Q&A column

Editor: Frederick L. Kiechle, MD, PhD

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Q. Is it a requirement that routine bacteriology cultures (for example, urine, sputum) be plated in a biological safety cabinet in your typical hospital biosafety level 2 laboratory? Is it safe to read these cultures on an open bench?

A.March 2024—Generally, all specimens sent to a clinical microbiology laboratory are considered potentially infectious. Specimens may contain a variety of pathogens that can cause a plethora of infectious diseases. Therefore, clinical laboratories must be primed to process these specimens.

Because laboratories may not be prepared for every pathogenic agent and laboratory personnel may not fully recognize the risks associated with handling clinical specimens, it is important that laboratories follow standard precautions and biosafety level 2 practices to minimize exposure to pathogens.

Biosafety in Microbiological and Biomedical Laboratories, published by the Centers for Disease Control and Prevention and the National Institutes of Health, recommends that all procedures that have the potential for creating infectious aerosols or splashes be conducted within a biological safety cabinet or other physical containment devices.

In addition, the American Society for Microbiology, in its “Interim Clinical Laboratory Guideline for Biological Safety,” states that: “Microorganisms with a low infectious dose, such as Brucella spp., F. tularensis, and Y. pestis, pose the highest risk of infection from primary specimens; however, specimens containing these organisms can still be handled safely using BSL-2 precautions. Exception is reserved for manipulations with a high risk of droplet or aerosol generation, in which case escalated BSL-3 precautions should be considered.”

Clinical laboratories should implement a risk-management approach to biosafety and execute mitigation actions based on the risks identified within their laboratories.

Regarding the reader’s second question, routine bacteriologic cultures derived from clinical specimens in BSL-2 laboratories can be safely manipulated on an open bench unless there is suspicion of a highly infectious pathogenic agent, in which case appropriate physical containment equipment should be used.

Buchan BW, Relich RF, Mahlen SD. Interim clinical laboratory guideline for biological safety. American Society for Microbiology. Jan. 11, 2019. www.asm.org/Guideline/Interim-Clinical-Laboratory-Guideline-for-Biologic

Centers for Disease Control and Prevention, National Institutes of Health. Biosafety in Microbiological and Biomedical Laboratories. 6th ed. U.S. Dept. of Health and Human Services; Rev. June 2020. www.cdc.gov/labs/BMBL.html