Use of Bacteriophage Amended with CRISPR-Cas Systems to Combat Antimicrobial Resistance in the Bacterial Foodborne Pathogen Listeria monocytogenes

Comparative genomics analysis to explore the biodiversity and mining novel target genes of Listeria monocytogenes strains from different regions

As a common foodborne pathogen, infection with L. monocytogenes poses a significant threat to human life and health. The objective of this study was to employ comparative genomics to unveil the biodiversity and evolutionary characteristics of L. monocytogenes strains from different regions, screening for potential target genes and mining novel target genes, thus providing significant reference value for the specific molecular detection and therapeutic targets of L. monocytogenes strains. Pan-genomic analysis revealed that L. monocytogenes from different regions have open genomes, providing a solid genetic basis for adaptation to different environments. These strains contain numerous virulence genes that contribute to their high pathogenicity. They also exhibit relatively high resistance to phosphonic acid, glycopeptide, lincosamide, and peptide antibiotics. The results of mobile genetic elements indicate that, despite being located in different geographical locations, there is a certain degree of similarity in bacterial genome evolution and adaptation to specific environmental pressures. The potential target genes identified through pan-genomics are primarily associated with the fundamental life activities and infection invasion of L. monocytogenes, including known targets such as inlB, which can be utilized for molecular detection and therapeutic purposes. After screening a large number of potential target genes, we further screened them using hub gene selection methods to mining novel target genes. The present study employed eight different hub gene screening methods, ultimately identifying ten highly connected hub genes (bglF_1, davD, menE_1, tilS, dapX, iolC, gshAB, cysG, trpA, and hisC), which play crucial roles in the pathogenesis of L. monocytogenes. The results of pan-genomic analysis showed that L. monocytogenes from different regions exhibit high similarity in bacterial genome evolution. The PCR results demonstrated the excellent specificity of the bglF_1 and davD genes for L. monocytogenes. Therefore, the bglF_1 and davD genes hold promise as specific molecular detection and therapeutic targets for L. monocytogenes strains from different regions.

The CRISPR/Cas system as an antimicrobial resistance strategy in aquatic ecosystems

With the growing population, demand for food has dramatically increased, and fisheries, including aquaculture, are expected to play an essential role in sustaining demand with adequate quantities of protein and essential vitamin supplements, employment generation, and GDP growth. Unfortunately, the incidence of emerging/re-emerging AMR pathogens annually occurs because of anthropogenic activities and the frequent use of antibiotics in aquaculture. These AMR pathogens include the WHO's top 6 prioritized ESKAPE pathogens (nosocomial pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), extended-spectrum beta lactases (ESBLs) and carbapenemase-producing E. coli, which pose major challenges to the biomagnification of both nonnative and native antibiotic-resistant bacteria in capture and cultured fishes. Although implementing the rational use of antibiotics represents a promising mitigation measure, this approach is practically impossible due to the lack of awareness among farmers about the interplay between antimicrobial use and the emergence of antimicrobial resistance (AMR). Nevertheless, to eradicate these 'superbugs,' CRISPR/Cas (clustered regularly interspersed short palindromic repeats/CRISPR associate protein) has turned out to be a novel approach owing to its ability to perform precise site-directed targeting/knockdown/reversal of specific antimicrobial resistance genes in vitro and to distinguish AMR-resistant bacteria from a plethora of commensal aquatic bacteria. Along with highlighting the importance of virulent multidrug resistance genes in bacteria, this article aims to provide a holistic picture of CRISPR/Cas9-mediated genome editing for combating antimicrobial-resistant bacteria isolated from various aquaculture and marine systems, as well as insights into different types of CRISPR/Cas systems, delivery methods, and challenges associated with developing CRISPR/Cas9 antimicrobial agents.

Whole Genome Sequence Analysis of Listeria monocytogenes Isolates Obtained from the Beef Production Chain in Gauteng Province, South Africa

The study used whole-genome sequencing (WGS) and bioinformatics analysis for the genomic characterization of 60 isolates of Listeria monocytogenes obtained from the beef production chain (cattle farms, abattoirs, and retail outlets) in Gauteng province, South Africa. The sequence types (STs), clonal complexes (CCs), and the lineages of the isolates were determined using in silico multilocus sequence typing (MLST). We used BLAST-based analyses to identify virulence and antimicrobial genes, plasmids, proviruses/prophages, and the CRISPR-Cas system. The study investigated any association of the detected genes to the origin in the beef production chain of the L. monocytogenes isolates. Overall, in 60 isolates of Listeria monocytogenes, there were seven STs, six CCs, forty-four putative virulence factors, two resistance genes, one plasmid with AMR genes, and three with conjugative genes, one CRISPR gene, and all 60 isolates were positive for proviruses/prophages. Among the seven STs detected, ST204 (46.7%) and ST2 (21.7%) were the most prominent, with ST frequency varying significantly (p < 0.001). The predominant CC detected were CC2 (21.7%) and CC204 (46.7%) in lineages I and II, respectively. Of the 44 virulence factors detected, 26 (across Listeria Pathogenicity Islands, LIPIs) were present in all the isolates. The difference in the detection frequency varied significantly (p < 0.001). The two AMR genes (fosX and vga(G)) detected were present in all 60 (100%) isolates of L. monocytogenes. The only plasmid, NF033156, was present in three (5%) isolates. A CRISPR-Cas system was detected in six (10%), and all the isolates carried proviruses/prophages. The source and sample type significantly affected the frequencies of STs and virulence factors in the isolates of L. monocytogenes. The presence of fosX and vga(G) genes in all L. monocytogenes isolates obtained from the three industries of the beef production chain can potentially cause therapeutic implications. Our study, which characterized L. monocytogenes recovered from the three levels in the beef production chain, is the first time genomics was performed on this type of data set in the country, and this provides insights into the health implications of Listeria.

