It
needs to be read in the original but here are a few key points:
When
is MRSA coverage needed?
From
the article:
There
has been increasing concern about antibiotic-resistant bacteria, such
as community-acquired methicillin-resistant S aureus (MRSA), which is
reflected in the increased use of anti-MRSA antibiotics (eg,
vancomycin, trimethoprim-sulfamethoxazole, doxycycline, clindamycin)
and broad-spectrum gram-negative antibiotics (eg,
β-lactam/β-lactamase inhibitors, levofloxacin, ceftriaxone) during
the past decade.40 However, most cases of cellulitis do not involve
gram-negative organisms, and in cases of nonpurulent and
uncomplicated cellulitis, the addition of antibiotics against
community-acquired MRSA did not improve outcomes.41 As such,
narrow-spectrum antibiotics against Streptococcus and
methicillin-sensitive S aureus remain appropriate. In purulent
cellulitis (presence of a pustule, abscess, or purulent drainage), S
aureus infection is more likely, as demonstrated by a study of 422
patients who presented with “purulent skin and soft tissue
infections” to 11 emergency departments throughout the United
States, in which skin surface swab cultures revealed MRSA in 59% of
patients, methicillin-sensitive S aureus in 17%, and β-hemolytic
streptococci in 2.6%.42 Because methicillin-sensitive S aureus and
MRSA can be difficult to differentiate according to clinical features
alone,43 MRSA should be considered for purulent infections in known
high-risk populations, such as athletes, children, men who have sex
with men, prisoners, military recruits, residents of long-term care
facilities, individuals with previous MRSA exposure, and intravenous
drug users.44
The
authors also recommend MRSA coverage for non purulent
cellulitis in certain situations: severe systemic manifestations,
rapid spread and immune compromise.
When
should the spectrum be extended beyond staph and strep (eg anaerobes,
gram negatives)?
Severe
systemic manifestations, immune compromise, rapid spread.
What
if purulent cellulitis is mild and can be treated with oral
antibiotics?
Consider
confining the coverage to strep and MSSA (but not MRSA). But if MRSA
is deemed important to cover TMP/SMX, doxy or clinda may be
acceptable (as well as, of course, linezolid).
What
are some unusual organisms to consider in special situations?
Traditional
(pharmacologic) immunosupression, HIV: strep pneumo, Mtb, gram
negatives, crypto species.
Chronic
liver disease, CKD: vibrio species ( including vulnificus), gram
negatives (including pseudomonas).
When
should nec fash (and other complications) be considered?
From
the article:
In
cases of suspected necrotizing fasciitis, early surgical assessment
is recommended; however, laboratory testing may help differentiate
cellulitis from early evolving necrotizing fasciitis. Wall et al75
found in a modeling study that a white blood cell count greater than
15 400 cells/mm3 or serum sodium level less than 135 mEq/L could
suggest a diagnosis of necrotizing fasciitis with a sensitivity of
90%, specificity of 76%, positive likelihood ratio of 3.75, and
negative likelihood ratio of 0.13. Similarly, Wong et al76 developed
the Laboratory Risk Indicator for Necrotizing Fasciitis score
according to white blood cell count and levels of C-reactive protein,
hemoglobin, serum sodium, creatinine, and serum glucose, which had a
sensitivity of 90%, specificity of 95%, positive likelihood ratio of
19.95, and negative likelihood ratio of 0.10. Finally, Murphy et al77
identified that for necrotizing fasciitis among cases in their
series, a serum lactate level of 2.0 mmol/L had a sensitivity of
100%, specificity of 76%, positive likelihood ratio of 4.17, and
negative likelihood ratio of 0. All of these tests are offered as
adjunctive tools, along with history, physical examination, and
surgical exploration, to guide diagnosis of necrotizing fasciitis.
Imaging
studies are not diagnostic of cellulitis but can help distinguish it
from more severe forms of infection and can identify drainable fluid
collections, such as abscesses. Osteomyelitis can sometimes
complicate cellulitis and when suspected can be best ruled out with
magnetic resonance imaging or radiography, if chronic. Furthermore,
magnetic resonance imaging or computed tomography can help
differentiate cellulitis from necrotizing fasciitis or pyomyositis.78
The appearance of gas on computed tomography scan in the absence of
soft tissue trauma or a rim-enhancing fluid collection, as would be
found with an abscess, is considered pathognomonic of, but not
requisite for, a diagnosis of necrotizing fasciitis.79- 81 A recent
study evaluating the utility of modern-day computed tomography
scanners demonstrated a positive predictive value of 76% and a
negative predictive value of 100% and found that only 36% of cases of
necrotizing fasciitis included gas.82
In
cases of non response to treatment consider cellulitis mimics and
possible derm consultation
Mimics include stasis dermatitis, calciphylaxis, erythema migrans and
other conditions.