Human meningitis due to Streptococcus suis in Lomé, Togo: a case report

A 32-year-old man working as a carpenter in Lomé, Togo, was admitted in August 2015 to the University Hospital Campus of Lomé for a 3 day history of severe headaches, vomiting, fever, and intense agitation (Table 1). He had no particular medical history and no risk factors for immunodeficiency. At admission, the body temperature was of 36.4 °C, and the general state was acceptable, with a correct conservation of consciousness. The neurological examination did not show any sign of motor or sensitive defect, of cranial nerve dysfunction or cerebellar symptoms. There was no hearing or skin abnormalities, no obvious neck stiffness, and the rest of the clinical examination was normal. Acute meningeal hemorrhage was evocated as the initial diagnosis. Cranial computed tomography could not be performed and a symptomatic treatment associating antalgic, antipyretic, and anticonvulsant medication was initiated. At the second day of admission, the patient was febrile, agitated, and still suffered from severe headaches and vomiting. The neck had become stiff, and Kernig and Brudzinski signs were positive. The meningeal signs led to the realization of a lumbar puncture, which yielded a turbid cerebrospinal fluid (CSF) concluding to the diagnosis of bacterial meningitis. An empiric intravenous antibiotic treatment associating ceftriaxone (2 g, 2×/d for 24 h then 1 g, 2×/d), ofloxacin (200 mg, 3×/d), and metronidazole (500 mg, 2×/d) was started.

CSF analysis showed 2,800 leukocytes/mm³ (65 % lymphocytes and 35 % neutrophils), a protein concentration of 1.8 g/L, and a glucose concentration of 0.47 g/L (2.6 mmol/L) with a plasma glucose concentration of 1.41 g/L (7.8 mmol/L; ratio = 0.33). Gram staining did not reveal any microorganism. Blood and CSF cultures, after 48 h and 24 h of incubation, respectively, grew small beta-hemolytic colonies on horse blood agar plates. The bacteria were catalase negative, gram-positive cocci, in chains or in pairs. They were identified as S. suis (score 2.56) by MALDI-TOF (Matrix Assisted Laser Desorption Ionisation Time Of Flight) spectrometry (BrukerTM) and as S. suis serotype 1 (97 % probability) by VITEK 2 Gram-positive card system (bioMérieux, Marcy l’Etoile, France). Slide agglutination with type-specific hyperimmune serum and specific multiplex PCR identified the isolate as S. suis serotype 2, indicating a serotype misidentification by the automated card system, and concluding, together with Multi-Locus Sequence Typing [3‐5], to an infection due to S. suis serotype 2, Sequence-Type (ST) 1, one of the most virulent and frequently isolated clone all over the world [1, 6]. Antimicrobial drug-susceptibility testing performed according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommendations characterized the strain as susceptible to penicillin (Minimum inhibitory concentration (MIC) < =0.25 mg/L), erythromycin, clindamycin, levofloxacin, and linezolid and resistant to tetracycline.

After S. suis was identified, the patient reported working as a pork butcher every week-end. The patient did not have any sign or symptoms of endocarditis, and the antibiotic treatment was replaced by ampicillin (2 g, 3×/d) and gentamicin (80 mg, 2×/d) for 7 days. While the patient was receiving treatment for 1 day, vertigo and tinnitus developed, for which he received adjunctive corticoid therapy and the treatment was completed with no particular adverse events. Hearing disorders, especially hearing loss, are the most common sequelae of S. suis infections and affect more than 50 % of patients who survive meningitis [2]. In that case, hearing disorders evolved into severe hearing loss in the left and right ears (80 dB), and the patient was still suffering from tinnitus 9 months after the diagnosis. One year later, tinnitus had disappeared and the patient’s auditory function had improved from severe to moderate hearing loss.