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We conducted patient chart reviews and whole-genome sequencing of wound specimens containing presumptive Corynebacterium ulcerans from Vancouver, British Columbia, Canada, during July 2019-July 2023. Sequencing confirmed 8/14 isolates were C. ramonii and identified 2 distinct clusters. Molecular methods should be used to clinically differentiate potential toxin-producing Corynebacterium spp.

We reviewed Corynebacterium spp. infection cases reported in South Africa during 2015-2023. We analyzed 84 isolates from 83 patients with C. diphtheriae, as well as 1 C. belfantii and 3 C. ulcerans isolates. Among C. diphtheriae cases, we observed respiratory diphtheria (26/83 patients [31%]), endocarditis (14/83 [17%]), cutaneous diphtheria (22/83 [27%]), nonspecific respiratory illnesses (5/83 [6%]), and asymptomatic carriage (16/83 [19%]). The median patient age was 19 (range 0-88) years. Diphtheria-tetanus-pertussis vaccination was incomplete for 26% (5/19) or unknown for 68% (13/19) of children 0-9 years of age. C. diphtheriae was intermediately resistant to penicillin (82/84 [98%] isolates; MIC 0.5 μg/mL) but susceptible to erythromycin (83/84 [99%] isolates; MIC 0.25 μg/mL). Eighteen unique sequence types were identified, corroborating C. diphtheriae heterogeneity. Toxin-producing strains were detected among cutaneous and respiratory diphtheria cases, indicating all forms of disease require monitoring and prompt public health action to curb transmission.

The genus Corynebacterium is the largest genera among corynebacteria and has a range of species widely spread in ecological niches, some with epidemic potential and capable of causing fatal diseases. In recent years, due to the reclassifications and discoveries of new potentially toxin-producing species, microbiological identification and epidemiological control have been compromised, becoming possible only with sequencing techniques. Two bacterial strains isolated from a cat were identified by MALDI-TOF mass spectrometry as Corynebacterium diphtheriae and sent to the collaborating center of the Brazilian Ministry of Health for molecular identification and determination of toxigenicity potential, which were initially performed by multiplex PCR method. In addition, the antimicrobial susceptibility profile was determined according to BrCAST. Finally, for the final identification at the species level and effective epidemiological monitoring, the sequencing of the 16S rRNA and rpo B housekeeping genes was carried out. The isolates were identified as nontoxigenic C. diphtheriae strains by mPCR. Both strains were found susceptible to all antimicrobial agents. Although the identification at the species level was not possible through similarity analysis of  S rRNA and rpo B housekeeping genes, the phylogenetic analysis showed that the isolates belonged to the species Corynebacterium rouxii with a high value of reliability. This is the first report of the isolation of C. rouxii in Latin America. Molecular identification, whether by the MALDI-TOF mass spectrometry or PCR techniques, does not discriminate C. rouxii from C. diphtheriae , requiring gene sequencing and phylogenetic analysis for correct identification at the species level.

To determine differences in clinical characteristics of patients with bacteremia caused by Corynebacterium striatum, C. jeikeium, and other species of Corynebacterium, we retrospectively reviewed medical records of patients in Japan who had Corynebacterium bacteremia during January 2014–May 2020. Of the 115 records evaluated, 60 (52%) were cases of true bacteremia and 55 (48%) were cases of contamination. Proportions of true bacteremia cases caused by C. striatum (70%) and by C. jeikeium (71%) were significantly higher than those caused by other species of Corynebacterium (9%). These 2 organisms were commonly detected in blood cultures of patients with hematologic malignancies and neutropenia. The mortality rates at 90 days were 34% (C. striatum), 30% (C. jeikeium), and 0 (other species). Given the high mortality rates, assessing true bacteremia when C. striatum or C. jeikeium is detected in blood cultures, especially in patients with hematologic malignancy, is warranted.

