Growth kinetics and metronidazole sensitivity of Blastocystis spp. isolated from colorectal carcinoma (CRC) and non-CRC patients

Abstract

Background: Blastocystis spp. is the most common protist detected in human fecal samples in numerous studies globally.Until recently debate regarding its pathogenicity has been controversial. Some studies speculated a possible correlation between Blastocystis and colorectal carcinoma (CRC). No previous studies investigated the presence of non-genotypic differences in Blastocystis spp. isolated from CRC and non-CRC patients. Objectives:The present work aimed to investigate the growth kinetics (GK) and metronidazole (MTZ) sensitivity of Blastocystis isolates from CRC and apparent non-CRC symptomatic and asymptomatic Blastocystis carriers. Materials and Methods: Seven isolates from CRC patients, 6 from symptomatic and 6 from asymptomatic non-CRC carriers were cultured in Locke's Egg (LE) medium supplemented with bovine serum and antibiotic mixture, and incubated at 37°C. Mean viable organisms counts of each isolate were calculated every 24 h to follow their GK. Counts were repeated after exposure to different MTZ concentrations to test their drug sensitivity. Results: In vitro GK of CRC and non-CRC symptomatic isolates were nearly similar at 72 h incubation with apparently higher peaks attained by isolates from CRC patients than the slower growing non-CRC-asymptomatic isolates. MTZ-sensitivity of CRC isolates was nearly similar to that of non-CRC asymptomatic isolates; both were significantly more sensitive than the symptomatic isolates especially at high drug concentration of 200 µg/ml of the medium. Conclusion: The recorded difference in GK and MTZ sensitivity of Blastocystis spp. isolated from different clinical groups suggests the existence of certain biological characters with different pathogenic roles.