Figure 3.

Bacterial colonization can lead to acute infections, which in healthy individuals are usually cleared by the immune response and in some cases with the aid of antibiotics. In immunocompromised patients, the infection can progress into a chronic state characterized by a continuous inflammatory response with collateral tissue damage, hypoxic conditions, and low bacterial growth rates, resulting in low antibiotic susceptibility. Alternative antipathogenic strategies include the use of QS inhibitors or quorum quenching enzymes to decrease bacterial expression of virulence factors and biofilm formation. The QS system has been shown be lost or inactive in late infection stages so the efficacy of using QS inhibitors is most likely restricted to a certain time window. The low growth rates and high antibiotic susceptibility of bacteria in chronic infections can be reversed by treating with supplemental O₂ by breathing pure oxygen in either normo or hyperbaric conditions. The associated higher tissue concentrations of O₂ will lead to increased bacterial growth rates and higher susceptibility toward antibiotics targeting metabolically active bacteria. Alternatively, inhalation of NO can lead to upregulation of phosphodiesterases that break down the biofilm promoting molecule cyclic-di-GMP resulting in disaggregation.