What antibiotic covers cellulitis and Proteus mirabilis in a patient with a penicillin (Penicillin) allergy?

From the Guidelines

For a patient with a penicillin allergy who has cellulitis caused by Proteus mirabilis, I recommend using a fluoroquinolone such as ciprofloxacin (500-750 mg orally twice daily for 7-14 days) or levofloxacin (750 mg orally once daily for 7-14 days) as the first-line treatment. Alternatively, trimethoprim-sulfamethoxazole (TMP-SMX, 1-2 double-strength tablets twice daily for 7-14 days) can be effective. For more severe infections requiring intravenous therapy, consider aztreonam (1-2 g IV every 8-12 hours) or a carbapenem like ertapenem (1 g IV once daily), as these typically don't cross-react with penicillin allergies 1. The duration of treatment depends on clinical response, with most uncomplicated cases resolving within 7-10 days. These antibiotics are recommended because Proteus mirabilis is naturally resistant to tetracyclines and often resistant to first-generation cephalosporins. Fluoroquinolones and TMP-SMX provide good coverage against both typical skin pathogens and gram-negative organisms like Proteus. Some key points to consider when selecting therapy include:

• Assessing the severity of infection
• Considering local resistance patterns
• Avoiding cephalosporins in patients with severe penicillin allergies (anaphylaxis) due to potential cross-reactivity, although the risk is lower than historically reported 1
• Using a fluoroquinolone or TMP-SMX as a first-line treatment for uncomplicated cases
• Reserving intravenous therapy with aztreonam or a carbapenem for more severe infections. It's also important to note that the diagnosis and management of skin and soft tissue infections, including cellulitis, should be guided by the most recent and highest quality evidence, such as the 2014 update by the Infectious Diseases Society of America 1.

From the FDA Drug Label

Levofloxacin has in vitro activity against Gram-negative and Gram-positive bacteria fections as described in Indications and Usage (1): Gram-PositiveBacteria Enterococcus faecalis Staphylococcus aureus (methicillin-susceptible isolates) Staphylococcus epidermidis (methicillin-susceptible isolates) Staphylococcus saprophyticus Streptococcus pneumoniae (including multi-drug resistant isolates [MDRSP] )1 Streptococcus pyogenes Gram-Negative Bacteria Enterobacter cloacae Escherichia coli Haemophilus influenzae Haemophilus parainfluenzae Klebsiella pneumoniae Legionella pneumophila Moraxella catarrhalis Proteus mirabilis Pseudomonas aeruginosa Serratia marcescens

Levofloxacin is an antibiotic that covers for cellulitis and Proteus mirabilis. Since the patient has a penicillin allergy, and levofloxacin is a fluoroquinolone antibiotic, it may be a suitable alternative. However, it is essential to consult a healthcare professional to determine the best course of treatment. 2

From the Research

Antibiotic Coverage for Cellulitis and Proteus Mirabilis

For a patient with a penicillin allergy, the choice of antibiotic for cellulitis and Proteus mirabilis infection is crucial.

• The following antibiotics have been shown to be effective against Proteus mirabilis:
  • Imipenem 3, 4
  • Aztreonam 3
  • Cefoperazone/sodium sulbactam 4
  • Levofloxacin 4
  • Sulfamethoxazole 4
  • Cefoxitin 4
  • Ceftazidime 4, 5
  • Ciprofloxacin 5
• It is essential to note that the susceptibility of Proteus mirabilis to antibiotics can vary by sex, season, and year 4.
• The formation of biofilms by Proteus mirabilis can also impact the effectiveness of antibiotics, with some antibiotics able to eradicate biofilms 5.
• For cellulitis, the chosen antibiotic should also be effective against common causes of cellulitis, such as Streptococcus and Staphylococcus species.
• In the case of a penicillin allergy, it is crucial to select an antibiotic that is safe and effective for the patient.