Susceptibilities of Helicobacter pylori strains isolated from children with gastritis to selected antibiotics

J Antimicrob Chemother 1999; 44: 720–722

Andreas F. Mentisa,*, Eleftheria Romab, Anastasia Pangalisc and Evangelia Katsiyiannakisd

aLaboratory of Bacteriology, Hellenic Pasteur Institute, Vas. Sofias Ave 127, 115 21 Athens bGastroenterology Unit of First Department of Paediatrics, Athens University, Athens cDepartment of Clinical Microbiology dPaediatric Gastroenterology Unit, ‘Agia Sofia’ Children's Hospital, Athens, Greece

Sir,

High percentages of children with gastritis or peptic ulcer disease are infected with Helicobacter pylori and, in common with adults, eradication of this pathogen results in long-term cure.1 However, the increasing frequencies with which metronidazole and clarithromycin, both constituents of commonly used treatment regimens, are administered, either for the eradication of H. pylori or as therapy of other infections, may lead to high rates of resistance to these antibiotics amongst H. pylori strains; primary or acquired resistance is predictive of treatment failure in adults2 and children1 with infections caused by this bacterium. Periodic monitoring of the antibiotic susceptibilities of isolates is therefore of considerable importance. The purpose of the present study was to assess the in-vitro activities of selected antibiotics against H. pylori strains isolated from children in Greece.

Thirty-six H. pylori isolates were studied. The strains were recovered from gastric antral biopsies obtained from children (20 males and 16 females) 6–15 years of age (mean age 10.5 ± 3.2 years) with symptoms of gastritis, i.e. recurrent abdominal pain for at least 3 months, with or without nausea, vomiting, upper gastrointestinal tract bleeding or weight loss. None of the children had received antibiotics for at least 2 months before undergoing endoscopy. The isolates were identified by routine laboratory methods and stored in Brain Heart Infusion broth (Oxoid Ltd, Basingstoke, UK) containing glycerol at –80°C until just before testing. The antibiotics evaluated were as follows: amoxycillin, clarithromycin and ciprofloxacin, which were provided by SmithKline Beecham Hellas S.A. (Athens, Greece), Abbott Laboratories Hellas S.A. (Athens) and Bayer Hellas S.A. (Athens), respectively; and tetracycline, minocycline, metronidazole and tinidazole, all of which were purchased from Sigma–Aldrich OM Ltd (Athens). MICs were determined by an agar dilution method as described previously, but with slight modifications;3 the medium used was Mueller–Hinton (Oxoid) supplemented with 7% horse blood. Inocula of 104–105 cfu were applied with a multipoint inoculator and H. pylori strain CGUT 17874 and three clinical isolates of H. pylori, the susceptibilities of which had been determined in previous studies, were included as controls. The MIC was taken as the lowest concentration of each antibiotic that inhibited visible growth after incubation at 37°C in a microaerophilic atmosphere for 72 h.

The susceptibility test results for the 36 isolates are shown in the Table. All of the strains were susceptible to amoxycillin, tetracycline, minocycline and ciprofloxacin. Ten (28%) of the isolates were resistant to metronidazole and tinidazole, cross-resistance being observed in all resistant isolates. Two (5.5%) isolates were resistant to clarithromycin (MICs > 8 mg/L).


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Table. In-vitro susceptibilities of 36 H. pylori strains isolated from children to selected antibiotics
 
At the time the study was undertaken, there was no standardized method of determining the antibiotic susceptibilities of H. pylori isolates. The agar dilution method used here is time-consuming, but the results are both reliable and reproducible and the correlation with clinical outcome is greater than those of other methods. It should therefore be regarded as the reference method when evaluating other susceptibility testing techniques.4

The incidence of resistance to metronidazole amongst H. pylori strains isolated from adults in Greece is 49%,5 while that to clarithromycin is 6% (unpublished data). We have detected a lower incidence of resistance to metronidazole, but a comparable incidence of resistance to clarithromycin, in strains recovered from children. The lower incidence of resistance to metronidazole amongst isolates from children probably reflects the less frequent use of this drug in childhood. In general, data relating to the incidences of antibiotic resistance amongst H. pylori isolates from children are limited; in France, rates of resistance to metronidazole and clarithromycin have been reported to be between 26 and 40% and between 4.3 and 7%, respectively6—figures that are comparable to those described here. Knowledge of antibiotic resistance rates is important to the successful treatment of patients with H. pylori infections, as eradication rates are reduced when children are infected with resistant strains.7 In order to facilitate optimal therapy, the susceptibilities of isolates from children (and adults) should therefore be monitored locally at periodic intervals.

Notes

* Corresponding author. Tel: +30-1-64-62-281; Fax: +30-1-64-23-498; E-mail:mentis1{at}otenet.gr Back

References

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2 . Goddard, A. F. & Logan, R. P. H. (1996). Antimicrobial resistance and Helicobacter pylori. Journal of Antimicrobial Chemotherapy 37, 639–43.[ISI][Medline]

3 . Tzelepi, E., Mentis, A. F., Spiliadis, C. & Tzouvelekis, L. S. (1991). Antibiotic susceptibility and plasmid content of Helicobacter pylori strains isolated in Greece. International Journal of Experimental and Clinical Chemotherapy 4, 111–3.

4 . Megraud, F. (1997). Resistance of Helicobacter pylori to antibiotics. Advanced Pharmacology and Therapeutics 11, Suppl. 1, 43–53.

5 . European Study Group on Antibiotic Susceptibility of Helicobacter pylori. (1992). Results of a multicentre European survey in 1991 of metronidazole resistance in Helicobacter pylori. European Journal of Clinical Microbiology and Infectious Diseases 11, 777–81.[ISI][Medline]

6 . Dhaenens, L., Szczebara, F. & Husson, M.-O. (1996). In-vitro activities of clarithromycin and other antimicrobial agents against Helicobacter pylori isolated from children. Journal of Antimicrobial Chemotherapy 38, 318–9.[ISI][Medline]

7 . Raymond, J., Kalach, N., Bergeret, M., Benhamou, P. H., Barbet, J. P., Gendrel, D. et al. (1998). Effect of metronidazole resistance on eradication of Helicobacter pylori in infected children. Antimicrobial Agents and Chemotherapy 42,1334 –5.[Abstract/Free Full Text]