The use of heated citric acid for dialyzer reprocessing.

Dialyzer reprocessing with heated water (100 to 105 degrees C) for 20 h can be used safely in lieu of chemical methods for disinfection. All infective agents including spores are destroyed and depyrogenation may occur. However, these temperatures may result in structural damage to the dialyzer, limiting reuse. Dialyzer reprocessing by using 1.5% citric acid heated to 95 degrees C for 20 h is an alternative method that produces equivalent microbiologic effects. Citric acid is well known as a disinfecting agent used for dialysis equipment. Because there is little structural damage to dialyzer components at 95 degrees C, reuse statistics are improved (mean reuse increased to 12.8). Both small and large molecule clearances and the sieving coefficient for protein are insignificantly altered by the process. Whereas the procedure is relatively simple, quality-assurance indicators are essential. The method has appeal because it avoids the use of chemical germicides. However, at present it has only been tested thoroughly in polysulfone dialyzers with heat-resistant polycarbonate casings and polyurethane resin. The clinical experience is favorable.

Methodological approaches to disinfection of human hepatitis B virus.

Three commercial disinfectants (two quaternary formulations and one phenolic) were tested against human hepatitis B virus (HHBV). The treated virus was assayed for infectivity by the chimpanzee assay and for morphological alteration by the Morphological Alteration and Disintegration Test. The same agents were tested against duck hepatitis B virus in a duck hepatocyte infectivity assay. It is apparent that human and duck hepatitis viruses were relatively susceptible to disinfection, becoming noninfectious after < or = 10 min of contact with the disinfectant. The Morphological Alteration and Disintegration Test accurately predicted activity in the two infectivity tests. The anti-human hepatitis B virus effect of the low-level quaternary ammonium germicides is a novel finding and suggest that members of the family Hepadnaviridae are relatively susceptible to chemical agents.

Bacteriologic studies on electronic hospital thermometers.

Electronic thermometers used in many hospitals require insertion into the mouth of a temperature-sensing probe covered by a pre-packaged probe cover. Handling procedures used by hospital personnel can lead to inadvertent manual contact with the probe cover. We attempted to determine the rate of non-sterility of these probe covers under normal hospital conditions and the extent to which pathogens could be detected on these and other components of the thermometer. Probe covers were removed before entry into the patient's mouth and aseptically inoculated into fluid thioglycollate medium. Subcultures were made to appropriate differential media. Over a 13-week period, 180 covers were cultured on two private hospital services. Forty-three percent were found to be non-sterile; control covers from central supply were only 6% non-sterile. Four percent of the probe covers harbored potential pathogens: coagulase positive Staphylococcus aureus, Streptococcus pyogenes, Enterobacter, and Bacteroides. No attempt was made to correlate these findings with infection. These results indicated a potential infection hazard for high-risk patient groups and a need by hospital personnel to consider this as a possible source of contamination.

Drug resistance studies with topical antiseptics.

Species of Proteus, Serratia, and Pseudomonas became resistant to chlorhexidine after five to eight transfers in vitro. Cross-resistance to benzalkonium chloride also was detected. Resistance to povidone-iodine was not encountered. Chlorhexidine resistance was stable after drug-free transfers of Serratia and Pseudomonas but was transitory for Proteus.

D-values of Bacillus pumilus spores on irradiated devices (inoculated product).

The D-values of Bacillus pumilus spores on various devices ranged from 0.14 to 0.23 Mrads. The majority of devices displayed D-values equal to or less than the value obtained on filter paper. Increased resistivity was also encountered.

Stability of Bacillus pumilus spore strips used for monitoring radiation sterilization.

Dried Bacillus pumilus spore strips had a stable D-value of 0.17 to 0.18 Mrad after 1 year at 5 or 25 C, but resistance was lost at 35 C. Refrigeration did not have an adverse effect on resistance to irradiation. The presence of water at the time of initial preparation increased this resistance to 0.23 to 0.25 Mrad. Proper drying is essential to achieve reproducible results in sterility tests using USP-type biological indicators.

Inactivation of the hemagglutinins of type A influenza viruses by physical and chemical means: an aid to classification.

The effects of temperature and treatment with sodium dodecyl sulfate, Tween 20, dithiothreitol, trypsin, or guanidine on the hemagglutinating capacity of six strains of type A influenza virus (A(0)/PR8/34, A(1)/CAME/46, A(2)/J305/57, A(2)/Bethesda/63, A(2)/HK/Aichi/68, and A(2)/HK/80/68), one strain of swine virus (A/Swine/76/?), and one equine strain (A/Equi-2/63) were determined. The two Hong Kong strains could be readily distinguished from the earlier A(2) strains by the resistance of their hemagglutinins to trypsin treatment and their inability to recover hemagglutinating capacity after removal of dithiothreitol from treated virus preparations. In these respects, the equine strain most closely resembled the Hong Kong variants. The pattern of hemagglutination inactivation also set the swine, PR8, and CAME strains apart from each other as well as from the other five strains. The results suggest that separation of type A viruses into groups by the pattern of inactivation of their hemagglutinins may be a valuable adjunct to standard serology for a more definite classification of these viruses.

Effects of l-(2-nitro-l-imidazolyl)-3-methoxy-2-propanol and 2-methyl-5-nitroimidazole-l-ethanol against anaerobic and aerobic bacteria and protozoa.

1-(2-Nitro-1-imidazolyl)-3-methoxy-2-propanol (RO 7-0582) and 2-methyl-5-nitroimidazole-1-ethanol (Metronidazole), substances known to be potent trichomonacides, were shown to inhibit obligate anaerobic bacteria in vitro but were essentially without effect at the doses tested against bacteria capable of growing aerobically. A similar effect was noted in vivo in that both substances exhibited good chemotherapeutic activity against infections produced by three species of anaerobic protozoa but were essentially inactive at the doses tested against three species of aerobic protozoa.