Underestimation of Invasive Meningococcal Disease in Italy.

Chiara Azzari,Daniele Serranti,Giuseppe Indolfi,Silvia Ricci,Maria Moriondo,Massimo Resti,Francesco Nieddu,Leila Bianchi,Giovanni Maria Poggi,Clementina Canessa

doi:10.3201/eid2203.150928

Abstract

Knowing the incidence of invasive meningococcal disease (IMD) is essential for planning appropriate vaccination policies. However, IMD may be underestimated because of misdiagnosis or insufficiently sensitive laboratory methods. Using a national molecular surveillance register, we assessed the number of cases misdiagnosed and diagnoses obtained postmortem with real-time PCR (rPCR), and we compared sensitivity of rPCR versus culture-based testing. A total of 222 IMD cases were identified: 11 (42%) of 26 fatal cases had been misdiagnosed or undiagnosed and were reclassified as IMD after rPCR showed meningococcal DNA in all available specimens taken postmortem. Of the samples tested with both rPCR and culture, 58% were diagnosed by using rPCR alone. The underestimation factor associated with the use of culture alone was 3.28. In countries such as Italy, where rPCR is in limited use, IMD incidence may be largely underestimated; thus, assessments of benefits of meningococcal vaccination may be prone to error.

Highlights

Knowing the incidence of invasive meningococcal disease (IMD) is essential for planning appropriate vaccination policies
N. meningitidis is a fastidious pathogen that frequently undergoes autolysis, and its growth can be inhibited by a single dose of antimicrobial drug therapy, even in cases when the patient dies from the infection [9]
No culture-based test was performed for the 11 patients whose IMD diagnosis was postmortem; instead, diagnosis was performed by using real-time PCR (rPCR) on autoptic specimens, including blood, cerebrospinal fluid (CSF), and formalin-fixed tissue samples

Summary

Introduction

Knowing the incidence of invasive meningococcal disease (IMD) is essential for planning appropriate vaccination policies. The underestimation factor associated with the use of culture alone was 3.28 In countries such as Italy, where rPCR is in limited use, IMD incidence may be largely underestimated; assessments of benefits of meningococcal vaccination may be prone to error. N. meningitidis is a fastidious pathogen that frequently undergoes autolysis, and its growth can be inhibited by a single dose of antimicrobial drug therapy, even in cases when the patient dies from the infection [9] Molecular tests such as real-time PCR (rPCR) are used alone or in combination with culture to diagnose IMD and determine the serogroup of the implicated pathogen [5,10]. By using data from Italy’s national register for molecular surveillance of invasive bacterial disease, we attempted to identify factors contributing to the underestimation of IMD, including suddenly fatal cases and the use of different diagnostic procedures

Methods

Results

Conclusion