What antibiotic covers both urinary tract infections (UTIs) and cellulitis?

Antibiotic Coverage for Both UTI and Cellulitis

For patients requiring coverage of both urinary tract infections and cellulitis, amoxicillin-clavulanate is the optimal single-agent choice, as it effectively covers common uropathogens (E. coli, Proteus, Klebsiella) and streptococci responsible for nonpurulent cellulitis. 1, 2

Rationale for Amoxicillin-Clavulanate

• Amoxicillin-clavulanate is recommended as first-line therapy for lower urinary tract infections by the WHO Essential Medicines guidelines, with E. coli susceptibility remaining generally high in urinary isolates 1

• For cellulitis, treatment requires antibiotics active against streptococci, which are the primary causative organisms in nonpurulent cellulitis, and amoxicillin-clavulanate provides excellent streptococcal coverage 1

• Amoxicillin-clavulanate demonstrated superior empirical efficacy compared to other oral antibiotics (cotrimoxazole, ciprofloxacin, cephalothin, ampicillin) for community-acquired UTI in a large retrospective analysis 2

• The combination covers the overlapping pathogen spectrum: E. coli (most common UTI pathogen at 74.5%), Klebsiella species, Proteus species for UTI, plus streptococci and methicillin-sensitive Staphylococcus aureus for cellulitis 2, 1

Dosing Recommendations

• Standard dosing: 875 mg/125 mg twice daily for outpatient management of both conditions 1

• Duration: 5-7 days for cellulitis (per NICE and IDSA guidelines) 1

• Duration: 7-14 days for UTI depending on whether the patient is male (14 days to exclude prostatitis) or female with uncomplicated cystitis (7 days) 1, 3

Alternative Options When Amoxicillin-Clavulanate Cannot Be Used

For Fluoroquinolone-Eligible Patients (No Contraindications)

• Ciprofloxacin 500-750 mg twice daily covers both UTI pathogens and has activity against skin/soft tissue infections, though it is not first-line for cellulitis 1, 4

• Levofloxacin 750 mg once daily provides similar dual coverage with once-daily convenience 1

• Important caveat: Fluoroquinolones carry FDA black box warnings for serious adverse effects (tendon rupture, peripheral neuropathy, CNS effects) and should be reserved for serious infections where benefits outweigh risks 1

For Patients with Beta-Lactam Allergies

• Trimethoprim-sulfamethoxazole 160/800 mg twice daily covers UTI pathogens effectively but has no reliable activity against streptococci causing cellulitis, making it unsuitable for dual coverage 1

• In this scenario, combination therapy is required: TMP-SMX for UTI plus clindamycin or doxycycline for cellulitis 1

Special Considerations for Hospitalized Patients

• Ceftriaxone 1-2 g once daily IV provides excellent coverage for both complicated UTI/pyelonephritis and cellulitis requiring parenteral therapy 1, 5, 6

• Ceftriaxone achieves very high urinary concentrations and has demonstrated excellent clinical and bacteriologic cure rates in complicated UTI 5, 6

• For severe cellulitis with systemic symptoms, ceftriaxone covers streptococci and common gram-negative organisms 1

• Piperacillin-tazobactam 3.375-4.5 g every 6-8 hours IV is an alternative broad-spectrum option for hospitalized patients with both infections 1

Common Pitfalls to Avoid

• Do not use nitrofurantoin for dual coverage—while effective for lower UTI, it achieves inadequate tissue concentrations for cellulitis and has no activity against skin pathogens 1

• Avoid cephalexin monotherapy—though commonly used for cellulitis, first-generation cephalosporins have poor activity against many gram-negative uropathogens including E. coli with ESBL production 1

• Do not use fluoroquinolones as first-line when amoxicillin-clavulanate is suitable, given resistance concerns and serious adverse effect profile 1

• Obtain urine culture before initiating therapy when feasible, especially in males or complicated UTI, to allow targeted therapy adjustment 1, 3

• Consider local resistance patterns—if local E. coli resistance to amoxicillin-clavulanate exceeds 20%, alternative empiric therapy may be warranted 1

When Proteus Species Are Suspected

• Proteus mirabilis can cause both UTI and, rarely, cellulitis in patients with vascular disease or compromised tissue 7

• Amoxicillin-clavulanate remains effective against Proteus species in both infection types 7, 2

• If cultures reveal Proteus cellulitis not responding to initial therapy, consider adjusting to targeted therapy based on susceptibility results 7