|Year : 2014 | Volume
| Issue : 2 | Page : 179-180
Brain abscess due to Streptococcus oralis in an immunocompetent patient
R Solanki1, S Subramanian1, V Lakshmi1, V Bhushanam2, A Kumar2
1 Department of Microbiology, Nizam's Institute of Medical Sciences, Hyderabad, Andhra Pradesh, India
2 Department of Neurosurgery, Nizam's Institute of Medical Sciences, Hyderabad, Andhra Pradesh, India
|Date of Submission||21-May-2013|
|Date of Acceptance||22-Oct-2013|
|Date of Web Publication||2-Apr-2014|
Department of Microbiology, Nizam's Institute of Medical Sciences, Hyderabad, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
A bacteriologically proven case of brain abscess, due to Streptococcus oralis is being reported in a 12-year-old girl who is a known case of congenital heart disease. The patient presented with fever, headache and vomiting. Pus cultures yielded S. oralis.
Keywords: Brain abscess, Streptococcus oralis, viridans group streptococci
|How to cite this article:|
Solanki R, Subramanian S, Lakshmi V, Bhushanam V, Kumar A. Brain abscess due to Streptococcus oralis in an immunocompetent patient. Indian J Med Microbiol 2014;32:179-80
|How to cite this URL:|
Solanki R, Subramanian S, Lakshmi V, Bhushanam V, Kumar A. Brain abscess due to Streptococcus oralis in an immunocompetent patient. Indian J Med Microbiol [serial online] 2014 [cited 2019 Dec 8];32:179-80. Available from: http://www.ijmm.org/text.asp?2014/32/2/179/129817
| ~ Introduction|| |
The viridans group streptococci (VGS) are a haeterogeneous group of organisms that colonize oral mucosa, gastrointestinal and genitourinary tracts. In general, VGS is considered to be of low pathogenic potential in immunocompetent individuals. However, in certain patient populations, VGS can cause invasive disease, such as endocarditis, intra-abdominal infection and shock. The name 'viridans' is somewhat of a misnomer, as many species do not produce any haemolysis on blood agar. 
| ~ Case Report|| |
We report a case of a 12-year-old girl who is a k/c/o congenital heart disease (CHD) (single ventricle, severe polycyclic aromatic hydrocarbons and moderate mitral regurgitation [MR]) presented with the complaints of headache and fever for 1 week duration and history of vomiting. On examination, patient was drowsy, but arousable (E3V5M6). Fundus examination showed bilateral papilloedema. She was not on penicillin prophylaxis.
In view of the headache and vomiting, the patient was admitted and further investigated. A computerized tomography (CT) of the head showed intracerebral abscess involving right frontal lobe [Figure 1]. Haematological investigations revealed a haemoglobin level of 13.4 g/dl, a platelet count of 3.6 lakh/dl and a white cell count of 14,9000/mm 3 . Blood biochemistry was normal. To identify focus of infection ENT examination and echocardiogram (ECHO) was done. ENT examination revealed bad oral hygiene and ECHO showed single ventricle, moderate MR, severe pulmonary hypertension, probable bicuspid aortic valve with good left ventricle function and no vegetation.
|Figure 1: Computerized tomography scan of brain showing 6 cm × 5 cm size hypodense lesion with ring enhancement and perilesional oedema in right frontal lobe|
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With a presumptive diagnosis of frontal lobe pyogenic abscess, the patient was administered ceftriaxone 500 mg intravenous (IV) BD, amikacin 500 mg IV OD and metronidazole 100 ml IV OD along with other supportive therapy. Patient underwent right frontal bur hole procedure and around 20 ml of pus was aspirated.
Pus was sent to the microbiology department for aerobic and anaerobic culture and Gram stain. Gram's stain of pus shows plenty of pus cells with Gram-positive cocci up to 1 μm in pairs and short chains. Culture was done on chromogenic media, blood agar at 37°C in ambient air and chocolate agar at 37°C under 5-10% CO 2 . Culture showed growth of tiny non-haemolytic colonies on blood agar after 48 h of incubation [Figure 2]. The isolate was identified as Streptococcus oralis with the ID strep panel. (Mini API, BioMerieux, Marcy I'Etoile-France) (99.5% probability). Antimicrobial susceptibility was done with ATB strep (mini API Biomerieux, Marcy I'Etoile-France). Isolate was sensitive to cotrimoxazole, tetracycline, levofloxacin and vancomycin, and resistant to penicillin, cefotaxime, erythromycin and gentamicin.
|Figure 2: Left side: tiny non-haemolytic colonies on 5% sheep blood agar. Right side: pinpoint green colonies on chromogenic media|
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After culture and sensitivity report, vancomycin was started (30 mg/kg body weight 12 hourly). Patient improved with this therapy and was discharged on levofloxacin (250 mg twice a day) for 15 days. The patient had a good response to this therapy and became afebrile. Post-treatment CT scan was normal and doing well on follow-up after 2 weeks.
The diagnosis of VGS is difficult since the taxonomic classification and species names may change due in time. VGS are classified into 5 groups (Sanguinis, Mitis, Mutans, Salivarius, Anginosus) according to biochemical reactions and 16S ribosomal ribonucleic acid sequencing. 
Observation of Gram-positive cocci microscopically, detection of optochin-resistant and bile insoluble colonies with few exceptions are the further important steps in laboratory diagnosis of VGS. Identification of VGS to the species level can be done by using biochemical reactions, automated diagnostic systems and molecular methods. Antibiotic susceptibility testing of VGS is of outmost importance as penicillin and erythromycin resistance is on rise. 
S. oralis is a significant agent of infective endocarditis and a major pathogen in patients with attenuated host defence mechanisms.  However it is not a common causative agent for brain abscess.  First case of meningitis due to S. oralis was reported in a 12-year-old girl child following extraction of a deciduous canine tooth  Konemann ref.  In this case, patient had bad oral hygiene however there was no history of tooth extraction.
The mechanisms by which S. oralis causes this wide range of infections are as yet unclear, but the sialidase produced by this bacterium has been proposed as contributing towards the pathogenicity. 
Regarding the portal of entry, brain abscess is almost always secondary to a focus of suppuration elsewhere in the body and may develop either by a contiguous focus of infection, head trauma, or haematogenous spread from a distant focus. CHD with left to right shunts may also predispose to brain abscess. 
Predisposing condition for viridians streptococcal brain abscess include congestive heart failure, chronic otitis media, head injury with cerebrospinal fluid rhinorrhoea, sinusectomy and craniotomy followed by ventriculoperitoneal shunt placement. 
Predisposing factors in our case are CHD, but without infective endocarditis and bad oral hygiene. Viridans streptococci are the prevalent pathogens with haematogenous spread secondary to cardiogenic origin or from infection of paranasal sinusitis.  Mortality of patients infected with VGS is less due to the low virulence of VGS. 
To the best of our knowledge this is a first case of brain abscess due to S. oralis in an immunocompetent patient, due to its low virulence and timely management leads to uneventful recovery in this case.
| ~ References|| |
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[Figure 1], [Figure 2]