title: Inhibition of beta-lactamase production in gram-positive and gram-negative strains by sub-inhibitory concentrations of nalidixic acid.
abstract: We found it of interest to try to determine a microbiological parameter for the effects that sub-inhibitory doses of a chemotherapeutic agent may have on bacteria. To this end, the antibacterial activity of nalidixic acid was analyzed and our attention was directed to evidence of the production of beta-lactamase by 60 strains. The tests carried out showed that sub-inhibitory concentrations of nalidixic acid, from 2 to 64 times lower than the MIC (minimum inhibitory concentrations), were able to inhibit production of penicillinases in the 14 strains of Staphylococcus spp. tested, while only in 7 of the 21 strains of Gram-negative bacteria. Strains from our collection of beta-lactamase producing bacteria were analyzed, and our results confirmed that nalidixic acid inhibits plasmidic and chromosomic beta-lactamases.
mesh_terms: D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000201:enzymology*; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000201:enzymology*; D009268:Nalidixic Acid / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D009268:Nalidixic Acid; D001618:beta-Lactamases