Meningitis caused by Streptococcus suis

Abstract

Background:In most countries with full-service microbiology services, streptococcus-like organisms visualized in a gram-stained smear of cerebrospinal fluid (CSF) from patients presenting with meningitis syndrome would be assumed to be Streptococcus pneumoniae.  However, in many areas of the world, predominantly in Southeast Asia, the organism may be Streptococcus suis.  Although initial antimicrobial treatment is similar, additional treatment for specific co-morbidities, such as hearing loss, may be needed.  This case, involving an adult male who presented with signs and symptoms of meningitis, describes the appropriate laboratory test procedures used to make the diagnosis and the subsequent patient management strategy.

Case presentation:  A previously healthy 69-year old rice farmer was admitted to the hospital with a one day history of fever, headache, neck stiffness, and altered consciousness.  Initial laboratory studies were consistent with meningitis but the CSF Gram stain did not reveal any organisms.  Blood cultures obtained at admission grew alpha-hemolytic, optochin-resistant colonies consistent with Streptococcus suis, and the identification was confirmed by MALDI-TOF performed at another laboratory.  Unusually, the isolate was penicillin resistant.  The patient received 4 g/day ceftriaxone and dexamethasone (to mitigate deafness) for 10 days and was discharged to home with moderate deafness but no residual infection. 

Conclusion: Diagnosis of meningitis should include both blood cultures and CSF cultures obtained before any antibiotics are administered.  In some patient populations such as those in Southeast Asia or if there is history of contact with pigs or raw pork, S. suis should be considered.