Laboratory quality control in a multicentre meningococcal carriage study in Burkina Faso.

To investigate the potential herd immunity effect of MenAfriVac, a new conjugate vaccine against serogroup A Neisseria meningitidis, a multiple cross-sectional carriage study was conducted in three districts in Burkina Faso in 2009, yielding a total of 20 326 oropharyngeal samples. A major challenge was the harmonisation of operational procedures and ensuring the reliability of results. Here we describe the laboratory quality control (QC) system that was implemented. Laboratory analysis performed by three local laboratories included colony morphology assessment, oxidase test, Gram stain, ß-galactosidase activity using o-nitrophenyl-ß-galactopyranoside (ONPG), γ-glutamyl transferase (GGT) activity and slide agglutination serogrouping. Internal QC was performed on media, reagents, laboratory equipment and field conditions. Confirmation of results and molecular characterisation was performed at the Norwegian Institute of Public Health (Oslo, Norway). External QC was performed on 3% of specimens where no colonies morphologically resembling N. meningitidis had been identified and on 10% of non-ONPG-/GGT+ isolates. The QC system was a critical element: it identified logistical and operational problems in real time and ensured accuracy of the final data. The overall N. meningitidis carriage prevalence (3.98%) was probably slightly underestimated and the calculated true prevalence was 4.48%. The components of the presented QC system can easily be implemented in any other laboratory study.

sodC-based real-time PCR for detection of Neisseria meningitidis.

Real-time PCR (rt-PCR) is a widely used molecular method for detection of Neisseria meningitidis (Nm). Several rt-PCR assays for Nm target the capsule transport gene, ctrA. However, over 16% of meningococcal carriage isolates lack ctrA, rendering this target gene ineffective at identification of this sub-population of meningococcal isolates. The Cu-Zn superoxide dismutase gene, sodC, is found in Nm but not in other Neisseria species. To better identify Nm, regardless of capsule genotype or expression status, a sodC-based TaqMan rt-PCR assay was developed and validated. Standard curves revealed an average lower limit of detection of 73 genomes per reaction at cycle threshold (C(t)) value of 35, with 100% average reaction efficiency and an average R(2) of 0.9925. 99.7% (624/626) of Nm isolates tested were sodC-positive, with a range of average C(t) values from 13.0 to 29.5. The mean sodC C(t) value of these Nm isolates was 17.6±2.2 (±SD). Of the 626 Nm tested, 178 were nongroupable (NG) ctrA-negative Nm isolates, and 98.9% (176/178) of these were detected by sodC rt-PCR. The assay was 100% specific, with all 244 non-Nm isolates testing negative. Of 157 clinical specimens tested, sodC detected 25/157 Nm or 4 additional specimens compared to ctrA and 24 more than culture. Among 582 carriage specimens, sodC detected Nm in 1 more than ctrA and in 4 more than culture. This sodC rt-PCR assay is a highly sensitive and specific method for detection of Nm, especially in carriage studies where many meningococcal isolates lack capsule genes.

Epidemiologic investigation and targeted vaccination initiative in response to an outbreak of meningococcal disease among illicit drug users in Brooklyn, New York.

BACKGROUND: An outbreak of serogroup C meningococcal disease that involved illicit drug users and their contacts occurred in Brooklyn, New York, during 2005 and 2006. METHODS: The objectives of this study were to identify the population at risk for meningococcal disease, describe efforts to interrupt disease transmission, and assess the impact of a vaccine initiative. Descriptive and molecular epidemiological analysis was used to define the extent of the outbreak and the common risk factors among outbreak-related cases. A vaccine initiative that used community-based service providers was targeted to illicit drug users and their close contacts. The vaccine initiative was assessed through cessation of outbreak-related cases and the reduction in carriage rate. RESULTS: The investigation identified 23 outbreak-related cases of serogroup C meningococcal disease; 17 isolates were indistinguishable and 4 isolates were closely related according to pulsed-field gel electrophoresis. Two additional culture-negative cases had epidemiological links to laboratory-confirmed cases. The median age of patients with outbreak-related cases was 41 years, and 19 (83%) of 23 patients reported an association with illicit drug use. There were 7 outbreak-related deaths. Vaccination was administered to 2763 persons at 29 community locations, including methadone treatment centers, syringe-exchange programs, and soup kitchens. Three additional cases of meningococcal disease due to strains with the same pulsed-field gel electrophoresis pattern were identified after the vaccination initiative. CONCLUSIONS: Community-based outbreaks of meningococcal disease are difficult to control, and the decision to vaccinate is not straightforward. Current national guidelines for implementing a vaccination campaign are not strict criteria and cannot be expected to accommodate the myriad of factors that occur in community-based invasive meningococcal disease outbreaks, such as the inability to enumerate the population at risk.

Emergence of ciprofloxacin-resistant Neisseria meningitidis in North America.

We report on three cases of meningococcal disease caused by ciprofloxacin-resistant Neisseria meningitidis, one in North Dakota and two in Minnesota. The cases were caused by the same serogroup B strain. To assess local carriage of resistant N. meningitidis, we conducted a pharyngeal-carriage survey and isolated the resistant strain from one asymptomatic carrier. Sequencing of the gene encoding subunit A of DNA gyrase (gyrA) revealed a mutation associated with fluoroquinolone resistance and suggests that the resistance was acquired by means of horizontal gene transfer with the commensal N. lactamica. In susceptibility testing of invasive N. meningitidis isolates from the Active Bacterial Core surveillance system between January 2007 and January 2008, an additional ciprofloxacin-resistant isolate was found, in this case from California. Ciprofloxacin-resistant N. meningitidis has emerged in North America.