Journal of Microbiology

Phenotypic and Genotypic Analysis of Clarithromycin-Resistant Helicobacter pylori from Bogotá D.C., Colombia: Alba A. Trespalacios , William Otero , Jorge E. Caminos , Marcela M. Mercado , Jenny Ávila , Liliana E. Rosero , Azucena Arévalo , Raúl A. Poutou-Piñales , David Y. Graham; J. Microbiol. 2013;51(4):448-452. Published online August 30, 2013; DOI: https://doi.org/10.1007/s12275-013-2465-6

Abstract: Resistance of Helicobacter pylori to clarithromycin is the most common cause of treatment failure in patients with H. pylori infections. This study describes the MICs and the presence of 23S rRNA mutations of H. pylori isolates from Bogotá, D.C., Colombia. H. pylori were isolated from gastric biopsies from patients with functional dyspepsia. Clarithromycin susceptibility was investigated by agar dilution and strains were considered resistant if the MIC was ≥1 μg/ml. DNA sequences of the 23S rRNA gene of strains resistant and sensitive to clarithromycin were determined to identify specific point mutations. Clarithromycin resistance was present in 13.6% of patients by agar dilution. The A2143G, A2142G and A2142C mutations were found in 90.5, 7.1, and 2.4% of H. pylori strains with resistance genotype.The resistant phenotype was associated with 23S rRNA resistance genotype in 85.7% of isolates. The point mutations in 23S rRNA were well correlated with MICs values for clarithromycin.

RNase G Participates in Processing of the 5′-end of 23S Ribosomal RNA: Woo-Seok Song , Minho Lee , Kangseok Lee; J. Microbiol. 2011;49(3):508-511. Published online June 30, 2011; DOI: https://doi.org/10.1007/s12275-011-1198-7

Abstract: In Escherichia coli, primary rRNA transcripts must be processed by a complex process in which several ribonucleases are involved in order to generate mature 16S, 23S, and 5S rRNA molecules. While it is known that RNase G, a single-stranded RNA-specific endoribonuclease encoded by the rng gene, plays an active role in the maturation of the 5′-end of 16S rRNA, its involvement in the maturation of the 5′-end of 23S rRNA remains unclear. Here we show that E. coli cells deleted for the rng gene accumulate the 23S rRNA precursor containing an extra 77 nucleotides at its mature 5′-end. In vitro cleavage assays show that RNase G cleaves synthetic RNA containing a sequence encompassing the 5′-end to 77 nucleotides upstream of mature 23S rRNA at two sites present in single-stranded regions. Our results suggest the involvement of RNase G in the processing of the 5′-region of 23S rRNA precursors.

Organization of Three rRNA (rrn) Operons from Sphingobium chungbukense DJ77: Sun-Mi Yeon , Beom-Soon Choi , Young-Chang Kim; J. Microbiol. 2008;46(6):697-703. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0193-0

Abstract: The nucleotide sequences of all three rRNA operons (rrnA, rrnB, and rrnC) of Sphingobium chungbukense DJ77 were determined. The three rrn operons have the same gene order (16S rRNA-tRNAIle-tRNAAla-23S rRNA-5S rRNA-tRNAfMet). The nucleotide sequences were identical over a 5,468 bp region spanning the 16S rRNA gene to the 5S rRNA gene. Variability was observed in the 5S rRNA-tRNAfMet spacer sequence of rrnB. The tRNAfMet gene sequences were identical except for two bases (T5794 and A5871 in rrnB, T5942 and A5956 in rrnA, but C5942 and G5956 in rrnC). Comparative sequence analyses of ribosomal RNA operons from DJ77 with those of the class Alphaproteobacteria, to which the genus Sphingobium belongs, reveal close evolutionary relationships with other members of the order Sphingomonadales.

Clarithromycin Resistance Prevalence and Icea Gene Status in Helicobacter Pylori Clinical Isolates in Turkish Patients with Duodenal Ulcer and Functional Dyspepsia: Peren H. Baglan , Gulendam Bozdayi , Muhip Ozkan , Kamruddin Ahmed , A. Mithat Bozdayi , Ali Ozden; J. Microbiol. 2006;44(4):409-416.; DOI: https://doi.org/2412 [pii]

Abstract: Clarithromycin resistance in Helicobacter pylori is a principal cause of failure of eradication therapies, and its prevalence varies geographically. The IceA gene is a virulence factor associated with clinical outcomes. The objective of this study was to determine the current state of clarithromycin resistance prevalence, and to investigate the role of iceA genotypes in 87 Turkish adult patients (65 with functional dyspepsia and 22 with duodenal ulcer). A2143G and A2144G point mutations were tested by PCR-RFLP for clarithromycin resistance. Among the patients in the study, 28 patients were tested by agar dilution as well. Allelic variants of the iceA gene were identified by PCR. A total of 24 (27.6%) strains evidenced one of the mutations, either A2143G or A2144G. IceA1 was found to be positive in 28 of the strains (32.2%), iceA2 was positive in 12 (13.8%) and, both iceA1 and iceA2 were positive in 22 (25.3%) strains. In conclusion, we discovered no relationships between iceA genotypes and functional dyspepsia or duodenal ulcer, nor between clarithromycin resistance and iceA genotypes. Clarithromycin resistance appears to be more prevalent in Turkish patients.

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