Parvimonas micra: A potential causative pathogen to consider when diagnosing odontogenic brain abscesses
- Departments of Neurosurgery, Puerta de Hierro University Hospital, Madrid, Spain.
- Departments of Internal Medicine, Puerta de Hierro University Hospital, Madrid, Spain.
- Neurophysiology, Puerta de Hierro University Hospital, Madrid, Spain.
Neurophysiology, Puerta de Hierro University Hospital, Madrid, Spain.
DOI:10.25259/SNI_20_2020Copyright: © 2020 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Ruth Prieto, Alejandro Callejas-Díaz, Rasha Hassan, Alberto Pérez de Vargas, Luis Fernando López-Pájaro. Parvimonas micra: A potential causative pathogen to consider when diagnosing odontogenic brain abscesses. 06-Jun-2020;11:140
How to cite this URL: Ruth Prieto, Alejandro Callejas-Díaz, Rasha Hassan, Alberto Pérez de Vargas, Luis Fernando López-Pájaro. Parvimonas micra: A potential causative pathogen to consider when diagnosing odontogenic brain abscesses. 06-Jun-2020;11:140. Available from: https://surgicalneurologyint.com/surgicalint-articles/10068/
Background: Brain abscess is a life-threatening entity which requires prompt and long-term antibiotic therapy, generally associated with surgical drainage, and eradicating the primary source of infection. Parvimonas micra (Pm) has only been reported once before as the lone infecting organism of an orally originated, solitary brain abscess. Diagnosing brain abscesses caused by this Gram-positive anaerobic coccus, constituent of the oral cavity flora, is challenging, and an optimal treatment regimen has not been well established. We report the diagnosis and successful treatment of a Pm caused odontogenic brain abscess.
Case Description: A 62-year-old immunocompetent male with a right-parietal brain abscess presented with headache and seizures. He was started on empirical antibiotic therapy and subsequently underwent surgical drainage. The only source of infection found was severe periodontitis with infected mandibular cysts. Thus, tooth extraction and cyst curettage were performed 1 week after brain surgery. Cultures of brain abscess fluid were negative, but amplification of bacterial 16S ribosomal RNA (rRNA) with polymerase chain reaction demonstrated Pm. After 3 weeks of intravenous ceftriaxone and metronidazole, the patient was switched to oral metronidazole and moxifloxacin for 6 weeks.
Conclusions: This case highlights the potential risk of untreated dental infections causing brain abscesses. Pm should be considered as a possible pathogen of odontogenic brain abscesses despite its presence usually not being detected by standard bacterial cultures. Therefore, 16S rRNA gene sequencing analysis is strongly recommended for bacterial identification before defining brain abscesses as cryptogenic.
Keywords: 16S rRNA analysis, Brain abscess, Dental infection, Odontogenic abscess, Parvimonas micra
Brain abscess is one of the most serious infections of the central nervous system. It consists of a focal purulent collection of the brain parenchyma.[
Pm, formerly known as Peptostreptococcus micros and Micromonas micros, is a Gram-positive anaerobic coccus that is normally found in the human flora of the oral cavity and gastrointestinal tract.[
A 62-year-old male presented to the hospital with a 1-week history of headache and an episode of transitory paresthesia in the left upper limb followed by a 2-min lapse in awareness and a claw-like left hand position highly suggestive of an atypical absence seizure. He had no history of fever, malignancy, diabetes mellitus, or corticosteroid use. Laboratory results revealed a normal white blood cell count and a moderately elevated C-reactive protein (63.6 mg/L–normal levels are below 10 mg/L–). The patient was alert and presented neither neurological deficits nor signs of meningeal irritation. An urgent brain computed tomography (CT) scan demonstrated an expansive process in the right parietal lobe [
Preoperative neuroradiological studies. (A) Computed tomography scan showing an isodense 3-cm-parietal mass with surrounding digitiform edema, (B) preoperative magnetic resonance imaging (MRI). (B1) T2-weighted MRI showing a hyperintense lesion with significant perilesional edema, (B2) diffusion-weighted imaging MRI showing a bright signal within the lesion (restriction of water diffusion), (B3) low apparent diffusion coefficient value within the lesion fluid. (B4) MR spectroscopy showing a high lipid level (lip) and decreased N-acetylaspartate, (B5) gadolinium- enhanced T1-weighted MRI showing a low-intensity lesion with rim enhancement which extended to the subarachnoid space (arrow).
On day 3, the patient underwent craniotomy with neurophysiological monitoring given the proximity of the lesion to the motor cortex. After opening the dura mater, a swollen brain was found [
Intraoperative photographs. (A) The patient was placed in the lateral position, (B) following dura opening, a swollen brain was found with a whitish subarachnoid area (arrow), (C) a catheter was inserted at the point where the abscess capsule was closest to the cortex. Brownish liquid pus was aspirated for mass decompression and later microbiological study. (D) Surgical view following removal of the whitish subarachnoid area and cavity washing.
The patient was also assessed by maxillofacial surgeons who detected severe periodontitis with infected mandibular cysts. This condition was considered the primary source of brain infection, and 1 week after craniotomy the patient underwent extraction of the lower teeth and curettage of mandibular cysts. Unfortunately, the material of the extracted teeth was not sent for microbiological studies. The patient was discharged in excellent conditions after 3 weeks of intravenous antibiotics, followed by 1 week of oral metronidazole and moxifloxacine. Oral antibiotics were maintained for 5 additional weeks. Follow-up MRIs demonstrated favorable progress without any radiological suspicion of recurrence [
The seriousness of brain abscesses requires prompt joint action by neurosurgeons and infectious-disease specialists. Merely focusing on the focal suppurative process of the brain parenchyma is not enough for a successful treatment. It is paramount to identify and eradicate the primary source of infection and the specific causative microorganism. In the case presented, Pm isolated in the brain abscess was assumed to have an oral origin based on the evident signs of dental infection. Abscess location in the parietal lobe supports that hematogenous dissemination is the major pathophysiological mechanism of brain abscess of odontogenic origin.[
After a thorough literature review, we found only ten previous cases of brain abscesses in which Pm, an organism typically found in the human oral flora, was isolated [
Optimal treatment of intracranial Pm infections remains uncertain.[
We report the successful diagnosis and treatment of a solitary brain abscess caused by Pm in a patient with severe periodontal infection. This case highlights the potential risk of untreated dental infections, which may lead to life- threating brain abscesses even in healthy patients. This report also supports that 16S rRNA analysis is a valuable technique to detect Pm in cases with culture-negative brain abscesses.
The authors certify that they have obtained all appropriate patient consent.
There are no conflicts of interest.
We are indebted to Crystal Smith and Liliya Gusakova, reference librarians of the National Library of Medicine, National Institutes of Health (Bethesda, MD, USA), and to Cristina Escudero and Ana Puerto, librarians of Puerta de Hierro University Hospital (Madrid, Spain) for their generous assistance during the process of retrieving some of the original articles used in this study. We are also grateful to George Hamilton for his critical review of the language and style of the manuscript.
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