Isolation and identification of a novel phage targeting clinical multidrug-resistant Corynebacterium striatum isolates.

Introduction: Over the past decade, Corynebacterium striatum (C. striatum), an emerging multidrug-resistant (MDR) pathogen, has significantly challenged healthcare settings, especially those involving individuals with weakened immune systems. The rise of these superbugs necessitates innovative solutions. Methods: This study aimed to isolate and characterize bacteriophages targeting MDR-C. striatum. Utilizing 54 MDR-C. striatum isolates from a local hospital as target strains, samples were collected from restroom puddles for phage screening. Dot Plaque and Double-layer plate Assays were employed for screening. Results: A novel temperate bacteriophage, named CSP1, was identified through a series of procedures, including purification, genome extraction, sequencing, and one-step growth curves. CSP1 possesses a 39,752 base pair circular double-stranded DNA genome with HK97-like structural proteins and potential for site-specific recombination. It represents a new species within the unclassified Caudoviricetes class, as supported by transmission electron microscopy, genomic evolutionary analysis, and collinearity studies. Notably, CSP1 infected and lysed 21 clinical MDR-C. striatum isolates, demonstrating a wide host range. The phage remained stable in conditions ranging from -40 to 55°C, pH 4 to 12, and in 0.9% NaCl buffer, showing no cytotoxicity. Discussion: The identification of CSP1 as the first phage targeting clinical C. striatum strains opens new possibilities in bacteriophage therapy research, and the development of diagnostic and therapeutic tools against pathogenic bacteria.

Mutational analysis in Corynebacterium stationis MFS transporters for improving nucleotide bioproduction.

Product secretion from an engineered cell can be advantageous for microbial cell factories. Extensive work on nucleotide manufacturing, one of the most successful microbial fermentation processes, has enabled Corynebacterium stationis to transport nucleotides outside the cell by random mutagenesis; however, the underlying mechanism has not been elucidated, hindering its applications in transporter engineering. Herein, we report the nucleotide-exporting major facilitator superfamily (MFS) transporter from the C. stationis genome and its hyperactive mutation at the G64 residue. Structural estimation and molecular dynamics simulations suggested that the activity of this transporter improved via two mechanisms: (1) enhancing interactions between transmembrane helices through the conserved "RxxQG" motif along with substrate binding and (2) trapping substrate-interacting residue for easier release from the cavity. Our results provide novel insights into how MFS transporters change their conformation from inward- to outward-facing states upon substrate binding to facilitate efflux and can contribute to the development of rational design approaches for efflux improvements in microbial cell factories. KEYPOINTS: • An MFS transporter from C. stationis genome and its mutation at residue G64 were assessed • It enhanced the transporter activity by strengthening transmembrane helix interactions and trapped substrate-interacting residues • Our results contribute to rational design approach development for efflux improvement.

A Case Report of Corynebacterium Tuberculostearicum Infection.

BACKGROUND: The goal was to report a rare case of lymphadenitis caused by Corynebacterium tuberculostearicum, and the laboratory's coping approach in the isolation and identification of this rare pathogen to improve the understanding of the disease. METHODS: Lymph node biopsy was performed in a patient with suspected tuberculous lymphadenitis, and the biopsy tissue was isolated and cultured. RESULTS: The culture was Gram positive Corynebacterium, which was identified as Corynebacterium tuberculostearicum by microbial mass spectrometry and 16S rRNA gene sequencing. Antimicrobial susceptibility test showed that the drug was sensitive to daptomycin, doxycycline, gentamicin, linezolid, vancomycin, and meropenem, but resistant to ciprofloxacin, clindamycin, erythromycin, rifampicin, compound sulfamethoxazole, ceftriaxone, and cefepime. CONCLUSIONS: This is a case of Corynebacterium tuberculostearicum infection. Case reports of Corynebacterium tuberculostearicum infection are relatively rare in China. Through case study, we can provide help for laboratory isolation, identification, clinical diagnosis, and treatment.

Novel Organism Verification and Analysis (NOVA) study: identification of 35 clinical isolates representing potentially novel bacterial taxa using a pipeline based on whole genome sequencing.

