Department of Chemistry, Faculty of Science, University of Karachi, Karachi 75270, Pakistan.
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Hamdard University, Karachi 74600, Pakistan.
Molecules. 2022 Oct 13;27(20):6874. doi: 10.3390/molecules27206874.
(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.
（1）背景：金黄色葡萄球菌（S. aureus）是生物膜相关感染的最常见原因之一。随着抗生素耐药性的出现，特别是耐甲氧西林金黄色葡萄球菌（MRSA），迫切需要发现针对这种临床重要病原体的新型抑制化合物。在这项研究中，我们评估了 11 种化合物（包括苯丙烯和酚醛）、丁香酚、阿魏酸、芥子酸、水杨醛、香草醛、肉桂酸和醛类对耐药性金黄色葡萄球菌分离株的抗菌和抗生物膜活性。
（2）方法：从巴基斯坦卡拉奇的 Alkhidmat 诊断中心和血库获得 32 株临床金黄色葡萄球菌分离株，筛选其生物膜形成潜力，并使用 Kirby-Bauer 圆盘扩散法检测其对环丙沙星、氯霉素、氨苄西林、阿米卡星、头孢噻吩、克林霉素、链霉素和庆大霉素的敏感性/耐药性。随后，选择 5 株有代表性的临床分离株，使用定性和定量测定法检测 11 种化合物的抗菌和抗生物膜潜力，然后进行 qPCR 分析，以检查经（天然化合物及其衍生物）和未经处理的分离株处理后生物膜形成基因（ica-A、fnb-B、clf-A 和 cna）表达水平的差异。
（3）结果：所有分离株均被发现为多药耐药且主要为生物膜形成者。天然化合物及其类似物的个别最低抑菌浓度（MIC）范围为 0.75-160mg/mL。此外，化合物水杨醛（SALI）、香草醛（VAN）、α-甲基反式肉桂醛（A-MT）和反式-4-硝基肉桂酸（T4N）在 1-10mg/mL 浓度下表现出显著的（15-92%）生物膜抑制/减少百分比能力。基因表达分析表明，水杨醛、α-甲基反式肉桂醛和α-溴代反式肉桂醛与未经处理的耐药分离株相比，导致 ica-A、clf-A 和 fnb-A 基因的表达显著（p<0.05）下调。
（4）结论：本研究中使用的天然化合物及其类似物对金黄色葡萄球菌表现出显著的抗菌和抗生物膜活性。生物膜的持续存在是临床环境中的主要关注点。这些化合物可能成为针对生物膜形成的金黄色葡萄球菌的潜在候选药物分子。
