Assessment of iodine-treated filter media for removal and inactivation of MS2 bacteriophage aerosols.

AIMS: To investigate the performance of an iodine-releasing filter medium for use as a protective device against airborne pathogens. METHODS AND RESULTS: The filter's physical and viable removal efficiencies (VRE) were investigated with challenges of MS2 bacteriophage aerosols, and the infectivity of MS2 collected on the filter was analysed. To test a proposed inactivation mechanism, media containing thiosulfate or bovine serum albumin (BSA) were put in impingers to quench and consume I(2) released from the filter. In direct plating experiments, treated filters presented significantly higher VREs than did untreated filters; however, collection in excess BSA decreased VRE by half and in thiosulfate the apparent VRE decreased drastically. No significant difference in infectivity of retained viruses on treated and untreated filters was observed at the same environmental condition. CONCLUSIONS: Evidence presented herein for competition by dissolved I(2) in infectivity assays supports a mechanism of induced displacement and capture of I(2.) It also requires that dissociation of iodine from the filter and capture of iodine by MS2 aerosols as they pass through the filter be factored in the design of the assessment methodology. The filter's strong retention capability minimizes reaerosolization but also makes it difficult to discriminate the antimicrobial effect at the surface. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the direct plating assay method to be sensitive to interference by iodine-releasing materials. This requires reevaluation of earlier reports of VRE measurements.

Efficacy of iodine-treated biocidal filter media against bacterial spore aerosols.

AIMS: To assess the effectiveness of iodine-treated biocidal filter media against bacterial spore aerosols. METHODS AND RESULTS: Bacillus subtilis spores were aerosolized and introduced into a filtration system. Both treated and untreated filters exhibited high viable removal efficiency (>99.996%) with negligible variation in pressure drop during the entire experiment. The viability of collected spores on the filter was investigated by enumeration of spores extracted from the filter by vortexing. At room temperature and low relative humidity (RH), the survival fraction of the treated filter was significantly lower than that of the untreated filter (P-value < 0.05). Meanwhile, at room temperature and high RH and at high temperature and high RH, the survival fractions on the treated medium were statistically the same as the untreated control at room temperature and low RH. CONCLUSIONS: Both treated and untreated filters achieved excellent viable removal efficiency for spores. The pressure drop of the treated filter was not affected by the iodine treatment. The viability of collected bacterial spores was decreased because of the exertion of iodine disinfectant. SIGNIFICANCE AND IMPACT OF THE STUDY: The evaluation demonstrates that the iodine-treated filter is a viable medium for respiratory protection against infectious spore aerosols. The results warrant further evaluation of smaller biological agents, which exhibit higher penetration.

Domains in the 1alpha dynein heavy chain required for inner arm assembly and flagellar motility in Chlamydomonas.

Flagellar motility is generated by the activity of multiple dynein motors, but the specific role of each dynein heavy chain (Dhc) is largely unknown, and the mechanism by which the different Dhcs are targeted to their unique locations is also poorly understood. We report here the complete nucleotide sequence of the Chlamydomonas Dhc1 gene and the corresponding deduced amino acid sequence of the 1alpha Dhc of the I1 inner dynein arm. The 1alpha Dhc is similar to other axonemal Dhcs, but two additional phosphate binding motifs (P-loops) have been identified in the NH(2)- and COOH-terminal regions. Because mutations in Dhc1 result in motility defects and loss of the I1 inner arm, a series of Dhc1 transgenes were used to rescue the mutant phenotypes. Motile cotransformants that express either full-length or truncated 1alpha Dhcs were recovered. The truncated 1alpha Dhc fragments lacked the dynein motor domain, but still assembled with the 1beta Dhc and other I1 subunits into partially functional complexes at the correct axoneme location. Analysis of the transformants has identified the site of the 1alpha motor domain in the I1 structure and further revealed the role of the 1alpha Dhc in flagellar motility and phototactic behavior.