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 relationship
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. In addition, tazobactam does not provide protection against extended-spectrum beta-lactamases (ESBLs) in the Molecular class A and D enzyme groups
• 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.
Breakpoints
EUCAST Clinical MIC Breakpoints for piperacillin/tazobactam (EUCAST Clinical Breakpoint Table Version 10.0, valid from 2020-01-01). For susceptibility testing purposes, the concentration of tazobactam is fixed at 4 mg/L.
| Pathogen | Species related breakpoints (S≤/R>), mg/L of piperacillin |
| Enterobacterales (formerly Enterobacteriaceae) | 8/16 |
| Pseudomonas aeruginosa | <0.001/161 |
| Staphylococcus species | -2 |
| Enterococcus species | -3 |
| Streptococcus Groups A, B, C, and G | -4 |
| Streptococcus pneumoniae | -5 |
| Viridans group streptococci | -6 |
| Haemophilus influenzae | 0.25/0.25 |
| Moraxella catarrhalis | -7 |
| Gram-positive anaerobes (except Clostridioides difficile) | 8/16 |
| Gram-negative anaerobes | 8/16 |
| Non-species related (PK/PD) breakpoints | 4/16 |
| 1 For several agents, EUCAST has introduced breakpoints which categorise wild-type organisms (organisms without phenotypically detectable acquired resistance mechanisms to the agent) as "Susceptible, increased exposure (I)" instead of "Susceptible, standard dosing regimen (S)". Susceptible breakpoints for these organism-agent combinations are listed as arbitrary, "off scale" breakpoints of S ≤ 0.001 mg/L. 2 Most staphylococci are penicillinase producers, and some are methicillin resistant. Either mechanism renders them resistant to benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, piperacillin and ticarcillin. Staphylococci that test susceptible to benzylpenicillin and cefoxitin can be reported susceptible to all penicillins. Staphylococci that test resistant to benzylpenicillin but susceptible to cefoxitin are susceptible to β-lactamase inhibitor combinations, the isoxazolylpenicillins (oxacillin, cloxacillin, dicloxacillin and flucloxacillin) and nafcillin. For agents given orally, care to achieve sufficient exposure at the site of the infection should be exercised. Staphylococci that test resistant to cefoxitin are resistant to all penicillins. Ampicillin susceptible S. saprophyticus are mecA-negative and susceptible to ampicillin, amoxicillin and piperacillin (without or with a beta-lactamase inhibitor). 3 Susceptibility to ampicillin, amoxicillin and piperacillin (with and without beta-lactamase inhibitor) can be inferred from ampicillin. Ampicillin resistance is uncommon in E. faecalis (confirm with MIC) but common in E. faecium. 4 The susceptibility of Streptococcus groups A, B, C and G to penicillins is inferred from the benzylpenicillin susceptibility with the exception of phenoxymethylpenicillin and isoxazolylpenicillins for Streptococcus group B. Streptococcus groups A, B, C and G do not produce beta-lactamase. The addition of a beta-lactamase inhibitor does not add clinical benefit. 5 The oxacillin 1 μg disk screen test or a benzylpenicillin MIC test shall be used to exclude beta-lactam resistance mechanisms. When the screen is negative (oxacillin inhibition zone ≥20 mm, or benzylpenicillin MIC ≤0.06 mg/L) all beta-lactam agents for which clinical breakpoints are available, including those with “Note” can be reported susceptible without further testing, except for cefaclor, which if reported, should be reported as “susceptible, increased exposure” (I). Streptococcus pneumoniae do not produce beta-lactamase. The addition of a beta-lactamase inhibitor does not add clinical benefit. Susceptibility inferred from ampicillin (MIC or zone diameter). 6 For isolates susceptible to benzylpenicillin, susceptibility can be inferred from benzylpenicillin or ampicillin. For isolates resistant to benzylpenicillin, susceptibility is inferred from ampicillin. 7 Susceptibility can be inferred from amoxicillin-clavulanic acid. |
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 pneumonia 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.