Amoxicillin resistance with beta-lactamase production in Helicobacter pylori.

Abstract

BACKGROUND:

Amoxicillin-resistant Helicobacter pylori with minimal inhibitory concentration (MIC) >or= 256 mg L(-1) was isolated from a gastritis patient. The aims were to investigate the mechanism of high-level amoxicillin resistance in H. pylori.

MATERIALS AND METHODS:

The beta-lactamase production was determined by means of nitrocefin sticks and the presence of gene encoding the beta-lactam antibiotic resistance enzyme TEM beta-lactamase was analysed by polymerase chain reaction (PCR), sequencing and dot-blot hybridization. Sequencing analysis of pbp1A gene was performed and amoxicillin-susceptible isolate was transformed with pbp1A PCR products from the resistant isolate. The expression of hefC efflux system was analysed using real-time quantitative PCR.

RESULTS:

Activity of beta-lactamase was detected. Sequence analysis showed that the PCR product derived from H. pylori 3778 was identical to the bla(TEM-1) (GenBank accession EU726527). Dot-blot hybridization confirmed the presence of beta-lactamase gene bla(TEM-1.) By transformation of PCR product of mutated pbp1A gene from H. pylori 3778 into amoxicillin-susceptible strain showed that substitutions in Thr(556)-->Ser, Lys(648)-->Gln, Arg(649)-->Lys and Arg(656)-->Pro contribute to low-level amoxicillin resistance. The MIC of amoxicillin for the transformants was 0.75 mg L(-1). Over-expression of hefC was not found.

CONCLUSIONS:

High-level amoxicillin resistance is associated with beta-lactamase production in H. pylori. Low-level amoxicillin resistance is linked to a point mutation on pbp1A. Because H. pylori can exchange DNA through natural transformation, spreading of bla(TEM-1) amoxicillin resistance gene among H. pylori is a potential threat when treating H. pylori infection.

• Authors: Y-S Tseng, D-C Wu, C-Y Chang, C-H Kuo, Y-C Yang, C-M Jan, Y-C Su, F-C Kuo, L-L Chang
• Journal: European journal of clinical investigation (Eur J Clin Invest) Vol. 39 Issue 9 Pg. 807-12 (Sep 2009) ISSN: 1365-2362 [Electronic] England
• PMID: 19614952 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Amoxicillin
• beta-Lactamases

Topics

• Amoxicillin (pharmacology)
• Drug Resistance, Microbial (drug effects, genetics)
• Gene Expression Regulation, Bacterial (drug effects, genetics)
• Helicobacter Infections (drug therapy, genetics)
• Helicobacter pylori (isolation & purification, metabolism)
• Humans
• Microbial Sensitivity Tests
• Reverse Transcriptase Polymerase Chain Reaction
• Sequence Analysis, DNA
• beta-Lactamases (drug effects, metabolism)