Acanthamoebaspp. in Urine of Critically Ill Patients

Acanthamoeba spp. in Urine of Critically Ill PatientsTo the Editor: Free-living amebae are ubiquitous protists able to endure extreme temperature and pH in diverse environments (1).In past decades, interest in them increased as causes of infections, such as keratitis (2) and granulomatous encephalitis (3).Acanthamoeba spp.can harbor pathogenic microorganisms as endosymbionts, such as bacteria (e.g., Legionella spp., Pseudomonas aeruginosa, and Vibrio cholera), fungi, and mycobacteria (4).The occasional observation of amebae in urine specimens in a clinical microbiology laboratory (by L.C.S.) motivated our study.To estimate the prevalence of Acanthamoeba spp. in urine, on March 3 and 4, 2008, we collected urine samples from indwelling urinary catheters of all critically ill patients in the intensive care units of a tertiary care 2,000-bed university hospital (Hospital das Clínicas, University of São Paulo).Medical records were evaluated for patient age, sex, underlying diseases, length of hospital stay, use of central venous catheter, mechanical ventilation, antimicrobial drug use, and duration of urinary catheterization.Chemical urinalysis was performed by using a urine dipstick (Uriquest; Labtest Diagnostica, Lagoa Santa, Minas Gerais, Brazil), and urine leukocyte and erythrocyte counts were performed.Samples were examined microscopically and cultured for amebae.Amebae were characterized on the basis of morphologic criteria (cyst morphology and trophozoite shape and motility) (5).For ameba culture, 10 mL of urine was centrifuged at 2,500 rpm for 5 min.The supernatant was discarded, and the sediment (1 mL) was added to 5 mL of brain heart infusion (Oxoid, Cambridge, UK).Cultures were incubated at 25 o C for