To isolate bacteriophages against extensively-drug resistant Acinetobacter baumannii from hospital sewage and analyze their biological characteristics.

Extensively-drug resistant Acinetobacter baumannii isolated from several hospitals in Shanghai during December, 2013 to July, 2014 were used as host bacteria, adopting double-layer agar method to isolate bacteriophages from raw sewage of these hospitals. The phage with broad host range was selected for further study, including observation of electron microscopic morphology, examination of thermal stability, pH stability and the optimal MOI, drawing of the adsorption, one-step-growth and infection curves, as well as sequencing of the phage genome DNA.

An extensively-drug resistant Acinetobacter baumannii bacteriophage vB_AbaP_PD-AB9 (PD-AB9 for short) with broad host range was isolated, and electron microscopy revealed it belonged to Podoviridae family. The optimal MOI of PD-AB9 was 0.001. PD-AB9 remained stable among 4 ℃ to 50 ℃ and pH 4 to 11. In the adsorption experiment, the adsorption rate of PD-AB9 reached above 95% within 5 min.PD-AB9 had a latent period of 4 min and a burst size of 213. PD-AB9 could obviously restrain the host growth, with faster effect at the higher MOIs (MOI=1, 0.1, 0.01) than at the lower ones (MOI=0.001, 0.000 1). Furthermore, genome of PD-AB9 proved to be a double-stranded linear DNA with size of 40 938 bp and GC content of 39.34%.

PD-AB9 exhibits good thermal stability, wide pH tolerance range, very fast adsorption, a short latent period, a large burst size and it could quickly cause effective host lysis after infection. Therefore, PD-AB9 is promised to act as a new antimicrobial agent to control drug-resistant Acinetobacter baumannii infections and its bio information remains to be further studied.(Chin J Lab Med, 2016, 39: 296-300)

Bacteriophages; Acinetobacter baumannii; Drug resistance, bacterial; Biological assay; Genome components