The College of Medicine at the University of Babylon, Department of Microbiology, discussed the master’s thesis of graduate student Um Al-Baneen Raed Rommel titled
“A Molecular Study of Virulence Factors and Antibiotic Resistance Patterns of Pseudomonas aeruginosa Isolated from Hospitalized Patients”,
supervised by Professor Jawad Kadhim Al-Khafaji and Professor Lubna Abdul Azeem Al-Bayati.
The defense session was attended by Assistant Professor Dr. Ashraf Mohammed Ali Hussein, the Scientific Assistant Dean, along with several faculty members, academicians, and postgraduate students.
During her defense, the researcher explained that 100 clinical samples were collected from patients suffering from various infections, including wound infections, urinary tract infections, respiratory tract infections, and burn infections. The samples were obtained from patients admitted to Imam Al-Sadiq Teaching Hospital and Hilla Teaching Hospital in the city of Hilla during the period from January to February 2025.
Each sample was aerobically cultured on selective and differential media that support bacterial growth. The results showed that 66 out of 100 samples (66%) exhibited bacterial growth, while 34 samples showed no growth.
Pseudomonas aeruginosa isolates were identified from the positive samples using biochemical tests on selective media, in addition to the Vitek automated identification system.
The distribution of isolates by infection site revealed that the highest proportion was found in urine samples (27 isolates, 41%), followed by sputum (15 isolates, 23%), burn wounds (12 isolates, 18.18%), and skin wounds (11 isolates, 17%).
Antibiotic susceptibility testing was performed using the disk diffusion technique to determine resistance patterns against 11 clinically important antibiotics. The isolates demonstrated high resistance to Colistin (95.45%), as well as elevated resistance rates to Tobramycin, Cefepime, Ciprofloxacin, Aztreonam, Norfloxacin, Piperacillin, Meropenem, Gentamicin, Ceftriaxone, and Azithromycin, indicating a broad-spectrum resistance pattern.
A molecular analysis was also conducted to detect quorum-sensing (QS) genes in all P. aeruginosa isolates. The results showed that LasI and LasR genes were present in 73% of isolates, detected using specific molecular primers at gene fragment lengths of 295 bp and 130 bp, respectively. These genes play a central role in regulating virulence factor production, suggesting that the loss of one or both genes may weaken the bacteria’s ability to cause infection.
Furthermore, antibiotic resistance genes, particularly those associated with ?-lactam antibiotics, were detected. The study revealed the presence of the blaIMP gene in 18.18% of isolates and the blaNDM gene in 17%, confirmed using specialized primers at fragment sizes of 578 bp and 782 bp, respectively. These genes encode enzymes that inactivate carbapenem antibiotics such as imipenem and meropenem, thereby enhancing the bacteria’s resistance capacity.
In another part of the study, the antimicrobial activity of silver nanoparticles (AgNPs) was evaluated against P. aeruginosa isolates obtained from burn and wound samples.
Five concentrations of AgNPs (31.25, 62.5, 125, 250, and 500 µL/mL) were tested on five selected clinical isolates. The evaluation included the effect of AgNPs alone and in combination with certain selected antibiotics. The findings indicated that antibacterial activity increased significantly with higher AgNP concentrations, showing a strong dose-dependent inhibitory effect.
These findings confirm that silver nanoparticles possess strong inhibitory effects on the growth of Pseudomonas aeruginosa and can prevent biofilm formation, highlighting their potential as an alternative therapeutic option in the future.