Objective: To identify and analyze two strains of C. diphtheriae in Guangdong Province by combining whole genome sequencing with traditional detection methods. Methods: The C. diphtheriae was isolated from Guangzhou in 2010 and Zhuhai in 2020 respectively. Isolates were identified by API Coryne strips and MALDI-TOF-MS. Genomic DNA was sequenced by using Illumina. The assembly was performed for each strain using CLC software. J Species WS online tool was used for average nucleoside homology identification, then narKGHIJ and tox gene were detected by NCBI online analysis tool BLSATN. MEGA-X was used to build a wgSNP phylogenetic tree. Results: GD-Guangzhou-2010 was Belfanti and GD-Zuhai-2020 was Gravis. ANIb between GD-Guangzhou-2010 and C. belfantii was 99.61%. ANI between GD-Zhuhai-2020 and C. diphtheriae was 97.64%. BLASTN results showed that the nitrate reduction gene narKGHIJ and tox gene of GD-Guangzhou-2010 was negative, while GD-Zhuhai-2020 nitrate reduction gene narKGHIJ was positive. There were two obvious clades in wgSNP phylogenetic tree. The first clades included all Mitis and Gravis types strains as well as GD-Zhuhai-2020. The second clades contained all isolates of C.belfantii, C.diphtheriae subsp. lausannense and GD-guangzhou-2010. Conclusion: Two non-toxic C. diphtheriae strains are successfully isolated and identified. The phylogenetic tree suggests that GD-Guangzhou-2010 and GD-Zhuhai-2020 are located in two different evolutionary branches.
China/epidemiology* ; Corynebacterium ; Corynebacterium diphtheriae/genetics* ; Diphtheria/microbiology* ; Humans ; Nitrates ; Phylogeny

OBJECTIVETo clarify the diagnosis of one suspected case of diphtheria in Guangdong province by epidemiological analysis and etiologic detection.

METHODSOn July 6th 2010, the corynebacterium diphtheria was detected from the nasal secretions of one nasopharyngeal carcinoma patient in a college-town hospital in Guangzhou City, Guangdong Province. The patient and the close contacts were asked to participate in the epidemiological survey; and their nasopharyngeal swabs (3 samples) and the nasal secretions of the patient (1 sample) were collected. The bacteria of the samples were isolated and cultured by blood plate and agar loefflera. The smears of positive strains were dyed and identified by BioMerieux API Coryne biochemical card. Gene tox of β-Corynebacteriophage, Corynebacterium diphtheriae was tested by PCR method, the aliphatic acid was analyzed by gas chromatography method and the Corynebacterium diphtheriae (CMCC 38009) was selected as positive control.

RESULTSThe patient had not gone out, neither had been visited. The patient denied history of vaccines or the immunizations. From the survey on patient's family members and close contacts, no similar symptoms had been found. One strain of Corynebacterium diphtheriae was isolated from the patient's nasal secretions, Gram positive and shape diversified. After cultured by agar loefflera and Gram-dyed and Neisser-dyed, one end or both two ends of the strain showed typical metachromatic granule. API Coryne was identified to Corynebacterium diphtheriae mitis/belfanti (99.4%). The result of gas chromatography method also indicated Corynebacterium diphtheriae. No Corynebacterium diphtheriae was isolated from the nasopharyngeal swabs, neither of the patient nor of the close contacts. The gene tox of β-Corynebacteriophage, Corynebacterium diphtheriae was negative according to the PCR test.

CONCLUSIONThe isolated Corynebacterium diphtheriae did not produce toxin as there was no biological structure gene of toxin. The patient was a health carrier of nontoxic Corynebacterium diphtheriae.

China ; epidemiology ; Corynebacterium diphtheriae ; isolation & purification ; Diphtheria ; epidemiology ; microbiology ; Female ; Humans ; Middle Aged ; Nasopharynx ; microbiology ; Polymerase Chain Reaction ; methods

There is a rare case of an elderly diabetic with diabetic foot infection at Hainan General Hospital in September 2021, which was diagnosed as Corynebacterium diphtheriae infection incidentally on routine culture with conventional methods and molecular biological approaches, to aid in diagnosis in clinical practice. Owing to smear staining, Albert staining and VITEK 2 system, automated identification systems viz matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) confirmed combing with 16S ribosomal RNA (16S rRNA) gene has been used for the taxonomic classification of bacteria. Otherwise, toxin gene tox was done for diphtheria toxin synthesis. The isolate was Gram-stain-positive, rod-like arrangement with irregular thickness, with characteristic metachromatic granules, ferment most sugars and homology of 16S rRNA analyses with C. diphtheriae NCTC11397^T (MW682323.1) was greater than a 100% possibility, toxin gene tox was negative. The findings lay the foundation to clinical identify and trace of non-toxigenic C. diphtheriae. Moreover, this work provides insights into the non-toxigenic C.diphtheriae that contribute to recognized risk of non-toxigenic C.diphtheriae infections.
Aged ; Corynebacterium/genetics* ; Corynebacterium diphtheriae/genetics* ; Diabetes Mellitus ; Diabetic Foot ; Diphtheria/microbiology* ; Humans ; RNA, Ribosomal, 16S/genetics*