The Berlengas archipelago, off the Portugese coast, may be isolated, but it is not free of the pernicious super bugs that plague the rest of the world.
Migratory seagulls carry both antibiotic-resistant and harmless strains of the bacteria Enterococcus to the islands, which are a protected habitat for wildlife, including seagulls and other seabirds. Using seagull droppings, researchers characterized the proteins suspected to play a role in the bacteria's antibiotic resistance. (Genes are the instructions for producing proteins, some of which carry out various functions.)
Of the 57 samples they collected, 10 percent carried strains that contained one type of resistance to vancomycin, considered a drug of "last resort." In the 1980s, it was discovered that the antibiotic was ineffective against some Enterococcus infections.
Almost 95 percent of the bird-poop samples contained Enterococcus; it is naturally present (and benign) in human, seagull and other animals' guts. In humans, Enterococcus species are also responsible for urinary tract and other infections, and have been known to cause death, particularly in hospitals.
Antibiotic-resistant bugs evolve in response to overuse of antibiotics; however, this evolution is not happening directly within seagulls. Rather, as opportunistic feeders comfortable consuming human garbage, the birds pick up and carry such drug-resistant bacteria around with them, according to the researchers.
Studying the proteins produced by the bacteria provides insights not available by studying the genes that code for them. It is one of the best methods of investigating basic processes, such as the origination and progression of the disease, the researchers wrote in the Sept. 21 issue of the journal Proteome Science.
"Our comprehensive description of the proteins that we found may provide new targets for development of antimicrobial agents," said one of the researchers, Gilberto Igrejas from the University of Tras-os-Montes and Alto Douro, Portugal. "This knowledge may also help to identify new biomarkers of antibiotic resistance and virulence factors."