BACKGROUND: Reliable species identification of cultured isolates is essential in clinical bacteriology. We established a new study algorithm named NOVA - Novel Organism Verification and Analysis to systematically analyze bacterial isolates that cannot be characterized by conventional identification procedures MALDI-TOF MS and partial 16 S rRNA gene sequencing using Whole Genome Sequencing (WGS). RESULTS: We identified a total of 35 bacterial strains that represent potentially novel species. Corynebacterium sp. (n = 6) and Schaalia sp. (n = 5) were the predominant genera. Two strains each were identified within the genera Anaerococcus, Clostridium, Desulfovibrio, and Peptoniphilus, and one new species was detected within Citrobacter, Dermabacter, Helcococcus, Lancefieldella, Neisseria, Ochrobactrum (Brucella), Paenibacillus, Pantoea, Porphyromonas, Pseudoclavibacter, Pseudomonas, Psychrobacter, Pusillimonas, Rothia, Sneathia, and Tessaracoccus. Twenty-seven of 35 strains were isolated from deep tissue specimens or blood cultures. Seven out of 35 isolated strains identified were clinically relevant. In addition, 26 bacterial strains that could only be identified at the species level using WGS analysis, were mainly organisms that have been identified/classified very recently. CONCLUSION: Our new algorithm proved to be a powerful tool for detection and identification of novel bacterial organisms. Publicly available clinical and genomic data may help to better understand their clinical and ecological role. Our identification of 35 novel strains, 7 of which appear to be clinically relevant, shows the wide range of undescribed pathogens yet to define.

Corynebacterium mendelii sp. nov., a novel bacterium isolated from Adélie penguin oral cavity.

The taxonomic status of strain P5891T, isolated from an Adélie penguin beak swab, was investigated. Based on the 16S rRNA gene sequence, the strain was identified as a potentially novel Corynebacterium species, with the highest sequence similarities to Corynebacterium rouxii FRC0190T (96.7 %) and Corynebacterium epidermidicanis DSM 45586T (96.6 %). The average nucleotide identity values between strain P5891T and C. rouxii FRC0190T and C. epidermidicanis DSM 45586T were 68.2 and 69.2 %, respectively. The digital DNA-DNA hybridization values between strain P5891T and C. rouxii FRC0190T and C. epidermidicanis DSM 45586T were 23.7 and 21.4 %, respectively. Phylogenetic trees based on the 16S rRNA sequence placed strain P5891T in a separate branch with Corynebacterium canis 1170T and Corynebacterium freiburgense 1045T, while a phylogenomic tree based on the Corynebacterium species core genome placed the strain next to Corynebacterium choanae 200CHT. Extensive phenotyping and genomic analyses clearly confirmed that strain P5891T represents a novel species of the genus Corynebacterium, for which the name Corynebacterium mendelii sp. nov. is proposed, with the type strain P5891T (=CCM 8862T=LMG 31627T).

Preliminary comparative genomics analysis among Corynebacterium kroppenstedtii complex necessitates a reassessment of precise species associated with mastitis.

AIMS: This study aimed to characterize the first complete genome of Corynebacterium parakroppenstedtii and clarify the evolutionary relationship in the Corynebacterium kroppenstedtii complex (CKC) by using comparative genomics analysis. METHODS AND RESULTS: The genome of isolate yu01 from a breast specimen was sequenced, and 35 CKC genomes were collected. Analysis of 16S rRNA, rpoB, and fusA suggested ambiguous identification, whereas ANI analysis assigned isolate yu01 as Coryne. parakroppenstedtii. The fourth genospecies "Corynebacterium aliikroppenstedtii" was identified in CKC. Comparative genomics analysis suggested that the genomic arrangement in CKC was highly conserved. A total of 43 potential virulence genes and 79 species-specific genes were detected. Most genome-based phylogenetic analysis were incapable of resolving the interspecific evolutionary relationships among CKCs. A total of 20 core genes were found to be distinguishable in CKC. CONCLUSIONS: This study suggested the limited divergence and unavailability of normal single gene-based identification in CKC and questioned the precise species of strains associated with mastitis, identified as Coryne. kroppenstedtii in previous studies. The 20 genes showed potential to enhance the methods for the identification and epidemiological investigation of CKC.

