The impact of Culture-Independent Diagnostic Testing on Salmonella incidence and surveillance in the State of Georgia from 2008 – 2018. Open Access

Kassner, Dayton (Spring 2019)

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Background: Salmonella has the potential to be a significant public health concern; the estimated burden of Salmonella in the U.S. is 1.2 million cases, 23,000 hospitalizations and 450 deaths every year. CIDT use for Salmonella detection began in 2011. CIDTs create challenges for surveillance epidemiologists who use historical data to establish trends for Salmonella incidence. The objectives of this study are to identify the impact of CIDT use on Salmonella surveillance and incidence in Georgia and determine whether any change in incidence differed amongst demographic groups.

Methods: The data was obtained through Georgia’s State Electronic Notifiable Disease Surveillance System. Salmonella cases were arranged into three test type categories: culture positive only, culture positive and CIDT positive, and CIDT positive only. Differences in Salmonella incidence rates were analyzed with percent change calculations using Poisson regression. Analysis on the changes in the rates of positive cultures and positive CIDTs was done using Poisson regression. Analysis on Salmonella incidence amongst different demographic groups was conducted with Poisson regression.

Results: Among the 27,789 Salmonella cases, 24,704 (88.9%) were culture positive only, 1,564 (5.6%) were culture positive and CIDT positive, and 1,521 (5.5%) were CIDT positive only. 2010 and 2017 had the highest and lowest total Salmonella incidence rates of 28.77 and 22.48 Salmonella cases per 100,000 persons, respectively. Culture positive only Salmonella incidence rates decreased significantly after 2012. Both culture and CIDT positive or CIDT positive only Salmonella incidence rates increased significantly after 2012.

Discussion: The increased use of CIDTs in Georgia does not appear to have had any impact on Salmonella incidence rates. The impact of CIDTs was still noticeable for Salmonella surveillance. The total number of Salmonella cases with a positive culture decreased significantly. A loss of cultures will result in a loss of bacterial isolates. Bacterial isolates are used in variety of ways in Salmonella surveillance, such as monitoring trends in Salmonella subtypes, detecting outbreaks throughout Georgia, identifying vehicles in outbreaks and testing antimicrobial susceptibility. Future studies will need to be conducted to monitor CIDT use in Salmonella surveillance and other foodborne disease surveillance as CIDTs are still a relatively novel testing type.

Table of Contents

Table of Contents


Literature Review.. 7

Background. 10


Study Design. 14

Data Acquisition. 14

Data Cleaning and Management. 15

Data Analysis. 16



Strengths and Limitations. 23

Future Directions. 24



Table 1. 30

Table 2. 31

Table 3a. 32

Table 3b. 32

Table 4. 33

Table 5. 34

Table 6. 35


Figure 1. 36

Figure 2. 37


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