From the Guidelines
For cat scratch cellulitis in a patient allergic to Zosyn, azithromycin is the recommended antibiotic option, given its efficacy in reducing lymph node size and alleviating symptoms, as demonstrated in a double-blind placebo-controlled study 1. The treatment regimen for azithromycin is 500 mg on day 1, followed by 250 mg once daily for 4 additional days for patients weighing ≥45.5 kg (100 lb), and 10 mg/kg orally on day 1, then 5 mg/kg on days 2–5 for those weighing <45.5 kg 1. Other alternatives, such as doxycycline (100 mg twice daily for 7-14 days) or trimethoprim-sulfamethoxazole (one double-strength tablet twice daily for 7-14 days), may also be considered, as suggested by guidelines for managing infections caused by Bartonella henselae 1. Key considerations in selecting an antibiotic include the severity of the infection, patient factors, and local resistance patterns. It is essential to monitor the patient's response to treatment and adjust the duration of therapy accordingly, with most uncomplicated cases resolving within 7-14 days of appropriate treatment. Additionally, proper wound care, including thorough cleaning, and monitoring for signs of worsening infection, such as increasing redness, swelling, or fever, are crucial components of managing cat scratch cellulitis. The choice of antibiotic should prioritize those with demonstrated efficacy against Bartonella henselae, the primary causative agent of cat scratch disease, as supported by the Infectious Diseases Society of America guidelines 1.
From the Research
Antibiotic Options for Cat Scratch Cellulitis
In a patient allergic to Zosyn (piperacillin-tazobactam), the following antibiotics can be considered for the treatment of cat scratch cellulitis:
- Azithromycin: This antibiotic has been shown to be effective in treating cat scratch disease, with one study demonstrating more rapid diminution in size of infected lymph nodes 2, 3, 4.
- Trimethoprim/sulfamethoxazole (TMP/SMX): This antibiotic combination has been found to be effective in treating cat scratch disease, with comparable effectiveness to azithromycin 4.
- Clarithromycin: This antibiotic has been shown to be effective against Bartonella henselae, the causative agent of cat scratch disease 2.
- Ciprofloxacin: This antibiotic has been found to be effective against Bartonella henselae, although its use may be limited due to potential side effects 2.
- Gentamicin: This antibiotic has been shown to be effective against Bartonella henselae, although its use may be limited due to potential side effects 2.
- Doxycycline: This antibiotic has been found to be effective in treating cat scratch disease, particularly in severe or persistent cases 5.
- Erythromycin: This antibiotic has been found to be effective in treating cat scratch disease, particularly in severe or persistent cases 5.
Considerations for Antibiotic Choice
When choosing an antibiotic for the treatment of cat scratch cellulitis, it is essential to consider the patient's allergy history and potential interactions with other medications. Additionally, the severity and presentation of the disease should be taken into account, as well as the potential for complications such as osteomyelitis or encephalopathy 2, 5, 3, 4.
Alternative Pathogens
It is also important to consider alternative pathogens that may be responsible for the patient's symptoms, such as Pasteurella multocida, which is a common cause of infection following cat bites or scratches 6. In such cases, penicillin may be an appropriate treatment option.