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Section VII

Agent Summary Statements

FUNGAL AGENTS


AGENT: Blastomyces dermatitidis

Laboratory-associated local infections following accidental parenteral inoculation with infected tissues or cultures containing yeast forms of B. dermatitidis (67, 87, 107, 108, 168, 199) have been reported. Pulmonary infections have occurred following the presumed inhalation of conidia; two developed pneumonia and one had an osteolytic lesion from which B. dermatitidis was cultured (9, 58). Presumably, pulmonary infections are associated only with sporulating mold forms (conidia).

LABORATORY HAZARDS: Yeast forms may be present in the tissues of infected animals and in clinical specimens. Parenteral (subcutaneous) inoculation of these materials may cause local granulomas. Mold form cultures of B. dermatitidis containing infectious conidia may pose a hazard of aerosol exposure.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 and Animal Biosafety Level 2 practices and facilities are recommended for activities with clinical materials, animal tissues, cultures, and infected animals.

AGENT: Coccidiodes immitis

Laboratory-associated coccidioidomycosis is a documented hazard (18, 56, 59, 60, 61, 105, 113, 133 ,171, 172, 173). Smith reported that 28 of 31 (90%) laboratory-associated infections in his institution resulted in clinical disease, whereas more than half of infections acquired in nature were asymptomatic (200).

LABORATORY HAZARDS: Because of the size (2-5 millimicrons), the arthroconidia are conducive to ready dispersal in air and retention in the deep pulmonary spaces. The much larger size of the spherule (30-60 millimicrons) considerably reduces the effectiveness of this form of the fungus as an airborne pathogen.

Spherules of the fungus may be present in clinical specimens and animal tissues, and infectious arthroconidia in mold cultures and soil samples. Inhalation of arthroconidia from soil samples, mold cultures, or following transformation from the spherule form in clinical materials, is the primary laboratory hazard. Accidental percutaneous inoculation of the spherule form may result in local granuloma formation (184). Disseminated disease occurs at a much greater frequency in blacks and Filipinos than whites.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for handling and processing clinical specimens, identifying isolates, and processing animal tissues. Animal Biosafety Level 2 practices and facilities are recommended for experimental animal studies when the route of challenge is parenteral.

Biosafety Level 3 practices and facilities are recommended for propagating and manipulating sporulating cultures already identified as C. immitis and for processing soil or other environmental materials known or likely to contain infectious arthroconidia.

AGENT: Cryptococcus neoformans

A single account is reported of a laboratory exposure to Cryptococcus neoformans as a result of a laceration by a scalpel blade heavily contaminated with encapsulated cells (83). This vigorous exposure, which did not result in local or systemic evidence of infection, suggests that the level of pathogenicity for normal immunocompetent adults is low. Respiratory infections as a consequence of laboratory exposure have not been recorded.

LABORATORY HAZARDS: Accidental parenteral inoculation of cultures or other infectious materials represents a potential hazard to laboratory personnel -- particularly to those that may be immunocompromised. Bites by experimentally infected mice and manipulations of infectious environmental materials (e.g., pigeon droppings) may also represent a potential hazard to laboratory personnel.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 and Animal Biosafety Level 2 practices and facilities are recommended, respectively, for activities with known or potentially infectious clinical, environmental, or culture materials and with experimentally infected animals.

The processing of soil or other environmental materials known or likely to contain infectious yeast cells should be conducted in a Class I or Class II biological safety cabinet. This precaution is also indicated for culture of the perfect or sexual state of the agent.

AGENT: Histoplasma capsulatum

Laboratory-associated histoplasmosis is a documented hazard in facilities conducting diagnostic or investigative work (151, 152). Pulmonary infections have resulted from handling mold form cultures (132). Local infection has resulted from skin puncture during autopsy of an infected human (185) and from accidental needle inoculation of a viable culture (182). Collecting and processing soil samples from endemic areas has caused pulmonary infections in laboratory workers. Encapsulated spores are resistant to drying and may remain viable for long periods of time. The small size of the infective conidia (less than 5 microns) is conducive to airborne dispersal and intrapulmonary retention. Furcolow reported that 10 spores were almost as effective as a lethal inoculum in mice as 10,000 to 100,000 spores (75).

LABORATORY HAZARDS: The infective stage of this dimorphic fungus (conidia) is present in sporulating mold form cultures and in soil from endemic areas. The yeast form in tissues or fluids from infected animals may produce local infection following parenteral inoculation.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 and Animal Biosafety Level 2 practices and facilities are recommended for handling and processing clinical specimens, identifying isolates, animal tissues and mold cultures, identifying cultures in routine diagnostic laboratories, and for experimental animal studies when the route of challenge is parenteral.

Biosafety Level 3 practices and facilities are recommended for propagating and manipulating cultures already identified as H. capsulatum, as well as processing soil or other environmental materials known or likely to contain infectious conidia.

AGENT: Sporothrix schenckii

S. schenckii has caused a substantial number of local skin or eye infections in laboratory personnel. Most cases have been associated with accidents and have involved splashing culture material into the eye, (69, 197) scratching (21) or injecting (183) infected material into the skin or being bitten by an experimentally infected animal (100, 101). Skin infections have resulted also from handling cultures (57, 124, 137) or necropsy of animals (73) without a known break in technique. No pulmonary infections have been reported to result from laboratory exposure, although naturally occurring lung disease is thought to result from inhalation.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 and Animal Biosafety Level 2 practices and facilities are recommended for all laboratory and experimental animal activities with S. schenckii. Gloves should be worn when handling experimentally infected animals, and during operations with broth cultures that might result in hand contamination.

AGENT: Pathogenic Members of the Genera Epidermophyton, Microsporum and Trichophyton

Although skin, hair and nail infections by these dermatophytid molds are among the most prevalent of human infections, the processing of clinical material has not been associated with laboratory infections. Infections have been acquired through contacts with naturally or experimentally infected laboratory animals (mice, rabbits, guinea pigs, etc.) and, rarely, with handling cultures (84, 119, 151).

LABORATORY HAZARDS: Agents are present in the skin, hair and nails of human and animal hosts. Contact with infected laboratory animals with inapparent or apparent infections is the primary hazard to laboratory personnel. Cultures and clinical materials are not an important source of human infection.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 and Animal Biosafety Level 2 practices and facilities are recommended for all laboratory and experimental animal activities with dermatophytes. Experimentally infected animals should be handled with disposable gloves.

AGENT: Miscellaneous Molds

Several molds have caused serious infection in immunocompetent hosts following presumed inhalation or accidental subcutaneous inoculation from environmental sources. These agents are Cladosporium (Xylohypha) trichoides, Cladosporium bantianum, Penicillium marnefii, Exophiala (Wangiella) dermatitidis, Fonsecaea pedrosoi and Dactylaria gallopava (Ochroconis gallopavum). Even though no laboratory acquired infections appear to have been reported with most of these agents, the gravity of naturally acquired illness is sufficient to merit special precautions in the laboratory. Penicillium marnefii has caused a local inoculation infection in a laboratory worker (169).

LABORATORY HAZARDS: Inhalation of conidia from sporulating mold cultures or accidental injection into the skin during infection or experimental animals is a theoretical risk to laboratory personnel.

RECOMMENDED PRECAUTIONS: Biosafety Level 2 practices and facilities are recommended for propagating and manipulating cultures known to contain these agents.

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Last Modified: 1/2/97
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