The spectrum of activity and pharmacology of combination beta-lactamase inhibitors, carbapenems, and monobactams will be reviewed here. The mechanisms of action and resistance and major adverse reactions of the beta-lactam antibiotics, issues related to penicillins and cephalosporins are discussed separately. (See "Beta-lactam antibiotics: Mechanisms of action and resistance and adverse effects" and "Penicillins" and "Cephalosporins".)
Clavulanate, sulbactam, and tazobactam are beta-lactamase inhibitors that have little intrinsic antibacterial activity but inhibit the activity of a number of plasmid-mediated beta-lactamases . They generally do not inhibit chromosomally mediated beta-lactamases . Combination of these agents with ampicillin, amoxicillin, ticarcillin, or piperacillin results in antibiotics with an enhanced spectrum of activity against many, but not all, organisms containing plasmid-mediated beta-lactamases. In addition, these compounds inhibit the chromosomal beta-lactamase of many Bacteroides species, extending the spectrum of coverage for these organisms as well.
Amoxicillin-clavulanate will inhibit most strains of oxacillin-sensitive Staphylococcus aureus and beta-lactamase producing Haemophilus influenzae in addition to the usual organisms inhibited by amoxicillin alone. (See "Penicillins".) At the high drug concentrations achieved in urine, the combination is also active against certain beta-lactamase producing Enterobacteriaceae. Amoxicillin-clavulanate (Augmentin) (250 to 500 mg PO Q 8h or 875 mg PO Q12h) can be used as oral therapy for patients with otitis media, sinusitis, lower respiratory infections, bite wounds, and urinary tract infections , although there are no data that this combination is superior to other antibiotics (such as trimethoprim-sulfamethoxazole or the second or third generation oral cephalosporins). (See "Soft tissue infections due to dog and cat bites".)
Ampicillin-sulbactam is a parenteral formulation that expands the spectrum of ampicillin to include most strains of S. aureus and beta-lactamase producing H. influenzae, some Enterobacteriaceae, and anaerobes (including Bacteroides fragilis). The sulbactam component of ampicillin-sulbactam has activity against many strains of Acinetobacter baumannii. Ampicillin-sulbactam has been used to treat patients with diabetic foot ulcers . This combination has also been used for prophylaxis and therapy of intraabdominal and pelvic infections instead of cefoxitin. Randomized, double-blind trials showed ampicillin-sulbactam to be equivalent to cefoxitin in prophylaxis for abdominal surgery and in the treatment of intraabdominal and pelvic infections [5,6]. However, increasing resistance worldwide to ampicillin-sulbactam of both Enterobacteriaceae and Bacteroides fragilis in intra-abdominal infections renders this drug combination less useful for this purpose [7-9].
Ticarcillin-clavulanate and piperacillin-tazobactam expand the spectrum of the respective penicillins to include beta-lactamase producing S. aureus, H. influenzae, Neisseria gonorrhoeae, some Enterobacteriaceae, and anaerobes (including B. fragilis) . These combinations are generally not effective for ticarcillin- or piperacillin-resistant strains of Pseudomonas aeruginosa. In addition, piperacillin-tazobactam, dosed at 3.375 g every six hours, may not be an adequate dose for the treatment of P. aeruginosa infections. Thus, the spectrum and clinical utility of these two agents are similar to ampicillin-sulbactam, but they are preferred over ampicillin-sulbactam for intra-abdominal infection when an agent from this class is chosen. (See "Anaerobic bacterial infections", section on 'Antibiotic treatment'.)