The distribution of serogroups and multilocus sequence types (STs) in collections of disease-associated and carried meningococci from the period 1991 to 2000 in three European countries (the Czech Republic, Greece, and Norway) was investigated. A total of 314 patient isolates and 353 isolates from asymptomatic carriers were characterized. The frequency distributions of serogroups and clone complexes differed among countries and between disease and carrier isolate collections. Highly significant differentiation was seen at each housekeeping locus. A marked positive association of serogroup C with disease was evidenced. The ST-11 complex was strongly positively associated with disease; associations for other clone complexes were weaker. The genetic diversity of the clone complexes differed. A single ST dominated the ST-11 clone complex, while the ST-41/44 complex exhibited greater levels of diversity. These data robustly demonstrated differences in the distribution of meningococcal genotypes in disease and carrier isolates and among countries. Further, they indicated that differences in genotype diversity and pathogenicity exist between meningococcal clone complexes.

The diversity of strains observed underscores the importance of studying the distribution of the vaccine antigen itself rather than relying on common epidemiological surrogates such as MLST.

To evaluate the role of seafoods in the epidemiology of human listeriosis and the role of the processing environment as a source of Listeria monocytogenes in seafood products, 305 L. monocytogenes isolates were characterized by multilocus enzyme electrophoresis using 21 genetic loci and restriction enzyme analysis of total DNA. Forty-four isolates were recovered from patients in Norway; 93 were isolated from seafoods, seafood-processing environments, and seawater from 55 different producers; and the remaining 168 isolates originated from six seafood-processing plants and one transport terminal examined in detail for L. monocytogenes. The patient isolates fell into 11 electrophoretic types, with four of them being responsible for 77% of the listeriosis cases in 1992 to 1996. Isolates from Norwegian seafoods and processing environments showed great genetic diversity, indicating that seafoods and seafood-processing environments do not offer a niche for specific L. monocytogenes strains. On the other hand, isolates from individual processing plants were genetically more homogenous, showing that plants are likely to be colonized with specific subclones of L. monocytogenes. The isolation of identical subclones of L. monocytogenes from both human patients and seafoods, including ready-to-eat products, suggests that such products may have been possible sources for listeriosis cases in Norway.

Aims: To investigate the prevalence of Listeria monocytogenes in poultry products, and to elucidate whether poultry products may be linked to listeriosis cases. A further goal was to identify contamination routes for L. monocytogenes to broiler carcasses. Methods and Results: Poultry products (385 samples) were screened for L. monocytogenes. The recovered isolates and 19 patient isolates were characterized by multilocus enzyme electrophoresis and restriction enzyme analysis. The poultry isolates showed great genetic diversity, but no identical subclones were identified from poultry sources and patients. One slaughterhouse was examined in detail during a 16-month period. The contamination rates increased along the processing line, and one subclone was found during the whole period. Only low prevalence of the bacteria was revealed from broiler faeces. Conclusions: The prevalence of L. monocytogenes in poultry products was high, but no listeriosis cases was linked to poultry products. Broilers seem to be contaminated during the slaughter process, and specific strains may persist in the processing environment. Broiler faeces does not seem to be an important source of L. monocytogenes in poultry products. Significance and Impact of the Study: Preventive measures to avoid contamination of poultry products by L. monocytogenes must be taken in the processing plants.