Genomic and phenotypic analysis of a novel clinical isolate of Corynebacterium pyruviciproducens.

BACKGROUND: Corynebacterium pyruviciproducens is a recently described species of Corynebacterium. There are few reports on the microbiological characteristics of the new species, and there is a lack of reports on the genomic analysis of the species. RESULTS: This study involved a clinical isolate from the pus of a hospital patient with sebaceous gland abscesses. The clinically isolated strain was identified as C. pyruviciproducens strain WYJY-01. In this study, referring to Koch's postulates, we observed the pathological changes of animal models infected by intraperitoneal injection and subcutaneous injection of pure culture of the strain WYJY-01. Furthermore, the strain WYJY-01 was isolated and cultured again from animal models' subcutaneous abscess drainage fluid. Subsequently, the genomics of the strain WYJY-01 was analyzed. By comparing various gene databases, this study predicted the core secondary metabolite gene cluster of the strain WYJY-01, virulence factor genes carried by prophage, pathogenicity islands, and resistance islands. In addition, the genomes of C. pyruviciproducens strain WYJY-01, ATCC BAA-1742 T, and UMB0763 were analyzed by comparative genomics, and the differential genes of strain WYJY-01 were compared, and their functions were analyzed. CONCLUSION: The findings showed that the strain WYJY-01 had pathogenicity, supplementing the phenotype characteristics of C. pyruviciproducens. Meanwhile, this research revealed the possible molecular mechanism of the pathogenicity of the strain WYJY-01 at the gene level through whole genome sequence analysis, providing a molecular basis for further research.

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

BACKGROUND: Corynebacterium 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. RESULTS: The 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. CONCLUSIONS: This 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.

Corynebacterium oculi-related bacterium may act as a pathogen and carrier of antimicrobial resistance genes in dogs: a case report.

BACKGROUND: The genus Corynebacterium comprises well-known animal and human pathogens as well as commensals of skin and mucous membranes. Species formerly regarded as contaminants are increasingly being recognized as opportunistic pathogens. Corynebacterium oculi has recently been described as a human ocular pathogen but has so far not been reported in dogs. CASE PRESENTATION: Here we present two cases of infection with a novel Corynebacterium sp., a corneal ulcer and a case of bacteriuria. The two bacterial isolates could not be identified by MALDI-TOF MS. While 16 S rRNA gene (99.3% similarity) and rpoB (96.6% identity) sequencing led to the preliminary identification of the isolates as Corynebacterium (C.) oculi, whole genome sequencing revealed the strains to be closely related to, but in a separate cluster from C. oculi. Antimicrobial susceptibility testing showed high minimal inhibitory concentrations of lincosamides, macrolides, tetracycline, and fluoroquinolones for one of the isolates, which also contained an erm(X) and tet-carrying plasmid as well as a nonsynonymous mutation leading to an S84I substitution in the quinolone resistance determining region of GyrA. CONCLUSIONS: While the clinical signs of both dogs were alleviated by antimicrobial treatment, the clinical significance of these isolates remains to be proven. However, considering its close relation with C. oculi, a known pathogen in humans, pathogenic potential of this species is not unlikely. Furthermore, these bacteria may act as reservoir for antimicrobial resistance genes also in a One Health context since one strain carried a multidrug resistance plasmid related to pNG3 of C. diphtheriae.

Species- and strain-level diversity of Corynebacteria isolated from human facial skin.

