Activity of ticarcillin/clavulanate and piperacillin/tazobactam (YTR 830; CL-298,741) against clinical isolates and against mutants derepressed for class I beta-lactamase

In vivo evolution of resistance of Pseudomonas aeruginosa strains isolated from patients admitted to an intensive care unit: mechanisms of resistance and antimicrobial exposure

OBJECTIVES

The main objective of this study was to investigate the relationship among the in vivo acquisition of antimicrobial resistance in Pseudomonas aeruginosa clinical isolates, the underlying molecular mechanisms and previous exposure to antipseudomonal agents.

METHODS

PFGE was used to study the molecular relatedness of the strains. The MICs of ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, ciprofloxacin and amikacin were determined. Outer membrane protein profiles were assessed to study OprD expression. RT-PCR was performed to analyse ampC, mexB, mexD, mexF and mexY expression. The presence of mutations was analysed through DNA sequencing.

RESULTS

We collected 17 clonally related paired isolates [including first positive samples (A) and those with MICs increased ≥4-fold (B)]. Most B isolates with increased MICs of imipenem, meropenem and ceftazidime became resistant to these drugs. The most prevalent resistance mechanisms detected were OprD loss (65%), mexB overexpression (53%), ampC derepression (29%), quinolone target gene mutations (24%) and increased mexY expression (24%). Five (29%) B isolates developed multidrug resistance. Meropenem was the most frequently (71%) received treatment, explaining the high prevalence of oprD mutations and likely mexB overexpression. Previous exposure to ceftazidime showed a higher impact on selection of increased MICs than previous exposure to piperacillin/tazobactam.

CONCLUSIONS

Stepwise acquisition of resistance has a critical impact on the resistance phenotypes of P. aeruginosa, leading to a complex scenario for finding effective antimicrobial regimens. In the clinical setting, meropenem seems to be the most frequent driver of multidrug resistance development, while piperacillin/tazobactam, in contrast to ceftazidime, seems to be the β-lactam least associated with the selection of resistance mechanisms.

Cross-Canada survey of resistance of 2747 aerobic blood culture isolates to piperacillin/tazobactam and other antibiotics

OBJECTIVE

To compare the activity of piperacillin/tazobactam with that of other broad parenteral antibiotics against aerobic and facultative anaerobic blood culture isolates in a Canada-wide survey.

DESIGN

Fifty-eight laboratories in nine provinces each contributed up to 50 consecutive clinically significant aerobic and facultative anaerobic isolates for susceptibility testing.

SETTING

Participating hospitals included both tertiary care and community hospitals.

MATERIALS AND METHODS

Testing was performed in five regional centres by using the same microbroth dilution method, and results were interpreted according to National Commitee for Clinical Laboratory Standards M7-A3 and M100-S5 guidelines.

RESULTS

Piperacillin/tazobactam and imipenem were both active against more than 99% of the 1616 strains of Enterobacteriaceae species tested. The minimum inhibitory concentration of 90% of isolates (MIC(90)) of all Enterobacteriaceae species was 2 mg/L for piperacillin/tazobactam compared with 64 mg/L for piperacillin alone. Seventeen per cent of strains of Enterobacteriaceae species were susceptible to piperacillin/tazobactam but resistant to piperacillin. Piperacillin/tazobactam was highly active against Pseudomonas aeruginosa, inhibiting 99.1% of strains. MIC(90) was 8 mg/L. Nine per cent of P aeruginosa strains were not susceptible to imipenem. Most of these strains had a MIC of 8 mg/L, which falls in the intermediate category. Ninety-seven per cent of P aeruginosa were susceptible to ciprofloxacin and 97.3% to tobramycin. Ninety-six per cent of strains of Actinobacter species were susceptible to piperacillin/tazobactam, whereas only 76% of strains were susceptible to piperacillin alone. Overall, piperacillin/tazobactam was the most active agent tested; 98% of all strains were susceptible, followed closely by imipenem, to which 97.8% of strains were susceptible.

CONCLUSIONS

Aerobic blood culture isolates from Canadian centres continue to be highly susceptible to a variety of antibiotics. The broad spectrum of activity of piperacillin/tazobactam suggests that this combination should be considered for empirical treatment of sepsis while awaiting results of cultures and susceptibility testing.

Antimicrobial agents for the dermatologist. I. Beta-lactam antibiotics and related compounds

We review the newer antimicrobial agents that are being employed by dermatologists with increased frequency as well as some of the more commonly used older agents. Particular emphasis is based on selection factors such as causative pathogens and their resistance profiles, routes of administration, toxicity, drug interactions, and dosing requirements. Emphasis in this review is on the newer classes of antimicrobials such as third- and fourth-generation cephalosporins; beta-lactam, beta-lactamase inhibitor combination agents; monobactams; carbapenems; macrolides; and fluoroquinolones. Dermatologic indications and treatment alternatives are highlighted; this will expand the practicing clinician's therapeutic armamentarium and enable him/her to make rational decisions concerning treatment approaches to infectious disease problems encountered in daily practice.

