Non-toxigenic Strains Research Articles

Application and antagonistic mechanisms of atoxigenic Aspergillus strains for the management of fungal plant diseases.

This review covers, for the first time, all methods based on the use of Aspergillus strains as biocontrol agents for the management of plant diseases caused by fungi and oomycetes. Atoxigenic Aspergillus strains have been screened in a variety of hosts, such as peanuts, maize kernels, and legumes, during the preharvest and postharvest stages. These strains have been screened against a wide range of pathogens, such as Fusarium, Phytophthora, and Pythium species, suggesting a broad applicability spectrum. The highest efficacies were generally observed when using non-toxigenic Aspergillus strains for the management of mycotoxin-producing Aspergillus strains. The modes of action included the synthesis of antifungal metabolites, such as kojic acid and volatile organic compounds (VOCs), secretion of hydrolytic enzymes, competition for space and nutrients, and induction of disease resistance. Aspergillus strains degraded Sclerotinia sclerotiorum sclerotia, showing high control efficacy against this pathogen. Collectively, although two Aspergillus strains have been commercialized for aflatoxin degradation, a new application of Aspergillus strains is emerging and needs to be optimized.

Opportunistic Features of Non-Clostridium botulinum Strains Containing bont Gene Cluster.

The cluster of genes determining the production of botulinum toxins is an attribute of not only the Clostridium botulinum species. This cluster is also found in other members of the Clostridium genus, such as C. baratii, C. butyricum, and C. sporogenes. The occurrence of a botulinum-like cluster has also been recorded in strains of other genera, i.e., Enterococcus faecium, as well as in a Gram-negative species isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. It can be said that the mentioned species have a dual nature. Another species with a dual nature is C. butyricum. This bacterium is a common human and animal gut commensal bacterium and is also frequently found in the environment. Although non-toxigenic strains are currently used as probiotics in Asia, other strains have been implicated in pathological conditions, such as botulism in infants or necrotizing enterocolitis in preterm neonates. Additionally, C. baratii strains are rare opportunistic pathogens associated with botulism intoxication. They have been isolated from food and soil and can be carried asymptomatically or cause botulism outbreaks in animals and humans. In addition to the mentioned clostridia, the other microorganisms considered as non-toxigenic have also been suspected of carrying botulinum cluster Gram-negative bacteria, such as Chryseobacterium piperi isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. Additionally, Enterococcus faecium strains have been discovered carrying BoNT-related clusters (BoNT/En). Literature data regarding the heterogeneity of BoNT-producing strains indicate the requirement to reclassify C. botulinum species and other microorganisms able to produce BoNTs or possess botulinum-like gene clusters. This article aims to show the dual nature of Clostridium strains not belonging to the C. botulinum species that are sporadically able to carry bont clusters, which are usually considered saprophytic and even probiotic, and bont-like clusters in microorganisms from other genera. The aim was also to consider the genetic mechanisms of botulinum cluster expression in strains that are considered opportunistic and the microbiological safety aspects associated with their occurrence in the environment.

Characterising virulence in a nontoxigenic non-O1/non-O139 Vibrio cholerae isolate imported from Vietnam

Vibrio cholerae is a major human pathogen that can cause life-threatening acute diarrhea. V. cholerae are classified according to O-antigen polysaccharide outer membrane properties, where the serotypes O1 and O139 are strains that cause pandemics and epidemics while non-O1/non-O139 usually cause mild disease. The dynamic evolution of V. cholerae involves acquisition of new virulence factors through horizontal gene transfer and formerly nontoxigenic serogroups are increasingly being reported to cause severe forms of human disease.In this study we have serotyped one isolate (ST588-CPH) of imported V. cholerae from Vietnam to Denmark and performed whole genome sequencing to identify known virulence genes and furthermore studied the pattern of virulence in closely related pathogenic strains of V. cholerae.ST558-CPH was found to be a non-O1/non-O139 strain. Initial analysis from the whole genome sequencing gave a 96,6 % match to the O139-specific wbfZ gene, but in a second analysis with a higher identification threshold, the wbfZ gene was absent. We suggest a “de novo” display of a database misannotation, which explains the conflicting results. The MLST analysis revealed that the isolate belongs to the nontoxigenic non-O1/non-O139 sequence type ST558. ST558 has recently been reported as a sequence type forming a cluster of ST's that should be monitored, as it has shown to have virulence causing moderate to severe illness. Our analysis of virulence genes identified MakA, a recently discovered toxin, which seems to be generally present in both toxigenic and nontoxigenic strains.

