Effect of smoking on meningococcal carriage

Invasion by Neisseria meningitidis varies widely between clones and among nasopharyngeal mucosae derived from adult human hosts

Colonization of the human nasopharynx is a feature of some species of Neisseria, and is a prerequisite of invasive meningococcal disease. The likelihood of colonization by Neisseria meningitidis varies widely between humans, and very few develop invasive disease. Explants of nasal mucosa derived from adult patients with non-allergic nasal obstruction were infected experimentally with Neisseria spp. At intervals over 18 h incubation, washed explants were homogenized, and viable bacteria were counted. To estimate bacterial invasion of mucosa, explants were exposed to 0.25% sodium taurocholate for 30 s prior to homogenization. N. meningitidis was recovered from the mucosa and the organism invaded and replicated within the tissue, in contrast to N. lactamica and N. animalis (n=9, P<0.008). N. meningitidis isolates of clones ET-5, ET-37 and lineage III were recovered from and invaded tissue, but strains of clones A4, A:subgroup I, A:subgroup III and A:subgroup IV-1 did not invade (n=6). To measure host variation, survival of N. meningitidis within nasal mucosa of 40 different human donors was measured. Intra-class correlation of replicates was 0.97, but the coefficient of variation of recovered viable counts was 1335% after 4 h and 77% after 18 h incubation. It is concluded that the distinctive colonization and disease potential of Neisseria spp. may be partly a consequence of their ability to invade and survive within human nasopharyngeal mucosa, but that this is influenced greatly by genetic or environmental factors operating on the host mucosa. This is consistent with the unpredictable epidemiology of meningococcal disease.

Bench-to-bedside review: genetic influences on meningococcal disease

This review discusses the possible involvement of a variety of genetic polymorphisms on the course of meningococcal disease. It has been shown that several common genetic polymorphisms can either influence the susceptibility to meningococcal disease or can account for a higher mortality rate in patients. Gene polymorphisms concerning antibody receptors, lipopolysaccharide (LPS) binding receptors or proteins, innate complement proteins as well as cytokines and hemostatic proteins are described. The study of genetic polymorphisms might provide important insights in the pathogenesis of meningococcal disease and could make it possible to identify individuals who are at risk of either contracting or dying from meningococcal disease.

Development of natural immunity to Neisseria meningitidis

Although meningococcal disease is rare in industrialized nations, Neisseria meningitidis holds a prominent position amongst pediatric infections because of the dramatic clinical presentation of the disease, high mortality, epidemic potential and the recent disappearance of many other important infectious diseases in developed countries through improvements in public health and vaccination. The precise nature of natural immunity to meningococci remains unknown, although a complex interaction between the organism and nasopharyngeal mucosal barrier, innate immune mechanisms and acquired immunity is involved. Study of the mechanisms of natural immunity may provide the key to development of vaccines that can reduce the burden of disease in early childhood.

Update on Haemophilus influenzae serotype b and meningococcal vaccines

Use of conjugate Haemophilus influenzae type b (Hib) vaccines has resulted in the near elimination of Hib invasive disease among infants in the United States in only 10 years, which places this intervention among the most notable public health achievements of the past decade. This has radically altered our perception of the major causes of bacterial meningitis and invasive bacterial disease among children, increasing the prominence of meningococcal disease as an important cause of childhood and adult meningitis and leading researchers to apply the same conjugate technology to the development of improved vaccines for Neisseria meningitidis. Use of conjugated meningococcal vaccines against serogroups A, C, Y, and W-135 are expected to offer the possibility of better control of sporadic disease and outbreaks throughout developed and developing countries within the next 5 years.

Preventing meningococcal infection in college students

The incidence of invasive meningococcal disease in adolescents and young adults of high school and college age has recently increased in the United States. Recent studies indicate that certain groups of college students are at increased risk. This has led to the recent Advisory Committee Immunization Practices recommendation that college freshman dormitory residents be provided information about meningococcal infection and the benefits of vaccination. Future studies will need to focus on the potential vaccine prevention of the increased risk of meningococcal infection in persons of high school age, particularly as new conjugate meningococcal vaccines become available.

