Resistance of Helicobacter pylori to Tetracicline

CAMARGO G; STEGE PW; MAJUL R; GOMEZ P; VEGA AE

Merlo, San Luis

Congreso; Annual Scientific Meeting of biology; 2004

Sociedad de biología de cuyo

For treatment of H. pylori infections, tetracycline-based triple or quadruple therapies are often used as a second-line treatment. Un­til the turn of the century only a few reports were published on spontaneous tetracycline (TET) resistance. However, an increase in the incidence of TET resistance has been reported in the last 2 years. The aim of this study was to determine the prevalence of tetracy­cline resistant H. pylori isolated from symptomatic adult patients from San Luis. TET MIC for sixty-two clinical isolates was deter­mined by agar dilution method according to the NCCLS recom­mendations. H. pylori NCTC 11638 was used as control. Antibi­otic was included in Mueller-Hinton agar supplemented with 7% horse blood as two-fold dilutions from 128 to 0.008 mg/L. Resis­tance to TET was present when MIC= 1 mg/L. Four tetracycline­ resistant strains were determined in this study. Interestingly, all of the TET resistant isolates exhibited cross-resistance to metronida­zole. Several authors have suggested that there may be a progres­sive acquisition of resistance where metronidazole resistance may be required before TET resistance can develop, but not vice versa. In H. pylori, metronidazole is converted to an active, mutagenic compound that could increase mutations in the 16S rRNA genes responsible for TET resistance in H. pylori. Emergence of cross­resistant strains among clinical isolates represents a major threat to current H. pylori eradication therapies.