Background: In recent years, high attention has been given to the biological activities of natural compounds and their potential antimicrobial properties. Objective: In this study, the antibacterial properties of the extracts from tissue and peptides of Cerastoderma and Didacna were studied. Materials and Methods: samples of Cerastoderma and Didacna were collected and washed. Then, the soft tissues were cut and powdered, and concentrations of 16, 8, 4, 2, 1 and 0.5 of chloroform, ethanol and methanol, and in addition extract of enzymatic hydrolysis were prepared, and their antibacterial activities against Staphylococcus aureus, Escherichia coli and Salmonella paratyphi were investigated. The disc diffusion method was used for the evaluation of strains susceptibility. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were investigated for bacterial growth inhibition. Results: Methanolic and ethanolic extracts from Cerastoderma demonstrated higher growth inhibitory effects compared to those from Didacna on E. coli and S. paratyphi and exhibited similar activities against S. aureus at concentrations 16 and 8 ug/mL. In addition, chloroform extracts of Cerastoderma and Didacna displayed similar inhibitory effects on S. paratyphi and S. aureus at concentrations 16 and 8 ug/mL which was a suitable effect, and the extract from Cerastoderma was more effective. MIC and MBC of methanolic extracts were at the lowest level, especially against S. aureus. Conclusion: It was revealed that Cerastoderma and Didacna extracts were effective as antibacterial compounds on S. aureus, E. coli and S. paratyphi species as natural agents.
Objective: As major nosocomial pathogens, Escherichia coli isolates exhibit antibiotic resistance and also express adhesive structures and antibiotic resistance genes. The objective of this study was the comparison of virulence gene expression of extendedspectrum beta-lactamase (ESBL)-producing E. coli between blood and stool samples.Methods: In this study, 20 E. coli clinical isolates (10 ESBL-producers including 5 from blood, 5 from stool samples and 10 non-ESBL-producer strains) were included. The existence of fimA, kpsMII and cdt (adhesives and toxin), acr-ab (efflux-encoding) and bla CTX-M1 genes were confirmed by PCR. The quantitative real-time PCR was performed for evaluation of gene expression.Results: ESBL-producing E. coli isolates from stool samples could express fimA, kpsMII and cdt genes significantly higher than blood samples, whereas those isolates from blood samples significantly expressed the acr-ab (efflux-encoding) genes. In addition, the bla CTXM1 gene was expressed among isolates from stool samples significantly higher (P ¼ 0.022) than those from blood samples according to the analysis of variance (ANOVA) test. In addition, among non-ESBL-producers, the expression of fimA, kpsMII and cdt genes was significantly lower than ESBL-producing isolates from blood samples, but not significantly different than those from stool samples. Moreover, the expression of acr-ab genes was significantly lower than those from stool samples. Conclusion:The results exhibited that the expression of virulence genes among clinical isolates of E. coli is not the same or similar in various conditions or from various clinical origins. Thus determining the profile of gene expression in each of clinical situations can be helpful in tracking the infectious pathogens. ESBL-producing strains possibly have regulatory factors for inducing higher virulence gene expression.
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