Assessment of a two-step nucleic acid amplification assay for detection of Neisseria meningitidis followed by capsular genogrouping

Immediate prevention of meningococcal disease relies in part on the prompt treatment with antibiotics of household and other close contacts of cases; however intervention with effective vaccination relies on identification of serogroup-causing strains. Parenteral antibiotic for patient with suspected meningococcal disease before hospital admission is currently recommended. Laboratory standard methods are hindered by failure to detect bacteria by this medical approach to improve patient prognosis. We assessed two polymerase chain reaction (PCR) assays to detect (crgA) and define the serogroups (siaD, orf-2, and ctrA) of Neisseria meningitidis in 120 cerebrospinal fluid (CSF) samples from positive cases (culture or antigen detection or direct smear). The PCR sensitivity for the identification of N. meningitidis was 100 percent (95 percent confidence interval, CI, 96-100 percent) compared to a sensitivity of 46 percent for culture (95 percent CI 37-55 percent), 61 percent for latex agglutination test (95 percent CI 52-70 percent), and 68 percent for Gram stain (95 percent CI 59-76 percent); PCR specificity was 97 percent (95 percent CI 82-100 percent). PCR correctly identified the serogroups A, B, C, W135, Y, and X in CSF samples with a sensitivity of 88 percent (95 percent CI 80-93 percent); the primer sets were 100 percent specific. The introduction of PCR-based assays shall increase laboratory confirmed cases, consequently enhancing surveillance of meningococcal disease.

Diagnosis of Streptococcus pneumoniae meningitis by polymerase chain reaction amplification of the gene for pneumolysin

Diagnosis of bacterial meningitis has long been based on classical methods of Gram stain, serological tests, and culture of cerebrospinal fluid (CSF). The performance of these methods, especially culture and direct smear, is thwarted by failure to detect bacteria following administration of antimicrobial agents and reluctance to performance lumbar punctures at admission. Indeed, patients with meningitis frequently receive antibiotics orally or by injection before the diagnosis is suspected or established. Thus an alternative method has become necessary to help clinicians and epidemiologists to management and control of bacterial meningitis. We evaluate the application of a polymerase chain reaction-based (PCR) assay for amplification of pneumolysin gene (ply) to diagnosis of Streptococcus pneumoniae meningitis. The PCR assay sensitivity for CSF was 96 percent (95 percent confidence interval, CI, 90-99 percent) compared to a sensitivity of 59 percent for culture (95 percent CI 49-69 percent), 66 percent for Gram stain (95 percent CI 56-74 percent), and 78 percent for latex agglutination test (95 percent CI 69-86 percent); PCR specificity was 100 percent (95 percent CI 83-100 percent). PCR results were available within 4 h of the start of the assay. This molecular approach proved to be reliable and useful to identify this bacterium compared with other classical laboratory methods for identification of bacterial meningitis pathogens.