The usefulness of Gram staining method for analysis of the effectiveness of decontamination of firefighter’s protective outfit

The Main School of Fire, Faculty of Fire Safety Engineering, 52/54 Slowackiego St., 01-629 Warsaw, Poland

^* Corresponding author: apolanczyk@sgsp.edu.pl

Abstract

Introduction: This study was undertaken to analyze the effectiveness of different decontamination techniques of firefighters’ outfit. Methods and findings: Firefighter’s outfit used for one month in field conditions was tested for biological contamination using Gram staining. Biological samples from pantleg above the ankle, on the knee and, in the groin were analyzed. Swabbed places were cut out and sterilized mechanically using tap water, 20% soap or 70% ethanol by rubbing for 20. Swabs were taken before sterilization and right after sterilization. Each time smears were made on sterile glass, fixed in pure ethanol and stained using Gram method. This staining method is used to visualize bacteria and distinguish gram-positive and gram-negative bacteria. After staining samples were air dried and photographed under a light microscope at magnification 100x. Each smear was made in triplicates and the relative number of biological contamination was analysed using ImageJ software. The results indicated that the highest level of contamination was visible on the knee. Decontamination decreased the number of bacteria in all analyzed places right after cloth patch washing. The most effective decontamination fluid was 70% ethanol followed by 20% soap. The Gram staining combined with numerical analysis may be successfully used to verify the effectiveness of decontamination method for firefighter’s outfit utilized at field.