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Sir,—We read with interest the article by Spyrou and colleagues1 in which Listeria monocytogenes was presented as an uncommon pathogen in infective endocarditis (58 cases in the literature). We have identified three further case reports2-4 and describe a patient with this condition who was recently under our care.
A 76 year old woman was admitted to our institution with a three month history of extreme lethargy, anorexia, and increasing dyspnoea. One month before admission she had been treated for a urinary tract infection and was noted to have a florid rash over both legs. A third mitral valve replacement, using a Hancock bioprosthesis, had been done 18 months before this admission. She lived in a rural community and routinely drank unpasteurised milk.
On examination she had two vasculitic lesions on the lower limbs. There were signs of mitral stenosis and tricuspid regurgitation. She did not have a fever and there were no other signs of endocarditis. Laboratory investigations revealed microscopic haematuria, polymorph leucocytosis, raised C reactive protein, low complement concentrations, and three positive blood cultures for L monocytogenes. Transoesophageal echocardiography showed a very thickened mitral prosthesis with severe mitral restenosis (0.7 cm2) and moderate tricuspid regurgitation. Vegetations were seen on the bioprosthesis.
The patient was treated with ampicillin and gentamicin. Her condition slowly deteriorated with progressive cardiac and renal failure and she died 21 days after admission. Postmortem examination revealed severe prosthetic mitral stenosis with nodular excrescences filling the valvar lumen. Histological examination showed these were composed of fibrin and colonies of Gram positive bacilli. A jet lesion was also noted in the left ventricle.
This case is interesting in that the source of infection was probably unpasteurised milk. Thus, it may be appropriate to advise patients with valvar prostheses to take the same dietary precautions currently given to pregnant women to avoid this infection.5
This letter was shown to the authors, who reply as follows:
We read with interest the report of a further case of listeria endocarditis by Johnston and Trouton. The consumption of unpasteurised milk and cheese made from unpasteurised milk has often been implicated in listeriosis. This has lead to the advice of dietary precautions for pregnant women. In view of the gravity of listeria endocarditis it is reasonable to consider giving the same recommendations to patients with damaged or prosthetic valves. However, the incidence is very low and therefore it is difficult to study the final common pathway in the pathogenesis of listeria monocytogenes endocarditis.
We assume that Johnston and Trouton’s patient lived for many years in a community where she would consume unpasteurised milk and, despite having a dysfunctional mitral valve that was replaced three times, she did not develop endocarditis until she was 76 years old. The difference for pregnant women is that they need to adhere to avoidance of unpasteurised products for only nine months, while patients with dysfunctional valves would be condemned to a lifetime of abstinence. We believe that patients should be advised that consuming unpasteurised milk may slightly increase the risk of developing listeria endocarditis.