JAC Advance Access published online on May 16, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn209
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Research letter |
Occurrence and diversity of the tetracycline resistance gene tet(M) in enteric bacteria of Antarctic Adélie penguins
1 Centre for Marine Environmental Studies (CMES), Ehime University, Matsuyama 790-8577, Japan 2 Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
* Corresponding author. Tel/Fax: +81-89-927-8551; E-mail: ssuzuki{at}agr.ehime-u.ac.jp
Key Words: Antarctica , marine ecosystem , drug resistance , ribosomal protection protein , selective pressure
The tet(M) gene has been found in numerous bacterial genera isolated from various environments.1 However, there is no report on the investigation of the tet(M) gene in Antarctica. We investigated the occurrence of tet(M) in the isolates from Antarctic Adélie penguins (Pygoscelis adliae) and detected two different genotypes of tet(M).2
Sampling was carried out from Adélie penguins colonizing Hukuro Cove (69°13' S, 039°39' E), Lützaw-Holm Bay, Antarctica, from December 2004 to February 2005, as an activity of the 45th Japanese Antarctic Research Expedition (JARE45). Intestinal contents (faeces) were collected by insertion of a sterilized cotton swab into the cloaca. Viable bacterial count was performed on marine broth 2216E (Difco) plus 1.5% BactoTM agar containing 0 or 30 mg/L tetracycline. The plates were incubated at 25°C for 7 days, and colonies were counted. Chromosomal DNA was extracted from 23 tetracycline-resistant (Tcr) isolates. Isolates were classified by 16S rDNA analysis. Specific primers for tet(M) detection, tet(M)-1 (5'-GTTAAATAGTGTTCTTGGAG-3') and tet(M)-2 (5'-CTAAGATATGGCTCTAACAA-3'), were used for PCR; the product length was expected to be 657 bp.2,3 The PCR products were cloned and sequenced.
The Tcr bacteria represented 0% to 0.54% of the total viable count. The Tcr bacteria included isolates from the following genera: Bacillus, Brachybacterium, Streptomyces, Arthrobacter, Psychrobacter and Pseudomonas (Table 1). Currently, 40 Tcr genes have been reported (http://faculty.washington.edu/marilynr/). Among these, the tet(M) gene has been detected in a wide range of bacterial species and is the most widely distributed. Thus, carriage of the tet(M) gene was determined. Of 23 isolates, 10 were Tcr and carried the tet(M) gene, and included 10 Bacillus spp., 4 Brachybacterium spp., 2 Streptomyces spp. and 1 Pseudomonas sp. (Table 1). To our knowledge, this is the first study on the detection of tet(M) in an animal endemic to Antarctica. This study is the first description of acquired tet genes [tet(M)] in either Brachybacterium or Arthrobacter. We also suggest that Antarctic Adélie penguins may act as a reservoir for Tcr bacteria because they have the potential to spread these Tcr bacteria to their young through regurgitation feeding and throughout the Antarctic ecosystem via faecal contamination.
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This study was partly supported by Grants-in-Aid from the 21st Century-COE and Global-COE Programmes (MEXT) and Grants-in-Aid from JSPS (14208063).
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None to declare.
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Acknowledgements |
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We thank Dr Todd Miller for his critical review of the manuscript.
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1 . Roberts MC. Tetracycline resistance determinants: mechanisms of actions, regulation of expression, genetic diversity, and distribution. FEMS Microbiol Rev (1996) 19:1–24.[CrossRef][Web of Science][Medline]
2 . Nonaka L, Ikeno K, Suzuki S. Distribution of tetracycline resistance gene, tet(M), in Gram-positive and Gram-negative bacteria isolated from sediment and seawater at a coastal aquaculture site in Japan. Microbes Environ (2007) 22:335–64.
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Chopra I, Roberts MC. Tetracycline antibiotics: mode and action, application, molecular biology, and epidemiology of bacterial resistance. Microbiol Mol Biol Rev (2001) 65:232–60.
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