Ribotyping as an additional molecular marker for studying Neisseria meningitidis serogroup B epidemic strains

Multiple-locus variable-number tandem repeat analysis of Neisseria meningitidis yields groupings similar to those obtained by multilocus sequence typing

We identified many variable-number tandem repeat (VNTR) loci in the genomes of Neisseria meningitidis serogroups A, B, and C and utilized a number of these loci to develop a multiple-locus variable-number tandem repeat analysis (MLVA). Eighty-five N. meningitidis serogroup B and C isolates obtained from Dutch patients with invasive meningococcal disease and seven reference strains were analyzed using MLVA and multilocus sequence typing (MLST). MLVA, based on eight VNTR loci with limited variability in the number of repeats, yielded clustering of the strains similar to that obtained by MLST, with congruence between both methods amounting to 69%. The ability to recognize clonal complexes makes MLVA a valuable high-throughput method to serve as a tool complementary to MLST. Four highly variable VNTR loci were used in a second assay to analyze N. meningitidis serogroup C strains collected during an outbreak of meningococcal disease in The Netherlands. Typing based on the latter VNTR loci enabled differentiation of isolates with identical MLST sequence types and grouped epidemiologically related strains.

Genetic diversity of Neisseria meningitidis strains isolated in Rio de Janeiro, Brazil, evaluated by multilocus enzyme electrophoresis

AIMS

To analyse Neisseria meningitidis isolates from meningococcal meningitis cases in Rio de Janeiro (Brazil) from 1990 to 1993 and 1999-2002, to determine the genetic and relatedness with hypervirulent and epidemic strains.

METHODS AND RESULTS

The isolates were analysed by multilocus enzyme electrophoresis (MEE) clustering into 83 electrophoretic types (ET). All isolates from 1999 to 2002, formed a cluster which included one strain of the ET-5 complex worldwide associated with epidemics.

CONCLUSIONS

The overall results suggested a panmictic structure probably because of recombination events. The observation of a separated cluster including isolates from 1999 to 2002 and an ET-5 complex strain, also suggested the introduction of strains genetically related with this hypervirulent complex in the State of Rio de Janeiro (Brazil) over the last 5 years.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of strains related to the ET-5 complex in several states of Brazil was already described elsewhere, but this is the first time it was reported in the State of Rio de Janeiro. Our findings reinforce the necessity to genetically determine the clones which should be considered to produce a national vaccine against meningococcal meningitis.

Serosubtypes and PorA types of Neisseria meningitidis serogroup B isolated in Brazil during 1997--1998: overview and implications for vaccine development

Meningococcal disease caused by N. meningitidis serogroup B (MenB) has been endemic in Brazil since 1997. In this study, we determined the prevalence of serosubtypes of MenB isolated in 10 Brazilian states and the Federal District during 1997 and 1998 and investigated the extent of PorA VR sequence variation among the most prevalent serosubtypes to evaluate the possible use of an outer membrane vesicle (OMV)-, PorA-based vaccine to prevent meningococcal disease in Brazil. During this period, a total of 8,932 cases of meningococcal disease were reported. Only 42% (n = 3,751) of the reported cases were laboratory confirmed, and about 60% (n = 2,255) of those were identified as MenB. Among 1,297 MenB strains selected for this study, the most prevalent serosubtypes were P1.19,15 (66%), P1.7,1 (11%), and P1.7,16 (4%). PorA VR typing showed that 91% of the P1.19,15 strains analyzed had VR1 and VR2 sequences identical to those of the prototype strain. No sequence variation was detected among the 40 strains representing all isolated MenB P1.7,16 strains in the three southern states, where this serosubtype accounts for 75% of the serosubtypes identified. Similarly, all P1.7,1 strains were identified by PorA typing as P1.7-1,1. Although further improvements in the reporting of cases and collection of strains in Brazil are needed, our data suggest that a trivalent OMV-based vaccine prepared with PorA types P1.19,15, P1.7-1,1, and P1.7,16 may be appropriate to control serogroup B meningococcal disease in most of the Brazilian states.

Genetic relationships among serogroup B: serotype 4 Neisseria meningitidis strains

We compared the results obtained by serotyping of PorB epitopes using an expanded panel of monoclonal antibodies (mAb) including mAb 7 and mAb 10, with results obtained by RFLP of rRNA genes (ribotyping). The purpose of this study was to assess the correlation between phenotypic- and genotypic- methods for typing N. meningitidis. The ribotypes obtained using ClaI or EcoRV endonucleases grouped the strains in seven and two different patterns, respectively. This additional characterization of PorB epitopes improved the correlation between these two methods of typing N. meningitidis.

Comparison of conventional ribotyping and PCR-RFLP ribotyping for the analysis of endemic strains of Neisseria meningitidis isolated in a local community over 7 years

Conventional ribotyping was compared with the PCR amplification of the intergenic spacer region between 16S and 23S rRNA genes (PCR-RFLP ribotyping) when applied to the subtyping of sporadic Neisseria meningitidis strains. Thirty isolates out of a total of 36 meningococcal disease cases, reported as having occurred in a particular community over a 7-year endemic period, were analyzed by each of the methods. Only ribotyping with three restriction enzymes (EcoRI, ClaI and XhoI) gave acceptable discriminatory power for short-term epidemiological purposes. We conclude that conventional ribotyping is a suitable method for typing sporadic meningococcal strains and that it cannot be replaced by the more straightforward PCR-RFLP ribotyping method.

