Sub-lethal treatment of Escherichia coli strain B23 with either β-lactam or Aminoglycoside Antibiotics May Delay T7 Bacteriophage-mediated Cell Lysis

SUMMARY With increasing rates of antibiotic resistance, there is renewed interest in the utilization of bacteriophages to treat pathogenic bacteria. However, the complex interplay between bacteria, phage, and antibiotic treatments is not well understood. A recent study by Hardman et al. found that treatment of E. coli with sub-lethal concentrations of the aminoglycoside antibiotics gentamycin and kanamycin lead to an increase in T7 phage resistance (7-10). We propose the idea of cross-protection, or a generalized stress response, as a possible framework for explaining and interpreting their results, in which case cells are able to produce a response induced by a primary stressor (sub-MIC antibiotics) and exhibit enhanced tolerance to a secondary stressor (T7 phage infection). We used a real-time cell lysis assay to investigate the effects of sublethal concentrations of antibiotics on phage resistance in Escherichia coli B23. We found that both beta-lactam and aminoglycoside increased resistance to lysis by T7 phage. This result suggests that sublethal concentration of antibiotics may decrease the rate of T7 replication and that this phenomenon is not unique to one class of antibiotics. We suggest that delayed T7-mediated lysis of Escherichia coli B23 may be due to upregulation of a general stress response following treatment with sublethal concentrations of antibiotics.