Pattern of Pathogens and Utility of Latex Agglutination Tests in Bacterial Meningitis

Abstract

The etiology of bacterial meningitis has changed significantly in the last decade, especially in the developed countries. 1 The classic bacterial pathogens of meningitis have been Haemophilus influenzae B, Neisseria meningitidis, Streptococcus pneumoniae, Escherichia coli and group B Streptococcus. Their relative importance varies according to the location and population characteristics. 2 In 1984, Babiker et al. reported 140 cases of bacterial meningitis from Riyadh, of which 90% were children under five years of age. The most common bacterial isolates in that study were E. coli from neonates and S. pneumoniae from children >2 months of age. 3 Later, an 11-year study reported H. influenzae B as a significant isolate in cases of meningitis in Riyadh, and recommended nationwide immunization against this pathogen. 4 Following an outbreak of meningococcal meningitis in 1988 in Makkah, a program of free nationwide vaccination against N. meningitides serogroup A and C has been in force. 5 Cost containment pressures have driven policy makers to critically appraise recommendations for latex agglutination tests (LAT) on cerebrospinal fluid (CSF). 6 Savings from their use and the fact that there is no change of empirical antibiotic therapy even after a positive test, have been cited in favor of abandoning the routine use of LAT. [6][7][8] In our laboratory, LAT is performed only in cases where the CSF cell count is elevated (>5 cell/mm 3 ) and the gram stain is negative, or when clinical suspicion is strong and prior antibiotic therapy is expected to reduce the yield of culture. In our institution, we process an average of 20 specimens of CSF/week. One LAT costs approximately 16 Saudi Riyals ($4.2). The saving/week is estimated at 19x16 =SR302 ($80).Aiming to address future concerns with the changing microbial pathogens of bacterial meningitis and problems with newer diagnostic implements, we undertook this study to determine the pattern of classical and non-classical bacterial isolates from CSF specimens, the usefulness of the gram stain and use of the LAT, and their implications on clinical decisions. It is pertinent to mention that this study is related to a tertiary care center, and by no means reflecting what happens in hospitals managing cases of community acquired meningitis. Materials and MethodsThe study sample consisted of 4180 CSF specimens, which were received during a four-year period (January 1995 to December 1998) by the Microbiology Laboratory at the King Khalid University Hospital, a 750-bed tertiary care general teaching hospital in Riyadh. All patients were highly suspected to have meningitis. Data were obtained from the laboratory records. In the vast majority of patients, a single CSF specimen was obtained from each patient. In a few cases, more than one specimen was obtained. Biochemical and Hematological TestsProtein and glucose levels were determined using the Dade autoanalyzer. Cerebrospinal cell counting was performed with the Neubaur Chamber. CSF specimen with protein levels of >45 mg/dL, and/o...

Methods for Rapid Diagnosis of Meningitis Etiology in Adults

“…Latex agglutination is relatively inexpensive and rapid (∼10 min) [2,6,[55][56][57][58]. Sensitivity varies by microorganism and manufacturer -78-100% for H. influenzae, 59-100% for S. pneumoniae, 69-100% for S. agalactiae and 50-93% for N. meningitis [4,52].…”