Characterization of a Coliphage AS1 isolated from sewage effluent in Pakistan

The role of identified and characterized bacteriophage ZCEC13 in controlling pathogenic and multidrug-resistant Escherichia coli in wastewater: in vitro study

The spread and development of Multi-Drug Resistant (MDR) bacteria in wastewater became beyond control and a global public health concern. The conventional disinfectants used in wastewater treatment methods have been becoming increasingly ineffective against a range of pathogenic and MDR bacteria. Bacteriophages are considered a novel approach to microbial control. Therefore, this study aims to explore the possibility of using phages against pathogenic and MDR Escherichia coli strains isolated from wastewater treatment plants. The wastewater samples were collected from two different treatment plants for E. coli isolation. The antibiotic sensitivity profile and occurrence of virulence and resistant genes were tested in 28 E. coli isolates. Phage ZCEC13 was selected based on its promising activity and host range to undergo identification and characterization. ZCEC13 was evaluated by transmission electron microscopy, genomic sequencing, in vitro lytic activity and tested for its stability under different conditions such as pH, Ultraviolet light exposure, and temperature. The results reported that ZCEC13 belongs to the Caudoviricetes class, with a high antibacterial dynamic. Phage ZCEC13 displayed high stability at different pH values ranging from 2 to 12, good tolerance to temperatures from -4 to 65°C, and high stability at UV exposure for 120 min. Respectively, the findings showed stability of the phage under several conditions and high efficiency in killing MDR bacteria isolated from the treatment plants. Further studies are encouraged to analyse the efficacy of phages as a microbial control agent in wastewater treatment plants.

Isolation and Phenotypic Characterization of Virulent Bacteriophages Against Multidrug-Resistant Escherichia coli and Its Phage-Resistant Variant from Sewage Sources

Purpose

The use of lytic bacteriophages for the control or elimination of pathogenic multidrug-resistant (MDR) bacteria is the promising alternative. However, the emergence of resistant bacterial variants after phage application may challenge its therapeutic benefit. In this study, we aimed to isolate candidate phages from sewage samples against two MDR Escherichia coli as well as their phage-resistant variant.

Methods

MDR E. coli isolates (n = 10) obtained from Jimma Medical Center that had been properly identified and stored were used to isolate bacteriophages. Two lytic coliphages were isolated from hospital sewage samples following standard protocols. Upon single phage infection, phage-resistant variant quickly evolved serving as a new host for the isolation of a third lytic phage. This virulent phage's lytic activity against both its host and the wild host was investigated. The host infectivity of the various cocktails was assessed, and each phage's biological properties were studied.

Results

Out of the first round of phage isolation process, two lytic phages were identified as VBO-E. coli 4307 and VBW-E. coli 4194. When exposed to VBO-E. coli 4307, the wild-type E. coli 4307 developed resistant variants. A third phage (VBA-E. coli 4307R) was isolated specific to this resistant variant (E. coli 4307R) under optimum condition. For VBO-E. coli 4307, VBW-E. coli 4194, and VBA-E. coli 4307R, the plaque assays generated under comparable conditions were 2.13 × 1010 PFU mL-1, 9.17 × 1012 PFU mL-1, and 3.3 × 1010 PFU mL-1, respectively. These phages have nearly identical stability and lytic ability but differ greatly in their host ranges for VBA-E. coli 4307R.

Conclusion

While the wild-type MDR pathogen could easily evolve resistance when exposed to a single phage infection by VBO-E. coli 4307, it is still possible to isolate a novel bacteriophage from environmental samples that is effective against the phage-resistant variants. This indicates that it is possible to manage the effects of phage resistance pathogens even if they are MDR.

Bacteriophages in wastewater treatment: can they be an approach to optimize biological treatment processes?

