الفهرس 
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Abstract
Efflux mechanisms of resistance, both drug specific and multi-drug are
important determinants of intrinsic and/or acquired resistance to antimicrobials.
This study aimed to determine the effect of verapamil on MICs of
levofloxacin, ciprofloxacin and norfloxacin against P.aeruginosa isolates.
This study was conducted on 118 hospitalized patients in Zagazig
University Hospital with the age groups between 7-70 years, and on 40
environmental samples.
Different clinical samples were collected and subjected to:
Cultivation on nutrient agar plates.
Cultivation on Mact.onkeys agar plates.
Identification of isolates by growth characters (colonial morphology,
characteristic smell and pigment production), Gram stained. smear,
biochemical reactions (oxidase test, citrate utilization test, motility test,
catalase test and triple sugar iron), and API 20 E.
The 158 samples revealed 30 P.aeruginosa isolates were detected by
cultivation on nutrient agar, biochemical reactions and API 20 E.
As regarding possible resistance mechanism by phenotypic methods, all
isemginsa isolates were ESBL producers.
The antimicrobial activity of levofloxacin, ciprofloxacin and norfloxacin
las determined. It was found that Piaeruginosa isolates had MIC ranged from
~,9ug/ml-250 ug/ml) oflevofloxacin, 13 (43.3%) isolates showed MIC above
break point of levofloxacin ~ 8 ug/ml, P.aeruginosa isolates had MIC