In Vitro Activity of Clarithromycin against Intracellular Helicobacter pylori

Abstract

The in vitro intracellular effect of clarithromycin, amoxicillin, metronidazole, lansoprazole, and rifabutin, tested at concentrations corresponding to one times the MIC, two times the MIC, and four times the MIC, was evaluated against an invasive Helicobacter pylori strain. At four times the MIC, clarithromycin showed an early bactericidal effect within 4 h of incubation and, in determining the complete killing within a 16 h-incubation period, lansoprazole and rifabutin showed comparable activity, yielding bactericidal activities within 4 and 8 h of incubation, respectively. Amoxicillin and metronidazole showed bacteriostatic activity only.Helicobacter pylori is a gram-negative, microaerophilic spiral bacterium that has been undisputably implicated in the etiology of chronic active gastritis, peptic ulceration disease, and gastric carcinoma in humans worldwide. H. pylori in vivo is commonly found adhering to gastric epithelial cells, and it is not considered as an invasive pathogen. However, observations both in vitro and in vivo have shown that H. pylori is capable of invading epithelial cells (4, 18). Some electron microscopic studies have also shown that H. pylori is often observed at the intercellular junctions between gastric epithelial cells or within intercellular spaces and gastric mucosal cells (11,12,18).Recently, we have shown that H. pylori can survive intracellularly for at least 48 h in vitro and that the intracellular bacteria can be killed by clarithromycin (15); these data suggest that treatment failures may be due, at least in part, to the existence of an ecological niche for the organism that allows it to survive both the hostile gastric environment and antibacterial therapy. Rifabutin, a spiropiperidyl-rifamycin derived from rifamycin S, has a broad spectrum of antimicrobial activity, including activity against mycobacteria (8). Its stability over a wide pH range suggests that it is a sensible alternative to study for activity against H. pylori. The in vitro activities of amoxicillin, clarithromycin, metronidazole, lansoprazole, and rifabutin were examined against one intracellular H. pylori clinical strain.The clinical strain H. pylori UdA203 was grown onto modified chocolate agar (14) under microaerophilic conditions (5% O 2 , 10% CO 2 , 85% N 2 ; CampyGen; Oxoid/Garbagnate Milanese, Milan, Italy) for 72 h at 37°C. Amoxicillin and metronidazole were purchased from Sigma-Aldrich (Milan, Italy); clarithromycin, rifabutin, and lansoprazole were kindly supplied by Abbott Italy S.p.A. (Campoverde, Latina, Italy), Pharmacia & Upjohn (Milan, Italy), and Takeda Chemical Industries (Osaka, Japan), respectively. Stock solutions were prepared according to the manufacturers' recommendations on the day of use. MICs were assessed in duplicate by the agar dilution method according to NCCLS guidelines (9). Twofold dilutions of each drug ranging from 0.008 to 64 g/ml were tested. The minimal bactericidal concentration (MBC) was established by spreading 0.01 ml from each concentration onto Columbia blood ag...

Rifabutin Containing Triple Therapy and Rifabutin with Bismuth Containing Quadruple Therapy for Third‐Line Treatment of Helicobacter pylori Infection: Two Pilot Studies

“…Rifabutin inhibits the beta-subunit of H. pylori DNAdependent RNA polymerase encoded by the rpoB gene [17] and shows good intracellular activity against H. pylori [18].…”

Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains ofHelicobacter pyloriand prevents benzo[a]pyrene-induced stomach tumors

“…Intracellular activity was studied in HEp-2 cells (ATCC CCL 23), a human epithelial cell line previously used to determine the activity of drugs against intracellular H. pylori (52,53). HEp-2 cells were routinely cultured in 75-cm 2 plastic tissue culture T-flasks containing minimum essential medium supplemented with Eagle's salts, 50 mM L-glutamine, and 0.75% sodium bicarbonate (EMEM), and 10% FCS at 37°C in 5% CO 2 .…”

Effective antimicrobial activity of rifabutin against multidrug‐resistant Helicobacter pylori

“…When internalized into the gastric epithelial cells, H. pylori can survive against hostile gastric environment as well as antibacterial therapy. 40,41 RFB is known as a cell membrane-penetrating antibiotic, 42…”

“…The remaining 67 isolates showed MDR pattern (2-to 5-labeled bar) bactericidal activity against intracellular bacteria was observed within 8 hours. 42 Recently, the WHO categorizes H. pylori among antibioticresistant bacteria which poses a great impact on human health. 43 Successful treatment of H. pylori-related diseases with currently used antibiotics is only effective in areas with low prevalence of antibiotic resistance and low encounter of human subjects with antibiotics in the same class.…”