A twenty-five year review of laboratory-acquired human infections at the National Animal Disease Center.

The National Animal Disease Center's experience with personnel exposure or infection with pathogenic agents is summarized. A total of 128 laboratory-associated exposures to infectious disease agents were reported. Of these exposures, 103 resulted from known accidents. The other 25 were identified only after the development of clinical or serological manifestations of infection. Thirty-four cases of laboratory-acquired infections were reviewed. Class 3 organisms--Chlamydia sp., Brucella sp. and Mycobacterium sp.--were responsible for 76% of the infections encountered, with Brucella sp. incriminated most frequently. The most commonly reported cause of exposure was associated with hypodermic syringe use. Unknown routes of exposure, presumed to be aerosol related, were the overwhelming explanation involved in the laboratory-associated infections.

Autoclavable ultrahigh-efficiency filter for use with flexible film germfree animal isolators.

An autoclavable ultrahigh-efficiency filter unit, which accommodated 99.98% efficient respirator filter cartridges, was built for use with flexible film germfree animal isolators.

Safe, convenient, portable pipettor.

A dafe, convenient, portable pipetting device that will accommodate any size pipette is described. A vacuum bulb eliminates the need for external vacuum. Necessary components, fabrication procedures, and operating techniques are given.

Laboratory-acquired infections at the National Animal Disease Center 1960--1976.

Experience with exposure to, or infection with pathogenic agents at the National Animal Disease Center is summarized. A total of 60 laboratory-associated exposures to infectious disease agents were reported. Forty-nine exposures resulted from known accidents, but the other 11 were identified only after the development of clinical or serological manifestations of infection. Eighteen cases of laboratory-acquired infections were reviewed. Brucellosis, the most frequently reported laboratory-acquired infection, accounted for one-half of the cases summarized. Three cases of leptospirosis, two cases of Newcastle disease, two cases of ringworm, and a single infection with Mycobacterium bovis and with Salmonella arizonae were also encountered. The most frequently reported causes of exposure were: auto-inoculation or spray exposure associated with the use of the hypodermic syringe, cuts or lacerations, direct contact with infected animals, and mouth pipetting. Although the infecting event could not be identified in 11 infections, presumptive evidence suggests aerogenic transmission as a probable route of exposure in a number of such cases.

Isolation and metabolism cage system for newborn pigs.

An isolation system was designed and constructed for isolating normal and infected newborn pigs. The system consisted of an outer cage fitted with a biological diffusion filter and a dunk bath entry system and an inner metabolism cage to contain the pig. When tested with S-13 bacteriophage, the isolation and metabolism cage system was at least 99% efficient in preventing the entry or escape of microorganism. A total of 267 Escherichia coli-infected newborn pigs have been isolated in these units, with no cross contaminations.

Safe, convenient pipetting station.

A simple convenient pipetting station is described that eliminates the need for mouth pipetting. Necessary components, fabrication procedures, and operating techniques are given.

Phenol concentrations in the air from disinfection solutions.

Phenol concentrations in the air near phenol disinfectant solutions were measured. The concentration of phenol was not excessive, except for hot solutions with which exposure would normally be for a very short time. Adverse physiological reactions may occur at air levels below the threshold limit values which may be especially hazardous to those persons exposed to organisms causing respiratory diseases.

Self-sterilizing inoculating loop.

A self-sterilizing inoculating loop consisting of a step-down transformer and an adjustable timing circuit are described.

Safe, convenient pipetting device.

A finger-mounted pipetting device which can be fabricated in the laboratory is described.

Method for quantitating formaldehyde gas in air.

A quick, simple method for collecting and assaying the disinfecting concentrations of formaldehyde vapor is described.

Portable ethylene oxide sterilization chamber.

A portable ethylene oxide sterilization chamber was designed, constructed, and tested for use in the sterilization of embolectomy catheters. The unit can accommodate catheters up to 40 inches (101.6 cm) in length and can be operated for less than 4 cents per cycle. A constant concentration of 500 mg of ethylene oxide per liter of space and holding periods of 4 and 6 hr at 43 and 22 C, respectively, were adequate when tested with B. subtilis spores. The estimated cost of construction was $165.00. If temperature control is unnecessary, the cost is approximately $80.00.

Fluorometric method for determining the efficiency of spun-glass air filtration media.

The procedures and equipment needed to measure filtration efficiency by means of fluorescent aerosols are described. The filtration efficiency of individual lots of spun-glass air filtration medium or of entire air filtration systems employing such media was determined. Data relating to the comparative evaluation of spun-glass filter media by means of the fluorometric method described, as well as by conventional biological procedures, are presented.

Influence of relative humidity on the survival of some airborne viruses.

A system for studying the effects of relative humidity (RH) and temperature on biological aerosols, utilizing a modified toroid for a static aerosol chamber, is described. Studies were conducted at 23 C and at three RH levels (10, 35, and 90%) with four viruses (Newcastle disease virus, infectious bovine rhinotracheitis virus, vesicular stomatitis virus, and Escherichia coli B T3 bacteriophage). Virus loss on aerosol generation was consistently lower at 90% than at 10 or 35% RH. When stored at 23 C, Newcastle disease virus and vesicular stomatitis virus survived best at 10% RH. Infectious bovine rhinotracheitis virus and E. coli B T3 bacteriophage survived storage at 23 C best at 90% RH.

Role of differential air pressure zones in the control of aerosols in a large animal isolation facility.

The uncontrolled transmission of hog cholera in a large animal isolation facility, designed to control the movement of aerosols within and between individual wings of a multiunit building, indicated the need for a critical study of aerosol behavior under existing conditions of operation. Studies with aerosols of Escherichia coli B T3 bacteriophage (T3 coliphage) conclusively demonstrated the impossibility of obtaining the desired control by means of a "static" air balance relationship between adjacent areas within the facility. Modifications needed to provide the desired control of the air-handling system are outlined and discussed.