The Antibacterial Action of Safranin and Gentian Violet

The increasing resistance of many bacterial pathogens against antibiotic measures urgently requires new or repurposing therapeutic strategies. Gentian violet is a triarylmethane dye used as a histological stain and for Gram's method of classifying bacteria. It also exerts an antimicrobial effect against certain pathogens, especially dermatological infections. Safranin is the most popular counterstain used in medical laboratories due to its low cost and safe laboratory usage. However, few studies have been conducted on the antimicrobial activity of safranin.

With the growing prevalence of multidrug-resistant bacteria, this study aimed to evaluate the antibacterial efficacy of gentian violet and safranin against multidrug-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa).

All tested bacteria were multidrug-resistant (MDR) bacteria isolated from skin infections (abscesses and wounds). Using gentian violet and safranin, antibacterial effects were studied using the well-diffusion method against 20 samples of clinically isolated bacteria, 10 diagnosed as S. aureus, and 10 as P. aeruginosa. Bacteria were diagnosed using the VITEK 2 automated system (bioMérieux, Marcy-l'Étoile, France). Iodine served as the control agent, since both Gram-positive and Gram-negative bacteria are sensitive to it.

Gentian violet dye has been shown to be 100% sensitive to both Gram-positive and Gram-negative bacterial isolates. Although safranin also had high sensitivity (100%) to S. aureus isolates, its sensitivity to P. aeruginosa was only 20%. Staphylococcus aureus was more resistant to iodine (40% sensitivity) compared to P. aeruginosa, which was 100% sensitive to iodine.

Gentian violet and safranin are low-cost and better tolerated topical agents that have potential for use in dermatological applications. Gentian violet had good antibacterial activity against both Gram-positive and Gram-negative bacteria, making it useful for treating bacterial skin pathogens such as S. aureus and P. aeruginosa especially for MDR bacteria. While safranin has good efficacy against Gram-positive bacteria (S. aureus), its effect against Gram-negative bacteria (e.g. P. aeruginosa) is poor.