Biology subjects

Badell-Ocando, E.

Publications and source records attributed to Badell-Ocando, E..

5 recordsLinked to original sources

bioRxiv2026

Modified Elek test improves in-vitro detection of diphtheria toxin

PurposeDiphtheria is caused by toxigenic strains of the Corynebacterium diphtheriae complex, mainly Corynebacterium diphtheriae and C. ulcerans. The diagnosis of diphtheria relies on detecting the diphtheria toxin (DT), for which Englers method of Eleks immunoprecipitation test is the gold standard. A recent optimization of Englers method was proposed by Melnikov and colleagues, showing higher sensitivity for C. ulcerans. The goal of our study was to test and adapt this optimized method, and to re-analyze apparent non-toxigenic tox gene bearing (NTTB) isolates from our collection. MethodsWe included 48 C. ulcerans, C. ramonii and C. diphtheriae isolates previously categorized as NTTB but for which no genetic explanation was found for the lack of DT expression. DT production was tested using Melnikovs method with further modifications made by us: i) increasing the antitoxin concentration; ii) using 5{degrees}C as the incubation temperature after 24h; and iii) modifying the layout of control and test strains on agar plates. Results35 of 38 C. ulcerans, 3 C. ramonii and 8 of 10 C. diphtheriae were found to be toxigenic. No genetic explanation was found regarding two non-toxigenic isolates (1 C. diphtheriae and 1 C. ulcerans), whereas for one C. diphtheriae, IS1132 was detected upstream of the tox gene. ConclusionOur modified implementation of Melnikovs Elek test improved our ability to detect diphtheria toxin production. Most isolates previously considered as NTTB but with no genetic explanation, were shown to be toxigenic using the novel method.

microbiology↗

bioRxiv2023

A global Corynebacterium diphtheriae genomic framework sheds light on current diphtheria reemergence

BackgroundDiphtheria, caused by Corynebacterium diphtheriae, reemerges in Europe since 2022. Genomic sequencing can inform on transmission routes and genotypes of concern, but currently, no standard approach exists to detect clinically important genomic features and to interpret emergence in the global C. diphtheriae population framework. MethodsWe developed the bioinformatics pipeline DIPHTOSCAN (available at https://gitlab.pasteur.fr/BEBP/diphtoscan) to extract from genomes of Corynebacteria of the diphtheriae species complex, medically relevant features including tox gene presence and disruption. We analyzed 101 human C. diphtheriae isolates collected in 2022 in metropolitan and overseas France (France-2022). To define the population background of this emergence, we sequenced 379 additional isolates (mainly from France, 2018-2021) and collated 870 publicly-available genomes. ResultsThe France-2022 isolates comprised 45 tox-positive (44 toxigenic) isolates, mostly imported, belonging to 10 sublineages (<500 distinct core genes). The global dataset comprised 245 sublineages and 33.9% tox- positive genomes, with DIPHTOSCAN predicting non-toxigenicity in 16.0% of these. 12% of the global isolates, and 43.6% of France-2022 ones, were multidrug resistant. Convergence of toxigenicity with penicillin and erythromycin resistance was observed in 2 isolates from France-2022. Phylogenetic lineages Gravis and Mitis contrasted strikingly in their pathogenicity-associated genes. ConclusionsThis work provides a bioinformatics tool and global population framework to analyze C. diphtheriae genomes, revealing important heterogeneities in virulence and resistance features. Emerging genotypes combining toxigenicity and first-line antimicrobial resistance represent novel threats. Genomic epidemiology studies of C. diphtheriae should be intensified globally to improve understanding of reemergence and spatial spread.

microbiology↗

bioRxiv2023

Corynebacterium of the diphtheriae complex in companion animals: clinical and microbiological characterization of 64 cases from France

ObjectivesCorynebacteria of the diphtheriae complex (Cdc) can cause diphtheria in humans and have been reported from companion animals. We aimed to describe animal infection cases caused by Cdc isolates. Methods18 308 animals (dogs, cats, horses and small mammals) with rhinitis, dermatitis, non-healing wounds and otitis were sampled in metropolitan France (August 2019 to August 2021). Data on symptoms, age, breed, and the administrative region of origin were collected. Cultured bacteria were analyzed for tox gene presence, for production of the diphtheria toxin, for antimicrobial susceptibility, and genotyped by multilocus sequence typing. ResultsC. ulcerans was identified in 51 cases, 24 of which were toxigenic. Rhinitis was the most frequent presentation (18/51). Eleven cases (6 cats, 4 dogs, 1 rat) were mono-infections. Large breed dogs, especially German Shepherds (9 of 28 dogs; p < 0.00001) were overrepresented. C. ulcerans isolates were susceptible to all tested antibiotics. tox-positive C. diphtheriae was identified in 2 horses. Last, 11 infections cases (9 dogs, 2 cats; mostly chronic otitis, and 2 sores) had tox-negative C. rouxii, a recently defined species. C. rouxii and C. diphtheriae isolates were susceptible to most antibiotics tested, and almost all of these infections were polymicrobial. ConclusionsMonoinfections with C. ulcerans point towards a primary pathogenic potential to animals. C. ulcerans represents an important zoonotic risk, and C. rouxii may represent a novel zoonotic agent. This case series provides novel clinical and microbiological data on Cdc infections, and underlines the need for management of animals and their human contacts. ImportanceWe report on the occurrence, clinical and microbiological characteristics of infections caused by members of the Corynebacteria of the diphtheriae complex (Cdc) in companion animals. This is the first study based on the systematic analysis of a very large animal cohort (18 308 samples), which provides data on the frequency of Cdc isolates in various types of clinical samples from animals. Awareness of this zoonotic bacterial group remains low among veterinarians and veterinary laboratories, among which it is often considered a commensal bacteria of animals. We suggest that in case of Cdc detection in animals, the veterinary laboratories should be encouraged to send the samples to a reference laboratory for analysis of the presence of the tox gene. This work is relevant to the development of guidelines in case of Cdc infections in animals, and underlines their public health relevance given the zoonotic transmission risk.

