Using selective media to assess aerosolization damage and ultraviolet germicidal irradiation susceptibility of Serratia marcescens
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This study determined whether selective media, McConkey agar (MC) and minimal salt glucose agar (MA) are suitable for monitoring aerosolization damage of airborne Serratia marcescens in our laboratory aerosol exposure system and assessed the relationship between bacterial culturability in these media and ultraviolet germicidal irradiation (UVGI) susceptibility of the bacteria. Two types of bacterial cultures were prepared. The first culture was taken from bacteria growing on Tryptic soy agar (TSA) as complete medium (fresh culture), which provided nearly 100% of MC/MA tolerant bacteria, while the second one was prepared from freezing the fresh culture (frozen culture), which produced 55 and 81% of MC and MA tolerant bacteria, respectively. We monitored bacterial culturability in TSA, MC and MA from these cultures in the nebulizer reservoir and bioaerosls collected on a six-stage Andersen cascade bio-impactor. The results indicated that both concentration and percentage of MC/MA tolerant bacteria maintained at a similar level during nebulization. For the bioaerosols, although the concentration recovered in the media from the fresh culture was higher than that from the frozen culture, the percentage of MC/MA tolerant bacteria was similar to that before aerosolization. We concluded that MC and MA are not suitable for monitoring aerosolization damage of the bacteria. Moreover, culturability of the bacteria in MC and MA has no effect on their survival after aerosolization. With respect to the bacterial susceptibility to UVGI, MC/MA sensitive and tolerant population as well as the fresh and frozen cultures showed the same susceptibility.
Keywordsaerosolization cell damage selective media Serratia marcescens UV germicidal irradition
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I would like to express my gratitude to the Croucher Foundation, Hong Kong for the award of a post-doctoral research fellowship, Drs. Melvin First and Steve Rudnick for reviewing the manuscript, Kevin Banahan for technical support on the experimental chamber and Ginadelle Romain for assistance in undertaking part of the experiments.
- Cox C.S. (1987). The aerobiological pathway of microorganisms. Wiley, ChichesterGoogle Scholar
- Heidelberg J.F., Shahamat M., Levin M., Rahman I., Stelma G., Grim C., Colwell R.R. (1997). Effect of aerosolization on culturability and viability of gram-negative bacteria. Appl Environ Microbiol 63: 3585–3588Google Scholar
- Kowalski W.J., Bahnfleth W.P. (2000). UVGI design basics for air and surface disinfection. HPAC Eng 72: 100–110Google Scholar
- Mitscherlich E., Marth E.H. (1984). Microbial survival in the environment. Springer-Verlag, New YorkGoogle Scholar
- Ray B., Speck M.L. (1973). Freeze-injury in bacteria. Crit Rev Clin Lab Sci 4: 161–213Google Scholar
- Stewart S.L., Grinshpun S.A., Willeke K., Terzieva S., Ulevicius V., Donnelly J. (1995). Effect of impact stress on microbial recovery on an agar surface. Appl Environ Microbiol 61: 1232–1239Google Scholar