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In vitro activity of rifaximin, metronidazole and vancomycin against Clostridium difficile and the rate of selection of spontaneously resistant mutants against representative anaerobic and aerobic bacteria, including ammonia-producing species.
Chemotherapy. 2000 Jul-Aug; 46(4):253-66.C

Abstract

BACKGROUND

Rifaximin is a rifamycin derivative characterized by a wide antibacterial activity. This drug is neither absorbed by the gastrointestinal tract nor inactivated by gastric juices, and exerts its action entirely within the intestinal lumen.

METHODS

In this study, the activity of this antibiotic was compared with that of metronidazole and vancomycin against 93 Clostridium difficile isolates. The rate of emergence of bacteria spontaneously resistant to the new compound was also evaluated in relation to representative gram-positive and gram-negative strains. In terms of MIC(50) values, rifaximin showed an intrinsic activity superior to that of the other agents. The emergence of spontaneously resistant strains was assessed with 46 aerobic (staphylococci, enterococci, Proteus spp., Citrobacter freundii, Providencia rettgeri, enteropathogenic, enteroinvasive, enterotoxigenic and entero- hemorrhagic Escherichia coli, and Salmonella enteritidis) and anaerobic (Clostridium spp., Bacteroides spp., Fusobacterium nucleatum and Peptococcus spp.) pathogens, most of them also ammonium producers. Two different methods, broth and agar dilution, were employed.

RESULTS

When liquid medium was employed, bacteria capable of sustained growth in 100 microg/ml of rifaximin were obtained after 2-5 transfers with gram-positive aerobic cocci, 2-3 transfers with gram-negative aerobic strains and 2-5 transfers with anaerobic species. At the highest dose used with the agar dilution method (8 x MIC), the frequency of emergence of spontaneously resistant mutants ranged from <1 x 10(-9) to 1.6 x 10(-8) with gram-positive aerobic and anaerobic cocci, while with aerobic and anaerobic gram-negative bacteria, this value ranged from <1 x 10(-9) to 1.7 x 10(-7). C. difficile showed a particularly low incidence of spontaneously resistant mutants (<1 x 10(-9)). The low incidence of resistant subpopulations selected by levels of 8 x MIC of rifaximin suggests that the high levels of the drug which were reached in the gastrointestinal lumen may further prevent the selection of mutants.

CONCLUSION

The low toxicity, broad antibacterial activity and very poor absorption from the gastrointestinal tract of rifaximin suggest a potential therapeutic use for this drug in gastrointestinal diseases, as well as in the management of patients with cirrhosis and chronic portal-systemic encephalopathy.

Authors+Show Affiliations

Istituto di Microbiologia C.A. Romanzi, Università di Genova, Italy.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

10859431

Citation

Marchese, A, et al. "In Vitro Activity of Rifaximin, Metronidazole and Vancomycin Against Clostridium Difficile and the Rate of Selection of Spontaneously Resistant Mutants Against Representative Anaerobic and Aerobic Bacteria, Including Ammonia-producing Species." Chemotherapy, vol. 46, no. 4, 2000, pp. 253-66.
Marchese A, Salerno A, Pesce A, et al. In vitro activity of rifaximin, metronidazole and vancomycin against Clostridium difficile and the rate of selection of spontaneously resistant mutants against representative anaerobic and aerobic bacteria, including ammonia-producing species. Chemotherapy. 2000;46(4):253-66.
Marchese, A., Salerno, A., Pesce, A., Debbia, E. A., & Schito, G. C. (2000). In vitro activity of rifaximin, metronidazole and vancomycin against Clostridium difficile and the rate of selection of spontaneously resistant mutants against representative anaerobic and aerobic bacteria, including ammonia-producing species. Chemotherapy, 46(4), 253-66.
Marchese A, et al. In Vitro Activity of Rifaximin, Metronidazole and Vancomycin Against Clostridium Difficile and the Rate of Selection of Spontaneously Resistant Mutants Against Representative Anaerobic and Aerobic Bacteria, Including Ammonia-producing Species. Chemotherapy. 2000 Jul-Aug;46(4):253-66. PubMed PMID: 10859431.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - In vitro activity of rifaximin, metronidazole and vancomycin against Clostridium difficile and the rate of selection of spontaneously resistant mutants against representative anaerobic and aerobic bacteria, including ammonia-producing species. AU - Marchese,A, AU - Salerno,A, AU - Pesce,A, AU - Debbia,E A, AU - Schito,G C, PY - 2000/6/22/pubmed PY - 2000/8/19/medline PY - 2000/6/22/entrez SP - 253 EP - 66 JF - Chemotherapy JO - Chemotherapy VL - 46 IS - 4 N2 - BACKGROUND: Rifaximin is a rifamycin derivative characterized by a wide antibacterial activity. This drug is neither absorbed by the gastrointestinal tract nor inactivated by gastric juices, and exerts its action entirely within the intestinal lumen. METHODS: In this study, the activity of this antibiotic was compared with that of metronidazole and vancomycin against 93 Clostridium difficile isolates. The rate of emergence of bacteria spontaneously resistant to the new compound was also evaluated in relation to representative gram-positive and gram-negative strains. In terms of MIC(50) values, rifaximin showed an intrinsic activity superior to that of the other agents. The emergence of spontaneously resistant strains was assessed with 46 aerobic (staphylococci, enterococci, Proteus spp., Citrobacter freundii, Providencia rettgeri, enteropathogenic, enteroinvasive, enterotoxigenic and entero- hemorrhagic Escherichia coli, and Salmonella enteritidis) and anaerobic (Clostridium spp., Bacteroides spp., Fusobacterium nucleatum and Peptococcus spp.) pathogens, most of them also ammonium producers. Two different methods, broth and agar dilution, were employed. RESULTS: When liquid medium was employed, bacteria capable of sustained growth in 100 microg/ml of rifaximin were obtained after 2-5 transfers with gram-positive aerobic cocci, 2-3 transfers with gram-negative aerobic strains and 2-5 transfers with anaerobic species. At the highest dose used with the agar dilution method (8 x MIC), the frequency of emergence of spontaneously resistant mutants ranged from <1 x 10(-9) to 1.6 x 10(-8) with gram-positive aerobic and anaerobic cocci, while with aerobic and anaerobic gram-negative bacteria, this value ranged from <1 x 10(-9) to 1.7 x 10(-7). C. difficile showed a particularly low incidence of spontaneously resistant mutants (<1 x 10(-9)). The low incidence of resistant subpopulations selected by levels of 8 x MIC of rifaximin suggests that the high levels of the drug which were reached in the gastrointestinal lumen may further prevent the selection of mutants. CONCLUSION: The low toxicity, broad antibacterial activity and very poor absorption from the gastrointestinal tract of rifaximin suggest a potential therapeutic use for this drug in gastrointestinal diseases, as well as in the management of patients with cirrhosis and chronic portal-systemic encephalopathy. SN - 0009-3157 UR - https://www.unboundmedicine.com/medline/citation/10859431/In_vitro_activity_of_rifaximin_metronidazole_and_vancomycin_against_Clostridium_difficile_and_the_rate_of_selection_of_spontaneously_resistant_mutants_against_representative_anaerobic_and_aerobic_bacteria_including_ammonia_producing_species_ L2 - https://www.karger.com?DOI=10.1159/000007297 DB - PRIME DP - Unbound Medicine ER -