infectious diseases
Meningococcal Diseases
Diagnosis of Meningococcal Diseases
Gram stain and culture Sometimes nucleic acid–based testing (NAAT) such as polymerase chain reaction (PCR) Neisseriaare small, gram-negative diplococci readily identified with Gram stain and by other standard bacteriologic identification methods. Serologic methods, such as latex agglutination and coagglutination tests, allow rapid presumptive diagnosis ofN. meningitidisin blood, cerebrospinal fluid, synovial fluid, and urine. However, both positive and negative results should be confirmed by culture. PCR testing of cerebrospinal fluid, blood, and other normally sterile sites forN. meningitidisis more sensitive and specific than culture and may be useful when the cerebrospinal fluid Gram stain is negative and when prior antibiotic administration interferes with isolating the organism. Because meningococci and gonococci appear similar on Gram stain, meningococcal urethritis should be considered if the urethral discharge shows gram-negative diplococci, but the NAAT is negative for gonococci; this situation requires culture of the urethral discharge to identify theNeisseriaspecies causing the infection (seeDiseases Characterized by Urethritis and Cervicitisfrom the CDC). 