Case Presentation:

An 18 year old male with a history of Trisomy 21 and Tetralogy of Fallot status post repair in infancy and subsequent bioprosthetic pulmonary valve replacement presented with a 10 day history of intermittent subjective fevers, diaphoresis, headaches, and left jaw pain.  Patient had undergone a routine dental exam two weeks prior for his left sided jaw pain, thought to be secondary to bruxism.   He initially presented to an Emergency Department where lab work was remarkable only for mild thrombocytopenia and mild hyponatremia.  At that time, CT head was normal and a Chest X-ray was positive only for mild cardiomegaly.  Patient was well appearing on exam and was discharged home.  Two days later both sets of blood cultures obtained in the ED grew gram positive rods and the patient was admitted for further management of bacteremia.  Repeat blood also grew gram positive rods, eventually identified as Lactobacillus rhamnosus.  Patient was initially treated with vancomycin, but after Lactobacillus was identified, he was switched to penicillin and gentamycin. Transthoracic echocardiogram revealed worsening pulmonary valve stenosis and insufficiency and Transesophageal echocardiogram revealed a possible perivalvar anterior abscess.  PET CT confirmed abscess and patient underwent pulmonary valve replacement after demonstrating that blood cultures had cleared.  Patient was discharged to complete a 6 week course of penicillin G. 

Discussion:

Clinically significant gram positive rod (GPR) bacteremia and endocarditis is rare.  More often, GPRs are thought to be contaminants when found in blood cultures. The likelihood of GPRs in blood cultures to be clinically significant increases if the organism grows in multiple blood cultures obtained from separate venipuncture sites. Certain underlying risk factors are also associated with increased likelihood of clinical significance such as prosthetic heart valve, intravascular devices, central lines, or history of IV drug use.  The range of organisms causing pathogenic GPR bacteremia is broad and includes listeria (neonatal, immunocompromised, and elderly patients with meningitis), bacillus species (B. cereus in line infections or IV drug use), lactobacillus (recent dental procedures), corneybacterium, arcanobacterium (recent dental procedure), erysipelothrix (contaminated diary products), and gardenella.  B. cereus, corneybacterium, arcanobacterium, and lactobacillus have all been described in endocarditis.  Choosing empiric coverage for GPRs can be challenging as some GPRs such as lactobacillus are intrinsically resistant to vancomycin while B. cereus is often resistant to ampicillin but sensitive to vancomycin.  Careful history taking is imperative when GPRs have been identified in blood cultures to identify risk factors that increase the possibility that the GPRs are clinically significant as well as aide in choosing appropriate empiric antibiotic coverage.

Conclusions:

While more unusual then other causes of bacteremia, the hospitalist should be aware of risk factors that increase the likelihood of clinically significant GPRs in blood cultures.  Empiric therapy, if appropriate, should be guided by a careful history identifying potential risk factors for particular bugs and narrowed based on culture results.  For ill patients, double coverage with both vancomycin and penicillin might be warranted while awaiting species identification.