Meningococcal disease at the University of Southampton: outbreak investigation

Evaluating the effect of targeted strategies as control tools for hypervirulent meningococcal C outbreaks: a case study from Tuscany, Italy, 2015 to 2016

BackgroundMeningococcus (Neisseria meningitidis) is the causative bacteria of invasive meningococcal disease (IMD), a major cause of meningitis and sepsis. In 2015-16, an outbreak caused by serogroup C meningococci (MenC), belonging to the hyperinvasive strain ST-11(cc-11), resulted in 62 IMD cases in the region of Tuscany, Italy.AimWe aimed to estimate the key outbreak parameters and assess the impact of interventions used in the outbreak response.MethodsWe developed a susceptible-carrier-susceptible individual-based model of MenC transmission, accounting for transmission in households, schools, discos/clubs and the general community, which was informed by detailed data on the 2015-16 outbreak (derived from epidemiological investigations) and on the implemented control measures.ResultsThe outbreak reproduction number (Re) was 1.35 (95% prediction interval: 1.13-1.47) and the IMD probability was 4.6 for every 1,000 new MenC carriage episodes (95% confidence interval: 1.8-12.2). The interventions, i.e. chemoprophylaxis and vaccination of close contacts of IMD cases as well as age-targeted vaccination, were effective in reducing Re and ending the outbreak. Case-based interventions (including ring vaccination) alone would have been insufficient to achieve outbreak control. The definition of age groups to prioritise vaccination had a critical impact on the effectiveness and efficiency of control measures.ConclusionsOur findings suggest that there are no effective alternatives to widespread reactive vaccination during outbreaks of highly transmissible MenC strains. Age-targeted campaigns can increase the effectiveness of vaccination campaigns. These results can be instrumental to define effective guidelines for the control of future meningococcal outbreaks caused by hypervirulent strains.

Meningococcal Disease Outbreaks: A Moving Target and a Case for Routine Preventative Vaccination

Outbreaks of invasive meningococcal disease (IMD) are unpredictable, can be sudden and have devastating consequences. We conducted a non-systematic review of the literature in PubMed (1997-2020) to assess outbreak response strategies and the impact of vaccine interventions. Since 1997, IMD outbreaks due to serogroups A, B, C, W, Y and X have occurred globally. Reactive emergency mass vaccination campaigns have encompassed single institutions (schools, universities) through to whole sections of the population at regional/national levels (e.g. serogroup B outbreaks in Saguenay-Lac-Saint-Jean region, Canada and New Zealand). Emergency vaccination responses to IMD outbreaks consistently incurred substantial costs (expenditure on vaccine supplies, personnel costs and interruption of other programmes). Impediments included the limited pace of transmission of information to parents/communities/healthcare workers; issues around collection of informed consents; poor vaccine uptake by older adolescents/young adults, often a target age group; issues of reimbursement, particularly in the USA; and difficulties in swift supply of large quantities of vaccines. For serogroup B outbreaks, the need for two doses was a significant issue that contributed substantially to costs, delayed onset of protection and non-compliance with dose 2. Real-world descriptions of outbreak control strategies and the associated challenges systematically show that reactive outbreak management is administratively, logistically and financially costly, and that its impact can be difficult to measure. In view of the unpredictability, fast pace and potential lethality of outbreak-associated IMD, prevention through routine vaccination appears the most effective mitigation tool. Highly effective vaccines covering five of six disease-causing serogroups are available. Preparedness through routine vaccination programmes will enhance the speed and effectiveness of outbreak responses, should they be needed (ready access to vaccines and need for a single booster dose rather than a primary series).

Factor H binding protein (fHbp)-mediated differential complement resistance of a serogroup C Neisseria meningitidis isolate from cerebrospinal fluid of a patient with invasive meningococcal disease

