Helicobacter pylori culture and antimicrobial resistance in Iran
http://www.100md.com
《美国医学杂志》
1 Department of Gastroenterology, Children Medical Centre, Tehran University of Medical Science, Tehran, Iran
2 Gilan University of Medical Science, Iran
Objective. Helicobacter pylori is considered as an important etiologic factor in pathogenesis of peptic ulcer disease, chronic gastritis and gastric cancer. To eradicate this micro-organism, numerous regimens containing various antimicrobial agents have been suggested. However, H pylori antimicrobial resistance is a leading factor to treatment failure and recurrence of the disease. The aim of the study was to evaluate the prevalence of H pylori resistance to metronidazole, clarithromycin, tetracycline, amoxicillin, erythromycin and furazolidone in authors pediatric patients. Methods. Antral biopsy of all pediatric patients with negative history of receiving anti-H pylori regimen and endoscopic findings of nodular gastritis or peptic ulcer without previous history of NSAID consumption, burning and trauma were performed for H pylori histology, urease test and culture. All positive cultures were tested for antimicrobial susceptibility. Results. Twenty four patients (14 male and 10 female) between 3.5 and 14 years of age were culture positive. 54.16% of the isolates were resistant to metronidazole, 8.33% to amoxicillin, 4.16% to erythromycin and 4.16% to clarithromycin. None of authors patients were resistant to tetracycline and furazolidone. Conclusion . H. pylori antimicrobial resistance could be a major contributor to failure of H pylori eradication. Continuous prospective surveillance of H. Pylori is essential. Moreover, culture and antimicrobial susceptibility test is recommended for resistant cases after the first failure to therapy.
Keywords: H. Pylori, Drug resistance; Pediatric; Endoscopy
Helicobacter Pylori is a gram negative, spiral, flagellate bacillus that naturally colonizes human, living in gastric mucus. The 20% prevalence of infection with H. Pylori among adolescents in United States pales in comparison to infection rates exceeding 90% by 5 years of age in parts of the developing countries.[1] H. Pylori is the etiology of peptic ulcer disease, gastritis, gastric mucosa-associated lymphoid-tissue lymphoma and gastric adenocarcinoma.[2],[3] Eradication of infection heals the active ulcers in long term, and leads to reduction in ulcer recurrence and attendant complications.[4],[5],[6]
Numerous regimens of several antimicrobial agents are suggested to eradicate the bacterium. Among them, triple therapy containing a proton pump inhibitor or bismuth and two antibiotics, which are usually among metronidazole, amoxicillin, tetracycline or clarithromycin, for 2 weeks are applied widely.[7] However, it is difficult to eradicate H. Pylori due to emergence of antimicrobial resistant strains. Antibiotic resistance varies widely between geographical regions and among subgroups within a study population.[8] In a study performed in Korea, resistance rate to metronidazole and clarithrimycin was reported as 40.6% and 5.9% respectively.[9] Another study found that 45% of the isolates were resistant to metronidazole and 41% to clarithromycin in United States.[10] Kalach et al reported that 43% and 21% of his study participants were primarily resistant to metronidazole and clarithromycin respectively in France.[6] And a large prospective surveillance in Germany showed primary metronidazole and clarithromycin resistance rates of 26.2% and 2.2% respectively.[11]
It is essential to be aware of the local antibiotic resistance rate to be able to prescribe the proper regimen to eradicate H. Pylori . On the other hand, there is little literature on H. Pylori antimicrobial resistance in Middle East countries. Therefore, the authors undertook this study to prospectively evaluate H. Pylori susceptibility to the current antimicrobial agents used to eradicate this bacterium in our pediatric patients.
