Ampicillin-Sulbactam

Emery Haley, PhD, Scientific Writing Specialist

Ampicillin/Sulbactam

Find the Latest FDA-Approved Labelling Information Here: Drugs@FDA Online Database 

Administrative Routes

Parenteral [intravenous infusion (IV) or intramuscular injection (IM)]

Other Names

Unasyn

Bacteriostatic or Bactericidal

Bactericidal [1]

Antibiotic Class

Penicillin/Beta-lactamase Inhibitor Combination

Mechanisms of Action

This antibiotic leverages dual mechanisms of action.   

Ampicillin, a beta-lactam antibiotic, binds to penicillin-binding proteins (PBPs) on bacterial cell walls. PBPs are essential for the formation of the peptidoglycan, which gives the bacterial wall strength and integrity. Binding of ampicillin to PBPs leads to failure of peptidoglycan cell wall synthesis, causing bacterial cell death.   

Some bacteria develop resistance to beta-lactam antibiotics, like ampicillin, by producing enzymes, called beta-lactamases, that degrade the antibiotic. Sulbactam helps preserve the activity of beta-lactam antibiotics by inhibiting these enzymes and allowing ampicillin to then bind to PBPs and cause bacterial cell wall degradation. 

WHO AWaRe Classification

Access [2]

Empiric Use Recommendations

No published guidance

Indication(s) Relevant to UTI

Not indicated for UTIs as per Prescribing Information.   

Indicated for skin and skin structure infections, intraabdominal infections, or gynecological infections caused by beta-lactamase producing strains of the following organisms included in the Guidance UTI test: Staphylococcus aureus, Escherichia coli, Klebsiella species, Proteus mirabilis, or Enterobacter species.   

Since these organisms can also cause UTIs, and because of increasing frequency of beta-lactamase production among these organisms, healthcare providers may exercise their clinical discretion to use ampicillin/sulbactam for treatment of the above organisms when they are uropathogens. 

Checkmarks

CLSI and/or FDA documents support the efficacy of this antibiotic against the following organisms from the Guidance® UTI test: Acinetobacter baumannii, Aerococcus urinae, Citrobacter koseri, Corynebacterium riegelii, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, and Providencia stuartii.  

Published primary literature supports the efficacy of this antibiotic against the following organisms from the Guidance® UTI test: Alloscardovia omnicolens ​[3], and Actinotignum schaalii ​[4-6]