Molecular epidemiology of recent United Kingdom isolates of Neisseria meningitidis serogroup C

Evaluation of pulsed-field gel electrophoresis in epidemiological investigations of meningococcal disease outbreaks caused by Neisseria meningitidis serogroup C

Since 1990, the frequency of Neisseria meningitidis serogroup C (NMSC) outbreaks in the United States has increased. Based on multilocus enzyme electrophoresis (MEE), the current molecular subtyping standard, most of the NMSC outbreaks have been caused by isolates of several closely related electrophoretic types (ETs) within the ET-37 complex. We chose 66 isolates from four well-described NMSC outbreaks that occurred in the United States from 1993 to 1995 to evaluate the potential of pulsed-field gel electrophoresis (PFGE) to identify outbreak-related isolates specific for each of the four outbreaks and to differentiate between them and 50 sporadic isolates collected during the outbreak investigations or through active laboratory-based surveillance from 1989 to 1996. We tested all isolates collected during the outbreak investigations by four other molecular subtyping methods: MEE, ribotyping (ClaI), random amplified polymorphic DNA assay (two primers), and serotyping and serosubtyping. Among the 116 isolates, we observed 11 clusters of 39 NheI PFGE patterns. Excellent correlation between the PFGE and the epidemiological data was observed, with an overall sensitivity of 85% and specificity of 71% at the 95% pattern relatedness breakpoint using either 1.5 or 1.0% tolerance. For all four analyzed outbreaks, PFGE would have given public health officials additional support in declaring an outbreak and making appropriate public health decisions.

Molecular epidemiology of recent belgian isolates of Neisseria meningitidis serogroup B

In Belgium an increase in the incidence of meningococcal disease has been noted since the early 1990s. Four hundred twenty clinical strains isolated during the period from 1990 to 1995, along with a set of 30 European reference strains, and 20 Dutch isolates were examined by random-primer and repetitive-motif-based PCR. A subset was investigated by multilocus enzyme electrophoresis and pulsed-field gel electrophoresis. The data were compared with results obtained by serotyping (M. Van Looveren, F. Carion, P. Vandamme, and H. Goossens, Clin. Microbiol. Infect. 4:224-228, 1998). Both phenotypic and molecular epidemiological data suggest that the lineage III of Neisseria meningitidis, first encountered in The Netherlands in about 1980, has been introduced in Belgium. The epidemic clone, as defined by oligonucleotide D8635-primed PCR, encompasses mainly phenotypes B:4:P1.4 and B:nontypeable:P1.4, but strains with several other phenotypes were also encountered. Therefore, serotyping alone would underestimate the prevalence of the epidemic clone.

Neisseria meningitidis W135 pneumonia with sepicaemia in a nonogenarian

Neisseria meningitidis infection is generally considered a disease of children or young adults, classically presenting as meningitis or sepicaemia. This infection is rare but recognised in the elderly. We present the case of a nonogenarian with meningococcal pneumonia and sinusitis with bacteraemia caused by N.meningitidis W135 a rare serogroup. We therefore thought this unusual situation of interest and worthwhile reporting.

Increasing incidence of meningococcal disease in Spain associated with a new variant of serogroup C

Serogroup B has been the main cause of meningococcal disease in Spain since at least 1979, but in recent years an increase in the prevalence of infection due to serogroup C meningococci has been detected. In 1996, for the first time, most cases of meningococcal disease were caused by serogroup C strains. The sero/subtype of all serogroup C meningococci received from 1993 to June 1996 was determined, and the results showed that C:2b:P1.2,5, the most common phenotype in 1995 and 1996 (63% and 65%, respectively), represented only 4.8% of strains in 1993. The C:2b: P1.2,5 epidemic strains appear to be responsible for the high prevalence of serogroup C in Spain. One hundred fifty-one randomly selected serogroup C strains were analyzed by multilocus enzyme electrophoresis, ribotyping, and pulsed-field gel electrophoresis. Pulsed-field gel electrophoresis provided the most accurate information: more than 80% of the C:2b:P1.2,5 and C:2b:P1.2 isolates exhibited one of two very closely related profiles, while most of the C:2b:NST and C:2b:P1.5 strains had a pattern located at a genetic distance of 0.24 from those two profiles. The results show that C:2b:P1.2,5 strains represent a subclone or a genetic variant of the previously identified Spanish epidemic clone C:2b:non-subtypable strains.

