Disease relevance of tetA

• Nucleotide sequence of class D tetracycline resistance genes from Salmonella ordonez [1].
• Plasmid pGFT1 was shown to be conjugative and to be able to replicate and express tetracycline resistance in Escherichia coli [2].
• A number of independent insertions into bacteriophage lambda of the translocatable tetracycline-resistance element Tn10 have been isolated and characterized [3].
• Frequency of four classes of tetracycline resistance determinants in Salmonella and Shigella spp. clinical isolates [4].
• The expression of extrachromosomal tet genes not only confers tetracycline resistance but also increases the susceptibilities of gram-negative bacteria to commonly used aminoglycoside antibiotics [5].

High impact information on tetA

• We show that the leu-500 promoter can function on a plasmid when it is adjacent to the tetracycline-resistance gene tetA [6].
• This is especially true when the plasmid carries a functional tetracycline-resistance gene tetA, and is borne in a topA strain of Escherichia coli or Salmonella typhimurium [7].
• Inversions and deletions of the Salmonella chromosome generated by the translocatable tetracycline resistance element Tn10 [8].
• The resistance genes included in the SXT constins were floR, tetA, strAB, and sulII, which encode resistance to chloramphenicol, tetracycline, streptomycin, and sulfamethoxazole, respectively [9].
• Two DT104 strains, showing resistance to streptomycin-spectinomycin and sulfonamides, carried a partially deleted SGI1 lacking the flo(st), tetR, and tetA genes, conferring chloramphenicol-florfenicol and tetracycline resistance, and the integron harboring the pse-1 gene cassette, conferring ampicillin resistance [10].

Chemical compound and disease context of tetA

• Class B tetracycline resistance determinants have been identified in two aerobactin-encoding FIme plasmids representative of those isolated from epidemic Salmonella wien [11].
• Genetic analysis of 131 independent transpositions of the tetracycline-resistance element Tn10 from a single site in phage P22 into the histidine operon of Salmonella typhimurium reveals that Tn10 insertions are not randomly distributed along this chromosomal target [12].
• To make a comprehensive study of tetracycline resistance determinant distribution in the genus Shigella, a collection of 577 clinical isolates of Shigella spp. and enteroinvasive Escherichia coli (EIEC) from a variety of geographical locations was screened to identify tetracycline-resistant strains [13].
• The resistance genes were cloned into the pACYC184 vector of Escherichia coli from a common plasmid of S. krefeld that encoded for resistance to ampicillin, chloramphenicol, kanamycin, streptomycin, sulphonamide and tetracycline resistance [14].
• Inhibition by paromomycin of R-factor transfer of tetracycline resistance between Escherichia coli and Salmonella pullorum [15].

Biological context of tetA

• We determined the nucleotide sequence of the pIP173 tetR repressor and tetA resistance genes [1].
• An analysis of the complete nucleotide sequence of the composite tetracycline-resistance transposon Tn10 (9147 bp) from the Salmonella typhi conjugative plasmid R27 is presented [16].
• Tetracycline resistance which was plasmid-mediated was the most common antibiotic resistance observed, and was carried by 23.8 per cent of all CJC isolates [17].
• A genomic library from one clinical isolate of Acinetobacter baumannii was obtained to find genes responsible for tetracycline resistance [18].
• Epidemiology of tetracycline resistance determinants in Shigella spp. and enteroinvasive Escherichia coli: characterization and dissemination of tet(A)-1 [13].

Anatomical context of tetA

• In an organ culture model, a mutant of S. typhimurium carrying a tetracycline resistance cassette inserted in pefC was found to be associated in lower numbers with murine small intestine than the wild-type [19].
• We have previously shown that this promoter can be activated on circular plasmids in a manner that depends on transcription and translation of the tetracycline resistance gene tetA and insertion of its product into the cell membrane [20].
• We demonstrate that the presence of the pSC101 derived tetracycline resistance gene on plasmids causes a lower survival rate of Salmonella in macrophages [21].

Associations of tetA with chemical compounds

• Approximately 89% of oxytetracycline-resistant strains carried the tetA gene and all of the 131 streptomycin-resistant isolates carried the aadA1a gene [22].
• Sulphonamide resistance was primarily mediated by sul2 and sul3, tetracycline resistance by tet(B) and tet(A), chloramphenicol resistance by catA1, streptomycin resistance by strA and ampicillin resistance by blaTEM. blaCTX and blaCMY-2 were found in cephalosporin-resistant isolates [23].
• This finding supports the contention that certain metal ions critically facilitate tetracycline uptake and leads us to suggest possible molecular mechanisms for tetracycline resistance [24].
• RESULTS AND CONCLUSIONS: dfrA25 encodes a dihydrofolate reductase of 157 amino acids with closest identity (85%) to dfrA5 dihydrofolate reductase. dfrA25 was located on a transferable plasmid ( approximately 150 kb) that also harboured the tetracycline resistance gene tet(A) [25].
• The collection was further characterized for extended-spectrum cephalosporin, aminoglycoside, and tetracycline resistance markers [26].

Analytical, diagnostic and therapeutic context of tetA

• METHODS: The S. enterica Agona strain was screened by PCR and DNA sequencing for TEM, SHV and CTX-M-type beta-lactamase genes, tet(A), (B), (C) and (D) tetracycline resistance genes, chloramphenicol resistance genes and class 1 integrons [27].
• Phage types, ribotypes and tetracycline resistance genes of Salmonella enterica subsp. enterica serovar Typhimurium strains isolated from different origins in Italy [28].
• Therapeutic antibiotic treatment of one group of chickens with oxytetracycline favoured the persistence of both the parent strain and, to a lesser extent, the marA inactivated strain; but interestingly, increased tetracycline resistance of Salmonella isolates after treatment of birds with antibiotic was seen only for the parent strain [29].

References