Materials and Methods
A prospective study was conducted. All patients ￡ 14 years old with upper gastrointestinal symptoms including recurrent abdominal pain, nausea, vomiting and the like referring to "Children Medical Centre" between Mar 2002 and Mar 2003 underwent esophagogastroduodenoscopy. The endoscopy was performed by a pediatric gastroenterologist. Those with negative history of receiving anti- H. Pylori regimen and endoscopic findings of nodular gastritis or peptic ulcer without previous history of NSAID consumption, burning and trauma were eligible to participate in their study. Single antral biopsy specimen was obtained from each participant. Biopsy specimens were kept in normal saline at 4oC and transported to the Health Faculty of Tehran University of Medical Science within 24 hours for culture. The specimens were inoculated onto Mueller-Hinton blood agar plates which were supplemented with 10 mg/L vancomycin, 50 μg/L polymyxin B and 5 mg/L trimethoprim to provide a selective media for H. pylori . The plates were incubated at an atmosphere of 5% CO2 at 37oC and relative humidity of 90% for 3 to 7 days. H. Pylori was identified by the appearance of milky colonies, gram negative bacillus in gram stained smear and positive urease test. Antimicrobial testing was performed on all isolates identified as H. pylori . All antibiotic disks were purchased from Sigma Company. Susceptibility testing was performed following the manufacturer's instructions. MICs were measured for each antibiotic and the resistance breakpoints were defined. The resistance breakpoint used for metronidazole was MIC > 8 μg/ml. Since the resistance breakpoints for other antibiotics are not established, the following values were accepted for other antibiotics: MIC > 0.12 μg/ml for furazolidone and MIC > 0.25 μg/ml for clarithromycin, amoxicillin, erythromycin and tetracycline.
The study was approved by ethics committee of the faculty and written informed consent was obtained from patients' parent's.
The SPSS 11.5 software package for windows was used for statistical analysis. Descriptive statistics were applied to the obtained data set. Results were considered significant at p ￡ 0.05. The role of gender, pathologic subtype of the disease and positive family history of peptic disease on metronidazole resistance rate were assessed using chi-square and Fisher exact test.
Results
Among all patients who underwent endoscopy, 62 patients with nodular gastritis or peptic ulcer were enrolled in our study. Therefore, 62 antral biopsy specimens were obtained for H. pylori culture and susceptibility testing. Urease test, histology and culture did not confirm the presence of H. pylori in 21 specimens. Furthermore, no H. pylori organisms were grown from 17 specimens despite positive histology and urease test. Finally, susceptibility test was performed on 24 culture positive specimens. Of 24 culture positive patients enrolled in our study, 14(58.33%) were male and 10(41.66%) were female. The age range of the patients was between 3.5 and 14 years with mean and median age of 9.5 and 10 years respectively. The most common endoscopic finding was nodular gastritis (in 19 patients); whereas, duodenal ulcer was observed in 4 patients and gastric ulcer was reported in only 1 patient. Among 24 H. pylori isolates, 10 (41.66%) were susceptible to all antimicrobial agents; yet, 14(58.33%) were resistant to = 1 antibiotic. Metronidazole resistant strains were isolated from 13 (54.16%) patients. The resistance rate for other anti microbial agents was reported as 8.33% (2 out of 24 patients) to amoxicillin, 4.16% (1patient) to erythromycin and 4.16% (1patient) to clarithromycin. None of the HP strains were resistant to tetracycline and furazolidone. Two (8.33%) of the isolates were resistant to both metronidazole and amoxicillin. Triple antibiotic resistance was observed in 1 (4.16%) isolate to metronidazole, clarithromycin and erythromycin.
Since most isolates were resistant to metronidazole, authors the association between metronidazole resistance rate and age, sex, pathologic subtype of the disease and family history of the peptic ulcer. The patients were divided into 2 age groups; 13 patients were 10 years old or older and 11 were below 10. Eight of the first group and 5 of the second were resistant to metronidazole. Statistical analysis revealed that metronidazole resistance rate was not significantly associated with age. Of 13 metronidazole resistant patients, 7(54%) were female and 6 (46%) were male. In metronidazole susceptible group, 3 and 8 patients were female and male respectively. No significant difference was found between these two groups regarding gender. Of 13 metronidazole resistant participants, 6 had positive family history for peptic disease. In the susceptible group, 2 patients out of 11 reported positive history of peptic ulcer in their families. Statistical analysis showed no significant difference between these two groups.
Pathologic subtypes of the disease are shown in [Table - 1]. Distribution of the pathologic subtypes of the disease doesn't significantly differ in metronidazole resistant and susceptible group.
