4. Discussion
Analysis of CT production is critical for accurate diagnosis of
cholera because, even if V. cholerae is isolated from patient,
we cannot attribute the symptoms to the isolated V. cholerae
bacterium without verification of ability to produce CT. In
this study, we constructed CT-IC with the lower detection
limit of 10ng/mL CT which is comparable to the detection
limit of commercially available RPLA (1–3 ng/mL) [10]. Although
both IC and RPLA are the simple and rapid detection
techniques, the detection limits of them are not sufficient for
direct detection of CT from stool sample. It was reported that
CT concentrations in most of the patient stools were lower
than 10 ng/mL, even though the concentrations of CT in
patient stools vary, ranging from 26 pg/mL to >100 ng/mL
[15]. For some toxigenic bacteria, including thermostable
direct hemolysin- (TDH-) producing V. parahaemolyticus
and Shiga toxin (Stx-) producing E. coli, it had been reported
that precultivation by using enrichment media is helpful for
immunochromatographic identification of toxigenic bacteria
fromstool or food sample [16, 17]. In the case of CT detection,
alkaline peptone water (APW) is expected to be useful as the
enrichment media. APW is most commonly used media for