ABSTRACT
Letters of the English alphabet have heretofore been used to name tetracycline resistance determinants. Since all 26 letters have now been used, a nomenclature employing numerals is recommended for future determinants, and one laboratory has offered to coordinate the assignment of numerals.
In 1989, a Note describing the nomenclature for tetracycline resistance determinants which employed letters of the English alphabet was published in this journal (14). Since no letters now remain for designating additional determinants, we propose that new determinants be hereafter designated by Arabic numerals. The new system is patterned on the previous letter-based one, with a numeral used instead of a letter to name a determinant. Since 30 determinants have been described (most, but not all, according to the 1989 nomenclature, with the new 1999 nomenclature being used for Tet 30) (Table 1), the next determinant would receive number 31, with no renaming of the earlier determinants. Following the previous system used with letters, the class would be 31, and the determinant would be designated Tet 31 (with a space between “Tet” and “31”). If there were only a single gene in the determinant, it would be designatedtet(31). If there were more than one structural gene, the first would be designated tetA(31) and the second would betetB(31), etc. A regulatory gene would be designatedtetR(31). Note that the class designation, 31, is not italicized. The names of the corresponding proteins would be Tet(31) or TetA(31), etc. An allele of a gene would be designated by a hyphen followed by an italicized allele number; for example,tetA(31)-1 would be allele number 1 of thetetA gene of class 31. If the class designation is not needed within a single communication, it could be omitted.
Known tetracycline resistance determinantsa
This system employs some of the conventions from the previous communication (14) and is summarized in Table2. Usage for previously described determinants should continue to conform to the prior recommendations (14).
Proposed nomenclature for new tetracycline resistance determinants
Recently, there have been several situations in which tetracycline resistance determinants discovered in different laboratories were nearly given the same designation. To avoid such a problem in the future, we offer the S. B. Levy group to coordinate the naming of new determinants. Such a determinant can be defined as a naturally occurring unit of one or more adjacent genes involved primarily in tetracycline resistance (as opposed to multidrug resistance or other known function) having a sequence significantly different from sequences of currently known determinants. We suggest ≤80% amino acid identity as the dividing line, based on previous usage. Class L has been defined as a single class even though it contains two subgroups in which the single proteins only are 81% identical (25, 26), while the proteins of two different classes, M and S, are 79% identical (4, 25). To confirm that a number proposed for a newly discovered tetracycline resistance determinant has not been used, please contact S. B. Levy.
Finally, we note that when looking in databases for a name containing parentheses or a space, such as “tet(X)” or “Tet X”, quotation marks should be used around the name, as shown, to retrieve the term intact.
ACKNOWLEDGMENTS
This work was supported by grant GM55430 from the National Institutes of Health.
FOOTNOTES
- Received 24 February 1999.
- Accepted 24 March 1999.
- Copyright © 1999 American Society for Microbiology