Discussion
H. Pylori is considered the major cause of chronic gastritis and peptic ulcer disease in both adults and children. Additionally, it can increase the risk of malignancies in adulthood. In general, H. Pylori eradication regimen usually entails a proton pump inhibitor or bismuth in combination with two of the following antimicrobial agents: metronidazole, amoxicillin, tetracycline or clarithromycin. However, various clinical trials and in vitro studies have reported H. Pylori antimicrobial resistance all over the world that represents a serious public health challenge. H. Pylori antimicrobial resistance varies between different geographical regions. Therefore, healthcare awareness of the H. Pylori susceptibility to each of the commonly used antibiotics is necessary to be able to recommend the most effective therapy regimen. Patient noncompliance and the location of the bacterium which is beneath the gastric epithelium and out of reach of antibiotics are among the most common causes of treatment failure.[4],[10] However, the severity of gastric inflammation, dosage of proton pump inhibitor and the nature of pathology (ulcerative versus non ulcerative disease) also affect the outcome of therapy according to some literature.[12]
Overall, H. Pylori resistance to metronidazole is greater than all other antimicrobial agents and varies from < 10% to > 80% in different geographical regions.[13] We observed that 54.16% of H. Pylori isolates obtained from 29 pediatric patients were resistant to metronidazole which is a high proportion. Metronidazole resistance is strongly believed to be caused by H. Pylori genetic drift and adaptation to environment.[10],[14] Increased prescription of metronidazole for parasitic infection among children and infection with a resistant strain H. Pylori are the other factors leading to high metronidazole resistance rate.[9]
According to 2 previous studies there was no significant difference found in rate of metronidazole resistant H. Pylori strains regarding age in patients in both pediatric and adult group.[6],[9] Those findings are in agreement with their own results. They have also evaluated the role of gender. Both mentioned studies have reported the significantly higher metronidazole resistance rate in female group compared with males. On the contrary, there was observed no statistical difference in metronidazole resistance rate between girls and boys in the present study. They also found that positive family history for peptic disease is not significantly associated with higher metronidazole resistance rate.
H. Pylori resistance rate to clarithromycin has been described as 2-50% in various studies.[15] Macrolids are commonly prescribed in pediatric age group for otitis media and upper airway infections. Since a cross over resistance mechanism among different types of macrolids develops rapidly, the H. Pylori resistance rate is correlated to national level of macrolid consumption.[16] Moreover, according to some literature, resistance to clarithromycin is more frequently seen in children compared with adults.[4],[6] It can also be the consequence of more consumption of macrolids in pediatrics. The study, resistance to clarithromycin was observed in only one child out of 24 (4.16%) which is a low proportion of the patients.
Previous studies have indicated that H. Pylori antibiotic resistance may change with time even in the same population,[8], [17] that is caused by emergence of resistance to metronidazole or clarithromycin after treating H. Pylori or other infective diseases. Therefore, a continuous surveillance is needed to determine the most effective anti H. Pylori regimen. In order to decrease morbidity and health care costs, in resistant cases after the first therapy, culture and antimicrobial susceptibility test is recommended to find the most appropriate antimicrobial regimen for that special case. They observed that none of their patients were resistant to furazolidone and tetracycline. Metronidazole resistance is claimed to be a major reason for the failure of metronidazole-containing regimens in adults.[18] To enhance the eradication of H. Pylori , furazolidon would be a proper substitute for metronidazole in anti H. Pylori regimen profile for our resistant cases and all other societies with high grade of metronidazole resistance rate. The limitation of this study was the small sample size that is due to the nature of H. Pylori which is difficult to grow.
Conclusion
We showed a high grade of metronidazole resistance rate among our pediatric patients. Continuous prospective surveillance of H. pylori is essential. Moreover, culture and antimicrobial susceptibility test is recommended for resistant cases after the first failure to therapy.
