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JAMDA 13 (2012) 75e79
JAMDA
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Controversies in Long Term Care
Swab Culture of Purulent Skin Infection to Detect Infection or Colonization
With Antibiotic-Resistant Bacteria
Paul Drinka MD, CMD a, *, Phyllis Bonham PhD, MSN, RN, CWOCN, DPNAP, FAAN b,
Christopher J. Crnich MD, MS c
a
Internal Medicine/Geriatrics, University of Wisconsin, Madison, Medical College of Wisconsin, Milwaukee, Waupaca, WI
Wound Care Education Program, Medical University of South Carolina, College of Nursing, Charleston, SC
c
Section of Infectious Diseases UWSMPH, Middleton VA Hospital, Madison, WI
b
a b s t r a c t
Keywords:
Purulent Skin Infection
Swab Culture
Multidrug Resistant Organisms
Long term Care
Prescribing systemic antibiotics without susceptibility testing has significant shortcomings, especially in
long term care facilities with high rates of multidrug-resistant organisms (MDROs) including methicillinresistant Staphylococcus aureus. Tissue biopsy or aspiration sampling of infected tissue is the “gold
standard” for culture of skin and soft tissue infection and is especially important with serious infection,
systemic toxicity, or failure of initial therapy. Swab cultures are probably the most commonly used
method to determine the resistance pattern of skin pathogens treated in nursing home residents.
However, they are controversial, especially when obtained from chronic wounds. The culture may be
obtained from an uninfected wound and lead to unnecessary antibiotic therapy. If material superficial to
the infected living tissue is sampled, colonizers may be isolated. This report is focused on swab culture
obtained by the Levine technique, after debridement or cleaning down to viable tissue when an acute
purulent skin infection has been diagnosed based on clinical criteria. Swab cultures should not be used to
determine IF a wound is acutely infected; rather the role may be to identify potential pathogens when
deep tissue biopsy is not elected. The swab culture may identify the pathogen or overlying MDRO
colonization, a risk factor for MDRO infection. MDRO isolation should heighten the clinician’s level of
concern if the prescribed antibiotic did not “cover” the MDRO or potential pathogen that was isolated.
Properly performed swab cultures could play a role in the identification of methicillin-resistant Staphylococcus/MDRO infections treated in nursing homes.
Copyright Ó 2012 - American Medical Directors Association, Inc.
One of the authors reviewed a legal case in which a resident
almost lost a leg because debridement and culture of an infected
wound were not performed. Later, when the infection was severe,
the resident finally received debridement and culture. None of the
infecting organisms were sensitive to the empiric antibiotics
prescribed. It is not uncommon for nursing home clinicians to rely
on empiric systemic antibiotics and to forego culture.
Skin and soft tissue infections (SSTIs) are the third most
common infection in nursing homes.1 This report addresses
whether antibiotic therapy for mild acute purulent SSTI treated in
the nursing home should be empiric or proceeded by culture.
Perhaps the most common type of acute purulent SSTI encountered
in nursing homes develops within a chronic wound. These infections are considered to be “complicated.”
* Address correspondence to Paul Drinka, MD, CMD, Clinical Professor of Internal
Medicine/Geriatrics, University of Wisconsin, Madison, Medical College of
Wisconsin, Milwaukee, N3379 Bailey Street, Waupaca, WI 54981.
E-mail address: [email protected] (P. Drinka).
According to the Infectious Disease Society of America (IDSA),
mild acute infections are defined as those in which cellulitis is
limited to the skin or superficial subcutaneous tissue; and extends
2 cm around an ulcer without systemic manifestations.2 Practitioners should be aware of the fact that chronic venous stasis or
other conditions may produce an inflammatory dermatitis that can
be confused with cellulitis and lead to unnecessary antibiotic
treatment.3 Moderate to severe infections include cellulitis
extending >2 cm around an ulcer, lymphangitic streaking, spread
beneath the superficial fascia, deep-tissue abscess (fluctuance,
induration), gangrene/necrosis, and involvement of muscle,
tendon, joint or bone, systemic toxicity, or metabolic instability
(e.g., fever, chills, tachycardia, hypotension, vomiting, confusion,
leukocytosis, acidosis, severe hyperglycemia, or azotemia).2 A
wound may require careful inspection following debridement
initially and over time to determine if acute infection exists and
which structures are involved.