During an outbreak of invasive meningococcal disease (IMD) at the University of Southampton, UK, in 1997, two Neisseria meningitidis serogroup C isolates were retrieved from a student ('Case'), who died of IMD, and a close contact ('Carrier') who, after mouth-to-mouth resuscitation on the deceased, did not contract the disease. Genomic comparison of the isolates demonstrated extensive nucleotide sequence identity, with differences identified in eight genes. Here, comparative proteomics was used to measure differential protein expression between the isolates and investigate whether the differences contributed to the clinical outcomes. A total of six proteins were differentially expressed: four proteins (methylcitrate synthase, PrpC; hypothetical integral membrane protein, Imp; fructose-1,6-bisphosphate aldolase, Fba; aldehyde dehydrogenase A, AldA) were upregulated in the Case isolate, while one protein (Type IV pilus-associated protein, PilC2) was downregulated. Peptides for factor H binding protein (fHbp), a major virulence factor and antigenic protein, were only detected in the Case, with a single base deletion (ΔT366) in the Carrier fHbp causing lack of its expression. Expression of fHbp resulted in an increased resistance of the Case isolate to complement-mediated killing in serum. Complementation of fHbp expression in the Carrier increased its serum resistance by approximately 8-fold. Moreover, a higher serum bactericidal antibody titre was seen for the Case isolate when using sera from mice immunized with Bexsero (GlaxoSmithKline), a vaccine containing fHbp as an antigenic component. This study highlights the role of fHbp in the differential complement resistance of the Case and the Carrier isolates. Expression of fHbp in the Case resulted in its increased survival in serum, possibly leading to active proliferation of the bacteria in blood and death of the student through IMD. Moreover, enhanced killing of the Case isolate by sera raised against an fHbp-containing vaccine, Bexsero, underlines the role and importance of fHbp in infection and immunity.

High COVID-19 transmission potential associated with re-opening universities can be mitigated with layered interventions

Controlling COVID-19 transmission in universities poses challenges due to the complex social networks and potential for asymptomatic spread. We developed a stochastic transmission model based on realistic mixing patterns and evaluated alternative mitigation strategies. We predict, for plausible model parameters, that if asymptomatic cases are half as infectious as symptomatic cases, then 15% (98% Prediction Interval: 6-35%) of students could be infected during the first term without additional control measures. First year students are the main drivers of transmission with the highest infection rates, largely due to communal residences. In isolation, reducing face-to-face teaching is the most effective intervention considered, however layering multiple interventions could reduce infection rates by 75%. Fortnightly or more frequent mass testing is required to impact transmission and was not the most effective option considered. Our findings suggest that additional outbreak control measures should be considered for university settings.

Neisseria meningitidis carriage and risk factors among teenagers in Suizhou city in China

Teenagers are important carriers of Neisseria meningitidis, which is a leading cause of invasive meningococcal disease. In China, the carriage rate and risk factors among teenagers are unclear. The present study presents a retrospective analysis of epidemiological data for N. meningitidis carriage from 2013 to 2017 in Suizhou city, China. The carriage rates were 3.26%, 2.22%, 3.33%, 3.53% and 9.88% for 2013, 2014, 2015, 2016 and 2017, respectively. From 2014 to 2017, the carriage rate in the 15- to 19-year-old age group (teenagers) was the highest and significantly higher than that in remain age groups. Subsequently, a larger scale survey (December 2017) for carriage rate and relative risk factors (population density, time spent in the classroom, gender and antibiotics use) were investigated on the teenagers (15- to 19-year-old age) at the same school. The carriage rate was still high at 33.48% (223/663) and varied greatly from 6.56% to 52.94% in a different class. Population density of the classroom was found to be a significant risk factor for carriage, and 1.4 persons/m² is recommended as the maximum classroom density. Further, higher male gender ratio and more time spent in the classroom were also significantly associated with higher carriage. Finally, antibiotic use was associated with a significantly lower carriage rate. All the results imply that attention should be paid to the teenagers and various measures can be taken to reduce the N. meningitidis carriage, to prevent and control the outbreak of IMD.

Outbreaks of meningococcal meningitis in non-African countries over the last 50 years: a systematic review

Background

Meningococcal disease is caused by the bacteria Neisseria meningitidis, leading to substantial mortality and severe morbidity; with serogroups A, B, C, W135, X and Y most significant in causing disease. An outbreak is defined as multiple cases of the same serogroup occurring in a population over a short time-period. A systematic review was performed to gain insight into outbreaks of meningococcal disease and to describe the temporal pattern over the last 50 years in non-African countries.

Methods

PubMed and EMBASE were searched for English-language publications on outbreaks of meningococcal disease in non-African countries between January 1966 and July 2017, with an additional grey literature search. Articles and reports were considered eligible if they reported confirmed meningococcal outbreak cases, included the region, number of cases, and the start and end dates of the outbreak. Data on outbreaks was stratified by geographical region in accordance with the World Health Organization (WHO) regional classification, and case-fatality rates (CFRs) were calculated.

