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Prime targets
These populations are at
greater risk of acquiring CA-MRSA
-Children under two
-Minorities, eg Natives/Aboriginals and African-Americans
-Contact sports athletes
-Men who have sex with men
-Military personnel
-Prisoners
-Veterinarians, pet owners and pig farmers
Source: Guidelines for the
prevention and management of community-associated
methicillin-resistant Staphylococcus aureus:
A perspective for Canadian healthcare practitioners
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If you expect to keep seeing the
run-of-the-mill Staphylococcus aureus infections
you're used to, you may be in for a rude awakening.
The drug-resistant version of the bacteria (MRSA) has
broken out of the hospital and is spreading through
our communities. If the 'superbugs' behave as they did
south of the border, they could soon take over the lion's
share of infections across the nation.
"This is the pattern that has been
observed over the last two to three years in several
US centres such as Houston, where the rate of methicillin
resistance among community-associated isolates of S
aureus (CA-MRSA) has reached a staggering 75%,"
says Dr Michael Hawkes of the Toronto Hospital for Sick
Children's Department of Infectious Diseases. And there's
every indication we're headed in the same direction.
"Here in Ontario, for instance,
the rates are for the most part unknown, but the prevalence
is thought to be rising as in most sectors of the country,"
says Dr Hawkes. British Columbia is currently seen as
the epicentre of the nation's superbug problem, but
rates will likely rise even more in the near future,
warns Dr Hawkes. That's why he and several other authors
of a new set of caregiver guidelines for CA-MRSA (available
online at www.ccar-ccra.com/english/ca-mrsa.shtml)
contributed to a January 2 CMAJ commentary urging
Canada's doctors to act on these recommendations —
pronto.
BE
PREPARED
Canadian infectious disease specialists have had their
eye on CA-MRSA for some time (see our original report,
"Community-acquired staph on rampage", April 15 2006,
Vol 3, No 7, page 1). The practice guidelines, Dr Hawkes
says, have come at a critical time. "Canada is arguably
poised at the brink of an epidemic of MRSA in its communities,"
he says, citing the explosive growth of CA-MRSA infections
in several US cities as a sign of things to come.
The full guidelines originally
appeared a few months ago in the Canadian Journal
of Infectious Diseases and Medical Microbiology
— not exactly a popular read among Canadian physicians,
according to Dr John Conly, of the Foothills Medical
Centre in Calgary. "A small piece in the CMAJ,
which has a much greater readership, serves to highlight
the full guidelines" and is necessary to prepare clinicians
for the growing threat, he says (for a crash course,
see "Your guide to treating CA-MRSA", below).
Dr Kunyan Zhang, an infectious
diseases instructor at the University of Calgary and
CA-MRSA expert, also feels that the recommendations
were a long time in coming. "The guidelines are very
timely and will be extremely important for helping to
address the management and prevention of recently emerging
CA-MRSA infections," he says.
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Your guide
to treating CA-MRSA
Nip the superbug in the bud
with these general rules of thumb from infectious
disease expert Dr John Embil:
- Incision and drainage of
abscesses is of critical importance as it will
relieve pain and expedite resolution of the
infection.
- Thankfully, CA-MRSA is susceptible
to agents such as trimethoprim sulfamethoxazole
(TMP/SMX), doxycycline, clindamycin and quinolones
— traditional anti-staphylococcal antibiotics
like cloxacillin and cephalexin will not work.
- Use of an agent such as TMP/SMX
1 double strength tablet po bid (for
adults) for 10-14 days should be sufficient.
However, if group A streptococcus is speculated
to be involved in the infection, an agent such
as clindamycin with improved antistreptococcal
activity may be a superior choice.
See Dr Embil's accompanying
editorial on page 20
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KNOW
THE ENEMY
Not everyone is convinced that the rising incidence
of CA-MRSA will make life more difficult for physicians
and their patients. Some American physicians working
in areas where CA-MRSA is already endemic think that
news coverage of the infection is a tad overblown. Texan
internist Dr Chris Rangel, for one, doesn't buy the
'superbug' hype. He reminds us in his medical blog that
even good ol' methicillin-sensitive Staph aureus
(MSSA) is still plenty deadly if inadequately treated
and that there are several very effective treatments
for CA-MRSA. "There's little current evidence that CA-MRSA
is more virulent than MSSA," he notes.
Dr Zhang disagrees. He believes
the drug-resistant form of S aureus very much
lives up to its nickname. "I strongly agree with this
term superbug.' It's useful to emphasize its clinical
importance and potential for significant impact on human
health," he says.
CA-MRSA strains are genetically
distinct from the traditional hospital strains, have
different antibiotic susceptibility patterns and target
different populations (see "Prime targets" top),
Dr Hawkes explains. Furthermore, serious and sometimes
life-threatening infections due to CA-MRSA have been
described. "Authors have called CA-MRSA an 'old foe
with new fangs,'" he remarks. "The widespread dissemination
of MRSA clones in the community signals their adaptation
to survive and spread outside the hospital setting."
For those of you who haven't yet
seen cases of CA-MRSA, Dr Conly has only two words:
be prepared. Dr Hawkes concurs. "Awareness of CA-MRSA
among frontline physicians, public health practitioners
and other healthcare workers is important for the appropriate
treatment, prevention and control of CA-MRSA," he says.
"This is the reason for publishing and promoting awareness
of the national guidelines."
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