Yangzhou is located in the middle of Jiangsu province, which has a high stomach cancer incidence of 44.05/100000 in 2014 [28]. H. pylori infection is regarded as the major risk factor of stomach cancer, a long-term cohort study [29] from Taiwan, China showed that eradicating H. pylori can reduce gastric cancer incidence and mortality. Unfortunately, the high prevalence of H. pylori infection and the increasing antibiotic resistance constitute the main challenge for current treatment. The main reason for us to conduct this work is that a disturbing phenomenon was found that a large proportion of people failed to eradicate H. pylori during the follow-up investigation, local resistance analysis is urgently required.
First-line eradication treatment is important in China because the rate of H. pylori reinfection after successful treatment is low (1.5% per person-year) [30], while the global annual reinfection rate of H. pylori was 3.1% [31]. It suggests we should choose the most effective therapy to improve first-line eradication rate. Antibiotic resistance rate of H. pylori varies among different countries or regions. In Italy in 2016, resistance rate to clarithromycin was 35.9% [32], and rate in Korea was 43.7% [8]. The present study showed that the resistance to clarithromycin (41.0%) is slightly higher than that in Zhuanghe (31%) [33] and significantly higher than the reported rate (22.1%) in the study included a large number of strains from 13 provinces or cities in China [34]. The significantly higher rate of clarithromycin resistance in Yangzhou may be caused by the long-time and wide use in clinical practice which can promote the emergence of drug-resistant bacteria. In addition, unhealthy lifestyle (no handwashing before meals, sharing utensils, etc.) could lead to the transmission of H. pylori among the population as well [35, 36]. According to consensus recommendations [7], levofloxacin-containing regimen is generally suggested to be avoided as an initial treatment, but as an alternative for rescue therapy because of the high rate of drug resistance. Resistance rate to levofloxacin was 38.8% in Taiwan, China in 2019 [37], and 56% in an area of China with a high risk of gastric cancer [33]. It is the highest of levofloxacin resistance rate in our study, maybe due to the widely use of quinolones owing to respiratory and urogenital infections. Metronidazole is a 5-nitroimidazole drug that is widely used for general anaerobic infections worldwide. The rate of metronidazole resistance was found to be 38.8% in this work, which is lower than the average rate (61%) of China in a meta-analysis [38].
The prevalence of resistance to amoxicillin was low in this study, concerning with its low rate of adverse reactions, amoxicillin-containing bismuth quadruple therapy can be used as the preferred choice for H. pylori eradication therapy. In addition, high-dose dual therapy is becoming familiar to doctors for great efficacy and lower side effects. The study conducted by Song et al. reported that dual therapy (esomeprazole and amoxicillin four times daily) was non-inferior to, and even superior to triple plus bismuth therapy as first‐line H. pylori eradication treatment[39]. However, the findings are not yet consistent and remains to be confirmed with further studies. Tetracycline also presented a high sensitivity, and it is recommended to replace amoxicillin for people who are allergic to penicillin. Our study showed that 42.3% of the strains were resistant to at least two antibiotics. The main resistance patterns were clarithromycin + levofloxacin (14.3%), clarithromycin + metronidazole (9.8%), clarithromycin + levofloxacin + metronidazole (6.7%). In addition, we also find several quadruple resistance patterns, and no strains resistant to all five antibiotics tested.
The vacA gene is the main virulence factor of H. pylori, strains with vacA s1/m1 genotype are the most cytotoxic, followed by s1/m2, and s2/ m2 strains were virtually non-toxic [40]. VacA s1 allele was detected in all strains in our study and was predominant in s1/m2 and s1/m1, is similar to the study conducted by Wang et al [41]. The results suggests that the strains in Yangzhou are more pathogenic and more likely to cause clinical disease. However, our statistics showed that the vacA genotype had no association with any gastric diseases, maybe for the reason of a small sample, which needs to be explored in further studies.
Multivariate analysis showed that history of chronic superficial gastritis was associated with clarithromycin resistance. H. pylori is the major cause of chronic gastritis, long -term H. pylori infection and the formation of bacterial biofilms [42] may lead to antibiotic resistance. Subjects with an endoscopic diagnosis of peptic ulcer or cancer have a lower risk of resistance to clarithromycin, which is consistent with a previous study in France [43]. Levofloxacin resistance was significantly associated with alcohol consumption. It is possible that physicians do not prescribe levofloxacin to patients who drink alcohol because of a disulfiram-like reaction, which might contribute to a low levofloxacin resistance rate among drinkers. In addition, in our study, people with family history of first-degree relatives with gastric cancer have a lower possibility of resistance to levofloxacin, it cannot be well explained at this time and needs to be further clarified by other studies. Gastrointestinal symptoms were significantly associated with levofloxacin and any antibiotics resistance, due to these individuals were infected by H. pylori early but ignore it. Unfortunately, the vacA s1/m2 genotype has not been shown to be associated with antibiotic resistance, although it was found more frequently in resistant strains.
Our study has some limitations. Firstly, we only performed endoscopic screening program in two small towns of Yangzhou city and the participants in our study ranged from 32 to 75 years old, with 80.5% of the population aged 50 years and above, it may not be adequately reflective of the general population. Secondly, our study was conducted using gene chip technology to detect known mutation sites to determine H. pylori antibiotic resistance, which may underestimate the antibiotic resistance. In addition, there are no follow-up investigation on H. pylori eradication in positive populations, and we will further strengthen observations.