Results

Of the identified publications, 3067 were screened and 73 included, reporting data from 83 outbreaks. The majority of outbreaks were identified in the regions of the Americas (41/83 outbreaks), followed by the European region (30/83 outbreaks). In each of the Western Pacific, Eastern Mediterranean, and South-East Asian regions there were <10 outbreaks reported. The predominant serogroup in the majority of outbreaks was serogroup C (61%), followed by serogroup B (29%), serogroup A (5%) and serogroup W135 (4%). Outbreaks showed a peak in the colder months of both the Northern and Southern Hemispheres. Of the 54 outbreaks where CFR was calculable for all outbreak cases, it ranged from 0%-80%.

Conclusions

These data present a retrospective view of the patterns for meningococcal disease outbreaks in non-African countries, and provide valuable data for monitoring future changes in disease epidemiology and informing preventive measures.

Meningococcal disease burden and transmission in crowded settings and mass gatherings other than Hajj/Umrah: A systematic review

BACKGROUND

Mass gatherings (MGs) such as the Hajj and Umrah pilgrimages are known to amplify the risk of invasive meningococcal disease (IMD) due to enhanced transmission of the organism between attendees. The burden of IMD at MGs other than Hajj and Umrah has not previously been quantified through a systematic review.

METHODS

A systematic search for relevant articles in PubMed and Embase was conducted using MeSH terms; this was buttressed by hand searching. Following data abstraction, a narrative synthesis was conducted to quantify the burden of IMD at MGs and identify potential risk factors and mitigation measures.

RESULTS

Thirteen studies reporting occurrence of IMD at MGs or similar crowded settings were identified. Eight studies reported cases or outbreaks in MGs of ≥1000 people; five others reported IMD in other crowded settings; all occurred between 1991 and 2015. All age groups were involved in the identified studies; however the majority of cases (∼80%) were young people aged 15-24 years. The number of affected people ranged from one to 321 cases and the overall crude estimate of incidence was calculated as 66 per 100,000 individuals. Serogroups A, C, B and W were identified, with serogroups A and C being most common. Of 450 cases of IMD reported in non-Hajj/Umrah MGs, 67 (14.9%) had fatal outcomes.

CONCLUSION

IMD outbreaks at non-Hajj/Umrah MGs are generally much smaller than Hajj-related outbreaks and affect mainly young people. Health education and vaccination should be considered for attendees of high risk non-Hajj/Umrah MGs, especially those involving adolescents and young adults.

Impact of vaccination on meningococcal epidemiology

Neisseria meningitidis may cause invasive disease (meningitis and sepsis), leading to considerable disease burden and mortality. However, effective vaccines are available against most pathogenic serogroups. Large-scale vaccination campaigns with the MCC vaccine conducted in UK and with MenAfriVac in the Sahel have clearly demonstrated the direct and indirect effect of immunization programmes on disease and carriage. Moreover, the introduction of novel subcapsular vaccines against serogroup B, which may cross-protect against other serogroups, is likely to have a further effect on trends. Accurate data collection is key to elaborate vaccination strategies able to reduce meningococcal disease burden through direct protection and herd immunity.

Whole-genome sequencing targets drug-resistant bacterial infections

During the past two decades, the technological progress of whole-genome sequencing (WGS) had changed the fields of Environmental Microbiology and Biotechnology, and, currently, is changing the underlying principles, approaches, and fundamentals of Public Health, Epidemiology, Health Economics, and national productivity. Today’s WGS technologies are able to compete with conventional techniques in cost, speed, accuracy, and resolution for day-to-day control of infectious diseases and outbreaks in clinical laboratories and in long-term epidemiological investigations. WGS gives rise to an exciting future direction for personalized Genomic Epidemiology. One of the most vital and growing public health problems is the emerging and re-emerging of multidrug-resistant (MDR) bacterial infections in the communities and healthcare settings, reinforced by a decline in antimicrobial drug discovery. In recent years, retrospective analysis provided by WGS has had a great impact on the identification and tracking of MDR microorganisms in hospitals and communities. The obtained genomic data are also important for developing novel easy-to-use diagnostic assays for clinics, as well as for antibiotic and therapeutic development at both the personal and population levels. At present, this technology has been successfully applied as an addendum to the real-time diagnostic methods currently used in clinical laboratories. However, the significance of WGS for public health may increase if: (a) unified and user-friendly bioinformatics toolsets for easy data interpretation and management are established, and (b) standards for data validation and verification are developed. Herein, we review the current and future impact of this technology on diagnosis, prevention, treatment, and control of MDR infectious bacteria in clinics and on the global scale.

