Unveiling Brevibacterium Species Isolated in the Cerebrospinal Fluid: A Report of a Rare Case

This case emphasizes the significance of recognizing and managing Brevibacterium species. Here, we present a unique case of Brevibacterium species isolated from the cerebrospinal fluid of a 60-year-old female with recently diagnosed human immunodeficiency virus (HIV) and small cell carcinoma of the lung. Management involved a two-week course of intravenous vancomycin. Brevibacterium species are infrequently encountered in clinical practice. Sharing this case report aims to enhance the limited understanding of Brevibacterium species infections and encourages discussion among healthcare professionals regarding its diagnosis and management.


Introduction
Brevibacterium species are gram-positive, non-spore-forming bacteria commonly found in soil, dairy products, and human skin flora.They are considered opportunistic pathogens, typically associated with bloodstream infections in immunocompromised individuals.The presence of Brevibacterium species in the cerebrospinal fluid (CSF) is exceedingly rare, with only a few reported cases in the literature [1].The most common isolated species is Brevibacterium casei [2].There are cases of osteomyelitis, endocarditis, brain abscess, and peritonitis [3][4][5][6].However, their involvement in CSF infections is extremely rare, and no specific guidelines exist for their management in such cases.Here, we present a case of Brevibacterium species in CSF, emphasizing the unique clinical features, etiology, diagnostic evaluation, and management strategies.

Case Presentation
A 60-year-old female with a past medical history of chronic obstructive pulmonary disease, hyperlipidemia, and current methamphetamine use presented to the emergency department with worsening shortness of breath, productive cough, and brown sputum.Physical examination revealed a restless, anxious-appearing female, alert and oriented ×4, faint wheezing in all lung fields, tachycardia with regular rhythm, a left eye droop, and no neurologic deficits.Imaging studies revealed right middle and lower lobe infiltrates with a small pleural effusion, as well as mediastinal and right hilar adenopathy as seen in Figure 1 and Figure 2. Further workup led to the diagnosis of human immunodeficiency virus (HIV) infection with a low CD4 count (as seen in Table 1) and reactive serologic tests for syphilis (as seen in Table 2).A lumbar puncture demonstrated a positive venereal disease research laboratory (VDRL) in the CSF (as seen in Table 3).The patient was initiated on intravenous penicillin G for neurosyphilis treatment.

Laboratory test Patient values Reference range
HIV-1 Qnt NAAT 419 copies/mL 30-10,000,000 copies/mL    Subsequently, a mediastinal lymph node biopsy revealed small cell carcinoma of the lung.In an unexpected finding, CSF cultures grew Brevibacterium species.Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry confirmed the identification.Because meningitis was not a recognized complication of Brevibacterium species infection, its isolation in combination with HIV infection and malignancy prompted management with 14 days of intravenous vancomycin 1 g twice daily.
For stage 4 small cell lung carcinoma, treatment was initiated utilizing cisplatin 50 mg daily for three days, etoposide 160 mg daily for three days, and dexamethasone 10 mg daily with chemotherapy.After her first cycle of chemotherapy, subsequent assessments included repeat CD4 measurements, revealing an absolute CD4 count of 675 and a CD4% of 35%.Importantly, the patient did not have acquired immunodeficiency syndrome (AIDS).

Discussion
The initial presence of a positive screening syphilis antibody test, along with an elevated reactive rapid plasma reagin (RPR) titer, prompted the decision to conduct a lumbar puncture to explore the possibility of neurosyphilis.The identification of Brevibacterium species in the CSF but not in the bloodstream prompted concerns regarding possible contamination.Nonetheless, repeated culturing of the same CSF sample and confirmation with MALDI-TOF mass spectrometry solidified the diagnosis.The patient's immunocompromised state, with concurrent HIV infection and small cell carcinoma of the lung, likely predisposed her to the isolation of Brevibacterium species in the CSF.
Given the lack of standardized treatment guidelines, management decisions were made based on available evidence and expert opinion [2].Vancomycin has been used in immunocompromised patients, particularly those with cancer and HIV, for Brevibacterium bacteremia [7].Therefore, the patient received a 14-day course of intravenous vancomycin 1 g twice daily [8].A follow-up lumbar puncture is scheduled in six months to determine the subsequent course of action in the management plan.
The presence of Brevibacterium species in the CSF of our patient represents a rare and unique case, given the scarcity of reported cases involving this pathogen in the central nervous system.The immunocompromised status resulting from HIV infection and stage 4 small cell carcinoma of the lung likely played a significant role in the dissemination of the pathogen to the CSF.Notably, the patient's absolute CD4 count exhibited improvement following the initial round of chemotherapy, even in the absence of antiretroviral therapy.

Conclusions
We present an intriguing and rare case of Brevibacterium species isolated from the CSF of a patient newly diagnosed with HIV and stage 4 small cell lung carcinoma.The patient's compromised immune system likely made her susceptible to this unusual infection.She was treated with a 14-day course of intravenous vancomycin at 1 g twice daily.A follow-up lumbar puncture will be performed in six months to determine the next step in management.This case report aims to enrich the existing knowledge about Brevibacterium species in the CSF and ignite meaningful discussions among healthcare professionals regarding its management.