Nongroupable Isolates Research Articles

Effectiveness of quadrivalent meningococcal conjugate vaccine against meningococcal carriage and genotype character changes: A secondary analysis of prospective cohort study in Korean military trainees

ObjectiveWe evaluated the changes and molecular epidemiology of meningococcal carriage in military recruits after quadrivalent meningococcal conjugate vaccines (MenACWY) vaccination. MethodsOropharyngeal swabs were obtained at the beginning and end of the 5-week training. Carriage rates before and after vaccination were compared to estimate vaccine effectiveness (VE). Cultured isolates were characterized by multi-locus sequence typing (MLST). ResultsOf 866 vaccinated participants, the overall carriage rate was 10.6% prior to MenACWY vaccination and it tended to decrease to 9.5% after 5 weeks of vaccination (P = 0.424). Carriage rate of serogroup ACWY decreased significantly after vaccination (VEACWY = 72.6%, 95% CI: 36.3-88.2), and serogroup C was particularly reduced (VEC = 83.0%, 95% CI: 50.6-94.1), whereas non-groupable isolates increased significantly after vaccination (VENG = -76.1%, 95% CI: -176.2 to -13.1). Among 99 carriage isolates with complete MLST profiles, 45 different sequence types with nine clonal complexes (CCs) were identified, and 35.3% of the carriage isolates belonged to hypervirulent strains such as CC-32, CC-41/44, and CC-269. ConclusionsMenACWY vaccination in military recruits led to reduced carriage rates of serogroups C, W, and Y within a short 5-week period. However, serogroup B isolates belonging to the hypervirulent lineage remained after the implementation of MenACWY vaccination.

Emergence of Neisseria meningitidis W South American sublineage strain variant in Brazil: disease and carriage.

Introduction. Invasive meningococcal disease is a major health problem, impacting morbidity and mortality worldwide. Exploratory genomics has revealed insights into adaptation, transmissibility and virulence to elucidate endemic, outbreaks or epidemics caused by Neisseria meningitidis serogroup W (MenW) strains.Gap Statement. Limited information on the genomics of Neisseria meningitis serogroup W ST11/cc11 is available from emerging countries, especially in contemporary isolates.Aim. To (i) describe the antigenic diversity and distribution of genetic lineages of N. meningitidis serogroup W circulating in Brazil; (ii) study the carriage prevalence of hypervirulent clones in adolescents students and (iii) analyse the potential risk factors for meningococcal carriage.Methodology. Using whole-genome sequencing, we analysed the genomic diversity of 92 invasive N. meningitidis serogroup W isolates circulating in Brazil from 2016 to 2019. A cross-sectional survey of meningococcal carriage was conducted in 2019, in the city of Florianópolis, Brazil, among a representative sample of 538 students.Results. A predominance (58.5 %, 41/82) of ST11/cc11 presenting PorB2-144, PorA VR1-5, VR2-2, FetA 1-1, and a novel fHbp peptide 1241 was found on invasive N. meningitidis W isolates, on the other hand, a high diversity of clonal complexes was found among carriage isolates. The overall carriage rate was 7.5 % (40/538). A total of 28 of 538 swab samples collected were culture positive for N. meningitidis, including four serogroup/genogroup B isolates (14.8 %;4/27), 1 serogroup/genogroup Y isolate (3.7 %;1/27), 22 (81.5 %; 22/27) non-groupable isolates. No MenW isolate was identified among carriages isolates.Conclusion. This report describes the emergence of the new MenW ST11/cc11 South America sublineage variant, named here, 2016 strain, carrying a novel fHbp peptide 1241, but its emergence, was not associated with an increased MenW carriage prevalence. Continuous surveillance is necessary to ascertain the role of this sublineage diversification and how its emergence can impact transmission.

Longitudinal study of meningococcal carriage rates in university entrants living in a dormitory in South Korea.