Sex bias in infectious disease epidemiology: patterns and processes

BACKGROUND

Infectious disease incidence is often male-biased. Two main hypotheses have been proposed to explain this observation. The physiological hypothesis (PH) emphasizes differences in sex hormones and genetic architecture, while the behavioral hypothesis (BH) stresses gender-related differences in exposure. Surprisingly, the population-level predictions of these hypotheses are yet to be thoroughly tested in humans.

METHODS AND FINDINGS

For ten major pathogens, we tested PH and BH predictions about incidence and exposure-prevalence patterns. Compulsory-notification records (Brazil, 2006-2009) were used to estimate age-stratified ♂:♀ incidence rate ratios for the general population and across selected sociological contrasts. Exposure-prevalence odds ratios were derived from 82 published surveys. We estimated summary effect-size measures using random-effects models; our analyses encompass ∼0.5 million cases of disease or exposure. We found that, after puberty, disease incidence is male-biased in cutaneous and visceral leishmaniasis, schistosomiasis, pulmonary tuberculosis, leptospirosis, meningococcal meningitis, and hepatitis A. Severe dengue is female-biased, and no clear pattern is evident for typhoid fever. In leprosy, milder tuberculoid forms are female-biased, whereas more severe lepromatous forms are male-biased. For most diseases, male bias emerges also during infancy, when behavior is unbiased but sex steroid levels transiently rise. Behavioral factors likely modulate male-female differences in some diseases (the leishmaniases, tuberculosis, leptospirosis, or schistosomiasis) and age classes; however, average exposure-prevalence is significantly sex-biased only for Schistosoma and Leptospira.

CONCLUSIONS

Our results closely match some key PH predictions and contradict some crucial BH predictions, suggesting that gender-specific behavior plays an overall secondary role in generating sex bias. Physiological differences, including the crosstalk between sex hormones and immune effectors, thus emerge as the main candidate drivers of gender differences in infectious disease susceptibility.

Resolution of a meningococcal disease outbreak from whole-genome sequence data with rapid Web-based analysis methods

The increase in the capacity and reduction in cost of whole-genome sequencing methods present the imminent prospect of such data being used routinely in real time for investigations of bacterial disease outbreaks. For this to be realized, however, it is necessary that generic, portable, and robust analysis frameworks be available, which can be readily interpreted and used in real time by microbiologists, clinicians, and public health epidemiologists. We have achieved this with a set of analysis tools integrated into the PubMLST.org website, which can in principle be used for the analysis of any pathogen. The approach is demonstrated with genomic data from isolates obtained during a well-characterized meningococcal disease outbreak at the University of Southampton, United Kingdom, that occurred in 1997. Whole-genome sequence data were collected, de novo assembled, and deposited into the PubMLST Neisseria BIGSdb database, which automatically annotated the sequences. This enabled the immediate and backwards-compatible classification of the isolates with a number of schemes, including the following: conventional, extended, and ribosomal multilocus sequence typing (MLST, eMLST, and rMLST); antigen gene sequence typing (AGST); analysis based on genes conferring antibiotic susceptibility. The isolates were also compared to a reference isolate belonging to the same clonal complex (ST-11) at 1,975 loci. Visualization of the data with the NeighborNet algorithm, implemented in SplitsTree 4 within the PubMLST website, permitted complete resolution of the outbreak and related isolates, demonstrating that multiple closely related but distinct strains were simultaneously present in asymptomatic carriage and disease, with two causing disease and one responsible for the outbreak itself.

Kinetics of immune responses to nasal challenge with meningococcal polysaccharide one year after serogroup-C glycoconjugate vaccination

BACKGROUND

Recipients of serogroup-C glycoconjugate meningococcal vaccine (MCC) exhibit waning of serum bactericidal antibody (SBA) titers, but the rate of decline and the speed of their immunological memory in response to new meningococcal nasopharyngeal colonization are unknown.

METHODS

In a prospective challenge study, we measured persistence of SBA and anti-Neisseria meningitidis serogroup-C (MenC) immunoglobulin (Ig) G and IgA in adults aged 18-39, 28 days and 12 months after receiving MCC. Volunteers were then challenged intranasally with 50 μg MenC polysaccharide to mimic meningococcal colonization, and systemic and mucosal antibody responses were measured.

