Biocidal properties of metal oxide nanoparticles and their halogen adducts.

Nanosized metal oxide halogen adducts possess high surface reactivities due to their unique surface morphologies. These adducts have been used as reactive materials against vegetative cells, such as Escherichia coli as well as bacterial endospores, including Bacillus subtilis and Bacillus anthracis (Delta Sterne strain). Here we report high biocidal activities against gram-positive bacteria, gram-negative bacteria, and endospores. The procedure consists of a membrane method. Transmission electron micrographs are used to compare nanoparticle-treated and untreated cells and spores. It is proposed that the abrasive character of the particles, the oxidative power of the halogens/interhalogens, and the electrostatic attraction between the metal oxides and the biological material are responsible for high biocidal activities. While some activity was demonstrated, bacterial endospores were more resistant to nanoparticle treatment than the vegetative bacteria.

A multifunctional biocide/sporocide and photocatalyst based on titanium dioxide (TiO2) codoped with silver, carbon, and sulfur.

Composite nanostructured samples of Ag (0.5-20%)/(C, S)-TiO(2) were synthesized and characterized by EDX, XRD, FT-IR, UV-vis, BET, XPS, and zeta potential measurements. Photocatalytic and biocidal tests revealed that the amount of the codoped silver (Ag(+)) in (C, S)-TiO(2) played a crucial, distinctive role in the photodegradation of gas-phase acetaldehyde as well as in the inactivation of Escherichia coli cells and Bacillus subtilis spores. Very interestingly, Ag/(C, S)-TiO(2) nanoparticles (crystallite size <10 nm) have shown very strong antimicrobial properties without light activation against both E. coli (log kill >8) and B. subtilis spores (log kill >5) for 30 min exposures, compared with P25-TiO(2). Thus, for the first time, we have demonstrated that titanium dioxide (an environmentally friendly photocatalyst) codoped with silver, carbon, and sulfur can serve as a multifunctional generic biocide as well as a visible light activated photocatalyst.

Reprocessing and sterilization of single-use electrophysiological catheters: removal of organic carbon and protein surface residues.

Although evidence to date indicates that reprocessing electrophysiological (EP) catheters results in clean, sterile devices, some concerns persist with regard to the risk of residual contamination. We examined the ability of a defined reprocessing procedure coupled with a validated sterilization protocol to remove organic carbon and protein residues from worst-case soiled EP catheters resulting in clean, sterile devices. Total organic carbon (TOC) determinations indicated that detergent residues on reprocessed used catheters were nominal and significantly lower than organic carbon levels present on new catheters. Determination of the mean residual organic carbon and protein contaminants on soiled and reprocessed EP catheters further indicated that TOC and protein were reduced (> or =99% of residue removed) below previously reported levels and current accepted standards. Moreover, reprocessed end-of-life catheters (six clinical uses, plus five reprocessings) were examined for residual microorganisms and found to be sterile. End-of-life catheters that had been inoculated with >10(6) CFU Bacillus atrophaeus spores and subjected to a half-cycle ethylene oxide exposure were also found to be sterile. Our data indicate that EP catheter cleaning and reprocessing using defined protocols effectively removes detergent residues and biological contamination, and provides sterile devices.

Occurrence of ciprofloxacin-, trimethoprim-sulfamethoxazole-, and vancomycin-resistant bacteria in a municipal wastewater treatment plant.

The occurrence of antibiotic-resistant bacteria was evaluated in aqueous samples obtained from a municipal wastewater treatment plant. Samples collected from the influent, clarifier effluent, and disinfected effluent were assayed for fecal coliforms, E. coli, and enterococci exhibiting resistance to ciprofloxacin, trimethoprim-sulfamethoxazole, and vancomycin. Membrane filtration of samples was followed by plating on growth media containing various concentrations of antibiotic. Bacterial colonies on plates with antibiotic exposures greater than the clinical minimum inhibitory concentrations were counted and considered resistant. The numbers of drug-resistant organisms in influent ranged from nondetectable to 7 x 10(5) colony-forming units (CFU)/100 mL for fecal coliforms, nondetectable to 5 x 10(4) CFU/100 mL for E. coli, and nondetectable to 6 x 10(5) CFU/100 mL for enterococci. Fecal coliforms, E. coli, and enterococci with reduced susceptibility to antibiotics were also detected in influent and clarifier effluent; however, the disinfected effluent did not contain resistant bacteria. Species-level identification of enterococci revealed that resistant enterococci were predominantly E. faecalis.

Comparison of bacteriophages for use in iodine inactivation: batch and continuous flow studies.

Inactivation rates in batch studies for four commonly used surrogate bacteriophages were measured in stable aqueous iodine solutions for the purpose of determining which was the most suited to evaluate iodine disinfection efficacy in batch and continuous flow conditions. Two types of group Leviviridae bacteriophages were used, Type I (MS2) and Type II (GA), along with group Microviridae, Phi-X174, and group Tectiviridae, PRD1. Inactivation was compared at iodine doses of 1.0-1.5 mg l2/l. MS2 was the most susceptible to iodine inactivation of the four phages tested. Inactivation of naked, icosahedral bacteriophages, MS2 and Phi-X174 demonstrated removals to below detection limits (>99.99%) in less than 10 min. Lipid-containing PRD1 and F+ssRNA GA bacteriophages demonstrated the greatest iodine resistance in batch experiments with an average of 1.82 logs of inactivation (98.5%) after 60 min and 1.05 logs of inactivation (91.1%) after 30 min respectively. Similarly, in continuous flow studies through pentaiodide quaternary ammonium strong base resin, MS2, GA and Phi-X174 were more strongly inactivated than PRD1. The lipid component of PRD1 is thought to enhance resistance to iodine over non-lipid-containing bacteriophages by protecting easily oxidized groups on the protein capsid, but further research is needed before proving this hypothesis. The results from this research may provide a surrogate standard for more rigorous and developed research into the mode of iodine disinfection and its inactivation kinetics.

Nanoscale powders and formulations with biocidal activity toward spores and vegetative cells of bacillus species, viruses, and toxins.

Certain formulations of nanoscale powders possess antimicrobial properties. These formulations are made of simple, nontoxic metal oxides such as magnesium oxide (MgO) and calcium oxide (CaO, lime) in nanocrystalline form, carrying active forms of halogens, for example, MgO. Cl2 and MgO. Br2. When these ultrafine powders contact vegetative cells of Escherichia coli, Bacillus cereus, or Bacillus globigii, over 90% are killed within a few minutes. Likewise, spore forms of the Bacillus species are decontaminated within several hours. Dry contact with aflatoxins and contact with MS2 bacteriophage (surrogate of human enterovirus) in water also causes decontamination in minutes.