Estimation of the effect Citrullus colocynthis extract on SPM and VIM genes in Pseudomonas aeruginosa isolated from cancer patients

Background and Objectives: Pseudomonas aeruginosa is a major threat to immunocompromised cancer patients due to multidrug resistance (MDR) and virulence. Metallo-β-lactamase (MBL) genes such as SPM and VIM further limit treatment options. This study evaluated the activity of Citrullus colocynthis (C. colocynthis) extract against MDR P. aeruginosa isolates, focusing on suppression of SPM and VIM expression. Methods: A cross-sectional study was conducted on 150 clinical specimens (blood, sputum, urine, pus) from cancer patients at Baghdad Teaching Hospital. P. aeruginosa isolates were identified by Gram staining, biochemical tests, and the VITEK 2 system. Antimicrobial susceptibility was determined using AST-GN72 cards. Minimum inhibitory concentration (MIC) of C. colocynthis extract was assessed by resazurin microdilution assay. RT-qPCR was performed on RNA extracted from isolates incubated with sub-MIC concentrations (0.35 mg/mL) to evaluate transcriptional changes in SPM and VIM genes. Results: Out of 150 samples, 30 (20%) yielded P. aeruginosa; 20 (66.6%) were MDR, most frequently from acute leukemia (30%) and breast cancer (23.3%) patients. MIC testing showed that 0.7 mg/mL C. colocynthis extract inhibited 100% of MDR isolates. RT-qPCR demonstrated significant downregulation of SPM (1.191 ± 0.615 vs. 0.202 ± 0.573; p = 0.01) and VIM (1.074 ± 0.405 vs. 0.170 ± 0.406; p = 0.01), indicating both direct antimicrobial activity and resistance gene suppression. Conclusions: C. colocynthis extract exhibited potent inhibitory effects against MDR P. aeruginosa, mediated by antimicrobial action and reduced MBL gene expression. These findings suggest its potential as an adjunct to conventional therapies.