While Sriramula et al. [16], grew their cultures under 20% EO2 with shaking, we grew our cultures under static conditions regardless of the EO2 concentration. Given these differences, it is not practical to directly compare the bacterial structures observed in the two studies with respect to the role of the QS systems in their formation. Biofilms at different infection sites often consist of multiple species of bacterial pathogens [52, 53]. These bacterial species may either compete with each other or support each other’s growth. Qin et al. [54] previously showed that P. aeruginosa inhibited the planktonic
https://www.selleckchem.com/products/BIRB-796-(Doramapimod).html growth of Staphylococcus epidermidis through a QS-related mechanism. Additionally, using the static chamber cultivation system (microtiter plate assay), they demonstrated that P. aeruginosa extracellular polysaccharide disrupted an already established S. epidermidis biofilm [54]. Disruption of these biofilms, however, does not occur through the bactericidal effect observed with the planktonic cells; instead the bacteria within the biofilm were dispersed alive [54]. When we co-cultured
P. aeruginosa and S. aureus statically under 20% EO2 in TSBDC or ASM+, P. aeruginosa eliminated S. aureus by day 2 (Figure 10). Furthermore, and similar to the findings by Qin et al. with S. epidermidis[54], the addition of P. aeruginosa to S. aureus BLS established in ASM+ disrupted the S. aureus BLS (11a, b). However, P. aeruginosa see more disrupted
the S. aureus BLS through an bactericidal effect rather than dispersion. By 56-h post addition of PAO1, no CFU of AH133 were recovered (Figure 11C), although it is remotely possible that our failure to detect S. aureus is due to their existence in a viable but nonculturable CFTR modulator state. This effect is similar to the clinical observations of CF lung infections where S. aureus, an early colonizer, is gradually replaced by P. aeruginosa. The MK-2206 chemical structure nature of the PAO1 bactericidal factor that eliminates the S. aureus BLS is under investigation. Conclusions In this study, we have demonstrated that thick, viscous ASM+ containing mucin and extracellular DNA and incubated under static conditions with lowered oxygen tension (10% EO2) – constituents and conditions similar to those within the lung alveoli of CF patients – induces the formation of biofilm-like structures by P. aeruginosa and S. aureus, two of the pathogens most commonly seen in the infected lungs of these patients. The BLS are not attached to the surface, but form within the medium as has been reported for the development of macrocolonies within the mucus in CF lungs. Thus, ASM+ represents an in vitro medium in which the effect of changing levels of substances produced by the host and the bacteria can be analyzed to determine the effect on such structures and on the susceptibility of the bacteria within the BLS to various treatments.