The formation of phage-resistant Proteus mirabilis strains

During September 15th - 17th our Research & Development team participated in the XXIX National Congress of the Polish Society of Microbiologists, which took place in Warsaw, Poland. Our colleague Nikol Wolińska presented the results of one of the recently conducted studies on The formation of phage-resistant Proteus mirabilis strains.

Due to the growing antibiotic resistance of pathogenic bacteria, there is a great potential in the application of phage therapy, which is based on combating bacterial infections through specific bacteriophages. Phage-resistant bacterial strains may develop during the phage therapy. This phenomenon can both contribute to reducing the therapy effectiveness, while have a positive impact because bacteria become resistant to phages, they can simultaneously lose their pathological effect on the organism. Therefore is the importance of studying the phage-resistance while composing bacteriophage preparations. The aim of this study was to analyze the formation of Proteus mirabilis strains resistant to specific bacteriophages and the identification of the molecular basis of resistance. 

Three uropathogenic strains of P. Mirabilis and 3 specific virulent bacteriophages were used in the study. As a result of the immunization process, from 2 to 12 potentially resistant variants of bacteria were obtained from individually tested P. Mirabilis strains. The frequency of potentially resistant variants emergence ranged from 1.53 to 6.80x10-6. Phage-sensitivity analysis of the obtained variants showed that only some of them were resistant to a given phage - these variants were considered resistant mutants. 

The bioinformatic analysis of the genome sequence of 6 resistant mutants showed:

- a change in the reading frame resulting in the formation of a non-functional glucosyltransferase enzyme, 

- a mutation in the gene encoding heptosyltransferase,

- a mutation in the gene encoding ADP-heptose synthetase.

The bioinformatic analysis of the genomes of mutants resistant to all analyzed bacteriophages showed that the lipopolysaccharide core is the secondary receptor for the above-mentioned bacteriophages. More precisely, it is the region between heptose and glucose, as mutations in the regions coding these enzymes resulted in the mutants resistance to selected bacteriophages. In one of the resistant mutants, there was detected an additional mutation in the coding region of the fatty acid transporter resulting in the formation of a non-functional protein.

The conclusion:

The presence of the mutation mentioned above in a strain resistant to only one bacteriophage allows the conclusion that it is the fatty acid transporter that is the primary receptor for this bacteriophage.

The obtained results enrich the knowledge about bacterial phago-resistance and indicate the importance of the research as for the appropriate selection of bacteriophages intended for therapy preparations.

The Authors: Nikol Wolińska, Rafał Matusiak, Dominika Wąsik, Arkadiusz Guziński, Agnieszka Maszewska

Proteon Pharmaceuticals is a leader in bacteriophage (phage) technology for livestock farming and aquaculture. Our mission is to eliminate the need for unnecessary antibiotic use, reducing the risk of antimicrobial resistance (AMR), as well as to increase the sustainability of protein production through the reduction of waste and improvement of on-farm efficiency. Our products function by modulating the microbiome enabling prophylactic health. We have created a precision phage product development platform using -omics technologies, molecular biology, bioinformatics, and artificial intelligence (AI) to create effective, reliable, and safe antibacterial solutions for animal and human health.