Anhydrochlortetracycline

One hundred Escherichia coli isolates from diseased and healthy pigs, cattle and broiler chickens were screened for the presence of tetracycline resistance genes tet(A), (B), (C), (D) or (E). The tet(A) gene was the most abundant (71% of the 100 isolates) followed by tet(B) (25%). The predominance of tet(A) and tet(B) applied to all three animal species, and there was no difference between the distribution of tet(A) and tet(B) genes among non-pathogenic and pathogenic E. coli in any of the animal species. The susceptibility of 20 of these isolates together with 10 tetracycline sensitive E. coli and 18 tetracycline resistant and 10 sensitive Enterococcus faecium to tetracyclines and tetracycline degradation products was determined. The resistant isolates showed reduced resistance to anhydrotetracycline, 4-epi-anhydrotetracycline, anhydrochlortetracycline and 4-epi-anhydrochlortetracycline. In general both the tetracycline resistant and susceptible E. faecium were more susceptible to the compounds tested than E. coli.

Inland water is very susceptible to the input of pollutants. However, little is known about the occurrence of antibiotics in inland lakes. In this study, a total of 83 target antibiotics were quantified in water and sediment samples collected from the Qinghai Lake, the largest inland lake of China located on the northeast of Qinghai-Tibet plateau, and its inflowing rivers. The results showed that 27 and 25 antibiotics were detected in water and sediments, respectively, with the summed concentrations (SUM) of 1.14-17.3 ng/L and 0.72-8.31 ng/g. Compared with the input rivers, significantly higher levels of sulfonamides (SAs), quinolones (QNs), polyethers (PEs), and SUM in water samples were observed in Qinghai Lake water. The average proportions of SAs (50.9-52.7%) and QNs (22.0-28.3%) in Qinghai Lake water nearly doubled compared to those in input rivers. An enrichment factor (EF) was proposed to reveal the enrichment degree of antibiotics in Qinghai Lake compared to its input river water. Sulfaguanidine (SGD), flumequine (FLU), and nalidixic acid (NDA) were enriched in Qinghai Lake up to several ten times based on the calculated EF values, due to their persistence in such a cold saline lake. Risk assessment showed that most antibiotics except anhydrochlortetracycline (ACTC) had insignificant risks to aquatic organisms and antibiotic resistance selection in Qinghai Lake water. This study was the first to reveal the enrichment of antibiotics in Qinghai Lake water, and suggests the urgent need to investigate the possible long-term enrichment and environmental risks of antibiotics in inland lakes.

Tetracycline analogs fell into two classes on the basis of their mode of action. Tetracycline, chlortetracycline, minocycline, doxycycline, and 6-demethyl-6-deoxytetracycline inhibited cell-free translation directed by either Escherichia coli or Bacillus subtilis extracts. A second class of analogs tested, including chelocardin, anhydrotetracycline, 6-thiatetracycline, anhydrochlortetracycline, and 4-epi-anhydrochlortetracycline, failed to inhibit protein synthesis in vitro or were very poor inhibitors. Tetracyclines of the second class, however, rapidly inhibited the in vivo incorporation of precursors into DNA and RNA as well as protein. The class 2 compounds therefore have a mode of action that is entirely distinct from the class 1 compounds, such as tetracycline that are used clinically. Although tetracyclines of the second class entered the cytoplasm, the ability of these analogs to inhibit macromolecular synthesis suggests that the cytoplasmic membrane is their primary site of action. The interaction of class 1 and class 2 tetracyclines with ribosomes was studied by examining their effects on the chemical reactivity of bases in 16S rRNA to dimethyl sulfate. Class 1 analogs affected the reactivity of bases to dimethyl sulfate. The response with class 2 tetracyclines varied, with some analogs affecting reactivity and others (chelocardin and 4-epi-anhydrotetracycline) not.