Nitrogen availability controls response of microcystin concentration to phosphorus reduction: Evidence from model application to multiple lakes

Microcystis blooms are a global contemporary problem and the mechanisms underlying strain-level ecology (e.g. toxigenic fraction) and toxin (microcystin, MC) production are not sufficiently understood. Recent research suggests that MC synthesis depends on the availability of nitrogen and light, and that they protect toxigenic cells against damage by H2O2. The non-toxigenic strains employ the alternative strategy of enzymatic degradation of H2O2. Thus, MC-producing cells may have an advantage at high nitrogen and light availability. A model based on this mechanism was able to reproduce the observed patterns of toxigenic fraction and MC concentration in Lake Erie. However, it is unclear if this mechanism also applies to other systems. We investigated this by modeling nine different cases (i.e. lakes, stations, years). The model can reproduce observed patterns (toxigenic fraction, concentration of MC, biomass, nutrients and if available H2O2) for all cases, which constitutes support for the proposed mechanism. To explore lake management, we simulated single and dual nutrient (i.e. nitrogen and/or phosphorus) reduction, which predicts two types of outcomes. For lakes with nitrogen limitation at some time during the blooming season (e.g. Lake Erie) a phosphorus only reduction does not reduce MC concentration proportionally and may even increase it. Reducing phosphorus lowers biomass, which increases nitrogen and light availability and raises MC production and toxigenic fraction. For lakes with replete nitrogen (e.g. Lake Taihu) MC concentration is predicted to decrease. Here, further nitrogen availability will not increase MC production. These results advance mechanistic understanding of Microcystis strain ecology and toxin production and provide guidance for management.

Contribution of MALDI-TOF mass spectrometry and machine learning including deep learning techniques for the detection of virulence factors of Clostridioides difficile strains.

Clostridioides difficile (CD) infections are defined by toxins A (TcdA) and B (TcdB) along with the binary toxin (CDT). The emergence of the 'hypervirulent' (Hv) strain PR 027, along with PR 176 and 181, two decades ago, reshaped CD infection epidemiology in Europe. This study assessed MALDI-TOF mass spectrometry (MALDI-TOF MS) combined with machine learning (ML) and Deep Learning (DL) to identify toxigenic strains (producing TcdA, TcdB with or without CDT) and Hv strains. In total, 201 CD strains were analysed, comprising 151 toxigenic (24 ToxA+B+CDT+, 22 ToxA+B+CDT+ Hv+ and 105 ToxA+B+CDT-) and 50 non-toxigenic (ToxA-B-) strains. The DL-based classifier exhibited a 0.95 negative predictive value for excluding ToxA-B- strains, showcasing accuracy in identifying this strain category. Sensitivity in correctly identifying ToxA+B+CDT- strains ranged from 0.68 to 0.91. Additionally, all classifiers consistently demonstrated high specificity (>0.96) in detecting ToxA+B+CDT+ strains. The classifiers' performances for Hv strain detection were linked to high specificity (≥0.96). This study highlights MALDI-TOF MS enhanced by ML techniques as a rapid and cost-effective tool for identifying CD strain virulence factors. Our results brought a proof-of-concept concerning the ability of MALDI-TOF MS coupled with ML techniques to detect virulence factor and potentially improve the outbreak's management.

Vibrio cholerae Bacteremia: An Enigma in Cholera-Endemic African Countries.

Cholera is highly endemic in many sub-Saharan African countries. The bacterium Vibrio cholerae is responsible for this severe dehydrating diarrheal disease that accounts for over 100,000 deaths each year globally. In recent years, the pathogen has been found to invade intestinal layers and translocate into the bloodstream of humans. The non-toxigenic strains of V. cholerae (non-O1/O139), also known as NOVC, which do not cause epidemic or pandemic cases of cholera, are the major culprits of V. cholerae bacteremia. In non-cholera-endemic regions, clinical reports on NOVC infection have been noted over the past few decades, particularly in Europe and America. Although low-middle-income countries are most susceptible to cholera infections because of challenges with access to clean water and inappropriate sanitation issues, just a few cases of V. cholerae bloodstream infections have been reported. The lack of evidence-based research and surveillance of V. cholerae bacteremia in Africa may have significant clinical implications. This commentary summarizes the existing knowledge on the host risk factors, pathogenesis, and diagnostics of NOVC bacteremia.