Given significant rates of community-associated methicillinresistant Staphylococcus aureus (MRSA) skin infection; the recently
1525-8610/$ - see front matter Copyright Ó 2012 - American Medical Directors Association, Inc.
doi:10.1016/j.jamda.2011.04.012
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P. Drinka et al. / JAMDA 13 (2012) 75e79
published IDSA Guideline on the Treatment of MRSA Infections
recommends obtaining cultures to guide systemic antibiotic
therapy in purulent skin infections (e.g., associated with purulent
drainage or exudate).4 In addition, the IDSA Guideline on the
Management of Diabetic Foot Infections recommends obtaining
cultures prior to starting antibiotic therapy.2 On the other hand, the
IDSA long term care (LTC) guideline seems to favor starting initial
antibiotic therapy in mild skin infections without obtaining
a culture: Gram stain and bacterial cultures “may be appropriate in
special circumstances in which unusual pathogens are suspected
fluctuant areas suggest an abscess, or initial antibiotic therapy has
been unsuccessful,” based on the “opinions of respected authorities.”5 The AMDA Guideline on Pressure Ulcers states: “Surface swab
cultures are not recommended because they cannot differentiate
infection from contamination or colonization.”6 We agree that
a swab culture should not be used to determine IF a wound is
acutely infected; rather, the role may be to identify potential
pathogens in a wound that is acutely infected based on clinical
assessment when deep tissue biopsy is not available or elected. In
our opinion, nursing home clinicians who treat purulent skin
infections with systemic antibiotics without obtaining a culture do
so based on expert opinion only. Expert opinion is divided, creating
a “Clinical Controversy.”
Empiricism has significant shortcomings, especially in LTC
facilities with high rates of multidrug-resistant organisms
(MDROs). MRSA is a prominent pathogen in acute SSTI. Empiric
coverage of S. aureus is recommended in a large proportion of skin
infections regardless of severity. Enterococcus, Pseudomonas aeruginosa, and other gram-negative rods may also express resistance to
commonly used antibiotics.2 Residents with MDRO/MRSA infections may receive antibiotics that fail to cover the MDRO with
disease progression. On the other hand, if the empiric antibiotic
“covers” MDRO, lack of culture results precludes de-escalation of
broad-spectrum antibiotic therapy. This will lead to unnecessary
antibiotic pressure and selection of resistant organisms.
Biopsy of viable tissue and/or aspiration of infected secretions
represents the gold standard for the bacteriologic diagnosis of SSTI.
