An Easy New Modified Method for Detection of Antibacterial Susceptibility in Biofilm-Growing Bacteria

Biofilms are a major challenge in treating infections. Clinically, biofilms are often associated with chronic infections, so rapid and accurate methods of investigating the antibiotic susceptibility of biofilm bacteria are very important for faster diagnosis and treatment. In this study, a new modified microplate method was proposed to evaluate the antibiotic susceptibility of alive bacteria in the biofilm.

The study was conducted on clinical isolates of Pseudomonas aeruginosa and standard strain over a period of one year. The susceptibility test was conducted according to a modified version of the Calgary biofilm device method. In the last step, to study the living bacteria in the biofilm, oxidative-fermentative (OF) medium was used to measure the acid production following the use of glucose by the bacteria. The biofilm-growing bacteria was determined by observing the color changing and also measuring optical density (OD) at 427 nm of OF medium.

The method in this study could evaluate the effect of antibiotics on biofilm bacteria based on glucose metabolism. The results indicated that this method can quickly and easily identify alive bacteria in biofilm at a low cost and without the need for any special devices.

Although biofilms are involved in most incurable clinical cases, there is currently no guideline to assist physicians in treating biofilm-related infections. Therefore, it is necessary to establish a specific sensitivity test for biofilm or to approve a new method for routine use in diagnostic laboratories.