Nocardiosis Cases and Risk Factors for Infection in a Tertiary Care Hospital

Introduction: Nocardiosis is an opportunistic infectious disease that involves the lungs, brain, eyes and skin and tends to occur in patients using immunosuppressive drugs (especially affecting cellular immunity) or chemotherapeutics, also in patients with diabetes mellitus, AIDS, lymphoreticular malignancies, solid cancers and architectural lung diseases such as bronchiectasis and cystic fibrosis. Here, it was aimed to present the clinical features and the risk factors of nocardiosis cases followed in a tertiary care hospital. Materials and Methods: All adult patients with a culture-proven Nocardia spp. infection at our hospital from 2013 to 2019 were analyzed in the study retrospectively. Strains were identified by conventional methods and in the case of availability, by 16SrRNA gen analysis or MADI-TOF; antimicrobil susceptibilities were defined by gradient method. Results: There were a total of 9 nocardiosis cases during the study period: 4 with disseminated (including pulmonary, brain, muscle, eye) nocardiosis, 4 with pulmonary nocardiosis and 1 case with skin nocardiosis. Corticosteroids, temozolomide, mycofenolate mofetil and cyclosoprin were used by patiensts as immunosupresive drugs in 6, 2 ,1 and 1 them, respectively. All of the patients were lymphopenic except one. Five strains identified at species level were N.cyriacigeorgica (2 strains), N.farcinicia, N.asteroides and N.abscessus, respectively. All of the 7 strains with available suceptibility test results were susceptible to co-trimoxazole. Conclusion: Nocardia spp. should always be taken into consideration in the case of pulmonary or central nervous system infections of patients with supressed cellular immunity or lymphopenia. In the case of newly defined CNS lesion in a patient with both malignancy and pulmonary nocardiosis, CNS nocardiosis should always be kept in mind in the differential diagnosis. Although chemotherapeutic agents have always been defined as risk factors for nocardiosis, temozolomide could be a stronger risk factor because of its ability to cause a deeper lymphopenia. If nocardiosis is always to be considered in the case of a compatible clinical situation in patients on temozolomide regime, the real incidence of nocardiosis and prophylactic strategies among those patients could be defined properly.