Abstract
This study investigated aerosolized viable bacteria in a university research laboratory during operation of an acoustic-assisted flow cytometer for antimicrobial susceptibility testing by sampling room air before, during and after flow cytometer use. The aim was to assess the risk associated with use of an acoustic-assisted flow cytometer analyzing unfixed bacterial suspensions. Air sampling in a nearby clinical laboratory was conducted during the same period to provide context for the existing background of microorganisms that would be detected in the air. The three species of bacteria undergoing analysis by flow cytometer in the research laboratory were Klebsiella pneumoniae, Burkholderia thailandensis and Streptococcus pneumoniae. None of these was detected from multiple 1000 L air samples acquired in the research laboratory environment. The main cultured bacteria in both locations were skin commensal and environmental bacteria, presumed to have been disturbed or dispersed in laboratory air by personnel movements during routine laboratory activities. The concentrations of bacteria detected in research laboratory air samples were reduced after interventional cleaning measures were introduced and were lower than those in the diagnostic clinical microbiology laboratory. We conclude that our flow cytometric analyses of unfixed suspensions of K. pneumoniae, B. thailandensis and S. pneumoniae do not pose a risk to cytometer operators or other personnel in the laboratory but caution against extrapolation of our results to other bacteria and/or different flow cytometric experimental procedures.
Highlights
Flow cytometry techniques have been used to analyze bacteria for several decades[1,2], and for assessing the effects of antimicrobial agents since the 1980s3–5
There was a significant fall in bacterial counts from air samples collected adjacent to the flow cytometer (54 CFU/1000 L air falling to 15.5 CFU/1000 L air) after interventional cleaning of research laboratory surfaces and replacement of gowns (Figure 2)
Identities of the commonest bacterial species isolated on blood agar† from 1000 L air samples, arranged by laboratory location. †sampling onto horse blood agar (HBA) frequently yielded plates crowded with microbial growth
Summary
Flow cytometry techniques have been used to analyze bacteria for several decades[1,2], and for assessing the effects of antimicrobial agents since the 1980s3–5. Concerns about laboratory biosafety and containment increased after 20017,8 and led to higher physical containment levels for select biothreat agents and some bacterial species such as Neisseria meningitidis, prone to transmission by aerosols generated during laboratory procedures[9,10]. Given these concerns about bioaerosol transmission risks, it is not surprising that standards for bioaerosol risk assessment and mitigation have been recommended for fluorescence-activated cell sorting protocols[11,12]. Though the cytometer we used had no cell sorting function and would not generally produce aerosols,[14,15] we decided to conduct an assessment to confirm that viable bacteria are not aerosolized during use before progressing with any analysis of potentially more hazardous aerosol-transmitted species such as Neisseria meningitidis, Mycobacterium tuberculosis and Burkholderia pseudomallei
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