{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T20:57:17Z","timestamp":1790456237563,"version":"4.1.0"},"reference-count":55,"publisher":"Wiley","issue":"6","license":[{"start":{"date-parts":[[2023,1,19]],"date-time":"2023-01-19T00:00:00Z","timestamp":1674086400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Basic Microbiol"],"published-print":{"date-parts":[[2023,6]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The emergence of multidrug\u2010resistant (MDR) strains of<jats:italic>Klebsiella pneumoniae<\/jats:italic>is associated with high morbidity and mortality due to limited treatment options. This study attempts to biologically synthesize silver nanoparticles (AgNPs) and investigate their effect on expression levels of virulence and biofilm\u2010related genes in clinically isolated<jats:italic>K. pneumoniae<\/jats:italic>. In this study, biofilm formation ability, antibiotic resistance pattern, extended\u2010spectrum \u03b2\u2010lactamases (ESBLs), and carbapenemases production were investigated for 200 clinical isolates of<jats:italic>K. pneumoniae<\/jats:italic>using phenotypic methods. Polymerase chain reaction (PCR) was used to detect virulence and biofilm\u2010related genes, ESBL\u2010encoding genes, and carbapenem resistance genes. AgNPs were synthesized using the bio\u2010reduction method. The antibacterial effects of AgNPs were investigated by microdilution broth. In addition, the cytotoxic effect of AgNPs on L929 fibroblast cell lines was determined. The effects of AgNPs on<jats:italic>K. pneumoniae<\/jats:italic>virulence and biofilm\u2010related genes (<jats:italic>fimH, rmpA<\/jats:italic>, and<jats:italic>mrkA<\/jats:italic>) were determined using quantitative real\u2010time PCR. Thirty percent of the isolates produced a strong biofilm. The highest and lowest levels of resistance were observed against amoxicillin\/clavulanic acid (95.4%) and tigecycline (96%), respectively. About 31% of isolates were considered positive for carbapenemases, and 75% of the isolates produced an ESBLs enzyme. Different frequencies of mentioned genes were observed. The synthesized AgNPs had a spherical morphology and varied in size. AgNPs inhibited the growth of MDR<jats:italic>K. pneumoniae<\/jats:italic>at 128\u2009\u00b5g\/ml. In addition, AgNPs downregulated the expression of<jats:italic>fim<\/jats:italic>H,<jats:italic>rmp<\/jats:italic>A, and<jats:italic>mrk<\/jats:italic>A genes by 10, 7, and 14\u2010fold, respectively (<jats:italic>p<\/jats:italic>\u2009&lt;\u20090.05), also exerted no cytotoxic effect on L929 fibroblast cell lines. It was revealed that AgNPs lead to a decrease in expression levels of virulence and biofilm\u2010related genes; therefore, it was concluded that AgNPs had an excellent antibacterial effect on MDR<jats:italic>K. pneumoniae<\/jats:italic>.<\/jats:p>","DOI":"10.1002\/jobm.202200612","type":"journal-article","created":{"date-parts":[[2023,1,20]],"date-time":"2023-01-20T05:50:06Z","timestamp":1674193806000},"page":"632-645","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Evaluation of biosynthesized silver nanoparticles effects on expression levels of virulence and biofilm\u2010related genes of multidrug\u2010resistant<i>Klebsiella pneumoniae<\/i>isolates"],"prefix":"10.1002","volume":"63","author":[{"given":"Seyed M.","family":"Mousavi","sequence":"first","affiliation":[{"name":"Scool of Medicine Iran University of Medical Science Tehran Iran"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Seyed M. 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