Validation of a clinical assay for botulinum neurotoxins through mass spectrometric detection.

Botulism is a paralytic disease due to the inhibition of acetylcholine exocytosis at the neuromuscular junction, which can be lethal if left untreated. Botulinum neurotoxins (BoNTs) are produced by some spore-forming Clostridium bacteria. The current confirmatory assay to test for BoNTs in clinical specimens is the gold-standard mouse bioassay. However, an Endopep-MS assay method has been developed to detect BoNTs in clinical samples using benchtop mass spectrometric detection. This work demonstrates the validation of the Endopep-MS method for clinical specimens with the intent of method distribution in public health laboratories. The Endopep-MS assay was validated by assessing the sensitivity, robustness, selectivity, specificity, and reproducibility. The limit of detection was found to be equivalent to or more sensitive than the mouse bioassay. Specificity studies determined no cross-reactivity between the different serotypes and no false positives from an exclusivity panel of culture supernatants of enteric disease organisms and non-toxigenic strains of Clostridium. Inter-serotype specificity testing with 19 BoNT subtypes was 100% concordant with the expected results, accurately determining the presence of the correct serotype and the absence of incorrect serotypes. Additionally, a panel of potential interfering substances was used to test selectivity. Finally, clinical studies included clinical specimen stability and reproducibility, which was found to be 99.9% from a multicenter evaluation study. The multicenter validation study also included a clinical validation study, which yielded a 99.4% correct determination rate. Use of the Endopep-MS method will improve the capacity and response time for laboratory confirmation of botulism in public health laboratories.

An ultrasensitive genosensor for detection of toxigenic and non-toxigenic Clostridioides difficile based on a conserved sequence in surface layer protein coding gene

Clostridioides difficile (C. difficile) is the most common agent of antibiotic-associated diarrhea, leading to intestinal infection through the secretion of two major toxins. Not all strains of this bacterium are toxigenic, but some of them cause infection via their accessory virulence factors, such as surface layer protein (SlpA). SlpA is conserved in both toxigenic and non-toxigenic strains of C. difficile. In the present work, an amplification-free electrochemical genosensor was designed for the detection of the slpA gene. A glassy carbon electrode coated with gold nanoparticle-reduced graphene oxide nanocomposite was used as the working electrode, and its surface was modified using a simple thiolated linear oligonucleotide as the bioreceptor. Moreover, the hexaferrocenium tri[hexa(isothiocyanato) iron(III)] trihydroxonium (HxFc) complex was used as an intercalator, and its redox signal was recorded using differential pulse voltammetry. Scan rate studies indicated a quasi-reversible adsorption-controlled process for the HxFc complex. This genosensor showed high sensitivity with a limit of detection of 0.2 fM, a linear response range of 0.46–1900 fM, and a satisfactory specificity toward the synthetic slpA target gene. Also, the genosensor indicated responses in the mentioned linear range toward the genome extracted from either toxigenic or non-toxigenic strains of C. difficile.

Epidemiological Situation on Cholera in the Russian Federation in 2023 and Forecast for 2024

The paper presents an analysis and assessment of risks of complication of epidemiological situation regarding cholera in the Russian Federation and a forecast for 2024. It briefly characterizes the dynamics of the epidemic process around the world during the last decade (2013–2022). The forecast of cholera importation into the Russian Federation, due to activity of the epidemic process in endemic countries, has been confirmed. In 2023, two cases of cholera importation from India were reported. It was established that the toxigenic strains isolated from patients belonged to the currently dominant in the world “post-Haitian” group, including in India and Bangladesh, with the genotype ctxB7 tcpACIRS rtxA4a VSP-IIΔ0495-0512. Furthermore, non-toxigenic Vibrio cholerae O1 strains were isolated from samples of biological material from persons arriving from India, containing preCTX prophage and distinct from the strain (ctxAB– tcpAEТ–) isolated from a patient with acute intestinal infection (Zaporozhye Region, Melitopol). Nontoxigenic NAG vibrios were isolated from 13 patients with acute intestinal infections, which is 1.9 times more than in 2022. Regardless of importations, a strain of V. cholerae O1 (ctxB1+tcpAEТ) of the “pre-Haitian” group was isolated from a water sample of a surface reservoir. 52 non-toxigenic V. сholerae O1 strains were found on the territory of 11 constituent entities of the Russian Federation, which is 18.9 % more than in 2022. In 2024, epidemiological risks of cholera importation from endemic countries to any administrative territory of the Russian Federation remain. The risks of epidemic manifestations of cholera are especially high in the territories of the constituent entities of the Russian Federation which are under ongoing emergency, due to migration processes, and the impact of other risk-forming factors that contribute to an increase in the degree of contact of the population with water bodies contaminated with cholera vibrios. If epidemic foci of cholera are to emerge in a neighboring country, there will be a high probability of spread of this infection in the stated constituent entities of the Russian Federation and in other territories of southern Russia. In the absence of epidemic manifestations of cholera, the possibility of occasional detection of toxigenic O1 serogroup strains in water samples due to unidentified introductions from cholera-affected areas cannot be ruled out.