References
1.Frenck RW Jr, Clemens J. Helicobacter in the developing world. Microbes Infect 2003; 5: 705-713. [PUBMED] [FULLTEXT]
2.Gottrand F, Turck D. Helicobacter pylori infection in children. Arch Pediatr 1995; 2 : 573-579. [PUBMED] [FULLTEXT]
3.Brown LM. Helicobacter pylori : epidemiology and routs of transmission. Epidemiol Rev 2000; 22 : 283-297. [PUBMED] [FULLTEXT]
4.Duck WM, Sobel J, Pruckler JM, Song Q, Swerdlow D, Friedman C et al. Antimicrobial resistance incidence and risk factors among Helicobacter pylori-infected persons, United States. Emerg Infect Dis 2004; 10 : 1088-1094.
5.Labenz J. Consequences of Helicobacter pylori cure in ulcer patients. Baillieres Best Pract Res Clin Gastroenterol 2000; 14 : 133-145. [PUBMED]
6.Kalach N, Bergeret M, Benhamou PH, Dupont C, Raymond J. High levels of resistance to metronidazole and clarithromycin in Helicobacter pylori strains in children. J Clin Microbiol 2001; 39: 394-397. [PUBMED] [FULLTEXT]
7.Hoffman JSC, David R. Treatment of Helicobacter pylori . Curr Opin Gastroenterol 2001; 17 : 30-34.
8.Adamek R J, Suerbaum S, Pfaffenbach B, Opferkuch W. Primary and acquired Helicobacter pylori resistance to clarithromycin, metronidazole, and amoxicillin-influence on treatment outcome. Am J Gastroenterol 1998; 93 : 386-389.
9.Kim JJ, Reddy R, Lee M, Kim JG, El-Zaatari FA, Osato MS et al. Analysis of metronidazole, clarithromycin and tetracycline resistance of Helicobacter pylori isolates from Korea. J Antimicrob Chemother 2001; 47 : 459-461.
10.Tolia V, Brown W, El-Baba M, Lin CH. Helicobacter pylori culture and antimicrobial susceptibility from pediatric patients in Michigan. Pediatr Infect Dis J 2000; 19 : 1167-1171. [PUBMED] [FULLTEXT]
11.Wolle K, Leodolter A, Malfertheiner P, Konig W. Antibiotic susceptibility of Helicobacter pylori in Germany: stable primary resistance from 1995 to 2000. J Med Microbiol 2002; 51: 705-709. [PUBMED] [FULLTEXT]
12.Shashidhar H, Peters JM, Lin CH, Rabah R, Thomas R, Tolia V. A prospective trial of lansoprazole triple therapy for pediatric Helicobacter pylori infection. J Pediatr Gastroenterol Nutr 2000; 30 : 276-282.
13.van der Wouden EJ, van Zwet AA, Vosmaer GD, Oom JA, de Jong A, Kleibeuker JH. Rapid increase in the prevalence of metronidazole-resistant Helicobacter pylori in the Netherlands. Emerg Infect Dis 1997; 3 : 385-389. [PUBMED]
14.Sisson G, Jeong JY, Goodwin A, Bryden L, Rossler N, Lim-Morrison S et al. Metronidazole activation is mutagenic and causes DNA fragmentation in Helicobacter pylori and in Escherichia coli containing a cloned H. pylori RdxA(+) (Nitroreductase) gene. J Bacteriol 2000; 182 : 5091-5096.
15.Malaty HM, Kim JG, Kim SD, Graham DY. Prevalence of Helicobacter pylori infection in Korean children: inverse relation to socioeconomic status despite a uniformly high prevalence in adults. Am J Epidemiol 1996; 143 : 257-262.
16.Cayla R. How to eradicate Helicobacter pylori Gastroenterol Clin Biol 1996; 20(1 Pt 2) : S119-S130.
17.Lin TKW, Cheng AFB, Sung JJY, Yiu PYL, Chung SSC. An increase in Helicobacter pylori strains resistant to metronidazole: a five-year study. Helicobacter 1996; 2 : 185-187.
