A 21-year-old Caucasian female with known congenital heart disease presented with a five-day history of fever, lethargy and a swollen, painful left calf. Her past medical history included previous surgical repair for pulmonary atresia, quadricuspid aortic valve and a ventricular septal defect (VSD) as a child for which she took life-long warfarin anticoagulation therapy. She had also suffered recurrent miscarriages.
On examination she was febrile at 38.5°C, but hemodynamically stable. Significant positive findings were a swollen, tender left lower limb and an ejection flow murmur across the prosthetic aortic valve and pulmonary regurgitation through the pulmonary conduit, consistent with her heart condition. The remainder of the clinical examination was unremarkable.
Laboratory results showed: hemoglobin 9.3 g/dl; mean cell volume 0.32 fl; white cell count 8.6 × 109/liter; neutrophil count 6.7 × 109/liter; platelet count 268 × 109/liter; C-reactive protein 35 mg/liter; INR 3.0. Her renal and liver function tests were normal. The admission chest radiograph was unremarkable. Ultrasound of her calf showed a hematoma, which was aspirated percutaneously under ultrasound guidance, the subsequent culture being negative.
However, due to ongoing fevers the patient underwent a transthoracic echocardiogram (the patient was initially unable to tolerate the transesophageal approach) that raised the possibility of vegetations on the mitral valve and VSD patch. The patient then suffered a grand mal seizure requiring intubation and admission to the Intensive Care Unit. On examination a fixed and dilated right pupil was noted. Computerized tomography of the head showed a large right frontal parenchymal hematoma with several smaller frontal abscesses associated with mass effect and midline shift to the left (Figure 1a).
Neurosurgical review led to an emergency right frontal craniotomy with evacuation of the hematoma (Figure 1b), which was negative on microbiological culture. She was commenced on empirical intravenous ceftriaxone (2 g every 12 h), vancomycin (1 g every 12 h) and metronidazole (500 mg every 8 h) on advice from the Microbiology Department. Her post-operative progress was complicated by the need for further neurosurgery due to persistently raised intracranial pressure, resulting in a craniostomy.
Subsequently, 15 days into her admission one out of a total of 12 sets of blood culture specimens became positive after 22 hours of incubation on the BACTEC 9240 system (Becton Dickinson Microbiology Systems Ltd, USA). Pleomorphic gram-positive bacilli were seen in the blood gram film. The blood was inoculated onto several agar plates including: 5% horse blood agar (HBA; CM0271, Oxoid, UK); fastidious anaerobic agar (FAA; Oxoid, UK); Columbia blood agar with neomycin (FNEO; Oxoid, UK) aerobically and anaerobically for 2 and 5 days respectively. After 48 hours at 37°C both aerobic and anaerobic cultures yielded small translucent, non-pigmented colonies, surrounded by a small zone of beta-hemolysis on horse blood agar. The organism was noted to be catalase-negative and was identified as A. haemolyticum (99.9% probability) by biochemical testing with the API CORYNE identification strips (BioMérieux, France). This was later confirmed by the Health Protection Agency in London, United Kingdom, using 16S rRNA gene sequencing.
Antibiotic susceptibility testing by disk diffusion assay demonstrated that the organism was susceptible to penicillin, ceftriaxone, ciprofloxacin, gentamicin, rifampicin, and vancomycin. The minimal inhibitory concentration (MIC) of penicillin was 0.023 mg/L to the isolate (penicillin control MIC was 1.5 mg/L). There have been several reports of A. haemolyticum infective endocarditis in which there have been treatment failures with penicillin [5–7]. In view of this and the fact the patient was clinically improving, Microbiology advised continuing ceftriaxone with the addition of gentamicin (80 mg every 12 hours) to the treatment regime. Vancomycin and metronidazole were stopped at this point, having now received two weeks therapy of these. A course of 42 days of antibiotics was given in total, with all repeat blood cultures being negative.
On completion of the antibiotic course, the patient had some mild residual weakness and resting tremor of her right lower limb. Repeat transthoracic and transesophageal echocardiograms showed no evidence of endocarditic phenomena. At six months follow-up the patient reported no new symptoms and there was no clinical evidence of relapse of infective endocarditis. Subsequently the patient underwent a successful insertion of intracranial titanium plates and titanium cranioplasty nine months later.