Piperacillin/tazobactam: a new beta-lactam/beta-lactamase inhibitor combination

OBJECTIVE

To discuss the antimicrobial activity, pharmacokinetics, clinical efficacy, and adverse effect profile of piperacillin/tazobactam, a new beta-lactan/beta-lactamase inhibitor combination.

DATA SOURCES

Literature was identified by MEDLINE search of the medical literature, review of selected references, and data provided by the manufacturer.

STUDY SELECTION

In vitro susceptibility data were surveyed from studies following the methods of the National Committee for Clinical Laboratory Standards. Data evaluating clinical efficacy were selected from all published trials and abstracts. Additional information concerning safety, chemistry, and pharmacokinetics was reviewed.

DATA SYNTHESIS

The antimicrobial activity of piperacillin is enhanced by addition of tazobactam against gram-positive, gram-negative, and anaerobic bacteria. Tazobactam is active against a broad spectrum of plasmid and chromosomally mediated enzymes and has minimal ability to induce class I chromosomally mediated beta-lactamase enzymes. Piperacillin/tazobactam's expanded activity appears encouraging in the treatment of mixed aerobic and anaerobic infections. Direct comparisons of ticarcillin/clavulanate and piperacillin/tazobactam for the treatment of lower respiratory tract infections showed piperacillin/tazobactam to be clinically superior, and in the treatment of skin and soft tissue infections the 2 agents were comparable. For the treatment of intraabdominal infections, piperacillin/tazobactam was at least as effective as imipenem/cilastatin and clindamycin plus gentamicin.

CONCLUSIONS

The combination of tazobactam with piperacillin results in an antimicrobial agent with enhanced activity against most beta-lactamase-producing organisms. Preliminary data indicate that piperacillin/tazobactam has proven clinical efficacy in the treatment of a variety of infections, especially polymicrobic infections.

A piperacillin-tazobactam resistant Escherichia coli strain isolated from a faecal sample of a healthy volunteer

As part of a surveillance programme of the prevalence of antibiotic resistance, the faecal bacteria of healthy people (n = 1348) were examined, and the antibiotic resistance of the Escherichia coli strains determined. One strain out of 142 amoxycillin-resistant isolates, E. coli strain 1662, was also resistant to piperacillin-tazobactam but susceptible to amoxycillin-clavulanic acid. The piperacillin-tazobactam resistance determinant was transferable to standard E. coli strains by conjugation. However, the strain produced a beta-lactamase with several characteristics very similar to those of the TEM-1 beta-lactamase, i.e. pI of 5.4, an M(r) value of 22,000 and a comparable substrate profile. The enzyme was as efficiently inhibited by clavulanic acid and tazobactam as the TEM-1 and TEM-2 beta-lactamases but more than the amoxycillin-clavulanic acid-resistant TRC-1 enzyme. The transferable resistance to piperacillin-tazobactam appears to be mediated by a novel resistance mechanism that has previously not been described.

Comparative antimicrobial activity of piperacillin-tazobactam tested against more than 5000 recent clinical isolates from five medical centers. A reevaluation after five years

Piperacillin combined with tazobactam at a fixed concentration (4 micrograms/ml) and a ratio (8:1) was tested against 5,029 aerobic isolates and 447 fastidious organisms, including anaerobes. Among the Enterobacteriaceae, > 95% inhibition was shared only by imipenem (99.1% at < or = 4 micrograms/ml), and some newer cephalosporins (95.1% - 99.8% at < or = 8 micrograms/ml), and piperacillin-tazobactam (95.8% at < or = 16/4 micrograms/ml). Piperacillin-tazobactam was the most active agent tested against nonenteric Gram-negative bacilli (93.5% at < or = 8 micrograms/ml). Ampicillin-sulbactam was the most active agent against staphylococci (95.0% at < or = 8 micrograms/ml), followed by imipenem (91.8%), piperacillin-tazobactam (89.3% at < or = 8/4 micrograms/ml), and cefepime (86.2% at < or = 8 micrograms/ml). Against the enterococci, only ampicillin (93.0% at < or = 8 micrograms/ml) with or without sulbactam, piperacillin (91.0% at < or = 16 micrograms/ml) with or without tazobactam, and imipenem (91.0%) had acceptable activity. Piperacillin-tazobactam and imipenem were the most active drugs tested against all aerobic isolates, inhibiting 93.5% of isolates each. Piperacillin-tazobactam inhibited all fastidious isolates tested, including Haemophilus influenzae (MIC90, 0.094/4 micrograms/ml), Moraxella catarrhalis (MIC90, 0.064/4 micrograms/ml), Neisseira gonorrhoeae (MIC90, < or = 0.016/4 micrograms/ml), and Streptococcus pneumoniae (all MICs, < or = 4/4 micrograms/ml). Against the anaerobic isolates, the most broad-spectrum antimicrobial agents tested were imipenem (100.0%), piperacillin-tazobactam (99.5% at < or = 32/4 micrograms/ml), metronidazole (98.4% at < or = 8 micrograms/ml), and ticarcillin-clavulanic acid (95.1% at < or = 32/2 micrograms/ml). These results are nearly identical to a previous study involving the same five medical centers in 1989. Piperacillin-tazobactam appears to remain a highly effective beta-lactamase inhibitor combination with a wide empiric spectrum and potency in teaching hospitals.