18.Fakheri H, Malekzadeh R, Merat S, Khatibian M, Fazel A, Alizadeh BZ et al. Clarithromycin vs. Furazolidone in quadruple therapy regimens for the treatment of Helicobacter pylori in a population with a high metronidazole resistance rate. Aliment Pharmacol Ther 2001; 15 : 411-416.(Fallahi Gholam-Hossein, Maleknejad Shohr)
2 Gilan University of Medical Science, Iran
Objective. Helicobacter pylori is considered as an important etiologic factor in pathogenesis of peptic ulcer disease, chronic gastritis and gastric cancer. To eradicate this micro-organism, numerous regimens containing various antimicrobial agents have been suggested. However, H pylori antimicrobial resistance is a leading factor to treatment failure and recurrence of the disease. The aim of the study was to evaluate the prevalence of H pylori resistance to metronidazole, clarithromycin, tetracycline, amoxicillin, erythromycin and furazolidone in authors pediatric patients. Methods. Antral biopsy of all pediatric patients with negative history of receiving anti-H pylori regimen and endoscopic findings of nodular gastritis or peptic ulcer without previous history of NSAID consumption, burning and trauma were performed for H pylori histology, urease test and culture. All positive cultures were tested for antimicrobial susceptibility. Results. Twenty four patients (14 male and 10 female) between 3.5 and 14 years of age were culture positive. 54.16% of the isolates were resistant to metronidazole, 8.33% to amoxicillin, 4.16% to erythromycin and 4.16% to clarithromycin. None of authors patients were resistant to tetracycline and furazolidone. Conclusion . H. pylori antimicrobial resistance could be a major contributor to failure of H pylori eradication. Continuous prospective surveillance of H. Pylori is essential. Moreover, culture and antimicrobial susceptibility test is recommended for resistant cases after the first failure to therapy.
Keywords: H. Pylori, Drug resistance; Pediatric; Endoscopy
Helicobacter Pylori is a gram negative, spiral, flagellate bacillus that naturally colonizes human, living in gastric mucus. The 20% prevalence of infection with H. Pylori among adolescents in United States pales in comparison to infection rates exceeding 90% by 5 years of age in parts of the developing countries.[1] H. Pylori is the etiology of peptic ulcer disease, gastritis, gastric mucosa-associated lymphoid-tissue lymphoma and gastric adenocarcinoma.[2],[3] Eradication of infection heals the active ulcers in long term, and leads to reduction in ulcer recurrence and attendant complications.[4],[5],[6]
Numerous regimens of several antimicrobial agents are suggested to eradicate the bacterium. Among them, triple therapy containing a proton pump inhibitor or bismuth and two antibiotics, which are usually among metronidazole, amoxicillin, tetracycline or clarithromycin, for 2 weeks are applied widely.[7] However, it is difficult to eradicate H. Pylori due to emergence of antimicrobial resistant strains. Antibiotic resistance varies widely between geographical regions and among subgroups within a study population.[8] In a study performed in Korea, resistance rate to metronidazole and clarithrimycin was reported as 40.6% and 5.9% respectively.[9] Another study found that 45% of the isolates were resistant to metronidazole and 41% to clarithromycin in United States.[10] Kalach et al reported that 43% and 21% of his study participants were primarily resistant to metronidazole and clarithromycin respectively in France.[6] And a large prospective surveillance in Germany showed primary metronidazole and clarithromycin resistance rates of 26.2% and 2.2% respectively.[11]
It is essential to be aware of the local antibiotic resistance rate to be able to prescribe the proper regimen to eradicate H. Pylori . On the other hand, there is little literature on H. Pylori antimicrobial resistance in Middle East countries. Therefore, the authors undertook this study to prospectively evaluate H. Pylori susceptibility to the current antimicrobial agents used to eradicate this bacterium in our pediatric patients.
