From the Guidelines
Susceptibility to amoxicillin is not always indicative of susceptibility to Augmentin (Amoxicillin-Clavulanate), as resistance mechanisms other than beta-lactamase production can affect the efficacy of both antibiotics. When considering the treatment of infections, it's crucial to understand the mechanisms of resistance and the spectrum of activity of the antibiotics in question.
- Amoxicillin is a broad-spectrum antibiotic effective against a variety of bacterial infections.
- Augmentin, which combines amoxicillin with clavulanic acid, a beta-lactamase inhibitor, extends the spectrum of activity to include bacteria that produce beta-lactamases, enzymes that can inactivate amoxicillin 1. However, as noted in a study published in the Journal of Microbiology, Immunology and Infection in 2019 1, while all isolates of M. catarrhalis were susceptible to amoxicillin/clavulanate, the high rates of ampicillin resistance due to beta-lactamase production suggest that susceptibility to amoxicillin alone does not guarantee susceptibility to Augmentin if other resistance mechanisms are present. Key points to consider include:
- The presence of beta-lactamase production in bacteria like M. catarrhalis, which can be overcome by the clavulanic acid in Augmentin 1.
- Other mechanisms of resistance, such as altered penicillin-binding proteins or decreased permeability, which may not be affected by the addition of clavulanic acid. In clinical practice, the choice between amoxicillin and Augmentin should be guided by the suspected or confirmed pathogen and its likely resistance patterns, taking into account the potential for beta-lactamase production and other resistance mechanisms 1.
From the Research
Susceptibility to Amoxicillin and Augmentin
- Susceptibility to amoxicillin does not necessarily indicate susceptibility to Augmentin (amoxicillin-clavulanate) 2, 3.
- Augmentin is active against penicillinase-producing Staphylococci susceptible to methicillin, whereas methicillin-resistant strains are also resistant to Augmentin 3.
- The addition of clavulanic acid to amoxicillin occasionally extends (but does not decrease) the susceptibility of amoxicillin-sensitive bacteria 4.
Mechanism of Action
- Clavulanic acid is a beta-lactamase inhibitor that extends the antibacterial activity of amoxicillin to include beta-lactamase-producing strains, which are otherwise resistant 4.
- The combination of amoxicillin and clavulanic acid is effective against amoxycillin-resistant species such as Bacteroides fragilis 4.
Clinical Implications
- Augmentin may be effective in treating infections caused by amoxicillin-resistant organisms, such as urinary tract infections and lower respiratory tract infections 4.
- The combination of cefixime and amoxicillin/clavulanate may be an effective oral outpatient treatment option for extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) 5.
- In vitro synergistic testing can be simple and predictive of successful treatment with cefixime and amoxicillin/clavulanate combination therapy 5.