Abstract

Seventy un-repeated Streptomyces isolates were isolated from different agricultural regions in Riyadh city. Amoxicillin-resistant Pseudomonas aeruginosa ATCC-10145 was obtained with minimum inhibitory concentration (MIC) > 1000 µg.ml^-1. Streptomycesisolates were screened for producing β-lactamase inhibitory effect against P. aeruginosaATCC-10145. There were ten Streptomyces isolates which had inhibitory effect. Although, one Streptomyces isolate has been considered the most potent, this was identified by using biochemical characteristics as Streptomyces chromofuscus. Optimization factors for maximum yield of β-lactamase inhibitory protein were studied. The best incubation period at 7th day, incubation temperature at 28°C, pH value at 6.8, the best carbon source was galactose and the best nitrogen source was prolin. The highest amount of β-lactamase inhibitory protein was precipitated at 40% of saturated ammonium sulphate. The purification was carried out by using both diethyl-aminoethyl-cellulose and sephadex G-200 column chromatography, respectively. The β-lactamase inhibitory protein was separated at 32 kDa. The purified β-lactamase inhibitory protein was characterized as tazobactam. The combination of tazobactam at 128 mg.L^-1 and amoxicillin at 125 µg.ml^-1(in vitro) leads to growth inhibition of amoxicillin-resistant P. aeruginosa and make it very sensitive to the amoxicillin.

Key words: Amoxicillin, enzyme inhibitors, protein purification, tazobactam