Population structure of Listeria monocytogenes serotype 4b isolates from sporadic human listeriosis cases in the United States from 2003 to 2008.

Listeria monocytogenes can cause severe food-borne disease (listeriosis). Numerous outbreaks have involved three serotype 4b epidemic clones (ECs): ECI, ECII, and ECIa. However, little is known about the population structure of L.

Listeriosis outbreaks and associated food vehicles, United States, 1998-2008.

Listeria monocytogenes, a bacterial foodborne pathogen, can cause meningitis, bacteremia, and complications during pregnancy. This report summarizes listeriosis outbreaks reported to the Foodborne Disease Outbreak Surveillance System of the Centers for Disease Control and Prevention during 1998-2008. The study period includes the advent of PulseNet (a national molecular subtyping network for outbreak detection) in 1998 and the Listeria Initiative (enhanced surveillance for outbreak investigation) in 2004.

Invasive listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009: further targeted prevention needed for higher-risk groups.

Background: Listeriosis can cause severe disease, especially in fetuses, neonates, older adults, and persons with certain immunocompromising and chronic conditions. We summarize US population-based surveillance data for invasive listeriosis from 2004 through 2009.

Methods: We analyzed Foodborne Diseases Active Surveillance Network (FoodNet) data for patients with Listeria monocytogenes isolated from normally sterile sites.

Atypical Listeria monocytogenes serotype 4b strains harboring a lineage II-specific gene cassette.

Listeria monocytogenes is the etiological agent of listeriosis, a severe food-borne illness. The population of L. monocytogenes is divided into four lineages (I to IV), and serotype 4b in lineage I has been involved in numerous outbreaks.

Re-evaluation, optimization, and multilaboratory validation of the PulseNet-standardized pulsed-field gel electrophoresis protocol for Listeria monocytogenes.

The PulseNet Methods Development and Validation Laboratory began a re-evaluation of the standardized pulsed-field gel electrophoresis (PFGE) protocols with the goal of optimizing their overall performance and robustness. Herein, we describe a stepwise evaluation of the PulseNet-standardized PFGE protocol for Listeria monocytogenes that led to the modification of several steps which significantly improved the overall appearance and reproducibility of the resulting PFGE data. These improvements included the following: (1) reducing the cell suspension concentration, (2) increasing lysozyme incubation temperature from 37 degrees C to 56 degrees C, and (3) decreasing the number of units of restriction enzymes AscI and ApaI.

Listeria marthii sp. nov., isolated from the natural environment, Finger Lakes National Forest.

Four isolates (FSL S4-120(T), FSL S4-696, FSL S4-710, and FSL S4-965) of Gram-positive, motile, facultatively anaerobic, non-spore-forming bacilli that were phenotypically similar to species of the genus Listeria were isolated from soil, standing water and flowing water samples obtained from the natural environment in the Finger Lakes National Forest, New York, USA. The four isolates were closely related to one another and were determined to be the same species by whole genome DNA-DNA hybridization studies (>82 % relatedness at 55 degrees C and >76 % relatedness at 70 degrees C with 0.0-0.

Short-term genome evolution of Listeria monocytogenes in a non-controlled environment.

Background: While increasing data on bacterial evolution in controlled environments are available, our understanding of bacterial genome evolution in natural environments is limited. We thus performed full genome analyses on four Listeria monocytogenes, including human and food isolates from both a 1988 case of sporadic listeriosis and a 2000 listeriosis outbreak, which had been linked to contaminated food from a single processing facility. All four isolates had been shown to have identical subtypes, suggesting that a specific L.

Reduction in the incidence of invasive listeriosis in foodborne diseases active surveillance network sites, 1996-2003.

Background: Listeriosis is a leading cause of death among patients with foodborne diseases in the United States. Monitoring disease incidence is an important element of listeriosis surveillance and control.

Method: We conducted population-based surveillance for Listeria monocytogenes isolates obtained from normally sterile sites at all clinical diagnostic laboratories in the Foodborne Diseases Active Surveillance Network from 1996 through 2003.

Multicenter validation of a multiplex PCR assay for differentiating the major Listeria monocytogenes serovars 1/2a, 1/2b, 1/2c, and 4b: toward an international standard.

The performance of a multiplex PCR assay that separates the four major serovars of the pathogenic Listeria monocytogenes into four distinct PCR groups was evaluated through a multicenter typing study. Identical panels of 90 Listeria isolates were distributed to five participating laboratories that were blind to the nature of the isolates. Isolates were characterized using the previously standardized protocol.

Multistate outbreak of Listeriosis linked to turkey deli meat and subsequent changes in US regulatory policy.

Background: Listeriosis, a life-threatening foodborne illness caused by Listeria monocytogenes, affects approximately 2500 Americans annually. Between July and October 2002, an uncommon strain of L. monocytogenes caused an outbreak of listeriosis in 9 states.

Microbiological aspects of the investigation that traced the 1998 outbreak of listeriosis in the United States to contaminated hot dogs and establishment of molecular subtyping-based surveillance for Listeria monocytogenes in the PulseNet network.

A multistate outbreak of listeriosis occurred in the United States in 1998 with illness onset dates between August and December. The outbreak caused illness in 108 persons residing in 24 states and caused 14 deaths and four miscarriages or stillbirths. This outbreak was detected by public health officials in Tennessee and New York who observed significant increases over expected listeriosis cases in their states.

Outbreak of listeriosis among Mexican immigrants as a result of consumption of illicitly produced Mexican-style cheese.

Background: In 2000, an outbreak of listeriosis among Hispanic persons was identified in Winston-Salem, North Carolina. The objectives of the present study were to identify the source of, strains associated with, and risk factors for Listeria monocytogenes infection for patients affected by the outbreak.

Methods: Microbiological, case-control, and environmental investigations were conducted.

Genetic markers unique to Listeria monocytogenes serotype 4b differentiate epidemic clone II (hot dog outbreak strains) from other lineages.

A small number of closely related strains of Listeria monocytogenes serotype 4b, designated epidemic clone I (ECI), have been implicated in numerous outbreaks of food-borne listeriosis described during the past two decades in Europe and North America. In 1998 to 1999, a multistate outbreak traced to contaminated hot dogs involved a different strain type of serotype 4b, with genetic fingerprints rarely encountered before. In spite of the profound economic and public health impact of this outbreak, the implicated bacteria (designated epidemic clone II [ECII]) have remained poorly characterized genetically, and nucleotide sequences specific for these strains have not been reported.

Comparison of Three Selective Enrichment Methods for the Isolation of Listeria monocytogenes from Naturally Contaminated Foods.

Three selective enrichment procedures-the U.S. Food and Drug Administration (FDA) method, the U.