These techniques are especially important in serious infection,
systemic toxicity, or failure of initial therapy. The IDSA Clinical
Practice Guideline (CPG) for the diagnosis and management of SSTI
states that: “Needle aspiration and punch biopsy specimens as well
as requests for a surgical consultation for inspection, exploration,
and/or drainage” should be performed in severe SSTI.3 On the other
hand, mild acute wound infection is often managed in nursing
homes without tissue biopsy or aseptic collection of infected
material through intact skin by aspiration. In reality, the clinician
must chose to prescribe systemic antibiotics empirically or perform
a swab culture. This report is focused on swab culture obtained by
the Levine technique after debridement or cleaning down to viable
tissue.7 Data are sparse. Swab culture should not be used to
determine IF the wound is acutely infected but rather the role is to
identify potential pathogens in a wound that is acutely infected
based on clinical assessment when deep tissue biopsy is not elected. A properly performed swab culture may be especially relevant
in the detection of MDRO/MRSA. The swab culture may identify the
pathogen or overlying MDRO colonization, a risk factor for MDRO
infection.8e10
Structure and Bacteriology
Aerobic gram-positive cocci are the predominant microorganisms that colonize and acutely infect breaks in the skin. S. aureus
and the beta-hemolytic streptococci are the most commonly isolated pathogens. Chronic open wounds provide “fertile ground” for
colonization with MDRO and may support complex biofilm flora
with large numbers of bacteria including aerobic gram-positive
cocci, enterococci, various Enterobacteriaceae, P. aeruginosa,
sometimes other nonfermentative gram-negative rods, and obligate anaerobes. Bacterial virulence factors and local conditions
(e.g., necrotic tissue, ischemia, hyperglycemia, trauma, maceration)
may allow planktonic bacteria to invade surrounding living tissue
to produce acute infections such as cellulitis or fasciitis. Slow
growing bacteria adapted to biofilm may fail to grow using standard culture techniques that maximize the cultivation of rapidly
proliferating free-living planktonic bacteria.2,11e14
According to the IDSA Guideline on Foot Infection in Diabetics,
acute infection should be diagnosed clinically on the basis of
purulent secretions (pus) or at least two of the cardinal manifestations of inflammation (redness, warmth, swelling or induration,
pain or tenderness). The AMDA pressure ulcer guideline states that
purulent drainage at the ulcer site alone may not require systemic
antibiotic therapy and respond to topical interventions.6 Wound
care specialists are interested in the role that “critical colonization”
or infection plays in delayed wound healing including: friability of
granulation tissue.7,15
Ulcerated lesions, especially stage 3-4, must be observed carefully over time following cleaning and/or debridement to detect the
cardinal manifestations of inflammation of recent onset (redness,
warmth, swelling or induration, pain or tenderness). The latter
criteria suggest a cellulitis that requires systemic antibiotic
therapy.2 Infection in stage 3-4 ulcers is usually polymicrobial and
may involve exposed deeper structures.16,17 The wound and
surrounding tissue should be carefully assessed for signs of severe
infection that could include easy dissection along the fascia by
a blunt instrument, severe constant pain, tissue necrosis/sloughing,
anesthesia, gas in the tissue/crepitation, or “woody” nonyielding
subcutaneous tissue.3
Pressure ulcers and undrained cutaneous abscesses may be the
source of polymicrobial MDRO bacteremia with a subtle afebrile
presentation in frail residents that includes functional decline.5,18e20
Bacteremia may include organisms such as Proteus, Escherichia coli,
Pseudomonas, S. aureus (MRSA), Streptococcus, and anaerobes.17,19e21
This report is focused on the management of mild infections treated
with systemic antibiotics in the nursing home and does not address
the management of severe infections in patients where tissue biopsy
is clearly indicated.
Sampling Options
Biopsy of viable tissue and/or aspiration of infected secretions
are the gold standard for the diagnosis of wound infection (an
infection of living tissue).2,3,5 However, when these samples are
obtained in acute cellulitis through intact skin, a pathogen may not
be isolated because the concentration of organisms is low.3,22,23
Causative organisms include gram-positive microorganisms
(mainly S. aureus, group A or B streptococci, viridans streptococci,
and Enterococcus) gram-negative bacilli (Enterobacteriaceae,
P. aeruginosa, acinetobacter sp.), and anaerobes. Unfortunately, few
clinicians are proficient and biopsy could cause pain and/or
bleeding, enlarge the wound, or introduce contaminants. A fullthickness punch biopsy may not be justified in the presence of
a small or superficial wound. Biopsy is relatively contraindicated in
the presence of arterial ulcers.24 Therefore, because of the invasiveness and limited number of qualified practitioners, swab
culture is the most frequently used method to determine the
resistance pattern of pathogens in acute wound infection.
