Molecular Assessment of Resistance to Clarithromycin in Helicobacter pylori Strains Isolated from Patients with Dyspepsia by Fluorescent In Situ Hybridization in the Center of Iran

Background and Aims

Helicobacter pylori is a common infectious bacterium mostly found in gastroduodenal diseases. The increased prevalence of clarithromycin-resistant H. pylori strains is a major challenge in the successful treatment of infections caused by this organism. The present study is aimed at detecting the clarithromycin resistance pattern of H. pylori strains isolated from gastric biopsies and evaluating point mutations of the 23S rRNA gene. Patients and methods. In the present descriptive cross-sectional study, 165 patients with gastrointestinal disorders, who were referred to the Endoscopy Center of Dr. Shariati Hospital of Isfahan, Iran, were enrolled from April to July 2018. H. pylori infection was diagnosed by culture, and susceptibility of the isolates to clarithromycin was assessed by the E-test. Minimum inhibitory concentration (MIC) values were obtained based on EUCAST recommendations. Also, fluorescence in situ hybridization (FISH) was used to determine point mutations associated with clarithromycin resistance.

Results

By using culturing, H. pylori was isolated from 50.3% (83/165) gastric biopsy specimens. The overall frequency of resistance to clarithromycin was 25.3% (21/83) by the E-test. In the resistance genotypic analysis, 19 isolates had mutations. The prevalence of A2143G and A2144G mutations was 68.4% (13/19) and 31.5% (6/19), respectively. A2143C mutation was not tracked in any isolate. Two isolates with MIC > 0.5 μg/mL had no mutations that could be related to other mechanisms of resistance.

Conclusion

As presented in the study, the high prevalence of clarithromycin-resistant H. pylori due to point mutations of the 23S rRNA gene indicates the necessity of revising the standard treatment regimen based on antibiotic susceptibility pattern of each region.

The oncogenic roles of bacterial infections in development of cancer

Initiation of cancer is interconnected with different factors like infections. It has been estimated that infections, particularly viruses, participate in about 20% of all cancers. Bacteria as the most common infectious agents are also reported to be emerging players in the establishment of malignant cells. Microbial infections are able to modulate host cell transformation for promoting malignant features through the production of carcinogenic metabolites participating in inflammation responses, disruption of cell metabolism, and integrity and also genomic or epigenetic manipulations. It seems that the best example of the role of bacteria in cancer promotion is Helicobacter pylori infection, which is related to gastric cancer. World Health Organization (WHO) describes bacterium as class I carcinogens. Several bacterial infections have been reported in association with prevalent cancers. In this review, we will summarize the role of known bacterial infections in the initiation of the main common cancers, which show high mortality in the world. Examining the microbiomes in cancer patients is important and necessary to better understand the pathogenesis of this disease and also to plan therapeutic interventions.

Evaluation of Clarithromycin Resistance Among Iranian Helicobacter pylori Isolates by E-Test and Real-Time Polymerase Chain Reaction Methods

Background

Helicobacter pylori is an important pathogen of human gastric mucosa. Antibiotic resistance, especially resistance to clarithromycin is a major factor for treatment failure of H. pylori infections. The main mechanism of clarithromycin resistance in these bacteria is related to point mutations in three different locations of 23S rRNA gene.

Objectives

The aims of this study were to evaluate the resistance rate to clarithromycin among local H. pylori isolates by the E-test method and to determine the profile of point mutation in 23S rRNA by real-time polymerase chain reaction (PCR) method.

Patients and Methods

Eighty biopsy samples were collected from dyspeptic patients by endoscopy during 2011 - 2012. All samples were homogenized immediately and cultured on supplemented brucella blood agar and incubated under microaerophilic conditions. Further biochemical tests and ureC gene PCR was done for H. pylori confirmation. The H. pylori OC1096 strain was used as the control strain, simultaneously. Frequency of clarithromycin resistance was determined by the E-test method based on the clinical and laboratory standard institute (CLSI) standards. Point mutation profile was determined by real-time PCR and further analysis of melting curve, amplicon sequencing was done continuously.

Results

From 80 biopsy samples, 20 positive H. pylori isolates were detected and confirmed by biochemical tests and PCR method. Overall, 21.7% of the H. pylori isolates, showed clarithromycin resistance phenotype by use of the E-test. Also, the minimal inhibitory concentration of clarithromycin was determined as ≥ 0.5 mg/L by the E-test method. Only point mutation in the location of A2143G with melting temperature of 54.7°C was observed in all resistant isolates.

Conclusions

This study showed that the frequency of H. pylori clarithromycin resistance in Iran is relatively high. Since clarithromycin is not commonly used in Iran for H. pylori eradication, the high rate of resistance could be related to cross-reactivity between other macrolides. Therefore, macrolide antibiotics must be prescribed with precaution in any case of treatment other than H. pylori infections. All resistant isolates showed A2143G mutation in 23S rRNA as the dominant pattern of point mutation at least in Tehran H. pylori isolates.

Primary Antibiotic Resistance to Helicobacter pylori Strains Isolated From Children in Northern Iran: A Single Center Study

Background:

Initial resistance to antibiotics is the main reason for the failure of Helicobacter pylori (H. pylori) eradication in children.

Objectives:

As we commonly face high antibiotic resistance rates in children, we aimed to determine the susceptibility of H. pylori to common antibiotics.

Patients and Methods:

In this cross-sectional in vitro study, 169 children younger than 14 years with clinical diagnosis of peptic ulcer underwent upper gastrointestinal endoscopy. Biopsy specimens from stomach and duodenum were cultured. In isolated colonies, tests of catalase, urease, and oxidase as well as gram staining were performed. After confirming the colonies as H. pylori, the antibiogram was obtained using disk diffusion method.

Results:

Culture for H. pylori was positive in 12.3% of the specimens, urease test in 21.3%, serological test in 18.9% and stool antigen test was positive in 21.9%. We could show high specificity but moderate sensitivity of both histological and H. pylori stool antigen tests to detect H. pylori. The overall susceptibility to metronidazole was 42.9%, amoxicillin 95.2%, clarithromycin 85.7%, furazolidone 61.9%, azithromycin 81.0%, and tetracycline 76.2% with the highest resistance to metronidazole and the lowest to clarithromycin.

Conclusions:

In our region, there is high resistance of H. pylori to some antibiotics including metronidazole and furazolidone among affected children. To reduce the prevalence of this antibiotic resistance, more controlled use of antibiotics should be considered in children.