Hansa Done and Rolf Halden, researchers at that University’s Biodesign Institute, measured the presence of 47 antibiotics in species such as shrimp, salmon, catfish, trout, swai and tilapia, originating from 11 countries.
Using liquid chromatography/tandem mass spectrometry (LC–MS/MS), they found traces of oxytetracycline in wild shrimp, farmed tilapia, farmed salmon and farmed trout.
And they detected 4-epioxytetracycline in farmed salmon, sulfadimethoxine in farmed shrimp, ormetoprim in farmed salmon, and virginiamycin in farmed salmon that had been marketed as antibiotic-free.
The research findings were published in the online edition of the Journal of Hazardous Materials.
Oxytetracycline, the most commonly used antibiotic in aquaculture, was the most prevalent in the study samples.
The researchers said they also found traces of that antibiotic in wild-caught shrimp imported from Mexico, which the authors suggest may be due to mislabeling, coastal pollution from sewage contamination, or cross-contamination during handling and processing.
They said all the seafood analyzed was found to be in compliance with US Food and Drug Administration (FDA) regulations, suggesting that “they are chemically safe to consume.”
However, they note that sub-regulatory antibiotic levels can promote resistance development, according to their "extensive meta-analysis" of existing literature.
Burgeoning industry
Aquaculture, say the authors, has undergone rapid growth to meet the burgeoning global demand, nearly tripling over the past 20 years to an estimated 83 million metric tons in 2013.
The large increase has led to widespread antibiotic use, applied both to prevent and treat pathogens known to infect fish.
“As production surges, many aquaculture facilities resort to antibiotics to combat diseases in an environment that creates ample opportunities for bacterial pathogens to thrive.
Antibiotics are also commonly used as a prophylactic, sometimes on a daily basis. Although some promising alternatives such as short-chain fatty acids and bacteriophage therapy have been proposed, many are not ready for mass usage.
Developed vaccines show promise in reducing antibiotic usage, but are only available to treat certain diseases and are not as cost-effective as antibiotics. Thus, the usage of antibiotics in aquaculture remains high,” said the team.
The researchers say the broad effects on health and the environment associated with these practices remain speculative.
“Future studies are warranted to fully understand the connection between aquacultural use of antibiotics, development of drug resistance, human exposure to resistant pathogens, and ensuing morbidity and mortality in seafood consumers,” said the authors.
Source: Journal of Hazardous Materials
Title: Reconnaissance of 47 antibiotics and associated microbial risks in seafood sold in the United States
Published online ahead of print: DOI: 10.1016/j.jhazmat.2014.08.075
Authors: H Y Done, R U Halden