Materials and Methods
A prospective study was conducted. All patients ￡ 14 years old with upper gastrointestinal symptoms including recurrent abdominal pain, nausea, vomiting and the like referring to "Children Medical Centre" between Mar 2002 and Mar 2003 underwent esophagogastroduodenoscopy. The endoscopy was performed by a pediatric gastroenterologist. Those with negative history of receiving anti- H. Pylori regimen and endoscopic findings of nodular gastritis or peptic ulcer without previous history of NSAID consumption, burning and trauma were eligible to participate in their study. Single antral biopsy specimen was obtained from each participant. Biopsy specimens were kept in normal saline at 4oC and transported to the Health Faculty of Tehran University of Medical Science within 24 hours for culture. The specimens were inoculated onto Mueller-Hinton blood agar plates which were supplemented with 10 mg/L vancomycin, 50 μg/L polymyxin B and 5 mg/L trimethoprim to provide a selective media for H. pylori . The plates were incubated at an atmosphere of 5% CO2 at 37oC and relative humidity of 90% for 3 to 7 days. H. Pylori was identified by the appearance of milky colonies, gram negative bacillus in gram stained smear and positive urease test. Antimicrobial testing was performed on all isolates identified as H. pylori . All antibiotic disks were purchased from Sigma Company. Susceptibility testing was performed following the manufacturer's instructions. MICs were measured for each antibiotic and the resistance breakpoints were defined. The resistance breakpoint used for metronidazole was MIC > 8 μg/ml. Since the resistance breakpoints for other antibiotics are not established, the following values were accepted for other antibiotics: MIC > 0.12 μg/ml for furazolidone and MIC > 0.25 μg/ml for clarithromycin, amoxicillin, erythromycin and tetracycline.
The study was approved by ethics committee of the faculty and written informed consent was obtained from patients' parent's.
The SPSS 11.5 software package for windows was used for statistical analysis. Descriptive statistics were applied to the obtained data set. Results were considered significant at p ￡ 0.05. The role of gender, pathologic subtype of the disease and positive family history of peptic disease on metronidazole resistance rate were assessed using chi-square and Fisher exact test.
Results
Among all patients who underwent endoscopy, 62 patients with nodular gastritis or peptic ulcer were enrolled in our study. Therefore, 62 antral biopsy specimens were obtained for H. pylori culture and susceptibility testing. Urease test, histology and culture did not confirm the presence of H. pylori in 21 specimens. Furthermore, no H. pylori organisms were grown from 17 specimens despite positive histology and urease test. Finally, susceptibility test was performed on 24 culture positive specimens. Of 24 culture positive patients enrolled in our study, 14(58.33%) were male and 10(41.66%) were female. The age range of the patients was between 3.5 and 14 years with mean and median age of 9.5 and 10 years respectively. The most common endoscopic finding was nodular gastritis (in 19 patients); whereas, duodenal ulcer was observed in 4 patients and gastric ulcer was reported in only 1 patient. Among 24 H. pylori isolates, 10 (41.66%) were susceptible to all antimicrobial agents; yet, 14(58.33%) were resistant to = 1 antibiotic. Metronidazole resistant strains were isolated from 13 (54.16%) patients. The resistance rate for other anti microbial agents was reported as 8.33% (2 out of 24 patients) to amoxicillin, 4.16% (1patient) to erythromycin and 4.16% (1patient) to clarithromycin. None of the HP strains were resistant to tetracycline and furazolidone. Two (8.33%) of the isolates were resistant to both metronidazole and amoxicillin. Triple antibiotic resistance was observed in 1 (4.16%) isolate to metronidazole, clarithromycin and erythromycin.
Since most isolates were resistant to metronidazole, authors the association between metronidazole resistance rate and age, sex, pathologic subtype of the disease and family history of the peptic ulcer. The patients were divided into 2 age groups; 13 patients were 10 years old or older and 11 were below 10. Eight of the first group and 5 of the second were resistant to metronidazole. Statistical analysis revealed that metronidazole resistance rate was not significantly associated with age. Of 13 metronidazole resistant patients, 7(54%) were female and 6 (46%) were male. In metronidazole susceptible group, 3 and 8 patients were female and male respectively. No significant difference was found between these two groups regarding gender. Of 13 metronidazole resistant participants, 6 had positive family history for peptic disease. In the susceptible group, 2 patients out of 11 reported positive history of peptic ulcer in their families. Statistical analysis showed no significant difference between these two groups.
Pathologic subtypes of the disease are shown in [Table - 1]. Distribution of the pathologic subtypes of the disease doesn't significantly differ in metronidazole resistant and susceptible group.