Changing carriage rate of Neisseria meningitidis among university students during the first week of term: cross sectional study

OBJECTIVE

To determine the rates of, and risk factors for, meningococcal carriage and acquisition among university students.

DESIGN

Repeated cross sectional study.

PARTICIPANTS

2,507 students in their first year at university.

MAIN OUTCOME MEASURES

Prevalence of carriage of meningococci and risk factors for carriage and acquisition of meningococci.

RESULTS

Carriage rates for meningoccoci increased rapidly in the first week of term from 6.9% on day 1, to 11.2% on day 2, to 19.0% on day 3, and to 23.1% on day 4. The average carriage rate during the first week of term in October among students living in catered halls was 13.9%. By November this had risen to 31.0% and in December it had reached 34. 2%. Independent associations for acquisition of meningococci in the autumn term were frequency of visits to a hall bar (5-7 visits: odds ratio 2.7, 95% confidence interval 1.5 to 4.8), active smoking (1.6, 1.0 to 2.6), being male (1.6, 1.2 to 2.2), visits to night clubs (1. 3, 1.0 to 1.6), and intimate kissing (1.4, 1.0 to 1.8). Lower rates of acquisition were found in female only halls (0.5, 0.3 to 0.9). The most commonly acquired meningococcal strain was C2a P1.5 (P1.2), which has been implicated in clusters of invasive meningococcal disease at other UK universities.

CONCLUSIONS

Carriage rates of meningococci among university students increase rapidly in the first week of term, with further increases during the term. The rapid rate of acquisition may explain the increased risk of invasive meningococcal disease and the timing of cases and outbreaks in university students.

Cigarette smoking and invasive pneumococcal disease. Active Bacterial Core Surveillance Team

BACKGROUND

Approximately half of otherwise healthy adults with invasive pneumococcal disease are cigarette smokers. We conducted a population-based case-control study to assess the importance of cigarette smoking and other factors as risk factors for pneumococcal infections.

METHODS

We identified immunocompetent patients who were 18 to 64 years old and who had invasive pneumococcal disease (as defined by the isolation of Streptococcus pneumoniae from a normally sterile site) by active surveillance of laboratories in metropolitan Atlanta, Baltimore, and Toronto. Telephone interviews were conducted with 228 patients and 301 control subjects who were reached by random-digit dialing.

RESULTS

Fifty-eight percent of the patients and 24 percent of the control subjects were current smokers. Invasive pneumococcal disease was associated with cigarette smoking (odds ratio, 4.1; 95 percent confidence interval, 2.4 to 7.3) and with passive smoking among nonsmokers (odds ratio, 2.5; 95 percent confidence interval, 1.2 to 5.1) after adjustment by logistic-regression analysis for age, study site, and independent risk factors such as male sex, black race, chronic illness, low level of education, and living with young children who were in day care. There were dose-response relations for the current number of cigarettes smoked per day, pack-years of smoking, and time since quitting. The adjusted population attributable risk was 51 percent for cigarette smoking, 17 percent for passive smoking, and 14 percent for chronic illness.

CONCLUSIONS

Cigarette smoking is the strongest independent risk factor for invasive pneumococcal disease among immunocompetent, nonelderly adults. Because of the high prevalence of smoking and the large population attributable risk, programs to reduce both smoking and exposure to environmental tobacco smoke have the potential to reduce the incidence of pneumococcal disease.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Meningococcal carriage in relation to an outbreak of invasive disease due to Neisseria meningitidis serogroup C in the Netherlands

BACKGROUND

a cross-sectional study on meningococcal carriage was performed in Putten, a small rural town in the Netherlands where an unusual high incidence of invasive meningococcal disease (IMD) due to Neisseria meningitidis C:2a:P1.5 occurred. The outbreak was controlled by mass vaccination of all inhabitants aged 2 to 20 years.

METHODS

meningococcal carriage was studied in three groups: (1) a systematic age-specific sample of 2-20 year olds who visited the immunization clinic in Putten (January 1998: n=411); (2) children and adolescents in the same age range recruited through a kindergarten and schools in Venlo, a town where the causative strain of IMD had not been encountered (February 1998; n=374); (3) all initial carriers in Putten and a sample of non-carriers in that town (March 1998: n=145). Oropharyngeal swabs were taken for the purpose of isolating N. menigitidis.

