Should wound cultures for a groin abscess be both aerobic and anaerobic?

From the Guidelines

Yes, wound cultures for a groin abscess should include both aerobic and anaerobic cultures. Groin abscesses typically contain a polymicrobial mixture of organisms, including both aerobic bacteria (such as Staphylococcus aureus, Streptococcus species, and gram-negative enteric organisms) and anaerobic bacteria (like Bacteroides, Peptostreptococcus, and other anaerobes) [ 1 ]. The proximity of the groin to the perineum and gastrointestinal tract increases the likelihood of anaerobic involvement. When collecting cultures, the specimen should be obtained after cleaning the area but before antibiotics are administered, ideally by aspiration or during incision and drainage to avoid contamination [ 1 ].

Key Considerations

• The culture results guide targeted antibiotic therapy, which is typically initiated empirically with broad-spectrum coverage (such as amoxicillin-clavulanate, piperacillin-tazobactam, or a combination of clindamycin plus a fluoroquinolone) and then narrowed based on culture results [ 1 ].
• Proper specimen collection and transport are crucial for accurate results, with anaerobic specimens requiring special transport media and prompt delivery to the laboratory to maintain viability of oxygen-sensitive organisms [ 1 ].
• The 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections recommends obtaining an appropriate specimen for culture from almost all infected wounds, including aerobic and anaerobic culture [ 1 ].

Clinical Implications

• Aerobic and anaerobic cultures are essential for guiding targeted antibiotic therapy and ensuring the best possible outcomes for patients with groin abscesses.
• Clinicians should prioritize proper specimen collection and transport to ensure accurate culture results.
• Empiric broad-spectrum antibiotic therapy should be initiated in cases of complex abscesses, with coverage of Gram-positive, Gram-negative, and anaerobic bacteria [ 1 ].

From the Research

Wound Culture for Groin Abscess

To determine whether wound cultures for a groin abscess should be both aerobic and anaerobic, consider the following points:

• Anaerobic bacteria are a common cause of endogenous infections, and anaerobic infections are generally polymicrobial, involving both anaerobes and aerobes 2.
• The isolation of anaerobes requires appropriate methods of collection, transportation, and cultivation of specimens, and the lack of use of these methods can lead to inadequate recovery of anaerobes and inappropriate therapy 2.
• Most anaerobic infections are polymicrobial, and diagnosis is often made on the basis of clinical clues, with knowledge of common sites, predisposing conditions, and representative features of anaerobic infections being critical 3.
• Appropriate coverage for aerobic bacteria must be included in the treatment regimen, as anaerobic infections often involve mixed flora 3.

Microbiologic Characteristics of Wounds and Abscesses

The aerobic and anaerobic microbiologic characteristics of wounds and cutaneous abscesses have been studied, with the following findings:

• In wounds, aerobic or facultative bacteria only were present in 38% of specimens, anaerobes only in 30%, and mixed flora in 32% 4.
• In abscesses, aerobic or facultative bacteria were recovered in 26% of specimens, anaerobes only in 36%, and mixed flora in 38% 4.
• The highest rates of anaerobes in wounds were in the inguinal, buttocks, and trunk areas, and in abscesses in the perirectal, external genitalia, neck, and inguinal areas 4.

Management of Groin Infections

The management of early (<30 day) vascular groin infections using vacuum-assisted closure alone without muscle flap coverage has been reported, with the following results:

• All patients had positive wound cultures and received culture-directed antibiotic therapy for 47 +/- 45 days (range, 14-180 days) 5.
• Length of stay was significantly more in Szilagyi III, whereas mean VAC use and time-to-healing were similar 5.
• Mean follow-up was 33.4 +/- 19.5 months (range, 2-72 months), with all wounds healing (mean, 49 +/- 21 days) 5.

Key Points to Consider

When culturing the drainage of a groin abscess, consider the following key points:

• Both aerobic and anaerobic cultures should be performed to ensure adequate coverage of potential pathogens 2, 3.
• The polymicrobial nature of wounds and cutaneous abscesses highlights the importance of considering both aerobic and anaerobic bacteria in the treatment regimen 4.
• Culture-directed antibiotic therapy is crucial in the management of groin infections, with the duration of therapy ranging from 14 to 180 days 5.