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Volume 22, Number 12—December 2016
Research

Infectious Dose of Listeria monocytogenes in Outbreak Linked to Ice Cream, United States, 2015

Régis PouillotComments to Author , Karl C. Klontz, Yi Chen, Laurel S. Burall, Dumitru Macarisin, Matthew Doyle, Kären M. Bally, Errol Strain, Atin R. Datta, Thomas S. Hammack, and Jane M. Van Doren
Author affiliations: Food and Drug Administration, College Park, Maryland, USA (R. Pouillot, K.C. Klontz, Y. Chen, D. Macarisin, M. Doyle, E. Strain, T.S. Hammack, J.M. Van Doren); Food and Drug Administration, Laurel, Maryland, USA (L.S. Burall, A.R. Datta); Via Christi Hospitals, Wichita, Kansas, USA (K.M. Bally)

Main Article

Table 2

Probability of invasive listeriosis after ingestion of ice cream products contaminated with Listeria monocytogenes, United States, 2015

Exposure scenario/model Population, no. cases in population
All, n = 4 Highly susceptible, n = 4 Pregnant, n = 0* Age >65 y, n = 4 Age >75 y, n = 2
Lower†
r Constant
No. L. monocytogenes cells consumed 1.5 × 109 7.2 × 106 2.2 × 107 2.3 × 108 1.2 × 108
Estimated r parameter 2.6 × 10−9 5.5 × 10−7 <2.3 × 10−8 1.7 × 10−8 1.7 × 10−8
Corresponding to 1 case every … servings‡ 37,867 181 >4,363 5,756 5,832
Log10(r) normally distributed
Estimated μ parameter −9.38 −6.19 <(−7.92) −8.00 −8.02
Estimated σ parameter
 0.88
 0.24
 0.54
 0.54
 0.54
Medium§
r Constant
No. L. monocytogenes cells consumed 6.2 × 109 1.5 × 107 8.9 × 107 9.4 × 108 4.8 × 108
Estimated r parameter 6.5 × 10−10 2.7 × 10−7 <5.6 × 10−9 4.3 × 10−9 4.2 × 10−9
Corresponding to 1 case every … servings‡ 154,612 375 >17,812 23,501 23,811
Log10(r) normally distributed
Estimated μ parameter −10.0 −6.40 <(−8.49) −8.60 −8.62
Estimated σ parameter
 0.88
 0.24
 0.54
 0.54
 0.54
High¶
r Constant
No. L. monocytogenes cells consumed 1.4 × 1010 3.3 × 107 2.0 × 108 2.1 × 109 1.0 × 109
Estimated r parameter 2.9 × 10−10 1.2 × 10−7 <2.6 × 10−9 1.9 × 10−9 1.9 × 10−9
Corresponding to 1 case every … servings‡ 339,153 816 >39,071 51,552 52,230
Log10(r) normally distributed
Estimated μ parameter −10.3 −6.80 <(−8.83) −8.97 −8.97
Estimated σ parameter 0.88 0.24 0.54 0.54 0.54

*0.5 used for computation.
†Products 1–3 contaminated beginning 2013 Dec 1; products 4–8 not contaminated.
‡Corresponding to 1 case every … servings, Including 10,000 L. monocytogenes cells.
§Products 1–8 contaminated beginning 2013 Dec 1.
¶Products 1–8 contaminated beginning 2012 Jun 1.

Main Article

Page created: November 16, 2016
Page updated: November 16, 2016
Page reviewed: November 16, 2016
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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