Case Presentation: A 62 year old man with a history of end stage liver disease secondary to Hepatitis C and alcohol, chronic obstructive pulmonary disease, and benign prostate hyperplasia presented to the hospital with a three day history of subjective fevers and chills, nausea and vomiting, anorexia, flank pain, and decreased urine output . Exam on admission was notable for tenderness to light palpation of the left lower and middle abdomen without guarding and left sided costovertebral tenderness. Laboratory studies were significant for leukocytosis of 16,000 cells/uL and a creatinine of 2.4mg/dL (150% above patient’s baseline). Abdominal CT scan showed a 5 mm left proximal ureteral calculus resulting in moderate left hydroureteronephrosis. The patient was taken to the operating room and a left ureteral stent was placed by Urology. The patient’s post-operative course was complicated by fever, hypoxemia, and hypotension requiring vasopressor support. Microbiology studies revealed four blood cultures taken on separate days with Coagulase-negative staphylococci and a urine culture with >100,000 Col/mL of Coagulase-negative staphylococci with susceptibilities identical to that of the blood culture isolates. The patient was started on broad spectrum antibiotics which were eventually narrowed once susceptibility testing returned. The patient responded to initial antibiotics and subsequent blood cultures were without growth.
Discussion: Coagulase-negative staphylococci (CoNS )are the most frequent bacteria isolated from blood cultures and are the most common cause of nosocomial bloodstream infections. CoNS are often overlooked as a cause of serious infection and are generally dismissed as a contaminant or an avirulent organism. In recent years however, CoNS has emerged as a clinically significant pathogen that can cause a variety of infections. Patients with indwelling catheters, or any other foreign bodies including prosthetic valves and pacemakers, and any immunocompromised patients are at especially high risk of infections by CoNS. The infections caused by CoNS vary depending on the species of CoNS implicated. Though less serious infections such as uncomplicated UTI, and skin and soft tissue infections have been reported, CoNS is emerging as an important cause of native valve endocarditis, with certain species causing severe disease reminiscent of those caused by Staphylococcus aureus. It is important to launch a thorough investigation to rule out other causes of the bacteremia as this will have implications on aggressiveness of infection as well as antibiotic choice and duration.
Conclusions: In hospitalized patients with blood cultures growing CoNS, it is important to consider the likelihood of true infection. Certain species of CoNS may cause more virulent infections than others, however many hospitals may not readily identify CoNS to the species level. Thus distinguishing contaminants from true pathogens continues to be a clinical dilemma. However, in patients with signs of clinical deterioration and persistently positive, adequately collected blood cultures growing CoNS; a high clinical suspicion for serious infections by these organisms must be considered. This is especially true in immunocompromised patients and those with indwelling devices.Because of the high prevalence of CoNS isolates in hospital blood cultures, it is important that hospitalists are aware of this bacteria’s ability to cause severe disease.