Choice of Route of Administration for Empiric Treatment

Oral Antibiotics

• If lymphadenopathy, fever & other constitutional signs are not present [eg white blood cells (WBC) <15,000], then may typically treat patient w/ oral antibiotics on an outpatient basis

Parenteral Antibiotics

• If symptoms do not improve or if disease progresses significantly w/in the first 24-48 hours parenteral therapy may be needed
• If lymphadenopathy, fever or constitutional signs are present
• Neonates should be admitted & given initial parenteral therapy if w/ moderate to severe presentation
• Considered in patients w/ comorbidities [eg diabetes mellitus (DM), peripheral vascular diseases]

Choice of Antibiotic

• Tailored according to known pathogen, comorbid condition, & special situations like water (eg salt or freshwater) exposure or animal bites
  
  • Treatment should also address underlying predisposing conditions
• Empiric therapy may be started pending culture results
  
  • For patients w/ purulent cellulitis, treatment is directed towards Methicillin-resistant S aureus (MRSA) since it is the dominant pathogen in this type of cellulitis; therapy for beta-hemolytic streptococci is likely not needed
  • For patients w/ nonpurulent cellulitis, treatment is directed towards Methicillin-sensitive S aureus (MSSA) & beta-hemolytic streptococci
    
    • Empiric therapy for MRSA may be needed if patient has signs of systemic infection, is unresponsive to initial therapy, has recurrent infection, or has a previous episode of or is at high risk for MRSA infection

Penicillins (Beta-lactamase resistant)

• Recommended therapy for patients w/ erysipelas, moderate nonpurulent & purulent cellulitis, & MRSA infection
• Recommended antibiotics against mild nonpurulent cellulitis caused by group A Streptococcus or S aureus
  
  • Some authorities recommend antistaphylococcal penicillin alone while others advocate antistaphylococcal penicillin + Penicillin or Amoxicillin
  • Combination may increase adverse effects 
• Recommended for initial treatment of neonates w/ moderate to severe cellulitis
• Also recommended for recurrent cellulitis

Penicillin G [Intravenous (IV)]

• Used for erysipelas & moderate nonpurulent uncomplicated cellulitis
• Treatment option for patients w/ recurrent cellulitis
• Observe patient for localized S aureus infection

Cephalosporins (1st Generation)

• If staphylococcal infection is suspected
• Usually sufficient for mild nonpurulent uncomplicated cellulitis

Cephalosporins (2nd & 3rd Generation) [Parenteral]

• Usually used empirically in diabetes mellitus (DM) patients who have early mild cellulitis
• Treatment alternative for patients w/ moderate nonpurulent cellulitis

Aminopenicillin/Beta-Lactamase Inhibitors

• Considered 2nd-line alternative by some authorities
• Effective & especially useful in the presence of bone or joint infection

Macrolides

• Eg Erythromycin, Roxithromycin
• May be used if patient is allergic to Penicillin
• Macrolide resistance among Group A Streptococci has increased & has become a concern in some countries
• Erythromycin is the main macrolide used unless Erythromycin resistance is widespread in the community
• Also used for prophylactic treatment against recurrent cellulitis
• Studies showed that the efficacy of Roxithromycin for erysipelas was comparable to that of Benzylpenicillin

Other Antibiotics

• Clindamycin
  • Used in patients allergic to Penicillin & cephalosporins
  • Alternative therapy for patients w/ nonpurulent or purulent cellulitis caused by Methicillin-sensitive S aureus (MSSA) or Methicillin-resistant S aureus (MRSA) infection

• Co-trimoxazole
  • Used for nonpurulent cellulitis & moderate purulent cellulitis
  • Has very good activity against community-acquired MRSA but not to streptococci

• Linezolid
  • Used in patients allergic to Penicillin & for complicated cellulitis & erysipelas

• Vancomycin
  • Treatment option for patients allergic to Penicillin
  • Combination w/ Piperacillin/Tazobactam or Imipenem/Meropenem is recommended for patients w/ severe nonpurulent cellulitis
  • Combination w/ Cefotaxime or Gentamicin is recommended as 1st-line parenteral treatment for neonates w/ MRSA infections
  • Also used for patients w/ penetrating trauma, nasal colonization w/ MRSA, & IV drug use

Quinolones

• Eg Ciprofloxacin, Levofloxacin, Moxifloxacin, Ofloxacin
• Those that have enhanced activity against Gram-positive bacteria have been shown to be effective
• Used for cellulitis caused by Vibrio vulnificus
• Not recommended for patients living in MRSA-prevalent regions

Tetracyclines

• Eg Doxycycline, Minocycline
• May be considered for moderate-severe purulent cellulitis, MSSA, & MRSA infections

Length of Therapy

• It is typically recommended that once erythema, warmth & edema have subsided significantly, patient  may be treated for an additional 10 days w/ oral antibiotics
• Antibiotic therapy for neonates is usually administered for 7-10 days; 5-10 days for patients >1 month
• Treatment duration may be extended for severe cases