The present study included the collection of 144 samples from various clinical and environmental  sources  to investigate the presence of P.aeruginosa. 45 isolates were identified as P.aeruginosa  based on morphological and biochemical tests in addition to molecular diagnostics  used of 16S rRNA. This diagnosis proved that all isolates belong to P. aeruginosa. All isolates selected susceptibility toward 11 antibiotics using disc diffusion method. The results showed a high resistance among isolates against Tetracycline, Cefixim, Cefotaxim, Amoxicillin,   Erythromycin, Methicillin, Cloxacillin and Naldixic acid, and moderate resistance towards Meropenem and low resistance towards Imipenem and Ciprofloxacin. To determine the types of some genes responsible for Extended Spectrum Beta- Lactams (ESBLs) in P. aeruginosa using polymerase chain reaction (PCR) was used for detecting genes, (OXA-10), (OXA-4) and (VEB-1). The results showed that two isolate positive  to (OXA-10), (OXA-4) and (VEB-1), while 43 isolates were negative to (OXA-10), (OXA-4) and (VEB-1).  Detection of gene expression was performed by Quantitative Real Time PCR  technique after RNA was extracted from isolate treated with plant extract of Thymus vulgaris and  Amoxicillin. The result showed that gene expression was low expression after treatment with plant extract and Amoxicillin.