Evaluation of Phage-Antibiotic Synergy (PAS) Against Biofilm Formed by Colistin-Resistant Klebsiella pneumoniae

The emergence of Antibiotic-Resistant Microbes (AMR) against last-resort antibiotics, including carbapenems, colistin, etc., is a pressing global concern. The dry pipeline of antibiotics necessitates the discovery of alternatives to counter AMR. Klebsiella pneumoniae is known for its MDR status and ability to form biofilm, posing additional challenges to antibiotic therapy. Bacteriophage therapy emerges as the most promising alternative to treat the growing antibiotic-resistant infections associated with biofilm. It will be very interesting if the synergic effect is examined between phages and antibiotics at subinhibitory concentrations. The novel phage ΦKpnBHU3 was isolated from the sewage water and characterized for host specificity and physiological stability (temperature and pH). The isolated phage, in combination with colistin in sub-MIC concentration, were further evaluated for eradication of planktonic and biofilm forms of K. pneumoniae in-vitro. Whole genome sequencing of phage ΦKpnBHU3 was performed for identification, evolutionary relationship, and bioinformatics analysis. This study showed that combining phage ΦKpnBHU3 (1 × 109 PFU/mL) with the sub-inhibitory concentration of colistin (12.2μg/mL) produced a synergistic antibacterial effect and successfully eradicated planktonic and biofilm forms of K. pneumoniae. While the phage-first therapy had excellent antibacterial synergy, simultaneous and antibiotic treatment resulted in limited antibacterial synergy. Phage-Antibiotic Synergy (PAS) based therapy has been suggested to eradicate the bacteria more efficiently and thus may lead to the relevance of those antibiotics which are being reported as ineffective. PAS may significantly reduce antibiotic usage, reducing selection pressure and thus restoring antibiotic activity. However, further research is required to comprehend the PAS’s molecular mechanisms and preclinical and clinical evaluation regarding efficacy and safety.