Skip Navigation



JAC Advance Access published online on September 1, 2003
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkg398
© 2003 by The British Society for Antimicrobial Chemotherapy
This Article
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
52/4/623    most recent
dkg398v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Houlihan, A. J.
Right arrow Articles by Russell, J. B.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Houlihan, A. J.
Right arrow Articles by Russell, J. B.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 2003 The British Society for Antimicrobial Chemotherapy

Original article

The susceptibility of ionophore-resistant Clostridium aminophilum F to other antibiotics

Adam J. Houlihan 1 and James B. Russell 2 *

1 Department of Microbiology, Cornell University, Wing Hall
2 Department of Microbiology, Cornell University, Wing Hall, and Agricultural Research Service, USDA, Ithaca, NY 14853, USA

* Corresponding author. E-mail: jbr8{at}cornell.edu.

Received 28 April 2003 ; revised 17 June 2003 ; accepted 2 July 2003

Abstract

Objective: To determine if ionophore-resistant ruminal bacteria are cross-resistant to other classes of antibiotics. Clostridium aminophilum was used as a model organism because this Gram-positive ruminal bacterium can adapt to ionophores (monensin and lasalocid). Non-adapted cultures lagged for at least 12 h with 1 µM monensin or lasalocid, but initiated no growth if the concentration was 10 µM. Adapted cultures did not lag with 1 µM monensin or lasalocid, grew well even if the ionophore concentration was 10 µM and contained cells at least 100 000-fold more resistant than those in non-adapted cultures.

Methods: Ionophore-adapted and non-adapted cultures were assayed for their susceptibility to other classes of antibiotics (penicillin G, ampicillin, cephalosporin C, vancomycin, carbenicillin, tetracycline, chloramphenicol, erythromycin, streptomycin, linocomycin, rifampicin, trimethoprim, novobiocin, polymyxin B and bacitracin) using a broth microdilution method.

Results: Adapted cultures retained their resistance phenotype for at least 28 generations even if ionophore was no longer present. Monensin-adapted cultures were as resistant to lasalocid as those adapted to lasalocid, but lasalocid-adapted cultures lagged with 1 µM monensin. Monensin- and lasalocid-resistant C. aminophilum F cultures were as susceptible to most antibiotics as non-adapted cultures. The only antibiotic that seemed to have a common mechanism of resistance was bacitracin, and the ionophore-adapted cultures had a 32-fold greater MIC.

Conclusion: The use of ionophores in cattle feed and the selection of ionophore-resistant ruminal bacteria does not necessarily lead to other types of antibiotic resistance.

Keywords: antibiotics, ionophores, resistance, monensin, lasalocid
Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.