Clinical Antibiotic-resistant Acinetobacter baumannii Strains with Higher Susceptibility to Environmental Phages than Antibiotic-sensitive Strains

Li-Kuang Chen,Chun-Chieh Tseng,Chieh-Chen Cheng,Kai-Chih Chang,Shu-Chen Kuo,Tren-Yi Chen,Pei-Ying Yu,Chih-Hui Chang

doi:10.1038/s41598-017-06688-w

Abstract

Antibiotic-resistant Acinetobacter baumannii is associated with nosocomial infections worldwide. Here, we used clinically isolated A. baumannii strains as models to demonstrate whether antibiotic resistance is correlated with an increased susceptibility to bacteriophages. In this study, 24 active phages capable of infecting A. baumannii were isolated from various environments, and the susceptibilities of both antibiotic-sensitive and antibiotic-resistant strains of A. baumannii to different phages were compared. In our study, a total of 403 clinically isolated A. baumannii strains were identified. On average, the phage infection percentage of the antibiotic-resistant A. baumannii strains was 84% (from 81–86%), whereas the infection percentage in the antibiotic-sensitive A. baumannii strains was only 56.5% (from 49–64%). In addition, the risk of phage infection for A. baumannii was significantly increased in the strains that were resistant to at least four antibiotics and exhibited a dose-dependent response (p-trend < 0.0001). Among all of the A. baumannii isolates, 75.6% were phage typeable. The results of phage typing might also reveal the antibiotic-resistant profiles of clinical A. baumannii strains. In conclusion, phage susceptibility represents an evolutionary trade-off in A. baumannii strains that show adaptations for antibiotic resistance, particularly in medical environments that have high antibiotic use.

Highlights

Because of the rapid accumulation of resistance to multiple antibiotics, carbapenems are the only effective group of antibiotics against MDRAB infections
A. baumannii was more sensitive to the tigecycline and colistin groups compared with the six other groups
All of the A. baumannii strains were sensitive to colistin, and only a small fraction was resistant to tigecycline

Summary

Introduction

Because of the rapid accumulation of resistance to multiple antibiotics, carbapenems are the only effective group of antibiotics against MDRAB infections. Twenty-four new phage strains have been isolated by our group, and we expect that these phages have the potential for use as biocontrol agents[16] and could be applied in clinical and environmental settings[15]. The development of resistance to different antibiotics may be correlated with the evolution of resistance to phages[17] This antagonistic coevolutionary relationship among bacteria, antibiotics and phages must be investigated via studies focused on clinical and environmental settings. We used clinically isolated A. baumannii strains as models to demonstrate the correlation between bacterial resistance to antibiotics and phages. The susceptibilities of both antibiotic-sensitive and antibiotic-resistant A. baumannii to 24 phage strains were compared. This study was conducted to determine whether the development of resistance to different types and numbers of antibiotics in A. baumannii generated significant fitness costs that impacted the evolution of resistance to phages in A. baumannii

Methods

Results

Conclusion