RESULTS

the prevalence of carriage was 12.4% in Putten and 18.2%, in Venlo, but the prevalence of group C meningococci was higher in Putten (1.7%) than Venlo (0.5%). N. meningitidis C:2a:P1.5 was isolated twice in Putten and not at all in Venlo. A second examination in Putten showed that 18 of the 22 repeatedly tested carriers were still carriers, and six new carriers were found among the 55 initial non-carriers. Of the two known carriers of C:2a:P1.5, one was still carrying the same strain, and the other did not participate in the second investigation. Carriage was associated with increasing family size, discotheque visits and visits to youth clubs and sports clubs. In contrast, visits to the swimming pool appeared to be related to a lower risk, as was recent antibiotic use.

CONCLUSION

the prevalence of carriage with the invasive strain C:2a:P1.5 was low in the population that experienced a community-wide outbreak recently: the specific strain was not found in the reference population. This indicates a relatively high risk of developing the invasive disease for those who become infected with such strains.

Maternal cigarette smoking and invasive meningococcal disease: a cohort study among young children in metropolitan Atlanta, 1989-1996

OBJECTIVES

This study assessed the association between maternal cigarette smoking during pregnancy and the risk of invasive meningococcal disease during early childhood.

METHODS

Using a retrospective cohort study design, cases from an active surveillance project monitoring all invasive meningococcal disease in the metropolitan Atlanta area from 1989 to 1995 were merged with linked birth and death certificate data files. Children who had not died or acquired meningococcal disease were assumed to be alive and free of the illness. The Cox proportional hazards analysis was used to assess the independent association between maternal smoking and meningococcal disease.

RESULTS

The crude rate of meningococcal disease was 5 times higher for children whose mothers smoked during pregnancy than for children whose mothers did not smoke (0.05% vs 0.01%). Multivariate analysis revealed that maternal smoking (risk ratio [RR] = 2.9; 95% confidence interval [CI] = 1.5, 5.7) and a mother's having fewer than 12 years of education (RR = 2.1; 95% CI = 1.0, 4.2) were independently associated with invasive meningococcal disease.

CONCLUSIONS

Maternal smoking, a likely surrogate for tobacco smoke exposure following delivery, appears to be a modifiable risk factor for sporadic meningococcal disease in young children.

The effect of cigarette smoke on adherence of respiratory pathogens to buccal epithelial cells

Smoking is associated with an increased risk of respiratory tract infection in adults. In children, exposure to cigarette smoke is a risk factor for respiratory tract infection and bacterial meningitis: Active smoking and passive exposure to cigarette smoke is also associated with carriage of some potentially pathogenic species of bacteria in both adults and children. The aims of the study were to determine the effect of active smoking on: (1) bacterial binding to epithelial cells; (2) expression of host cell antigens that act as receptors for some species; and (3) the effects of passive exposure to water-soluble components of cigarette smoke on bacterial binding. Flow cytometry was used to assess binding to buccal epithelial cells of the following species labelled with fluorescein isothiocyanate: Neisseria meningitidis, Neisseria lactamica, Streptococcus pneumoniae, Bordetella pertussis, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus. Flow cytometry was also used to assess expression of host cell antigens which have been identified as bacterial receptors. For each species, binding to cells of smokers was significantly higher than to cells of non-smokers; however, expression of host cell antigens was similar on epithelial cells of both groups. Non-dilute cigarette smoke extract reduced binding of bacteria to epithelial cells, but dilutions between 1 in 10 and 1 in 320 enhanced binding. We conclude that smokers might be more densely colonised by a variety of potentially pathogenic bacteria. The enhanced bacterial binding to epithelial cells of smokers is not related to enhanced expression of host cell antigens that can act as receptors for some species, but possibly to components in the smoke that alter charge or other properties of the epithelial cell surface. Passive coating of mucosal surfaces with components of cigarette smoke might enhance binding of potentially pathogenic bacteria.

