Conference abstract
Molecular characterization and genetic diversity of isoniazid-resistant strains of Mycobacterium tuberculosis clinical isolates in Cameroon
Pan African Medical Journal - Conference Proceedings. 2023:18(145).03
Oct 2023.
doi: 10.11604/pamj-cp.2023.18.145.2255
Archived on: 03 Oct 2023
Contact the corresponding author
Keywords: Tuberculosis, resistance, mutations, isoniazid, genetic diversity
Oral presentation
Molecular characterization and genetic diversity of isoniazid-resistant strains of Mycobacterium tuberculosis clinical isolates in Cameroon
Nono Vanessa Ninkeh1,&, Nantia Akono Edouard1, Donkeng Valerie2
1The University of Bamenda, Bamenda, Cameroon, 2Centre Pasteur du Cameroun, Yaoundé, Cameroun
&Corresponding author
Introduction: the emergence and widespread of isoniazid-resistant strains has greatly jeopardized tuberculosis management. Although approximately 85% of all isoniazid-resistant strains have mutations in the major isoniazid-resistant genes, their contributions differ across countries. Studying the resistance mechanisms and genetic diversity has implications for pathogenicity, transmissibility, identification of drug-target genes, and improving diagnosis. The objective was to understand better the mutation profile, mechanisms associated with isoniazid resistance, genetic diversity and transmission dynamics associated with isoniazid-resistant Mycobacterium tuberculosis isolates circulating in Cameroon
Methods: five hundred (500) isoniazid-resistant archived isolates were isolated from the Mycobacteriology unit of Centre Pasteur du Cameroun and analyzed. Bacteria cultured were realized using the BACTEC MGIT 960 system. Tubes that gave a positive fluorescent signal with the BACTEC MGIT 960 equipment were removed, checked for acid-fast-bacilli using Ziehl-Neelsen staining, and confirmed for Mycobacterium tuberculosis complex using the TB Ag MPT64 test. Genotypic drug susceptibility testing was performed on positive cultures and their phenotypic resistance was reconfirmed using the Genotype MTBDRplus assay and BACTEC MGIT SIRE kits respectively. The minimum inhibitory concentration (MIC) for the reconfirmed isolates was also tested.
Results: of the 500 isoniazid-resistant strains, 447 were Mycobacterium tuberculosis positives and 53 were negative. Out of the 356 clinical isolates to which the Genotype MTBDRplus assay was performed, S315T mutation was the most frequent (66%). Also, mutations at the inhA promoter region namely c-15t (26.1%), t-8c (12.1%), t-8a (1.69%), a-16g (0.56%) were identified. Additionally, 8.9% and 10.4% possessed both mutations at the S315T and inhA promoter regions(c-15t and t-8c) respectively. Nevertheless, 54 of the strains were susceptible to isoniazid. Among these isoniazid-susceptible isolates identified, 61.1% (33/54) were reconfirmed phenotypically resistant (0.1 μg/ml) and exhibited varying MIC.
Conclusion: this result revealed a prevalence of 15.2% isoniazid-resistant strains with unknown resistance mechanisms (lacking mutations at katG and inhA genes). It is therefore important to verify the presence/absence of mutants and other factors by whole-genome sequencing, which can detect uncommon isoniazid-resistance mutations in these strains and further investigate the diversity of isoniazid-resistant Mycobacterium tuberculosis strains and their transmission pattern.
Molecular characterization and genetic diversity of isoniazid-resistant strains of Mycobacterium tuberculosis clinical isolates in Cameroon
Nono Vanessa Ninkeh1,&, Nantia Akono Edouard1, Donkeng Valerie2
1The University of Bamenda, Bamenda, Cameroon, 2Centre Pasteur du Cameroun, Yaoundé, Cameroun
&Corresponding author
Introduction: the emergence and widespread of isoniazid-resistant strains has greatly jeopardized tuberculosis management. Although approximately 85% of all isoniazid-resistant strains have mutations in the major isoniazid-resistant genes, their contributions differ across countries. Studying the resistance mechanisms and genetic diversity has implications for pathogenicity, transmissibility, identification of drug-target genes, and improving diagnosis. The objective was to understand better the mutation profile, mechanisms associated with isoniazid resistance, genetic diversity and transmission dynamics associated with isoniazid-resistant Mycobacterium tuberculosis isolates circulating in Cameroon
Methods: five hundred (500) isoniazid-resistant archived isolates were isolated from the Mycobacteriology unit of Centre Pasteur du Cameroun and analyzed. Bacteria cultured were realized using the BACTEC MGIT 960 system. Tubes that gave a positive fluorescent signal with the BACTEC MGIT 960 equipment were removed, checked for acid-fast-bacilli using Ziehl-Neelsen staining, and confirmed for Mycobacterium tuberculosis complex using the TB Ag MPT64 test. Genotypic drug susceptibility testing was performed on positive cultures and their phenotypic resistance was reconfirmed using the Genotype MTBDRplus assay and BACTEC MGIT SIRE kits respectively. The minimum inhibitory concentration (MIC) for the reconfirmed isolates was also tested.
Results: of the 500 isoniazid-resistant strains, 447 were Mycobacterium tuberculosis positives and 53 were negative. Out of the 356 clinical isolates to which the Genotype MTBDRplus assay was performed, S315T mutation was the most frequent (66%). Also, mutations at the inhA promoter region namely c-15t (26.1%), t-8c (12.1%), t-8a (1.69%), a-16g (0.56%) were identified. Additionally, 8.9% and 10.4% possessed both mutations at the S315T and inhA promoter regions(c-15t and t-8c) respectively. Nevertheless, 54 of the strains were susceptible to isoniazid. Among these isoniazid-susceptible isolates identified, 61.1% (33/54) were reconfirmed phenotypically resistant (0.1 μg/ml) and exhibited varying MIC.
Conclusion: this result revealed a prevalence of 15.2% isoniazid-resistant strains with unknown resistance mechanisms (lacking mutations at katG and inhA genes). It is therefore important to verify the presence/absence of mutants and other factors by whole-genome sequencing, which can detect uncommon isoniazid-resistance mutations in these strains and further investigate the diversity of isoniazid-resistant Mycobacterium tuberculosis strains and their transmission pattern.