Meningococcal disease caused by Neisseria meningitidis serogroup B serotype 4 in São Paulo, Brazil, 1990 to 1996

A large epidemic of serogroup B meningococcal disease (MD), has been occurring in greater São Paulo, Brazil, since 1988. A Cuban-produced vaccine, based on outer-membrane-protein (OMP) from serogroup B: serotype 4: serosubtype P1.15 (B:4:P1.15) Neisseria meningitidis, was given to about 2.4 million children aged from 3 months to 6 years during 1989 and 1990. The administration of vaccine had little or no measurable effects on this outbreak. In order to detect clonal changes that could explain the continued increase in the incidence of disease after the vaccination, we serotyped isolates recovered between 1990 and 1996 from 834 patients with systemic disease. Strains B:4:P1.15, which was detected in the area as early as 1977, has been the most prevalent phenotype since 1988. These strains are still prevalent in the area and were responsible for about 68% of 834 serogroup B cases in the last 7 years. We analyzed 438 (52%) of these strains by restriction fragment length polymorphism (RFLPs) of rRNA genes (ribotyping). The most frequent pattern obtained was referred to as Rb1 (68%). We concluded that the same clone of B:4:P1.15-Rb1 strains was the most prevalent strain and responsible for the continued increase of incidence of serogroup B MD cases in greater São Paulo during the last 7 years in spite of the vaccination trial.

Molecular subtyping of Neisseria meningitidis serogroup B: comparison of five methods

In order to compare methods for subtyping Neisseria meningitidis serogroup B isolates, 96 isolates obtained from various locations in the United States and northwestern Europe were subtyped by five methods: monoclonal antibody (MAb)-based serotyping and serosubtyping, DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE), multilocus enzyme electrophoresis (MEE), ribotyping, and PCR-restriction fragment length polymorphism of the internally transcribed spacer region of the rRNA operon (ITS PCR-RFLP). All N. meningitidis serogroup B isolates were typeable by PFGE, MEE, ribotyping, and ITS PCR-RFLP. Only 44.8% of the isolates were completely typeable (both serotype and serosubtype determination) by MAb-based serotyping and serosubtyping. 60.4% of the isolates could be serotyped but not serosubtyped, and 90.6% of the isolates could be either serotyped or serosubtyped. Simpson's discrimination indices of diversity for the methods were as follows: PFGE, 99.7%; MEE, 99.4%; ribotyping, 98.8%; MAb serotyping, 75.8%; MAb serotyping and/or serosubtyping 97.5%; and ITS PCR-RFLP, 84.2%. The high degree of diversity observed by PFGE, MEE, and ribotyping can be explained by the fact that isolates were collected from different geographic locations at various times. PFGE, MEE, and ribotyping showed greater discriminatory abilities than MAb-based serotyping and serosubtyping or ITS PCR-RFLP.

Genetic relationships of Corynebacterium diphtheriae strains isolated from a diphtheria case and carriers by restriction fragment length polymorphism of rRNA genes

In the present study we report the results of an analysis, based on ribotyping of Corynebacterium diphtheriae intermedius strains isolated from a 9 years old child with clinical diphtheria and his 5 contacts. Quantitative analysis of RFLPs of rRNA was used to determine relatedness of these 7 C.diphtheriae strains providing support data in the diphtheria epidemiology. We have also tested those strains for toxigenicity in vitro by using the Elek's gel diffusion method and in vivo by using cell culture method on cultured monkey kidney cell (VERO cells). The hybridization results revealed that the 5 C.diphtheriae strains isolated from contacts and one isolated from the clinical case (nose case strain) had identical RFLP patterns with all 4 restriction endonucleases used, ribotype B. The genetic distance from this ribotype and ribotype A (throat case strain), that we initially assumed to be responsible for the illness of the patient, was of 0.450 showing poor genetic correlation among these two ribotypes. We found no significant differences concerned to the toxin production by using the cell culture method. In conclusion, the use of RFLPs of rRNA gene was successful in detecting minor differences in closely related toxigenic C.diphtheriae intermedius strains and providing information about genetic relationships among them.

Genetic structure of Neisseria meningitidis serogroup C epidemic strains in south Brazil

In the present study we report the results of an analysis, based on serotyping, multilocus enzyme electrophoresis (MEE), and ribotyping of N. meningitidis serogroup C strains isolated from patients with meningococcal disease (MD) in Rio Grande do Sul (RS) and Santa Catarina (SC) States, Brazil, as the Center of Epidemiology Control of Ministry of Health detected an increasing of MD cases due to this serogroup in the last two years (1992-1993). We have demonstrated that the MD due to N.meningitidis serogroup C strains in RS and SC States occurring in the last 4 years were caused mainly by one clone of strains (ET 40), with isolates indistinguishable by serogroup, serotype, subtype and even by ribotyping. One small number of cases that were not due to an ET 40 strains, represent closely related clones that probably are new lineages generated from the ET 40 clone referred as ET 11A complex. We have also analyzed N.meningitidis serogroup C strains isolated in the greater São Paulo in 1976 as representative of the first post epidemic year in that region. The ribotyping method, as well as MEE, could provide useful information about the clonal characteristics of those isolates and also of strains isolated in south Brazil. The strains from 1976 have more similarity with the actual endemic than epidemic strains, by the ribotyping, sulfonamide sensitivity, and MEE results. In conclusion, serotyping with monoclonal antibodies (C:2b:P1.3), MEE (ET 11 and ET 11A complex), and ribotyping by using ClaI restriction enzyme (Rb2), were useful to characterize these epidemic strains of N.meningitidis related to the increased incidence of MD in different States of south Brazil. It is mostly probable that these N.meningitidis serogroup C strains have poor or no genetic correlation with 1971-1975 epidemic serogroup C strains. The genetic similarity of members of the ET 11 and ET 11A complex were confirmed by the ribotyping method by using three restriction endonucleases.