THERAPY VARIES BY SETTING
IDSA, and Canadian guidelines organize their approach to
CAP by clinical settingoutpatient or inpatient and,
for the latter, general ward or intensive care unit (ICU).
The CDC presented its guidelines in a Q&A format, providing
responses to such questions as What are suitable empirical
regimens for outpatient community-acquired pneumonia in
the era of drug-resistant Streptococcus pneumoniae?
Canadian guidelines address CAP in the nursing home, recommending
a fluoroquinolone alone in that setting or amoxicillin/clavulanate
in combination with a macrolide. A fluoroquinolone, especially
one of the newer formulations, was the top choice because
of concern about a rise in gram-negative organisms and anaerobes
in the elderly. However, there are no randomized, controlled
clinical trials to support this recommendation, Dr. Grossman
guidelines recommend a macrolide or doxycycline for empiric
treatment of outpatients with CAP. An oral anti-pseudomonal
fluoroquinolone is also acceptable in these cases, the IDSA
of the ATS only applies in the absence of both significant
cardiopulmonary disease and risk factors for drug-resistant
S pneumoniae, enteric gram-negative organisms, or
aspiration. A ß-lactam should be added to therapy if
either is present, the ATS says; the choices include high-dose
amoxicillin, amoxicillin/clavulanate, and some cephalosporins.
An anti-pneumococcal fluoroquinolone can be substituted
for the combination therapy.
most part, the IDSA gives no preference to any of the agents
it recommends for outpatient therapy, stressing that regional
drug susceptibility patterns should influence the selection.
However, it does suggest that a fluoroquinolone may be preferable
in older patients with significant underlying lung disease.
the Canadian guidelines state that in the absence of significant
lung disease and risk factors for gram-negative infection,
a macrolide should be the first-line agent, and doxycycline
an alternative. Because of their increased risk for infection
with Haemophilus influenzae, patients with obstructive
airways disease should be given one of the newer macrolides;
these agents have improved activity against that pathogen,
Dr. Grossman noted.
is best for outpatients who are at risk for gram-negative
infection, the Canadian guidelines state. An alternative
is to use either amoxicillin/clavulanate or a second-generation
cephalosporin plus a macrolide, they add.
difference in the CDC guidelines is that they do not recommend
a fluoroquinolone for empiric therapy of outpatients with
CAP. In fact, pointed out Dr. Grossman, the CDC typically
reserves these agents for patients in whom initial therapy
ON GENERAL WARDS
IDSA, and ATS guidelines make similar recommendations about
CAP therapy for patients on general hospital wards. In that
setting, the Canadian guidelines say that a fluoroquinolone
should be the first choice; a second- or third-generation
cephalosporin plus a macrolide is the next-best pick.
guidelines favor fluoroquinolone therapy because it is simpler
to administer. Furthermore, because the bioavailability
is about the same with intravenous and oral administration,
switching from one mode to the other is easy. And, in some
cases, it may be possible to start with oral therapy. That
would be extraordinarily cheap, Dr. Grossman commented.
recommendations for empiric CAP therapy on the wards include
fluoroquinolones but do not give them preference. Another
option in that setting is a macrolide plus a ß-lactam/ß-lactamase
inhibitor (preferably, cefotaxime or ceftriaxone), the IDSA
ward patients with cardiopulmonary disease or risk factors
for multidrug-resistant pathogens, the ATS recommends either
combination therapy with a ß-lactam and macrolide or
monotherapy with an anti-pneumococcal fluoroquinolone. In
a slight variation, the ATS suggests that parenteral azithromycin
alone may be acceptable if cardiopulmonary disease and risk
factors for multidrug resistance are absent. Intravenous
doxycycline and a ß-lactam are acceptable, however,
if a macrolide is not well tolerated. The CDC does not recommend
the use of fluoroquinolones for empiric treatment of ward
patients with CAP. Instead, the agency suggests that a ß-lactam
plus a macrolide be given.
WHO ARE CRITICALLY ILL
the guidelines recommend combination therapy for CAP in
the critically ill; however, the ATS, IDSA, and Canadian
recommendations suggest that the specific choice of agents
should usually hinge on the risk for Pseudomonas aeruginosa
infection. In the absence of such a risk, the ATS guidelines
suggest combining a ß-lactam with a macrolide or intravenous
anti-pseudomonal ß-lactam/fluoroquinolone combination
is indicated in at-risk patients, says the ATS. So is a
three-drug combination, which should typically include an
intravenous anti-pseudomonal ß-lactam, an aminoglycoside,
and either azithromycin or a non-pseudomonal fluoroquinolone.
patients with CAP and no risk factors for infection with
multidrug-resistant gram-negative organisms, such as P
aeruginosa, the IDSA guidelines recommend a ß-lactam/ß-lactamase
inhibitor plus a macrolide or fluoroquinolone. The IDSA
suggests an anti-pseudomonal agent plus a fluoroquinolone
for patients with structural lung disease, who are at high
risk of gram-negative infection.
an anti-pseudomonal fluoroquinolone (preferably parenteral
ciprofloxacin) with an anti-pseudomonal ß-lactam is
best for CAP in critically ill patients at risk for P
aeruginosa, say the Canadian guidelines; an anti-pseudomonal
ß-lactam/aminoglycoside/macrolide combination is another
option. In the absence of P aeruginosa risk, physicians
can combine a third-generation nonanti-pseudomonal
cephalosporin with a fluoroquinolone or macrolide, the guidelines
than base its recommendations for the ICU on P aeruginosa
risk, the CDC simply suggests using a ß-lactam in addition
to either a macrolide or fluoroquinolone in that setting.
The CDC makes no recommendations about anti-pseudomonal
therapy in critically ill patients with CAP, Dr. Grossman
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