CRISPR-Cas systems of lactic acid bacteria and applications in food science

CRISPR-Cas (Clustered regularly interspaced short palindromic repeats-CRISPR associated proteins) systems are widely distributed in lactic acid bacteria (LAB), contributing to their RNA-mediated adaptive defense immunity. The CRISPR-Cas-based genetic tools have exhibited powerful capability. It has been highly utilized in different organisms, accelerating the development of life science. The review summarized the components, adaptive immunity mechanisms, and classification of CRISPR-Cas systems; analyzed the distribution and characteristics of CRISPR-Cas system in LAB. The review focuses on the development of CRISPR-Cas-based genetic tools in LAB for providing latest development and future trend. The diverse and broad applications of CRISPR-Cas systems in food/probiotic industry are introduced. LAB harbor a plenty of CRISPR-Cas systems, which contribute to generate safer and more robust strains with increased resistance against bacteriophage and prevent the dissemination of plasmids carrying antibiotic-resistance markers. Furthermore, the CRISPR-Cas system from LAB could be used to exploit novel, flexible, programmable genome editing tools of native host and other organisms, resolving the limitation of genetic operation of some LAB species, increasing the important biological functions of probiotics, improving the adaptation of probiotics in complex environments, and inhibiting the growth of foodborne pathogens. The development of the genetic tools based on CRISPR-Cas system in LAB, especially the endogenous CRISPR-Cas system, will open new avenues for precise regulation, rational design, and flexible application of LAB.

Investigation of a Listeria monocytogenes Chromosomal Immigration Control Region Reveals Diverse Restriction Modification Systems with Complete Sequence Type Conservation

Listeria monocytogenes is a Gram-positive pathogen responsible for the severe foodborne disease listeriosis. A chromosomal hotspot between lmo0301 and lmo0305 has been noted to harbor diverse restriction modification (RM) systems. Here, we analyzed 872 L. monocytogenes genomes to better understand the prevalence and types of RM systems in this region, designated the immigration control region (ICR). Type I, II, III and IV RM systems were found in 86.1% of strains inside the ICR and in 22.5% of strains flanking the ICR. ICR content was completely conserved within the same multilocus sequence typing-based sequence type (ST), but the same RM system could be identified in diverse STs. The intra-ST conservation of ICR content suggests that this region may drive the emergence of new STs and promote clone stability. Sau3AI-like, LmoJ2 and LmoJ3 type II RM systems as well as type I EcoKI-like, and type IV AspBHI-like and mcrB-like systems accounted for all RM systems in the ICR. A Sau3AI-like type II RM system with specificity for GATC was harbored in the ICR of many STs, including all strains of the ancient, ubiquitous ST1. The extreme paucity of GATC recognition sites in lytic phages may reflect ancient adaptation of these phages to preempt resistance associated with the widely distributed Sau3AI-like systems. These findings indicate that the ICR has a high propensity for RM systems which are intraclonaly conserved and may impact bacteriophage susceptibility as well as ST emergence and stability.

Comparative Genomics of Listeria Species Recovered from Meat and Food Processing Facilities

Listeria species (spp.) are contaminants that can survive in food, on equipment, and on food processing premises if appropriate hygiene measures are not used. Homologous stress tolerance genes, virulence gene clusters such as the prfA cluster, and clusters of internalin genes that contribute to the pathogenic potential of the strains can be carried by both pathogenic and nonpathogenic Listeria spp. To enhance understanding of the genome evolution of virulence and virulence-associated properties, a comparative genome approach was used to analyze 41 genome sequences belonging to L. innocua and L. welshimeri isolated from food and food processing facilities. Genetic determinants responsible for disinfectant and stress tolerance were identified, including the efflux cassette bcrABC and Tn6188_qac_1 disinfectant resistance determinant, and stress survival islets. These disinfectant-resistant genes were more frequently found in L. innocua (12%) than in L. welshimeri (2%). Several isolates representing the presumed nonpathogenic L. innocua still carried virulence-associated genes, including LGI2, LGI3, LIPI-3, and LIPI-4 which were absent in all L. welshimeri isolates. The mobile genetic elements identified were plasmids (pLGUG1 and J1776) and prophages (PHAGE_Lister_vB_LmoS_188, PHAGE_Lister_LP_030_3, PHAGE_Lister_A118, PHAGE_Lister_B054, and PHAGE_Lister_vB_LmoS_293). The results suggest that the presumed nonpathogenic isolates especially L. innocua can carry genes relevant to the strain's virulence and stress tolerance in the food and food processing facilities. IMPORTANCE This study provides genomic insights into the recently expanded genus in order to gain valuable information about the evolution of the virulence and stress tolerance properties of the genus Listeria and the distribution of these genetic elements pertinent to the pathogenic potential across Listeria spp. and clonal lineages in South Africa (SA).