University students, especially those living in dormitories, are known to have a high risk of invasive meningococcal disease. We performed a longitudinal study to investigate the change in Neisseria meningitidis carriage rates and identify the risk factors for carriage acquisition in university students in South Korea. We recruited university entrants who were admitted to a student dormitory. Pharyngeal swabs were taken from participants at baseline, 1 month, and 3 months, and the subjects completed a questionnaire. Culture and real-time polymerase chain reaction (PCR) for species-specific ctrA and sodC genes were performed. The cultured isolates or PCR-positive samples were further evaluated for epidemiologic characterization using serogrouping, PorA typing, FetA typing, and multilocus sequence typing (MLST). At the first visit, we enrolled 332 participants who were predominantly male (64.2%) with a median age of 19 years. Meningococcal carriage rates increased from 2.7% (95% confidence interval [CI] 0.9–4.4%) at baseline to 6.3% (95% CI 3.4–9.0%) at 1 month and 11.8% (95% CI 7.8–15.6%) at 3 months. Nongroupable isolates accounted for 50.0% of all isolates, with serogroup B being the next most prevalent (24.1%). In the study population, male sex (OR 2.613, 95% CI 1.145–5.961, p = 0.022) and frequent pub or club visits (OR 3.701, 95% CI 1.536–8.919, p = 0.004) were significantly associated with meningococcal carriage. Based on serotype and MLST analyses, six carriers transmitted meningococci to other study participants. N. meningitidis carriage rates among new university entrants who lived in a dormitory significantly increased within the first 3 months of dormitory stay, probably owing to the transmission of identical genotype among students. Based on the risk of meningococcal disease, meningococcal vaccination should be considered for students before dormitory admission.

Meningococcal carriage 7 years after introduction of a serogroup A meningococcal conjugate vaccine in Burkina Faso: results from four cross-sectional carriage surveys

SummaryBackgroundIn the first 2 years after a nationwide mass vaccination campaign of 1–29-year-olds with a meningococcal serogroup A conjugate vaccine (MenAfriVac) in Burkina Faso, carriage and disease due to serogroup A Neisseria meningitidis were nearly eliminated. We aimed to assess the long-term effect of MenAfriVac vaccination on meningococcal carriage and herd immunity.MethodsWe did four cross-sectional studies of meningococcal carriage in people aged 9 months to 36 years in two districts of Burkina Faso between May 2, 2016, and Nov 6, 2017. Demographic information and oropharyngeal swabs were collected. Meningococcal isolates were characterised using whole-genome sequencing.FindingsOf 14 295 eligible people, 13 758 consented and had specimens collected and laboratory results available, 1035 of whom were meningococcal carriers. Accounting for the complex survey design, prevalence of meningococcal carriage was 7·60% (95% CI 5·67–9·52), including 6·98% (4·86–9·11) non-groupable, 0·48% (0·01–0·95) serogroup W, 0·10% (0·01–0·18) serogroup C, 0·03% (0·00–0·80) serogroup E, and 0% serogroup A. Prevalence ranged from 5·44% (95% CI 4·18–6·69) to 9·14% (6·01–12·27) by district, from 4·67% (2·71–6·64) to 11·17% (6·75–15·59) by round, and from 3·39% (0·00–8·30) to 10·43% (8·08–12·79) by age group. By clonal complex, 822 (88%) of 934 non-groupable isolates were CC192, all 83 (100%) serogroup W isolates were CC11, and nine (69%) of 13 serogroup C isolates were CC10217.InterpretationOur results show the continued effect of MenAfriVac on serogroup A meningococcal carriage, for at least 7 years, among vaccinated and unvaccinated cohorts. Carriage prevalence of epidemic-prone serogroup C CC10217 and serogroup W CC11 was low. Continued monitoring of N meningitidis carriage will be crucial to further assess the effect of MenAfriVac and inform the vaccination strategy for future multivalent meningococcal vaccines.FundingBill & Melinda Gates Foundation and Gavi, the Vaccine Alliance.

Molecular characterization of Neisseria meningitidis isolates recovered from 11-19-year-old meningococcal carriers in Salvador, Brazil.