BACKGROUND: Sequencing of the human skin microbiome revealed that Corynebacterium is an ubiquitous and abundant bacterial genus on human skin. Shotgun sequencing further highlighted the microbial "dark matter" of the skin microbiome, consisting of microorganisms, including corynebacterial species that were not cultivated and genome-sequenced so far. In this pilot project, facial human skin swabs of 13 persons were cultivated to selectively obtain corynebacteria. 54 isolates were collected and 15 of these were genome-sequenced and the pan-genome was determined. The strains were biochemically characterized and antibiotic susceptibility testing (AST) was performed. RESULTS: Among the 15 sequenced strains, nine different corynebacterial species were found, including two so far undescribed species, tentatively named "Corynebacterium vikingii" and "Corynebacterium borealis", for which closed genome sequences were obtained. Strain variability beyond the species level was determined in biochemical tests, such as the variable presence of urease activity and the capacity to ferment different sugars. The ability to grow under anaerobic conditions on solid agar was found to be species-specific. AST revealed resistances to clindamycin in seven strains. A Corynebacterium pseudokroppenstedtii strain showed additional resistance towards beta-lactam and fluoroquinolone antibiotics; a chromosomally located 17 kb gene cluster with five antibiotic resistance genes was found in the closed genome of this strain. CONCLUSIONS: Taken together, this pilot study identified an astonishing diversity of cutaneous corynebacterial species in a relatively small cohort and determined species- and strain-specific individualities regarding biochemical and resistance profiles. This further emphasizes the need for cultivation-based studies to be able to study these microorganisms in more detail, in particular regarding their host-interacting and, potentially, -beneficial and/or -detrimental properties.

Pangenome analysis of Corynebacterium striatum: insights into a neglected multidrug-resistant pathogen.

BACKGROUND: Over the past two decades, Corynebacterium striatum has been increasingly isolated from clinical cultures with most isolates showing increased antimicrobial resistance (AMR) to last resort agents. Advances in the field of pan genomics would facilitate the understanding of the clinical significance of such bacterial species previously thought to be among commensals paving the way for identifying new drug targets and control strategies. METHODS: We constructed a pan-genome using 310 genome sequences of C. striatum. Pan-genome analysis was performed using three tools including Roary, PIRATE, and PEPPAN. AMR genes and virulence factors have been studied in relation to core genome phylogeny. Genomic Islands (GIs), Integrons, and Prophage regions have been explored in detail. RESULTS: The pan-genome ranges between a total of 5253-5857 genes with 2070 - 1899 core gene clusters. Some antimicrobial resistance genes have been identified in the core genome portion, but most of them were located in the dispensable genome. In addition, some well-known virulence factors described in pathogenic Corynebacterium species were located in the dispensable genome. A total of 115 phage species have been identified with only 44 intact prophage regions. CONCLUSION: This study presents a detailed comparative pangenome report of C. striatum. The species show a very slowly growing pangenome with relatively high number of genes in the core genome contributing to lower genomic variation. Prophage elements carrying AMR and virulence elements appear to be infrequent in the species. GIs appear to offer a prominent role in mobilizing antibiotic resistance genes in the species and integrons occur at a frequency of 50% in the species. Control strategies should be directed against virulence and resistance determinants carried on the core genome and those frequently occurring in the accessory genome.

National public health response to an outbreak of toxigenic Corynebacterium diphtheriae among asylum seekers in England, 2022: a descriptive epidemiological study.

