Two tetracycline resistance genes of Streptomyces rimosus, an oxytetracycline producer, were cloned in Streptomyces griseus by using pOA15 as a vector plasmid. Expression of the cloned genes, designated as tetA and tetB was inducible in S. griseus as well as in the donor strain. The tetracycline resistance directed by tetA and tetB was characterized by examining the uptake of tetracycline and i...

The expression of R-factor-mediated resistance to tetracycline has been compared in Proteus mirabilis and Escherichia coli. Resistance to a range of concentrations of tetracycline was significantly lower in P. mirabilis than in E. coli in both induced and repressed states. Indirect evidence showed that conditions which result in a marked increase in the level of resistance of P. mirabilis harbo...

AIM To compare the prevalence of antibiotic resistance found in nasopharyngeal Streptococcus pneumoniae between villages treated with topical tetracycline or systemic azithromycin as part of a trachoma control programme. METHODS All children aged 1-10 years were offered either single dose oral azithromycin treatment (20 mg/kg) or a course of topical 1% tetracycline ointment, depending on the ...

A global sample of group A streptococci (GAS) revealed > or =80 separate acquisitions of tetracycline resistance. Of 244 clones, 38 and 25% displayed resistance to tetracycline and erythromycin, respectively; a relatively high proportion (15%) were resistant to both classes of drugs. tet(M) displayed a highly significant association with erm(B).

A comparative study was done on the transfer frequency of R factors from 90 strains of multiple drug-resistant Aerobacter and 81 strains of Klebsiella to Escherichia coli CSH-2 (F(-), met(-), pro(-), Nal-r). The most common resistance patterns for the Aerobacter isolants were ampicillin streptomycin chloramphenicol tetracycline and ampicillin streptomycin chloramphenicol tetracycline kanamycin ...

Tetracycline uptake into inverted membrane vesicles from Tn10-bearing Escherichia coli cells required divalent cations. The degree of the stimulation of tetracycline uptake by various divalent cations showed the following decreasing order: Co2+ greater than Mn2+ greater than Mg2+ greater than Cd2+ greater than Ca2+. This order is consistent with the increasing order of the dissociation constant...

AIM This study was devoted to elucidate the tetracycline resistance of coagulase-negative staphylococci (CNS) derived from normal and subclinical mastitic (SCM) buffaloes' milk in Egypt. MATERIALS AND METHODS A total of 81 milk samples from 46 normal buffalo milk samples and 35 SCM buffalo milk samples at private dairy farms of Egypt were used in this study. CNS were identified using phenotyp...

The mechanism of tetracycline resistance was examined in strains containing each of the three previously identified resistance determinants in Streptococcus spp. Uptake of tetracycline was measured in tetracycline-sensitive cells as well as in cells containing each of the three resistance determinants. In cells containing tetL, uptake was not observed. However, in sensitive cells and cells cont...

1. E8cherichia coli with an R-factor conferring resistance to tetracycline was induced to high-degree resistance by pre-exposure to the antibiotic. The degree of resistance was drastically lowered by subjecting the cells to osmotic shock. 2. Resistance to tetracycline was rapidly restored by incubating the shocked cells in a glucose-salts medium containing shock proteins prepared from tetracycl...

The tetracycline resistance gene tet(K) was shown to be integrated within the predominant staphylococcal cassette chromosome mec (SCCmec) element of Danish livestock-associated methicillin-resistant Staphylococcus aureus CC398 (LA-MRSA CC398). These LA-MRSA CC398 isolates already possessed tet(M), but the acquisition of tet(K) significantly improved their fitness at sublethal concentrations of ...