Listeria monocytogenes Infection in a 69-year-old Diabetic

Listeria monocytogenes is a gram-positive, rod-shaped facultative anaerobe, often misidentified with Diphtheroids due to sharing similar characteristics. Due to its virulence factor listeriolysin O, it is capable of evading host immune systems and living in extreme environments. This organism often causes listeriosis in pregnant women, newborns, the elderly, or immunocompromised individuals. Therefore, it is crucial to include listeria infection in patients with positive diphtheroids in blood or CSF. We discuss a case of a 69- ear-old Hispanic woman with a history of type 2 diabetes mellitus, hypertension, seizure disorder, and obesity who presented with generalized body aches and fever. Initial blood culture showed diphtheroid on blood culture. In order to distinguish listeria from diphtheroids, longer blood culture inoculation is required. After 48 hours of inoculation, blood culture resulted in L. monocytogenes as the culprit of the patient’ symptoms, contributing to the complex nature of distinguishing between diphtheroid and listeriosis. Therapy was modified to ampicillin at this time. Following antibiotic treatment and negative blood culture, the patient fully recovered from the listeriosis without suspicion of having symptoms of endocarditis and meningitis.