Antibiotics for Abscess

Case Presentation:

40-year-old presenting with cellulitis and abscess. There is a 3-cm fluctuant nodule on the dorsum of his left forearm. Ultrasound shows cobblestoning with a 3x2x2 cm fluid collection below the dermis.

Clinical Question: Should antibiotics be used in the treatment of simple cutaneous abscess?

Background:

Abscesses are an extremely common complaint in the ED. Four out of 100 people in the US seek medical attention each year for skin infections.1 There are clear IDSA guidelines on the management of these abscess and extensive literature supporting these guidelines.2 One recommendation is that mild abscesses should be treated with incision and drainage (I&D) without antibiotics. The level of evidence is described as “strong,” citing RCTs dating back to 1970. Based on my experience in the ED, this recommendation has been largely ignored, and I became curious why.

Current IDSA Guidelines:

Systemic antibiotics for I&D does not improve cure rates.3–7 Even in abscesses due to MRSA, antibiotics are not shown to improve cures, but they may have a modest effect on recurrence3,7 However, antibiotics should be considered in the treatment of abscesses for patients with signs of systemic infection, multiple abscesses, extremes of age, or severely impaired host defenses.

Current evidence:

In the last three years, there have been three large randomized controlled trials (RCTs) on the use of antibiotics as an adjunct for abscess treatment in the ED. Two RCTs (n=1247 and 524) showed that clindamycin and TMP-SMX improve clinical cure rates.8,9 One study looked specifically at abscesses less than 5 cm, the other looked at abscesses greater than 2 cm. However, TMP-SMX and clindamycin were both associated with more GI side effects when compared to placebo. A third RCT showed no significant difference in clinical cure rate with clindamycin vs TMP-SMX for treatment of skin abscesses 5 cm or larger.10

• Three of the five RCTs cited by the IDSA in support of not using antibiotics are no longer applicable to the US population. These studies were done published before 1990,4,6,11 when community-acquired MRSA was virtually non-existent.12 MRSA now causes 63% of abscesses in the US.13

• Only two RCTs cited by the IDSA assessed TMP-SMX during the MRSA era.3,7 These studies have small sample sizes (212 and 161). They detected trends, but did not demonstrate that antibiotics significantly improve cure rates. This may be due to type II error, rather than a true negative finding.

• Since 2014, the evidence shows the use of TMP-SMX or clindamycin as an adjunct to I&D for simple cutaneous abscesses improves cure rates among healthy immunocompetent patients in the ED setting.

The IDSA does advocate for the use of antibiotics in several populations without citing evidence. This includes patients with signs of systemic illness, severely immunocompromised, multiple abscesses, extremes of age, and lack of response to incision and drainage alone.

These populations were largely excluded from both the original RCTs cited by the IDSA as well as the new publications cited here.

Although these populations were not studied in these RCTs, it is reasonable to treat patients in these circumstances with systemic antibiotics given they are higher risk for complications and adverse outcomes.

Recommendations:

• Antibiotics should be strongly considered as an adjunct to I&D for simple cutaneous abscesses, even among healthy patients

• The benefit needs to be weighed against the risk associated with antibiotics including GI side effects and more rare effects such as clostridium difficile.

• Be cognizant of contraindications such as hypersensitivity, pregnancy/breastfeeding, etc.14 Be aware of antibiotic resistance patterns in the local community.

• Simple cutaneous abscesses are defined as purulent skin infections that can be safely managed in the ED and outpatientsettings . Be sure to rule out infections that do not meet this criterion:

• Specific anatomic locations (genital, perirectal, etc)

• Deeper infection (necrotizing fasciitis, osteomyelitis, etc)

• Systemically ill patient (meets SIRS criteria)

• Treatment for the patient in the vignette above:

• Perform I&D

• Discharge home with 10-day course of clindamycin (given MRSA has active resistance to TMP-SMX in our local population).

• Follow up with primary care doctor in 10 days

References:

1. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e | AccessMedicine | McGraw-Hill Medical. Available at: https://accessmedicine.mhmedical.com/book.aspx?bookID=1658. (Accessed: 14th September 2017)

2. Stevens, D. L. et al. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Clin. Infect. Dis. 59, e10–e52 (2014).

3. Duong, M., Markwell, S., Peter, J. & Barenkamp, S. Randomized, controlled trial of antibiotics in the management of community-acquired skin abscesses in the pediatric patient. Ann. Emerg. Med. 55, 401–407 (2010).

4. Macfie, J. & Harvey, J. The treatment of acute superficial abscesses: A prospective clinical trial. Br. J. Surg. 64, 264–266 (1977).

5. Llera, J. L. & Levy, R. C. Treatment of cutaneous abscess: a double-blind clinical study. Ann. Emerg. Med. 14, 15–19 (1985).

6. Rutherford, W. H., Calderwood, J. W., Hart, D. & Merrett, J. D. ANTIBIOTICS IN SURGICAL TREATMENT OF SEPTIC LESIONS. The Lancet 295, 1077–1080 (1970).

7. Schmitz, G. R. et al. Randomized Controlled Trial of Trimethoprim-Sulfamethoxazole for Uncomplicated Skin Abscesses in Patients at Risk for Community-Associated Methicillin-Resistant Staphylococcus aureus Infection. Ann. Emerg. Med. 56, 283–287 (2010).

8. Talan, D. A. et al. Trimethoprim–Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess. N. Engl. J. Med. 374, 823–832 (2016).

9. Daum, R. S. et al. A Placebo-Controlled Trial of Antibiotics for Smaller Skin Abscesses. N. Engl. J. Med. 376, 2545–2555 (2017).

10. Miller, L. G. et al. Clindamycin versus Trimethoprim–Sulfamethoxazole for Uncomplicated Skin Infections. N. Engl. J. Med. 372, 1093–1103 (2015).

11. Llera, J. L. & Levy, R. C. Treatment of cutaneous abscess: A double-blind clinical study. Ann. Emerg. Med. 14, 15–19 (1985).

12. David, M. Z. & Daum, R. S. Community-Associated Methicillin-Resistant Staphylococcus aureus: Epidemiology and Clinical Consequences of an Emerging Epidemic. Clin. Microbiol. Rev. 23, 616–687 (2010).

13. Emerging Infections Program Network Report Methicillin-Resistant Staphylococcus aureus. (CDC, 2015).

14. Merck Manual. (2017).