Characterization of meningococci isolated from the pharynx is essential towards understanding the dynamics of meningococcal carriage and disease. Meningococcal isolates, collected from adolescents resident in Salvador, Brazil during 2014, were characterized by multilocus sequence typing, genotyping or whole-genome sequencing. Most were nongroupable (61.0%), followed by genogroups B (11.9%) and Y (8.5%). We identified 34 different sequence types (STs), eight were new STs, distributed among 14 clonal complexes (cc), cc1136 represented 20.3% of the nongroupable isolates. The porA and fetA genotypes included P1.18,25–37 (11.9%), P1.18–1,3 (10.2%); F5-5 (23.7%), F4-66 (16.9%) and F1-7 (13.6%). The porB class 3 protein and the fHbp subfamily A (variants 2 and 3) genotypes were found in 93.0 and 71.0% of the isolates, respectively. NHBA was present in all isolates, and while most lacked NadA (94.9%), we detected the hyperinvasive lineages B:P1.19,15:F5-1:ST-639 (cc32); C:P1.22,14–6:F3-9:ST-3780 (cc103) and W:P1.5,2:F1-1:ST-11 (cc11). This is the first report on the genetic diversity and vaccine antigen prevalence among N. meningitidis carriage isolates in the Northeast of Brazil. This study highlights the need for ongoing characterization of meningococcal isolates following the introduction of vaccines and for determining public health intervention strategies.

Prevalence and epidemiology of meningococcal carriage in Southern Ethiopia prior to implementation of MenAfriVac, a conjugate vaccine.

Background Neisseria meningitidis colonizes humans and transmits mainly by asymptomatic carriage. We sought to determine the prevalence and epidemiology of meningococcal carriage in Ethiopia prior to the introduction of MenAfriVac, a serogroup A meningococcal conjugate vaccine.MethodsA cross-sectional meningococcal carriage study was conducted in Arba Minch, southern Ethiopia. A total of 7479 oropharyngeal samples were collected from 1 to 29 year old volunteers, between March and October, 2014. The swabs were cultured for N. meningitidis and Neisseria lactamica in Ethiopia. N. meningitidis isolates were confirmed and characterized by their serogroup, sequence type (ST) and PorA:FetA profile in Norway.ResultsOverall carriage prevalence was 6.6 %. There was no significant difference in overall carriage between male (6.7 %) and female (6.4 %) participants. Highest carriage prevalence (10.9 %) for females was found in the 15–19 years of age, while prevalence among males was highest (11.3 %) in the 20–24 age group. Non-groupable isolates dominated (76.4 %), followed by serogroups X (14.0 %) and W (5.9 %) isolates. No serogroup A was found. Most non-groupable isolates were ST-192. Serogroup W isolates were assigned to the ST-11 clonal complex, and serogroup X isolates to the ST-181 and ST-41/44 clonal complexes. Overall carriage prevalence of N. lactamica was 28.1 %. Carriage of N. meningitidis and N. lactamica varied depending on age and geographic area, but there was no association between carriage of the two species.ConclusionsEpidemic strains of serogroups W and X were circulating in this area of Ethiopia. As no serogroup A was found among the carriage isolates the immediate impact of mass-vaccination with MenAfriVac on transmission of N. meningitidis in this population is expected to be marginal.

Neisseria meningitidisSerogroup W‐135 Carriage among US Travelers to the 2001 Hajj

In 2000, a large international outbreak of meningococcal disease caused by Neisseria meningitidis serogroup W-135 was identified among pilgrims returning from the Hajj in Saudi Arabia. To assess ongoing risk, we evaluated N. meningitidis carriage among US travelers to the 2001 Hajj. Of 25 N. meningitidis isolates obtained, 15 (60%) were nongroupable and 8 (32%) were serogroup W-135 when tested by standard slide-agglutination techniques. Two additional nongroupable isolates were characterized as serogroup W-135 when tested by polymerase chain reaction. Nine of 10 serogroup W-135 isolates were indistinguishable from the Hajj-2000 clone. None of the departing, but 9 (1.3%) of the returning, pilgrims carried serogroup W-135 (P=.01); all carriers reported previous vaccination. Carriage of N. meningitidis serogroup W-135 increased significantly in pilgrims returning from the Hajj. Although the risk of disease to pilgrims appears to be low, the risk of spread to others of this pathogenic strain remains a concern.