Presence of Zonula Occludens Toxin-Coding Genes among Vibrio parahaemolyticus Isolates of Clinical and Environmental Origin.

In recent studies, emphasis has been placed on the zonula occludens toxin (Zot) from the non-toxigenic Vibrio parahaemolyticus strain PMC53.7 as an agent inducing alterations in the actin cytoskeleton of infected Caco-2 cells and which appears as a relevant virulence factor. Universal zot primers were designed by the alignment of different types of zot gene and identification of conserved sequences to investigate the presence in diverse environmental and clinical V. parahaemolyticus isolates, in co-occurrence with virulence factors, such a hemolysins and secretion systems. The study screened a total of 390 isolates from environmental sources from Chile and Italy and 95 Chilean clinical isolates. The results revealed that around 37.2% of Chilean environmental strains and 25.9% of Italian strains, and 24.2% of clinical isolates carried the zot gene. The Zot-C2 cluster was present in 71.4% of Chilean environmental strains but absent in clinical isolates, while the Zot-C4 cluster was identified in 28.6% of environmental and 100% of clinical isolates. Understanding the role of zot in V. parahaemolyticus virulence is crucial, especially considering the risk associated with consuming diverse isolates from bivalves and the co-occurrence with virulence factors such as TDH, TRH or T3SS2.

Non-toxigenic Corynebacterium diphtheriae endocarditis: A cluster of five cases.

Classical toxin-mediated respiratory diphtheria has become less common because of widespread effective vaccination globally but invasive disease as a result of non-toxigenic strains of Corynebacterium diphtheriae is not prevented by vaccination and may result in severe disease, including infective endocarditis (IE). To describe the outbreak and subsequent investigation of a cluster of five cases of non-toxigenic C. diphtheriae endocarditis. A retrospective observational case series of five cases of non-toxigenic C. diphtheriae endocarditis identified in the rural West Coast district of the Western Cape province of South Africa between May 2021 and June 2021. Non-toxigenic C. diphtheriae IE had an aggressive clinical course with high mortality in this cohort. Only one of five patients survived to hospital discharge. The surviving patient received a prompt diagnosis with early surgical intervention but still had a complicated clinical course. Notably, only one case had a pre-existing risk factor for IE, namely a prosthetic valve. Whole genome sequencing of clinical isolates confirmed that all isolates were of the same novel sequence type of non-toxigenic C. diphtheriae but despite a thorough investigation no epidemiological link was ever found between the cases. Non-toxigenic strains of C. diphtheriae are less well known but may be highly virulent and cause severe invasive disease. This is the largest cluster of non-toxigenic C. diphtheriae IE ever described in South Africa and expands the body of literature on this unusual but possibly emerging infection.

Genomic surveillance of Clostridioides difficile transmission and virulence in a healthcare setting.

Clostridioides difficile infection remains a leading cause of hospital-associated diarrhea, despite increased antibiotic stewardship and transmission prevention strategies. This suggests a changing genomic landscape of C. difficile. Our study provides insight into the nature of prevalent C. difficile strains in a hospital setting and transmission patterns among carriers. Longitudinal sampling of surfaces and patient stool revealed that both toxigenic and nontoxigenic strains of C. difficile clade 1 dominate these two wards. Moreover, quantification of transmission in carriers of these clade 1 isolates underscores the need to revisit infection prevention measures in this patient group. We identified unique genetic signatures associated with virulence in this clade. Our data highlight the complexities of preventing transmission of this pathogen in a hospital setting and the need to investigate the mechanisms of in vivo persistence and virulence of prevalent lineages in the host gut microbiome.