The use of capillary electrophoresis for point-mutation screening

Advances in capillary electrophoresis technology over the past three years have been rapid. Capillary electrophoresis offers high-throughput, high-resolution, automatic operation and on-line detection with automatic data acquisition, and this has stimulated its application to the analysis of DNA mutations. Many different PCR-based DNA-mutation assays have been developed for unknown and known mutations. This article compares conventional PCR-based mutation-detection assays with the methods developed for use with capillary electrophoresis. Future trends for mutation detection using capillary electrophoresis are also assessed, with a special emphasis on totally integrated, microchip capillary-electrophoresis-based mutation-detection systems.

Rapid pulsed-field gel electrophoresis protocol for typing of Escherichia coli O157:H7 and other gram-negative organisms in 1 day

Genomic DNA patterns generated by pulsed-field gel electrophoresis are highly specific for different strains of an organism and have significant value in epidemiologic investigations of infectious-disease outbreaks. Unfortunately, time-consuming and tedious specimen processing is an inherent problem which limits the use of this powerful technology as a real-time epidemic investigational tool. Here, I describe a rapid method to improve the response time and provide specific bacterial strain identification for the typing of Escherichia coli O157:H7 and other gram-negative organisms in a single day.

Endemic meningococcal disease in Cerdanyola, Spain, 1987--93: molecular epidemiology of the isolates of Neisseria meningitidis

OBJECTIVE: To establish the relationships between 30 Neisseria meningitidis strains isolated in Cerdanyola (Spain) from 30 out of 36 sporadic cases of meningococcal disease (MD) during 1987--93 and their spread in this population by multilocus enzyme electrophoresis (MEE) and by pulsed-field gel electrophoresis (PFGE), and to evaluate the usefulness of PFGE versus serologic typing methods and MEE as an alternative epidemiologic marker to study meningococcal infection. METHODS: Serotyping, electrophoretic mobility of seven isoenzymes determined by MEE and chromosomal DNA macrorestriction with NheI resolved by PFGE were analyzed. RESULTS: Of these 30 strains, 25 were serogroup B and the remaining five were serogroup C, with the 4:P1.15 and the 2b:NT as the most common antigenic phenotypes, respectively. There were 13 electrophoretic types (ETs) by MEE, with 14 isolates showing an identical ET, 8. Sixteen pulse types (PTs) were generated by PFGE. The 14 ET 8 isolates were clustered into six PTs, A1, A2, A4, A5, A6 and A8. However, by combining both methods, 19 genetically distinct groups were obtained. Eleven of these groups (20 serogroup B strains) and two of these (four serogroup C strains) were genetically related. CONCLUSIONS: We conclude that, according to the clonal population structure, these 30 N. meningitidis strains are heterogeneous although a great number are related. Moreover, PFGE is a useful method to establish clonal structure in N. meningitidis strains under endemic conditions. Finer discrimination of these strains was achieved by combining both MEE and PFGE methods.

Epidemiological evaluation of Neisseria meningitidis serogroup B by pulsed-field gel electrophoresis

Genomic DNA from 25 strains of serogroup B Neisseria meningitidis was subjected to pulsed-field gel electrophoresis (PFGE) after digestion with Spe I. N. meningitidis genomic DNA displayed considerable diversity. The diversity we observed among these strains was stable and included isolates from an outbreak that were phenotypically identical. This confirms the value of macrorestriction profiling and PFGE in providing epidemiologically stable strain markers for typing meningococci.