Bruno Marques1, Maria Manuel Donato2, Olga Cardoso3, Cristina Luxo3, António Martinho1, Nuno Almeida4. 1. Centro do Sangue e da Transplantação de Coimbra, Instituto Português do Sangue e da Transplantação, IP, Coimbra, Portugal. 2. CIMAGO, Faculty of Medicine, University of Coimbra, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal. Electronic address: mmdonato@fmed.uc.pt. 3. Laboratory of Microbiology, Faculty of Pharmacy and CIEPQPF, Department of Chemical Engineering, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal. 4. Faculty of Medicine, University of Coimbra, and Gastroenterology Department, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal.
Abstract
OBJECTIVES: Helicobacter pylori is one of the most prevalent global pathogens colonising an estimated 50% of the world's population. Although metronidazole (MTZ) is an important antibiotic playing a relevant role in various H. pylori eradication therapies, its frequent consumption results in an increased frequency of resistance with a consequent negative impact on treatment efficacy. Mutations on genes encoding NADPH nitroreductases, commonly known as rdxA gene (oxygen-insensitive) and frxA gene (flavinreductase) have been associated to H. pylori resistance to metrodinazole. The aim of this study was to evaluate the mutation profile of rdxA and frxA genes in a population of 38 H. pylori isolates with phenotypic patterns of susceptibility and resistance to this antibiotic. METHODS: Touchdown PCR with the purpose of amplifying rdxA and frxA genes in one PCR was used. Sequence data were made by pair-wise sequence alignment and were examined in terms of codons, and comparison was achieved regarding amino acids. RESULTS: Although repeated mutations occurred in positions 118, 131, 172 and 183 of rdxA and in positions 72, 73, 110, 126 and 193 of frxA, it must be highlighted that the mutations are widespread along these two genes in this population. Furthermore, six MTZ-resistant isolates did not present any mutation in the frxA gene. CONCLUSIONS: This work appears to confirm that mutations in rdxA and frxA alone are unable to explain MTZ resistance in H. pylori isolates and therefore additional mechanisms may exist and should be investigated.
OBJECTIVES:Helicobacter pylori is one of the most prevalent global pathogens colonising an estimated 50% of the world's population. Although metronidazole (MTZ) is an important antibiotic playing a relevant role in various H. pylori eradication therapies, its frequent consumption results in an increased frequency of resistance with a consequent negative impact on treatment efficacy. Mutations on genes encoding NADPH nitroreductases, commonly known as rdxA gene (oxygen-insensitive) and frxA gene (flavinreductase) have been associated to H. pylori resistance to metrodinazole. The aim of this study was to evaluate the mutation profile of rdxA and frxA genes in a population of 38 H. pylori isolates with phenotypic patterns of susceptibility and resistance to this antibiotic. METHODS: Touchdown PCR with the purpose of amplifying rdxA and frxA genes in one PCR was used. Sequence data were made by pair-wise sequence alignment and were examined in terms of codons, and comparison was achieved regarding amino acids. RESULTS: Although repeated mutations occurred in positions 118, 131, 172 and 183 of rdxA and in positions 72, 73, 110, 126 and 193 of frxA, it must be highlighted that the mutations are widespread along these two genes in this population. Furthermore, six MTZ-resistant isolates did not present any mutation in the frxA gene. CONCLUSIONS: This work appears to confirm that mutations in rdxA and frxA alone are unable to explain MTZ resistance in H. pylori isolates and therefore additional mechanisms may exist and should be investigated.
Authors: William R Jacobs; Wendy A Szymczak; Rajagopalan Saranathan; Michael H Levi; Alice R Wattam; Adel Malek; Emmanuel Asare; Daniel S Behin; Debra H Pan Journal: J Clin Microbiol Date: 2020-02-24 Impact factor: 5.948