Increasing multidrug resistance has led to renewed interest in phage-based therapy. A combination of the bacteriophages and antibiotics presents a promising approach enhancing the phage therapy effectiveness. First, phage candidates for therapy should be deeply characterized. Here we characterize the bacteriophage vB_AbaP_AGC01 that poses antibacterial activity against clinical Acinetobacter baumannii strains. Moreover, besides genomic and phenotypic analysis our study aims to analyze phage–antibiotic combination effectiveness with the use of ex vivo and in vivo models. The phage AGC01 efficiently adsorbs to A. baumannii cells and possesses a bacteriolytic lifecycle resulting in high production of progeny phages (317 ± 20 PFU × cell−1). The broad host range (50.27%, 93 out of 185 strains) against A. baumannii isolates and the inability of AGC01 to infect other bacterial species show its high specificity. Genomic analysis revealed a high similarity of the AGC01 genome sequence with that of the Friunavirus genus from a subfamily of Autographivirinae. The AGC01 is able to significantly reduce the A. baumannii cell count in a human heat-inactivated plasma blood model (HIP-B), both alone and in combination with antibiotics (gentamicin (GEN), ciprofloxacin (CIP), and meropenem (MER)). The synergistic action was observed when a combination of phage treatment with CIP or MER was used. The antimicrobial activity of AGC01 and phage-antibiotic combinations was confirmed using an in vivo larva model. This study shows the greatest increase in survival of G. mellonella larvae when the combination of phage (MOI = 1) and MER was used, which increased larval survival from 35% to 77%. Hence, AGC01 represents a novel candidate for phage therapy. Additionally, our study suggests that phages and antibiotics can act synergistically for greater antimicrobial effect when used as combination therapy.
The development of antimicrobial resistance has become a global concern. One approach to overcome the problem of drug resistance is the application of bacteriophages. This study aimed at characterizing three phages isolated from sewage, which show lytic activity against clinical isolates of multidrug-resistant Staphylococcus aureus. Morphology, genetics and biological properties, including host range, adsorption rate, latent time, phage burst size and lysis profiles, were studied in all three phages. As analyzed by transmission electron microscopy (TEM), phages vB_SauM-A, vB_SauM-C, vB_SauM-D have a myovirion morphology. One of the tested phages, vB_SauM-A, has relatively rapid adsorption (86% in 17.5 min), short latent period (25 min) and extremely large burst size (~500 plaque-forming units (PFU) per infected cell). The genomic analysis revealed that vB_SauM-A, vB_SauM-C, vB_SauM-D possess large genomes (vB_SauM-A 139,031 bp, vB_SauM-C 140,086 bp, vB_SauM-D 139,088 bp) with low G+C content (~30.4%) and are very closely related to the phage K (95–97% similarity). The isolated bacteriophages demonstrate broad host range against MDR S. aureus strains, high lytic activity corresponding to strictly virulent life cycle, suggesting their potential to treat S. aureus infections.
The ability to form biofilm is an important virulence factor of many microorganisms. Infections involving biofilms account for approx. 65% of all human infections. Biofilms may develop on intravascular catheters or implanted devices such as prosthetic heart valves. Implanted devices are covered by biofilm and become reservoirs of microorganisms which can be a cause of persistent infections (endocarditis, deep tissue abscesses, septic arthritis, and osteomyelitis). Treatment of infections caused by biofilm-growing cells is linked to a high risk of failure due to an extreme resistance to antimicrobial agents and increased capacity to evade the immune responses. A large number of biofilm-associated infections involve Staphylococcus aureus. Treatment of staphylococcal infections is a great challenge for clinicians because of the presence of various mechanisms of resistance to antibiotics in S. aureus, for example methicillin resistance and biofilm production. Therapeutic difficulties related with antibiotic-resistant bacteria and limitations in research on new antimicrobials were the reasons that nearly 100 years after discovery, bacteriophages caught the attention of scientists around the world as a new therapeutic option for bacterial infections. Numerous in vitro studies on S. aureus strains showed that phages can both prevent biofilm formation and contribute to the elimination of bacteria from the mature biofilm structure. The major role in biofilm eradication play depolymerases produced by some phages which facilitate their penetration into the inner layers of biofilm by disturbing the biofilm structure. This leads to the conclusion that bacteriophages treatment might become a new strategy in the prevention and eradication of infectious bacterial biofilms, including these formed by S. aureus.
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