Discussion
H. Pylori is considered the major cause of chronic gastritis and peptic ulcer disease in both adults and children. Additionally, it can increase the risk of malignancies in adulthood. In general, H. Pylori eradication regimen usually entails a proton pump inhibitor or bismuth in combination with two of the following antimicrobial agents: metronidazole, amoxicillin, tetracycline or clarithromycin. However, various clinical trials and in vitro studies have reported H. Pylori antimicrobial resistance all over the world that represents a serious public health challenge. H. Pylori antimicrobial resistance varies between different geographical regions. Therefore, healthcare awareness of the H. Pylori susceptibility to each of the commonly used antibiotics is necessary to be able to recommend the most effective therapy regimen. Patient noncompliance and the location of the bacterium which is beneath the gastric epithelium and out of reach of antibiotics are among the most common causes of treatment failure.[4],[10] However, the severity of gastric inflammation, dosage of proton pump inhibitor and the nature of pathology (ulcerative versus non ulcerative disease) also affect the outcome of therapy according to some literature.[12]
Overall, H. Pylori resistance to metronidazole is greater than all other antimicrobial agents and varies from < 10% to > 80% in different geographical regions.[13] We observed that 54.16% of H. Pylori isolates obtained from 29 pediatric patients were resistant to metronidazole which is a high proportion. Metronidazole resistance is strongly believed to be caused by H. Pylori genetic drift and adaptation to environment.[10],[14] Increased prescription of metronidazole for parasitic infection among children and infection with a resistant strain H. Pylori are the other factors leading to high metronidazole resistance rate.[9]
According to 2 previous studies there was no significant difference found in rate of metronidazole resistant H. Pylori strains regarding age in patients in both pediatric and adult group.[6],[9] Those findings are in agreement with their own results. They have also evaluated the role of gender. Both mentioned studies have reported the significantly higher metronidazole resistance rate in female group compared with males. On the contrary, there was observed no statistical difference in metronidazole resistance rate between girls and boys in the present study. They also found that positive family history for peptic disease is not significantly associated with higher metronidazole resistance rate.
H. Pylori resistance rate to clarithromycin has been described as 2-50% in various studies.[15] Macrolids are commonly prescribed in pediatric age group for otitis media and upper airway infections. Since a cross over resistance mechanism among different types of macrolids develops rapidly, the H. Pylori resistance rate is correlated to national level of macrolid consumption.[16] Moreover, according to some literature, resistance to clarithromycin is more frequently seen in children compared with adults.[4],[6] It can also be the consequence of more consumption of macrolids in pediatrics. The study, resistance to clarithromycin was observed in only one child out of 24 (4.16%) which is a low proportion of the patients.
Previous studies have indicated that H. Pylori antibiotic resistance may change with time even in the same population,[8], [17] that is caused by emergence of resistance to metronidazole or clarithromycin after treating H. Pylori or other infective diseases. Therefore, a continuous surveillance is needed to determine the most effective anti H. Pylori regimen. In order to decrease morbidity and health care costs, in resistant cases after the first therapy, culture and antimicrobial susceptibility test is recommended to find the most appropriate antimicrobial regimen for that special case. They observed that none of their patients were resistant to furazolidone and tetracycline. Metronidazole resistance is claimed to be a major reason for the failure of metronidazole-containing regimens in adults.[18] To enhance the eradication of H. Pylori , furazolidon would be a proper substitute for metronidazole in anti H. Pylori regimen profile for our resistant cases and all other societies with high grade of metronidazole resistance rate. The limitation of this study was the small sample size that is due to the nature of H. Pylori which is difficult to grow.
Conclusion
We showed a high grade of metronidazole resistance rate among our pediatric patients. Continuous prospective surveillance of H. pylori is essential. Moreover, culture and antimicrobial susceptibility test is recommended for resistant cases after the first failure to therapy.
