Characterization of a novel high-efficiency cracking Burkholderia gladiolus phage vB_BglM_WTB and its application in black fungus

Burkholderia gladiolus (B. gladiolus) is foodborne pathogenic bacteria producing bongkrekic acid (BA), which causes food poisoning and has a mortality rate of up to 40 % or more. However, no drugs have been reported in the literature for the prevention and treatment of this infection. In this study, a phage was identified to control B. gladiolus. The novel phage vB_BglM_WTB (WTB), which lyse B. gladiolus with high efficiency, was isolated from sewage of Huaihe Road Throttle Well Sewage Treatment Plant in Hefei. Transmission electron microscopy showed that WTB had an icosahedral head (69 ± 2 nm) and a long retractable tail (108 ± 2 nm). Its optimal temperature and pH ranges to control B. gladiolus were 25 °C -65 °C and 3-11 respectively. The phage WTB was identified as a linear double-stranded DNA phage of 68, 541 bp with 60.04 % G + C content, with a long latent period of 60 min. Phylogenetic analysis and comparative genetic analysis indicated that phage WTB has low identity (<50 %) with other phages, with the highest similarity to Burkholderia phage Maja (25.7 %), which showed that it does not belong to any previous genera recognized by the International Committee on Taxonomy of Viruses (ICTV) and was a candidate for a new genus within the Caudoviricetes. We have submitted a new proposal to ICTV to create a new genus, Bglawtbvirus. No transfer RNA (tRNA), virulence associated and antibiotic resistance genes were detected in phage WTB. Experimental results indicated that WTB at 4 °C and 25 °C had excellent inhibition activity against B. gladiolus in the black fungus, with an inhibition efficiency of over 99 %. The amount of B. gladiolus in the black fungus was reduced to a minimum of 89 CFU/mL when treated by WTB at 25 °C for 2 h. The inhibition rate remained at 99.97 % even after 12 h. The findings showed that the phage WTB could be applied as a food-cleaning agent for enhancing food safety and contributed to our understanding of phage biology and diversity.

Tracking the contamination sources of microbial population and characterizing Listeria monocytogenes in a chicken slaughterhouse by using culture-dependent and -independent methods

Listeria monocytogenes is the etiologic agent of listeriosis, a foodborne disease that poses a threat to public health globally. Chicken meat exhibits heightened susceptibility to L. monocytogenes contamination during butchery. The persistence of this pathogen in the slaughterhouse environment enables recurring contamination of meat products. This study aimed at identifying the sources and transmission routes of L. monocytogenes contamination within an abattoir where it was consistently detected for three consecutive years (2019-2021). Furthermore, the environmental factors aiding contamination along chicken processing lines were determined by surveying the microbiome within the facility. Samples collected in 2019 to 2021 were subjected to culture-dependent analysis to assess the prevalence, serotypes, and multi-locus sequence typing (MLST) of L. monocytogenes. Additionally, the specimens collected in 2021 underwent culture-independent analysis via real-time quantitative polymerase chain reaction (qPCR) and 16S rRNA gene amplicon sequencing to identify the contamination sources and characterize the entire microbial community within the slaughterhouse. L. monocytogenes was isolated only from the clean zone, where the final slaughtering stage occurs. Most strains isolated from the final carcasses showed the same genetic cluster as the isolate in the chilling water and were assigned to MLST profile ST3. Culture-independent qPCR confirmed L. monocytogenes contamination in all samples, excluding post-scalding carcasses, prewashed post-evisceration carcasses, and the bleeding areas. Consequently, qPCR enabled more comprehensive identification of L. monocytogenes contamination points than culture-dependent approaches. Moreover, 16S rRNA gene amplicon sequencing demonstrated that psychro-tolerant and spoilage-related bacteria with L. monocytogenes-like attributes exhibited enhanced viability in the clean zone and immersion-chilling water. Metagenomics-based source tracking analysis further revealed that the shackles and chilling waters represent predominant sources of cross-contamination between different slaughterhouse zones, whereas the grading and packaging workstations and chilling water in the clean zone were deemed crucial sources affecting final carcass contamination. Collectively, these findings demonstrate through culture-dependent and -independent methods that L. monocytogenes spreads along the slaughter line, contaminating the slaughterhouse. Moreover, by investigating changes in microbial community and bacterial flow along the slaughter line within the facility, the sources influencing carcass contamination can be effectively traced.