RESULTS

All subjects had protective SBA titers (≥8) 28 days after MCC vaccination, but 12.3% and 20.2% had unprotective (<8) or low (<128) levels, respectively, after 12 months. Following rechallenge (12 months postvaccination) and measurement of antibody responses after 4, 7, and 10 days, rises in SBA titers were only observed in subjects with low (<128) or nonprotective (<8) prerechallenge SBA titers. In subjects with pre rechallenge SBA titers <8, the majority did not reach a protective SBA titer until 7 days post-rechallenge. MenC-specific IgG levels rose in both serum and saliva in correlation with SBA titers. No detectable rise in salivary IgA was observed.

CONCLUSIONS

In those individuals who fail to retain protective SBA 12 months after MCC, immunological memory fails to generate protective systemic and mucosal antibodies until 7 days post intranasal challenge with cognate meningococcal polysaccharide. This is likely too slow to protect from natural meningococcal infection. MCC vaccinees rely on persistence of antibody levels rather than immunological memory for sustained protection.

Social behavior and meningococcal carriage in British teenagers

Understanding predisposing factors for meningococcal carriage may identify targets for public health interventions. Before mass vaccination with meningococcal group C conjugate vaccine began in autumn 1999, we took pharyngeal swabs from ≈14,000 UK teenagers and collected information on potential risk factors. Neisseria meningitidis was cultured from 2,319 (16.7%) of 13,919 swabs. In multivariable analysis, attendance at pubs/clubs, intimate kissing, and cigarette smoking were each independently and strongly associated with increased risk for meningococcal carriage (p<0.001). Carriage in those with none of these risk factors was 7.8%, compared to 32.8% in those with all 3. Passive smoking was also linked to higher risk for carriage, but age, sex, social deprivation, home crowding, or school characteristics had little or no effect. Social behavior, rather than age or sex, can explain the higher frequency of meningococcal carriage among teenagers. A ban on smoking in public places may reduce risk for transmission.

The natural history of meningococcal carriage and disease

The prevalence of Neisseria meningitidis carriage is highest in teenagers and lowest in young children. In contrast, invasive meningococcal disease is most common in young children with a smaller secondary peak in teenagers. Data on carriage and disease were analysed to quantify the risks of infection and disease by age and serogroup. The forces of infection for serogroups B, C, other meningococci and Neisseria lactamica were modelled together with the risk of disease given infection for serogroups B and C, using maximum likelihood to fit the models to the available data. The risk of meningococcal disease given infection declines steeply through childhood and is higher for serogroup C than for serogroup B. The secondary peak in disease in teenagers appears to be explained mostly by increased transmission although there is a suggestion that other factors may also contribute. These analyses provide important insights and may be used to guide further data collection and modelling studies.

Development of immunity to serogroup B meningococci during carriage of Neisseria meningitidis in a cohort of university students

Understanding the basis of protective immunity is a key requirement for the development of an effective vaccine against infection with Neisseria meningitidis of serogroup B. We have conducted a longitudinal study into the dynamics of meningococcal acquisition and carriage in first-year university students. The detection of carriage of serogroup B meningococci correlated with an increase in detection of serum bactericidal activity (SBA) against both colonizing and heterologous serogroup B strains. Once induced, SBA remained high throughout the study. Although students showed increases in antibodies reactive with capsular polysaccharide and lipopolysaccharide (LPS), these antibody responses were transitory, and their decline was not accompanied by a corresponding decline in SBA. In contrast, there was a significant correlation between the presence of antibodies to the PorA outer membrane protein and SBA against both homologous and heterologous strains. SBA induced by a PorA-negative mutant confirmed the contribution of PorA to heterologous activity. Increases in SBA against a range of serogroup B strains were also observed in students in whom no meningococcal carriage was detected. This heterologous protection could not be associated with the presence of antibodies reacting with capsule, LPS, PorA, PorB, Rmp, Opa, Opc, or pilin, demonstrating that other, as yet unidentified, antigens contribute to the development of immunity to serogroup B meningococci. Identification of such antigens with the ability to induce an effective cross-reactive bactericidal response to a range of strains would be a major step in the production of a universally effective vaccine against infections caused by serogroup B meningococci.

