TUESDAY, May 13, 2014 (HealthDay News) -- A new study may
provide the best evidence yet that the superbug known as MRSA can
travel between humans and their pets, although researchers caution
that people shouldn't worry too much about the germ lurking in
their cats and dogs.
In the big picture, the findings reveal how the use of
antibiotics can affect germs that infect both people and animals,
explained study author Ewan Harrison, a research associate with the
University of Cambridge in England.
The research also shows how "infectious diseases in humans and
animals are intrinsically linked and should be seen as a single
problem to be addressed jointly by human and veterinary medicine,"
Methicillin-resistant Staphylococcus aureus, better known as
MRSA, causes infections in the skin, in the bloodstream and
elsewhere in the body.
Once mainly limited to sick people in hospitals and nursing
homes, MRSA has spread into the world at large, often infecting
healthy people such as prisoners and athletes who share supplies
like towels and razors. MRSA can be deadly, and it can't easily be
vanquished by antibiotics.
It's no secret that MRSA can travel between species. In one
well-known case, a newborn elephant at a zoo died after a human
taking care of her accidentally infected her with MRSA.
But while some types of MRSA appear "to be able to transmit
easily between different species, others seem to be restricted to
one or a small number of animal species, possibly due to specific
adaptations to one species making the bacteria less able to infect
others," Harrison said.
In the new study, the researchers sought to better understand
how MRSA travels between species. They analyzed the genetic makeup
of MRSA strains from cats and dogs in England and discovered
evidence of a "human source" for the germs in the animals.
The researchers also found evidence that the MRSA germs in the
animals were developing resistance -- immunity -- to the antibiotic
clindamycin, which veterinarians use in the U.K. The germs were
less likely to have developed immunity against the antibiotic
erythromycin, which is used less.
"This demonstrates how the use of antibiotics in both human and animals medicine can alter the population of a bacteria that can causes infections in both," Harrison said.
It's not clear if the same goes for other types of germs, he
Dr. J. Scott Weese, an associate professor with the department
of pathobiology at the University of Guelph in Canada, said the
study "doesn't change anything but does give more support to the
ongoing hypothesis that pet MRSA is ultimately usually human in
"Since MRSA in pets is usually human-associated, if someone's dog has MRSA, the owner is probably either the source or there's someone else in the household that is MRSA-positive and probably a greater source than the dog," he said.
What to do?
"Pet owners shouldn't be overly concerned directly about MRSA in their animals other than reinforcing the message of good hygiene when handling pets," Harrison said. Experts recommend frequent hand washing when a pet orhis or her human has a MRSA infection.
As for future research, "we are currently using similar genome
sequencing technology to understand transmission between humans and
animals in a veterinary hospital setting," Harrison said. "We also
hope to investigate larger collections of different types of MRSA
to discover whether the findings of our study are more general to
other types of MRSA."
The study was published online recently in
mBio, a journal of the American Society for
For more about MRSA, try the
Disease Control & Prevention.