Molecular Methods for Identification and Quantification of Foodborne Pathogens

Foodborne pathogens that enter the human food chain are a significant threat worldwide to human health. Timely and cost-effective detection of them became challenging for many countries that want to improve their detection and control of foodborne illness. We summarize simple, rapid, specific, and highly effective molecular technology that is used to detect and identify foodborne pathogens, including polymerase chain reaction, isothermal amplification, loop-mediated isothermal amplification, nucleic acid sequence-based amplification, as well as gene chip and gene probe technology. The principles of their operation, the research supporting their application, and the advantages and disadvantages of each technology are summarized.

Antimicrobial peptides: Promising alternatives over conventional capture ligands for biosensor-based detection of pathogenic bacteria

The detection of pathogenic bacteria using biosensing techniques could be a potential alternative to traditional culture based methods. However, the low specificity and sensitivity of conventional biosensors, critically related to the choice of bio-recognition elements, limit their practical applicability. Mammalian antibodies have been widely investigated as biorecognition ligands due to high specificity and technological advancement in antibody production. However, antibody-based biosensors are not considered as an efficient approach due to the batch-to-batch inconsistencies as well as low stability. In recent years, antimicrobial peptides (AMPs) have been increasingly investigated as ligands as they have demonstrated high stability and possessed multiple sites for capturing bacteria. The conjugation of chemo-selective groups with AMPs has allowed effective immobilization of peptides on biosensor surface. However, the specificity of AMPs is a major concern for consideration as an efficient ligand. In this article, we have reviewed the advances and concerns, particularly the selectivity of AMPs for specific detection of pathogenic bacteria. This review also focuses the state-of-the-art mechanisms, challenges and prospects for designing potential AMP conjugated biosensors. The application of AMP in different biosensing transducers such as electrochemical, optical and piezoelectric varieties has been widely discussed. We argue that this review would provide insights to design and construct AMP conjugated biosensors for the pathogenic bacteria detection.

Direct detection of Salmonella from poultry samples by DNA isothermal amplification

1. Salmonellosis is one of the most important diseases in public health and it is usually associated with poultry product consumption. This study aimed to validate rapid methods to detect Salmonella spp. from poultry samples. 2. A DNA isothermal amplification method, previously developed for other matrices, was applied for the specific detection of Salmonella spp. from various samples, including poultry tissues, drag and boot swabs, faeces and feed. A new procedure was validated with Salmonella spp. serotypes and isolates from other enteric bacterial species, as well as naturally contaminated poultry samples. 3. The study demonstrated the successful development and implementation of a procedure, including a DNA isothermal amplification method, for the detection of Salmonella spp. directly from tissues, drag and boot swabs, faeces and feed. The whole procedure can be performed in less than 24 hours and it has been successfully used in a veterinary diagnostic laboratory.

Whole-genome sequencing of Escherichia coli isolated from contaminated meat samples collected from the Northern Region of Ghana reveals the presence of multiple antimicrobial resistance genes

OBJECTIVES

This study reports the draft genomes of 14 Escherichia coli isolated from contaminated meat samples collected from the Northern Region of Ghana in order to determine the presence of antimicrobial resistance genes (ARGs) and genetic relatedness of the isolates.

METHODS

The 14 E. coli isolates were of beef (n=3), mutton (n=2), chevon (n=3), local chicken (n=3) and guinea fowl (n=3) origin. Whole-genome sequencing (WGS) was performed using an Illumina MiSeq sequencer. Double-disk synergy test (DDST) was also used to confirm the production of extended-spectrum β-lactamase (ESBL).

