Free-living amoebae recovered from human stool in Strongyloides agar culture

Our laboratory in The Gambia, West Africa, performs Koga agar (1.5% bacteriological agar, 0.5% sodium chloride, 0.5% meat extract, 0.1% bacteriological peptone) culture for larvae of strongyle nematodes on human fecal samples for which parasitological investigation has been requested. We have recovered free-living amoebae (FLA) from human fecal specimens on two occasions over a period of 9 months (representing 130 individual fecal cultures) on this agar (Fig. 1). The amoebae in both cases were identified as Hartmannella species based upon the morphology of trophozoites and cysts in agar culture (Fig. 2) and their inability to enflagellate in distilled water after 8 h of incubation at 37°C. No other types of FLA have been recovered. Due to resource constraints, sequencing of the partial 18S rRNA gene and internal transcribed spacer (ITS) region could not be performed, and this identification must remain presumptive. Specimens were collected into sterile containers, and Koga culture plates were sterile and sealed with Parafilm prior to incubation at 30°C for 5 days; therefore, environmental contamination with FLA was very unlikely. Repeat specimens could not be obtained from subjects, and so it was not possible to determine if these findings represent transient passage of FLA or true intestinal colonization.