Influence of biosynthesized silver nanoparticles on keratinase activity and mycelial growth of dermatophytes

Objective Among different nanomaterials, silver nanoparticles (SNPs) exhibited high antifungal potency compared with other types of nanoparticles (NPs), and this property is often very helpful, particularly against fungi resistant to conventional antifungal agents. However, synthesis of SNPs can generate toxic waste during the preparation process. Accordingly, new technique using non-toxic routes have been researched for the synthesis of SNPs using cell-free filtrate of Aspergillus niger and evaluate their effect against some dermatophytes spp. Methods The proposal of our study was to biosynthesize SNPs using cell-free filtrate of Aspergillus niger as reducing agent. The characterization of biosynthesized SNPs was carried out by UV-Visible spectroscopy, Fourier transform infrared spectroscopic analysis (FTIR) and scanning electron microscopy (SEM). The antifungal effect of the NPs against dermatophytes was also evaluated. The minimum inhibitory concentration (MIC) was determined by broth microdilution method. Results Spherical NPs 15–50 nm in size were obtained. The biosynthesized SNPs exerted pronounced morphological alteration in the fungal mycelia. Additionally, the inhibition of keratinase activity of the tested dermatophytes was also recorded. Conclusion The results indicate that SNPs can be synthesized in ecofriendly, inexpensive and promising technique by fungal strain of A. niger, and it has considerable antifungal activity in comparison with other antifungal drugs

Association between Biofilm Formation and Susceptibility to Antibiotics in Staphylococcus Lentus Isolated from Urinary Catheterized Patients

Staphylococcus lentus (S. lentus) is a coagulase negative gram positive cocci recognized as opportunistic pathogens and rarely forming biofilm; it has many virulence factors, but recently caused nosocomial and community infections. Biofilm formation of Staphylococcus lentus may be associated with the ability to resist antibiotics which leads to increase in mortality rate due to the difficulty in eradicate infections. To evaluate the biofilm forming capacity of Staphylococcus lentus and its susceptibility to antibiotics, phenotypic and genotypic assays were used. Among 28 biofilm bacteria, Staphylococcus lentus was isolated and identified from urine catheterized patients who were hospitalized in different departments of four Iraqi hospitals (Al-Diwaniyah Teaching, Al-Hilla Teaching, Al Qassim and Al Hashimiyah Hospitals). Staphylococcus lentus was examined for detection of biofilm formation by detecting icaA gene, the intercellular adhesion gene which expressed adhesion factor to form biofilm in staphylococci by using polymerase chain reaction (PCR) method and tested for antimicrobial susceptibility by disc diffusion method and VITEK2 system according to guidelines of the Clinical & Laboratory Standards Institute (CLSI).Three isolates of Staphylococcus lentus revealed the ability to form biofilm phenotypically which contained icaA gene with 100% antibiotics resistance to penicillin, carbenicillin, gentamicin, tobramycin, oxacillin, vancomycin, clindamycin, ciprofloxacin, and 0% antibiotics resistance to azithromycin. icaA genes are present in Staphylococcus lentus and responsible for biofilm formation which is considered as the indicator; biofilm formation is a strong cause of multidrug resistance in bacteria

Boosting Antimicrobial Activity of Imipenem in Combination with Silver Nanoparticles towards S. fonticola and Pantoea sp.

Silver nanoparticles have been considered as powerful antimicrobial agents recently, especially with the increasing incidence of diseases associated with biofilm and multi-drug resistant pathogens. The aim of this study was to synthesize silver nanoparticles by biological and chemical methods and combination with imipenem to eradicate biofilm-forming bacteria at phenotypic and genotypic levels. The biosynthesis of silver nanoparticles was done by using Enterobacter cloacae (cell-free suspension) while chemosynthesis was conducted using sodium borohydride. Biological and chemical silver nanoparticles were characterized by ultraviolet-visible spectrophotometry which showed absorbance peak at 400 and 390nm respectively. Fourier transformer infrared analysis revealed that carboxylic and polyphenolic groups were coated on surface of both silver nanoparticles. Scanning electron microscope and size analyser showed that the sizes of biologically and chemically silver nanoparticles were 63 nm and 25 nm, respectively. In addition, it showed the formation of cubical nanoparticles. The antimicrobial effect of synthesized silver nanoparticles were evaluated by agar well diffusion and macrodilution method to determine minimum inhibitory concentration value. The results showed that biological silver nanoparticles were more effective on biofilm forming bacteria (Serratia fonticola and Pantoea sp.) than chemical synthesized ones. In addition, the combination effect between silver nanoparticles and imipenem displayed synergistic effect. Gene expression of biofilm encoding genes (smaI and esaL) were evaluated by real- time quantitative polymerase chain reaction (RT- qPCR) before and after treatment with silver nanoparticles in both types and imipenem and in combination between them. The results revealed that biological silver nanoparticles alone or in combination with antibiotics were more effective on biofilm gene expression by down regulation than other treatments