Tobacco smoke as a risk factor for meningococcal disease

BACKGROUND

Since 1992 the US Pacific Northwest has experienced a substantial increase in the incidence of serogroup B meningococcal disease. The current meningococcal polysaccharide vaccine is poorly immunogenic in young children and does not protect against N. meningitidis serogroup B. Defining alternative approaches to the prevention and control of meningococcal disease is of considerable public health importance.

METHODS

We performed a case-control study comparing 129 patients in Oregon and southwest Washington with 274 age- and area-matched controls. We used conditional logistic regression analysis to determine which exposures remained associated with disease after adjusting for other risk factors and confounders and calculated the proportion of disease attributable to modifiable exposures.

RESULTS

After adjustment for all other significant exposures identified, having a mother who smokes was the strongest independent risk factor for invasive meningococcal disease in children < 18 years of age [odds ratio (OR), 3.8; 95% confidence interval (CI) 1.6 to 8.9)], with 37% (CI 15 to 65) of all cases in this age group potentially attributable to maternal smoking. Adult patients were more likely than controls to have a chronic underlying illness (OR 10.8, CI 2.7 to 43.3), passive tobacco smoke exposure (OR 2.5, CI 0.9 to 6.9) and to smoke tobacco (OR 2.4, CI 0.9 to 6.6). Dose-response effects were seen for passive smoke exposure and risk of disease in all age groups.

CONCLUSION

Tobacco smoke exposure independently increases the risk of developing meningococcal disease.

Meningococcal carriage: prevalence and sex-related risk factors

A retrospective analysis was done to examine whether sexual behaviour was associated with meningococcal carriage. Over the 4 month period from January to April 1994, 136 (27.4%) of the 496 consecutive new/re-registered genito-urinary medicine clinic attenders showed meningococcal carriage. Two (15.4%) of 13 homosexual men compared with 134 (27.7%) of 484 heterosexual men and women had evidence of meningococcal carriage. Relative risk (RR) of meningococcal carriage was 1.8 with > 10 lifetime partners and 1.2 with 3-10 partners (P < 0.007). RR with age group of 16-25 was 4.2 and for 26-35 it was 3.5. There was no relationship with meningococcal carriage and pharyngeal symptoms, sexual orientation, intravenous drug use, number of partners per month and orogenital sex. Further longitudinal studies may be of value in order to determine whether a high number of sexual partners is a marker for meningococcal carriage. In addition, further study may show whether there is an increased risk of meningococcal carriage and disease in those who live with meningococcal carriers.

Risk factors for Neisseria meningitidis carriage in a school during a community outbreak of meningococcal infection

As part of the management of an outbreak of meningococcal infection, 119 school contacts of an index case were swabbed for nasopharyngeal carriage. In a cohort study, risk factors for Neisseria meningitidis carriage were ascertained by means of a questionnaire, completed by 114 (96%) of those swabbed. Twenty five (21%) cultures were identified as "neisseria positive'; of which there were 18 (15%) Neisseria meningitidis isolates, 2 (2%) Neisseria lactamica isolates and 5 (4%) showed contaminants only. Two (2%) carriers were identified as harbouring the implicated outbreak strain. Single variable analysis identified six statistically significant risk factors for meningococcal carriage; increasing age, female sex, manual social class, personal smoking, regular attendance at a discotheque and rhinorrhoea. Multivariate analysis, using logistic regression modelling, found that of these six variables only age, sex and social class remained statistically significant when the other factors were controlled for. Nevertheless the role of smoking, social events and respiratory/viral infections in nasopharyngeal carriage, and other plausible mechanisms whereby age, sex and social class might exert their effect, could usefully be investigated further.

Meningococcal disease in Los Angeles County, California, and among men in the county jails

BACKGROUND

From January through March 1993, there were 54 cases of meningococcal disease in Los Angeles County, California, of which 9 occurred among men incarcerated in the county's jail system, which was 40 percent above capacity at the time. Several of the 45 patients from the community had had contact with men recently released from a county jail.

