الفهرس 
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Abstract
Bacteria exist, in most environments, as complex organized communities of sessile cells embedded within a self-produced matrix. These communities are known as biofilms. Bacterial biofilms contribute to more than 80% of hospital-acquired and community-acquired infections. Pseudomonas aeurginosa (P. aeruginosa) is an important example of pathogens able to form biofilm.
The capability to form biofilm by this organism is considered as a virulence factor. Biofilm-related infections are challenging to treat and difficult to fully eradicate with normal treatment regimens. Quorum sensing (QS) is important in regulating the biofilm formation.
This study aimed to determin the ability of different P. aeruginosa clinical isolates to produce biofilm and its association with LasR gene, LecA gene and Pel A gene and antibiotic resistance.
In this study 100 isolates of P. aeurginosa were obtained from infected wounds from patients admitted to Minia University Hospitals.
All samples were cultured on Cetramide agar media then the isolated organisms were identified by colonial morphology, Gram staining and biochemical reactions. Antibiotic sensitivity of the isolated strains was done using disc diffusion method. The expression of Pel A gene, LecA and LasR gene in isolated strains was detected using real time rt-PCR technique.
The isolated bacteria were tested for their ability to form biofilm using microtitre plate assay.
It was found that:
1. 27 out of 100 isolates (27%) were positive biofilm producers: 14% were strong biofilm producers, 7% were moderate biofilm producers and 6% were weak biofilm producers.
2. 24 out of 100 isolates (24%) had the Pel A gene, 52out of 100 isolates (52%) had the Lec A gene while 43 out of 100 isolates (43%) had the Las R gene.
3. 18 0ut of 27 (66.7%) of biofilm producing strains expressed Pel A gene, 26 out of 27 (96.3%) of biofilm producing strains expressed Lec A gene while 20 out of 27 (74.1%) of biofilm producing strains expressed Las R gene and their expression was statistically significant to biofilm production.
4. The isolates were most sensitive to imipenem (91%) followed by amoxicillin-clavulanate (66%) then ceftazidime(61%), while least sensitive to levofloxacin (56%) followed by amikacin (44%).
5. Resistance to all used antibiotics and MDR were higher among biofilm producing than non-biofilm producing strains, but the difference was statistically non-significant.
Conclusion
1- The degree of biofilm formation differs between different P. aeurginosa strains.
2- Lec A, Las R and Pel A genes have a significant role in biofilm formation.
3- Imipenem is highly effective against P. aeurginosa in vitro.
4- Biofilm producing strains have higher resistance to antibiotics even in their planktonic form than non-biofilm producing strains.
Recommendations
1. Large scale studies on a large number of P. aeruginosa clinical isolates to study their abilities to form biofilm and its relation to Lec A, Pel A and Las R genes and antibiotics resistance.
2. Study the effect of Las R, Lec A and Pel A inhibition on biofilm control.
3. Study other P. aeruginosa QS genes for better understanding their role in controlling biofilm formation.
4. Many researches are needed to find easier methods for diagnosing biofilm infection and to develop more specific antimicrobial agents and methods for eradication or inhibition of biofilm.
5. Measurment of minimal biofilm eradication concentration rather than minimal inhibitory concentration is recommended to be done for biofilm incriminated infections.