What is the role of CSF culture in the workup of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Answer

Culture of the CSF yields the most specific information; unfortunately, that information is not immediately available. CSF cultures are positive within 48 hours in approximately 75-80% of cases, with a sensitivity of 95% and a specificity of 99%. Hib in culture can be considered the cause of meningitis most confidently when the organism was found on Gram stain of the initial CSF.

A positive culture is the most valuable single test in confirming the diagnosis of bacterial meningitis. Although in some instances a false-positive CSF culture is obtained, these cultures tend to contain skin commensals such as Staphylococcus alba, and a false-positive CSF culture containing Hib is likely very rare. Moreover, ascribing such a positive culture to contamination is so risky that the physician rarely has any choice other than to complete the usual course of therapy for meningitis.

A positive CSF culture provides the additional benefit of permitting the determination of antimicrobial sensitivity in subcultures of recovered organisms and thus allowing the adjustment of antibiotic selection. However, several additional days after recovery of the organism may be necessary to obtain such results.


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