Effects of Temperature on Host−Pathogen−Drug Interactions in Red Abalone, Haliotis rufescens, Determined by ¹H NMR Metabolomics

The antibiotic oxytetracycline (OTC) has shown immense promise for combating the causative agent of Withering syndrome (WS), a Rickettsia-like procaryote (WS-RLP) that has severely impacted California abalone (Haliotis spp.) populations. Using histology and nuclear magnetic resonance (NMR) spectroscopy based metabolomics, the effects of OTC treatments (10, 20, or 30 days) on WS-RLP infected abalone in seawater temperatures of 13.4 ± 1.2 and 17.3 ± 1.3 °C were investigated over 160 days. The highly efficacious nature of OTC in combating WS-RLP at both temperatures was demonstrated by histology. Metabolomics revealed, however, that the most significant metabolic changes in foot muscle depended upon posttreatment duration, irrespective of treatment and temperature. This was quite unexpected and would have been overlooked using histology alone. Metabolic changes in all animals at both temperatures included decreased levels of amino acids and carbohydrates and elevated taurine, glycine-betaine, and homarine. Subtle metabolic differences between OTC-treated and untreated abalone were observed at 17.3 °C only. These findings provide clear evidence that OTC eradicates WS-RLP which in turn reduces the metabolic decay associated with WS at elevated seawater temperature. Furthermore, this study documents the sequential metabolic changes that occur during pre-clinical WS, and demonstrates the application of metabolic phenotyping for understanding environmental effects on host−pathogen−drug interactions.