References
1.Frenck RW Jr, Clemens J. Helicobacter in the developing world. Microbes Infect 2003; 5: 705-713. [PUBMED] [FULLTEXT]
2.Gottrand F, Turck D. Helicobacter pylori infection in children. Arch Pediatr 1995; 2 : 573-579. [PUBMED] [FULLTEXT]
3.Brown LM. Helicobacter pylori : epidemiology and routs of transmission. Epidemiol Rev 2000; 22 : 283-297. [PUBMED] [FULLTEXT]
4.Duck WM, Sobel J, Pruckler JM, Song Q, Swerdlow D, Friedman C et al. Antimicrobial resistance incidence and risk factors among Helicobacter pylori-infected persons, United States. Emerg Infect Dis 2004; 10 : 1088-1094.
5.Labenz J. Consequences of Helicobacter pylori cure in ulcer patients. Baillieres Best Pract Res Clin Gastroenterol 2000; 14 : 133-145. [PUBMED]
6.Kalach N, Bergeret M, Benhamou PH, Dupont C, Raymond J. High levels of resistance to metronidazole and clarithromycin in Helicobacter pylori strains in children. J Clin Microbiol 2001; 39: 394-397. [PUBMED] [FULLTEXT]
7.Hoffman JSC, David R. Treatment of Helicobacter pylori . Curr Opin Gastroenterol 2001; 17 : 30-34.
8.Adamek R J, Suerbaum S, Pfaffenbach B, Opferkuch W. Primary and acquired Helicobacter pylori resistance to clarithromycin, metronidazole, and amoxicillin-influence on treatment outcome. Am J Gastroenterol 1998; 93 : 386-389.
9.Kim JJ, Reddy R, Lee M, Kim JG, El-Zaatari FA, Osato MS et al. Analysis of metronidazole, clarithromycin and tetracycline resistance of Helicobacter pylori isolates from Korea. J Antimicrob Chemother 2001; 47 : 459-461.
10.Tolia V, Brown W, El-Baba M, Lin CH. Helicobacter pylori culture and antimicrobial susceptibility from pediatric patients in Michigan. Pediatr Infect Dis J 2000; 19 : 1167-1171. [PUBMED] [FULLTEXT]
11.Wolle K, Leodolter A, Malfertheiner P, Konig W. Antibiotic susceptibility of Helicobacter pylori in Germany: stable primary resistance from 1995 to 2000. J Med Microbiol 2002; 51: 705-709. [PUBMED] [FULLTEXT]
12.Shashidhar H, Peters JM, Lin CH, Rabah R, Thomas R, Tolia V. A prospective trial of lansoprazole triple therapy for pediatric Helicobacter pylori infection. J Pediatr Gastroenterol Nutr 2000; 30 : 276-282.
13.van der Wouden EJ, van Zwet AA, Vosmaer GD, Oom JA, de Jong A, Kleibeuker JH. Rapid increase in the prevalence of metronidazole-resistant Helicobacter pylori in the Netherlands. Emerg Infect Dis 1997; 3 : 385-389. [PUBMED]
14.Sisson G, Jeong JY, Goodwin A, Bryden L, Rossler N, Lim-Morrison S et al. Metronidazole activation is mutagenic and causes DNA fragmentation in Helicobacter pylori and in Escherichia coli containing a cloned H. pylori RdxA(+) (Nitroreductase) gene. J Bacteriol 2000; 182 : 5091-5096.
15.Malaty HM, Kim JG, Kim SD, Graham DY. Prevalence of Helicobacter pylori infection in Korean children: inverse relation to socioeconomic status despite a uniformly high prevalence in adults. Am J Epidemiol 1996; 143 : 257-262.
16.Cayla R. How to eradicate Helicobacter pylori Gastroenterol Clin Biol 1996; 20(1 Pt 2) : S119-S130.
17.Lin TKW, Cheng AFB, Sung JJY, Yiu PYL, Chung SSC. An increase in Helicobacter pylori strains resistant to metronidazole: a five-year study. Helicobacter 1996; 2 : 185-187.
18.Fakheri H, Malekzadeh R, Merat S, Khatibian M, Fazel A, Alizadeh BZ et al. Clarithromycin vs. Furazolidone in quadruple therapy regimens for the treatment of Helicobacter pylori in a population with a high metronidazole resistance rate. Aliment Pharmacol Ther 2001; 15 : 411-416.(Fallahi Gholam-Hossein, Maleknejad Shohr)