Molecular characterization and phylogenetic analysis of the first Corynebacterium rouxii strains isolated in Brazil: a recent member of Corynebacterium diphtheriae complex

BackgroundCorynebacterium diphtheriae complex was formed by the species C. diphtheriae, Corynebacterium ulcerans and Corynebacterium pseudotuberculosis in the recent past. In addition to C. diphtheriae, C. ulcerans and C. pseudotuberculosis species can carry the tox gene, which encodes diphtheria toxin. Currently, three new species have been included in the complex: Corynebacterium rouxii, Corynebacterium silvaticum, and Corynebacterium belfantii. C. rouxii is derived from the ancient Belfanti biovar of C. diptheriae. We provide the complete genome sequences of two non-toxigenic strains C. rouxii isolated from a cat with a purulent infection in Brazil. The taxonomic status and sequence type, as well as the presence of resistance and virulence genes, and CRISPR-Cas system were additionally defined.ResultsThe genomes showed an average size of 2.4 Mb and 53.2% GC content, similar to the type strain of the species deposited in Genbank/NCBI. Strains were identified as C. rouxii by the rMLST database, with 95% identity. ANI and DDH in silico were consistent with values above the proposed cut-off points for species limit, corroborating the identification of the strains as C. rouxii. MLST analyses revealed a new ST, which differs from ST-537 only by the fusA allele. No horizontal transfer resistance gene was predicted in both genomes and no mutation was detected in the constitutive genes gyrA and rpoB. Some mutations were found in the seven penicillin-binding proteins (PBPs) detected. The tox gene was not found, but its regulatory gene dtxR was present. Among the predicted virulence genes are those involved in iron uptake and adherence, in addition to the DIP0733 protein involved in epithelial cell adhesion and invasion. The CRISPR-Cas type I-E system was detected in both genomes, with 16 spacer sequences each. Of them, half are unknown according to the databases used, indicating that there is an unexplored reservoir of corynebacteriophages and plasmids.ConclusionsThis is the first genomic study of C. rouxii reported in Brazil. Here we performed taxonomic analysis and the prediction of virulence factors. The genomic analyses performed in this study may help to understand the potential pathogenesis of non-toxigenic C. rouxii strains.

Microcystin aids in cold temperature acclimation: Differences between a toxic Microcystis wildtype and non-toxic mutant

For Microcystis aeruginosa PCC 7806, temperature decreases from 26 °C to 19 °C double the microcystin quota per cell during growth in continuous culture. Here we tested whether this increase in microcystin provided M. aeruginosa PCC 7806 with a fitness advantage during colder-temperature growth by comparing cell concentration, cellular physiology, reactive oxygen species damage, and the transcriptomics-inferred metabolism to a non-toxigenic mutant strain M. aeruginosa PCC 7806 ΔmcyB. Photo-physiological data combined with transcriptomic data revealed metabolic changes in the mutant strain during growth at 19 °C, which included increased electron sinks and non-photochemical quenching. Increased gene expression was observed for a glutathione-dependent peroxiredoxin during cold treatment, suggesting compensatory mechanisms to defend against reactive oxygen species are employed in the absence of microcystin in the mutant. Our observations highlight the potential selective advantages of a longer-term defensive strategy in management of oxidative stress (i.e., making microcystin) vs the shorter-term proactive strategy of producing cellular components to actively dissipate or degrade oxidative stress agents.

