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Adjunctive antibiotic therapy improves cure rates for simple skin abscesses
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Another study has shown the clinical benefit of adding antibiotic therapy to incision and drainage treatment for uncomplicated skin abscesses.
In the study, published today in The New England Journal of Medicine, Robert S. Daum, MD, professor of pediatrics at the University of Chicago Medicine, and colleagues demonstrate that clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) in conjunction with incision and drainage improves short-term outcomes in patients with simple abscess, particularly those caused by Staphylococcus aureus.
Daum and colleagues said their results complement a study published last year showing that patients with uncomplicated skin abscesses who were assigned TMP-SMX had higher cure rates than those given placebo. Unlike that study, Daum and colleagues included children aged 12 years or younger.
“The cumulative data from our investigation and that of Talan et al. call into question the perception — largely based on expert opinion or smaller, underpowered, and lower quality noninferiority trials — that cure rates do not improve with the addition of systemic antibiotic treatment after incision and drainage,” Daum and colleagues wrote. “These two larger trials show that adjunctive antibiotic therapy improves cure rates for skin abscesses and decreases the recurrence rate.”
Between May 2009 and January 2015, Daum and colleagues recruited outpatients from urgent care clinics, emergency departments and affiliated clinics at six sites in Atlanta, Chicago, Los Angeles, Nashville, San Francisco and St. Louis. Patients had to have a single abscess no larger than 5 cm in diameter, except for children aged 1 to 8 years, who were eligible if their abscesses were 4 cm or smaller, and infants aged 6 to 11 months, whose abscesses could be no larger than 3 cm. Participants were randomly assigned oral clindamycin, TMP-SMX or placebo after abscess incision and drainage.
Among the 786 patients enrolled in the study, 505 were adults and 281 were children. The mean age at enrollment was 25.5 years and 57% of the participants were male. In the intention-to-treat population, the clinical cure rate among patients who received clindamycin (n = 266) was 83.1% compared with 81.7% in patients who received TMP-SMX (n = 263) and 68.9% in the placebo group (n = 257).
“The results were similar for the population that could be evaluated, with significantly different cure rates for placebo versus either antibiotic but no significant difference between clindamycin and TMP-SMX,” Daum and colleagues wrote.
Among their other findings, Daum and colleagues found:
- children who received clindamycin had a significantly higher cure rate than those in the TMP-SMX or placebo groups in the population that could be evaluated — an advantage that was significantly greater than as seen among the adult population;
- no significant difference in cure rates between adults and children when the TMP-SMX and placebo groups were compared (P = 0.87);
- no significant differences between children and adults in any comparison among the intention-to-treat groups.
According to the results, cure rates were significantly higher for the clindamycin (83.5%) and TMP-SMX (83.2%) groups than for the placebo group (63.8%) in the intention-to-treat population of patients who were culture-positive for S. aureus. Similarly, significantly lower cure rates were seen in the placebo group compared with patients who received either antibiotic for treatment of MRSA. In patients infected with MRSA, the cure rate in the placebo group was significantly lower than in patients who received clindamycin but not significantly lower than in the TMP-SMX group, Daum and colleagues said.
After 1 month, new infections were less common in the 221 patients in the clindamycin group (6.8%) than in 215 patients in the TMP-SMX group (13.5%) or 177 in the placebo group (12.4%). Adverse events were more frequent with clindamycin than with TMP-SMX or placebo, Daum and colleagues reported.
“Although no cases of C. difficile-associated diarrhea or severe allergic reactions were observed, these and other known side effects must be considered,” they wrote. “Our findings suggest that there is a trade off between more adverse effects and a lower likelihood of infection recurrence when one uses clindamycin rather than TMP-SMX. Such information and the local prevalence of resistance should be used by treating physicians and policymakers when choosing an antibiotic for adjunctive therapy of cutaneous abscesses.” – by Gerard Gallagher
Reference:
Daum RS, et al. N Engl J Med. 2017;doi:10.1056/NEJMoa1607033.
Disclosure: Please see the full study for a list of all authors’ relevant financial disclosures.
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Michael S. Calderwood, MD, MPH, FIDSA
The findings published in the study by Daum and colleagues complement those published previously by Talan and colleagues, as well as prior findings by Miller and colleagues. These studies help put to rest the debate about the benefit of adjunctive systemic antibiotic treatment following incision and drainage of a skin abscess, with all three of these papers being published after the release of the most recent guidelines from the Infectious Diseases Society of America. This is important because the IDSA guidelines state the following: “The addition of systemic antibiotics to incision and drainage of cutaneous abscesses does not improve cure rates.” It is important to note, though, that two of the studies referenced by the IDSA guidelines did actually show 13.5% to 19% higher rates of new lesions at 10 to 30 days following placebo vs. antibiotic.
In the study by Daum and colleagues, the authors present the findings of a 7-year, six-site prospective, randomized, double-blind, placebo-controlled clinical trial focused on both children and adults presenting with small skin abscesses (≤3 cm in ages 3 to 11 months, ≤4cm in age 1 to 8 years, and ≤5 cm in those older than aged 8 years). There were more than 250 patients in each of the three arms (1:1:1 ratio):
- incision and drainage followed by placebo (N = 257);
- incision and drainage followed by trimethoprim-sulfamethoxazole (TMP-SMX) two single-strength tablets (equivalent to one double-strength tablet) twice per day for 10 days (N = 263);
- incision and drainage followed by clindamycin two 150-mg tablets (equivalent to one 300-mg tablet) three times per day for 10 days (N = 266).
Not surprisingly, given the focus on skin abscess rather than cellulitis, about two-thirds of the cases were confirmed by culture to be secondary to Staphylococcus aureus (49% MRSA, 18% methicillin-susceptible S. aureus).
In the intention-to-treat analysis comparing results at the test of cure visit 7 to 10 days after completion of the antibiotic (or placebo), 68.9% of participants in the placebo arm, 81.7% of participants in the TMP-SXT arm, and 83.1% of participants in the clindamycin arm were deemed cured.
Of additional interest is the finding that children had a significantly higher cure rate with clindamycin compared with TMP-SMX in the population that could be evaluated. This difference was not seen in adults.
It is important to note, though, that this study population had only 2.3% clindamycin resistance in the S. aureus isolates (0% TMP-SMX resistance). In thinking about the generalizability of the clindamycin finding to one’s own practice, it is important to look at local resistance rates because the incidence of clindamycin-resistant S. aureus has been on the rise. Daum and colleagues also found a higher rate of adverse events in the clindamycin arm than in the TMP-SMX arm, although all resolved without sequelae.
Overall, this is an important study that adds to the literature suggesting that a course of an oral antibiotic following incision and drainage of a skin abscess, even a small skin abscess, can increase the probability of clinical cure in both adult and pediatric patients. Future guidelines will need to reflect these data.
References:
Duong M, et al. Ann Emerg Med. 2008;doi:10.1016/j.annemergmed.2009.03.014.
Miller LG, et al. N Engl J Med. 2015;doi:10.1056/NEJMoa1403789.
Schmitz GR, et al. Ann Emerg Med. 2010;doi:10.1016/j.annemergmed.2010.03.002.
Stein M, et al. Int J Infect Dis. 2016;doi:10.1016/j.ijid.2016.02.016.
Stevens DL, et al. Clin Infect Dis. 2014;doi:10.1093/cid/ciu296.
Sutter DE, et al. Pediatrics. 2016;doi:10.1542/peds.2015-3099.
Talan DA, et al. N Engl J Med. 2016;doi:10.1056/NEJMoa1507476.
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