METHODS

We interviewed patients from the community (n=42) and neighborhood controls matched with the patients for age, race, and ethnic group (n=84) about potential exposures. We collected and cultured pharyngeal swabs for Neisseria meningitidis from men entering the central jail (n=162), men leaving the central jail (n=379), members of the jail staff (n=121), and patients at a community health center (n=214). Meningococcal isolates were identified by serotyping and multilocus enzyme electrophoresis.

RESULTS

The presence of community-acquired meningococcal disease was strongly associated with exposure to a person who had been in or worked at one of the county jails (multivariate matched odds ratio, 18.5; 95 percent confidence interval, 3.8 to 90.8; P<0.001). Pharyngeal carriage of meningococcus was significantly more frequent among men released from jail (19 percent) or entering jail (17 percent) than among workers at the jails (3 percent) or community residents seen at the clinic (1 percent). Among men entering jail, those who had previously been incarcerated were more often carriers than those who had not (21 percent vs. 7 percent, P=0.03). Of the isolates from nine community residents with serogroup C meningococcal disease, eight were the same strain as that isolated from the eight inmates with serogroup C disease.

CONCLUSIONS

In this outbreak of meningococcal disease in Los Angeles County, nearly half of community residents with the disease had contact with persons who had been in a county jail. The high rates of carriage among recidivists and released inmates suggests that the men became meningococcal carriers while in jail.

Meningococcal carriage, alcohol consumption, and campus bar patronage in a serogroup C meningococcal disease outbreak

Community outbreaks of serogroup C invasive meningococcal disease are increasing in North America (L. H. Harrison, JAMA 273:419-421, 1995; L. A. Jackson, A. Schuchat, M. W. Reeves, and J. D. Wenger, JAMA 273:382-389, 1995; C. M. Whalen, J. C. Hockin, A. Ryan, and F. Ashton, JAMA 273:390-394). In a recent 15-month university outbreak, disease was linked to patronage of a specific campus-area bar, suggesting that aspects of a campus bar environment might promote meningococcal transmission (P. B. Imrey, L. A. Jackson, P. H. Ludwinski, et al., Am. J. Epidemiol., in press). To investigate this hypothesis, oropharyngeal carriage results from samples taken from 867 university health service clients and 85 campus-area bar employees during the last 3 months of the outbreak were analyzed to determine factors correlated with carriage of any strain of Neisseria meningitidis. Results were validated with data from samples from 344 health center clients and 211 campus bar employees taken 8 months after the last outbreak case. Recent alcohol consumption (adjusted prevalence odds ratio = 3.8 for > 15 versus 0 drinks in last week [P = 0.0012]) and campus bar patronage (adjusted odds ratio = 1.9 for any versus no patronage in last 2 weeks [P = 0.0122]) showed separate effects in both univariate and multiple logistic regression analyses of data from the 1992 health center clients. Prevalence of meningococcal carriage among 1992 campus bar workers was 3.8 times that among health center clients; this prevalence ratio was roughly 2.5 after adjustment for alcohol consumption and bar patronage. Recent antibiotic usage was protective (prevalence odds ratio = 0.3) among health center clients and bar workers. These findings were generally supported by the validation samples. If alcohol consumption and other aspects of the campus bar environment facilitate transmission of and/or colonization by N. meningitidis, then the introduction of a highly pathogenic substrain into the campus bar environment may provide an unusual opportunity for invasive meningococcal disease within a campus community.

Molecular epidemiology of an outbreak of meningococcal disease in a university community

Over a 2-month period, five cases of serogroup C meningococcal disease occurred in Iowa City, Iowa. Two patients were unacquainted university students who had independently visited another university with endemic meningococcal disease. Isolates from these patients had DNA fingerprints identical to those of the isolates responsible for infections on the other campus. Three cases for which the patients' isolates had a different DNA fingerprint were linked to visiting a local tavern. To disrupt the outbreak, the University of Iowa offered free meningococcal vaccine to all students. This report demonstrates that outbreaks of meningococcal disease may be due to more than one circulating strain and illustrates the utility of pulsed-field gel electrophoresis in defining the molecular epidemiology of meningococcal infections.