RESULTS

WGS confirmed the identity of all of the E. coli isolates. All of the isolates contained at least one ARG and 57.1% (8/14) of them were multidrug-resistant (MDR). The mdf(A) gene was most common ARG, found in all 14 isolates. DDST confirmed the production of an ESBL in a MDR E. coli of guinea fowl origin. The sequence types (STs) varied among the E. coli isolates, with the exception of three isolates of ST155. Similarly, the serotypes of the E. coli isolates from meat sample were genetically diverse. Eleven different plasmid sequences were detected in ten of the isolates.

CONCLUSION

E. coli from contaminated meat sources in Ghana possessed multiple ARGs and were genetically diverse. To the best of our knowledge, this is the first work on WGS of E. coli isolated from various meat samples in the study area. The sequence data add to data base for epidemiological studies.

Application of molecular tools to elucidate the microbiota of seafood

The aim of this review is to present the methodologies currently applied to identify microbiota and pathogens transmitted to humans through seafood consumption, focusing on molecular techniques and pointing out their importance, advantages, disadvantages and applicability. Knowledge of available techniques allows researchers to identify which technique best fits their expectations. With such discernment, it will be possible to infer which disadvantages will be present and, therefore, not interfering with the final result. Two methodologies can be employed for this purpose, dependent and independent cultures. However, the dependent culture has certain limitations that can be solved through the independent cultivation techniques, such as PCR, PFGE and NGS, especially through the sequencing of the 16S rRNA region, providing a complete view of microbial diversity. These have revolutionized microbiological knowledge, mainly because they allow for the identification of uncultivable micro-organisms, which represent a substantial portion of total micro-organisms, making it possible to elucidate not yet described taxa which may display pathogenic potential, besides quantifying microbial communities, microbiota genetics, translated proteins and produced metabolites. In addition, transcriptomic and metabolomic techniques also allow for the evaluation of possible impacts that microbial communities may create in their environment, as well as the determination of potential pathogenicity to humans.

Genetic characterization of antibiotic-resistant Staphylococcus aureus from milk in the North-West Province, South Africa

Food borne diseases are a major public health concern worldwide. Staphylococcus aureus is one of the potential food borne pathogens which causes nosocomial and community acquired infections. In the present study, 74 representative strains of S. aureus isolated and characterized in previous study from different milk samples were subjected to random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) and enterobacterial repetitive intergenic consensus (ERIC)-PCR to generate fingerprints to determine the genetic relationships of the isolated strains. A total of 20 RAPD patterns were generated and the number of amplified fragments obtained ranged from 0 to 8 with molecular weight ranging from 250 to 2000 bp. A dendrogram based on fingerprinting pattern grouped isolates into twelve major clusters (I–XII). In the case of ERIC-PCR 9 banding patterns were obtained with amplicons ranging from 1 to 8 and band sizes ranging from 250 to 2000 bp. A total of four major clusters (I–IV) were observed in the dendrogram based on ERIC fingerprints. The discrete banding patterns obtained both from ERIC-PCR and RAPD-PCR showed remarkably the genetic diversity of S. aureus. The findings of this study indicate that raw, bulk and pasteurized milk in the North-West Province was contaminated with toxigenic and multi-drug resistant S. aureus strains. This emphasizes the need to implement appropriate control measures to reduce contamination as well as the spread of virulent S. aureus strains to reduce the burden of disease in humans.

On the track for an efficient detection of Escherichia coli in water: A review on PCR-based methods

