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Identification of Enterotoxigenic Bacteroides Fragilis in Patients With Diarrhea: A Study Targeting 16S Rrna, Gyrb and Nanh Genes Publisher Pubmed



Amiri R1 ; Norouzbabaei Z2 ; Kalali N1 ; Ghourchian S1 ; Yaseri M3 ; Abdollahi A4 ; Douraghi M1
Authors
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Authors Affiliations
  1. 1. Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
  2. 2. Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
  3. 3. Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
  4. 4. Department of Pathology, Imam Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran

Source: Anaerobe Published:2022


Abstract

Objectives: We aimed to identify the enterotoxigenic Bacteroides fragilis (ETBF) and bft subtypes among patients with diarrhea. In addition, we assessed whether DNA gyrase subunit B (gyrB) and neuraminidase (nanH) genes are useful determinants for identification of B. fragilis compared to 16S rRNA sequencing as a reference method. Methods: The 530 fecal specimens were cultured on BBE agar. The colonies which supposed to be a member of B. fragilis group were subjected to 16S rRNA gene sequencing and PCR assays targeting the Bacteroides fragilis group (BFG), gyrB and nanH. The B. fragilis toxin (bft) gene and its subtype was detected by PCR. The specificity of PCR assays was calculated considering the 16S rRNA gene sequencing as the reference method. Results: A total of 111 Gram-negative anaerobic coccobacilli were isolated from 530 fecal specimens using BBE agar. Of the 111 isolates, 100 (90.09%) were assumed to be a member of Bacteroides fragilis group as they yielded an amplicon through PCR using the group-specific primers (Bfra-F/g-Bfra-R). However, only 28 isolates out of 100 were definitively identified as species of Bacteroides using16S rRNA gene sequencing; of which 15 isolates were B. fragilis and the remaining 13 isolates were identified as B. thetaiotaomicron (n = 6), Parabacteroides distasonis (n = 3), B. vulgatus (Phocaeicola vulgatus) (n = 1), B. ovatus (n = 1), B. congonensis (n = 1) and B. nordii (n = 1). Among the 15 isolates of B. fragilis, 4 were found to be ETBF. Compared to the reference method, the specificity and accuracy of the PCR targeting gyrB gene (64.7% and 65%) was higher than of nanH (36.4% and 46%, respectively. Conclusions: This study demonstrated that more than one-fourth of B. fragilis isolates harbored bft gene and less than 1% of patients with diarrhea harbored ETBF. The slight agreement between the PCR assays -already used for identification of B. fragilis which targeting gyrB or nanH - and 16S rRNA gene sequencing as the reference method was noted. © 2022 Elsevier Ltd
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