In this paper, we explore the applications of bacteriophages and the advantages of using these viruses to control undesirable organisms in wastewater treatment plants. Based on this, this paper reviewed the literature on the subject by performing a bibliometric and scientometric analysis of articles published in peer-reviewed journals through 2021. We obtained 806 publications, of which 40% were published in the last 5 years, demonstrating an increase in interest in the subject. These articles analyzed, bacteriophages in treatment plants were strongly linked to bacteria such as Escherichia coli and related to disinfection, inactivation, sewage, and wastewater, in addition, biocontrol studies have gained prominence in recent years, particularly due to the resistance of microorganisms to antibiotics. Studies have shown that bacteriophages have great potential for application in treatment systems to control unwanted processes and act as valuable economic and environmental tools to improve the efficiency of various treatment technologies. Although these viruses have already been studied in various applications to optimize treatment plant processes, technology transfer remains a challenge due to the limitations of the technique-such as physicochemical factors related to the environment-and the complexity of biological systems. The research focusing on application strategies in conjunction with molecular biology techniques can expand this study area, enabling the discovery of new bacteriophages.

Evaluating the Phenotypic and Genomic Characterization of Some Egyptian Phages Infecting Shiga Toxin-Producing Escherichia coli O157:H7 for the Prospective Application in Food Bio-Preservation

Simple Summary

Shiga toxin-producing Escherichia coli (STEC) represents a hazardous health problem because it causes various human gastrointestinal tract diseases, for example, bloody diarrhea and hemorrhagic colitis. The major concern of STEC O157:H7 resulted from its biological characteristics, including low infective dose, ability to express different virulence factors and multidrug resistance of some species. Principally, the human outbreaks of STEC O157:H7 are associated with consumption of undercooked or contaminated bovine dairy and meat products. Treatments of E. coli infections have been increasingly complicated as a result of the development of antibiotic resistance. For this reason, as well as the increasing consumer demand for safe food products, it has become important to apply alternative effective and eco-friendly approaches, such as using lytic phages, to control the growth of pathogenic bacteria in food. This study focused on evaluating the applicability of locally isolated lytic phages specific to Shiga toxin-producing Escherichia coli O157:H7 as prospective biocontrol agents in food. Our findings presented two phages with promising biological and genomic characteristics to be applied in food bio-preservation.

Abstract

Shiga toxin-producing E. coli (STEC) is considered a worldwide public health and food safety problem. Despite the implementation of various different approaches to control food safety, outbreaks persist. The aim of study is to evaluate the applicability of phages, isolated against STEC O157:H7, as prospective food bio-preservatives. Considering the relatively wide host range and greatest protein diversity, two phages (STEC P2 and P4) from four were furtherly characterized. Complete genome analysis confirmed the absence of toxins and virulence factors—encoding genes. The results confirmed the close relation of STEC P2 to phages of Myoviridae, and STEC P4 to the Podoviridae family. The phages retained higher lytic competence of 90.4 and 92.68% for STEC P2 and P4, respectively with the HTST pasteurization. The strong acidic (pH 1) and alkaline (pH 13) conditions had influential effect on the surviving counts of the two phages. The lowest survivability of 63.37 and 86.36% in STEC P2 and P4 lysate, respectively appeared in 2% bile salt solution after 3 h. The results confirmed the strong effect of simulated gastric fluid (SGF) on the survivability of the two phages comparing with simulated intestinal fluid (SIF). Therefore, the two phages could be applied as a natural alternative for food preservation.

Isolation, Characterization, and Genomic Analysis of Three Novel E. coli Bacteriophages That Effectively Infect E. coli O18

Escherichia coli (E. coli) is one of the most common pathogenic bacteria worldwide. Avian pathogenic E. coli (APEC) causes severe systemic disease in poultry (Colibacillosis), and accordingly, has an extreme risk to the poultry industry and public health worldwide. Due to the increased rate of multi-drug resistance among these bacteria, it is necessary to find an alternative therapy to antibiotics to treat such infections. Bacteriophages are considered one of the best solutions. This study aimed to isolate, characterize, and evaluate the potential use of isolated bacteriophages to control E. coli infections in poultry. Three novel phages against E. coli O18 were isolated from sewage water and characterized in vitro. The genome size of the three phages was estimated to be 44,776 bp, and the electron microscopic analysis showed that they belonged to the Siphoviridae family, in the order Caudovirales. Phages showed good tolerance to a broad range of pH and temperature. The complete genomes of three phages were sequenced and deposited into the GenBank database. The closely related published genomes of Escherichia phages were identified using BLASTn alignment and phylogenetic trees. The prediction of the open reading frames (ORFs) identified protein-coding genes that are responsible for functions that have been assigned such as cell lysis proteins, DNA packaging proteins, structural proteins, and DNA replication/transcription/repair proteins.