Development of a lateral flow immunochromatographic assay for the detection of Lactococcus garvieae in grey mullet (Mugil cephalus)

Lactococcosis, the disease caused by Lactococcus garvieae, is one of the most prevalent bacterial diseases affecting grey mullet (Mugil cephalus) aquaculture. In this study, a lateral flow immunochromatographic assay (LFIA) was developed for the rapid detection of L. garvieae in grey mullet. The monoclonal antibody (mAb) 74C10 was used to target L. garvieae, both in a colloidal gold-mAb conjugate and as the capture antibody on the test line. The LFIA results would be visualized on LFIA strip within 10 min after the application of bacterial suspensions and spleen tissue lysates diluted in sample buffer in separate tests. The detection limit of the LFIA strip for L. garvieae was 4.25 × 10⁴ colony-forming units (CFU)/100 µL, with no cross-reactivity against eight other fish bacteria. When compared with CFU testing of 23 spleen samples from L. garvieae-infected mullet, the LFIA strip showed a significant correlation (p < 0.01) with bacterial concentrations. Field validation of the assay using spleens from 50 infected and 50 non-infected mullet demonstrated a specificity of 100%, sensitivity of 98%, and diagnostic effectiveness of 99%. Thus, the developed LFIA strip represents a useful tool for rapid detection (within 10 min) of L. garvieae in diseased mullet at aquaculture facilities.