| Abstract|| |
We report a case of intratumoral brain abscess due to Bacillus cereus in an adult male patient, which was managed successfully with excision of lesion and piperacillin-tazobactam for the duration of 5 weeks. To the best of our knowledge, this is a first case report of B. cereus infection leading to intratumoral brain abscess in a patient with a history of steroid administration by the intravenous route.
Keywords: Bacillus cereus, brain abscess, opportunistic infection
|How to cite this article:|
Saigal K, Gautam V, Singh G, Ray P. Bacillus cereus causing intratumoral brain abscess. Indian J Pathol Microbiol 2016;59:554-6
| Introduction|| |
Bacillus cereus is a motile, aerobic or facultative anaerobic, spore-forming, Gram-positive, or Gram-variable bacterium that is found in dust, air, and water. As a human pathogen, the organism is perhaps best known for its role as a mediator of self-limited foodborne illness. Among members of this genus, only B. anthracis is potentially more significant as a cause of human disease.  B. cereus can cause some opportunistic infections such as bacteremia, pneumonia, ophthalmitis, osteomyelitis, soft tissue infections, and meningitis in immunocompromised hosts. ,, Combination therapy with vancomycin or clindamycin and aminoglycoside has been recommended for systemic infections.  Meningoencephalitis with B. cereus has been reported in very low birth weight premature babies. , B. cereus brain abscess, however, is very rare and to date, only a few cases have been reported in individuals with high-risk factors. ,, We report the first case of intratumoral brain abscess by B. cereus, which most probably had a portal of entry from an intravenous catheter.
| Case Report|| |
A 51-year-old male, resident of Kullu, presented in the emergency services with an episode of severe headache followed by unconsciousness. Detailed history revealed patient was having a complaint of headache for the last more than 2 years, which was mild to moderate in intensity, diffuse in nature, with no associated aggravating or relieving factors. Recently his symptoms worsened and were accompanied with fever >39°C for >1 month, an episode of generalized seizures 10 days back followed by projectile vomiting which was non-bile stained. The patient had a history of forgetfulness for 7 days, irrelevant talk and difficulty in walking for the last 2 days, urinary incontinence, and altered behavior for 1-2 days. He was admitted in the local hospital for about 2 weeks where he was managed with intravenous steroids, but the condition of the patient worsened, and he was referred to the emergency department of our hospital. On examination, Glasgow Coma Scale score was E4V4M5, pulse rate - 100/min, blood pressure - 128/78 mmHg, fever 38.4°C, and all other systems were within normal limits. Laboratory investigations revealed, hemoglobin - 9.4 g/dl, total leukocyte count 9000/mm 3 (differential leukocytes count - N-61, L-33, M-4, E-2), and all electrolytes within normal limits. He was seronegative for hepatitis B surface antigen and nonreactive for HIV. Magnetic resonance imaging report revealed an irregular thick-walled peripheral enhancing space occupying lesion with perilesional edema in the right parieto-occipital region causing a mass effect with significant midline shift toward left suggesting an abscess/tumor. The right parietal craniotomy was performed with excision of lesion. Excised lesion was sent in formalin for histopathological examination (culture could not be performed) and about 10 ml pus was aspirated and sent to the microbiology laboratory for bacterial/fungal/tubercular culture and sensitivity. The excised tissue was labeled as a low-grade glioma (astrocytoma) on histopathological examination. No bacterial elements were found on histopathological examination of the tissue. Gram-staining of the pus sample revealed pus cells with Gram-positive bacilli [Figure 1]a and b. Organism grew well on 5% sheep blood agar aerobically, as well as anaerobically, producing beta hemolytic colonies. On spore staining using Schaeffer-Fulton method, ellipsoidal subterminal spores with no swollen sporangia were found. The organism was motile with typical stately motility. It was catalase positive, oxidase negative, produced acid from glucose with no gas, acid was also produced from maltose, salicin, trehalose, and glycogen but not from arabinose, glycerol, and mannitol. The organism was lipase, casein hydrolysis, and starch hydrolysis positive. It did not reduce nitrate and showed no growth at 50°C. Pus for fungal or tubercular culture was negative. Blood culture of the patient at the time of admission could not be performed as the patient was already on antibiotics when transferred to our hospital. The final diagnosis of intratumoral abscess caused by B. cereus was made. On antimicrobial susceptibility (CLSI M45), it was sensitive to gentamicin, ciprofloxacin, piperacillin-tazobactam, and meropenem; intermediate sensitive to chloramphenicol and resistant to amoxicillin and cefotaxime. Based on the antimicrobial susceptibility report, patient was started with piperacillin-tazobactam which was continued for 5 weeks and thereafter patient was discharged successfully.
|Figure 1: (a and b) Gram - stain of the pus aspirated from the brain abscess shows Gram - positive bacilli (arrows) along with polymorphonuclear cells|
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| Discussion|| |
B. cereus is a ubiquitous, Gram-positive organism that commonly induces food poisoning. B. cereus can readily contaminate the hospital environment, including the uniforms of health care workers, patients' dressings, or intravenous catheters.  Despite the widespread distribution of the Bacillus genus, they rarely cause systemic infections. Organism has been described as causing localized infections, specifically destructive eye infections that lead to orbital abscesses and endophthalmitis. , Little is known about the source of transmission of B. cereus infection in the central nervous system (CNS). Diligent analyses of possible risk factors must be considered while considering the CNS infection by B. cereus. Common risk factors include bowel perforation, ventriculoperitoneal shunting, intravenous or arterial catheterization, neonatal leukemia, mechanical ventilation, and bronchopulmonary dysplasia. , The role of B. cereus in nosocomial acquired bacteremia and wound infections in postsurgical patients has also been well defined, especially when intravascular devices such as catheters are inserted. The intravenous route for administration of steroids in a local hospital for about 2 weeks was the only possible risk factor which could be delineated in our case. In reviewing various reports of brain abscess due to B. cereus, it was observed that most infections occur in pediatric and immunosuppressed adult patients (generally due to leukemia and other malignancies) and are predominantly secondarily to B. cereus bacteremia or following induction chemotherapy [Table 1].
This is the first case from India reporting B. cereus causing brain abscess in an apparently immunocompetent individual. Previous cases reported by B. cereus are polymicrobial. Unlike the previous cases, the present case was a monomicrobial infection by B. cereus (pure growth of B. cereus on culture and on Gram-stain, there were pus cells and Gram-positive bacilli only). In the initial postoperative period (about 3 days) till the laboratory results were awaited, the patient was managed with fluids, mannitol, ceftriaxone, amikacin, and metronidazole. Still, the patient continued to have fever >39.5°C and developed left hemiparesis. Based on the antimicrobial sensitivity report, the patient was switched over to piperacillin-tazobactam and improved dramatically in next subsequent weeks. Most strains of B. cereus produce β-lactamase as a result of which they are generally resistant to penicillins and cephalosporins.  Our strain was sensitive to piperacillin-tazobactam in-vitro, as well as in-vivo, thus indicating that piperacillin-tazobactam can be used as empirical therapy in CNS infections due to B. cereus. To the best of our knowledge, this is the first case of intratumoral brain abscess by B. cereus which most probably had a portal of entry from an intravenous catheter.
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Department of Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None