Smoking, the environment and meningococcal disease: a case control study

This case control study investigated environmental factors in 74 confirmed cases of meningococcal disease (MD). In children aged under 5, passive smoking in the home (30 or more cigarettes daily) was associated with an odds ratio (OR) of 7.5 (95% confidence interval (CI) 1.46-38.66). ORs increased both with the numbers of cigarettes smoked and with the number of smokers in the household, suggesting a dose-response relationship. MD in this age group was also significantly associated with household overcrowding (more than 1.5 persons per room) (OR 6.0, 95% CI 1.10-32.8), with kisses on the mouth with 4 or more contacts in the previous 2 weeks (OR 2.46, 95% CI 1.09-5.56), with exposure to dust from plaster, brick or stone in the previous 2 weeks (OR 2.24, 95% CI 1.07-4.65); and with changes in residence (OR 3.0, 95% CI 1.0-8.99), marital arguments (OR 3.0, 95% CI 1.26-7.17) and legal disputes in the previous 6 months (OR 3.10, 95% CI 1.24-7.78). These associations were independent of social class. Public health measures to lower the prevalence of cigarette smoking by parents of young children may reduce the incidence of MD. The influence of building dust and stressful life events merits further investigation.

Asymptomatic carriage of Neisseria meningitidis in a randomly sampled population

To estimate the extent of meningococcal carriage in the Norwegian population and to investigate the relationship of several characteristics of the population to the carrier state, 1,500 individuals living in rural and small-town areas near Oslo were selected at random from the Norwegian National Population Registry. These persons were asked to complete a questionnaire and to volunteer for a bacteriological tonsillopharyngeal swab sampling. Sixty-three percent of the selected persons participated in the survey. Ninety-one (9.6%) of the volunteers harbored Neisseria meningitidis. The isolates were serogrouped, serotyped, tested for antibiotic resistance, and analyzed by multilocus enzyme electrophoresis. Eight (8.8%) of the 91 isolates represented clones of the two clone complexes that have been responsible for most of the systemic meningococal disease in Norway in the 1980s. Age between 15 and 24, male sex, and active and passive smoking were found to be independently associated with meningococcal carriage in logistic regression analyses. Working outside the home and having an occupation in transportation or industry also increased the risk for meningococcal carriage in individuals older than 17, when corrections for gender and smoking were made. Assuming that our sample is representative of the Norwegian population, we estimated that about 40,000 individuals in Norway are asymptomatic carriers of isolates with epidemic potential. Thus, carriage eradication among close contacts of persons with systemic disease is unlikely to have a significant impact on the overall epidemiological situation.

Parental smoking and carriage of Neisseria meningitidis among Greek schoolchildren

In December 1990 and January 1991, primary (320) and secondary (697) pupils in 2 areas of Athens were screened to determine the rate of carriage of Neisseria meningitidis and to determine if the genetic and environmental factors associated with carriage of meningococci in Greece were similar to those observed for northern European populations. In 1 area, socioeconomic indicators were significantly lower than in the other (p < 0.0005), but the isolation rates from pupils in the areas were similar, 5.3% and 6.3%. In contrast to studies in northwest Europe, carriage was not associated with lower socioeconomic conditions, sex, numbers of individuals per household, upper respiratory tract infection, or secretor status. By univariate analysis, carriage was associated with age (15-18 years) (p < 0.05) and mother's or other carer's smoking habits (p < 0.05)--but not father's smoking. Although the proportion of fathers who smoked was greater in the area where socioeconomic indicators were lower (61%) vs. (47%) (p < 0.0005), the proportions of women smokers were similar (33% vs. 38%). By multiple regression analysis, the only significant factors were age (p < 0.01) and carer's smoking (p < 0.05).