Pituitary abscesses are an uncommon cause of pituitary lesions. A 77-year-old woman presented for elective resection of a presumed non-functioning pituitary macroadenoma in the context of a progressive left-sided visual field deficit. She proceeded to trans-sphenoidal resection of the pituitary lesion, with purulent fluid found upon opening the pituitary capsule. Culture of operative samples yielded Corynebacterium pseudodiphtheriticum , susceptible to penicillin. Following debridement, treatment with 10-weeks of directed antimicrobials achieved good clinical response. This is the first reported case of primary C. pseudodiphtheriticum infection of the central nervous system, representing a rare but important differential for a slow growing pituitary lesion.

Corynebacterium striatum ( C. striatum ) is a Gram-positive bacterium commonly colonizing the skin and mucosa in healthy individuals and hospitalized patients. Traditionally regarded as a contaminant, C. striatum is now increasingly recognized as a potential cause of clinical infections, especially after the coronavirus disease pandemic. It has emerged as a pathogen implicated in severe infections, including pneumonia, bacteremia, meningitis, artificial joint infections, abdominal infections, and endocarditis. C. striatum has been reported in lower respiratory tract infections, mostly as a conditioned pathogen in immunocompromised individuals, particularly in those with chronic structural lung diseases, such as chronic obstructive pulmonary disease, leading to severe pneumonia or exacerbation of the existing disease and high mortality. Additionally, C striatum has been implicated in the community-acquired pneumonia among immunocompetent individuals and nosocomial lung infections, with evidence of person-to-person transmission through caregivers. C. striatum may exhibit multidrug resistance. Vancomycin, alone or in combination, is currently considered the most effective treatment for C. striatum . This review highlights the epidemiological characteristics, drug resistance mechanisms, diagnostics approaches, and treatment options for C. striatum lower respiratory tract infections to enhance clinician awareness and improve patient management strategies.

We report a possible zoonotic case of severe diphtheria-like respiratory illness in Norway caused by a previously unreported toxigenic Corynebacterium ulcerans sequence type. This case highlights C. ulcerans as an emerging pathogen that can cause life-threatening disease. Clinicians should be aware of C. ulcerans infection, even in regions where diphtheria is rare.

Corynebacterium ulcerans is an emerging zoonotic pathogen which causes diphtheria-like infections. Although C. ulcerans is found in multiple domestic and wild animal species, most human cases are linked with pets. Our ability to decipher cross-host species transmission dynamics and to understand the emergence of clinically relevant clones (e.g., diphtheria toxin-positive) is currently hampered by a limited knowledge of C. ulcerans strain diversity and genome evolution. Here, we explore the genomic population structure and evolution of C. ulcerans with 582 isolates from diverse hosts and geographical locations. A newly developed core genome genotyping scheme captures the population structure of C. ulcerans both at deep and shallow phylogenetic levels, uncovering its main sublineages and offering high strain subtyping resolution for epidemiological surveillance. Additionally, we reveal the diversity and distribution of the diphtheria toxin gene ( tox ), and those of its associated mobile elements. Considering the entire Corynebacterium diphtheriae Species Complex, we find four diphtheria toxin families, five tox -prophage families, and a novel tox -carrying genetic element. We show that some toxin families are shared across Corynebacterium species, revealing tox -prophage cross-species transfer. Our work enhances knowledge on the ecology and evolution of C. ulcerans and provides a genomic framework for tracking the dissemination of emerging sublineages. This study reveals prior undetected transmission events of Corynebacterium ulcerans , suggesting pets play an intermediary role between wildlife and humans. Two main sublineages were identified, showing high positivity rates for the diphtheria toxin.

