Corynebacterium diphtheriae, the agent of diphtheria, is a genetically diverse bacterial species. Although antimicrobial resistance has emerged against several drugs including first-line penicillin, ...the genomic determinants and population dynamics of resistance are largely unknown for this neglected human pathogen.
Here, we analyzed the associations of antimicrobial susceptibility phenotypes, diphtheria toxin production, and genomic features in C. diphtheriae. We used 247 strains collected over several decades in multiple world regions, including the 163 clinical isolates collected prospectively from 2008 to 2017 in France mainland and overseas territories.
Phylogenetic analysis revealed multiple deep-branching sublineages, grouped into a Mitis lineage strongly associated with diphtheria toxin production and a largely toxin gene-negative Gravis lineage with few toxin-producing isolates including the 1990s ex-Soviet Union outbreak strain. The distribution of susceptibility phenotypes allowed proposing ecological cutoffs for most of the 19 agents tested, thereby defining acquired antimicrobial resistance. Penicillin resistance was found in 17.2% of prospective isolates. Seventeen (10.4%) prospective isolates were multidrug-resistant (≥ 3 antimicrobial categories), including four isolates resistant to penicillin and macrolides. Homologous recombination was frequent (r/m = 5), and horizontal gene transfer contributed to the emergence of antimicrobial resistance in multiple sublineages. Genome-wide association mapping uncovered genetic factors of resistance, including an accessory penicillin-binding protein (PBP2m) located in diverse genomic contexts. Gene pbp2m is widespread in other Corynebacterium species, and its expression in C. glutamicum demonstrated its effect against several beta-lactams. A novel 73-kb C. diphtheriae multiresistance plasmid was discovered.
This work uncovers the dynamics of antimicrobial resistance in C. diphtheriae in the context of phylogenetic structure, biovar, and diphtheria toxin production and provides a blueprint to analyze re-emerging diphtheria.
Clinical, epidemiologic, and microbiologic analyses revealed emergence of 26 cases of Corynebacterium diphtheriae species complex infections on Réunion Island, France, during 2015-2020. Isolates were ...genetically diverse, indicating circulation and local transmission of several diphtheria sublineages. Clinicians should remain aware of the risk for diphtheria and improve diagnostic methods and patient management.
Corynebacteria of the
species complex (CdSC) can cause diphtheria in humans and have been reported from companion animals. We aimed to describe animal infection cases caused by CdSC isolates. A total ...of 18,308 animals (dogs, cats, horses, and small mammals) with rhinitis, dermatitis, nonhealing 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
gene presence, production of the diphtheria toxin, and antimicrobial susceptibility and were genotyped by multilocus sequence typing. Corynebacterium 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, and 1 rat) were monoinfections. Large-breed dogs, especially German shepherds (9 of 28 dogs;
< 0.00001), were overrepresented. C. ulcerans isolates were susceptible to all tested antibiotics.
positive C. diphtheriae was identified in 2 horses. Last, 11 infections cases (9 dogs and 2 cats; mostly chronic otitis and 2 sores) had
-negative C. rouxii, a recently defined species.
and C. diphtheriae isolates were susceptible to most antibiotics tested, and almost all of these infections were polymicrobial. Monoinfections with C. ulcerans point toward a primary pathogenic potential to animals. C. ulcerans represents an important zoonotic risk, and
may represent a novel zoonotic agent. This case series provides novel clinical and microbiological data on CdSC infections and underlines the need for management of animals and their human contacts.
We report on the occurrence and clinical and microbiological characteristics of infections caused by members of the CdSC 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 CdSC 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 commensal in animals. We suggest that in the case of CdSC detection in animals, the veterinary laboratories should be encouraged to send the samples to a reference laboratory for analysis of the presence of the
gene. This work is relevant to the development of guidelines in the case of CdSC infections in animals and underlines their public health relevance given the zoonotic transmission risk.
The early innate response after Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccination is poorly characterized but probably decisive for subsequent protective immunity against tuberculosis. ...Therefore, we vaccinated mice with fluorescent BCG strains in the ear dorsum, as a surrogate of intradermal vaccination in humans. During the first 3 days, we tracked BCG host cells migrating out of the dermis to the auricular draining lymph nodes (ADLNs). Resident skin dendritic cells (DCs) or macrophages did not play a predominant role in early BCG capture and transport to ADLNs. The main BCG host cells rapidly recruited both in the dermis and ADLNs were neutrophils. Fluorescent green or red BCG strains injected into nonoverlapping sites were essentially sheltered by distinct neutrophils in the ADLN capsule, indicating that neutrophils had captured bacilli in peripheral tissue and transported them to the lymphoid organ. Strikingly, we observed BCG-infected neutrophils in the lumen of lymphatic vessels by confocal microscopy on ear dermis. Fluorescence-labeled neutrophils injected into the ears accumulated exclusively into the ipsilateral ADLN capsule after BCG vaccination. Thus, we provide in vivo evidence that neutrophils, like DCs or inflammatory monocytes, migrate via afferent lymphatics to lymphoid tissue and can shuttle live microorganisms. (Blood. 2005;106: 1843-1850)
We describe the development of a multilocus sequence typing (MLST) scheme for Corynebacterium diphtheriae, the causative agent of the potentially fatal upper respiratory disease diphtheria. Global ...changes in diphtheria epidemiology are highlighted by the recent epidemic in the former Soviet Union (FSU) and also by the emergence of nontoxigenic strains causing atypical disease. Although numerous techniques have been developed to characterize C. diphtheriae, their use is hindered by limited portability and, in some instances, poor reproducibility. One hundred fifty isolates from 18 countries and encompassing a period of 50 years were analyzed by multilocus sequence typing (MLST). Strain discrimination was in accordance with previous ribotyping data, and clonal complexes associated with disease outbreaks were clearly identified by MLST. The data produced are portable, reproducible, and unambiguous. The MLST scheme described provides a valuable tool for monitoring and characterizing endemic and epidemic C. diphtheriae strains. Furthermore, multilocus sequence analysis of the nucleotide data reveals two distinct lineages within the population of C. diphtheriae examined, one of which is composed exclusively of biotype belfanti isolates and the other of multiple biotypes.
