies were smaller than those of the non-treated control and were visible only after 5 days of incubation.

The objective of this study was to compare the dynamics of three previously isolated phages for Enterobacter cloacae in order to evaluate their ability to treat urinary tract infections (UTI). The phages genomes, survival, host range, were characterized, and the host-phage dynamics was determined in culture medium and urine samples. The presence of prophages in bacteria, host recovery and development of resistance to phage after treatment was also evaluated. The growth of the E. cloacae was inhibited by the three phages, resulting in a decrease of ≈3 log. The use of cocktails with two or three phages was significantly more effective (decrease of ≈4 log). In urine, the inactivation was still effective (≈2 log). Both phages were considered safe to inactivate the bacteria (no integrase and toxin codifying genes). Some bacteria remained viable in the presence of the phages, but their colonies were smaller than those of the non-treated control and were visible only after 5 days of incubation (visible after 24 h in the control). A high bacterial inactivation efficiency with phage cocktails combined with the safety of the phages and their long periods of survival, even in urine samples, paves the way for depth studies, especially in vivo studies, to control urinary tract infection and to overcome the development of resistances by the nosocomial bacterium E. cloacae.