Evaluation of Potential ARG Packaging by Two Environmental T7-Like Phage during Phage-Host Interaction

• Main Authors: Junlin Liu, Peng Liu, Fenglin Feng, Junxuan Zhang, Fulin Li, Mianzhi Wang, Yongxue Sun
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Viruses
• Subjects: T7-like phage; antibiotic resistance genes (ARG); potential packaging; phage-host interaction
• Online Access: https://www.mdpi.com/1999-4915/12/10/1060

The increase in antimicrobial resistance is a threat to both human and animal health. The transfer of antibiotic resistance genes (ARG) via plasmids has been studied in detail whereas the contribution of bacteriophage-mediated ARG transmission is relatively little explored. We isolated and characterized two T7-like lytic bacteriophages that infected multidrug-resistant <i>Escherichia coli</i> hosts. The morphology and genomic analysis indicated that both phage HZP2 and HZ2R8 were evolutionarily related and their genomes did not encode ARGs. However, ARG-like raw reads were detected in offspring sequencing data with a different abundance level implying that potential ARG packaging had occurred. PCR results demonstrated that six fragments of genes (<i>qnrS</i>, <i>cmlA</i>, <i>tetM</i>, <i>bla_TEM</i>, <i>sul3</i>, <i>mcr-1</i>) were potentially packaged by phage HZP2 and four (<i>qnrS</i>, <i>cmlA</i>, <i>bla_TEM</i>, <i>mcr-1</i>) by phage HZ2R8. Further quantitative results showed that ARG abundance hierarchies were similar. The gene <i>bla_TEM</i> was the most abundant (up to 1.38 × 10⁷ copies/mL) whereas <i>cmlA</i> and <i>qnrS</i> were the least. Moreover, the clinically important <i>mcr-1</i> gene was the second most abundant ARG indicating a possibility for spread through generalized transduction. Together, our results indicated that these structurally similar phage possessed similar characteristics and potential packaging during phage-host interaction displayed an ARG preference rather than occurring randomly.