Factors enhancing adherence of toxigenic Staphylococcus aureus to epithelial cells and their possible role in sudden infant death syndrome

Toxigenic strains of Staphylococcus aureus have been suggested to play a role in sudden infant death syndrome (SIDS). In this study we examined two factors that might enhance binding of toxigenic staphylococci to epithelial cells of infants in the age range in which cot deaths are prevalent: expression of the Lewis(a) antigen and infection with respiratory syncytial virus (RSV). By flow cytometry we demonstrated that binding of three toxigenic strains of S. aureus to cells from nonsecretors was significantly greater than to cells of secretors. Pre-treatment of epithelial cells with monoclonal anti-Lewis(a) or anti-type-1 precursor significantly reduced bacterial binding (P < 0.01); however, attachment of the bacteria correlated only with the amount of Lewis(a) antigen detected on the cells (P < 0.01). HEp-2 cells infected with RSV bound significantly more bacteria than uninfected cells. These findings are discussed in context of factors previously associated with SIDS (mother's smoking, bottle feeding and the prone sleeping position) and a hypothesis proposed to explain some cases of SIDS.

Transmission of Neisseria meningitidis among asymptomatic military recruits and antibody analysis

Following the occurrence of a case of systemic meningococcal disease in a military camp in Norway, throat cultures and blood samples were collected from 33 healthy individuals belonging to the same troop as the patient (troop A) and from 29 individuals from a different troop (troop B) in the same camp. Serological studies showed that 91% of the recruits had bactericidal antibodies against the disease-causing strain. The isolates of Neisseria meningitidis recovered from the throat cultures were serogrouped, serotyped, and assigned to a clone on the basis of an analysis of the electrophoretic mobilities of 14 metabolic enzymes. None of the 23 carriers in troop A harboured the clone responsible for the case of disease, but 6 carried isolates of the same electrophoretic type, ET-7, which was not identified in any of the 19 carriers of troop B. Individuals in troop A were resampled 2 and 17 weeks after the meningococcal disease episode. Five of the carriers had acquired different clones and one of them changed clone twice in that period. Four of the six newly acquired clones had previously been identified in other carriers of troop A, demonstrating transmission of clones among individuals living and working in close proximity.

Factors affecting carriage of Neisseria meningitidis among Greek military recruits

Greek military recruits (993) were examined for carriage of meningococci during July 1990. Blood, saliva and throat swab specimens were obtained and each recruit answered a questionnaire providing information on age, education (a measure of socioeconomic level), place of residence, smoking habits and recent infections. The overall carriage rate was 25% but differed between the two camps: 79/432 (18%) in Camp A and 168/561 (30%) in Camp B (P less than 0.0005). In Camp B, there were significantly higher proportions of recruits who were non-secretors (P less than 0.0005), and/or heavy smokers (P less than 0.0005). They were also younger (less than 19 years old) (P less than 0.001), and on the whole had fewer years of education (P less than 0.0005). By univariate analysis, carriage was significantly associated with smoking. By multiple logistic regression analysis, carriage was associated with smoking (P less than 0.001), age (P less than 0.01) and the camp in which the recruits were based (P less than 0.01). Among recruits in Camp B, 15/38 (40%) of those with recent viral infections were carriers compared with 30% for the camp in general.

Pharyngeal carriage of Neisseria meningitidis and Neisseria lactamica in households with infants within areas with high and low incidences of meningococcal disease

In a household survey in the Faroe Islands, an isolated community with hyperendemic occurrence of meningococcal disease due to serogroup B 15, 1604 persons were examined for pharyngeal carriage of Neisseria meningitidis and N. lactamica. Two areas were chosen having experienced high (HIA), and two having experienced low incidences (LIA) of disease. Living in HIA compared with LIA was associated with higher risk of N. meningitidis B 15 carriage and lower risk of N. lactamica carriage, with odds ratios of 2.7 (95% confidence interval (CI) 1.4-5.1, P = 0.003) and 0.41 (95% CI 0.31-0.53, P less than 0.0001), respectively. In HIA the risk of N. meningitidis carriage was much lower in non-carriers than carriers of N. lactamica, with an odds ratio of 0.19 (95% CI 0.08-0.47, P = 0.0003); in LIA this association (odds ratio 0.51, P = 0.05) was much weaker. Children 0-14 years had substantially higher risk of being carriers of N. meningitidis group B 15 if the mothers were so, with an odds ratio of 11 (95% CI 4-29, P less than 0.0001).