Efficacy of different antibiotic combinations on uropathogenic multi-drug resistant Escherichia coli

Using checkerboard titration method as well as time-kill curve technique, the potential synergy of combinations of beta-lactams [ceftazidime and cefepime], aminoglycosides [amikacin, gentamicin, and tobramycin] and fluoroquinolones [ciprofloxacin, levofloxacin, and ofloxacin] were compared against multidrug resistant uropathogenic Escherichia coli isolated from patients with urinary tract infections. In the checkerboard titration studies, none of 21 combinations demonstrated antagonism against 8 strains, five of the 21 combinations showed synergism for more than 40% of the test strains, i.e. ceftazidime tobramycin, ceftazidime levofloxacin, amikacin levofloxacin, amikacin with ofloxacin, and tobramycin with levofloxacin, synergy occurred more often with levofloxacin combined with amikacin [7/8 strains]. Corresponding to the respective fractional inhibitory concentration [FIC] indices, the bactericidal activity determined in combinations of amikacin with ceftazidime or levofloxacin at sub-minimum inhibitory concentrations produced a significant reduction in bacterial count [>/= 2 log 10 cfu/ml] observed within 6 hours of drug administration, at 24 hours, both combinations were bactericidal [reduction in colony count >/= 3 log 10]. Results of this study suggest that amirioglycosides [amikacin and or tobramycin] combination with levofloxacin or ceftazidime could be promising alternatives for the treatment of serious urinary tract infections due to multi drug resistant E. coli

Rational approach towards improving the predictive effectiveness of official antimicrobial challenge tests

Comparative resistance of naturally occurring strains of Pseudomonas aeruginosa and E. coli and type cultures of the same species to the preservatives was assessed. Some of the factors affecting their responses were also examined. The results indicated that minimum bactericidal concentration value [MBC] of E. coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027 were much lower than those of the environmental strains. This suggested that type culture organisms should be cultivated in conditions relevant to actual environmental in the pharmaceutical and cosmetic production field where they are subjected to starvation and many other stresses. The comparison between the usual pharmacopoeial cultivation method and multinutrient starved in different dilutions of trypticase soy agar showed that starved organisms had much higher D-values. The D-values of starved organisms increased with increasing of TSB dilution up to 10[-3]. Most air conditioned area in production field are adjusted at 20-25°C. Growth of starved organisms at 23°C showed highest homogeneous antimicrobial response curve. Thus this study suggested usage of multinutrient starved organisms. The results showed that the starved type culture strains were more aggressive than strains isolated from contaminated batches of the above products or from their water for preparation. While the nutrient amended ATCC type strains showed the least aggressiveness ability. The significance of these findings may alter the present concept of preservation testing systems as well as routine control procedures in cosmetic and pharmaceutical preparations

Studies on the asparaginolytic activity of the brown-pigmented streptomycetes

Twenty-eight brown-pigmented streptomycetes were isolated from different fertile Egyptian soils. Screening was carried out according to their asparaginolytic activity under static culture condition on glycerol- L-asparagine [GA] medium. Results revealed that FS-39 isolate gave the highest asparaginolytic activity. Therefore, it was selected and subjected to complete identification. The cultural, morphological and physiological characteristics of this isolate indicated that it belongs to Streptomyces phaeochromogenes. The effects of nutritional and environmental conditions on the asparaginase activity of Streptomyces phaeochromogenes FS-39 were studied. Data revealed that the maximal, yield of L-asparaginase from this strain can be obtained by growing it on glycerol-L-asparagine yeast extract [GAY] medium containing [w/v] 2.0% Glycerol, 0.2% L-asparagine, 0.1% yeast extract, 0.1% K[2]HPO[4].3H20, 0.0001% FeSO[4].7H[2]0, 0.0001% MnCl[2]. 4H[2]0, 0.0001% ZnSO[4].7H[2]O which was initially adjusted to pH 7.0, inoculated by 2% [v/v] of homogenized spore suspension [containing approximately 3.2x10[7] spores/ml] of 3 days old culture on starch nitrate medimi and incubated at 30°C for 7 days under static culture condition

Puriffication and characterization of L-asparaginase produced by Streptomyces phaeochromogenes FS-39

An L-asparaginase [EC.3.5.1.1] produced by Streptomyces phaeochromogenes FS-39 was purified and characterized. After initial ammonium sulfate fractionation [50-70% saturation], the enzyme was purified by consecutive column chromatography on ion exchange [DEAE-Cellulose] and Sephadex G-200 filtration. The 67.2 fold purified enzyme thus obtained has the specific activity of 179.14 units mg protein super [-1] with an over all recovery of 17.7%. The enzyme was characterized by demonstration of optimum activity at 35°C and pH 8.5. It was stable for 180 min. at 30-35°C and 7 days at 4°C [refrigerator] and pH range from 8.0 to 9.0. The enzyme activity was slightly stimulated by Mg supper [2+], Fe super [2+] and Ca super [2+] cations, but Na-azid and EDTA did not exert any effect on the enzyme activity. Hg super [2+], Ag super [+] and Cu super [2 +] cations as well as L-cysteine, iodine, KCN and iodoacetic acid strongly inhibited the enzyme, but Zn super [2+], KMnO4 and super [2+] potentially slightly inhibited the enzyme activity. L-aspartic acid was competitive inhibitor