Piperacillin/tazobactam. A review of its antibacterial activity, pharmacokinetic properties and therapeutic potential

Combining tazobactam, a beta-lactamase inhibitor, with the ureidopenicillin, piperacillin, successfully restores the activity of piperacillin against beta-lactamase-producing bacteria. Tazobactam has inhibitory activity, and therefore protects piperacillin against Richmond and Sykes types II, III, IV and V beta-lactamases, staphylococcal penicillinase and extended-spectrum beta-lactamases. However, tazobactam has only species-specific activity against class I chromosomally-mediated enzymes. Resistant organisms include some Citrobacter spp., Enterobacter spp., Serratia spp., Xanthomonas maltophilia and Enterococcus faecium. Consistent with its in vitro activity, preliminary clinical data indicate that the fixed combination of piperacillin/tazobactam (dose ratio 8:1) is effective in the treatment of moderate to severe polymicrobial infections, including intra-abdominal, skin and soft-tissue and lower respiratory tract infections. In limited comparative trials, piperacillin/tazobactam demonstrated equivalent or better efficacy than standard comparator regimens in these infections. Piperacillin/tazobactam in combination with an aminoglycoside was effective in the empirical treatment of fever in patients with neutropenia and compared favourably with ceftazidime in combination with an aminoglycoside, although second-line therapy with a glycopeptide antibiotic may be indicated in unresponsive episodes. Data from phase III trials indicate that piperacillin/tazobactam has a tolerability profile typical of a penicillin agent. Piperacillin/tazobactam provides a broad spectrum of antibacterial activity in a convenient single formulation suitable for use in the treatment of polymicrobial infections. Possible limitations concern its restricted activity against class I beta-lactamases, enzymes that are becoming increasingly important in the nosocomial environment. Combined therapy with an aminoglycoside may be necessary in more serious infections.

Piperacillin/tazobactam/amikacin versus piperacillin/amikacin/teicoplanin in the empirical treatment of neutropenic patients

A prospective randomized trial was performed to compare the efficacy of a regimen containing a glycopeptide versus one containing a beta-lactamase inhibitor in the treatment of febrile episodes in neutropenic patients. Fifty-eight patients received piperacillin/amikacin/teicoplanin (group 1) and 56 received piperacillin/amikacin/tazobactam (group 2). In the case of persistence of fever without microbiological documentation of the cause, teicoplanin was also given empirically in group 2 on day 4, and amphotericin B in both groups on day 6. In 114 evaluable febrile episodes, the rate of success without modification of therapy was 60% in patients on piperacillin/amikacin/teicoplanin and 41% in patients on piperacillin/amikacin/tazobactam (p < 0.03). Eleven of 34 patients in the latter group who failed to improve eventually responded upon addition of teicoplanin. Ten and nine patients in group 1 and group 2 respectively required the addition of amphotericin B for definite improvement. There were 14 episodes of gram-positive septicemia in each group: the response rate was 100% in group 1 and 43% in group 2. Three episodes of gram-negative breakthrough septicemia occurred in group 1 versus no cases in group 2 (p = 0.1). Three deaths occurred in each group. Piperacillin/amikacin/tazobactam may be as efficacious as piperacillin/amikacin/teicoplanin in the treatment of febrile neutropenic patients provided the regimen is modified (usually by addition of teicoplanin) in unresponsive cases.

Comparison of fixed concentration and fixed ratio options for testing susceptibility of gram-negative bacilli to piperacillin and piperacillin/tazobactam

Piperacillin combined with tazobactam was tested at both a fixed ratio (8:1) and fixed tazobactam concentration (4 micrograms/ml) against 2,685 consecutively isolated gram-negative bacilli and 56 highly piperacillin-resistant isolates. Tazobactam significantly enhanced the spectrum of piperacillin activity. Overall, at a concentration of 16 micrograms/ml piperacillin alone inhibited 78.8% of the Enterobacteriaceae isolates compared to inhibition of 92.7% and 95.5% by the 8:1 ratio and fixed (4 micrograms/ml) tazobactam combinations, respectively. In MIC tests the two combination options performed comparably against both routine and highly piperacillin-resistant isolates. Synergistic inhibition was observed for comparable numbers of isolates with the two combination options, the most marked effect being seen in the more highly piperacillin-resistant isolates. Both testing options are supported by the available human pharmacokinetic data; however the 8:1 ratio of piperacillin to tazobactam may be preferable given that the clinical formulation contains the two compounds in an 8:1 ratio and this ratio is maintained in vivo.