Pharmacotherapeutic group: Antibacterials for systemic use, Combinations of penicillins incl. beta-lactamase inhibitors; ATC code: J01C R05
Mechanism of action
Piperacillin, a broad-spectrum, semisynthetic penicillin exerts bactericidal activity by inhibition of both septum and cell-wall synthesis.
Tazobactam, a beta-lactam structurally related to penicillins, is an inhibitor of many beta-lactamases, which commonly cause resistance to penicillins and cephalosporins but it does not inhibit AmpC enzymes or metallo beta-lactamases. Tazobactam extends the antibiotic spectrum of piperacillin to include many beta-lactamase-producing bacteria that have acquired resistance to piperacillin alone.
Pharmacokinetic/Pharmacodynamic effects
The time above the minimum inhibitory concentration (T>MIC) is considered to be the major pharmacodynamic determinant of efficacy for piperacillin.
Mechanism of resistance
The two main mechanisms of resistance to piperacillin / tazobactam are:
• Inactivation of the piperacillin component by those beta-lactamases that are not inhibited by tazobactam: beta-lactamases in the Molecular class B, C and D.
• Alteration of penicillin-binding proteins (PBPs), which results in the reduction of the affinity of piperacillin for the molecular target in bacteria.
Additionally, alterations in bacterial membrane permeability, as well as expression of multi-drug efflux pumps, may cause or contribute to bacterial resistance to piperacillin/tazobactam, especially in Gram-negative bacteria.
Susceptibility testing breakpoints
MIC (minimum inhibitory concentration) interpretive criteria for susceptibility testing have been established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for Piperacillin/Tazobactam and are listed here:
https://www.ema.europa.eu/documents/other/minimum-inhibitory-concentration-mic-breakpoints_en.xlsx”
Susceptibility
The prevalence of acquired resistance may vary geographically and with time for selected species, and local information on resistance is desirable, particularly when treating severe infections. As necessary, expert advice should be sought when the local prevalence of resistance is such that the utility of the agent in at least some types of infections is questionable.
| Groupings of relevant species according to piperacillin/tazobactam susceptibility |
| COMMONLY SUSCEPTIBLE SPECIES |
| Aerobic Gram-positive micro-organisms |
| Enterococcus faecalis (ampicillin- or penicillin-susceptible isolates only) |
| Listeria monocytogenes |
| Staphylococcus aureus (methicillin-susceptible isolates only) |
| Staphylococcus species, coagulase negative (methicillin-susceptible isolates only) |
| Streptococcus agalactiae (Group B streptococci)† |
| Streptococcus pyogenes (Group A streptococci)† |
| Aerobic Gram-negative micro-organisms |
| Citrobacter koseri |
| Haemophilus influenza |
| Moraxella catarrhalis |
| Proteus mirabilis |
| Anaerobic Gram-positive micro-organisms |
| Clostridium species |
| Eubacterium species |
| Anaerobic gram-positive cocci†† |
| Anaerobic Gram-negative micro-organisms |
| Bacteroides fragilis group |
| Fusobacterium species |
| Porphyromonas species |
| Prevotella species |
| SPECIES FOR WHICH ACQUIRED RESISTANCE MAY BE A PROBLEM |
| Aerobic Gram-positive micro-organisms |
| Enterococcus faecium |
| Streptococcus pneumonia† |
| Streptococcus viridans group† |
| Aerobic Gram-negative micro-organisms |
| Acinetobacter baumannii |
| Citrobacter freundii |
| Enterobacter species |
| Escherichia coli |
| Klebsiella pneumoniae |
| Morganella morganii |
| Proteus vulgaris |
| Providencia ssp. |
| Pseudomonas aeruginosa |
| Serratia species |
| INHERENTLY RESISTANT ORGANISMS |
| Aerobic Gram-positive micro-organisms |
| Corynebacterium jeikeium |
| Aerobic Gram-negative micro-organisms |
| Burkholderia cepacia |
| Legionella species |
| Ochrobactrum anthropi |
| Stenotrophomonas maltophilia |
| Other microorganisms |
| Chlamydophilia pneumonia |
| Mycoplasma pneumonia |
| † Streptococci are not β-lactamase producing bacteria; resistance in these organisms is due to alterations in penicillin-binding proteins (PBPs) and, therefore, susceptible isolates are susceptible to piperacillin alone. Penicillin resistance has not been reported in S. pyogenes. †† Including Anaerococcus, Finegoldia, Parvimonas, Peptoniphilus, and Peptostreptococcus spp. |
Merino Trial (blood stream infections due to ESBL producers)
In a prospective, non-inferiority, parallel-group, published randomized clinical trial, definitive (i.e. based on susceptibility confirmed in-vitro) treatment with piperacillin/tazobactam, compared with meropenem, did not result in a non-inferior 30-day mortality in adult patients with ceftriaxone-non-susceptible E. coli or K. pneumoniae blood stream infections.
A total of 23 of 187 patients (12.3%) randomized to piperacillin/tazobactam met the primary outcome of mortality at 30 days compared with 7 of 191 (3.7%) randomized to meropenem (risk difference, 8.6% [1-sided 97.5% CI − ∞ to 14.5%]; P = 0.90 for non-inferiority). The difference did not meet the non-inferiority margin of 5%.
Effects were consistent in an analysis of the per-protocol population, with 18 of 170 patients (10.6%) meeting the primary outcome in a piperacillin/tazobactam group compared with 7 of 186 (3.8%) in the meropenem group (risk difference, 6.8% [one-sided 97.5% CI, - ∞ to 12.8%]; P = 0.76 for non-inferiority).
Clinical and microbiological resolution (secondary outcomes) by day 4 occurred in 121 of 177 patients (68.4%) in the piperacillin/tazobactam group compared with 138 of 185 (74.6%), randomized to meropenem (risk difference, 6.2% [95% CI − 15.5 to 3.1%]; P = 0.19). For secondary outcomes, statistical tests were 2-sided, with a P <0.05 considered significant.
In this trial, a mortality imbalance between study groups was found. It was supposed that deaths occurred in piperacillin/tazobactam group were related to underlying diseases rather than to the concomitant infection.