Influencc of B-lactamase inhibitors on the activity of oxacillin and four quinolone agents against resistant staphylococcus aureus

The influence of some Beta-lactamase inhibitors on the activity of four quinolones against 78 isolates of methicillin-resistant Staphylococcus aureus [MRSA] was tested by the minimum inhibitory concentration [MIC] method. All 78 strains were found by the rapid chromogenic cephalosporin method to be Beta-lactamase producer. The addition of 8 ug/ml of tazobactam to oxacillin had decreased the MICs from 8 to 32 folds, while the addition of 8 ug/ml of clavulanic acid had decreased the MICs only two fold. The addition of 2 ug/ml of clavulanic acid, sulbactam, and tazobactam to levofloxacin did not affect the MICs at all. The only effect observed was a two-fold decrease of the MICs when we added 8 ug/ml of the three inhibitors. The addition of 2 ug/ml of the three inhibitors to ofloxacin, lomefloxacin, and ciprofloxacin did not improve the MICs at all and 8 ug/ml decreased the MISs from two-fold to four-fold. The results of this study suggest that Beta-lactamase production plays a role in resistance to the four quinolones tested in those MRSA strains of low-level quinolone resistance

Comparative antimicrobial activity of three quinolones, tetracyclines, doxycycline and minocycline against mycoplasma pneumoniae, mycoplasma hominis and ureaplasma urealyticum

Agar dilution technique was used to compare the antimicrobial activites of temafloxacin, sparfloxacin, ofloxacin, tetracycline, doxycycline and minocycline against 69 isolates of M. pneumoniae, 47 isolates of M. hominis and 38 isolates of U. urealyticum. Among the three quinolones agents tested, sparfloxacin was the most active agent against all the isolates. Doxycylcine has better activity than tetracycline against all the isolates. U. urealyticum were highly susceptible to minocycline and sparfloxacin with MIC90 of 0.35 micro g/ml and respectively. Among the six antibiotics tested the most active agent was sparfloxacin against M. pneumoniae and M. hominis and minocycline against U. urealyticum. Tetracycline and ofloxacin were the least active agents against all the isolates

Antimicrobial activity of fusidic acid against some bacterial eye isolates

The in-vitro activity of fusidic acid against 113 bacterial eye isolated [107 gram positive and 6 gram negative] was investigated by agar dilution and both micro- and macrodilution methods. The results show that fusidic acid is very effective against all the gram-positive isolates with best inhibition against Staphylococcus aureus [non- penicillinase-producing] [MIC95 < 1.4 mug/ml]. All gram-negative isolates were sensitive to fusidic acid [MIC95 < mug/ml] with the exception of Pseudomonas spp. [MIC95 > 100 mug/ml]. It is concluded that fusidic acid proved to be an effective antibiotic for the treatment of bacterial eye infections caused by one of those susceptible strains