A New Approach for Phage Cocktail Design in the Example of Anti-Mastitis Solution.

The studies on phage therapy have shown an overall protective effect of phages in bacterial infections, thus providing an optimistic outlook on the future benefits of phage-based technologies for treating bacterial diseases. However, the therapeutic effect is highly affected by the proper composition of phage cocktails. The rational approach to the design of bacteriophage cocktails, which is the subject of this study, allowed for development of an effective anti-mastitis solution, composed of virulent bacteriophages acting on Escherichia coli and Staphylococcus aureus. Based on the in-depth bioinformatic characterization of bacteriophages and their in vitro evaluation, the cocktail of five phages against E. coli and three against S. aureus strains was composed. Its testing in the milk model experiment revealed a reduction in the number of S. aureus of 45% and 30% for E. coli strains, and in the study of biofilm prevention, it demonstrated 99% inhibition of biofilm formation for all tested S. aureus strains and a minimum of 50% for 50% of E. coli strains. Such insights justify the need for rational design of cocktails for phage therapy and indicate the potential of the developed cocktail in the treatment of diseased animals, but this requires further investigations to evaluate its in vivo efficacy.

Novel multiplex-PCR test for Escherichia coli detection.

Escherichia coli is a diverse and ubiquitous strain of both commensal and pathogenic bacteria. In this study, we propose the use of multiplex polymerase chain reaction (PCR), using amplification of three genes (cydA, lacY, and ydiV), as a method for determining the affiliation of the tested strains to the E. coli species. The novelty of the method lies in the small number of steps needed to perform the diagnosis and, consequently, in the small amount of time needed to obtain it. This method, like any other, has some limitations, but its advantage is fast, cheap, and reliable identification of the presence of E. coli. Sequences of the indicated genes from 1,171 complete E. coli genomes in the NCBI database were used to prepare the primers. The developed multiplex PCR was tested on 47,370 different Enterobacteriaceae genomes using in silico PCR. The sensitivity and specificity of the developed test were 95.76% and 99.49%, respectively. Wet laboratory analyses confirmed the high specificity, repeatability, reproducibility, and reliability of the proposed test. Because of the detection of three genes, this method is very cost and labor-effective, yet still highly accurate, specific, and sensitive in comparison to similar methods. IMPORTANCE: Detection of E. coli from environmental or clinical samples is important due to the common occurrence of this species of bacteria in all human and animal environments. As commonly known, these bacteria strains can be commensal and pathogenic, causing numerous infections of clinical importance, including infections of the digestive system, urinary, respiratory, and even meninges, particularly dangerous for newborns. The developed multiplex polymerase chain reaction test, confirming the presence of E. coli in samples, can be used in many laboratories. The test provides new opportunities for quick and cheap analyses, detecting E. coli using only three pairs of primers (analysis of the presence of three genes) responsible for metabolism and distinguishing E. coli from other pathogens from the Enterobacteriaceae family. Compared to other tests previously described in the literature, our method is characterized by high specificity and sensitivity.

RT-qPCR-based tests for SARS-CoV-2 detection in pooled saliva samples for massive population screening to monitor epidemics.

Swab, RT-qPCR tests remain the gold standard of diagnostics of SARS-CoV-2 infections. These tests are costly and have limited throughput. We developed a 3-gene, seminested RT-qPCR test with SYBR green-based detection designed to be oversensitive rather than overspecific for high-throughput diagnostics of populations. This two-tier approach depends on decentralized self-collection of saliva samples, pooling, 1st-tier testing with highly sensitive screening test and subsequent 2nd-tier testing of individual samples from positive pools with the IVD test. The screening test was able to detect five copies of the viral genome in 10 µl of isolated RNA with 50% probability and 18.8 copies with 95% probability and reached Ct values that were highly linearly RNA concentration-dependent. In the side-by-side comparison, the screening test attained slightly better results than the commercially available IVD-certified RT-qPCR diagnostic test DiaPlexQ (100% specificity and 89.8% sensitivity vs. 100% and 73.5%, respectively). Testing of 1475 individual clinical samples pooled in 374 pools of four revealed 0.8% false positive pools and no false negative pools. In weekly prophylactic testing of 113 people within 6 months, a two-tier testing approach enabled the detection of 18 infected individuals, including several asymptomatic individuals, with substantially lower cost than individual RT-PCR testing.

Complete genome sequences of Aeromonas and Pseudomonas phages as a supportive tool for development of antibacterial treatment in aquaculture.

BACKGROUND: Aquaculture is the fastest growing sector of food production worldwide. However, one of the major reasons limiting its effectiveness are infectious diseases among aquatic organisms resulting in vast economic losses. Fighting such infections with chemotherapy is normally used as a rapid and effective treatment. The rise of antibiotic resistance, however, is limiting the efficacy of antibiotics and creates environmental and human safety concerns due to their massive application in the aquatic environment. Bacteriophages are an alternative solution that could be considered in order to protect fish against pathogens while minimizing the side-effects for the environment and humans. Bacteriophages kill bacteria via different mechanisms than antibiotics, and so fit nicely into the 'novel mode of action' concept desired for all new antibacterial agents. METHODS: The bacteriophages were isolated from sewage water and characterized by RFLP, spectrum of specificity, transmission electron microscopy (TEM) and sequencing (WGS). Bioinformatics analysis of genomic data enables an in-depth characterization of phages and the choice of phages. This allows an optimised choice of phage for therapy, excluding those with toxin genes, virulence factor genes, and genes responsible for lysogeny. RESULTS: In this study, we isolated eleven new bacteriophages: seven infecting Aeromonas and four infecting Pseudomonas, which significantly increases the genomic information of Aeromonas and Pseudomonas phages. Bioinformatics analysis of genomic data, assessing the likelihood of these phages to enter the lysogenic cycle with experimental data on their specificity towards large number of bacterial field isolates representing different locations. CONCLUSIONS: From 11 newly isolated bacteriophages only 6 (25AhydR2PP, 50AhydR13PP, 60AhydR15PP, 22PfluR64PP, 67PfluR64PP, 71PfluR64PP) have a potential to be used in phage therapy due to confirmed lytic lifestyle and absence of virulence or resistance genes.