Prevalence, Biofilm-Forming Capacity and Expression of Matrix-Associated Genes in Clinical Pseudomonas Aeruginosa Isolates from Babylon, Iraq

Abstract

Objective: To identify the number of Pseudomonas aeruginosa from different clinical specimens and quantify biofilm production and to compare gene expression of pslA, pelA and fliC among biofilm and non-biofilm phenotypes by using reverse transcription-quantitative polymerase chain reaction.

Study Design: Prospective cross-sectional study
Place and Duration of Study: This study was conducted at the Department of Life Sciences, College of Science, University of Babylon, Iraq from 1st November 2025 to 30th April 2026.

Methods: Fifty samples from laboratory confirmed Pseudomonas aeruginosa were collected from 50 patients; 87 isolates were also cultured on Cetrimide agar and confirmed as Pseudomonas aeruginosa via standard polymerase chain reaction utilizing the azu gene (476 bp). Biofilm development was determined based on OD590 readings from stained crystal violet biofilms formed following 24 hr of static culture in 96 well plates. Gene expression was measured via reverse transcription-quantitative polymerase chain reaction on an Mx3005P with SYBR Green
utilizing rpoD as a normalizing reference gene and the 2-ΔΔC T method for data analysis.

Results: Seventy six (87.4%) were confirmed as Pseudomonas aeruginosa; wound sample comprised 30% of total samples; overall confirmatory increase across each type ranged from 81.8% (urine) to 100% (blood). Biofilms were created by 80.3% of confirmed isolates; of these, strongly biofilm-producing (vs weak) isolates constituted the majority (42.1%). Gene expression of pslA (13.5-62.5-fold; F=121,038; P<0.0001) and pelA (1,116-5,181-fold; F=903,770,772; P<0.0001) were significantly downregulated in all biofilm-producing phenotypes relative to non- biofilm-producing phenotypes; fliC was significantly upregulated (4.2-19.6-fold; F=497.9; P<0.0001).

Conclusion: P.aeruginosa clinical specimens from Babylon are highly capable of biofilm formation; however, the unexpected expression profile of biofilm producing specimens suggests that there is a significant dissociation between phenotypic expression of biofilm components and the mechanism of biofilm persistence.