Evaluación del ácido etilendiaminotetraacético y del mercaptoacético de sodio en la detección de metalo β-lactamasas en Pseudomonas aeruginosa mediante la técnica del disco combinado

pseudomanas aeruginosa is a gram negative bacillus capable of acquiring genes which code for metallo β-lactamase production (mbls) which are active against carbapenems and inhibited by chelating agents such as ethylenediaminetetraacetic acid (edta). we determined the effectiveness of edta and sodium mercaptoacetic acid (sma) in the detection of mbls on 25 p. aeruginosa strains from different hospitals and research centers, using the combined disk technique. we evaluated the effect of the antibiotics alone and combined with edta, sma, or both. we found that through the increase of the diameter of the inhibition halos of the carbapenems combined with an edta/sma mixture (0.5 m/300 mg/ml) o with edta alone (0.5 m), we could differentiate in a clear and reliable way the mbls producing from the non producing strains, establishing as cutoff point a difference of 5 mm or more between the antibiotic alone and the antibiotic combined with the chelating agent(s).