Antibacterial Potential of Non-Tailed Icosahedral Phages Alone and in Combination with Antibiotics.

Non-tailed icosahedral phages belonging to families Fiersviridae (phages MS2 and Qbeta), Tectiviridae (PRD1) and Microviridae (phiX174) have not been considered in detail so far as potential antibacterial agents. The aim of the study was to examine various aspects of the applicability of these phages as antibacterial agents. Antibacterial potential of four phages was investigated via bacterial growth and biofilm formation inhibition, lytic spectra determination, and phage safety examination. The phage phiX174 was combined with different classes of antibiotics to evaluate potential synergistic interactions. In addition, the incidence of phiX174-insensitive mutants was analyzed. The results showed that only phiX174 out of four phages tested against their corresponding hosts inhibited bacterial growth for > 90% at different multiplicity of infection and that only this phage considerably prevented biofilm formation. Although all phages show the absence of potentially undesirable genes, they also have extremely narrow lytic spectra. The synergism was determined between phage phiX174 and ceftazidime, ceftriaxone, ciprofloxacin, macrolides, and chloramphenicol. It was shown that the simultaneous application of agents is more effective than successive treatment, where one agent is applied first. The analysis of the appearance of phiX174 bacteriophage-insensitive mutants showed that mutations occur with a frequency of 10-3. The examined non-tailed phages have a limited potential for use as antibacterial agents, primarily due to a very narrow lytic spectrum and the high frequency of resistant mutants appearance, but Microviridae can be considered in the future as biocontrol agents against susceptible strains of E. coli in combinations with conventional antimicrobial agents.

An Optimized Checkerboard Method for Phage-Antibiotic Synergy Detection.

Phage-antibiotic synergy is a promising therapeutic strategy, but there is no reliable method for synergism estimation. Although the time-kill curve assay is a gold standard, the method is not appropriate for fast and extensive screening of the synergy. The aim is to optimize the checkerboard method to determine phage-chemical agent interactions, to check its applicability by the time-kill curve method, and to examine whether the synergy can be obtained with both simultaneous and successive applications of these agents. In addition, the aim is to determine interactions of the Pseudomonas phage JG024 with ciprofloxacin, gentamicin, or ceftriaxone, as well as the Staphylococcus phage MSA6 and SES43300 with ciprofloxacin, gentamicin, and oxacillin. The results show that the optimized checkerboard method is reliable and that results correspond to those obtained by the time-kill curve. The synergy is detected with the phage JG024 and ciprofloxacin or ceftriaxone against Pseudomonas aeruginosa, and the phage SES43300 with ciprofloxacin against MRSA. The synergy was obtained after simultaneous applications, and in the case of P. aeruginosa, after application of the second agent with delay of one hour, indicating that simultaneous application is the best mode of synergy exploitation for therapy. The checkerboard method can be used for thorough clinical studies on synergy and in the future for personalized therapy when infections are caused by multiple resistant bacteria.

Virtual histology study of atherosclerotic plaque composition in patients with stable angina and acute phase of acute coronary syndromes without ST segment elevation.

INTRODUCTION: Rupture of vulnerable atherosclerotic plaques is the cause of most acute coronary syndromes (ACS). Postmortem studies which compared stable coronary lesions and atherosclerotic plaques in patients who have died because of ACS indicated high lipid-core content as one of the major determinants of plaque vulnerability. OBJECTIVE: Our primary goal was to assess the potential relations of plaque composition determined by IVUS-VH (Intravascular Ultrasound -Virtual Histology) in patients with stable angina and subjects in acute phase of ACS without ST segment elevation. METHODS: The study comprised of 40 patients who underwent preintervention IVUS examination.Tissue maps were reconstructed from radio frequency data using IVUS-VH software. RESULTS: We analyzed 53 lesions in 40 patients. Stable angina was diagnosed in 24 patients (29 lesions), while acute phase of ACS without ST elevation was diagnosed in 16 patients (24 lesions). In the patients in acute phase of ACS without ST segment elevation IVUS-VH examination showed a significantly larger area of the necrotic core at the site of minimal lumen area and a larger mean of the necrotic core volume in the entire lesion comparing to stable angina subjects (1.84+/-0.90 mm2 vs. 0.96+/-0.69 mm2; p<0.001 and 20.94+/-15.79 mm3 vs. 11.54+/-14.15 mm3; p<0.05 respectively). CONCLUSION: IVUS-VH detected that the necrotic core was significantly larger in atherosclerotic lesions in patients in acute phase of ACS without ST elevation comparing to the stable angina subjects and that it could be considered as a marker of plaque vulnerability.