Monday, September 26, 2011

Laboratory associated biological hazards

Historically, workers in diagnostic laboratories have always been at higher risk for infection from exposure to infectious materials. Today, the laboratory worker is faced with increased exposure to infectious material from the recognition of new infectious agents, potential use of bioterrorism agents, increasing antimicrobial resistance, and introduction of new diagnostic techniques and instrumentation. In addition, improper handling of biologic wastes or episodes of laboratory-acquired infection (LAI) could lead to the spread of microorganisms outside the laboratory, although this occurrence has been rare (Harding and Byers, 2000).
LAIs are defined as all infection acquired through laboratory or laboratory-related activities regardless whether they are symptomatic or asymptomatic in nature. LAIs are resulting from occupational exposure to infectious agents (Peterson and Brossette, 2002).
Mode of Transmission and Etiology:
In laboratories, the factors that influence occupationally acquired infections are related to host susceptibility and behavior, the virulence and availability of the pathogen, and the work environment. The most common types of exposure that cause infections include inhalation of aerosols generated by accidents and work practices; percutaneous inoculation through accidents with needles, blades, and broken glassware; ingestion; and contamination of mucous membranes and skin The types of laboratory accidents that are associated with LAIs are listed in Table ( Harding & Byers, 2000).
The manipulation of infectious material in the laboratory often produces aerosol droplets of varying size. Larger droplets rapidly settle from the air and contaminate surfaces. Smaller droplets evaporate and can remain suspended indefinitely. These droplet nuclei (15 urn in diameter) can be inhaled and reach the alveoli of the lungs (Peterson and Brossette, 2002).
Numerous laboratory procedures (e.g., vortexing, mixing, centrifuging, flaming a loop, etc.) produce droplet nuclei. Contact of infectious agents with mucous membranes, conjunctiva, and skin occurs following spills or splashes and accidental aspirations or ingestion. Bench tops, requisitions, equipment, and nearly all items in the laboratory are potentially contaminated (Straton, 2001).
These contaminated items can promote transfer of organisms to mucous membranes through hand-to-face motions or exposure to cuts and abrasions in the skin. Ingestion of infectious materials should not occur through mouth pipetting or food consumption, as these two practices are banned in all clinical laboratories. Laboratory personnel have a high rate of needlesticks and sharp-object accidents that lead to LAIs (Sejvar et al., 2005).
Most of the affected laboratory personnel are microbiologists who may transmit the infection to individuals outside the laboratory. Typhoid fever cases have been associated with handling proficiency test samples and training materials (Straton, 2001).

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