Analysis of the Antimicrobial and Anti-Biofilm Activity of Natural Compounds and Their Analogues against Staphylococcus aureus Isolates

Abstract

(1) Background: Staphylococcus aureus (S. aureus) is one of the most frequent causes of biofilm-associated infections. With the emergence of antibiotic-resistant, especially methicillin-resistant S. aureus (MRSA), there is an urgent need to discover novel inhibitory compounds against this clinically important pathogen. In this study, we evaluated the antimicrobial and anti-biofilm activity of 11 compounds, including phenyl propenes and phenolic aldehydes, eugenol, ferulic acid, sinapic acid, salicylaldehyde, vanillin, cinnamoyl acid, and aldehydes, against drug-resistant S. aureus isolates. (2) Methods: Thirty-two clinical S. aureus isolates were obtained from Alkhidmat Diagnostic Center and Blood Bank, Karachi, Pakistan, and screened for biofilm-forming potential, and susceptibility/resistance against ciprofloxacin, chloramphenicol, ampicillin, amikacin, cephalothin, clindamycin, streptomycin, and gentamicin using the Kirby-Bauer disk diffusion method. Subsequently, 5 representative clinical isolates were selected and used to test the antimicrobial and anti-biofilm potential of 11 compounds using both qualitative and quantitative assays, followed by qPCR analysis to examine the differences in the expression levels of biofilm-forming genes (ica-A, fnb-B, clf-A and cna) in treated (with natural compounds and their derivatives) and untreated isolates. (3) Results: All isolates were found to be multi-drug resistant and dominant biofilm formers. The individual Minimum Inhibitory Concentration (MIC) of natural compounds and their analogues ranged from 0.75–160 mg/mL. Furthermore, the compounds, Salicylaldehyde (SALI), Vanillin (VAN), α-methyl-trans-cinnamaldehyde (A-MT), and trans-4-nitrocinnamic acid (T4N) exhibited significant (15–92%) biofilm inhibition/reduction percentage capacity at the concentration of 1–10 mg/mL. Gene expression analysis showed that salicylaldehyde, α-methyl-trans-cinnamaldehyde, and α-bromo-trans-cinnamaldehyde resulted in a significant (p < 0.05) downregulation of the expression of ica-A, clf-A, and fnb-A genes compared to the untreated resistant isolate. (4) Conclusions: The natural compounds and their analogues used in this study exhibited significant antimicrobial and anti-biofilm activity against S. aureus. Biofilms persist as the main concern in clinical settings. These compounds may serve as potential candidate drug molecules against biofilm forming S. aureus.

Antibacterial and Antibiofilm Effects of Allelopathic Compounds Identified in Medicago sativa L. Seedling Exudate against Escherichia coli

“…The susceptibility of E. coli isolates to the total extract and its isolated compounds was revealed by the agar well-diffusion method [ 78 ]. Briefly, after spreading the bacterial suspensions on the Muller–Hinton agar plates, cups were made, and the tested compounds, in dimethyl sulfoxide (DMSO) with concentrations of 1000 µg/mL, were poured into the cups.…”

Potential Surviving Effect of Cleome droserifolia Extract against Systemic Staphylococcus aureus Infection: Investigation of the Chemical Content of the Plant

“…The relative gene expression of the treated isolates was compared to that of the untreated ones according to the 2 −∆∆Ct method [76]. Primers are exposed in Table S1 [77,78].…”

Antimicrobial and biocide resistance in Staphylococcus aureus: genomic features, decontamination strategies, and the role of S. aureus complex-related species, with a focus on ready-to-eat food and food-contact surfaces

“…Recent studies have indicated that various natural compounds not only inhibit biofilm formation but also eradicate mature biofilm produced by several bacterial species, including S. aureus (Mastoor et al, 2022). Essential oils are mixtures of secondary metabolites obtained from plants, which can exert an antimicrobial activity directly when used in food products and in active food packaging, or indirectly when used as sanitizing or antibiofilm agents on food-and other contact surfaces (Pedonese et al, 2017).…”