Les Métallo-Beta-Lactamases -recherche de souches bactériennes productrices -Essais d’inhibition de l’activité enzymatique relative par trois flavonoïdes commerciaux et deux extraits de Terminalia chebula

Abstract

Four extracts were prepared: one aqueous, one methanolic, are from dried fruits of Terminalia chebula and two semi-purified extracts of beta-lactamases, one from a strain of Acinetobacter baumannii and the other from Pseudomonas aeruginosa (clinical isolates), identified among eight others by the CDT test as producing metallo and serine beta-lactamases, respectively. Quantitative and qualitative analyzes show that the first two are rich in polyphenols (513.094±3.061 and 496±2.856 µg GAE/mg, respectively) and flavonoids (39.866±0.469 and 37.261±0.272 µg QE /mg, respectively); the last two are rich in proteins (7.9 and 8.9 mg/ml, respectively). The semi-purified extract of beta-lactamases from Acinetobacter baumannii, hydrolyzes imipinem (KM = 57.52µM, Vm = 47.62 µmol/mg/min), its enzymatic activity is sensitive to EDTA (IC50 = 3.98 mM), hydrolyzes cephaloridin much more than benzylpenicillin; beta-lactamases contained therein could be so metallo-beta-lactamases type, 3c class. It is inhibited competitively by morin, aqueous and methanolic extracts from dried fruit of T.chebula (IC50= 23.28 µM, 18.45 and 19.68 µg/ml, in order), non-competitively by myrecitin and rutin (IC50 = 26.39 and 39.71 µM, respectively). The second extract from P.aeruginosa does not hydrolyze the imipinem, its enzymatic activity is insensitive to clavulanic acid, EDTA and NaCl and hydrolyzes cephaloridin much more than benzylpenicillin; beta-lactamases contained herein could be so serine beta-lactamases type, C class. It is inhibited competitively by morin, rutin, methanolic and aqueous extracts of dried fruits T.chebula (IC50 = 30, 21.03 µM, 7.04 and 12.07 µg/ml, respectively); non-competitively by myrecitin (IC50 = 27.10 µM). The comparison of IC50 of the three flavonoids to those of methanolic and aqueous extracts from dried fruit of T.chebula, assume that they are rich in flavonoids much closer to that of morin structure. The test demonstrated the antagonist or potentiating effects shows that the methanolic extract potentiates relatively the effect of imipenem on the growth of A.baumannii.