PCR-Based Assay for Detection of Neisseria meningitidis Capsular Serogroups 29E, X, and Z

PCR-based assays for the identification of Neisseria meningitidis serogroups 29E, X, and Z by detection of specific regions of the ctrA gene are described. The specificities of these assays were confirmed using serogroups A, B, C, 29E, H, W135, X, Y, and Z and nongroupable meningococcal isolates.

Genetic basis for nongroupable Neisseria meningitidis.

Nongroupable Neisseria meningitidis may constitute one-third or more of meningococcal isolates recovered from the nasopharynx of human carriers. The genetic basis for nongroupability was determined in isolates obtained from a population-based study in which 60 (30.9%) of 194 meningococcal isolates from asymptomatic carriers were not groupable. Forty-two percent of nongroupable isolates were related to serogroup Y ET-508/ST-23 clonal complex strains, the most common groupable carrier isolate from the study population. Nongroupable isolates were all rapidly killed by 10% normal human serum. The capsule loci of 6 of the ET-508/ST-23 complex strains and of 25 other genetically diverse nongroupable meningococci were studied in detail. Serogroup A or novel capsule biosynthesis genes were not found. Nongroupable isolates were genetically serogroup Y, B, or C isolates that did not express capsule but were related to groupable isolates found in the population (class I); capsule deficient because of insertion element-associated deletions of capsule biosynthesis genes (class II); or isolates that lacked all capsule genes and formed a distinct genetic cluster not associated with meningococcal disease (class III).

Nucleotide Sequence Analysis of the Sialyltransferase Genes of Meningococcal Serogroups B, C, Y and W135

A rapid method for serogrouping meningococci is essential for the characterization of phenotypically non-groupable meningococcal isolates and clinical samples, particularly for public health management purposes. The Scottish Meningococcus and Pneumococcus Reference Laboratory (SMPRL) provides serogrouping results of meningococcal isolates and clinical samples using a PCR assay which detects restriction fragment length polymorphisms in meningococcal serogroups B, C, Y and W135. Although this PCR system was invaluable when first introduced, it has several drawbacks and lacks the required sensitivity for detecting DNA in clinical samples. Due to the recent introduction of the meningococcal group C conjugate vaccine and an impending group B vaccine, a more robust and informative method for serogroup determination is required. A protocol was devised allowing PCR amplification of the siaD gene of serogroup B, C, Y and W135 meningococci. This system was multiplexed and allowed serogroup differentiation between serogroups B and C and also between B/C and Y/W135 by product size analysis. A nested stage was incorporated into the system for enhanced detection of meningococci in clinical samples, and finally a sequencing protocol was designed allowing detection of any nucleotide changes within the siaD gene. This system allows rapid serogrouping results for use within an agarose gel system as well as more informative results when used for sequencing within the siaD gene.

Unusual antineisserial activity expressed by a systemic isolate of Neisseria meningitidis. antimeningococcal effect and properties.

Antineisserial activity expressed by the systemic Neisseria meningitidis strain 77/79A was studied using the cross-streaking technique. Of 271 meningococcal isolates tested, > 84% were sensitive to this strain. The degree of susceptibility was largely dependent upon the agent characteristics of the individual isolates. Serogroup A sulfonamide-resistant systemic strains and non-groupable sulfonamide-sensitive isolates from healthy carriers were highly sensitive to the antagonistic activity. Among insensitive or weakly sensitive strains, serogroup B sulfonamide-resistant isolates dominated. The activity is of general interest as it also antagonized growth of bacteriocin producers. Colonization by the producer strain might determine the agent characteristics of a surviving population. Group B was predominant among disease-causing strains in Norway at the time when strain 77/79A was isolated. A component was purified by ammonium sulfate precipitation, gel filtration and hydrophobic interaction chromatography. It was bacteriostatic and partly resistant to proteolysis by trypsin. Preparations remained active after 30 min at 90 degrees C, but activity was lost after 20 min at 120 degrees C. Nevertheless, sodium dodecyl sulfate-polyacrylamide gel electrophoresis produced a band by Coomassie Brilliant Blue staining, corresponding to a molecular mass of approximately 52 kDa. Further characterization was limited due to the low levels of active substance produced.

