From the Guidelines
Zosyn (piperacillin/tazobactam) is generally effective for treating most Bacteroides infections, but its use should be guided by local resistance patterns and the severity of the infection, as some Bacteroides strains have shown increasing resistance to beta-lactam/beta-lactamase inhibitor combinations 1.
Key Considerations
- The combination of piperacillin (a penicillin) with tazobactam (a beta-lactamase inhibitor) provides good coverage against Bacteroides fragilis and other Bacteroides species, which are common anaerobic pathogens.
- Typical dosing for adults with normal renal function is 3.375g (3g piperacillin/0.375g tazobactam) administered intravenously every 6 hours, or 4.5g (4g piperacillin/0.5g tazobactam) every 8 hours.
- Treatment duration typically ranges from 7-14 days depending on the severity and site of infection.
- For severe infections, particularly intra-abdominal abscesses or complicated infections, combination therapy with metronidazole (500mg IV every 8 hours) might be considered for enhanced anaerobic coverage.
- Alternatively, carbapenems like meropenem or imipenem may be more appropriate for resistant strains.
Resistance Patterns
- Some Bacteroides strains have shown increasing resistance to beta-lactam/beta-lactamase inhibitor combinations in recent years 1.
- The emergence of resistance in B. fragilis group isolates, especially against metronidazole, has important implications in the treatment of surgical infections.
- Local resistance patterns should guide the selection of empiric antibiotic therapy, with consideration of the individual risk for infection by resistant pathogens and the local resistance epidemiology 1.
Treatment Recommendations
- Zosyn (piperacillin/tazobactam) can be used as empiric therapy for community-acquired intra-abdominal infections, but its use should be guided by local resistance patterns and the severity of the infection.
- For healthcare-associated infections, antibiotic regimens with broader spectra of activity are preferred, and Zosyn may not be the first choice due to concerns about resistance 1.
- The choice of empiric antibiotic regimens should be based on the clinical condition of the patients, the individual risk for infection by resistant pathogens, and the local resistance epidemiology 1.
From the FDA Drug Label
Piperacillin and tazobactam for injection is indicated in adults and pediatric patients (2 months of age and older) for the treatment of appendicitis (complicated by rupture or abscess) and peritonitis caused by beta-lactamase producing isolates of Escherichia coli or the following members of the Bacteroides fragilis group: B. fragilis, B. ovatus, B. thetaiotaomicron, or B. vulgatus.
Zosyn (piperacillin/tazobactam) is sufficient for treating certain Bacteroides infections, specifically those caused by beta-lactamase producing isolates of B. fragilis, B. ovatus, B. thetaiotaomicron, or B. vulgatus in the context of intra-abdominal infections, such as appendicitis or peritonitis 2.
From the Research
Efficacy of Zosyn Against Bacteroides Infections
- Zosyn, a combination of piperacillin and tazobactam, has been shown to be effective against Bacteroides infections in various studies 3, 4, 5, 6.
- A case report from 2019 described a diabetic patient with a Bacteroides caccae bloodstream infection that was successfully treated with a combination of intravenous piperacillin/tazobactam and oral ornidazole 3.
- In vitro studies have demonstrated that piperacillin/tazobactam has a broad spectrum of activity against anaerobic bacteria, including Bacteroides fragilis 4, 5, 6.
- The combination of piperacillin and tazobactam has been shown to be more effective than piperacillin alone against Bacteroides fragilis group organisms 5, 6.
Mechanism of Action and Resistance
- Piperacillin/tazobactam works by inhibiting cell wall synthesis in bacteria, and tazobactam also inhibits beta-lactamase enzymes that can inactivate piperacillin 4.
- Resistance to piperacillin/tazobactam can occur through various mechanisms, including the production of beta-lactamase enzymes and changes in the penicillin-binding proteins 7.
- A study from 2010 found that the acquisition of piperacillin/tazobactam resistance in Bacteroides fragilis may enhance the pathogenic properties of these strains 7.
Clinical Implications
- Zosyn may be a suitable treatment option for Bacteroides infections, particularly in cases where the infection is caused by susceptible strains of Bacteroides fragilis or other anaerobic bacteria 3, 4, 5, 6.
- However, the development of resistance to piperacillin/tazobactam is a concern, and alternative treatment options may be necessary in cases where resistance is suspected or confirmed 7.