Background Corynebacterium is a widespread and abundant bacterial genus on human skin. Occasionally, corynebacteria are isolated from clinical specimens associated with infection. In this study, 56 bacterial isolates were examined. These isolates were obtained from 52 patients with diverse infections such as keratitis, osteitis/osteomyelitis, mastitis, (suspected) foreign body associated infections (spine, prosthetic joint), suspected meningitis, post-operative infections, among others. These isolates were identified as corynebacteria by MALDI-TOF mass spectrometry but could not be reliably assigned to a specific species. To resolve this issue, the isolates were genome-sequenced, and species identification was done with different approaches, including digital DNA–DNA hybridization, phylogenomic tree placement and Average Nucleotide Identity (ANI) calculations. A subset of 34 strains was further investigated by biochemical characterization and antimicrobial susceptibility testing (AST). Results The 56 isolates belonged to 28 distinct corynebacterial species. Species identification was particularly ambiguous for 13 isolates as the ANIs were below 95% to the closest identified reference genomes. Two isolates represented potentially novel species, since no close relative could be identified (ANI < 90%). The majority of isolates belonged to the Corynebacterium marquesiae/tuberculostearicum ( n  = 10) and Corynebacterium kroppenstedtii/parakroppenstedtii ( n  = 9) complexes. Biochemical tests and AST revealed species- and strain-level variability. AST demonstrated extensive antimicrobial resistance (AMR), particularly among C. marquesiae , C. tuberculostearicum , C. lehmanniae , C. hesseae and C. resistens , with resistances observed against penicillin, clindamycin, ciprofloxacin, and rifampin. Resistance was frequently associated with acquired AMR genes, such as erm(X) , tet(W) and genes encoding aminoglycoside-modifying enzymes. Among the tested antibiotics, clindamycin resistance was most common, detected in 23 of 34 tested strains (64.7%). Conclusions This study expands our knowledge of Corynebacterium isolates derived from clinical specimens, particularly those differing from well-characterized species. It underscores the extensive geno- and phenotypic variability within most Corynebacterium species and challenges current species boundary definitions. The extensive level of detected AMR may complicate treatment of underlying infections. However, it remains uncertain whether these isolates represent true infectious agents or contaminants derived from the skin of the patients.

Background Corynebacterium species are often regarded as blood culture contaminants, but they are increasingly recognized as true pathogens. However, their clinical significance, resistance patterns, and prognostic factors remain poorly defined. This study aimed to describe the clinical characteristics, antimicrobial resistance profiles, and factors associated with true bacteremia compared with isolates considered contaminants, as well as all-cause mortality. Methods We conducted a 15-year retrospective cohort study of adults with at least one Corynebacterium -positive blood culture at a tertiary-care university hospital in southern Thailand (2009–2024). Species identification was performed using MALDI-TOF MS from 2017 onward. True bacteremia was defined by clinical and microbiologic criteria. Multivariable logistic regression was used to identify independent predictors of true bacteremia, and Cox proportional hazards regression was applied to identify predictors of 30-day mortality. Results Among the 437 patients, 192 (44%) were classified as having true bacteremia. Independent predictors included hematologic malignancy (aOR 3.75; 95% CI: 1.40–10.73), central venous catheter use (aOR 2.39; 95% CI: 1.49–3.84), non-dialysis dependent chronic kidney disease (aOR 2.83; 95% CI: 1.11–7.66), and hypertension (aOR 1.92; 95% CI: 1.20–3.08). The 30-day all-cause mortality rate was significantly greater in true bacteremia patients (43.8% vs. 23.3%, p  < 0.001). In the Cox proportional hazards model, hematologic malignancy (aHR 2.32, 95% CI 1.35–4.00) and central venous catheter use (aHR 2.34, 95% CI 1.46–3.74) were identified as independent predictors of 30-day mortality. C. striatum was the most common species (29.5%), highly resistant to penicillin (96.7%) and clindamycin (98.4%), but universally susceptible to vancomycin Conclusion Nearly half of Corynebacterium -positive blood cultures represented true infections with high mortality. Vancomycin remains the most reliable empiric therapy. Species-level identification and susceptibility testing are essential for accurate diagnosis and management Clinical trial Not applicable.