title: Mutation of environmental mycobacteria to resist silver nanoparticles also confers resistance to a common antibiotic.
abstract: Non-tuberculous mycobacteria are a threat to human health, gaining entry to the body through contaminated water systems, where they form persistent biofilms despite extensive attempts at disinfection. Silver is a natural antibacterial agent and in nanoparticle form activity is increased by a high surface area. Silver nanoparticles (AgNPs) have been used as alternative disinfectants in circulating water systems, washing machines and even clothing. However, nanoparticles, like any other antibiotic that has a pervasive durable presence, carry the risk of creating a resistant population. In this study Mycobacterium smegmatis strain mc(2)155 was cultured in AgNP enriched agar such that only a small population survived. Surviving cultures were isolated and re-exposed to AgNPs and AgNO3 and resistance to silver was compared to a negative control. After only a single exposure, mutant M. smegmatis populations were resistant to AgNPs and AgNO3. Further, the silver resistant mutants were exposed to antibiotics to determine if general resistance had been conferred. The minimum inhibitory concentration of isoniazid was four times higher for silver resistant mutants than for strain mc(2)155. However, core resistance was not conferred to other toxic metal ions. The mutants had lower resistance to CuSO4 and ZnSO4 than the mc(2)155 strain.
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 636 Benedum Hall, 3700 O'Hara St., Pittsburgh, PA, 15261, USA.
authors.forename: Curtis
authors.initials: C
authors.lastname: Larimer
authors.forename: Mohammad Shyful
authors.initials: MS
authors.lastname: Islam
authors.forename: Anil
authors.initials: A
authors.lastname: Ojha
authors.forename: Ian
authors.initials: I
authors.lastname: Nettleship
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D019327:Copper Sulfate / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004783:Environmental Microbiology; D007538:Isoniazid / Q000494:pharmacology; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000235:genetics*; D012834:Silver / Q000494:pharmacology*; D019287:Zinc Sulfate / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D019287:Zinc Sulfate; D019327:Copper Sulfate; D007538:Isoniazid