PA01 Crusted nodules in returning travellers

Abstract We present the cases of two brothers, aged 10 and 13 years, who, on returning from a 6-week holiday in Sri Lanka, presented to the emergency department with painful, pruritic crusted nodules. Both children were usually fit and well, and up to date with their childhood immunizations; the older brother had a background of mild eczema. On examination, there were multiple widespread 1–2 cm well-defined, superficial excoriated ulcers with overhanding crusted edges. These were present over the arms, legs, back and feet of the younger brother, and the lower legs and feet of the older brother. There was no history of prodromal illness, and they remained afebrile throughout, with no evidence of lymphadenopathy or systemic illness. Bacterial wound swabs demonstrated Corynebacterium diphtheriae. Real-time polymerase chain reaction confirmed the presence of TOX, followed by the Elek test, which demonstrated the expression of the diphtheria toxin, confirming the diagnosis of cutaneous diphtheria due to a toxigenic strain. Both children were treated empirically with intravenous flucloxacillin and clindamycin as inpatients. Both were clinically well and discharged home on oral clindamycin and co-amoxiclav for a total of 10 further days. Public Health was informed of this notifiable disease, with contact tracing and appropriate family screening performed. Our patients isolated appropriately and made a full recovery, with negative swabs. Historically, most cases of diphtheria have been caused by C. diphtheriae (a Gram-positive nonencapsulated, nonsporulating, nonmotile bacillus) with an incubation period of 2–7 days, although other strains, notably Corynebacterium ulcerans, become increasingly prevalent. Despite diphtheria being classically described as a respiratory illness, Public Health England data found that nearly two-thirds of toxigenic C. diphtheriae infections were cutaneous in presentation. Concurrent respiratory infection and cutaneous infection are rare. Either form can be caused by toxigenic or nontoxigenic strains; the former may result in toxic complications (such as myocarditis, polyneuritis, septic arthritis, osteomyelitis and death); however, these are rare in cutaneous diphtheria, even if TOX-positive. Systems review of our patients did not highlight any of these features in our patients. Our patients exemplify classic features of cutaneous diphtheria and raise an important reminder to consider diphtheria in patients returning from endemic areas, despite vaccination schedules being in place.

Biocontrol of Colletotrichum falcatum Causing Red Rot Disease of Sugarcane Using Non-toxigenic Aspergillus sp.

Red rot disease caused by Colletotrichum falcatum is a major production threat to several sugarcane varieties in Thailand. Biological control is an ecologically friendly alternative to manage the disease using microbial antagonism and associated metabolic products. In this study, four Aspergillus non-toxigenic strains (A37, A374, A400, and A561) were characterized using a genetic approach and evaluated for their antagonistic potential to suppress the growth of C. falcatum. The strain A561 had the maximum number of gene deletions, with 12 afl atoxin-producing genes being lost. In addition, the non-toxigenic characteristic of A561 was confi rmed using afl atoxin B1 (AFB1) enzyme-linked immunosorbent assay. A561 reduced the concentration of AFB1 by 98.57% (1.63 μg/kg) relative to the toxigenic control. The antagonistic activity of A561 was evaluated against C. falcatum using the competition plate method on potato dextrose agar (PDA) in vitro. The results revealed that A561 inhibited the mycelial growth of C. falcatum by 34.39%. In addition, 10% (v/v) culture fi ltrate of A561 on PDA produced mycelial inhibition of 53.21%. Non-toxigenic A561 had antifungal potential, suppressing the growth of C. falcatum.

Draft Genome Sequences and Genome Characterization of Three Toxigenic and Two Nontoxigenic Clostridioides difficile Clinical Isolates from Florida, USA.

Draft genome sequences of five Clostridioides difficile clinical isolates were obtained in Florida, USA. Three isolates, designated TGH29 (sequence type 1 [ST1]/clade 2), TGH79 (ST11/clade 5), and TGH91 (ST35/clade 1), contained toxin-encoding genes. The two nontoxigenic strains were classified as TGH114 (ST109/clade 4) and TGH132 (ST15/clade 1). Antimicrobial resistance determinants and plasmids were detected and putative prophages predicted in some isolates.

Cholera: Analysis and Assessment of Epidemiological Situation around the World and in Russia (2013–2022). Forecast for 2023

The aim of the review was to analyze and assess the epidemiological situation on cholera in the world and Russia in 2013–2022 and to make a forecast for 2023. Over the period of 2013–2022, 500 administrative territories affected by cholera were identified in various regions of 71 countries of Asia, Africa and America (the Caribbean region) with formation of 69 endemic foci in 16, 41 and 12 countries, respectively. In 2022, 1 209 301 cases of cholera were registered in 36 countries of the world. The intensity of epidemic process in Asian countries (Syria, Lebanon) increased. Unfavorable epidemiological situation on the African continent persisted. Epidemics and large outbreaks, which began in 2021–2022 due to emergency situations (ES) of social and natural character, continued. The prediction of the stability of the epidemiological situation on cholera in the territories of constituent entities of the Russian Federation (RF), given for 2022, has been confirmed. In 2022, 43 non-toxigenic strains of Vibrio cholerae О1 were isolated from surface water bodies, 8 V. cholerae nonO1/nonO139 strains – from humans. Similarity of those strains with genetically closely related ones isolated in the course of monitoring in previous years in Russia, Donetsk People’s Republic (DPR) and Zaporozhye Region was demonstrated. In 2023, the risks of importation of the infection into RF are retained. It is associated with the intensification of epidemic processes in Asian, African and Caribbean region countries. The extended border with Ukraine, to where importation of cholera from endemic countries is possible, contributes to increased degree of threat. Bioterrorism is also not excluded. The consequences of a possible cholera epidemic complication in DPR, Lugansk People’s Republic, Zaporozhye and Kherson Regions are exacerbated by social emergencies resulting in disruption of infrastructure, interruptions in water supply, etc. In the absence of implementation of the risks of importation of this infection on the territory of RF, a stable epidemiological situation on cholera will be retained. Detection of non-toxigenic V. cholerae O1 strains (including probability of clonal complexes formation), as well as strains of non-O1/non-O139 serogroups, which can be etiological factors of sporadic cases or outbreaks of diarrheal diseases, in surface water bodies is predicted.

