Pulsed-Field Gel Electrophoresis (PFGE) Analysis of Temporally Matched Listeria monocytogenes Isolates from Human Clinical Cases, Foods, Ruminant Farms, and Urban and Natural Environments Reveals Source-Associated as Well as Widely Distributed PFGE Types

Abstract

A total of 495 temporally and geographically matched Listeria monocytogenes isolates from human clinical cases, foods, ruminant farms, and urban and natural environments were used to investigate L. monocytogenes pulsed-field gel electrophoresis (PFGE) type diversity. Two-enzyme (AscI and ApaI) PFGE discriminated 310 PFGE types and exhibited higher overall discriminatory power ( Seven PFGE types showed significant associations with specific sources, including one and four PFGE types, respectively, associated with human clinical cases and foods. Spatial analysis of 13 PFGE types occurring >5 times showed that two PFGE types were specific to a single processing facility each, where they appear to have persisted over time. Nine PFGE types were geographically widespread and occurred among isolates from multiple sources. For example, a PFGE type that matched isolates from listeriosis outbreaks in Los Angeles and Switzerland occurred among isolates from farms (n ‫؍‬ 7), human clinical cases (n ‫؍‬ 4), environmental sources (n ‫؍‬ 3), and foods (n ‫؍‬ 1). Our data indicate that (i) PFGE is highly discriminatory for the subtyping of L. monocytogenes, (ii) some L. monocytogenes PFGE types are associated with specific sources, and (iii) some L. monocytogenes PFGE types are widely distributed and appear to be stable and pandemic. Large PFGE type databases representing isolates from different sources are thus needed to appropriately interpret subtype data in epidemiological investigations and to identify common as well as source-specific PFGE types.

Increased In Vitro Adherence and On-Farm Persistence of Predominant and Persistent Listeria monocytogenes Strains in the Milking System

“…Listeria monocytogenes has been isolated from many locations within dairy farms, including feces (32,39,40), animal drinking water (29,37,40), feeds or feed components (37,39), and milking equipment (29,30). A potential link between animal production systems and human listeriosis cases exists, as was suggested by previous studies that described the presence of L. monocytogenes ribotypes (39) or pulsed-field gel electrophoresis (PFGE) types (3,17) from farms that matched those observed for isolates from human listeriosis cases.…”

Diverse Geno- and Phenotypes of Persistent Listeria monocytogenes Isolates from Fermented Meat Sausage Production Facilities in Portugal

“…While molecular subtyping of L. monocytogenes can provide valuable information not only for human disease surveillance but also for improved control of this pathogen along the food chain (22,23), more widespread application of these methods is still hampered by a variety of factors, including, but not limited to, (i) the considerable cost of subtyping, (ii) the time required for subtype analysis, and (iii) the technical expertise required for many subtyping methods. While a variety of molecular subtyping methods are available for L. monocytogenes, many of them, including PFGE, which is often considered the gold standard for subtyping of L. monocytogenes (20,22), show the challenges and disadvantages detailed above. RAPD-PCR (72) continues to be a potentially attractive alternative for subtyping, as it allows for relatively easy, rapid, and inexpensive high-throughput subtyping of bacterial isolates.…”

Review. Dairy farm management and production practices associated with the presence of Listeria monocytogenes in raw milk and beef

“…In spite of its ubiquity, some subtypes of L. monocytogenes can be unique to specific niches such as specific foods (Fugett et al, 2007), and some can persist in particular processing environments for extended periods . The processing environ-ment is the main origin of contamination of processed food with Listeria.…”

“…Genomic macrorestriction based on rare-cutting endonucleases followed by pulsed-field gel electrophoresis (PFGE) remains as the gold standard test for routine molecular subtyping of most clinically important foodborne pathogens, including L. monocytogenes (Brosch et al, 1996;Graves & Swaminathan, 2001;Gerner-Smidt et al, 2006;Fugett et al, 2007;Ortiz et al, 2010). Analysis of data using bioinformatics software clusters isolates according to banding pattern similarity in a genetic distance tree known as a dendrogram (Nightingale, 2010) (Fig.…”