The effect of hyperbaric oxygenation on the in vitro growth of Escherichia coli in environments with and without blood cells

Abstract

The aim of this study was to investigate whether the in vitro presence of blood cells influences the anti-microbial activity of hyperbaric oxygen (HBO) against Escherichia coli. Fifty E. coli isolates from clinical samples were used in the study. A small number of colonies belonging to each isolate from the nutrient media were transferred into two K3EDTA tubes (the blood group) and two Mueller-Hinton broth tubes (the broth group). Then, both groups were divided into subgroups according to whether HBO was administered (HBO subgroup) or not (non-HBO subgroup). HBO treatment was applied for one hour at 2.5 absolute atmospheres. The tubes in the non-HBO subgroup were left at room temperature during this period. Subsequently, all the tubes were cultured on Mueller-Hinton and Eosin Methylene Blue agar using the quantitative counting technique. After 18 to 24 h incubation at 37 °C, the colonies formed in the plates were counted. In the blood group, compared with non-HBO subgroup samples, the number of colonies decreased in 56% of samples, increased in 32% of samples and did not change in 12% of samples in the HBO subgroup. Whereas, in the broth group the number of colonies decreased in only 32% of samples increased in 38% of samples and did not change in 30% of samples in the HBO subgroup compared with the non-HBO subgroup. The difference between the blood and the broth groups revealed a statistical significance using Pearson's Chi-square test (P = 0.025). We concluded that the antibacterial effect of HBO on E. coli increases in the cellular environment belonging to the host organism.