Phenotypic and Molecular Characterization of Plasmid-Mediated Virulence and Antimicrobial Resistance Traits among Multidrug Resistant Enterococcus spp. in Egypt

Chemical Profile, Antibacterial, Antibiofilm, and Antiviral Activities of Pulicaria crispa Most Potent Fraction: An In Vitro and In Silico Study

Infectious diseases caused by viruses and bacteria are a major public health concern worldwide, with the emergence of antibiotic resistance, biofilm-forming bacteria, viral epidemics, and the lack of effective antibacterial and antiviral agents exacerbating the problem. In an effort to search for new antimicrobial agents, this study aimed to screen antibacterial and antiviral activity of the total methanol extract and its various fractions of Pulicaria crispa (P. crispa) aerial parts. The P. crispa hexane fraction (HF) was found to have the strongest antibacterial effect against both Gram-positive and Gram-negative bacteria, including biofilm producers. The HF fraction reduced the expression levels of penicillin binding protein (PBP2A) and DNA gyrase B enzymes in Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Additionally, the HF fraction displayed the most potent antiviral activity, especially against influenza A virus, affecting different stages of the virus lifecycle. Gas chromatography/mass spectrometry (GC/MS) analysis of the HF fraction identified 27 compounds, mainly belonging to the sterol class, with β-sitosterol, phytol, stigmasterol, and lupeol as the most abundant compounds. The in silico study revealed that these compounds were active against influenza A nucleoprotein and polymerase, PBP2A, and DNA gyrase B. Overall, this study provides valuable insights into the chemical composition and mechanism of action of the P. crispa HF fraction, which may lead to the development of more effective treatments for bacterial and viral infections.

Development of fluorinated nicotinonitriles and fused candidates as antimicrobial, antibiofilm, and enzyme inhibitors

The antimicrobial assessments of two new series of nicotinonitriles and pyrido[2,3-d]pyrimidines were performed using amoxicillin and nystatin as reference standards. Outstanding antifungal activities were achieved by some target compounds; for instance, compounds 7 and 9 displayed a minimal inhibitory concentration (MIC) value of 1.95 µg/ml toward Candida albicans, compound 11 showed a potent anti-Rhizopus effect (MIC 1.95 µg/ml) and compound 14 elicited remarkable antifungal effects against both Aspergillis niger and C. albicans (MIC 1.95 µg/ml). However, pyrido[2,3-d]pyrimidines 12, 14, and 16 showed moderate antibacterial activities against some gram-negative bacteria. The antibiofilm results of these compounds against resistant strains of Proteus mirabilis were better than those of Pseudomonas aeruginosa. Docking studies of these hits at the DNA gyrase active site revealed affinity and docking scores comparable to that of the reference standards. Gyrase-inhibitory activities revealed that 14 (IC₅₀  = 0.31 µM) is the most potent hit as DNA gyrase A inhibitor; it exhibited 1.66-fold the activity of ciprofloxacin (IC₅₀  = 0.50 µM) and it was a 44.3 times more potent gyrase B inhibitor (IC₅₀  = 0.04 µM) than novobiocin (IC₅₀  = 1.77 µM). Regarding its antifungal activity, it displayed 0.78% of the fluconazole activity as a 14α-demethylase inhibitor. The cytotoxicity of 12, 14, and 16 on human diploid lung fibroblasts (WI38 cells) ensured their safety. Moreover, they are orally bioavailable with no permeation of the blood-brain barrier.

Phenotype-Genotype Correlations and Distribution of Key Virulence Factors in Enterococcus faecalis Isolated from Patients with Urinary Tract Infections

Background and Objective

Enterococcus faecalis can cause different nosocomial infections, especially urinary tract infection (UTI). Pathogenicity of E. faecalis is driven by various virulence factors; however, no specific genetic pattern is restricted to a particular type of infection. The current study aimed to investigate the correlation between different virulence factors in E. faecalis clinical isolates causing UTIs.

Methods

We phenotypically analyzed 60 urinary isolates, identified as E. faecalis, for biofilm formation, gelatinase, protease and hemolytic activities by Crystal Violet assay, gelatin hydrolysis, casein hydrolysis and blood agar hemolysis assays, respectively. Additionally, we detected different genes associated with species identification, virulence phenotypes, adherence and quorum sensing by the polymerase chain reaction (PCR). The detected genes included D-alanine-D-alanine ligase (ddl), cytolysin (cyl), gelatinase (gelE), serine protease (sprE), faecal streptococci regulator locus genes (fsrA, fsrB, fsrC), pili (pil), adhesin to collagen of E. faecalis (ace) and aggregation substance (agg).

Results

All isolates formed biofilms, mostly with strong to moderate ability. Although gelE was detected in 87% of the isolates, only 22% of the isolates had gelatinase activity. Similar phenotype-genotype incongruities were observed with hemolysis and casein hydrolysis activities, as the isolates that expressed these two phenotypes were fewer than those carrying the genes encoding them.

Conclusion

A clear variability in virulence gene distribution among the isolates was observed, and no particular pattern was associated with UTI. Whereas all isolates carried at least ace and pil, whose products are involved in adherence, which is a virulence phenotype that is required for urinary colonization, six isolates carried the entire set of investigated genes. Statistical analysis of the results suggests cyl as a biomarker for hemolytic activity, fsrB as a diagnostic biomarker for the gelatinase activity, and gelE-sprE as predictors for biofilm formation strength in E. faecalis.