Detection of bacterial pathogens in Mongolia meningitis surveillance with a new real-time PCR assay to detect Haemophilus influenzae.

Since the implementation of Haemophilus influenzae (Hi) serotype b vaccine, other serotypes and non-typeable strains have taken on greater importance as a cause of Hi diseases. A rapid and accurate method is needed to detect all Hi regardless of the encapsulation status. We developed 2 real-time PCR (rt-PCR) assays to detect specific regions of the protein D gene (hpd). Both hpd assays are very specific and sensitive for detection of Hi. Of the 63 non-Hi isolates representing 21 bacterial species, none was detected by the hpd #1 assay, and only one of 2 H. aphrophilus isolates was detected by the hpd #3 assay. The hpd #1 and #3 assays detected 97% (229/237) and 99% (234/237) of Hi isolates, respectively, and were superior for detection of both typeable and non-typeable Hi isolates, as compared to previously developed rt-PCR targeting ompP2 or bexA. The diagnostic sensitivity and specificity of these rt-PCR assays were assessed on cerebrospinal fluid specimens collected as part of meningitis surveillance in Ulaanbaatar, Mongolia. The etiology (Neisseria meningitidis, Hi, and Streptococcus pneumoniae) of 111 suspected meningitis cases was determined by conventional methods (culture and latex agglutination), previously developed rt-PCR assays, and the new hpd assays. The rt-PCR assays were more sensitive for detection of meningitis pathogens than other classical methods and improved detection from 50% (56/111) to 75% (83/111). The hpd #3 assay identified a non-b Hi that was missed by the bexA assay and other methods. A sensitive rt-PCR assay to detect both typeable and non-typeable Hi is a useful tool for improving Hi disease surveillance especially after Hib vaccine introduction.

Childhood bacterial meningitis in Ulaanbaatar, Mongolia, 2002-2004.

BACKGROUND: Childhood bacterial meningitis is severe and largely preventable by vaccination. Few data on childhood bacterial meningitis in Northeast and Central Asia exist. Our aim was to determine the incidence and etiology of childhood bacterial meningitis in Ulaanbaatar, Mongolia. METHODS: We conducted prospective, population-based, active hospital surveillance for clinical meningitis in children 2 months to 5 years of age. Clinical data, blood, and cerebrospinal fluid were collected according to a standard protocol. Laboratory testing was performed at 2 reference laboratories in Ulaanbaatar. RESULTS: From February 2002 to January 2005, 201 suspected meningitis cases were identified in residents of Ulaanbaatar. The average annual incidence rate for confirmed and probable bacterial meningitis (cases with culture-negative, purulent cerebrospinal fluid) was 68 cases per 100,000 children aged 2 months to 5 years. The average annual incidence rate of confirmed cases was 28 cases per 100,000 children for Haemophilus influenzae type b meningitis, 11 cases per 100,000 children for pneumococcal meningitis, and 13 cases per 100,000 children for meningococcal meningitis. Adjusting for cases without complete cerebrospinal fluid information and culture-negative, probable bacterial cases, the estimated incidence rate was 40 cases per 100,000 children for H. influenzae type b meningitis, 15 cases per 100,000 children for pneumococcal meningitis, and 17 cases per 100,000 children for meningococcal meningitis. CONCLUSION: H. influenzae type b is the leading cause of childhood bacterial meningitis in Ulaanbaatar, and the incidence rate is higher than that reported from other Asian countries. These data supported the recent introduction of H. influenzae type b conjugate vaccine in Mongolia. Ongoing surveillance will monitor the impact of the vaccine.