Session: EV022 Parasitic diseases and international health Category: 7a. Diagnostic parasitology 22 April 2017, 08:45 - 15:30 EV0362 Blastocystis hominis and PCR: contributions and doubts Jonathan Fernandez-Suarez*1, Jose Boga2, Azucena Rodriguez-Guardado3, Christian Sabater2, Ana Fernández-Blazquez2, Alvaro Leal2, Fernando Vazquez2 1Hospital Universitario Central de Asturias; Huca _; Microbiologia Y Parasitologia 2Hospital Universitario Central de Asturias; Microbiology 3Hospital Universitario Central de Asturias; Infectious Diseases Background: Blastocystis hominis is a protozoan that is found with a high frequency in stools. Its pathogenicity is controversial, being related to the amount of microorganisms, the genotype and the presence of other concomitant pathogens. When is symptomatic, it has been associated with diarrhea or abdominal pain. Classic microbiological diagnosis has been performed through microscopy of concentrated stools. Recent genomic amplification techniques must be evaluated comparing the results with the microscopy and relating them to clinical or epidemiological parameters. Material/methods: During a 6-month period (March-August 2016) the detection of Blastocystis hominis was compared using 2 techniques: 1.Microscopic visualization of the concentrated stools (Copropack SAF, Difco®). 2.Multiplex real-time(rt)-PCR (Seegene Allplex®), which detects 6 pathogenic protozoa (Giardia lamblia, Cryptosporidium parvum, Cyclospora cayetanensis, Entamoeba histolytica, Dientamoeba fragilis and Blastocystis hominis). The rt-PCR results were compared with microscopy. Subsequently we analyzed the age and gender of the patients, the seasonality, the related clinical diagnosis and the presence of another parasites. The techniques were compared in a single sample per patient. Results: 1902 samples were studied. Blastocystis hominis was detected microscopically in 196 (10.3%) and by rt-PCR in 926 (48.7%). Microscopy detection was inversely proportional to threshold cycle (Ct) in which they were detected by rt-PCR, with virtually no positives by microscopy above cycle 30 (Table 1). Table 1 Positive samples (Total samples:1902) Ct rt-PCR+ Microscopy+ % Microscopy+/rt-PCR+ <20 83 57 68,7 20-25 219 108 49,3 25-30 107 28 26,2 30-35 140 2 1,4 35-40 266 1 0,3 40-45 111 0 0 TOTAL 926 196 21,2 No significant differences were observed in terms of gender or seasonality, regardless of the technique. It was observed (very significantly by microscopy) that Blastocystis hominis is present in all ages equally except for 0 to 5 years (2.3% and 35.3% of positives by microscopy and rt-PCR respectively) (p<0.0001 and p=0.0161, respectively). It was also observed a greater relationship at clinical level with abdominal pain than with diarrhea, objecting only by microscopy (12.5% vs 7.8% of positive patients) (p=0.0154). The relationship between positive microscopy and presence of other parasites was extremely significant. Positive microscopy showed more parasites in 55.6% of the samples compared to 30.5% with negative microscopy (p<0.0001). Conclusions: 1.rt-PCR has a much higher sensitivity than microscopy. Cts obtained can be used quantitatively to discriminate between symptomatic and asymptomatic parasites, but further studies are necessary. Results should therefore be interpreted with caution. 2.Blastocystis hominis has a lower incidence in children under 5 years of age, with no differences due to gender or seasonality. Abdominal pain is related to a greater presence of Blastocystis hominis. 3.The presence of more parasites are clearly more frequent in samples with a higher load of Blastocystis hominis: a marker of multiple parasitic infection?..