Weirdo19ES is a novel singleton mycobacteriophage that selects for glycolipid deficient phage-resistant M. smegmatis mutants

Alternatives to antibiotics in veterinary medicine: considerations for the management of Johne's disease

Antibiotic resistance has become a major health concern globally, with current predictions expecting deaths related to resistant infections to surpass those of cancer by 2050. Major efforts are being undertaken to develop derivative and novel alternatives to current antibiotic therapies in human medicine. What appears to be lacking however, are similar efforts into researching the application of those alternatives, such as (bacterio)phage therapy, in veterinary contexts. Agriculture is still undoubtedly the most prominent consumer of antibiotics, with up to 70% of annual antibiotic usage attributed to this sector, despite policies to reduce their use in food animals. This not only increases the risk of resistant infections spreading from farm to community but also the risk that animals may acquire species-specific infections that subvert treatment. While these diseases may not directly affect human welfare, they greatly affect the profit margin of industries reliant on livestock due to the cost of treatments and (more frequently) the losses associated with animal death. This means actively combatting animal infection not only benefits animal welfare but also global economies. In particular, targeting recurring or chronic conditions associated with certain livestock has the potential to greatly reduce financial losses. This can be achieved by developing novel diagnostics to quickly identify ill animals alongside the design of novel therapies. To explore this concept further, this review employs Johne's disease, a chronic gastroenteritis condition that affects ruminants, as a case study to exemplify the benefits of rapid diagnostics and effective treatment of chronic disease, with particular regard to the diagnostic and therapeutic potential of phage.

Characterization and Genomic Analysis of a Novel Lytic Phage DCp1 against Clostridium perfringens Biofilms

Clostridium perfringens (C. perfringens) is one of the foremost pathogens responsible for diarrhea in foals. As antibiotic resistance increases, phages that specifically lyse bacteria are of great interest to us with regard to C. perfringens. In this study, a novel C. perfringens phage DCp1 was isolated from the sewage of a donkey farm. Phage DCp1 had a non-contractile short tail (40 nm in length) and a regular icosahedral head (46 nm in diameter). Whole-genome sequencing indicated that phage DCp1 had a linear double-stranded DNA genome with a total length of 18,555 bp and a G + C content of 28.2%. A total of 25 ORFs were identified in the genome, 6 of which had been assigned to functional genes, others were annotated to encode hypothetical proteins. The genome of phage DCp1 lacked any tRNA, virulence gene, drug resistance gene, or lysogenic gene. Phylogenetic analysis indicated that phage DCp1 belonged to the family Guelinviridae, Susfortunavirus. Biofilm assay showed that phage DCp1 was effective in inhibiting the formation of C. perfringens D22 biofilms. Phage DCp1 could completely degrade the biofilm after 5 h of interaction. The current study provides some basic information for further research on phage DCp1 and its application.

Insertion Mutation of MSMEG_0392 Play an Important Role in Resistance of M. smegmatis to Mycobacteriophage SWU1

Purpose

Phage is a new choice for the treatment of multi-drug-resistant bacteria, and phage resistance is also an issue of concern. SWU1 is a mycobacteriophage, and the mechanism of its resistance remain poorly understood.

Methods

The mutant strains which were stably resistant to SWU1 were screened by transposon mutation library. The stage of phage resistance was observed by transmission electron microscope (TEM). The insertion site of transposon was identified by thermal asymmetric interlaced PCR (TAIL-PCR). The possible relationship between insertion site and phage resistance was verified by gene knockout technique. The fatty acid composition of bacterial cell wall was analyzed by Gas Chromatography-Mass Spectrometer (GC-MS). Through the amplification and sequencing of target genes and gene complement techniques to find the mechanism of SWU1 resistance.

Results

The transposon mutant M12 which was stably resistant to mycobacteriophage SWU1 was successfully screened. It was confirmed that resistance occurred in the adsorption stage of bacteriophage. It was verified that the insertion site of the transposon was located in the MSMEG_3705 gene, but after knocking out the gene in the wild type M. smegmatis mc2 155, the resistance of the knockout strain to SWU1 was not observed. Through the amplification and sequencing of the target gene MSMEG_0392, it was found that there was an adenine insertion mutation at position 817. After complementing MSMEG_0392 in M12, it was found that M12 returned to sensitivity to SWU1.

Conclusion

We confirmed that the resistance of M12 to SWU1 was related to the functional inactivation of MSMEG_0392 and this phenomenon may be caused by the change of cell wall of M. smegmatis.