A Pediatric Case of Cardiobacterium Hominis Endocarditis
A 12 year old boy, who was status post repair (shortly after birth) of Tetralogy of Fallot with pulmonary atresia and subsequent replacements of right ventricle to pulmonary artery conduit 4 years prior to current evaluation, was seen in an outside Pediatric cardiology clinic for his annual follow-up appointment. The appointment had been scheduled one month earlier on the patient’s request, due to the onset of generalized fatigue and decreased endurance of 2-3 weeks duration. The patient denied symptoms of fever, chest pain, dizziness or syncope.\nThe patient had a history of poor dentition, poorly controlled asthma, sleep apnea, and allergic symptoms, which led to an adenoidectomy two years prior to current presentation. The most recent right ventricle to pulmonary artery conduit replacement occurred 4 years prior to presentation which was complicated by Staphylococcus aureus mediastinitis. In clinic, by report, the physical examination revealed a well looking boy with thin habitus, in no acute distress with a heart rate of 102 beats/min, respiratory rate of 16 breaths/min and a blood pressure of 94/70 mmHg. Respiratory examination was significant for mild end expiratory wheezes. Cardiovascular examination demonstrated a regular rate and rhythm with a normal S1 and split fixed S2. A 3/6 graded harsh, early peaking, mid pitch systolic ejection murmur and a soft 2/4 graded diastolic murmur were heard best at the left sternal border. Of note, there were no peripheral stigmata of endocarditis (splinter haemorrhages, Osler nodes or Janeway lesions) and the remainder of the physical examination was unremarkable. A routine echocardiogram showed a bright and thickened conduit valve with a suggestion of mass attached to the leaflet. This was not present on the previous echocardiogram (approximately 2 years prior).\nBlood work at the clinic appointment was significant for a mildly elevated ESR of 25 mm/hour, CRP of 11.5 mg/L and a WBC of 5.92 cell/cm3 with 16% of monocytes. Repeat blood work 2 days later showed slight improved CRP of 7.6 mg/L, unchanged ESR and CBC, normal electrolytes, LFT, CXR, and sinus films. A throat culture was positive for Streptococcus and ASO titre was elevated. The patient was started on amoxicillin for Streptococcal pharyngitis. At this time, the patient spiked a fever of 38.3°C. The blood cultures taken both at presentation and two days later became positive for a slow growing gram negative rod.\nBased on the positive blood cultures and the findings on the ECHO, the patient was referred for admission at University of Michigan C.S. Mott Children’s Hospital with the diagnosis of subacute bacterial endocarditis four days after the initial clinic visit. Upon admission the patient was continued on amoxicillin for the Streptococcal pharyngitis and empirical treatment for bacterial endocarditis with intravenous (i.v.) vancomycin and i.v. piperacillin/tazobactam was initiated. Infectious Diseases was consulted three days after admission and the antibiotics were narrowed to i.v. ceftriaxone 1700 mg q 12 hours since blood cultures had become negative after the first few doses of amoxicillin. At this time, oropharyngeal flora was suspected and organisms such as Kingella and Haemophilus species are not particularly virulent and are susceptible to ceftriaxone.\nAerobic and anaerobic blood cultures obtained on admission and on the subsequent day remained negative. A trans-thoracic echocardiogram on the second day after admission demonstrated evidence of a new oscillating mass on a pulmonary valve leaflet concerning for a possible vegetation. The local laboratory was initially unable to identify the gram negative rod isolated from their clinic and the organism was sent to the University of Michigan microbiology laboratory where it was identified as Cardiobacterium hominis (C. hominis) that was susceptible to amoxicillin/clavulanate, meropenem, ceftriaxone and levofloxacin and resistant to ampicillin. The combined susceptibilities from the two laboratories are shown in .\nThroughout the duration of admission, the patient remained afebrile and well-appearing and was discharged home on the fifth hospital day in stable condition on i.v. ceftriaxone therapy through a right upper extremity peripherally inserted central catheter line to complete a 6 week course of antibiotics. Two weeks into the course of treatment, the patient developed an intense pruritic rash near his peripherally inserted central catheter (PICC) site and along the PICC line track concerning for allergy. Ceftriaxone was discontinued and ampicillin/sulbactam was started. However, the patient developed another lacy rash and ampicillin/sulbactam was then switched to levofloxacin 10 mg/kg/day orally for the remaining two weeks of antibiotic therapy.