September 11, 2019

Hospitalizations for skin and
soft tissue infections, or SSTIs, are rising in frequency. According to a recent AHRQ study,
hospital stays with a principal diagnosis of SSTI grew
75% from 1997 to 2010. There’s no clear explanation for this phenomenon although it is
likely due in part to the rise in community-acquired methicillin-resistant
staph aureus or MRSA infections. According to the 2014 Infectious
Diseases Society of America guidelines, the first step in diagnosing and
managing skin and soft tissue infections is determining if
the process is purulent or non purulent. Purulent SSTIs include furuncles, or boils, carbuncles, and
cutaneous abscesses. Non purulent skin and
soft tissue infections include erysipelas, cellulitis, and necrotizing fasciitis. This clinical distinction is
critical as the management of both groups of infections differs. Incision and drainage or
I and D is necessary for the resolution of purulent SSTIs. And according to the 2014 IDSA guidelines,
antibiotics, as an adjunct to IND, are only recommended if patients have
severely impaired immune systems or evidence of a systemic
inflammatory response. Next, clinicians must determine if
their patient has mild, moderate or severe disease. Patients without signs to suggests
a systemic inflammatory response qualifies having mild infection. The majority of skin and
soft tissues infections in the U.S. are mild, and
can be treated in an out-patient clinic. Purulent SSTIs can be
treated with I & D alone, while patients with non-purulent
SSTIs can be treated with empiric oral antibiotics effective
against the common pathogens, namely group A Streptococcus, plus or
minus methicillin sensitive staphoreous. Patients with typical SSTIs together
with signs to suggest a system inflammatory response have
infections of moderate severity. The guidelines recommend that patients
with purulent SSTIs of moderate severity be managed with I & D plus empiric oral
antibiotics with activity against MRSA, namely Trimethoprim-Sulfamethoxazole
Doxycycline or clindamycin. Patients with nonpurulent SSTIs of
moderate severity should be treated with intravenous antibiotics directed
against Streptococcus and methicillin sensitive staph aureus. As discussed earlier, the patient in
this case had non-purulent cellulitus of moderate severity when she was admitted,
and should’ve been started on antibiotics targeted against streptococcus and
methicilin sensitive staph aureus alone. The IDSA guidelines include patients who
fail initial management among those with severe infections. They suggest broadening antibiotic therapy
in these patients to include anti-MRSA coverage, as well as coverage directed
against gram negative organisms in specific situations,
like necrotizing fasciitis. So that begs the question, has this patient failed her
initial antimicrobial management? the involved area of her leg has not
changed significantly since admission. And she has received broad spectrum
antibiotics for almost 48 hours. Most patients treated with the right
antibiotics begin to improve symptomatically by 24 to 48 hours
after the initiation of therapy, but some do not see improvement for 72 hours. According to the FDA Guidelines for
SSTI studies, a clinical response is defined as the cessation of spread or
reduction of size of the SSTI, plus resolution of fever 48 to 72
hours after starting antibiotics. In this patient’s case,
she meets the general criteria for a positive clinical response. She is afebrile, her tachycardia has
resolved, and the arythema, edema, and tenderness have not spread since
the initiation of antibiotics. Thus her antibiotics have not failed,
they’ve worked. In the absence of specific
epidemiologic risk factors most SSTIs are caused by Streptococcus or
Staphylococcus species. As previously discussed,
her initial antibiotic regimen was inappropriate because it was overly broad,
providing gram negative, and anti MRSA activity when it wasnt needed,
and is actually contraindicated now, in the era of rising clostridium
difficile infection rates, and the emergence of multi
drug resistant organisms. For that reason it is
appropriate to de-escalate her therapy now to a regiment that would
have been appropriate from the start. In this case, cefazolin. It is important to clarify what
might already seem obvious to you. You do not have to wait until the 48
hour timeout to make this switch. You could have done it as
soon as you began to care for the patient based upon her presentation
and the likely microbiologic ideology. Given her clinical scenario you could
consider making an IV to PO switch during your 48 hour time out. She has improved clinically, although you don’t know if
she’s taking oral medications. In this case,
the narrowest agent with antistrep and antiemesis activity as well as good
oral bioavailability is Dicloxacillin. Other potential options
with broader coverage but good oral bioavailability include
Cephalexin, Doxycycline, and Clindamycin. Again, these oral antibiotics can be
used from the start in mild cases of nonpurulent cellulitis. If your patient is not responding to, or slowly recovering on antibiotics,
it is important to consider non-infectious etiologies that
can masquerade as cellulitis. Stasis dermatitis may be the most common. Stasis Dermatitis describes the chronic
skin changes associated with chronic venous insufficiency including
erythema and desquamation. It is typically bilateral, which is
very uncommon in acute cellulitis. And Stasis Dermatitis is
typically non-tender. Lipodermatosclerosis in its acute form
is a common cause of pseudo cellulitis. It is a severe fibrosing panniculitis
of the subcutaneous tissue, and is another consequence of
chronic venous insufficiency. This process typically starts near
the medial region of the ankle and progresses to involve
the leg circumferentially. The leg then takes on the appearance
of what’s called the inverted champagne bottle. In its acute form, the affected region can
be erythematous, tender, and edematous. Although these patients may
be at an increased risk for acute cellulitis due to their abnormal
skin, the chronicity of their symptoms, which can last for months In the absence
of systemic symptoms can help you make the distinction
from acute cellulitis. Contact Dermatitis, both irritant and
allergic, often present with erythematous patches limited for the most part
to the area of initial exposure. The lesions can be warm and
painful, but again, systemic signs of infection are absent. Other mimics include thrombophlebitis,
drug reactions, radiation recall syndromes,
and insect stings or bites. For a more in depth discussion of
non-infectious etiologies that are often confused with SSTIs please see
the two articles lifted in the for further reading section of this case.

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