Bacteriophages against human and plant pathogens

The bacterial resistance to antibiotics gained very high relevance in the 21st Century, as to justify the forecasting of a "post-antibiotic era". The concerns due to resistant bacteria involves both the human/veterinary clinic and the environmental health. To limit both the spread of antibiotics in the environment and the consequent selective pressure which favours exchange and selection of resistance genes, alternative solution must be found: to this aim, the use of bacteriophages has gained a renewed relevance. Virulent bacteriophages against bacteria of both clinical and agricultural interest have been collected in environmental samples of different origin. Our research led to the isolation and characterization of bacteriophages active against Pseudomonas syringae pathovar actinidiae and Klebsiella pneumoniae. Some of the preliminary results of Klebsiella were rewarded on the occasion of the Italian Society of Microbiology Congress (SIMB 2014, Turin, Italy) and of the Bacteriophage 2016 Conference (January 19-21, London, UK). These researches are performed in collaboration with Marco Maria D'Andrea, Gian Maria Rossolini (University of Florence) and Domenico Frezza, (retired, University of Rome Tor Vergata).

Ciacci N., D’Andrea M.M., Marmo P., Demattè E., Amisano F., Di Pilato V., Fraziano M., Lupetti P., Rossolini G.M. and Thaller M.C. (2018) - CHARACTERIZATION OF VB_KPN_F48, A NEWLY DISCOVERED LYTIC BACTERIOPHAGE FOR KLEBSIELLA PNEUMONIAE OF SEQUENCE TYPE 101. Viruses, 10(9): 482-497.

Resistance to carbapenems in Enterobacteriaceae, including Klebsiella pneumoniae, represents a major clinical problem given the lack of effective alternative antibiotics. Bacteriophages could provide a valuable tool to control the dissemination of antibiotic resistant isolates, for the decolonization of colonized individuals and for treatment purposes. In this work, we have characterized a lytic bacteriophage, named vB_Kpn_F48, specific for K. pneumoniaeisolates belonging to clonal group 101. Phage vB_Kpn_F48 was classified as a member of Myoviridae, order Caudovirales, on the basis of transmission electron microscopy analysis. Physiological characterization demonstrated that vB_Kpn_F48 showed a narrow host range, a short latent period, a low burst size and it is highly stable to both temperature and pH variations. High throughput sequencing and bioinformatics analysis revealed that the phage is characterized by a 171 Kb dsDNA genome that lacks genes undesirable for a therapeutic perspective such integrases, antibiotic resistance genes and toxin encoding genes. Phylogenetic analysis suggests that vB_Kpn_F48 is a T4-like bacteriophage which belongs to a novel genus within the Tevenvirinae subfamily, which we tentatively named “F48virus”. Considering the narrow host range, the genomic features and overall physiological parameters phage vB_Kpn_F48 could be a promising candidate to be used alone or in cocktails for phage therapy applications.

D'Andrea M., Marmo P., Henrici De Angelis L., Palmieri M., Ciacci N., Di Lallo G., Demattè E., Vannuccini E., Lupetti P., Rossolini G.M., Thaller M.C. (2017) - ΦBO1E, A NEWLY DISCOVERED LYTIC BACTERIOPHAGE TARGETING CARBAPENEMASE-PRODUCING KLEBSIELLA PNEUMONIAE OF THE PANDEMIC CLONAL GROUP 258 CLADE II LINEAGE. Scientific Reports 7(1): 2614. DOI: 10.1038/s41598-017-02788-9

 The pandemic dissemination of KPC carbapenemase-producing Klebsiella pneumoniae (KPC-KP) represents a major public health problem, given their extensive multidrug resistance profiles and primary role in causing healthcare-associated infections. This phenomenon has largely been contributed by strains of Clonal Group (CG) 258, mostly of clade II, which in some areas represent the majority of KPC-KP isolates. Here we have characterized a newly discovered lytic Podoviridae, named φBO1E, targeting KPC-KP strains of clade II lineage of CG258. Genomic sequencing revealed that φBO1E belongs to the Kp34virus genus (87% nucleotide identity to vB_KpnP_SU552A). ΦBO1E was stable over a broad pH and temperature range, exhibited strict specificity for K. pneumoniae strains of clade II of CG258, and was unable to establish lysogeny. In a Galleria mellonella infection model, φBO1E was able to protect larvae from death following infection with KPC-KP strains of clade II of CG258, including one colistin resistant strain characterized by a hypermucoviscous phenotype. To our best knowledge φBO1E is the first characterized lytic phage targeting K. pneumoniae strains of this pandemic clonal lineage. As such, it could be of potential interest to develop new agents for treatment of KPC-KP infections and for decolonization of subjects chronically colonized by these resistant superbugs.