Wound care nurse specialists perform conservative, sharp
instrumental wound debridement to remove loosely adherent,
clearly, identifiable devitalized/necrotic tissue with minimal pain
and bleeding. There should be a clear interface between the viable
P. Drinka et al. / JAMDA 13 (2012) 75e79
and nonviable tissue for nurses to remove the tissue. Nurse
specialists do not excise, biopsy, or place a needle into viable tissue.
Advanced practice nurses might perform additional activities that
could include punch biopsy or curettage of the wound base.25
However, only about 15% to 20% of wound care specialist nurses
are advanced practice nurses. Therefore, it is likely that on-site
availability of tissue biopsy, curettage, or aspiration of infected
material through intact skin will remain limited in nursing homes.
Although swab cultures are the most commonly performed type
of culture, they are controversial. If obtained from an uninfected
wound, they may lead to unnecessary antibiotic treatment. Cellulitis is an infection of living tissue. Specimens obtained from
material overlying the infected tissue or bone may or may not
reflect the infecting organisms. The swab may sample bacteria
colonizing superficial eschar, slough, or necrotic tissue rather than
the bacteria infecting the underlying living tissue or may fail to
isolate the underlying pathogen.25e27 On the other hand, careful
insertion of a swab following incision of a cutaneous abscess or
from a sinus tract with purulent drainage should produce a sample
with less potential surface contamination than swab culture of an
infected chronic wound.28 Swab specimens are not optimal/
suitable for culture of anaerobes and many fastidious organisms.24
Clinicians who use swab cultures must be aware of these potential
shortcomings.
The Levine Technique for Swab Cultures
The procedure used to obtain the swab is critical.7,24 Surface
organisms contaminate all wounds. Therefore, the wound should
be cleaned and irrigated (nonbacteriostatic saline) free of necrotic
material, eschar, purulence, or drainage prior to obtaining specimens. In some cases this will require sharp debridement. [Note:
Sharp debridement may be contraindicated in arterial ulcers.29]
The “interstitial”/tissue bioburden of pathogens might be approximated using the Levine technique, in which a 1-cm2 area of viable
tissue near the center of the viable wound base is sampled for
5 seconds with sufficient pressure to express fluid from within the
wound tissue for culture and gram stain.7 Proper technique is
important. Unfortunately, poor technique is often used. Invalid
results might be expected if the specimen consists of debris overlying the infected living tissue.
Swab Versus Tissue Biopsy or Curetage Culture of the Cleaned
or Debrided Acutely Infected Ulcer Base
We were able to identify only 2 studies that focused on acute
infection that compared specific organisms identified by swab
(following cleaning and/or debridement down to viable tissue)
versus biopsy or curettage specimens. The limited data are presented next. None of the reports were generated from an LTC
facility, and none included randomization of antibiotic therapy.
Pellizzer et al.30 cleaned and debrided the bases of 29 diabetic
foot ulcers with limb-threatening acute infection in patients who
had not received antibiotics for 3 weeks. Limb-threatening infection
was defined by the presence of full-thickness ulcer, cellulitis >2 cm,
bone or joint involvement, and systemic toxicity or serious
ischemia. Pellizzer et al. compared swab specimens to punch
biopsy specimens. The mean number of isolates per patient was
2.34 by swab and 2.07 by biopsy (NS). S. aureus was isolated in 10
specimens by swabbing and biopsy. The authors concluded “our
experience suggests that swabbing and biopsy of the ulcer base
may be equally reliable for the initial follow-up of empirical therapy
in limb-threatening diabetic foot infection, provided that laboratory processing is adequate.” The authors also concluded that tissue
77
biopsy was more reliable in wounds that were still active after
2 weeks of appropriate treatment.30
Lipski et al.25 studied 39 ulcers in diabetic patients who had not
received antibiotic therapy for 2 weeks. The ulcers were associated
with acute uncomplicated lower extremity SSTI. Approximately one
quarter were related to chronic ulcers. Standard bacteriology from
curettage specimens was compared to swab specimens. Results were
identical in 23. S. aureus was isolated in 54%. Compared to curettage,
there were missing isolates in 13 swab specimens. In approximately
6, the missing isolates included anaerobes (no attempt was made to
isolate anaerobes from swab specimens). In approximately 5, the
missing isolates included gram-negative rods, and in 3, they
included coagulase-negative staphylococci. Approximately 5 swab
specimens included “contaminants” not isolated from curettage. The
authors administered 2 weeks of antibiotic therapy directed against
aerobic gram-positive cocci. Clinical cure occurred in 75% with
improvement in an additional 16%. The authors concluded that
aerobic gram-positive cocci were usually the early tissue invaders in
uncomplicated previously untreated lower extremity SSTI.25
Current Guidelines Regarding Swab Culture
We reviewed current CPG regarding swab cultures and found
the following, sometimes-conflicting recommendations based on
expert opinion and limited data.
