In Vitro Effects of Centaurea ovina (Roudbari Cornflower) Aqueous and Ethanolic Extracts on Staphylococcus saprophyticus: Growth Inhibition, Antibiofilm Activity, and Reduced ureC/uafA Transcripts
Abstract
Objectives: Staphylococcus saprophyticus frequently causes community-acquired urinary tract infections (UTIs) and is characterized by multidrug resistance (MDR) and biofilm formation. This study evaluated the in vitro antibacterial and antibiofilm effects of aqueous and ethanolic extracts of Centaurea ovina (Roudbari cornflower) against clinical S. saprophyticus isolates and measured changes in ureC and uafA transcript levels after exposure to the extracts.
Methods: The aqueous and 80% ethanolic extracts of C. ovina were analyzed for total phenolics, flavonoids, flavonols, anthocyanins, and DPPH radical-scavenging activity. Antibacterial activity against three clinical isolates (SS1-SS3) was assessed using agar well diffusion and broth microdilution (MIC/MBC). Biofilm inhibition was measured by crystal violet staining. In the MDR isolate (SS2), ureC and uafA transcript levels were measured by SYBR Green qRT-PCR (2-ΔΔCt) after treatment with the ethanolic extract at a sub-MIC concentration (1/2MIC), with results normalized to 16S rRNA.
Results: The ethanolic extract contained more flavonoids and flavonols and exhibited stronger DPPH scavenging activity than the aqueous extract, which had more total phenolics. In broth microdilution, the ethanolic extract inhibited SS1-SS3 growth at 48 mg/mL (MIC), whereas the aqueous extract did not reach an MIC within the tested range (MIC > 48 mg/mL). No bactericidal effect was observed for the ethanolic extract (MBC > 48 mg/mL). Both…
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