Staphylococcus lugdunensis Bacteremia in Adults in a Large Community Teaching Hospital. Report of 29 Episodes and Review of its Epidemiology, Microbiology, Clinical Manifestations, and Treatment

Background: Staphylococcus lugdunensis is an emerging pathogen and an unusually virulent coagulates-Negative Staphylococcus (CNS) native to the human skin flora. If isolated from blood culture specimens, this CNS may be deemed a "contaminant" and a precious therapeutic window could be lost in patients with invasive S. lugdunensis disease/bacteremia. As microbiology laboratories have begun to differentiate this CNS from other Coagulase-Negative Staphylococci, the importance of S. lugdunensis in human disease has become more apparent. Methods: We reviewed the medical records of all adult (≥ 16 years of age) patients with Staphylococcus lugdunensis bacteremia at our institution during the period from January 1, 2006 to April 30, 2012 and report the incidence, epidemiology, microbiology, antimicrobial sensitivities, source of infection, comorbid conditions, and the results of treatment for these patients. Results: There were 29 episodes of Staphylococcus lugdunensis bacteremia in the 76-month study period for a mean incidence of 4.6 episodes/year. There were 19 episodes in women (65.5%) and 10 episodes in men (34.5%). The patients' ages ranged from 20 to 92 years with a mean of 57.1 years. The most common identifiable sources of bacteremia were vascular catheter infection in 10 of 29 patients (34.5%), skin and soft tissue infection in 6 patients (20.7%), infective endocarditis in 5 patients (17.2%). Endocarditis was seen in five patients (1 aortic valve, 2 mitral valve, 2 tricuspid valve). 7 patients (24.1%) had primary bacteremia (no source identified). The most common presenting manifestations were fever and chills in 12 patients (41.4%), decreased level of consciousness in 7 patients (24.1%), and increasing shortness of breath/dyspnea on exertion in 7 patients (24.1%). The average Charlson comorbidity index was 2.07 and the average age- adjusted Charlson comorbidity index was 3.52. The most common comorbidities were diabetes mellitus (9 patients=31.0%), hypertension (6 patients=20.7%), chronic obstructive lung disease (5 patients=17.2%), and solid tumor malignancy (5 patients=17.2%). Although Staphylococcus lugdunensis is often a relatively anti microbially sensitive Coagulase-Negative Staphylococcus, 53% of our strains were resistant to penicillin G, 36% resistant to methicillin/oxacillin, 37% resistant to trimethoprim-sulfamethoxazole, and 36% resistant to clindamycin. All strains were sensitive to vancomycin. All patients received initial appropriate antimicrobial therapy. Two of our 29 patients died resulting in a 6.9% mortality rate. Conclusion: Staphylococcus lugdunensis bacteremia is an emerging infectious disease that was common in our hospital during the years of our study. It causes severe and potentially fatal disease. Vascular catheter infections are the most common source of S. lugdunensis bacteremia and treatment should include vascular device removal and appropriate antimicrobial therapy. In septic patients with positive blood cultures for CNS, the isolated CNS should be identified to species level to appropriately identify infection due to S. lugdunensis. S. lugdunensis should be recognized as an aggressive emerging cause of bacteremia and sepsis syndrome in a general adult hospital population.