microbiology↗

bioRxiv2022

Genomic epidemiology of Corynebacterium diphtheriae in New Caledonia

ObjectivesAn increasing number of isolations of Corynebacterium diphtheriae has been observed in recent years in the archipelago of New Caledonia. We aimed to analyze the clinical and microbiological features of samples with C. diphtheriae. MethodsAll C. diphtheriae isolates identified in New Caledonia from May 2015 to May 2019 were included. For each case, a retrospective consultation of the patient files was conducted. Antimicrobial susceptibility phenotypes, tox gene and diphtheria toxin expression, biovar and the genomic sequence were determined. Core genome multilocus sequence typing (cgMLST), 7-gene MLST and search of genes of interest were performed from genomic assemblies. Results58 isolates were included, with a median age of patients of 28 years (range: 9 days to 78 years). Cutaneous origin accounted for 51 of 58 (87.9%) isolates, and C. diphtheriae was associated with Staphylococcus aureus and/or Streptococcus pyogenes in three quarters of cases. Half of cases came either from the main city Noumea (24%, 14/58) or from the sparsely populated island of Lifou (26%, 15/58). Six tox-positive isolates were identified, associated with recent travel to Vanuatu; 5 of these cases were linked and cgMLST confirmed recent transmission. Two cases of endocarditis in young female patients with a history of rheumatic fever involved tox-negative isolates. The 58 isolates were mostly susceptible to commonly used antibiotics. In particular, no isolate was resistant to the first-line molecules amoxicillin or erythromycin. Resistance to tetracycline was found in a genomic cluster of 17 (29%) isolates, 16 of which carried the tetO gene. There were 13 cgMLST sublineages, most of which were also observed in the neighboring country Australia. ConclusionsCutaneous infections may harbor non-toxigenic C. diphtheriae isolates, which circulate largely silently in non-specific wounds. The possible introduction of tox-positive strains from a neighboring island illustrates that diphtheria surveillance should be maintained in New Caledonia, and that immunization in neighboring islands must be improved. Genomic sequencing uncovers how genotypes circulate locally and across neighboring countries.

microbiology↗

bioRxiv2019

Carriage of a single strain of non-toxigenic Corynebacterium diphtheriae biovar Belfanti (Corynebacterium belfantii) in four patients with cystic fibrosis

Cystic fibrosis (CF) patients are commonly colonized by bacterial pathogens, which can induce persistent lung inflammation and may contribute to clinical deterioration. Colonization of CF patients and cross-transmission by Corynebacterium diphtheriae has not been reported so far. The aim of this article was to investigate the possibility of a cross transmission of C. diphtheriae biovar Belfanti between four patients of a CF center. C. diphtheriae biovar belfanti (now formally called C. belfantii) isolates were collected from four patients in a single CF care center over a 6 years period and analyzed by microbiological methods and whole genome sequencing. Epidemiological links among patients were investigated. Ten isolates were collected from 4 patients. Whole genome sequencing of one isolate from each patient showed that a single strain was shared among them. In addition, one patient had the same strain on two consecutive samplings nine months apart. The strain was non-toxigenic and was susceptible to most antimicrobial agents. Ciprofloxacin resistance was observed in one patient. Transmission of the strain among patients was supported by the occurrence of same-day visits to the CF center. This study demonstrates colonization of CF patients by C. diphtheriae biovar Belfanti (C. belfantii) and shows persistence and transmission of a unique strain during at least six years in a single CF patient care center.\n\nPrevious meeting presentationsThe information in this work was not previously presented in any meeting.\n\nAccession numbersThe genomic sequence data generated in this work were submitted to the European Nucleotide Archive and are available from the International Nucleotide Sequence Database Collaboration (NCBI/ENA/DDBJ) databases under project accession number PRJEB28372 and run data accession numbers ERR2757916 to ERR2757921.

microbiology↗