Effect of probiotics on some virulencefactors of Pseudomonas aeruginosa isolated from clinical samples

 This study aimed to detect the inhibitory effect of some probiotics against pyocyanin and lipases activity produced by Pseudomonas aeruginosa, and comparing this effect with that of the commonly used
antibiotics. From a total of 209 bacterial isolates collected from different clinical sources (Urine, ear, sputum, congenital disorder fluids, pus, and wounds) of two hospitals in Baghdad, 16 of them were identified as P. aeruginosa.When the sixteen isolates were examined for pyocyanin and lipases production on glycerol supplemented nutrient agar and tween 80 agar, respectively, all isolates, except one, were positive for pigment and enzymes production.Four probiotic microorganisms namely (Lactobacillus acidophilus, Lb. fermentum, Lb. plantarum and Saccharomyces boulardii) were propagated in their media. After incubation, their fermented aliquots were centrifuged and filtered which were considered as unconcentrated filtrates. From these filtrates, one, two and three-fold concentrated filtrates were prepared. Antibiotic solutions of Amikacin, Ceftazidime,Imipenem and Tobramycin were also prepared at a concentration of 10μg/ml for comparison. Pyocyanin of the two highly producing P. aeruginosa isolates was extracted after 72h incubation at 28°C in glycerol supplemented nutrient broth, and then was allowed to contact the probiotic filtrates and antibiotic solutions for 15min. The optical density of pyocyanin activity was estimated at a wave length of 520 nm. Similarly, lipases activity of the two highly producing isolates was estimated by lipases turbidimetric assay after 48h incubation at 35°C in the lipolytic medium, and then was allowed to contact the probiotics and antibiotics for 30min.The optical density of lipases activity was estimated at a wave length of 500 nm. Results revealed that the three-fold concentrated filtrate of Lb. acidophilus was able to inhibit pyocyanin activity very strongly (1.06μg/ml) and lipases moderately (127.3U/L), followed by those filtrates of Lb. fermentum and Lb. plantarum which were less strongly in their inhibition. On the other hand, the three-fold filtrate of S. boulardii was weakly effective in this regard (20.3μg/ml and 261.1U/L,respectively). Regarding the antibiotics used in this study, Ceftazidime was the most effective one (4.69μg/ml and 169U/L respectily), followed by Imipenem and Tobramycin with moderate effect, then Amikacin with the least effect, while neither Imipenem nor Tobramycin were unable to show any effect on lipases produced by P. aeruginosa. From the results, it can concluded that among all probiotics and antibiotics used in this study, the three-fold concentrated filtrate of Lb. acidophilus was the superior in its ability to inhibit the Pseudomonas aeruginosa virulence factors included in this study (pyocyanin pigment and lipase enzymes), while the antibiotic Ceftazidime was the most effective compared to the other antibiotics used.