Carried meningococci in the Czech Republic: a diverse recombining population

Population and evolutionary analyses of pathogenic bacteria are frequently hindered by sampling strategies that concentrate on isolates from patients with invasive disease. This is especially so for the gram-negative diplococcus Neisseria meningitidis, a cause of septicemia and meningitis worldwide. Meningococcal isolate collections almost exclusively comprise organisms originating from patients with invasive meningococcal disease, although this bacterium is a commensal inhabitant of the human nasopharynx and very rarely causes pathological effects. In the present study, molecular biology-based techniques were used to establish the genetic relationships of 156 meningococci isolated from healthy young adults in the Czech Republic during 1993. None of the individuals sampled had known links to patients with invasive disease. Multilocus sequence typing (MLST) showed that the bacterial population was highly diverse, comprising 71 different sequence types (STs) which were assigned to 34 distinct complexes or lineages. Three previously identified hyperinvasive lineages were present: 26 isolates (17%) belonged to the ST-41 complex (lineage 3); 4 (2.6%) belonged to the ST-11 (electrophoretic type [ET-37]) complex, and 1 (0.6%) belonged to the ST-32 (ET-5) complex. The data were consistent with the view that most nucleotide sequence diversity resulted from the reassortment of alleles by horizontal genetic exchange.     

PorA variable regions of Neisseria meningitidis

Subtypes, defined by variation in the outer membrane protein PorA, are an integral part of the characterization scheme for Neisseria meningitidis. Identification of these variants remains important as the PorA protein is a major immunogenic component of several meningococcal vaccines under development, and characteristics of PorA are used to provide detailed epidemiologic information. Historically, serosubtypes have been defined by reactivity with a set of monoclonal antibodies. However, nucleotide sequence analyses of porA genes have established that the panel of serosubtyping monoclonal antibodies is not exhaustive, and many porA variants cannot be detected. In addition, the nomenclature system used to define subtypes is inadequate. We examined all available nucleotide sequences of the porA VR1 and VR2 regions to identify and define subtype families. A revised nomenclature scheme, compatible with the previous serologic nomenclature scheme, was devised. A Web-accessible database describing this nomenclature and its relationship to previous schemes was established (available from: http://neisseria.org/nm/typing/pora).     

Real-Time Genomic Epidemiological Evaluation of Human Campylobacter Isolates by Use of Whole-Genome Multilocus Sequence Typing

Sequence-based typing is essential for understanding the epidemiology of Campylobacter infections, a major worldwide cause of bacterial gastroenteritis. We demonstrate the practical and rapid exploitation of whole-genome sequencing to provide routine definitive characterization of Campylobacter jejuni and Campylobacter coli for clinical and public health purposes. Short-read data from 384 Campylobacter clinical isolates collected over 4 months in Oxford, United Kingdom, were assembled de novo. Contigs were deposited at the pubMLST.org/campylobacter website and automatically annotated for 1,667 loci. Typing and phylogenetic information was extracted and comparative analyses were performed for various subsets of loci, up to the level of the whole genome, using the Genome Comparator and Neighbor-net algorithms. The assembled sequences (for 379 isolates) were diverse and resembled collections from previous studies of human campylobacteriosis. Small subsets of very closely related isolates originated mainly from repeated sampling from the same patients and, in one case, likely laboratory contamination. Much of the within-patient variation occurred in phase-variable genes. Clinically and epidemiologically informative data can be extracted from whole-genome sequence data in real time with straightforward, publicly available tools. These analyses are highly scalable, are transparent, do not require closely related genome reference sequences, and provide improved resolution (i) among Campylobacter clonal complexes and (ii) between very closely related isolates. Additionally, these analyses rapidly differentiated unrelated isolates, allowing the detection of single-strain clusters. The approach is widely applicable to analyses of human bacterial pathogens in real time in clinical laboratories, with little specialist training required.     

Diversity in pathogenicity can cause outbreaks of meningococcal disease

Neisseria meningitidis, the meningococcus, is a major cause of bacterial meningitis and septicemia worldwide. Infection in most cases leads to asymptomatic carriage and only rarely to disease. Meningococcal disease often occurs in outbreaks, which are both sporadic and highly unpredictable. The occurrence of disease outbreaks in a host population in which the etiological agent is widely carried is not well understood. A potential explanation lies in the fact that meningococci are diverse with respect to disease-causing potential. We formulated a stochastic mathematical model to investigate whether diversity of the bacterial population is related to outbreaks of meningococcal disease. In the model, strains that occasionally cause the disease appear repeatedly in a population dominated by a nonpathogenic strain. When the pathogenicity, i.e., the disease-causing potential, of the pathogenic lineage was low, the model shows distinct outbreaks, the size distribution of the outbreaks follows a power law, and the ratio of the variance to the mean number of cases is high. Analysis of notification data of meningococcal disease showed that the ratio of the variance to the mean was significantly higher for meningococcal diseases than for other bacterial invasive diseases. This result lends support to the hypothesis that outbreaks of meningococcal disease are caused by diversity in the pathogenicity of meningococcal strains.     