BACKGROUND: In July, 2022, an increase in diphtheria cases caused by toxigenic Corynebacterium diphtheriae (C diphtheriae) was reported among asylum seekers arriving by small boats to England. Rising case numbers presented challenges for case and contact management in initial reception centres, prompting changes to national guidance and implementation of population-based control measures. This study aimed to describe the outbreak of toxigenic C diphtheriae among asylum seekers arriving by small boats to England during 2022 by use of national surveillance data. METHODS: We undertook a descriptive epidemiological analysis of cases of toxigenic C diphtheriae among asylum seekers arriving by small boats to England during 2022, incorporating genomic sequencing data, antibiotic susceptibility testing results, and epidemiological data obtained through the UK Health Security Agency's national enhanced surveillance programme. Health Protection Teams conducted risk assessments, and operational data (including details regarding offer and uptake of antibiotics and vaccinations) were obtained from National Health Service partners supporting the intervention programme. FINDINGS: In 2022, C diphtheriae isolates from 86 asylum seekers arriving by small boats were submitted to the National Reference Laboratory for confirmation and testing. Toxigenic C diphtheriae was confirmed for 72 (84%) cases and one individual with typical diphtheritic lesions but from whom no C diphtheriae was isolated from clinical swabs was also included as a probable case, resulting in 73 cases of diphtheria. 71 (97%) were male, 39 (53%) were younger than 18 years, and 36 (49%) presented with cutaneous diphtheria. The prevalence of diphtheria was highest among Afghans (1·3%) compared with all other nationalities (<0·1%). Local antibiotic susceptibility testing identified six cases with a macrolide resistant strain. INTERPRETATION: The increase in diphtheria coincided with a high volume of asylum seekers arriving by small boats to England during 2022, and subsequently increased clinical awareness of the disease among this population. Long-term disruption to vaccination programmes in origin countries along with barriers to accessing health care along migrant routes puts asylum seekers arriving by small boats at risk of disease. With arrivals expected to continue in 2023, the UK Health Security Agency has recommended continuation of population-based control measures in England until October, 2023, subject to ongoing review. FUNDING: The UK Health Security Agency.

Corynebacterium lipophilum sp. nov., a lipophilic bacterium isolated from clinical breast specimens and emended description of the species Corynebacterium pilbarense.

Two isolates (MC-18T and MC-17D), representing the Gram-stain-positive, facultatively anaerobic, irregular rod-shaped, non-motile, and non-spore-forming actinobacteria, were isolated from clinical breast specimens in Guangzhou, China. The growth of the isolates is enhanced by supplementing 1% Tween-80 on Luria Bertani agar. Optimal growth of the isolates was observed at 37 °C, pH 7-8, and with 1% (w/v) NaCl on Columbia blood agar. Pairwise comparison of the 16S rRNA gene sequences revealed that isolates MC-18T and MC-17D shared the highest sequence similarities with Corynebacterium liangguodongii 2184T (96.9%), which were lower than the threshold value for species delineation (98.65%). Phylogenetic dendrograms based on the 16S rRNA gene, rpoB gene, and core genomes indicated that two isolates formed a distinct lineage within the genus Corynebacterium. The estimated dDDH, ANIb, ANIm, and AAI values between strain MC-18T and its closely related strains were below the threshold values generally considered for recognizing a new species. The genome DNA G + C contents of both the isolates MC-18T and MC-17D are 60.6%. The two isolates have virulence-related genes of the VF classes of adhesion and antiphagocytosis, and also contain the antimicrobial resistance genes ErmX, mtrA, rpoB2, and RbpA. The major fatty acids (> 10%) of isolates MC-18T and MC-17D were C16:0, C18:1 ω9c, C18:0 and summed feature 5 (anteiso-C18:0 and/or C18:2 ω6,9c). The main respiratory quinone of strain MC-18T was MK-8(H2), and the polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, three unidentified glycolipids, an unidentified aminolipid, and four unidentified phosphoglycolipids. The two isolates lack mycolic acids in the cell envelope. Based on the above findings, the two isolates are considered to represent a novel species of the genus Corynebacterium, for which the name Corynebacterium lipophilum sp. nov. is proposed, with isolate MC-18T (= NBRC 115144T = CCTCC AB 2020201T) as the type strain. An emended description of the Corynebacterium pilbarense is also provided.

Corynebacterium hylobatis sp. nov. and Corynebacterium lemuris sp. nov., two novel species of the genus Corynebacterium isolated from faeces of primates.

