PFGE for Salmonella infection Surveillance | CDC EID

EID Journal Home > Volume 16, Number 6–June 2010

Volume 16, Number 6–June 2010
Dispatch
Pulsed-field Gel Electrophoresis for Salmonella Infection Surveillance, Texas, USA, 2007
Stephen G. Long, Herbert L. DuPont, Linda Gaul, Raouf R. Arafat, Beatrice J. Selwyn, Joan Rogers, and Eric Casey
Author affiliations: Houston Department of Health and Human Services, Houston, Texas, USA (S.G. Long, R.R. Arafat, J. Rogers); University of Texas School of Public Health, Houston (H.L. DuPont, B.J. Selwyn); St. Luke's Episcopal Hospital, Houston (H.L. DuPont); Baylor College of Medicine, Houston (H.L. DuPont); and Texas Department of State Health Services, Austin, Texas, USA (L. Gaul, E. Casey)

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Abstract
To identify sources of transmission for area clusters, in 2007 the Houston Department of Health and Human Services conducted an 8-month study of enhanced surveillance of Salmonella infection. Protocol included patient interviews and linking the results of interviews to clusters of pulsed-field gel electrophoresis patterns detected by the local PulseNet laboratory.
To detect Salmonella clusters, public health laboratories perform pulsed-field gel electrophoresis (PFGE) that provides a PFGE pattern, or DNA fingerprint. If the PFGE patterns of isolates from >2 persons are indistinguishable, the responsible bacteria may be related to a common source (1–3). PulseNet is a network of public health laboratories coordinated by the Centers for Disease Control and Prevention (CDC), in which bacteria that cause foodborne diseases, including Salmonella isolates, are analyzed by using PFGE. This network provides the means to rapidly compare PFGE patterns from isolates submitted in different geographic areas. State and local laboratories upload PFGE patterns to the national CDC PulseNet database. Indistinguishable patterns at the national level might represent a large multistate outbreak (4–6).

As a city health department located in the state of Texas, the Houston Department of Health and Human Services (HDHHS) investigates all local Salmonella cases to detect outbreaks and vehicles of transmission. The HDHHS laboratory has been certified as a PulseNet laboratory since 2001 and serves residents of Houston (≈2.1 million persons) and adjacent counties.

Because PFGE patterns obtained by a local health department may appear to be sporadic or unrelated to a more generalized process (2), local public health practitioners may gain a larger perspective by receiving notification of state and national clusters (4,5). During 2002–2005, before this study was conducted but during a time HDHHS was in routine communication with PulseNet, most local PFGE patterns were not recognized as linked to statewide or nationwide clusters.

In this study, HDHHS sought to determine more rigorously the utility of PFGE in local surveillance (as opposed to national surveillance) in detecting area clusters and vehicles of transmission. Another goal was to determine how local PFGE patterns and clusters are associated with larger-scale clusters. The study was approved by the Committee for the Protection of Human Subjects, University of Texas Health Science Center.

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PFGE for Salmonella infection Surveillance | CDC EID