In this report, we demonstrate that usnic acid causes

rapid and strong inhibition of RNA and DNA synthesis in Gram-positive bacteria, represented by Bacillus subtilis and Staphylococcus aureus, while it does not inhibit production of macromolecules (DNA, RNA, and proteins) in Escherichia coli, which is resistant to even high doses of this compound. However, we also observed slight inhibition of RNA synthesis in a Gram-negative XL184 bacterium, Vibrio harveyi. Inhibition of protein synthesis in B. subtilis and S. aureus was delayed, which suggest indirect action (possibly through impairment of transcription) of usnic acid on translation. Interestingly, DNA synthesis was halted rapidly in B. subtilis and S. aureus, suggesting interference of usnic acid with elongation of DNA replication. We propose that inhibition of RNA synthesis may be a general mechanism of antibacterial action of usnic acid, with additional direct mechanisms, such as impairment of DNA replication in B. subtilis and S. aureus. “
“The latest threat of multidrug-resistant Gram-negative bacteria corresponds to the emergence of carbapenemase NDM-1 (New Delhi metallo-β-lactamase) producers, mostly in Enterobacteriacae. Five blaNDM-1-positive plasmids of different incompatibility groups (IncL/M,

FII, A/C and two untypeable plasmids) from clinical Enterobacteriaceae were evaluated for conjugation properties and host specificity. Successful conjugative transfers were obtained using Neratinib all tested enterobacterial species as recipients (Escherichia coli, Klebsiella pneumoniae, Salmonella typhimurium and Proteus mirabilis) and all plasmid types. Conjugation frequencies varied from 1 × 10−4 to 6 × 10−8 transconjugants per donor. Higher conjugation rates were obtained for two plasmids at 30 °C compared with that observed at 25 and 37 °C. Carbapenems used as selector did not lead to higher conjugation frequencies. None of the five plasmids was transferable to Acinetobacter baumannii or Pseudomonas aeruginosa by conjugation. Isotretinoin This work underlines how efficient the spread of the carbapenemase blaNDM-1 gene could be among Enterobacteriaceae.

Carbapenem-hydrolysing β-lactamases identified in Enterobacteriaceae are the emerging threat for treating infected patients. New Delhi metallo-β-lactamase (NDM-1) confers resistance to all β-lactams except the monobactam aztreonam and is expressed in multidrug or pandrug-resistant isolates (Kumarasamy et al., 2010). The NDM-1 was identified first from Klebsiella pneumoniae and Escherichia coli isolates from a patient previously hospitalized in India (Yong et al., 2009) (hence its name). NDM-1 producers have been reported from all over the world except from South and Central America but mostly from the United Kingdom, India and Pakistan (Nordmann et al., 2011). It has been identified from Enterobacteriaceae and Acinetobacter baumannii isolates and recently from environmental Gram-negative rods (Nordmann et al., 2011; Walsh et al., 2011).