Abstract
A 56-year-old man on long-term hemodialysis presented with a three-month history of progressive swelling of the left retroauricular area (Fig. 1A) without headache or fever. On admission, he was alert, oriented, and afebrile. The findings of the neurologic and physical examinations were unremarkable. Brain computed tomography (CT) (Fig. 1B) and magnetic resonance imaging (Figs. 1C, 1D) demonstrated a heterogeneous vault lesion destroying the left temporal bone with extracranial and intracranial extension but without evidence of underlying mastoiditis. A granulomatous ring-enhanced lesion was seen in the adjacent temporal parenchyma with mild edema. On diffusion-weighted sequences, the content of the liquid lesions appeared hyperintense. Laboratory investigations revealed moderate anemia (hemoglobin 10 g/dL) and high C-reactive protein concentration (36 mg/L) without hyperleukocytosis. Human immunodeficiency virus serology was negative.
Photograph of patient showing swelling over left retroauricular region (
The patient underwent surgical evacuation of the scalp abscess, extradural empyema, and temporal abscess with debridement of the infected skull. Pus culture yielded pure growth of a gram-negative bacillus identified as Serratia liquefaciens by API 20E (BioMérieux, Marcy-l'Etoile, France). Isolates were resistant to amoxicillin, coamoxiclav, cefalothin, and colistin, and susceptible to ceftriaxon, cefotaxime, gentamicin, and ciprofloxacin. In addition, polymerase chain reaction (PCR) analysis for Mycobacterium tuberculosis complex was positive, but no focus of tuberculosis was identified. Histopathologic examination of the biopsy sample revealed infiltration of the marrow spaces by neutrophils and the presence of plasma cells with admixed fibrosis consistent with concurrent acute and chronic osteomyelitis.
The patient was treated for six weeks with intravenous ciprofloxacin and oral anti-tuberculous therapy consisting of isoniazid, rifampicin, and pyrazinamide for two months followed by 10 months with isoniazid and rifampicin. Eight weeks after the operation, surgical specimen cultures yielded Mycobacterium tuberculosis. The patient had a complete recovery, and the findings of neurologic examination were normal. No residual mass or pathological enhancement could be detected on follow-up CT scans. No other patient from the same dialysis center has presented a S. liquefaciens or M. tuberculosis infection.
Serratia liquefaciens, previously considered an environmental non-pathogenic organism, is a gram-negative bacillus classified as a member of the Enterobacteriaceae. In the last three decades, S. liquefaciens has become an emerging human pathogen and an important cause of nosocomial infections with a high mortality rate. Many outbreaks have been reported, especially in intensive care units, as a result of contaminated blood transfusions or cystometric transducers, and in hemodialysis centers [1–4]. However, S. liquefaciens has never been reported as a cause of skull osteitis or intracranial suppuration. On the other hand, calvarial tuberculosis is a rare entity, occurring in children and young individuals. It may present as a subgaleal swelling (Pott's puffy tumor) with a discharging sinus when the outer table is involved. Involvement of the inner table is associated with formation of underlying extradural granulation tissue (52%) and, more rarely, cerebral tuberculomas (5%) [5]. Tuberculous intraparenchymal brain abscesses are rare [6].
A concomitant pathogen with M. tuberculosis in the brain parenchyma is exceptional: To date, only three cases have been reported. Siddiqui et al. in 2001 described two cases of concomitant pyogenic and tuberculous brain abscess localizing in the parietal and occipital lobe, respectively. Both patients had Streptococcus and M. tuberculosis in the pus without other tuberculous foci [7]. Recently, Ramesh and Sundar reported a concomitant tuberculous and pyogenic cerebellar abscess secondary to Staphylococcus aureus in a 26-year old patient with pulmonary tuberculosis [8]. Cerebellar spread from the pulmonary tuberculosis was suspected.
Our patient's case is unique in that the cranial vault was infected with two pathogens, namely an atypical (generally non-pathogenic) bacterium and a mycobacterium. It is recommended that one consider the possibility of other microorganisms such as mycobacteria even when pyogenic microorganisms already have been isolated, especially in endemic areas where the incidence of tuberculosis is high. Early diagnosis with surgical drainage followed by selection of adequate antibacterial drugs play crucial roles in the prognosis of skull osteitis with intracranial suppuration. The classical picture of intracranial hypertension associated with high fever usually is incomplete, even absent, as in our patient [9]. Although the origin of infection was unclear in this patient on long-term hemodialysis, chronic kidney disease may have been the predisposing risk factor when associated with poor living conditions. In conclusion, S. liquefaciens may act as a co-pathogen in infections in immunocompromised individuals.
Footnotes
Author Disclosure Statement
There are no conflicts of interest. No funding was received for this work.