Comparison of cloth, paper, and warm air drying in eliminating viruses and bacteria from washed hands.

We compared the efficiency of paper, cloth, and electric warm air drying in eliminating rotaviruses and Escherichia coli remaining on finger pads washed with 70% isopropanol, a medicated liquid soap, an unmedicated liquid soap, or tap water alone. The contaminated area on the finger pads of a volunteer was exposed to the hand-washing agent for 10 seconds and then rinsed in 40 degrees C tap water. The washed areas were dried for 10 seconds by one of the three methods. Irrespective of the hand-washing agent used, electric air drying produced the highest and cloth drying the lowest reduction in the numbers of both test organisms. These findings indicate the importance of selecting the right means for drying washed hands, particularly when less effective hand-washing agents are used.

In vivo protocol for testing efficacy of hand-washing agents against viruses and bacteria: experiments with rotavirus and Escherichia coli.

Ten antiseptic formulations, an unmedicated liquid soap, and tap water alone were compared for their capacities to eliminate human rotavirus from the finger pads of adult volunteers; three of the antiseptics, the soap, and the tap water alone were also tested against Escherichia coli. A fecal suspension of virus or bacterium was placed on each finger pad and air dried. The contaminated site was exposed to the test product for 10 s, rinsed in tap water, and dried on a paper towel. The residual virus or bacterium was then eluted. Selected agents were also tested by an analogous whole-hand method by which the entire palm surfaces of both hands were contaminated. Alcohols (70%) alone or with Savlon reduced the virus titer by greater than 99%, whereas the reductions by Proviodine, Dettol, and Hibisol ranged from 95 to 97%. Aqueous solutions of chlorhexidine gluconate were significantly less effective for virus removal or inactivation than 70% alcohol solutions. Furthermore, Savlon in water (1:200) was found to be much less effective in eliminating the virus (80.6%) than the bacterium (98.9%). The tap water alone and the soap reduced the virus titers by 83.6 and 72.5% and the bacterial titers by 90 and 68.7%, respectively. The results of the whole-hand method agreed well with those of the finger pad protocol. We conclude that the finger pad method is a suitable model for testing the in vivo efficacy of hand-washing agents and emphasize the need for using appropriate test viruses and bacteria.

Rotavirus survival on human hands and transfer of infectious virus to animate and nonporous inanimate surfaces.

We tested the survival of the Wa strain of human rotavirus on the hands of volunteers and also studied infectious virus transfer between animate and inanimate (stainless steel disks) surfaces. The virus was diluted in a 10% suspension of feces, and 10 microliters (1 X 10(3) to 4 X 10(4) PFU) was placed on each of the four fingerpads of the left hand. One milliliter of 20% tryptose phosphate broth in Earle balanced salt solution was used for virus elution from each fingerpad, and the hands were disinfected with 70% ethanol before they were washed with an antiseptic soap and water. At 20, 60, and 260 min after inoculation, approximately 57, 43, and 7%, respectively, of the input infectious virus could be recovered. For virus transfer, the inoculum (2 X 10(4) to 8 X 10(4) PFU) was allowed to dry, and the donor surface was kept in contact with the recipient surface for 10 s at a pressure of approximately 1 kg/cm2. At 20 and 60 min after virus inoculation, 16.1 and 1.8%, respectively, of the input infectious virus could be transferred from the contaminated hand to a clean disk; when a clean hand was pressed against a contaminated disk, virus transfer was 16.8 and 1.6%, respectively. Contact between a contaminated and a clean hand 20 and 60 min after virus inoculation resulted in the transfer of 6.6 and 2.8%, respectively, of the input infectious virus. These findings indicate the potential vehicular role for human hands in the spread of rotaviral infections.

Proficiency testing of conventional drug susceptibility tests of Mycobacterium tuberculosis.

Proficiency testing of indirect drug susceptibility tests of Mycobacterium tuberculosis was begun in 1985 by the Laboratory Centre for Disease Control (LCDC) with the participation of Provincial Public Health Laboratories in Canada. Comparable sets of 60 cultures of Mycobacterium tuberculosis representing 30 strains were distributed by LCDC to the participating laboratories to be tested for drug susceptibility against isoniazid, streptomycin, rifampin, and ethambutol using conventional methodologies. Intralaboratory agreement values determined by comparing results obtained on sets of duplicate cultures were high and were found to vary little from drug to drug and from laboratory to laboratory. Interlaboratory agreement was determined by comparing results reported by participating laboratories to those obtained by the Reference Laboratory. Agreement percentages were found to be lower for drug-resistant cultures than for drug-susceptible cultures. The reliability of drug susceptibility testing results was higher for isoniazid and rifampin, than for ethambutol and streptomycin. This study shows that the higher subsidiary drug concentrations do not compare well with main drug concentrations, especially in the case of streptomycin and ethambutol. The significance of the higher subsidiary concentrations in in vitro susceptibility testing is therefore in need of clarification. The proficiency testing results obtained in this study compare favorably with those reported in other developed countries despite the fact that a variety of testing procedures are used throughout the country.