Leptospirosis is a widespread zoonosis caused by pathogenic Leptospira interrogans that are transmitted by asymptomatic infected rodents. Leptospiral lipoproteins and LPS have been shown to stimulate ...murine cells via TLRs 2 and 4. Host defense mechanisms remain obscure, although TLR4 has been shown to be involved in clearing Leptospira. In this study, we show that double (TLR2 and TLR4) knockout (DKO) mice rapidly died from severe hepatic and renal failure following Leptospira inoculation. Strikingly, the severe proinflammatory response detected in the liver and kidney from Leptospira-infected DKO mice appears to be independent of MyD88, the main adaptor of TLRs. Infection of chimeric mice constructed with wild-type and DKO mice, and infection of several lines of transgenic mice devoid of T and/or B lymphocytes, identified B cells as the crucial lymphocyte subset responsible for the clearance of Leptospira, through the early production of specific TLR4-dependent anti-Leptospira IgMs elicited against the leptospiral LPS. We also found a protective tissue compartmentalized TLR2/TLR4-mediated production of IFN-gamma by B and T lymphocytes, in the liver and kidney, respectively. In contrast, the tissue inflammation observed in Leptospira-infected DKO mice was further characterized to be mostly due to B lymphocytes in the liver and T cells in the kidney. Altogether these findings demonstrate that TLR2 and TLR4 play a key role in the early control of leptospirosis, but do not directly trigger the inflammation induced by pathogenic Leptospira.
Epidemiology of diphtheria in the southwestern Indian Ocean is poorly documented. We analyzed 14 cases of infection with toxigenic Corynebacterium diphtheriae reported during 2007-2015 in Mayotte, a ...French department located in this region. Local control of diphtheria is needed to minimize the risk for importation of the bacterium into disease-free areas.
An 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. All 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,
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. Fifty-eight 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
-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
-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
gene. There were 13 cgMLST sublineages, most of which were also observed in the neighboring country Australia. Cutaneous infections may harbor nontoxigenic C. diphtheriae isolates, which circulate largely silently in nonspecific wounds. The possible introduction of
-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.
The analysis of C. diphtheriae from the tropical archipelago of New Caledonia revealed a high genetic diversity with sublineages that may be linked to Polynesia, Australia, or metropolitan France. Genomic typing allowed confirming or excluding suspected transmission events among cases and contacts. A highly prevalent tetracycline-resistant sublineage harboring the
gene was uncovered. Toxigenic isolates were observed from patients returning from Vanuatu, showing the importance of improving vaccination coverage in settings where it is insufficient. This study also illustrates the importance for diphtheria surveillance of the inclusion of isolates from cutaneous sources in addition to respiratory cases, in order to provide a more complete epidemiological picture of the diversity and transmission of C. diphtheriae.
The C-type lectin dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) mediates the innate immune recognition of microbial carbohydrates. We investigated the ...function of this molecule in the host response to pathogens in vivo, by generating mouse lines lacking the DC-SIGN homologues SIGNR1, SIGNR3, and SIGNR5. Resistance to Mycobacterium tuberculosis was impaired only in SIGNR3-deficient animals. SIGNR3 was expressed in lung phagocytes during infection, and interacted with M. tuberculosis bacilli and mycobacterial surface glycoconjugates to induce secretion of critical host defense inflammatory cytokines, including tumor necrosis factor (TNF). SIGNR3 signaling was dependent on an intracellular tyrosine-based motif and the tyrosine kinase Syk. Thus, the mouse DC-SIGN homologue SIGNR3 makes a unique contribution to protection of the host against a pulmonary bacterial pathogen.
Diphtheria is a re-emerging disease in resource-rich settings. We here report three cases of cutaneous diphtheria diagnosed and managed in our infectious disease department and discuss the ...determinants of its re-emergence. Migration, travel and vaccine scepticism are key factors not only for diphtheria re-emergence, but for the future of most preventable diseases.
PDF