Ensuring water safety is an ongoing challenge to public health providers. Assessing the presence of fecal contamination indicators in water is essential to protect public health from diseases caused by waterborne pathogens. For this purpose, the bacteria Escherichia coli has been used as the most reliable indicator of fecal contamination in water. The methods currently in use for monitoring the microbiological safety of water are based on culturing the microorganisms. However, these methods are not the desirable solution to prevent outbreaks as they provide the results with a considerable delay, lacking on specificity and sensitivity. Moreover, viable but non-culturable microorganisms, which may be present as a result of environmental stress or water treatment processes, are not detected by culture-based methods and, thus, may result in false-negative assessments of E. coli in water samples. These limitations may place public health at significant risk, leading to substantial monetary losses in health care and, additionally, in costs related with a reduced productivity in the area affected by the outbreak, and in costs supported by the water quality control departments involved. Molecular methods, particularly polymerase chain reaction-based methods, have been studied as an alternative technology to overcome the current limitations, as they offer the possibility to reduce the assay time, to improve the detection sensitivity and specificity, and to identify multiple targets and pathogens, including new or emerging strains. The variety of techniques and applications available for PCR-based methods has increased considerably and the costs involved have been substantially reduced, which together have contributed to the potential standardization of these techniques. However, they still require further refinement in order to be standardized and applied to the variety of environmental waters and their specific characteristics. The PCR-based methods under development for monitoring the presence of E. coli in water are here discussed. Special emphasis is given to methodologies that avoid pre-enrichment during the water sample preparation process so that the assay time is reduced and the required legislated sensitivity is achieved. The advantages and limitations of these methods are also reviewed, contributing to a more comprehensive overview toward a more conscious research in identifying E. coli in water.

Genetic diversity of Escherichia coli isolated from ducks and the environment using enterobacterial repetitive intergenic consensus

Escherichia coli are mostly free living bacteria that harbour the gastrointestinal tract of poultry. Howbeit, pathogenic Escherichia coli are very important foodborne pathogens that can cause severe complications, illnesses and deaths in humans. The objective of this study was to determine the genetic diversity or relatedness of 62 Escherichia coli strains isolated from ducks and the environment using Enterobacterial Repetitive Intergenic Consensus (ERIC). The analysis of the Escherichia coli strains by ERIC produced DNA bands of different sizes for differentiation purposes and cluster analysis at a coefficient of 0.85 grouped the strains into different clusters and singletons. At this coefficient the Escherichia coli strains were grouped into thirteen clusters and eleven singletons with discriminatory index (D value) of 0.946. The ERIC PCR adapted in this study showed to be a useful genotyping tool for determining the genetic relatedness of the duck Escherichia coli strains. Comparison of the genetic relatedness among foodborne pathogens is important for foodborne diseases outbreak investigations.

Molecular techniques for detecting and typing of bacteria, advantages and application to foodborne pathogens isolated from ducks

In recent times, several foodborne pathogens have become important and a threat to public health. Surveillance studies have provided data and a better understanding into the existence and spread of foodborne pathogens. The application of molecular techniques for detecting and typing of foodborne pathogens in surveillance studies provide reliable epidemiological data for tracing the source of human infections. A wide range of molecular techniques (including pulsed field gel electrophoresis, multilocus sequence typing, random amplified polymorphism deoxyribonucleic acid, repetitive extragenic palindromic, deoxyribonucleic acid sequencing, multiplex polymerase chain reaction and many more) have been used for detecting, speciating, typing, classifying and/or characterizing foodborne pathogens of great significance to humans. Farm animals including chickens, cattle, sheep, goats and pigs, and others (such as domestic and wild animals) have been reported to be primary reservoirs for foodborne pathogens. The consumption of contaminated poultry meats or products has been considered to be the leading source of human foodborne infections. Ducks like other farm animals are important source of foodborne pathogens and have been implicated in some human foodborne illnesses and deaths. Nonetheless, few studies have been conducted to explore the potential of ducks in causing foodborne outbreaks, diseases and its consequences. This review highlights some common molecular techniques, their advantages and those that have been applied to pathogens isolated from ducks and their related sources.

Nanobiotechnologies for the detection and reduction of pathogens

Advances in the manipulation of nanomaterials has permitted the development of nanobiotechnology with enhanced sensitivities and improved response times. Low levels of infection of the major pathogens require the need for sensitive detection platforms and the properties of nanomaterials make them suitable for the development of assays with enhanced sensitivity, improved response time and increased portability. Nanobiotechnologies focusing on the key requirements of signal amplification and pre-concentration for the development of sensitive assays for food-borne pathogen detection in food matrices will be described and evaluated. The potential that exists for the use of nanomaterials as antimicrobial agents will also be examined.