Surface plasmon resonance analysis of antipolysaccharide antibody specificity: responses to meningococcal group C conjugate vaccines and bacteria

Antibody (Ab) responses to polysaccharides (PS), such as Neisseria meningitidis group C PS (MCPS), are characterized as being thymus independent and are restricted with regard to clonotype and isotype expression. PS conjugated to proteins, e.g., MCPS coupled with tetanus toxoid or the diphtheria toxin derivative CRM197, elicit thymus-dependent responses. The present study developed a surface plasmon resonance approach to evaluate Ab responses to MCPS conjugate vaccines, including either O-acetylated (OAc+) or de-O-acetylated (OAc-) forms of the PS. The results were generally consistent with those obtained by enzyme-linked immunosorbent assay and showed that sera from mice immunized with conjugate vaccines contain Abs that bind more effectively to OAc+ and OAc- MCPS than sera from mice immunized with fixed bacteria. The data suggest a critical shared or overlapping epitope recognized by all the conjugate vaccine immune sera and strategies for assessing polyclonal Ab avidity.

Should university students be vaccinated against meningococcal disease in Canada?

OBJECTIVE

To evaluate the benefit and costs of vaccination of university students against invasive meningococcal disease (IMD) in Canada.

METHODS

Published studies were reviewed and a simulation model was used.

RESULTS

IMD risk seems to be of low magnitude, but consequences can be dramatic. Over a 10-year period, IMD risk reduction would be slightly greater using a monovalent C conjugate vaccine than a quadrivalent polysaccharide vaccine. From a societal perspective, costs per quality-adjusted life-years gained would be between $135,000 and $698,000, according to epidemiological scenarios and with vaccine purchase prices between $35 and $50 per dose.

CONCLUSIONS

Economic indices exceed proposed criteria for cost effective public health programs, but from the perspective of students and parents, the cost of vaccination might be worth the benefit.

Characterization of humoral and cellular immune responses elicited by meningococcal carriage

In order to study the immune response elicited by asymptomatic carriage of Neisseria meningitidis, samples of serum, peripheral blood mononuclear cells (PBMCs), and saliva were collected from a cohort of more than 200 undergraduate students in Nottingham, United Kingdom, who were subject to high rates of acquisition and carriage of meningococci. Serum immunoglobulin G levels were elevated following increases in the rate of carriage, and these responses were specific for the colonizing strains. In order to investigate T-cell responses, PBMCs from 15 individuals were stimulated with a whole-cell lysate of the H44/76 meningococcal strain (B:15:P1.7,16), stained to detect cell surface markers and intracellular cytokines, and examined by flow cytometry. The cells were analyzed for expression of CD69 (to indicate activation), gamma interferon (IFN-gamma) (a representative T-helper 1 subset [Th1]-associated cytokine), and interleukin-5 (IL-5) (a Th2-associated cytokine). Following a brief meningococcal stimulation, the numbers of CD69(+) IFN-gamma(+) CD56/16(+) NK cells were much higher than cytokine-positive CD4(+) events. Both IFN-gamma(+) and IL-5(+) events were detected among the CD69(+) CD4(+) population, leading to the conclusion that an unbiased T-helper subset response was elicited by meningococcal carriage.

Detection of meningococcal carriage by culture and PCR of throat swabs and mouth gargles

The standard method for detecting meningococcal carriage is culture of throat swabs on selective media, but the levels of carriage determined depend heavily on the skills of the individuals taking the swab and interpreting the cultures. This study aimed to determine the most sensitive detection method for meningococcal carriage. Throat swabs and saline mouth gargles, obtained from 89 university students, were processed in parallel by conventional culture and TaqMan ctrA PCR. Carriage of meningococci, as detected by the combined methods, was 20%. The sensitivities of throat swab culture, throat swab PCR, gargle culture, and gargle PCR were 72, 56, 56, and 50%, respectively, and the probabilities that these techniques would correctly identify the absence of carriage (negative predictive value [NPV]) were 93.4, 89.9, 89.9, and 88.8%. Culturing both throat swabs and gargles increased the NPV to 98.6%. The further addition of throat swab PCR increased this to 100%. Testing gargles by both culture and PCR was as sensitive as testing throat swabs by both methods, suggesting that gargles may be a suitable alternative for large-scale screening studies when throat swabs are difficult to obtain, although they required more lengthy laboratory processing. PCR was a useful adjunct to culture for detecting nasopharyngeal carriage, but it failed to detect some nongroupable strains. For maximum sensitivity, a combination of techniques was required. This study indicates the confidence with which health care professionals involved in meningococcal screening can regard laboratory results.