Related Experiment Videos
Differentiation of Listeria monocytogenes isolates by using plasmid profiling and multilocus enzyme electrophoresis
J Kolstad1, D A Caugant, L M Rørvik
1Department of Food Hygiene, Norwegian College of Veterinary Medicine, Oslo.
Abstract:
Three hundred and seven Listeria monocytogenes isolates from various origins (clinical sources, raw chicken, seafoods, dairy and meat products and processing environments) were screened for plasmids. The overall frequency of L. monocytogenes isolates containing plasmids was 77%. The highest percentages of plasmid positive isolates were found from meat (89%), chicken (81%) and dairy products (64%), while clinical isolates had the lowest plasmid percentage (28%). Seven sizes of plasmids (21, 24, 27, 35, 40, 47 and 52 MDa) were distinguished. All sizes were represented in the meat isolates, clinical isolates contained only two of the plasmid sizes, while several different sizes of plasmids were found in the isolates from other origins. Plasmid profiling divided the isolates into ten plasmid pattern types. Multilocus enzyme electrophoresis of 75 isolates demonstrated 12 distinctive multilocus genotypes (ETs) which clustered into two groups: cluster A including serotype 1 and 4 isolates, and isolates not typable by Difco antisera serotype 1 and 4, and cluster B containing only serotype 1 isolates. No relationship between ETs and plasmid profiles could be demonstrated.
Insights
Most Listeria monocytogenes isolates carry plasmids, particularly those from meat and chicken. Plasmid presence and size varied by origin, but no link was found between plasmid profiles and genetic types.
Area of Science:
- Microbiology
- Molecular Biology
- Food Safety
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- Plasmids are extrachromosomal DNA elements that can influence bacterial traits, including virulence and antibiotic resistance.
- Understanding plasmid dynamics in L. monocytogenes is crucial for food safety and public health.
Purpose of the Study:
- To investigate the prevalence and characteristics of plasmids in Listeria monocytogenes isolates from diverse sources.
- To determine the relationship between plasmid profiles and multilocus genotypes of L. monocytogenes.
Main Methods:
- Screening of 307 L. monocytogenes isolates for plasmid presence using plasmid profiling.
- Characterization of plasmid sizes (21-52 MDa) and patterns.
- Multilocus enzyme electrophoresis (MEE) was performed on 75 isolates to determine genetic diversity (12 electrophoretic types, ETs).
Main Results:
- A high overall plasmid frequency (77%) was observed in L. monocytogenes isolates.
- Meat (89%), chicken (81%), and dairy (64%) isolates showed higher plasmid prevalence than clinical isolates (28%).
- Ten distinct plasmid profiles were identified, with varying plasmid sizes across different isolate origins. No correlation was found between plasmid profiles and ETs.
Conclusions:
- Plasmids are common in L. monocytogenes, with significant variation in prevalence and size depending on the source.
- The genetic diversity of L. monocytogenes, assessed by MEE, does not appear to be directly related to plasmid carriage or profiles.
- Further research is needed to understand the functional role of these plasmids in L. monocytogenes adaptation and pathogenicity.