Although it has not spread so far, the possibility that MRSA could eventually overwhelm even last-line drugs such as vancomycin is a very serious one, scientists said, branding it "a dangerous organism in hospitals".
US researchers form Harvard University, the Massachusetts Eye and Ear Infirmary in Boston and the Broad Institute in Cambridge found that since 2002, there have been 12 cases of the antibiotic-resistant superbug clonal cluster 5 (CC5) -- a deadly strain of methicillin-resistant Staphylococcus aureus or MRSA.
"MRSA strains are leading causes of hospital-acquired infections in the US, and CC5 is the predominant lineage responsible for these infections," the researchers said.
"There have been 12 cases of vancomycin-resistant S aureus (VRSA) infection in the US since 2002 -- all CC5 strains. Vancomycin is a key last-line bactericidal drug for treating these infections," they added.
In the study, published in the American Society for Microbiology, the team sequenced the genomes of all available vancomycin-resistant MRSA strains to find what distinguishes them from other lineages and why CC5 is apparently more adept than other strains at picking up vancomycin resistance.
It was found that vancomycin-resistant MRSA strains and other CC5 lineages have some important differences from other types of MRSA, including adaptations that allow them to co-exist with other types of bacteria and may help them take up foreign DNA.
It was also found they lacked a set of genes that encode an antibiotic protein made by bacteria to kill other bacteria.
"This is important because it enables CC5 to get along well with other bacteria in mixed infections. Instead of killing off competing organisms, CC5 aims to co-exist. This enables it to pick up genes, like the one that encodes vancomycin resistance, from unexpected places," they said. (More)
