Characterization of four virulent Klebsiella pneumoniae bacteriophages, and evaluation of their potential use in complex phage preparation

Background Nowadays, hundreds of thousands of deaths per year are caused by antibiotic resistant nosocomial infections and the prognosis for future years is much worse, as evidenced by modern research. Bacteria of the Klebsiella genus are one of the main pathogens that cause nosocomial infections. Among the many antimicrobials offered to replace or supplement traditional antibiotics, bacteriophages are promising candidates. Methods This article presents microbiological, physicochemical and genomic characterization of 4 virulent bacteriophages belonging to Siphoviridae, Myoviridae and Podoviridae families. Phages were studied by electron microscopy; their host range, lytic activity, adsorption rate, burst size, latent period, frequency of phage-resistant forms generation, lysis dynamics and sensitivity of phage particles to temperature and pH were identified; genomes of all 4 bacteriophages were studied by restriction digestion and complete genome sequence. Results Studied phages showed wide host range and high stability at different temperature and pH values. In contrast with single phages, a cocktail of bacteriophages lysed all studied bacterial strains, moreover, no cases of the emergence of phage-resistant bacterial colonies were detected. Genomic data proved that isolated viruses do not carry antibiotic resistance, virulence or lysogenic genes. Three out of four bacteriophages encode polysaccharide depolymerases, which are involved in the degradation of biofilms and capsules. Conclusions The bacteriophages studied in this work are promising for further in vivo studies and might be used in phage therapy as part of a complex therapeutic and prophylactic phage preparation. The conducted studies showed that the complex preparation is more effective than individual phages. The use of the complex phage cocktail allows to extend the lytic spectrum, and significantly reduces the possibility of phage-resistant forms generation.

Complete Genome Sequence of Escherichia-Infecting Phage CEC_KAZ_2018, Isolated from Soil

Avian pathogenic Escherichia coli (APEC) bacteria are one of the main problems of the poultry industry. An effective way to combat colibacillosis is to use a phage preparation that lyses the bacteria. Here, we report the isolation of an E. coli-infecting phage, CEC_KAZ_2018, isolated from soil.

Efficacy of Lytic Bacteriophage Preparation in Reducing Salmonella In Vitro, on Turkey Breast Cutlets, and on Ground Turkey†‡

The efficacy of the recently approved Salmonella lytic bacteriophage preparation (SalmoFresh) in reducing Salmonella enterica serotype Heidelberg on turkey breast cutlets and ground turkey was evaluated. In a broth model assay, the phage preparation completely inhibited the growth of four S. enterica serotypes (Salmonella Enteritidis, Salmonella Heidelberg, Salmonella Kentucky, and Salmonella Typhimurium) at 37°C at a multiplicity of infection of 10,000 PFU/CFU. At 4°C in 0.1% peptone water (PW), phage treatment at a multiplicity of infection of 10,000 resulted in ca. 4.0-log CFU/ml reductions of Salmonella Enteritidis, Salmonella Heidelberg, and Salmonella Typhimurium. When raw turkey breast cutlets inoculated with Salmonella Heidelberg (~103 CFU/g) were treated with phage preparation (107 PFU/g) and stored at 4°C, the phage treatment caused reductions of 0.8, 0.6, and 1.3 log CFU/g (P ≤ 0.05) of Salmonella Heidelberg on day 0, 1, and 7, respectively, compared with the counts in the control. However, no significant reduction of Salmonella Heidelberg (P > 0.05) was observed in ground turkey when turkey meat pieces inoculated with Salmonella Heidelberg were surface treated with phage preparation (107 PFU/g) before grinding. These findings indicate that the bacteriophage preparation was effective in reducing Salmonella on turkey breast cutlets as a surface treatment but did not cause any reduction of Salmonella Heidelberg in ground turkey.

Bacteriophage Administration Reduces the Concentration ofListeria monocytogenesin the Gastrointestinal Tract and Its Translocation to Spleen and Liver in Experimentally Infected Mice

To investigate the efficacy of phage supplementation in reducing pathogen numbers, mice were treated via oral gavage with aListeria monocytogenesphage preparation (designated ListShield) before being orally infected withL. monocytogenes. The concentrations ofL. monocytogenesin the liver, spleen, and intestines were significantly lower (P<.05) in the phage-treated than in the control mice. Phage and antibiotic treatments were similarly effective in reducing the levels ofL. monocytogenesin the internal organs of the infected mice. However, the significant weight loss detected in the control and antibiotic-treated groups was not observed in the infected, ListShield-treated mice. Long-term (90 days), biweekly treatment of uninfected mice with ListShield did not elicit detectable changes in the microbiota of their large intestines or deleterious changes in their health. Our data support the potential feasibility of using bacteriophages to control proliferation ofL. monocytogenesin mice without affecting commensal microbiota composition.