Methods: 100 CSF and blood samples were collected from suspected /clinically diagnosed cases of meningitis over a period of 1year.CSF samples were processed by conventional and molecular methods.The objectives of the study were:To identify the common bacterial etiological agent;to assess the utility of PCR in diagnosis of acute bacterial meningitis and to know the antimicrobial susceptibility pattern.
Results: Out of 100 samples, maximum cases presented with frank meningeal signs (45%) followed by clinically suspected cases (42%).Microscopic examination, CSF culture, PCR detected 7%,24% and 40% positive cases respectively. 13% were detected positive by blood culture. The positivity on CSF culture was comparable to the study done by R Mani et al (40.5%).The predominant pathogens isolated were K.pneumoniae (37.5%) followed by Streptococcus pneumoniae and Acinetobacter spp (each 16.67%). PCR positive followed by Gene sequencing revealed Pseudomonas aeruginosa (34.78%) as the predominant pathogen. Culture is considered as the gold standard. However, it fails to identify fastidious organisms and often gives false negative results. Therefore, the gold standard was modified to consider parameters like-clinical signs of meningitis, CSF biochemistry indicative of meningitis and CSF positive on any 1 microbiological test (CSF staining/CSF culture/Blood culture). The performance of PCR was then improved to Sensitivity (67.74%); Specificity- (72.46%); Diagnostic accuracy-(71%); PPV- 52.50% and NPV- 83.34%. The kappa coefficient-0.372 showed a fair agreement, considering the modified gold standard. This criteria was also used in study done by Welinder-Olsson et al.
Conclusion: Gram negative enteric bacteria were the most common etiology reported by both the methods. PCR could detect more cases than conventional culture method indicating its utility in the diagnosis of acute meningitis. Apart from microbiological parameters, clinical and other laboratory parameters should be considered to achieve a precise diagnosis.