Bacillus cereus Bacteriemia/Endocarditis: Which should be the best targeted therapy?

We present the case of a patient with significant Bacillus cereus bloodstream infection. We are having some debate about the ideal targeted antibiotic therapy. Comments will be appreciated.

A continuación os presentamos un caso clínico activo, que nos está planteando dudas sobre el manejo antibiótico…todos los comentarios son bienvenidos…Un saludo

A 62 year-old man with significant past medical history for gout was admitted to our hospital 2 weeks ago because of acute pulmonary edema. On TTE he was found to have severe doble aortic damage. 48h after admission he spikes a fever of 38.5 and blood cultures were drawn (negative). 48 hours later he spikes again and new blood cultures are obtained, which grew Bacillus cereus (3/3). Concomitantly with these blood cultures he was found to have a peripheral vein phlebitis which was removed and vancomycin was started. 48 hours after starting vancomycin, he had a new fever and a new set of blood cultures was obtained (Bacillus cereus 1/3). Awaiting the susceptibility reports imipenem was added. Micro lab reports the following susceptibility data: Pen R (>8); Cefotaxime R (>16); Meropenem S (0.12); Vanc S (<1); Dapto S (4); gentamicin S(<4); clindamycin S(2)

Patient is awiting for TEE, but even if negative we consider this as a high risk bacteremia given his valve status. We have not found much information about how to treat a high risk Bacillus cereus bacteremia/endocarditis. The case has been discussed in our ID/Micro conference with a broad discrepancies: some argue in favor of combining vancomycin and gentamicin, some in favor of vancomycin in monotherapy and others in favor of including a b-lactam (carbapenem) +/- vancomycin.  We would appreciate your input. 

Patient has had no significant contact with Healthcare System in the previous months, nor has had recent dentalwork. No IVDU. Concomitantly he has been found to have microcitic anemia and has lost 10 pounds weight in the previous 6 months. This is going to be worked-up.

Thank you very much.

Best regards

José R. Pano-Pardo

Hospital Universitario La Paz-IDIPAZ

Madrid, Spain

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  1. Bacillus cereus is an ubiquitous sporulated grampositive bacilli which frequently represents contamination of clinical samples.

    In a review of positive blood cultures for Bacillus spp. in a North Carolina hospital in the 1980s, only 5 of 78 isolates were thought to represent true infection1. The most common feature in true Bacillus spp. bacteremia is the presence of an intravascular catheter, particularly a surgically implanted catheter2. Bacillus species are rarely the cause of native valve endocarditis and, when this occurs, it is almost always in injection drug users.

    In this case the presence of multiple positive cultures occurring in a high risk patient makes the isolation of Bacillus cereus meaningful. Although in vitro, most Bacillus spp. isolates are susceptible to vancomycin, clindamycin, fluoroquinolones, aminoglycosides, carbapenems and, variably, penicillins and cephalosporins, clinical data supporting the superiority of any of these antimicrobial drugs are scarce.

    In this setting we believe that a b-lactam (imipenem) could be more efficacious than vancomycin. In the absence of endocarditis we plan to continue therapy with imipenem monotherapy. if endocarditis was found to be present in surgical specimens we would favor to combine imipenem with vancomycin instead of an aminoglycoside based combination, given that the renal function has already deteriorated.


    Mandell: Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 7th ed

    1. Weber DJ, Saviteer SM, Rutala WA, et al: Clinical significance of Bacillus species isolated from blood cultures. South Med J 1989; 82:705-709.

    2. Blue SR, Singh VR, Saubolle MA: Bacillus licheniformis bacteremia: Five cases associated with indwelling central venous catheters. Clin Infect Dis 1995; 20:629-633.

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