Genetic Analysis and Characterization of a Bacteriophage ØCJ19 Active against Enterotoxigenic Escherichia coli

Isolation, characterization, molecular analysis and application of bacteriophage DW-EC to control Enterotoxigenic Escherichia coli on various foods

Among food preservation methods, bacteriophage treatment can be a viable alternative method to overcome the drawbacks of traditional approaches. Bacteriophages are naturally occurring viruses that are highly specific to their hosts and have the capability to lyse bacterial cells, making them useful as biopreservation agents. This study aims to characterize and determine the application of bacteriophage isolated from Indonesian traditional Ready-to-Eat (RTE) food to control Enterotoxigenic Escherichia coli (ETEC) population in various foods. Phage DW-EC isolated from Indonesian traditional RTE food called dawet with ETEC as its host showed a positive result by the formation of plaques (clear zone) in the bacterial host lawn. Transmission electron microscopy (TEM) results also showed that DW-EC can be suspected to belong to the Myoviridae family. Molecular characterization and bioinformatic analysis showed that DW-EC exhibited characteristics as promising biocontrol agents in food samples. Genes related to the lytic cycle, such as lysozyme and tail fiber assembly protein, were annotated. There were also no signs of lysogenic genes among the annotation results. The resulting PHACTS data also indicated that DW-EC was leaning toward being exclusively lytic. DW-EC significantly reduced the ETEC population (P ≤ 0.05) in various food samples after two different incubation times (1 day and 6 days) in chicken meat (80.93%; 87.29%), fish meat (63.78%; 87.89%), cucumber (61.42%; 71.88%), tomato (56.24%; 74.51%), and lettuce (46.88%; 43.38%).

Genomic characterization of bacteriophage BI-EHEC infecting strains of Enterohemorrhagic Escherichia coli

OBJECTIVE

The aims of this research were to determine the genomic properties of BI-EHEC to control Enterohemorrhagic Escherichia coli (EHEC), which was isolated from previous study. Genomic analysis of this phage is essential for the assessment of this bacteriophage for further application as food preservatives.

RESULTS

Genome of BI-EHEC was successfully annotated using multiPhATE2. Structural and lytic cycle-related proteins such as head, tail, capsid, and lysozyme (lysin) were annotated. The phylogenetic tree of tail fiber protein and BRIG results showed that BI-EHEC was similar to phages of the same host in the bacteriophage genome database. There were no indications of virulence properties, antibiotic resistance genes and lysogenic protein among annotated genes which implied BI-EHEC followed a lytic life cycle. PHACTS analysis was done to confirm this notion further and yielded a lytic cycle result. Further analysis using CARD found that BI-EHEC does not contain residual ARGs per recommended parameter. Furthermore, BI-EHEC confirmed as lytic bacteriophage, making it a good candidate for biocontrol agent.

Improvement of the detection efficiency of 3M™ molecular detection system for Campylobacter in poultry using nitrogen-doped carbon nanodots

This study was performed to examine whether the use of nitrogen-doped carbon nanodots (N-CNDs) can improve the detection sensitivity of the 3 M™ molecular detection system (MDS) for Campylobacter. N-CNDs were added to a Campylobacter enrichment broth (CEB) at concentrations of 5 and 10 mg/mL (NCEB-5 and NCEB-10, respectively). Campylobacter coli, C. jejuni, and C. lari were inoculated into the broths. The broth cultures were then irradiated with light-emitting diode (LED) at 425 nm for 1 h and incubated at 42 °C for 6 h, and then grown on modified charcoal cefoperazone deoxycholate agar (mCCDA). The detection rates of the MDS and a conventional method (plating an enriched sample on mCCDA and analyzing a colony on mCCDA with PCR) for Campylobacter in chicken and duck carcasses were compared. The detection rates from the MDS were compared after enrichment in CEB and NCEB-5 at 3, 5, 6, 7, 9, 12, and 24 h. When 5 mg/mL of N-CNDs was added to the CEB followed by irradiation at 425 nm, growth of the Campylobacter was accelerated. In addition, the qualitative test was more sensitive in the MDS than in the conventional method, and the detection time was shortened in CEB enriched with N-CNDs. These results indicate that adding N-CNDs to CEB can improve the detection efficiency of MDS.