Two Gram-stain positive, aerobic, short-rod-shaped, catalase-positive, oxidase-negative and non-motile strains, designated YIM 101343T and YIM 101645T, were isolated from faeces of Hylobates hoolock and Lemur catta, respectively. The results of 16S rRNA gene analysis indicated that both represented members of the genus Corynebacterium, and they shared a similarity of 98.0 % with each other. Corynebacterium marinum DSM 44953T showed the highest similarity with both strains YIM 101343T (99.0 %) and YIM 101645T (97.3 %). The results of phylogenetic analysis based on 16S rRNA gene indicated that strain YIM 101343T formed a cluster with C. marinum DSM 44953T and Corynebacterium comes 2019T, strain YIM 101645T formed a cluster with Corynebacterium halotolerans YIM 70093T, and the two clusters were neighbours. The genomic size of strain YIM 101343T was 3068751 bp and that of strain YIM 101645T was 3169714 bp. The dDDH, ANI and AAI values among strains YIM 101343T, YIM 101645T and the closely related species indicated that the two isolates represented two different novel species. Both strains contained meso-diaminopimelic acid and short-chain mycolic acids, and the major menaquinones were MK-9(H2) and MK-8(H2). The major polar lipids of the two strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside. The major fatty acids (>10 %) of both strains were C16 : 0, summed feature 4 and C18 : 1ω9c, but C17 : 1 ω8c was only present as a major component in YIM 101645T . In addition, phenotypic and some chemotaxonomic characteristics of strains YIM 101343T, YIM 101645T and the closely related species were different. Thus, strains YIM 101343T and YIM 101645T should represent two novel species of the genus Corynebacterium, for which the names Corynebacterium hylobatis sp. nov. and Corynebacterium lemuris sp. nov. are proposed, respectively. The type strains are YIM 101343T (=DSM 45970T=CCTCC AB 2013221T) and YIM 101645T (=BCRC 16963T=CCTCC AB 2013281T=KCTC 39868T).

Clinical Characteristics of Corynebacterium ulcerans Infection, Japan.

Corynebacterium ulcerans is a closely related bacterium to the diphtheria bacterium C. diphtheriae, and some C. ulcerans strains produce toxins that are similar to diphtheria toxin. C. ulcerans is widely distributed in the environment and is considered one of the most harmful pathogens to livestock and wildlife. Infection with C. ulcerans can cause respiratory or nonrespiratory symptoms in patients. Recently, the microorganism has been increasingly recognized as an emerging zoonotic agent of diphtheria-like illness in Japan. To clarify the overall clinical characteristics, treatment-related factors, and outcomes of C. ulcerans infection, we analyzed 34 cases of C. ulcerans that occurred in Japan during 2001-2020. During 2010-2020, the incidence rate of C. ulcerans infection increased markedly, and the overall mortality rate was 5.9%. It is recommended that adults be vaccinated with diphtheria toxoid vaccine to prevent the spread of this infection.

Succession and determinants of the early life nasopharyngeal microbiota in a South African birth cohort.

BACKGROUND: Bacteria colonizing the nasopharynx play a key role as gatekeepers of respiratory health. Yet, dynamics of early life nasopharyngeal (NP) bacterial profiles remain understudied in low- and middle-income countries (LMICs), where children have a high prevalence of risk factors for lower respiratory tract infection. We investigated longitudinal changes in NP bacterial profiles, and associated exposures, among healthy infants from low-income households in South Africa. METHODS: We used short fragment (V4 region) 16S rRNA gene amplicon sequencing to characterize NP bacterial profiles from 103 infants in a South African birth cohort, at monthly intervals from birth through the first 12 months of life and six monthly thereafter until 30 months. RESULTS: Corynebacterium and Staphylococcus were dominant colonizers at 1 month of life; however, these were rapidly replaced by Moraxella- or Haemophilus-dominated profiles by 4 months. This succession was almost universal and largely independent of a broad range of exposures. Warm weather (summer), lower gestational age, maternal smoking, no day-care attendance, antibiotic exposure, or low height-for-age z score at 12 months were associated with higher alpha and beta diversity. Summer was also associated with higher relative abundances of Staphylococcus, Streptococcus, Neisseria, or anaerobic gram-negative bacteria, whilst spring and winter were associated with higher relative abundances of Haemophilus or Corynebacterium, respectively. Maternal smoking was associated with higher relative abundances of Porphyromonas. Antibiotic therapy (or isoniazid prophylaxis for tuberculosis) was associated with higher relative abundance of anerobic taxa (Porphyromonas, Fusobacterium, and Prevotella) and with lower relative abundances of health associated-taxa Corynebacterium and Dolosigranulum. HIV-exposure was associated with higher relative abundances of Klebsiella or Veillonella and lower relative abundances of an unclassified genus within the family Lachnospiraceae. CONCLUSIONS: In this intensively sampled cohort, there was rapid and predictable replacement of early profiles dominated by health-associated Corynebacterium and Dolosigranulum with those dominated by Moraxella and Haemophilus, independent of exposures. Season and antibiotic exposure were key determinants of NP bacterial profiles. Understudied but highly prevalent exposures prevalent in LMICs, including maternal smoking and HIV-exposure, were associated with NP bacterial profiles. Video Abstract.

