Bacillus Cereus Prosthetic ValveEndocarditisEvaristo Castedo, MD, Almudena Castro, MD, PalomaMartin, MD, Jorge Roda, MD, and Carlos G. Montero,MD

Departments of Cardiothoracic Surgery, Cardiology, andMicrobiology, Hospital Puerta de Hierro, UniversidadAutonoma de Madrid, Madrid, Spain

Bacillus cereus is a ubiquitous organism that often con-taminates microbiological cultures but rarely causes se-rious infections. Reports of B cereus endocarditis areinfrequent. Infection in patients with valvular heartdisease is associated with significant mortality and mor-bidity. We describe a case of B cereus endocarditisinvolving a mechanical mitral prosthesis that resolvedafter replacement of the prosthetic valve. We also reviewthe previous cases reported in the literature.

(Ann Thorac Surg 1999;68:2351–2)© 1999 by The Society of Thoracic Surgeons

Bacillus cereus endocarditis is a rare entity that isusually associated with intravenous drug adminis-

tration, and underlying valvular disease. When the infec-tion involves a prosthetic valve it is usually a verydestructive process with a malignant clinical course. Wepresent a case of B cereus prosthetic valve endocarditis ina patient who underwent replacement of the mitralprosthetic valve.

A 45-year-old Caucasian female was admitted to ourhospital with fever, chills, and weakness of 3 days’duration. She had undergone a Hall–Kaster mitral valvereplacement 17 years earlier for rheumatic heart disease.Two months before admission, she experienced abdom-inal pain, and a colonoscopic study was ordered. She wasadmitted to our center 48 hours prior to the procedure inorder to have the warfarin that she was taking due to themechanical prosthesis, substituted by IV heparin. Noprophylactic antibiotics were given. Twelve hours beforecolonoscopy, she experienced fever of 38.5°C and chills.The venipuncture site for heparin was swollen and ten-der. The endoscopic study showed no pathological find-ings. She was treated with amoxicillin-clavulanic acid for7 days and discharged.

On admission, no symptomatology of respiratory orurinary tract infection was recorded. She denied iv druguse. On physical examination, her temperature was 38°C,

pulse 100 beats/min, and blood pressure 120/80 mm Hg.Skin, lung, abdominal, and neurological examinationrevealed no abnormalities. She had normal regular pros-thetic valve sounds and a grade 2/6 systolic ejectionmurmur at the apex radiating to the axilla. Abnormallaboratory findings included a white blood cell count of20,000/mm3 with 61% segmented polymorphonuclearwhite cells. The chest x-ray film showed moderate car-diomegaly, and the electrocardiogram, atrial fibrillation.A transesophageal echocardiogram revealed a highlymobile echo mass attached to the anulus of the mitralprosthetic valve and a mild to moderate mitral regurgi-tation. Administration of a combination of vancomycin,gentamicin, and rifampin was started after blood cultureswere drawn. Three sets of blood cultures yielded Bacillusspecies that were sensitive to vancomycin, gentamicin,rifampin, and amoxicillin. Neither increased white blood

Accepted for publication May 17, 1999.

Address reprint requests to Dr Castedo, Department of CardiothoracicSurgery, Hospital Puerta de Hierro, C/San Martın de Porres, 4, E-28035Madrid, Spain; e-mail: soniaf@ti:telefonica.es.

Fig 1. Preoperative transesophageal echocardiographic image of theheart, showing two mobile vegetations on the mitral prosthetic valve(arrows). (LA 5 left atrium; LV 5 left ventricle.)

Fig 2. Scanning electron microscopic view of the Bacillus cereusisolated from the prosthetic vegetation. Rod-shaped cell with a cen-tral and ellipsoidal endospore; bacillary body width more than1 mm; peritrichous flagella (arrow). (E 5 endospore.)

2351Ann Thorac Surg CASE REPORT CASTEDO ET AL1999;68:2351–2 BACILLUS CEREUS ENDOCARDITIS

© 1999 by The Society of Thoracic Surgeons 0003-4975/99/$20.00Published by Elsevier Science Inc PII S0003-4975(99)01163-7

cell count nor fever disappeared despite antibiotic ther-apy, and on day 6 after admission, the patient suffered atransient episode of dysarthria and headache. Cranialcomputed tomographic (CT) scan revealed two recentinfarcts in the right hemisphere. A new transesophagealechocardiogram showed two mobile vegetations on theanterior anulus of the mitral prosthetic valve (Fig 1).

