To Biofilm or Not to Biofilm?

Aim: The goal of this research is to examine the biofilm forming ability of Staphylococcus aureus and Pseudomonas aeruginosa clinical isolates in different in vitro conditions using Meuller-Hinton and Luria-Bertani broths. Material and methods: 30 strains of Pseudomonas aeruginosa and 30 strains of Staphylococcus aureus obtained from clinical specimens were used. After preparing the suspensions of bacteria inoculated on broths, they were set on microtiter plates and the biofilm production was measured using the spectrophotometric reader on 550 nm. Strains were classified into four categories: non producing, weak producers, moderate and strong producers, based on the comparison of the optical density of samples and negative control. Results: Both of the tested strains, successfully formed a biofilm in both broths (p<0.01). P. aeruginosa strains in both in vitro conditions had a higher percentage of strong producers, in comparison with S. aureus strains (3.3% vs 50%). Nevertheless, there is no statistically significant difference in the biofilm formation between the strains, regardless the used broths and there is no statistically significant difference between the biofilm forming ability of both species observed separately regarding in vitro conditions as well. Conclusion: Both species have an ability to produce biofilm, which likely contributes the pathogenicity and virulence of these bacteria and leads to better understanding their in vivo characteristics to cause infections related to biofilm, as well.