This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Niemira, B. A. Articles by Solomon, E. B. Search for Related Content PubMed PubMed Citation Articles by Niemira, B. A. Articles by Solomon, E. B. Agricola Articles by Niemira, B. A. Articles by Solomon, E. B.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, May 2005, p. 2732-2736, Vol. 71, No. 5
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.5.2732-2736.2005

Sensitivity of Planktonic and Biofilm-Associated Salmonella spp. to Ionizing Radiation

Brendan A. Niemira^* and Ethan B. Solomon

Food Safety Intervention Technologies Research Unit, Eastern Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, Wyndmoor, Pennsylvania 19038

Received 17 September 2004/ Accepted 8 December 2004

Salmonella enterica forms biofilms that are relatively resistant to chemical sanitizing treatments. Ionizing radiation has been used to inactivate Salmonella on a variety of foods and contact surfaces, but the relative efficacy of the process against biofilm-associated cells versus free-living planktonic cells is not well documented. The radiation sensitivity of planktonic or biofilm-associated cells was determined for three food-borne-illness-associated isolates of Salmonella. Biofilms were formed on sterile glass slides in a coincubation apparatus, using inoculated tryptic soy broth, incubated at 37°C for 48 h. Resulting biofilms were 18 to 24 µm in height as determined by confocal scanning laser microscopy. The planktonic and biofilm cultures were gamma irradiated to doses of 0.0 (control), 0.5, 1.0, 1.5, 2.0 and 2.5 kGy. The D₁₀ value (the dose of radiation required to reduce a population by 1 log₁₀, or 90%) was calculated for each isolate-culture based on surviving populations at each radiation dose. The D₁₀ values of S. enterica serovar Anatum were not significantly (P < 0.05) different for biofilm-associated (0.645 kGy) and planktonic (0.677 kGy) cells. In contrast, the biofilm-associated cells of S. enterica serovar Stanley were significantly more sensitive to ionizing radiation than the respective planktonic cells, with D₁₀ values of 0.531 and 0.591 kGy, respectively. D₁₀ values of S. enterica serovar Enteritidis were similarly reduced for biofilm-associated (0.436 kGy) versus planktonic (0.535 kGy) cells. The antimicrobial efficacy of ionizing radiation is therefore preserved or enhanced in treatment of biofilm-associated bacteria.

---

* Corresponding author. Mailing address: Eastern Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, PA 19038. Phone: (215) 836-3784. Fax: (215) 233-6445. E-mail: bniemira{at}errc.ars.usda.gov.

---

Applied and Environmental Microbiology, May 2005, p. 2732-2736, Vol. 71, No. 5
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.5.2732-2736.2005

This article has been cited by other articles:

• Niemira, B. A. (2007). Irradiation Sensitivity of Planktonic and Biofilm-Associated Escherichia coli O157:H7 Isolates Is Influenced by Culture Conditions. Appl. Environ. Microbiol. 73: 3239-3244 [Abstract] [Full Text]