A conserved uORF in the ilvBNC mRNA of Corynebacterium species regulates ilv operon expression.

Computational methods can be used to identify putative structured noncoding RNAs (ncRNAs) in bacteria, which can then be validated using various biochemical and genetic approaches. In a search for ncRNAs in Corynebacterium pseudotuberculosis, we observed a conserved region called the ilvB-II motif located upstream of the ilvB gene that is also present in other members of this genus. This gene codes for an enzyme involved in the production of branched-chain amino acids (BCAAs). The ilvB gene in some bacteria is regulated by members of a ppGpp-sensing riboswitch class, but previous and current data suggest that the ilvB-II motif regulates expression by a transcription attenuation mechanism involving protein translation from an upstream open reading frame (uORF or leader peptide). All representatives of this RNA motif carry a start codon positioned in-frame with a nearby stop codon, and the peptides resulting from translation of this uORF are enriched for BCAAs, suggesting that expression of the ilvB gene in the host cells is controlled by attenuation. Furthermore, recently discovered RNA motifs also associated with ilvB genes in other bacterial species appear to carry distinct uORFs, suggesting that transcription attenuation by uORF translation is a common mechanism for regulating ilvB genes.

Comparative whole-genome analysis of diphtheria toxin-producing Corynebacterium ulcerans isolates from sheltered cats in Osaka, Japan.

Diphtheria toxin-producing Corynebacterium ulcerans is a zoonotic pathogen that causes human diphtheria-like symptoms. After performing whole-genome analysis of the five isolates from sheltered cats in Osaka, Japan, we compared them with genome sequences of 25 strains of C. ulcerans from a public database. The five isolates from cats harbored 14 genes encoding possible virulence factors in diphtheria-toxin-producing C. ulcerans. These isolates also had diphtheria toxin gene-encoding prophage in their chromosome, although differences were found in other prophages possession. Whole-genome single-nucleotide polymorphism analysis showed that cats' isolates belonged to ST337 branch, as were strains from Japanese human patients, with 41 or more single-nucleotide polymorphisms variations. High-resolution single-nucleotide polymorphism analysis of C. ulcerans was sufficient to distinguish cats' isolates clearly as not different by conventional genotyping methods.

An unusual case of native aortic endocarditis due to Corynebacterium pseudodiphtheriticum.

Corynebacterium pseudodiphtheriticum, a Gram-positive rod belonging the oropharynx microbiota, is usually described in pulmonary infections, especially in immunocompromised patients. This paper describes a rare case of native aortic infectious endocarditis (IE) and reviews the literature on similar cases. A 62-year-old man with rheumatic fever since childhood was hospitalized for surgical treatment of a febrile IE due to C. diphtheriticum with a large vegetation (15.8 X 8.3 mm). MALDI-TOF-MS from strain isolated in positive blood cultures identified C. pseudodiphtheriticum (2.34), and 16S rRNA sequencing from the valve sample confirmed the identification. The summary of 25 cases shows that the outcome of an IE due to C. pseudodiphtheriticum is bad. The review of the literature shows that this agent found in blood cultures in a cardiovascular context deserves to be explored meticulously because an unfavorable prognosis is frequent.

Genomic Epidemiology of Corynebacterium diphtheriae in New Caledonia.

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, 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. 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 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. Cutaneous infections may harbor nontoxigenic C. diphtheriae isolates, which circulate largely silently in nonspecific 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. IMPORTANCE 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 tetO 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.