Methylene blue activity against clinically isolated Staphylococcus aureus and Pseudomonas aeruginosa from wounds compared to gentamicin and iodine

Document Type : Original Article


1 Department of Microbiology, Al-Shomali General Hospital, Babylon Health Directorate, Babylon, Iraq

2 Department of Medical Laboratory Technology, College of Medical Technology, The Islamic University, Najaf, Iraq


Background: The increasing resistance of many bacterial pathogens against antibiotic requires urgently new or repurposing therapeutic strategies. Methylene blue (MB) was first prepared in 1876. It was previously used for treating cyanide poisoning and urinary tract infections, but this use is no longer recommended. However, few studies have been conducted on the antimicrobial activity of MB. Methods: This cross- sectional study includes 30 bacterial samples isolated from wounds, 15 were Staphylococcus aureus and 15 were Pseudomonas aeruginosa from patients in Al- Shomali general hospital, Babylon, Iraq, from 2/9/2023 to 10/1/12024. Isolates examined by their Gram stain, morphology, culture, and biochemical tests. MB and iodine used as anti-microbial, they were used in well diffusion method while gentamicin investigated by disc diffusion method. For statistical analysis, SPSS software 26 (SPSS Inc., Chicago, USA) was used to represent data as the interquartile range (IQR). Result:  Methylene blue showed 63.4% activity to bacteria. Although activity of iodine on bacteria isolates that was strong activity 76.3%. Activity of gentamicin on isolates was strong activity 60.0%. The sensitivity of S. aureus to gentamicin was 18(12-20) mm while P. aeruginosa sensitivity to gentamicin was 15 (10-17) mm with no significant difference (P= 0.14). Activity of MB against S. aureus 22 (21-22) mm was higher than activity against P. aeruginosa 6 (0-22) mm significantly (p< 0.0001). There is negative correlation between gentamicin and iodine (r=-0.37, p= 0.03). Strong negative correlation observed between MB and iodine (r=-0.56, p=0.0001). Conclusion:  Methylene blue has antimicrobial activity against bacteria, so it may be used in the medical practices especially for topical treatment of wounds.


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