Predictive value of interleukin 1 gene polymorphisms for surgery

OBJECTIVES: To determine the influence of interleukin 1alpha (IL1alpha), IL1beta, and IL1 receptor antagonist gene polymorphisms on disease outcome as assessed by the need for major joint surgery within 15 years of diagnosis. PATIENTS AND METHODS: 50 patients with rheumatoid arthritis (RA) who required major joint surgery (hip, knee, or shoulder arthroplasty) within a 15 year period of disease diagnosis and 50 patients with RA with disease duration greater than 15 years and no major surgery were recruited together with 66 normal west of Scotland controls. Genomic DNA and polymerase chain reaction were used to determine polymorphisms in the genes for IL1alpha, IL1beta, and IL1 receptor antagonist. For all patients with RA recruited to the study, HLA-DR beta1 gene status was recorded as was the erythrocyte sedimentation rate (ESR) at the first ever clinic visit. RESULTS: No difference in the allele frequencies or genotypes of the IL1alpha and IL1 receptor antagonist gene polymorphisms was found between the controls and patients with RA, with or without previous surgery. IL1beta allele 2 was overrepresented in patients with RA who had undergone surgery compared with patients who had not (40% v 27%, chi(2)=4, 1df, p=0.04). ESR at the first ever clinic visit was significantly higher in those carrying allele 2 (36 mm/1st h v 22 mm/1st h, p=0.04). When patients, with or without previous surgery, who did not carry two disease associated HLA-DR beta1 alleles were compared, an increase in allele 2 was observed in the surgery cohort (42% v 25%, chi(2)=4.8, 1df, p=0.03). CONCLUSIONS: Patients who require major joint surgery were found to carry the IL1beta allele 2 more often than expected. Patients with this allele also had a higher initial ESR. This may be useful in predicting early surgery in patients who do not carry two disease associated HLA-DR beta1 alleles. Although these findings are interesting, further functional and epidemiological studies to confirm these observations are required.     

Molecular characterization of Campylobacter jejuni clones: a basis for epidemiologic investigation

A total of 814 isolates of the foodborne pathogen Campylobacter jejuni were characterized by multilocus sequence typing (MLST) and analysis of the variation of two cell-surface components: the heat-stable (HS) serotyping antigen and the flagella protein FlaA short variable region. We identified 379 combinations of the MLST loci (sequence types) and 215 combinations of the cell-surface components among these isolates, which had been obtained from human disease, animals, food, and the environment. Despite this diversity, 748 (92%) of the isolates belonged to one of 17 clonal complexes, 6 of which contained many (318, 63%) of the human disease isolates. Several clonal complexes exhibited associations with isolation source or particular cell-surface components; however, the latter were poorly predictive of clonal complex. These data demonstrate that the clonal complex, as defined by MLST, is an epidemiologically relevant unit for both long and short-term investigations of C. jejuni epidemiology.     

Long-term effects of respiratory syncytial virus (RSV) bronchiolitis in infants and young children: a quantitative review

One of the major questions regarding long-term side effects of bronchiolitis by respiratory syncytial virus (RSV) is whether or not it induces asthma in later life. In this quantitative review, the data of 10 controlled studies are analysed. METHODS: Follow-up studies of RSV bronchiolitis published between January 1978 and December 1998 were identified through a MEDLINE search. Studies were selected if (i) postnatal age at the time of the initial illness was below 12 mo, (ii) all children were hospitalized for RSV bronchiolitis, (iii) the diagnosis RSV was virologically confirmed in all cases, and (iv) a control group was used. RESULTS: Six studies met all selection criteria. Up to 5 y of follow-up after RSV bronchiolitis in infancy, 40% of children reported wheezing as compared to only 11% in the control group (p <0.001). Between 5 and 10 y of follow-up 22% of the bronchiolitis group reported wheezing against 10% of the control group (p = 0.19). The incidence of recurrent wheezing as defined by three or more wheezing episodes also decreased with increasing years of follow-up: at 5 or more years of follow-up the difference between the RSV group and the control group was no longer significant. Furthermore, the presence of either a personal and/or a family history of either atopy and/or asthma did not differ between the two groups. CONCLUSIONS: Wheezing is common after RSV bronchiolitis in infancy. It may persist for > or = 5 y of follow-up. However, no significant difference between the RSV bronchiolitis and the control group was observed regarding recurrent wheezing by 5 y of follow-up. No significant difference between the RSV bronchiolitis and the control group were found regarding a personal history of atopy, a family history of atopy and/or asthma. Therefore it seems unlikely that RSV bronchiolitis is a cause of atopic asthma in later life.     

Does social disadvantage contribute to the excess mortality in rheumatoid arthritis patients?

BACKGROUND: Socioeconomic deprivation is associated with increased mortality from cardiovascular causes and malignancy. The influence of disadvantage in patients with rheumatoid arthritis (RA), who are known to have premature mortality, has not been ascertained. AIM: To assess the relation between the level of patient deprivation and mortality in RA patients. METHODS: 200 RA patients, enrolled in a study comparing sulfasalazine and penicillamine in 1984-85, have been followed up prospectively for 12 years. Subjects were categorised into Carstairs groups with deprivation scores ranging from 1 (most affluent) to 7 (most deprived). Information about deaths was obtained from the Registrar General in Scotland, death certificates and GP/hospital records. RESULTS: There were more RA patients in the deprived areas then expected compared with the West of Scotland and England and Wales. Some 47.5% of the RA patients had died by 12 years-the majority of cardiorespiratory causes or malignancy. There were no differences in the median age or disease duration in the various Carstairs groups at study entry, but the percentage of deaths was higher in the more deprived groups after 12 years (36% dead in most affluent area compared with 61% in the most deprived, that is, in groups 6 and 7). CONCLUSION: In patients with RA increasing deprivation was associated with premature mortality. If confirmed elsewhere these findings have implications for rheumatological management strategies, for researchers involved in collaborative studies of patients from different socioeconomic backgrounds and for resource allocation.