Effects of different media and methods of inoculum preparation on results of antimicrobial susceptibility testing of Neisseria gonorrhoeae by agar dilution.

The effects of two methods of inoculum preparation (the opacity standard method and a template method) and three different types of media on the penicillin, tetracycline, spectinomycin, and erythromycin MICs for 191 non-penicillinase-producing, 49 penicillinase-producing, and 5 tetracycline-resistant isolates of Neisseria gonorrhoeae were evaluated. Three World Health Organization reference strains (III, V, and VII) were similarly evaluated. Inoculum preparation method did not significantly alter the MIC (i.e., within a twofold dilution) of either susceptible or chromosomally resistant non-penicillinase-producing isolates; MICs achieved by the template method were slightly higher, but these differences were not significant. However, with penicillinase-producing and tetracycline-resistant isolates, the template method, which delivered 10(4) CFU, produced unequivocal MICs (denoting clinical resistance) which were significantly higher than MICs observed with the opacity standard method (inoculum, 10(3) CFU). With penicillin-, spectinomycin-, and erythromycin-containing medium, addition of hemoglobin to the medium produced lower, though not significantly different, MICs with all isolates as compared with MICs on medium without hemoglobin. Media supplemented with hemoglobin produced higher tetracycline MICs with all isolates, which were significantly different (greater than twofold) from MICs on the same hemoglobin-free media. Changes in auxotype did not alter overall observations concerning the effects of different media and inocula on MICs.

The role of isotype and epitope specificity of monoclonal antibody mixtures in immunodiffusion reactions.

Twenty monoclonal antibodies to human alpha-fetoprotein have been characterized in terms of IgG subclass, epitope specificity and immunodiffusion properties. The Ig molecules consisted of six G1, ten G2a and four G2b isotypes. The epitope analysis was conducted by a solid-phase RIA employing 125I-labelled AFP. The RIA analysis resulted in the identification of seven determinants, two of which were specific for one antibody each, while others were specific for two or more antibodies. In Ouchterlony tests with the antibodies, none formed bands of immunoprecipitate when diffused individually against the antigen. Tests with all possible mixtures of pairs of the antibodies (190) resulted in positive immunodiffusion responses with only two mixtures. These each contained antibodies of the 2b isotype and demonstrated distinct epitope specificities. The immunodiffusion of mixtures of three antibodies from a group of 12 that were selected to represent equal numbers of isotypes resulted in 84 positive responses and 136 negative responses, i.e. from a total of 220 mixtures. A striking correlation was noted between positive immunodiffusion tests and composition of antibody isotypes and of epitope specificities of the mixtures. Each mixture was found to contain antibodies of at least one 2b isotype and of different epitope specificities. None of the mixtures that lacked a 2b isotype (56) responded in immunodiffusion tests. Similarly, in instances (46) in which the epitope specificities of the antibodies in the mixture were the same, i.e. duplicated or triplicated, the results were again negative despite the presence of a 2b isotype. The comparison of these studies with similar studies of a smaller group of antibodies to pregnancy-specific beta 1-glycoprotein strongly suggests that the G3 antibody isotype may have an immune precipitation enhancing effect similar to the G2b isotype.

Preparation and calibration of a reference preparation for human serum proteins.

A reference preparation for human serum proteins (RPHSP) has been developed to aid in the standardization of a wide variety of protein analytes commonly tested by immunodiagnostic procedures. The U.S. national RPHSP was used to cross-calibrate our reference serum by single radial immunodiffusion for the analytes alpha 1-acid glycoprotein, alpha 1-antitrypsin, alpha 2-macroglobulin, ceruloplasmin, C3, C4, haptoglobin, transferrin, IgA, IgG, IgM and by Laurell "rocket" assay for albumin. The statistical evaluation of the cross-calibration study indicates high precision of estimates of the specific proteins assigned to the Canadian RPHSP relative to those of the U.S. reference preparation. Protein concentrations were assigned in both WHO international units (when available) and mass units.

Comparative bioavailabilities from truncated blood level curves.

The period of time after administration over which blood level measurements are required to obtain a reliable bioavailability comparison of two or more formulations of the same drug was considered by the analysis of bioavailability data taken from the literature. The drugs examined, selected to represent a range of absorption and elimination half-lives, were acetaminophen, aminosalicylic acid, chloramphenicol, chlordiazepoxide, digoxin, isoniazid, phenylbutazone, sulfamethizole, tetracycline, and warfarin. For most drugs, ratios of areas under the curve changed little between the end of the absorption period and the time when blood sampling was terminated. Reliable bioavailability comparisons among different brands of the drugs apparently could have been made by blood sampling over 24 hr or less.