M P Dore1, D Y Graham, A R Sepulveda. 1. Department of Medicine and Pathology, VA Medical Center and Baylor College of Medicine, Houston, TX 77030, USA.
Abstract
BACKGROUND: The beta-lactam group of antibiotics kills bacteria by inhibiting the terminal stages of peptidoglycan metabolism. We have recently identified amoxicillin-resistant Helicobacter pylori, none of which expressed beta-lactamase. Penicillin-binding proteins (PBPs) represent a group of target enzymes for the beta-lactam antibiotic family, and alterations in PBPs have been described in other penicillin-resistant bacteria. The amoxicillin-resistant phenotype characteristically was lost after freezing but could be restored by consecutive transfers into gradient plates. MATERIALS AND METHODS: To determine whether amoxicillin resistance in H. pylori was related to alterations in any of the H. pylori PBPs, five H. pylori strains resistant to amoxicillin and three amoxicillin-sensitive strains were tested. PBPs were extracted from bacteria grown to logarithmic phase, labeled in vivo with 3H-benzylpenicillin, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Four main PBPs were separated from all amoxicillin-sensitive H. pylori strains. RESULTS: Only three of the four main PBPs were found in the amoxicillin-resistant H. pylori strains. The differentially detectable PBP (PBP D) had an apparent molecular weight of 30 to 32 kD. CONCLUSION: These results suggest that PBP D might play a role in the amoxicillin-resistant phenotype of H. pylori strains lacking beta-lactamase activity.
BACKGROUND: The beta-lactam group of antibiotics kills bacteria by inhibiting the terminal stages of peptidoglycan metabolism. We have recently identified amoxicillin-resistant Helicobacter pylori, none of which expressed beta-lactamase. Penicillin-binding proteins (PBPs) represent a group of target enzymes for the beta-lactam antibiotic family, and alterations in PBPs have been described in other penicillin-resistant bacteria. The amoxicillin-resistant phenotype characteristically was lost after freezing but could be restored by consecutive transfers into gradient plates. MATERIALS AND METHODS: To determine whether amoxicillin resistance in H. pylori was related to alterations in any of the H. pylori PBPs, five H. pylori strains resistant to amoxicillin and three amoxicillin-sensitive strains were tested. PBPs were extracted from bacteria grown to logarithmic phase, labeled in vivo with 3H-benzylpenicillin, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Four main PBPs were separated from all amoxicillin-sensitive H. pylori strains. RESULTS: Only three of the four main PBPs were found in the amoxicillin-resistant H. pylori strains. The differentially detectable PBP (PBP D) had an apparent molecular weight of 30 to 32 kD. CONCLUSION: These results suggest that PBP D might play a role in the amoxicillin-resistant phenotype of H. pylori strains lacking beta-lactamase activity.
Authors: Ousman Secka; Douglas E Berg; Martin Antonio; Tumani Corrah; Mary Tapgun; Robert Walton; Vivat Thomas; Juan J Galano; Javier Sancho; Richard A Adegbola; Julian E Thomas Journal: Antimicrob Agents Chemother Date: 2012-12-21 Impact factor: 5.191