ABSTRACT
With increasing resistance to anti-parasitic drugs, it has become more important to detect and recognize phenotypes of resistant isolates. Molecular methods of detecting resistant isolates are limited at present. Here, we introduce a microfluidic bioassay to measure phenotype using parameters of nematode locomotion. We illustrate the technique on larvae of an animal parasite Oesophagostomum dentatum. Parameters of sinusoidal motion such as propagation velocity, wavelength, wave amplitude, and oscillation frequency depended on the levamisole-sensitivity of the isolate of parasitic nematode. The levamisole-sensitive isolate (SENS) had a mean wave amplitude of 135 µm, which was larger than 123 µm of the levamisole-resistant isolate (LEVR). SENS had a mean wavelength of 373 µm, which was less than 393 µm of LEVR. The mean propagation velocity of SENS, 149 µm s-1, was similar to LEVR, 143 µm s-1. The propagation velocity of the isolates was inhibited by levamisole in a concentration-dependent manner above 0.5 µm. The EC50 for SENS was 3 µm and the EC50 for LEVR was 10 µm. This microfluidic technology advances present-day nematode migration assays and provides a better quantification and increased drug sensitivity. It is anticipated that the bioassay will facilitate study of resistance to other anthelmintic drugs that affect locomotion.