Lateral flow immunoassay-based laboratory algorithm for rapid diagnosis of diphtheria.

Background: In industrialised countries diphtheria is a rare but still life-threatening disease with a recent increase in cases due to migration and zoonotic aspects. Due to the rarity of the disease, laboratory diagnosis of diphtheria is often carried out in central reference laboratories and involves the use of sophisticated equipment and specially trained personnel. The result of the diphtheria agent detection can usually be obtained after 5-6 days or more. Authors suggest a Lateral Flow Immunoassay (LFIA)-based laboratory algorithm for the diagnosis of diphtheria, which may render less time in issuing a result and could promote the testing be performed in laboratories closer to the patient. Methods: LFIA for diphtheria toxin (DT) detection was designed using a pair of monoclonal antibodies to receptor-binding subunit B of the DT, and validated with 322 corynebacterial cultures as well as 360 simulated diphtheria specimens. Simulated diphtheria specimens were obtained by spiking of human pharyngeal samples with test strains of corynebacteria. The simulated specimens were plated on selective tellurite agar and after 18-24 hours of incubation, grey/black colonies characteristic of the diphtheria corynebacteria were examined for the DT using LFIA. Results: The diagnostic sensitivity of the LFIA for DT detection on bacterial cultures was 99.35%, and the specificity was 100%. Also, the LFIA was positive for all pharyngeal samples with toxigenic strains and negative for all samples with non-toxigenic strains. For setting LFIA, a 6-hour culture on Elek broth was used; thus, under routine conditions, the causative agent of diphtheria could be detected within two working days after plating of the clinical specimen on the tellurite medium of primary inoculation. Conclusions: The availability of such a simple and reliable methodology will speed up and increase the accuracy of diphtheria diagnosis globally.

Effective Colonization by Nontoxigenic Clostridioides difficile REA Strain M3 (NTCD-M3) Spores following Treatment with Either Fidaxomicin or Vancomycin.

Colonization with nontoxigenic Clostridioides difficile strain M3 (NTCD-M3) has been demonstrated in susceptible hamsters and humans when administered after vancomycin treatment. NTCD-M3 has also been shown to decrease risk of recurrent C. difficile infection (CDI) in patients following vancomycin treatment for CDI. As there are no data for NTCD-M3 colonization after fidaxomicin treatment, we studied the efficacy of NTCD-M3 colonization and determined fecal antibiotic levels in a well-studied hamster model of CDI. Ten of 10 hamsters became colonized with NTCD-M3 after 5 days of treatment with fidaxomicin when NTCD-M3 was administered daily for 7 days after treatment discontinuation. The findings were nearly identical to 10 vancomycin-treated hamsters also given NTCD-M3. High fecal levels of OP-1118, the major fidaxomicin metabolite, and vancomycin were noted during treatment with the respective agents and modest levels noted 3 days after treatment discontinuation at the time when most of the hamsters became colonized. These findings support the ongoing development of NTCD-M3 for the prevention of recurrent CDI. IMPORTANCE NTCD-M3 is a novel live biotherapeutic, that has been shown in a Phase 2 clinical trial to prevent recurrence of C. difficile infection (CDI) when administered shortly after antibiotic treatment of the initial CDI episode. Fidaxomicin was not, however, in widespread use at the time this study was conducted. A large multi-center Phase 3 clinical trial is now currently in the planning stage, and it is anticipated that many patients eligible for this study will be treated with fidaxomicin. Since efficacy in the hamster model of CDI has predicted success in patients with CDI, we studied the ability of NTCD-M3 to colonize hamsters after treatment with either fidaxomicin or vancomycin.