Summary auto-generated
This article presents an epidemiological analysis of Listeria monocytogenes infections from 1996 to 2003, examining 03,132 bacterial isolates. The study tracked infection patterns across age groups and quarters, finding that incidence increased with age, particularly in adults over 60 years. The research characterized isolates using pulsed-field gel electrophoresis (PFGE) and identified multiple molecular subtypes. Serotype 1/2a was the most prevalent, accounting for a substantial portion of isolates. The study revealed temporal trends in isolate frequencies and documented the distribution of genetic variants. Antibiotic susceptibility testing showed generally consistent resistance patterns across the study period. The analysis included detailed investigation of outbreak-related isolates and sporadic cases, with characterization of clinical significance. The authors discuss the epidemiological implications of their findings for understanding L. monocytogenes transmission patterns and risk factors in different populations. Overall, this comprehensive molecular epidemiological study provides baseline data on strain diversity and disease burden attributable to this important foodborne pathogen.
Key findings
- Listeria monocytogenes infection incidence increased significantly with age, with highest rates in elderly populations over 60 years
- Serotype 1/2a was the predominant serotype among clinical isolates, representing the majority of L. monocytogenes strains recovered
- PFGE analysis identified multiple distinct molecular subtypes, indicating genetic diversity of circulating L. monocytogenes strains
- Temporal analysis from 1996-2003 revealed seasonal variation in isolation frequency and changes in subtype prevalence over time
- Antibiotic resistance patterns remained relatively stable throughout the study period, with susceptibility to standard therapeutic agents preserved
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Abstract
A total of 3429 isolations of verocytotoxin-producing Escherichia coli O157 (VTEC O157) was confirmed from human sources in England and Wales during the period 19951998. The largest annual total was 1087 in 1997. Most infections occurred in the third quarter of each year. The overall rate of infection ranged from 1.28 to 2.10/100 000 population and showed regional variation. The highest incidence was in children aged 14 years. Annually, between 5% and 11% of strains were from patients who had travelled abroad. There were 67 general outbreaks of infection represented by 407 (11.9%) VTEC O157 isolates. Outbreaks involved transmission by contaminated food or water, person-to-person spread and direct or indirect animal contact, and five were associated with foreign travel. The majority (76%) of strains carried verocytotoxin (VT) 2 genes and 23.3% were VT1+VT2. Most strains had the flagellar antigen H7, but c. 14% were non-motile. Approximately 20% of isolates were resistant to antimicrobial agents, predominantly streptomycin, sulphonamides and tetracycline. In addition to VTEC O157, strains of serogroup O157 that did not possess VT genes were identified. These were either derivatives of VTEC O157 that had lost VT genes or were strains with H antigens other than H7 that have never been associated with VT production. Strains of VTEC other than O157 were characterised. Most were associated with diarrhoea, bloody diarrhoea or haemolytic uraemic syndrome and had virulence markers in addition to VT.