Journal of Postgraduate Medicine
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Year : 2004  |  Volume : 50  |  Issue : 4  |  Page : 272-273  

Pneumocephalus associated with Bacteroides fragilis meningitis

Malvinder S Parmar 
 University of Ottawa, Timmins & District Hospital, Timmins, Ontario P4N 8R1, Canada

Correspondence Address:
Malvinder S Parmar
University of Ottawa, Timmins & District Hospital, Timmins, Ontario P4N 8R1


Gas within the intracranial cavity (pneumocephalus) commonly results from trauma or after surgery and rarely from infection by gas-forming organisms. The presence of pneumocephalus in the absence of injury or surgery should raise the suspicion of anaerobic infection of the central nervous system. I present a case of pneumocephalus associated with Bacteroides fragilis meningitis where the diagnosis was suspected after CT findings become available. Bacteroides fragilis meningitis is rare and often occurs in premature infants and neonates; only few cases are reported in adults. Pneumocephalus associated with Bacteroides fragilis meningitis is not described in the literature. This case also illustrates the absence of classic findings of meningeal irritation in the elderly. The literature is reviewed.

How to cite this article:
Parmar MS. Pneumocephalus associated with Bacteroides fragilis meningitis .J Postgrad Med 2004;50:272-273

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Parmar MS. Pneumocephalus associated with Bacteroides fragilis meningitis . J Postgrad Med [serial online] 2004 [cited 2021 Jan 18 ];50:272-273
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Gas within the intracranial cavity commonly results from trauma,[1] after surgery,[2] after lumbar drainage[3] or as a result of post-radiation necrosis[4] of skull appendages. Infection by gas-forming organisms[5] is an extremely rare cause of pneumocpehalus and often, is associated with Clostridium perfringens meningitis[5],[6] and rarely with mixed aerobic-anaerobic meningitis.[7] In adults Bacteroides fragilis meningitis is very rare and often has a predisposing factor[8] and pneumocephalus is not described in the literature with this organism. A case of pneumocephalus associated with Bacteroides fragilis meningitis is being reported.

 Case History

A 74-year-old woman with longstanding history of degenerative joint disease presented with worsening lower back pain of 2 weeks duration with fever and night sweats. She described pain across the lower back with radiation to posterior aspect of both thighs. She denied headache. There was no history of bladder or bowel incontinence. She denied leg weakness or paraesthesias. Her appetite was poor and she lost 15 pounds in the past 6 months. Her brother had tuberculosis 50 years ago. Her medications included aspirin, diclofenac and acetaminophen with codeine as needed. She had 45-pack years history of smoking. Physical examination revealed her to be in mild pain with temperature of 380Cand blood pressure of 160/80 mmHg. There was no lymphadenopathy. There was no neck stiffness and the Kernig sign was negative. The patient had pain with leg-raising in the lower back and thigh because of ongoing degenerative bone disease. Heart sounds were normal with 2/6 systolic murmur in the aortic area with transmission to the carotids. Lungs were clear. Abdominal examination was benign other than obese, soft abdomen. There was no renal angle fullness or tenderness. She was alert and oriented. Neurological examination was non-focal. The deep tendon reflexes were decreased but symmetrical. There was no focal tenderness of the spine. There was mild weakness of the lower extremities but symmetrical.

Laboratory data showed elevated white cell count of 21.5 (4.0-11.0 x109/L), elevated ESR of 115 (normal 0-20 mm/hr). Urinalysis was negative for blood and protein. Urine culture grew E. coli. Renal and hepatic profile was unremarkable save for slightly low serum albumin of 31 g/L (35-50 g/L). Chest X-ray was unremarkable. A CT scan of the lumbosacral spine showed severe facet hypertrophic osteoarthritis at L4-L5 and L5-S1 levels. There was no evidence of associated spinal stenosis. Extensive calcification was noted in the lower abdominal aorta and iliac arteries. Triple phase bone scan was unremarkable. Abdominal ultrasound showed benign cortical cyst in the left kidney and ectatic atherosclerotic aorta. Echocardiogram showed aortic sclerosis. There was no vegetation, specifically.

She was admitted to the hospital and treated with trimethoprim-sulphamethoxazole for urinary tract infection. She continued to have fever despite treatment of urinary tract infection. The possibilities of underlying vasculitis, neoplastic process and tuberculosis were entertained because of persistently elevated ESR and ongoing symptoms with fever and night sweats. This work-up remained negative. Work-up for collagen vascular disease was negative, including negative anti-nuclear antibody (ANA), normal complement levels (C3 and C4), and negative anti-neutrophilic cytoplasmic autoantibody (ANCA). Three sets of blood cultures remained negative. Repeat ESR was still elevated at 120. Six days later, she developed diffuse headache and became confused. A CT scan of the head showed multiple pockets of air in both cerebral hemispheres [Figure:1]. Possibility of bacterial meningitis with gas-forming organisms, although rare, was considered and a lumbar puncture was performed. Opening pressure was 10 cm and cloudy fluid was obtained that showed low CSF glucose of Bacteroides species - fragilis group, Beta-lactamase producing organism. Tubercular culture was negative. She was treated with intravenous cefoxitin and metronidazole but her condition continued to deteriorate and she died ten days later. The family did not permit an autopsy.


Many aerobes and anaerobes are known for their gas-producing property in tissues.[5] These include Escherichia coli, Klebsiella species, Peptostreptococcus species, Bacteroides and Fusobacterium species, Streptococcus pyogenes (rare), and mixed facultative and anaerobic species, as seen in perianal phlegmon.

Bacteroides are thin, pleomorphic, non-motile, non-sporulating, gram-negative bacilli. All are obligate anaerobes, but the dominant pathogen, B. fragilis, produces enzymes superoxide dismutase and catalase that makes it relatively aerotolerant and is able to survive in the presence of oxygen up to 8 hours. Bacteroides species are present as part of the normal human flora, principally in the oropharynx and colon. B. fragilis often causes intrabdominal abscesses, pelvic infections and peritonitis. It is the most common cause of anaerobic bacteremia,[9] a life-threatening process that occurs commonly in debilitated patients who have intra-abdominal or pelvic disease. Meningitis with Bacteroides fragilis is rare[8] and often occurs in premature infants and neonates. When it occurs in adults, there is often has an underlying cause[8] such as cholesteotoma, nasopharyngeal carcinoma, chronic otitis media, para nasal sinus infection, and the source of infection should be actively sought.

All strains of B. fragilis produce beta-lactamases and are resistant to penicillin, but extended spectrum penicillins in combination with -lactamase inhibitors (ampicillin-sulbactam, ticarcillin-clavulanate, and pipracillin-tazobactam) are active against most strains. Other beta-lactam antibiotics that are active against most isolates are cefoxitin, cefotetan, cefotaxime, imipenem, and meropenem. Metronidazole, clindamycin, trovafloxcin (now withdrawn from the market), and chloramphenicol all have excellent activity. Metronidazole is the drug of choice for CNS infections. As B. fragilis is often associated with polymicrobial infections, it is important to eradicate other aerobic and facultative organisms simultaneously.


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