IDSA CPG for the diagnosis and treatment of diabetic foot
infections states the following: “Cleanse and debride the lesion
before obtaining specimens for culture. In cases involving an open
wound, obtain tissue specimens from the debrided base (whenever
possible) by means of curettage (scraping with a sterile dermal
curette or scalpel blade) or biopsy (bedside or operative)” [good
evidence based on a controlled trial]. “Avoid swabbing undebrided
ulcers or wound drainage. If swabbing the debrided wound base is
the only available culture option use a swab designed for culturing
aerobic and anaerobic organisms, and rapidly transport it to the
laboratory” [moderate evidence from a controlled trial].2
IDSA CPG for the evaluation of fever and infection in older adult
residents of LTC facilities states the following: “Surface swab
cultures are not indicated for the diagnosis of most bacterial SSTIs”
[good evidence from 1 or more well designed clinical trials, without
randomization; from cohort or case-controlled analytical studies
from multiple time-series; or from dramatic results from uncontrolled experiments]. “Needle aspiration (only skilled physicians
should perform this procedure) or deep-tissue biopsy to obtain
samples for Gram stain and culture may be appropriate in special
circumstances in which unusual pathogens are suspected, fluctuant
areas suggest an abscess is present, or initial antimicrobial treatment has been unsuccessful” [poor evidence and the opinion of
respected authorities].”5
Of interest, the ISDA CPGs cited above express different
conclusions regarding swab cultures, while the 2011 IDSA guideline
on the management of MRSA infection does not discuss the role of
swab versus tissue culture.4
According to the Wound, Ostomy and Continence Nurses Society
Guideline for Management of Wounds in Patients with LowerExtremity Arterial Disease, “Tissue biopsy is considered the gold
standard, to confirm the diagnosis of infection. Limited studies have
demonstrated that noninvasive, quantitative swab cultures are
a reasonable alternative to biopsies in general clinical practice
settings“ [consensus narrative review of several nonrandomized
trials of humans selected by a systematic method].31 The interested
reader is encouraged to consult the details of the review performed
by one of the co-authors (P.B.) that was the basis for this recommendation. The reviewer identified 19 nonrandomized studies in
which swab specimens were obtained from wounds of all types
78
P. Drinka et al. / JAMDA 13 (2012) 75e79
with or without acute infection. Swab specimens were processed
using quantitative and/or semiquantitative techniques.7 Quantitative technique may be more sensitive than standard semiquantitative technique.26,27 Some of the investigators used alginate
swabs because of the potential bacteriostatic effect of oxygenated
cotton.7
The Institute for Clinical Systems Improvement Pressure Ulcer
Prevention and Treatment’s health care protocol states: “Diagnosis
of wound infections is based on patient history and clinical findings. Although the gold standard for determining infection is tissue
biopsy, many wounds are swab cultured for confirmation of
infection. All wounds should be cleansed with a non-antiseptic
solution prior to culture. The swab culture should be placed on
healthy granulation tissue, pressed down and turned 360 degrees
to extract fluid. Do not culture pus, slough or necrotic tissue.
