First Report of Brain Abscess Caused by a Satelliting Phenotypic Variant of Helcococcus kunzii

Abstract

Helcococcus kunzii was isolated from a brain abscess in a diabetic patient with cholesteatoma and demonstrated satellitism around Staphylococcus aureus in culture. This is the first reported case of severe central nervous system infection due to H. kunzii and the first description of a satelliting phenotypic variant of this organism. CASE REPORTA n 83-year-old man was admitted with a worsening right earache and fever for 10 days. He had a background history of hypertension, diabetes mellitus, and prostate cancer and was on androgen blockade therapy. On admission, he had a temperature of 37.2°C and a fluctuating consciousness level. Otoscopic examination revealed an inflamed outer ear canal. Blood tests showed leukocytosis (13.93 ϫ 10 9 /liter) with neutrophilia (12.19 ϫ 10 9 / liter). Liver and renal function test results were unremarkable. Contrast-enhanced computed tomography scans of the head showed a right-sided cholesteatoma with abscess formation in the mastoid cavity. There was no definite evidence of intracranial extension. Excision of the cholesteatoma and mastoidectomy were performed. Histology showed the presence of keratinized squamous metaplasia consistent with the preoperative diagnosis of cholesteatoma. Cultures of pus swabs obtained from the mastoid abscess were negative for bacterial and fungal growth.In view of the severe clinical infection with systemic upset, the head and neck surgeons in charge started the patient on intravenous ceftriaxone at 2 g every 12 h and intravenous metronidazole at 500 mg every 8 h for broad-spectrum coverage of Gram-negative pathogens, methicillin-sensitive Staphylococcus aureus, and anaerobes. Antipseudomonal coverage was to be added if the patient's condition did not improve. After 2 weeks of intravenous antibiotics, he showed clinical improvement and was switched to oral amoxicillin-clavulanate at 1 g twice daily. However, he developed generalized tonic-clonic convulsions and a high fever 3 weeks after the operation. Reassessment by computed tomography scans of the brain with contrast enhancement showed a right temporal brain abscess (Fig. 1). The abscess was drained surgically. Intravenous ceftriaxone at 2 g every 12 h and intravenous metronidazole at 500 mg every 8 h were restarted. In addition, intravenous vancomycin at 500 mg every 12 h (dose adjusted for estimated creatinine clearance) was commenced in view of breakthrough abscess formation despite previous broad-spectrum beta-lactam antibiotic use. Empirical local amikacin instillation was used to irrigate the abscess cavity through the abscess drain as described in the literature (1, 2). The patient's neurological status improved with no further seizure episodes. In view of the clinical improvement and the results of in vitro antimicrobial susceptibility testing of the bacterial isolate obtained from the brain abscess drainage at the second operation, he was kept on a regimen of ceftriaxone, vancomycin, and metronidazole. Local amikacin instillation through the abscess drain was discontinued. Subsequent c...

Identification and Clinical Significance of Helcococcus kunzii in Human Samples

“…However, it has sometimes been isolated in pure cultures, underlining that H. kunzii is able to act as a sole pathogen (18-24). In our study, H. kunzii was detected as the unique pathogen in two cases of osteomyelitis, confirming its opportunistic role, as previously reported in different types of infections such as bacteremia, pleural empyema, implantable cardiac device infection, prosthetic joint infection, and brain abscess (18)(19)(20)(21)(22)(23)(24). As opposed to bloodstream infections reported in the literature, the unique blood isolate in our study was recovered from a polymicrobial specimen (with H. kunzii, S. aureus, Proteus sp.…”

“…MALDI-TOF mass spectrometry accurately identified all 40 isolates to the species level (score of Ͼ2.0), while both rrs and sodA sequencing also unambiguously provided species-level identification. Only two recent papers reported the use of MALDI-TOF mass spectrometry for H. kunzii identification (23,24), and we confirmed here using a large panel of strains that this new method is reliable for species-level identification of H. kunzii. This is the largest case series of infections caused by H. kunzii, which can now be easily identified with modern methods (particularly MALDI-TOF mass spectrometry).…”

“…This predominance of H. kunzii was also demonstrated in venous leg ulcers where it was the fourth most frequently seen bacterial species (22%) in patient wounds, after Staphylococcus aureus (64%), Corynebacterium striatum (61%), and Pseudomonas aeruginosa (33%) (27). As reported here, patients are usually older than 57 years of age (5,13,16,17,19,21,23,24). H. kunzii was mostly isolated with concomitant bacteria (95% of cases), particularly staphylococci, Enterobacteriaceae, and anaerobes, as previously described (5,13,(15)(16)(17).…”

“…Most isolates included in this study (31/39, 79%) were recovered from lower extremity wounds as reported in the literature (20/31, 65%) (13,14,16,23,24). Interestingly, a study on the incidence of skin colonization demonstrated that 10% (12/120) of the foot specimens collected from podiatry patients were positive for H. kunzii (including two-thirds of specimens from diabetic patients), whereas only one specimen (2%) from a healthy volunteer was positive (14).…”

“…It has also been found in cultures of skin/soft tissue abscesses (1,6,16,18,19). A few observations of invasive H. kunzii infections (bacteremia, pleural empyema, implantable cardiac device infection, prosthetic joint infection, and brain abscess) have also been reported (20)(21)(22)(23)(24). Of note, H. kunzii was isolated once from a sow with purulent urocystitis, suggesting its possible pathogenic role in pigs (25).…”