From the Guidelines
For a possibly infected spider bite, the recommended antibiotic is typically amoxicillin-clavulanate, given its broad-spectrum coverage against common skin infection pathogens, including Staphylococcus aureus, Streptococcus species, and Pasteurella multocida, as suggested by the Infectious Diseases Society of America guidelines 1. The choice of antibiotic should be based on the severity of the infection, patient allergies, and local resistance patterns.
- Amoxicillin-clavulanate 875/125 mg orally twice daily is a common adult regimen for 7-10 days, as it provides coverage against a wide range of bacteria, including those that may be resistant to other antibiotics 1.
- For patients with penicillin allergies, alternative options such as doxycycline 100 mg orally twice daily or a fluoroquinolone (e.g., ciprofloxacin or levofloxacin) plus metronidazole may be considered, as they also provide broad-spectrum coverage against common skin infection pathogens 1. In addition to antibiotics, wound care is essential, including cleaning the area with soap and water, applying an antibiotic ointment, and covering with a clean bandage.
- Elevating the affected area, if possible, and using cold compresses can help reduce swelling and promote healing. Medical attention should be sought immediately if there are signs of severe infection, such as increasing redness, warmth, swelling, pus, or red streaks extending from the bite, or if the bite is from a known dangerous spider like a black widow or brown recluse.
From the Research
Antibiotic Treatment for Possible Spider Bite
- The recommended antibiotic treatment for a possible spider bite with signs of infection is not explicitly stated in the provided studies, but some studies suggest the use of antibiotics with activity against MRSA, such as trimethoprim-sulfamethoxazole 2.
- A study published in 2003 found that all isolated organisms from spider bite infections were sensitive to trimethoprim-sulfamethoxazole, and the authors recommend the empiric use of antibiotics with activity against MRSA 2.
- Another study published in 2002 found that secondary infection occurred in only 0.9% of spider bite cases, and there were no cases of necrotic ulcers or allergic reactions 3.
- A review of the treatment of community-acquired respiratory tract infections published in 2004 discusses the use of amoxicillin/clavulanate (Augmentin) as a broad-spectrum antibacterial agent, but does not specifically address spider bite infections 4.
- A study published in 1987 on the diagnosis and treatment of brown recluse spider bites used erythromycin as a treatment, but the effectiveness of this treatment is not clearly established 5.
Considerations for Antibiotic Treatment
- The choice of antibiotic treatment for a possible spider bite with signs of infection should be guided by the results of culture and sensitivity testing, if available 2.
- The use of antibiotics with activity against MRSA, such as trimethoprim-sulfamethoxazole, may be warranted in cases where MRSA is suspected or confirmed 2.
- It is essential to note that the majority of spider bites do not result in significant infections, and the use of antibiotics should be judicious and based on clinical judgment 3, 6.