Infection must be treated with systemic antibiotics based on wound
culture results” [consensus statement, narrative review].15
According to the Registered Nurses’ Association of Ontario’s
Assessment and Management of Stage I to IV Pressure Ulcers, “To
obtain a wound culture, cleanse the wound with normal saline first.
Swab wound bed, not eschar, slough, exudate, or edges” [opinion of
respected authorities].32
Current Practice
We communicated with the author of a recent retrospective
report, “Empiric Outpatient Therapy with TrimethoprimSulfamethoxazole, Cephalexin, or Clindamycin for Cellulitis,” in
the American Journal of Medicine, who verified that the reported
bacteriology was based on swab culture.33 An article in the New
England Journal of Medicine, “MRSA Infections among Patients in the
Emergency Department,” stated that “Specimens were obtained
from the single largest area of infection with the use of sterile
Dacron swabs.”34 Swab culture seems to be the “de facto” standard
of care in publications focused on SSTI in out patients. These studies
did not focus on chronic wounds, which may develop a more
complex flora.2 Finally, Jenkins et al. reported, “Skin and soft tissue
infections requiring hospitalization at an academic medical center”
in Clinical Infectious Disease from the University of Colorado. Deep
tissue samples and material from abscess cavities were cultured.
The authors stated, “Needle aspirates or punch biopsies are not
routinely performed at our institution.”18 Perhaps it is unrealistic to
expect nursing home personnel to use biopsy or needle aspiration
to determine that a mild skin infection is caused by MRSA, if these
techniques are not routinely used in hospitalized patients at an
academic medical center.
Antibiotic Therapy
Most literature on systemic antibiotic treatment of skin infection focuses on outpatients or serious infection in hospitalized
patients. Clinicians are left to adapt/project these recommendations to the management of mild infections treated in the nursing
home.
The 2011 IDSA guideline for the management of MRSA infections
provides guidance for the management of SSTI in outpatients. The
recommendations may be applicable to mild infections treated in
the nursing facility. For outpatients with purulent cellulitis, therapy
for MRSA is recommended pending culture results. If coverage for
both beta-hemolytic streptococci and MRSA is desired, options
include trimethoprim-sulfamethoxazole (TMP-SMX) or a tetracycline in combination with a beta-lactam (e.g., amoxicillin). The
activity of TMP-SMX or a tetracycline against beta-hemolytic
streptococci is “not well defined”; beta-hemolytic streptococci
may also be resistant to erythromycin.3,4 Oral antibiotic choices
(TMP/SMX, minocycline) are considered to be less reliable for
methicillin-sensitive S. aureus (MSSA) than the oral agent of choice,
dicloxicillin.3,4 According to the IDSA SSTI guideline, the efficacy of
doxycyline/minocycline for MSSA includes “limited recent clinical
experience,” while that of TMP-SMX is “poorly documented.”3
A 1992 publication, “TMP-SMX Compared with Vancomycin for
the Treatment of S. aureus Infection,” found that TMP-SMX failure in
serious infections occurred mostly in patients with MSSA.35 It is
optimal to determine if a skin infection is caused by MRSA versus
MSSA; beta-lactams are the drug of choice for MSSA.3
If oral therapy is elected for more severe SSTI, linazolid is
considered to be the drug of choice. For hospitalized patients with
complicated SSTI (defined as patients with deeper soft-tissue
infections surgical/traumatic wound infection, major abscesses,
cellulitis, and infected ulcers and burns), in addition to surgical
debridement and broad-spectrum antibiotics, empirical therapy for
MRSA should be considered pending culture data.4
The IDSA Guideline for Diabetic Foot Infections presents a typical
(but not invariable) scenario for the progression of acute infection.
