Nucleotide Sequence Analysis of the Class G Tetracycline Resistance Determinant from Vibrio anguillarum

Abstract

The nucleotide sequence of the class G tetracycline resistance determinant previously isolated from Vibrio anguillarum has been determined. Two open reading frames of divergent polarity were identified. A resistance gene (tet A) encodes a protein of 393 amino acid residues (deduced molecular mass of 40.9 kDa), and a repressor gene (tet R) encodes a protein consisting of 210 amino acids with a calculated molecular mass of 23.6 kDa. Based on the deduced amino acid sequences, the proteins of tet A(G) and tet R(G) are about 60% homologous with those of RP1/ Tn1721 (class A) and pSC101/pBR322 (class C), and about 50% homologous with Tn10 (class B). The relationship of the tet (G) sequence to five known tetracycline resistance determinants (class A to E) is discussed.Tetracycline resistance (TCr) determinants are widespread among bacterial species. Five classes of TCr determinants (A through E) defined by DNA-DNA hybridization have been described among Enterobacteriaceae (16, 18). They are encoded by either plasmids or transposons and share the resistance mechanism involving active efflux of the drug from resistance cells (17,18). Each of them consists of the resistance gene tet A and the repressor gene tet R, which have divergent polarities and overlapping promoters (12, 23). The resistance gene encodes a membrane-associated protein (Tet A) which is responsible for resistance (7, 13). The repressor gene encodes a regulatory protein (Tet R) that has been characterized as interacting with tetracycline and the tet operator (9, 11). The nucleotide sequences of three resistance genes (27) and five repressor genes (23) have been determined. About 40-60% homology was revealed among encoded proteins of the three resistance genes as well as the five repressor genes (23).Vibrio anguillarum is a gram-negative fish pathogenic bacterium. It is a causative agent of vibriosis in marine and freshwater fish throughout the world. Infections with multiple drug-resistant strains of V. anguillarum have been found in cultured ayu (Plecoglossus altivelis) in various areas of Japan since 1973 (1). These strains were usually resistant to ampicillin, chloramphenicol, colistin, nalidixic acid, nitrofurazone, sulfonamides, streptomycin, tetracycline (TC) and/or trimethoprim. In most cases, these resistant strains carried a transferable R plasmid. In a previous study, a tetracycline determinant (designated class G) was cloned from a V. anguillarum strain MZ8122 carrying the R plasmid pJA8122 (2). This determinant does 105 1

Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

“…A floR homolog was first identified on a plasmid in Pasteurella piscicida recently renamed Photobacterium damselae, a fish pathogen [80]. In addition, the class G tetracycline resistance gene associated with the floR gene in the S. Typhimurium DT104 antibiotic resistance gene cluster was first identified in Vibrio anguillarum, also a fish pathogen [157]. The tet(G) gene has also been detected on plasmids of Photobacterium damselae [81].…”

Molecular characterization, spread and evolution of multidrug resistance in Salmonella enterica Typhimurium DT104

“…A floR homolog was first identified on a plasmid in Pasteurella piscicida recently renamed Photobacterium damselae, a fish pathogen [28]. In addition, the class G tetracycline resistance gene associated with the floR gene in the DT104 antibiotic resistance gene cluster was first identified in Vibrio anguillarum, also a fish pathogen [56]. The tet(G) gene has also been detected on plasmids of Photobacterium damselae [27].…”

Sequence of a class E tetracycline resistance gene from Escherichia coli and comparison of related tetracycline efflux proteins

“…Recent studies of the TnJO TetA protein have shown that it functions as a tetracycline/proton antiporter and that the species transported out of the cell is a divalent metal-tetracycline complex (57,60). Sequences for both tetA and tetR have been reported for class A (52), class B (tetA [19,34]; tetR [37]), class C (tetA [36]; tetR [46]), class D (tetA [2]; tetR [47]), and class G (62). For class E, the sequence of the tetR gene but not the tetA gene has been reported (45).…”

“…family Enterobacteriaceae and related genera, resistance is most often due to a family of related tet genes (classes A through E and G), all of which mediate tetracycline efflux (26,27,29,62). The plasmids and transposons that define these six classes are RP1 and Tnl721 (class A), TnlO (class B), pSC101 and pBR322 (class C), RA1 and pIP173 (class D), pSL1456 (class E), and pJA8122 (class G).…”