Candidemia
Keith W. Hamilton
Ebbing Lautenbach
INTRODUCTION
The incidence of invasive fungal infections has increased as an unintended consequence of increased use of immunosuppression to treat certain medical conditions and the improved ability of medical technology to treat critically ill patients.
Candida species are the most common cause of health care-acquired invasive fungal infections and represent 5% to 10% of all central line-associated bloodstream infections (CLABSIs).
A blood culture positive for yeast should never be considered a contaminant and should be treated promptly with appropriate empiric antifungal therapy.
Delayed treatment has been associated with increased morbidity and mortality.
Possible sources of candidemia and presence of complications and focal organ involvement should also be investigated as these factors will impact the type and duration of therapy.
In critically ill patients, the most common sources of infection are indwelling catheters and gastrointestinal pathology.
Risk factors associated with candidemia include (i) presence of a central venous catheter, (ii) total parenteral nutrition, (iii) recent gastrointestinal surgery or perforation, (iv) receipt of broad-spectrum antibiotics, (v) acute renal failure, (vi) receipt of hemodialysis, (vii) mechanical ventilation, (viii) ICU admission, (ix) older age, (x) number of red blood cell transfusions, (xi) immunosuppression (including neutropenia), (xii) known fungal colonization, and (xiii) increased severity of illness.
Despite developments in the diagnosis and treatment of candidemia, mortality rates remain substantial, with an overall mortality of 30% to over 50% and attributable mortality of 19% to 38%.
CLINICAL PRESENTATION
Clinical manifestations of candidemia are variable and depend on host immune factors and the extent of infection. Symptoms range from a low-grade fever to sepsis. Skin lesions may also occur and often appear as small pustules or nodules with surrounding erythema, but appearance can be variable, and patients may even develop large, necrotic lesions.
Candidemia can also be associated with metastatic foci of infection through hematogenous seeding. Commonly involved sites include heart valves, spleen, liver, central nervous system, joints, and bones.
Candidemia can also result in endovascular seeding of the highly vascular choroid plexus in the eye, causing chorioretinitis or endophthalmitis. The possibility of Candida chorioretinitis should be evaluated in all patients with candidemia regardless of symptoms because many patients lack visual symptoms early in the course of illness.
Failure to identify Candida chorioretinitis may result in loss of vision due to inappropriate or inadequate duration of treatment, which should be a minimum of 4 to 6 weeks.
DIAGNOSIS
Blood cultures have been the standard diagnostic tool for candidemia, but the sensitivity of traditional blood culture methods has been only about 50%. However, newer automated culture modalities likely have significantly better performance characteristics.
Fungal culture and direct microscopic examination of a biopsy or drainage sample from possible focal sources of infection, including skin lesions and abscesses, provide important additive diagnostic ability.
Growth in specialized chromogenic media can expedite identification of certain Candida species.
More rapid identification methodologies, such as the antigen-based assay β-D-glucan, have been used as an adjunct for diagnosis in some invasive fungal infections.
The β-D-glucan test detects a cell wall antigen present in most fungi. However, its presence in multiple types of fungi also makes the test less specific for use in the diagnosis of candidemia. Pooled sensitivity and specificity for all invasive fungal infections are 76.8% and 85.3%, respectively. The β-D-glucan test should be approached with the caveat that it cannot distinguish Candida infections from those caused by other fungi. Identification and isolation of the particular organism by other means is still necessary to make a definitive diagnosis and to tailor appropriate therapy.
Consultation with an institution’s clinical microbiology department or an expert in the diagnosis and management of patients with fungal disease should be initiated to discuss performance characteristics of diagnostic tests available at the institution and to aid in the interpretation of the results. These individuals are also knowledgeable of institutional protocols to optimize chances of isolating Candida species.
Historically, Candida albicans was the most common species involved in nosocomial candidemia, but over the past decade, there has been a progressive shift toward nonalbicans Candida species. These non-albicans species now outnumber C. albicans in many health care institutions. This increase is generally thought to be the consequence of increased use of broader-spectrum antifungal agents.
Identification of the species responsible for infection is important, as each species has a different antifungal susceptibility pattern (Table 39-1). Within their own institutions, clinicians should be aware of the most common species of Candida and the susceptibility profiles.
MANAGEMENT
The selection of empiric therapy for any patient with candidemia, pending identification of the species, should take into consideration the severity of illness, comorbidities, previous history of Candida infection, exposure to or intolerance to certain antifungal agents, and available susceptibility reports. Consultation with an expert familiar with the management of patients with serious fungal infections is advised.Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
