Caring for a patient with Listeria endocarditis: use of antibiotic desensitization.

Occurrence of Listeria endocarditis is rare, and the mortality rate is high, 100% in untreated cases. The use of antibiotics, specifically ampicillin, is considered a first-line treatment. Coadministration of ampicillin and gentamicin provides a synergistic effect in killing the bacteria. Antibiotics are among the most common causes of hypersensitivity reactions. Of all antibiotics, penicillin is the one that most often causes a reaction. Skin testing adds time until treatment, and all patients with sensitivity to penicillin may not be detected. In the case presented, the patient had antibiotic desensitization with ampicillin. He did not have any allergic reactions to the drug. However, his history of allergy to penicillin was uncertain, so perhaps he did not have a true, serious penicillin allergy. Also, most likely he was anergic and could not mount an immune response to ampicillin, even if truly allergic. Therefore, his response may not be a typical response to antibiotic desensitization. Understanding possible hypersensitivity reactions can help guide the medical and nursing management of patients having antibiotic desensitization.