Management of diabetic foot infections involves determining the
severity of infection as the basis for selecting appropriate treatment. Mild acute superficial cellulitis can probably be treated with
agents that only (or predominantly) cover aerobic gram-positive
cocci, S. aureus and beta-hemolytic streptococci (groups A, C, and
G, but especially group B), in patients who have not recently
received antimicrobials while carefully monitoring the response. In
the case of chronic infections of moderate severity, it is safest to
commence therapy with agents active against gram positive, gram
negative, and anaerobic organisms while awaiting culture results.
P. aeruginosa should be suspected in an ulcer macerated because of
soaking and anaerobes should be suspected if the ulcer is
malodorous. The guideline also states: “The pathogenic role of each
isolate in a polymicrobial infection is often unclear. . It is not
always necessary to cover all microorganisms isolated from
cultures. More virulent species (e.g., S. aureus and group A or B
streptococci) should always be covered, but in a polymicrobial
infection, less-virulent bacteria (e.g., coagulase-negative staphylococci and enterococci) may be less important. However, if the
infection has not responded to the empirical regimen, select agents
with activity against all isolates.” Infection in pressure ulcers is
usually polymicrobial and may involve exposed deeper
structures.17
Conclusion
Tissue biopsy is the gold standard for the culture of wound
tissue infection. Scraping the cleaned/debrided wound base with
a dermal curette or scalpel blade is an alternative. Attempted
aspiration of abscess, bullae, or an area of cellulitis is also optimal.2
These techniques are less likely to collect surface contaminants
than is swab collection from the base of a chronic wound and are
especially important in serious infection, systemic toxicity, or
failure of initial therapy. Nursing home practitioners should
become proficient with these techniques or develop systems that
provide rapid consultation. Until then, swab culture will be used to
determine the resistance pattern of wound pathogens treated in
nursing homes and emergency departments.
Whenever possible, systemic antibiotic therapy should be
preceded by culture, especially in settings in which MDROs are
endemic. Surface organisms contaminate all wounds. Therefore, if
the wound is acutely infected and a swab culture is ordered, the
wound should be cleaned and irrigated prior to obtaining a specimen from the viable wound bed using the Levine technique.7 If the
wound requires debridement to produce a clean wound bed,
referral to a qualified practitioner should be expedited.36 In many
P. Drinka et al. / JAMDA 13 (2012) 75e79
circumstances, debridement/drainage may be more important than
antibiotic therapy. The goal is to physically excise dead and
unhealthy tissue and to drain abscesses, thereby enabling wound
healing by removing a reservoir of potential pathogens.2 Availability of practitioners capable of performing sharp debridement
will also facilitate the collection of specimens following removal of
overlying devitalized tissue.
Swab cultures should not be used to determine IF the wound is
acutely infected; rather, their role may be to identify potential
pathogens in a wound judged to be infected based on clinical
criteria. Practitioners who utilize swab cultures to guide antibiotic
selection for mild infections treated in the nursing home should
ensure proper collection technique and be aware that the results
may indicate colonization rather than infection (a risk factor for
MDRO infection). False-negative results are also a possibility.25,30,31
Antibiotic treatment should be viewed as a therapeutic trial that
includes monitoring for deterioration and/or bacteremia. MDRO
isolation should heighten the clinician’s level of concern if the
prescribed antibiotic did not “cover” the MDRO or other potential
pathogen. Deterioration or failure to respond could be related to
inadequate debridement of necrotic tissue or abscess, ischemia,
inadequate antibiotic penetration, or failure to “cover” the infecting
pathogens. We are writing to ask clinicians to consider use of the
Levine technique to collect specimens from clinically infected
wounds treated in the nursing home, if more invasive sampling is
not available or elected. The relative value of “Levine” swab culture
versus empiric systemic antibiotic choice on the outcome of mild
acute wound infection treated in the nursing home is unknown
since neither approach has been tested. The data are meager.
Controlled trials are needed. Until then, the issue will remain
a “Clinical Controversy.”
Acknowledgments
We would like to thank Benjamin Lipsky for patiently
responding to our questions during preparation of the manuscript.
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