Non-gonococcal, non-meningococcal neisseriae, often called the ‘non-pathogenic’ neisseriae, are commonly found as saprophytes in the upper respiratory tract and rarely cause disease. Isolation from blood cultures has usually been associated with serious infections such as endocarditis, septicemia or meningitis . In this report we present a patient with endocarditis due to Neisseria mucosa.
A 26-year-old male was admitted to Hacettepe University Hospital with 20 days history of fever (39°C), malaise, palpitation, sweating, dyspnea, abdominal pain and arthralgia of knee and ankle. He had developed frequent hiccups 2 weeks before his admission, and he had painful echymosis on the thenar surface of his fingers. He had received no medical treatment.
The history included acute rheumatic fever 7 years before for which he was receiving benzathine penicillin prophylaxis. On examination, he was acutely ill, he had prominent hiccups, his temperature was 38.8°C, his blood pressure was 110/55 mmHg and his pulse rate was 84/min. He had pectus carinatus, left upper quadrant abdominal tenderness and hepatosplenomegaly. A diastolic decrescendo murmur at the apex and a holosystolic murmur at the left border of the sternum were heard on cardiac auscultation. A purpuric, painful skin lesion, 2 cm in diameter, was found on the anterior surface of the fourth finger of his left hand.
Abnormal laboratory test results comprised the following: hemoglobin 11.7 g/dL, leukocyte count 24,300/mm3, erythrocyte sedimentation rate 84 mm/h, C-reactive protein 58 U/mL (normal 12 U/mL), alanine aminotransferase 44 U/L, aspartate aminotransferase 42 U/L, and microscopic hematuria. The X-ray showed cardiac enlargement. Echocardiography revealed moderate aortic and mitral and minimal tricuspid valve insufficiency and increased mitral valve thickness. By the Duke criteria  for diagnosis of infective endocarditis, five minor criteria (predisposing heart condition, fever, immunologic phenomena, vascular phenomena, suggestive echocardiogram findings) were consistent with definite infective endocarditis, and intravenous penicillin and gentamicin therapy was started.
On the fifth day of hospitalization, cultures of all of seven blood samples taken on the day of admission showed growth of Gram-negative cocci, and the patient was placed on ceftriaxone 2 g/day intravenously instead of the gentamicin-containing regimen. The isolates were identified as Neisseria mucosa, by the characteristic biochemical findings: oxidase, catalase and nitrate positive; producing acid from glucose, sucrose, and maltose but not from lactose .
Antimicrobial sensitivity tests showed resistance to benzylpenicillin (MIC 2 mg/L), and sensitivity to ceftriaxone (MIC 0.125 mg/L). The minimum inhibitory concentration values of other antibiotics were: ampicillin 1 mg/L, cephalothin 2 mg/L, gentamicin 0.5 mg/L, and ciprofloxacin 0.03 mg/L.
On the ninth day of hospitalization, multiple splenic infarcts were detected with abdominal ultrasound and the patient underwent splenectomy. After 11 days of ceftriaxone therapy no fever was observed but peripheral embolism continued, affecting upper and lower limbs. A new echocardiogram showed a 2.9 × 1.4 cm vegetation on the posterior part of the aortic valve and on the 17th day aortic and mitral valve replacement was performed. After a 6-week course of intravenous ceftriaxone he was discharged from hospital. No growth was obtained from the received valves or subsequent blood cultures. He was well 1, 2, 4 and 8 months after completion of his therapy and normal prosthetic valve function was demonstrated by echocardiography.
This case corresponds to cases of N. mucosa endocarditis in the literature, with the exception of the aortic valve involvement. Only one previous case showed certain aortic valve involvement  and, recently, another patient had possible involvement of this valve . Non-gonococcal, non-meningococcal Neisseria species existing as respiratory commensals in humans can occasionally cause serious infection, not only in immunocompromised hosts but also in immunocompetent individuals, as in our case. As mentioned in Ingram's review , the optimal antibiotic treatment regimen and its duration for N. mucosa endocarditis are unknown. This is the first case treated with ceftriaxone. As in our case, N. mucosa may show resistance to penicillin/gentamicin therapy, and serious embolic complications may be seen under this regimen. We elected to use ceftriaxone because of the lower MIC value for the organism and proven activity against Neisseria species in other infections . We suggest ceftriaxone therapy as an alternative antibiotic choice in cases of N. mucosa endocarditis.