What antibiotics are recommended for cellulitis (infection of the skin and subcutaneous tissues) above the knee following a scratch injury in a pig barn environment?

From the Guidelines

For cellulitis over the knee after a scratch in a pig barn, the recommended first-line antibiotic treatment is amoxicillin-clavulanate (Augmentin) 875/125 mg taken orally twice daily for 5-7 days, as suggested by the most recent guidelines 1. This recommendation is based on the likely bacteria from both the skin and the agricultural environment, including Staphylococcus, Streptococcus, and potentially zoonotic pathogens from pigs. Some key points to consider:

• The scratch in a pig barn raises concerns about exposure to bacteria like Streptococcus suis or other farm-associated organisms that require broader coverage than typical skin infections.
• It's essential to clean the wound thoroughly with soap and water, apply topical antibiotic ointment, keep the area covered with a clean bandage, elevate the leg when possible, and seek medical attention promptly.
• If you develop fever, increasing redness, warmth, swelling, red streaking from the wound, or the infection doesn't improve within 48 hours of starting antibiotics, you should seek immediate medical care as intravenous antibiotics may be necessary. Alternatives to amoxicillin-clavulanate include cephalexin 500 mg four times daily or clindamycin 300-450 mg three times daily for the same duration if you have a penicillin allergy, as supported by previous guidelines 1. However, the most recent and highest quality studies 1 prioritize amoxicillin-clavulanate as the first-line treatment. In cases where there are signs of systemic infection or severe disease, broader-spectrum antibiotics such as vancomycin or linezolid may be considered, as recommended by the guidelines 1. It is crucial to follow the recommended treatment duration and to seek medical attention if the infection does not improve or worsens, to prevent complications and ensure the best possible outcome.

From the FDA Drug Label

The cure rates in clinically evaluable patients with complicated skin and skin structure infections were 90% in linezolid-treated patients and 85% in oxacillin-treated patients The cure rates by pathogen for microbiologically evaluable patients are presented in Table 18. Table 18 Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Complicated Skin and Skin Structure Infections PathogenCured ZYVOXn/N (%)Oxacillin/Dicloxacillinn/N (%) Staphylococcus aureus73/83 (88)72/84 (86) Methicillin-resistant S aureus2/3 (67)0/0 (-) Streptococcus agalactiae6/6 (100)3/6 (50) Streptococcus pyogenes18/26 (69)21/28 (75)

Antibiotics for Cellulitis

• The most relevant information for treating cellulitis comes from the study of complicated skin and skin structure infections.
• Linezolid and oxacillin are two antibiotics that have been studied for the treatment of complicated skin and skin structure infections.
• The cure rates for linezolid and oxacillin are 90% and 85%, respectively.
• The cure rates for specific pathogens, such as Staphylococcus aureus and Streptococcus pyogenes, are also provided.
• Tedizolid is another antibiotic that has been studied for the treatment of acute bacterial skin and skin structure infections (ABSSSI).
• The clinical success rates for tedizolid and linezolid are similar, with tedizolid showing a clinical success rate of 88.5% and linezolid showing a clinical success rate of 88.6% 2 3.

From the Research

Antibiotic Treatment for Cellulitis

• The treatment of cellulitis, particularly when acquired in a setting like a pig barn after a scratch, involves considering the potential causative pathogens and their antibiotic resistance patterns 4, 5, 6, 7, 8.
• Studies have shown that community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a common cause of skin and soft tissue infections, including cellulitis 4, 6, 8.
• The choice of antibiotic should be guided by the severity of the infection, patient history, and risk factors, as well as the likelihood of CA-MRSA involvement 5, 7.
• Trimethoprim-sulfamethoxazole and clindamycin are often recommended for empiric treatment of cellulitis in areas with high prevalence of CA-MRSA due to their activity against this pathogen 6, 8.
• Cephalexin, while commonly used, may not be as effective against CA-MRSA, highlighting the importance of considering local resistance patterns and the specific circumstances of the infection 4, 5.

Considerations for Cellulitis Over the Knee

• The management of cellulitis over the knee after a scratch in a pig barn should take into account the potential for exposure to bacteria that may be resistant to common antibiotics 8.
• Given the risk of CA-MRSA, antibiotics with activity against this pathogen, such as trimethoprim-sulfamethoxazole or clindamycin, may be preferred for empiric treatment 6, 8.
• It is crucial to assess the severity of the cellulitis and the patient's overall health status to determine the most appropriate antibiotic regimen and whether hospitalization is necessary 7.

Importance of Antibiotic Selection

• The selection of an appropriate antibiotic is critical to ensure effective treatment of cellulitis and to minimize the risk of treatment failure or the development of antibiotic resistance 4, 5, 6, 8.
• Antibiotics should be chosen based on their efficacy against the most likely causative pathogens, considering factors such as the patient's history, the severity of the infection, and local antibiotic resistance patterns 7.