Ans. is 'c' i.e., Nasopharyngeal swab Best site for specimen collection for meningococci :? For cases - CSF (by lumbar puncture) For carriers - Nasopharyngeal swab As CSF is not there in options, examiner is, most probably, asking about specimen in carrier. Laboratory diagnosis of meningococcal infection Specimens CSF - Divided into three poions : One poion is centrifuged and Gram stained smears are prepared from the deposit The second poion is inoculated on blood agar or chocolate agar plates. The third poion of CSF is incubated overnight and than subcultured on chocolate agar. Blood - for culture in patients with meningococcemia and early meningitis. Nasopharyngeal swab - for carriers Petechial lesions - In cases of meningococcemia. Autopsy specimens - from meninges, lateral ventricle, surface of brain or spinal cord. Smear will show Gram negative diplococci inside the polymorphs but often extracellularly also. They are arranged in pairs, with the adjacent sides flattened. Capsulated nonmotile Transpo medium - Stua's medium Culture Blood agar, chocolate agar and Muller-Hinton starch casein hydrolysate agar are the media commonly used for culturing meningococci. Modified Thayer - Main (with vancomycin, colistin and nystatin) is a useful selective medium. Serology Antibodies to meningococcal polysaccharides can be measured by latex agglutination or hemagglutination tests or by their bactericidal activity.