Combined Effect of Ultrasound and Microwave Power in Tangerine Juice Processing: Bioactive Compounds, Amino Acids, Minerals, and Pathogens

The inhibition of Escherichia coli ATCC 25922 (E. coli), Staphylococcus aureus ATCC6538 (S. aureus), Salmonella Enteritidis ATCC 13076 (S. Enteritidis), and Listeria monocytogenes DSM12464 (L. monocytogenes) is one of the main aims of the food industry. This study was the first in which the use of ultrasound and microwave power were applied to optimize the values of the bioactive components, amino acids, and mineral compositions of tangerine juice and to inhibit Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis, and Listeria monocytogenes. The response surface methodology (RSM) was used to describe the inactivation kinetics, and the effects of ultrasound treatment time (X1: 12–20 min), ultrasound amplitude (X2:60–100%), microwave treatment time (X3: 30–40 s), and microwave power (X4:200–700 W). The optimum parameters applied to a 5-log reduction in E. coli were determined as ultrasound (12 min, 60%) and microwave (34 s, 700 W). The optimum condition ultrasound–microwave treatment was highly effective in tangerine juice, achieving up to 5.27, 5.12, and 7.19 log reductions for S. aureus, S. Enteritidis, and L. monocytogenes, respectively. Ultrasound–microwave treatment increased the total phenolic compounds and total amino acids. While Cu, K, Mg, and Na contents were increased, Fe and Ca contents were lower in the UM-TJ (ultrasound–microwave-treated tangerine juice) sample. In this case, significant differences were detected in the color values of ultrasound–microwave-treated tangerine juice (UM-TJ) (p < 0.05). The results of this study showed that ultrasound–microwave treatment is a potential alternative processing and preservation technique for tangerine juice, resulting in no significant quality depreciation.

Phage delivered CRISPR-Cas system to combat multidrug-resistant pathogens in gut microbiome

The Host-microbiome interactions that exist inside the gut microbiota operate in a synergistic and abnormal manner. Additionally, the normal homeostasis and functioning of gut microbiota are frequently disrupted by the intervention of Multi-Drug Resistant (MDR) pathogens. CRISPR-Cas (CRISPR-associated protein with clustered regularly interspersed short palindromic repeats) recognized as a prokaryotic immune system has emerged as an effective genome-editing tool to edit and delete specific microbial genes for the expulsion of bacteria through bactericidal action. In this review, we demonstrate many functioning CRISPR-Cas systems against the anti-microbial resistance of multiple pathogens, which infiltrate the gastrointestinal tract. Moreover, we discuss the advancement in the development of a phage-delivered CRISPR-Cas system for killing a gut MDR pathogen. We also discuss a combinatorial approach to use bacteriophage as a delivery system for the CRISPR-Cas gene for targeting a pathogenic community in the gut microbiome to resensitize the drug sensitivity. Finally, we discuss engineered phage as a plausible potential option for the CRISPR-Cas system for pathogenic killing and improvement of the efficacy of the system.

Review of CRISPR-Cas Systems in Listeria Species: Current Knowledge and Perspectives

Listeria spp. are pathogens widely distributed in the environment and Listeria monocytogenes is associated with food-borne illness in humans. Food facilities represent an adverse environment for this bacterium, mainly due to the disinfection and cleaning processes included in good hygiene practices, and its virulence is related to stress responses. One of the recently described stress-response systems is CRISPR-Cas. Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (cas) genes have been found in several bacteria. CRISPR-Cas has revolutionized biotechnology since it acts as an adaptive immune system of bacteria, which also helps in the evasion of the host immune response. There are three CRISPR systems described on Listeria species. Type II is present in many pathogenic bacteria and characterized by the presence of cas9 that becomes the main target of some anti-CRISPR proteins, such as AcrIIA1, encoded on Listeria phages. The presence of Cas9, either alone or in combination with anti-CRISPR proteins, suggests having a main role on the virulence of bacteria. In this review, we describe the most recent information on CRISPR-Cas systems in Listeria spp., particularly in L. monocytogenes, and their relationship with the virulence and pathogenicity of those bacteria. Besides, some applications of CRISPR systems and future challenges in the food processing industry, bacterial vaccination, antimicrobial resistance, pathogens biocontrol by phage therapy, and regulation of gene expression have been explored.