Carriers of Neisseria meningitidis in household contacts of meningococcal disease cases in Catalonia (Spain).

A population-based study was carried out in Catalonia (Spain) from May 1998 to April 1999 to determine the prevalence of Neisseria meningitidis strains in meningococcal disease (MD) cases and their contacts, as well as the prevalence of meningococci in close contacts of patients with MD, and risk factors for its carriage. A total of 364 close contacts of 87 patients with MD were studied. Throat samples were collected by hospital staff before rifampicin chemoprophylaxis was begun. For each contact, a questionnaire was completed for sociodemographic and epidemiological data. A total of 61 contacts (an overall prevalence of 16.8%) were carriers of meningococcal strains (40 B, 10 C, 1 Z and 10 non-groupable isolates). This prevalence is two to three times higher than in the general population (5-10%). In 33/61 microbiologically confirmed cases (54%) and in 9/26 probable cases (35%), contacts carrying N. meningitidis were found. In 22/33 confirmed cases with carrier contacts, it was possible to study the phenotype of the carrier and patient strains (sero-group, serotype and serosubtype). In 14 cases (64%), both strains were identical, in four cases, only a minor change was observed, in three cases, some strain (from the case or from his contact) was non-serotypable and non-serosubtypable, and in one case, both isolates were completely different. Bivariate analysis identified five statistically significant risk factors for meningococcal carriage: age (5-9 years old), meningococcal A+C vaccination, severe household overcrowding, social class and heavy active smoking (>20 cigarettes a day). Multivariate analysis revealed that of these five variables, only heavy active smoking remained statistically significant when the other factors were controlled.

Sero/subtyping of Neisseria meningitidis isolated from patients in Spain.

To know the types of meningococcal strains in Spain, we serotyped and subtyped 743 Neisseria meningitidis isolates recovered between 1990 and 1992 from patients. A great number of serogroup B, serogroup C and non-groupable meningococci reacted with the serotyping reagents while many serogroup C and non-groupable isolates did not react with the serosubtyping reagents (78.2% and 54.8% respectively); only 8.9% of serogroup B meningococci were non-subtypeable (NST). Distribution of serotypes was similar in serogroup C and in non-groupable strains. Isolates showed great variability in antigenic phenotypes (71 in serogroup B, 20 in serogroup C and 25 in non-groupable meningococci). The most frequent antigenic combinations were 4:P1.15 (39.8%) in serogroup B, 2b:NST (55.8%) in serogroup C and 2b:NST (35.6%) in non-groupable meningococci.

Neisseria meningitidis group B capsular polysaccharide

A total of 41 Neissera meningitidis isolates were analyzed for capsular polysaccharide (CP) and lipopolysaccharide (LPS) release and filtrability. Twenty-two of these isolates were serogroup B from blood or cerebrospinal fluid of patients, five were group B isolates from healthy throat carriers, and 14 were nongroupable (acapsular) meningococcal isolates from healthy carriers. Filtration of liquid whole-cell cultures through cellulose acetate-nitrate filters resulted in distinctly lower LPS filtrate activity for acapsular than for capsular meningococci (p less than 0.001). On the other hand, when polysulfone membrane filtration was performed, filtrates from acapsular and capsular meningococci contained LPS in similar amounts. These results indicate that LPS-containing particles released from acapsular isolates are larger or more aggregated than corresponding CP- and LPS-containing particles released from capsular isolates. The LPS released from acapsular isolates apparently are more efficiently retained by adsorption to cellulose acetate-nitrate. From the capsular isolates comparatively more CP than LPS appeared to be released, as related to cell-bound amounts. The total amounts of CP and released, filtrable LPS through cellulose acetate-nitrate filters were both relatively low and had similar values for capsular carrier meningococci and systemic isolates from mild meningococcal disease. The amount of CP released and passing this type of membrane was significantly higher for systemic isolates from severe septicemia than from mild meningococcal disease (p = 0.03).

Hyaluronidase production in Streptococcus milleri in relation to infection.

