The aim of our investigation was to verify whether phage therapy (PT) can induce antiphage antibodies. The antiphage activity was determined in sera from 122 patients from the Phage Therapy Unit in Wrocław with bacterial infections before and during PT, and in sera from 30 healthy volunteers using a neutralization test. Furthermore, levels of antiphage antibodies were investigated in sera of 19 patients receiving staphylococcal phages and sera of 20 healthy volunteers using enzyme-linked immunosorbent assay. The phages were administered orally, locally, orally/locally, intrarectally, or orally/intrarectally. The rate of phage inactivation (K) estimated the level of phages' neutralization by human sera. Low K rates were found in sera of healthy volunteers (K ≤ 1.73). Low K rates were detected before PT (K ≤ 1.64). High antiphage activity of sera K > 18 was observed in 12.3% of examined patients (n = 15) treated with phages locally (n = 13) or locally/orally (n = 2) from 15 to 60 days of PT. High K rates were found in patients treated with some Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis phages. Low K rates were observed during PT in sera of patients using phages orally (K ≤ 1.04). Increased inactivation of phages by sera of patients receiving PT decreased after therapy. These results suggest that the antiphage activity in patients' sera depends on the route of phage administration and phage type. The induction of antiphage activity of sera during or after PT does not exclude a favorable result of PT.

Background: Members of the genusKlebsiellaare among the leading microbial pathogens associated with nosocomial infection. The increased incidence of antimicrobial resistance in these species has propelled the need for alternate/combination therapeutic regimens to aid clinical treatment. Bacteriophage therapy forms one of these alternate strategies.Methods: Electron microscopy, burst size, host range, sensitivity of phage particles to temperature, chloroform, pH, and restriction digestion of phage DNA were used to characterizeKlebsiellaphages.Results and conclusions: Of the 32 isolated phages eight belonged to the familyMyoviridae, eight to theSiphoviridaewhilst the remaining 16 belonged to thePodoviridae. The host range of these phages was characterised against 254 clinicalEnterobacteriaceaestrains including multidrug resistantKlebsiellaisolates producing extended-spectrum beta-lactamases (ESBLs). Based on their lytic potential, six of the phages were further characterised for burst size, physicochemical properties and sensitivity to restriction endonuclease digestion. In addition, five were fully sequenced. Multiple phage-encoded host resistance mechanisms were identified. TheSiphoviridaephage genomes (KP16 and KP36) contained low numbers of host restriction sites similar to the strategy found in T7-like phages (KP32). In addition, phage KP36 encoded its own DNA adenine methyltransferase. The φKMV-like KP34 phage was sensitive to all endonucleases used in this study. Dam methylation of KP34 DNA was detected although this was in the absence of an identifiable phage encoded methyltransferase. TheMyoviridaephages KP15 and KP27 both carried Dam and Dcm methyltransferase genes and other anti-restriction mechanisms elucidated in previous studies. No other anti-restriction mechanisms were found, e.g. atypical nucleotides (hmC or glucosyl hmC), althoughMyoviridaephage KP27 encodes an unknown anti-restriction mechanism that needs further investigation.

Bacteriophages (phages), discovered 100 years ago, are able to infect and destroy only bacterial cells. In the current crisis of antibiotic efficacy, phage therapy is considered as a supplementary or even alternative therapeutic approach. Evolution of multidrug-resistant and pandrug-resistant bacterial strains poses a real threat, so it is extremely important to have the possibility to isolate new phages for therapeutic purposes. Our phage laboratory and therapy center has extensive experience with phage isolation, characterization and therapeutic application. In this article we present current progress in bacteriophages isolation and use for therapeutic purposes, our experience in this field and its practical implications for phage therapy. Herein we attempt to summarize the state of the art: properties of phages, the methods for their isolation, criteria of phage selection for therapeutic purposes and limitations of their use. Perspectives for the use of genetically engineered phages to specifically target bacterial virulence-associated genes are also briefly presented.

In this study, we investigated the humoral immune response (through the release of IgG, IgA, and IgM antiphage antibodies) to a staphylococcal phage cocktail in patients undergoing experimental phage therapy at the Phage Therapy Unit, Medical Center of the Ludwik Hirszfeld Institute of Immunology and Experimental Therapy in Wrocław, Poland. We also evaluated whether occurring antiphage antibodies had neutralizing properties towards applied phages (K rate). Among 20 examined patients receiving the MS-1 phage cocktail orally and/or locally, the majority did not show a noticeably higher level of antiphage antibodies in their sera during phage administration. Even in those individual cases with an increased immune response, mostly by induction of IgG and IgM, the presence of antiphage antibodies did not translate into unsatisfactory clinical results of phage therapy. On the other hand, a negative outcome of the treatment occurred in some patients who showed relatively weak production of antiphage antibodies before and during treatment. This may imply that possible induction of antiphage antibodies is not an obstacle to the implementation of phage therapy and support our assumption that the outcome of the phage treatment does not primarily depend on the appearance of antiphage antibodies in sera of patients during therapy. These conclusions are in line with our previous findings. The confirmation of this thesis is of great interest as regards the efficacy of phage therapy in humans.

Although phage discovery is an unquestionable merit of the English bacteriologist Frederick W. Twort and the Canadian–French microbiologist Félix d’Hérelle, who both discovered phages over 100 years ago, the Polish history of phage studies also dates back to those years. In contrast to the Western world, developing phage treatment in Poland has never been abandoned despite the country’s tense history marked by the Second World War (WWII) and the communism era. Today, Poland takes a prominent and remarkable place in the phage research area. Furthermore, established in 2005, the Phage Therapy Unit at the Hirszfeld Institute of Immunology and Experimental Therapy in Wrocław, the first such center within European borders, has quickly become a model for other centers in the world facing the issue of widespread antibiotic resistance. This article constitutes an attempt to fill the gap in the scientific literature by providing a comprehensive summary of the long tradition of phage research in Poland.

Aim: The aim was to study the association between the phage neutralization of patients’ sera and the clinical outcome of phage therapy (PT). Patients: About 62 patients with various bacterial infections receiving PT as well as 30 healthy volunteers were studied. Materials & methods: Antiphage activity of sera (AAS) was examined using the phage neutralization test of different types of phages before and during PT in relation to the route of phage administration and correlated with the results of PT. Results & conclusion: The analysis of the association between AAS level and clinical results indicated that the level of AAS is not correlated with the outcome of PT.