| Summary: | The justification for the use of herbal supplements with <i>Pulmonaria officinalis</i> L. extract (POE) in the case of staphylococcal lung colonization/infections characteristic for cystic fibrosis (CF), was examined in vitro. The impact of POE phenolic-rich fraction on the virulence attributes of CF-associated <i>Staphylococcus aureus</i> (<i>S. aureus</i>) clinical strains has been assessed, including pathogen adhesion, biofilm formation on native and protein-conditioned surfaces (mucin, elastin), mature biofilm eradication, staphylococcal protein A expression, α-toxin release, and <i>S. a.</i> adhesion to A549 cells. Cytotoxicity of the extract to lung epithelial cells was also investigated. It was found that POE has bacteriostatic effects at MIC 1–2 mg/mL, recognized as of limited efficacy, but at MIC/subMICs it targeted virulence not viability. It usually decreased <i>S. aureus</i> adhesion and less frequently inhibited biofilm formation on native and protein-conditioned surfaces. Observed effect seems to be related to significant reduction by POE of sortase A activity. However, in some cases POE favored the creation of biofilm by staphylococci and <i>S. aureus</i> adhesion to the lung epithelium was not limited. On the other side POE caused significant decrease of <i>S. a.</i> α-toxin synthesis and slightly weakened the expression of SpA. When used at supraMICs POE eradicated mature biofilm, but in some cases with unsatisfying outcomes. Promisingly, POE has been recognized as a safe product, with no cytotoxicity up to 4 mg/mL. These results reflect the positive, negative or neutral anti-staphylococcal properties of POE. It seems that POE may be beneficial as a prophylactic, but not as a therapeutic or supportive agent in the area of CF—integrative medicine. However, introduction the official recommendations needs further in vivo studies.
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