Comparison of disinfectant efficacy when using high-volume directed mist application of accelerated hydrogen peroxide and peroxymonosulfate disinfectants in a large animal hospital.

REASONS FOR PERFORMING STUDY: Effective decontamination of animal holding environments is critical for providing high quality patient care and maintaining a safe working environment. Disinfection of animal holding environments is a significant challenge during times of epidemic disease. OBJECTIVES: The purpose of this study was to evaluate the disinfectant efficacy of 3 strategies for high-volume directed mist application of accelerated hydrogen peroxide and peroxymonosulfate disinfectants; 4.25% accelerated hydrogen peroxide (Accel(®) ; AHP) at a 1:16 dilution and single and double applications of 2% peroxymonosulfate solution (Virkon-S(®) ; VIR-1 and VIR-2) for decontamination of a large animal hospital environment. STUDY DESIGN: Experiment. METHODS: After cleaning and disinfection of the hospital environment, transparencies experimentally contaminated with known concentrations of Staphylococcus aureus, Salmonella enterica and Pseudomonas aeruginosa were placed on vertical surfaces. Disinfectant solution was applied by directed mist application and, after 30 min of contact time, transparencies were collected and individually placed into tubes containing 10 ml Dey-Engley broth. The process was repeated for each disinfectant. Tenfold dilutions of each sample were plated onto tryptic soy blood agar with 5% sheep blood. Bacterial counts from transparencies exposed to disinfectants were compared with counts from control transparencies (unexposed to disinfectants) to evaluate reduction in colony forming units. RESULTS: The least squares mean reduction (log10 ) in colony forming units (CFUs) for S. aureus and P. aeruginosa was 1.5-2.5 logs and approximately 0.8-1.0 logs for S. enterica. Reductions were generally largest for VIR-2 and smallest for AHP, although these differences were not all statistically significant and the magnitude of differences may not be clinically relevant. CONCLUSIONS: For the organisms evaluated, all 3 disinfectants applied as a directed mist were effective at reducing CFUs in a veterinary hospital environment. Effective disinfection using this method of application is dependent on adequate cleaning prior to application, and use of adequate volumes of disinfectant.

2-week inhalation study of N-monomethylformamide in rats.

N-Monomethylformamide (MMF) is a chemical intermediate with potential for inhalation exposure in humans. Human exposures to MMF have occurred in cancer chemotherapy but have been limited due to liver damage. To assess the toxicity of MMF, groups of 15 male rats each were exposed by nose-only inhalation, 6 hr/day, 5 days/week, for 2 weeks to either 0 (control), 50, 130, or 400 ppm MMF. Five rats per group were killed following the 10th exposure, five were killed after a 14-day postexposure recovery period, and five rats were used to determine urinary MMF excretion. Parameters investigated were clinical observations and body weights, clinical pathology, and gross and microscopic pathology including organ weights. Liver damage occurred in rats exposed to either 130 or 400 ppm. This was detected both by increases in serum enzyme activity indicative of liver injury and by microscopic changes in the liver. The changes were more severe in the 400-ppm rats and were partially reversible. Other organs were not adversely affected by inhalation of MMF. The amount of MMF excreted in the urine was dependent on the exposure concentration and MMF was present 14 days postexposure at the higher exposure levels. The no-observed-effect level under the conditions of this experiment was 50 ppm.

Characterization of technetium-99m-L,L-ECD for brain perfusion imaging, Part 1: Pharmacology of technetium-99m ECD in nonhuman primates.

Technetium-99m ethyl cysteinate dimer ([99mTc]ECD) is a neutral, lipophilic complex which rapidly crosses the blood-brain barrier. Brain retention and tissue metabolism of [99mTc]ECD is dependent upon the stereochemical configuration of the complex. While both L,L and D,D enantiomers are extracted by the brain, only the L,L but not the D,D form, is metabolized and retained in the monkey brain (4.7% injected dose initially, T 1/2 greater than 24 hr). Dynamic single photon emission computed tomography imaging studies in one monkey indicates 99mTc-L,L-ECD to be distributed in a pattern consistent with regional cerebral blood flow for up to 16 hr postinjection. Dual-labeled 99mTc-L,L-ECD and [14C]iodoantipyrine autoradiography studies performed 1 hr after administration show cortical gray to white matter ratios of both isotopes to be equivalent (approximately 4-5:1). These data suggest that 99mTc-L,L-ECD will be useful for the scintigraphic assessment of cerebral perfusion in humans.

Sensory irritation potential of selected nasal tumorigens in the rat.

Several important chemicals, including formaldehyde, 1,4-dichloro-2-butene, bis-chloromethyl ether, hexamethylphosphoramide, and epichlorohydrin have been shown to produce nasal tumours in rats following repeated or continuous inhalation exposures. Some of these compounds are respiratory irritants. To determine whether there is a correlation between the ability of a chemical to produce sensory irritation and to elicit nasal tumours, the atmospheric concentration causing a 50% decrease in the respiratory rate (RD50) of male rats was determined. Three other nasal tumorigens, dimethylcarbamoyl chloride, 2,3,4-trichloro-1-butene and 1,2-ethoxy-3-phenoxypropane, were also studied. No correlation between sensory irritation potency and nasal tumorigenic potential was observed. The most potent nasal tumorigen hexamethylphosphoramide, which produces tumours in rats following 12 months' continuous exposure to 50 ppb, failed to cause any decrease in respiratory rate when tested at 351 ppm (an aerosol exposure level which exceeds atmospheric saturation by approximately ten times).

The influence of enterogastric reflux on gastric juice bacterial growth, nitrite, and N-nitroso compound concentrations following gastric surgery.

Detailed analyses were carried out in 207 fasting gastric juice samples obtained at endoscopy or with a nasogastric tube from 50 patients with partial gastrectomy, 43 with vagotomy, 20 with gastric carcinoma and 50 controls. Significantly higher mean pH, nitrite and N-nitroso compound (N-NO) concentrations and nitrate-reducing bacterial cultures were noted following partial gastrectomy compared with normal controls and comparable to findings in gastric cancer. A highly significant relationship (p less than 10(-6)) was also demonstrated between pH and N-NO concentrations, highest levels of which were seen following Billroth II gastrectomy, significantly higher (p = 0.02) than Billroth I, whereas the only change observed following proximal gastric vagotomy was a nearly threefold rise in N-NO compared with normal controls. However, vagotomy and pyloroplasty produced gastric juice changes comparable to those seen with gastrectomy and gastric carcinoma. Thus, the most marked changes were observed following surgical procedures involving increased enterogastric reflux and these findings lend further support to the possible involvement of N-nitroso compounds in the development of gastric cancer following both Billroth I and II gastrectomy and vagotomy with pyloroplasty.