Because of persistence of fever despite adequate anti-biotic therapy and the evidence of central embolic events,as documented on a CT scan, the patient underwentreplacement of the mitral prosthetic valve. Two vegeta-tions were found on the anterior anulus of the mitralvalve. The mitral prosthesis was replaced with a St. JudeMedical prosthesis (27 mm in diameter; St. Jude Medical,Inc, St. Paul, MN). Cultures of the vegetations on thesewing ring of the explanted prosthesis yielded Bacilluscereus (Fig 2). The patient has remained well for 6 monthssince a 6-week course of antibiotics was completed.

Comment

Bacillus species are ubiquitous, aerobic, spore-formingrods that can stain as gram-positive or gram-variable andare common contaminants of blood cultures.

B cereus was considered to be just a contaminant untilFarrar, in 1963, identified it as a pathogen [1]. Clinicalinfection with B cereus can be categorized broadly asgastrointestinal (food-poisoning-related) or non-gastrointestinal disease, and the latter can be separatedinto infections that are either local (postsurgical or trau-matic wound, burn, ocular) or systemic (bacteremia-septicemia, meningitis, respiratory, endocarditis).

B cereus bacteremia is a frequent event. In the majorityof cases, it is transient and not clinically significant. Mostcases of significant clinical illness are related to iv drugabuse, presence of foreign bodies (iv catheters, mechan-ical prostheses) and immunocompromised hosts.

Bacteremia may be complicated by endocarditis; infact, B cereus is a small but significant cause of endocar-ditis, particularly when associated with intravenous drugadministration or an underlying valvular disease. Theportal of entry in a drug addict is usually either the drug

or the injection equipment but, in our case, it is verylikely to be related to the venipuncture site because therewere signs of thrombophlebitis at that level, fever beganbefore the colonoscopy was performed, and no case of Bcereus endocarditis after invasive gastrointestinal diag-nostic tests has, to our knowledge, been reported [2].However, given that the patient’s first symptom wasabdominal pain, the possibility that the patient firstpresented with B cereus enteritis and seeded the valveduring colonoscopy cannot be ruled out.

B cereus endocarditis affecting iv drug users respondsextraordinarily well to antibiotic therapy, but when itinvolves a prosthetic valve, it is associated with signifi-cant mortality and morbidity. Data for 3 cases of pros-thetic valve endocarditis due to B cereus reported in theEnglish literature are summarized in Table 1 [3–5]. Thefirst patient had a mechanical mitral prosthetic valve anddied after being treated with antibiotics alone. The other2 patients, with aortic prostheses, recovered after re-placement of their infected prosthetic valves. We de-scribe the fourth reported case, to our knowledge, of Bcereus prosthetic valve infection and one in which thepatient survived a mitral prosthetic valve endocarditis. Itis also the only case of those documented, thus far, inwhich B cereus was isolated from the excised valve tissue.

We would suggest consideration of prompt valve re-replacement in order to reduce the high mortality andmorbidity (recurrent thromboembolic events, prosthesisdysfunction) associated with prosthetic valve endocardi-tis caused by B cereus.

References

1. Farrar WE. Serious infections due to “non-pathogenic” or-ganisms of the genus Bacillus. Am J Med 1963;34:134–41.

2. Drobniewski FA. Bacillus cereus and related species. ClinMicrobiol Rev 1993;6:324–38.

3. Block CS, Levy ML, Fritz VU. Bacillus cereus endocarditis—acase report. S Afr Med J 1978;53:556–7.

4. Oster HA, Kong TQ. Bacillus cereus endocarditis involving aprosthetic valve. South Med J 1982;75:508–9.

5. Steen MK, Bruno-Murtha LA, Chaux G, Lazar H, Bernard S,Sulis C. Bacillus cereus endocarditis: report of a case andreview. Clin Infect Dis 1992;14:945–6.

Table 1. Characteristics of the Previous and Present Cases of Bacillus cereus PVE

Case ReferenceType of

PVEType of Preexisting

Prosthetic Valve

Cultures ofExcised Valvular

Tissue Complications Treatment Outcome

1 [3] Early Bjork–Shiley (M) Negative Renal, splenic, andcerebral infarcts

TM, CHL Died

2 [4] Late Carpentier–Edwards (A) Negative Paravalvular leak GM, CM,surgery

Recovered

3 [5] Late Bjork–Shiley (A) Negative Renal and splenicinfarcts

VM, surgery Recovered

4 Presentcase

Late Hall–Kaster (M) Positive Cerebral infarcts VM, GM, RM,surgery

Recovered

A 5 aortic; CHL 5 chloramphenicol; CM 5 clindamycin; early 5 within 60 days postoperatively; GM 5 gentamicin; late 5 later than60 days postoperatively; M 5 mitral; PVE 5 prosthetic valve endocarditis; RM 5 rifampin; TM 5 tobramycin; VM 5 vancomycin.

2352 CASE REPORT CASTEDO ET AL Ann Thorac SurgBACILLUS CEREUS ENDOCARDITIS 1999;68:2351–2