One hundred and seven (41%) of 262 isolates of Streptococcus milleri, from human sources, produced hyaluronidase. Hyaluronidase production was commoner in beta haemolytic isolates 32 of 39 (82%), many of which were of Lancefield group F. But hyaluronidase was also found in alpha and non-haemolytic isolates, and in groups A, C, G, and non-groupable isolates. There was a strong association between hyaluronidase production and isolation from known internal abscesses (48/58, 83%) compared with isolates from the normal flora of uninfected sites (24/97, 25%). Isolates from 15 patients with endocarditis were uniformly negative, although 13 of 25 (52%) isolates from dental plaque produced the enzyme. Production of hyaluronidase may therefore be an important determinant in the pathogenicity of infection by S milleri and could be helpful in predicting the likelihood of deep purulent lesions in isolates from blood culture.

Incidence and characterization of beta-hemolytic Streptococcus milleri and differentiation from S. pyogenes (group A), S. equisimilis (group C), and large-colony group G streptococci.

The biochemical characteristics of 172 clinical isolates of group A, C, F, or G or "nongroupable" beta-hemolytic streptococci were examined. Among these isolates, 91 were identified as beta-hemolytic strains of Streptococcus milleri. The remaining isolates included 20 Streptococcus pyogenes, 21 Streptococcus equisimilis, 37 large-colony group G streptococci, and 3 unidentified nongroupable isolates. A majority (84%) of the S. milleri strains possessed Lancefield group antigen (3 A, 27 C, 41 F, and 5 G), whereas 15 S. milleri strains (16%) were nongroupable. Serological tests did not differentiate S. milleri isolates with group A, C, or G antigen from S. pyogenes (group A), S. equisimilis (group C), or large-colony group G streptococci. Biochemical tests which were found useful for differentiation included the Voges-Proskauer test, hydrolysis of pyroglutamic acid and beta-D-glucuronide, bacitracin susceptibility, and acid production from ribose. S. milleri represented 56% of the group C, 100% of the group F, and 83% of the nongroupable beta-hemolytic streptococci isolated in our clinical laboratory, whereas the incidence of S. milleri among group A and group G streptococci was estimated to be low. The role of beta-hemolytic S. milleri as a cause of human infection remains obscured by the failure to routinely differentiate S. milleri from other beta-hemolytic streptococci.

Occurrence of Streptococcus milleri among beta-hemolytic streptococci isolated from clinical specimens.

A total of 256 beta-hemolytic streptococcal isolates were subjected to serological and physiological tests to identify those which could be classified as Streptococcus milleri. S. milleri accounted for 75% of 70 group C isolates, 15% of 69 group G isolates, 75% of 16 nongroupable isolates, and 100% of 20 group F isolates examined. No S. milleri isolates were encountered among the 90 group A streptococci studied. Of the 95 beta-hemolytic S. milleri isolates examined, 81% were recovered from respiratory specimens.

Natural bactericidal activity of human serum against Neisseria meningitidis isolates of different serogroups and serotypes.

We used a microtiter assay, standardized with serum-sensitive and serum-resistant strains of Neisseria gonorrhoeae, to determine the serum sensitivity of Neisseria meningitidis isolates of different serogroups and serotypes. Numbers of serum-resistant isolates varied among serogroups: group A = 7/8 (88%), group B = 26/50 (52%), group C = 5/8 (63%), group Y = 4/6 (67%), group W135 = 5/8 (63%), group 29E (Z') = 0/8 (0%), nongroupable isolates = 0/8 (0%). In comparison to group B isolates, group A isolates were more serum resistant (P less than 0.06), and group 29E and nongroupable isolates were more serum sensitive (P less than 0.001). Poor correlation was observed between serum sensitivity results and group-specific levels of bactericidal antibody in the normal human serum of volunteers. The frequency of serum-resistant strains among group B disease isolates (45%) was not significantly different from throat isolates of asymptomatic carriers (52%). Serotype 2 isolates of group B were no more serum resistant than were other serotypes examined. The serum sensitivity of meningococci appears to involve both capsular and noncapsular antigens and varies between serogroups. The increased serum sensitivity of nongroupable and group 29E isolates may account for the low incidence of disease caused by these organisms.