Crystal structures of the molecular class A ß-lactamase TEM-171 and its complexes with tazobactam.

The resistance of bacteria to ß-lactam antibiotics is primarily caused by the production of ß-lactamases. Here, novel crystal structures of the native ß-lactamase TEM-171 and two complexes with the widely used inhibitor tazobactam are presented, alongside complementary data from UV spectroscopy and fluorescence quenching. The six chemically identical ß-lactamase molecules in the crystallographic asymmetric unit displayed different degrees of disorder. The tazobactam intermediate was covalently bound to the catalytic Ser70 in the trans-enamine configuration. While the conformation of tazobactam in the first complex resembled that in published ß-lactamase-tazobactam structures, in the second complex, which was obtained after longer soaking of the native crystals in the inhibitor solution, a new and previously unreported tazobactam conformation was observed. It is proposed that the two complexes correspond to different stages along the deacylation path of the acyl-enzyme intermediate. The results provide a novel structural basis for the rational design of new ß-lactamase inhibitors.

Investigation of enzymes and solvents in the production process of 6-ammonium penicillanic acid (6-APA) in industry to reduce costs and improve production conditions.

In this study, the optimization of the amount of enzyme consumed in the enzymatic phase of substitution of butanol solvent instead of methanol in the powder washing phase after filtration was investigated. To perform this study, different amounts of the enzyme penicillin G amidase (PGA) were tested in reactions with the same conditions. The highest efficiency was observed in the reaction that the ratio of penicillin powder to the amount of enzyme was 2:1. In this reaction, for every 100 g of penicillin consumed, 50 g of the PGA was used. Replacement of butanol instead of methanol after filtration, the powder obtained from this step was washed with butanol instead of methanol and the powder obtained from this step was examined after drying. The resulting solvent powder was very small and the drying speed of the powder increased compared to the time of methanol usage. Optimizing the amount of enzyme in this process due to the high cost of the enzyme made this reaction more economically viable at the end of this study. In this study, for the first time, butanol was used as a suitable substitute for methanol and the ratio of enzyme use to penicillin powder was optimized. This research deals with the future perspective in the field of research in this regard.

Electric-field-enhanced selective separation of products of an enzymatic reaction in a membrane micro-contactor.

Processes employed in separations of products of enzyme reactions are often driven by diffusion, and their efficiency can be limited. Here, we exploit the effect of a direct current (DC) electric field that intensifies mass transfer through a semipermeable membrane for fast, continuous, and selective separation of electrically charged molecules. Specifically, we separate low-molecular-weight reaction products (phenylacetic acid, 6-aminopenicillanic acid) from the original reaction mixture containing a free enzyme (penicillin acylase). The developed microfluidic dialysis-membrane contactor allows a stable counter-current arrangement of the retentate and permeates liquid streams on which DC electric field is perpendicularly applied. The applied electric field significantly accelerates the transport of electrically charged products through the semipermeable membrane yielding high separation efficiencies at short residence times. The residence time of 5 min is sufficient to reach 100% separation yield in the electric field. The same residence time provides only a 50% yield in the diffusion-controlled experiments. We experimentally demonstrated that a combined microreactor-microextractor with a recycle of the soluble penicillin acylase can continuously produce both the reaction products at high concentrations. The developed membrane-contactor is a versatile platform allowing to tune its characteristics, such as selectivity given by the membrane, or the type of the retentate phase, for a specific application.

Novel insights into the chemistry of an old medicine: A general degradative pathway for penicillins from a piperacillin/tazobactam stability study.

Piperacillin is a broad spectrum beta-lactam antibiotic used in combination with tazobactam for hospital-related bacterial infections. The reconstituted solutions must respect the sub-visible and visible particles specifications. It was claimed that the reformulation containing EDTA/sodium citrate was able to control the formation of an insoluble impurity responsible for the formation of particulate matter observed using Ringer Lactate as diluent. The nature of the impurities formed during the degradative process of piperacillin/tazobactam combination has been herein investigated, by exploring the effect of added excipients and pH variations. The exact structure of the isolated dimeric impurity, the penicilloic acid-piperacillin dimer, was determined through complete characterization, allowing to propose a novel degradative general pathway for beta-lactam antibiotics. The presence of EDTA resulted unnecessary to contain the formation of the insoluble impurity, since the use of sodium citrate alone allowed to avoid this drawback. Finally, the proposed mechanism was successfully applied to the design of a novel, easy and high purity procedure for the synthesis of the acetylated penicilloic acid, known related substance of piperacillin.

Shielding of Enzymes on the Surface of Graphene-Based Composite Cellular Foams Through Bioinspired Mineralization.

Immobilization of enzyme on the surface of graphene-based composite cellular foams (GCCFs) is commonly prone to acquire stable and ultrahigh loading of enzymes and fast transport of substrates during the catalytic process. In this chapter, we reported a method of preparing GCCFs through combination of redox assembly and biomimetic mineralization with in situ enzyme immobilization. Briefly, GCCFs were first prepared through redox assembly of graphene oxide (GO) nanosheets enabled by polyethyleneimine (PEI). The cationic PEI in the resultant reduced GO/PEI (rGO/PEI) cellular foams acted as the mineralization-inducing agent could catalyze the condensation of silicate to form silica (biomimetic silicification) on the reduced graphene oxide (rGO) surface, where enzyme (with penicillin G acylase as model enzyme) is in situ entrapped and shielded within the silica network. Enzymes could be stably resided on the surface of GCCFs without any leaching against a broad range of pH values (3.5-10.0). GCCFs show a three-dimensional (3D) porous structure, which facilitates the fast transfer of substrate and, thereby, leads to desirable catalytic activity. Combined with the monolithic feature, GCCFs exhibit ease of recyclability and superior thermal/recycling stabilities during the catalytic synthesis of 6-aminopenicillanic acid (6-APA, an important pharmaceutical intermediate) compared to free enzyme and enzyme adsorbed on rGO/PEI cellular foams.

A gratuitous ß-Lactamase inducer uncovers hidden active site dynamics of the Staphylococcus aureus BlaR1 sensor domain.

Increasing evidence shows that active sites of proteins have non-trivial conformational dynamics. These dynamics include active site residues sampling different local conformations that allow for multiple, and possibly novel, inhibitor binding poses. Yet, active site dynamics garner only marginal attention in most inhibitor design efforts and exert little influence on synthesis strategies. This is partly because synthesis requires a level of atomic structural detail that is frequently missing in current characterizations of conformational dynamics. In particular, while the identity of the mobile protein residues may be clear, the specific conformations they sample remain obscure. Here, we show how an appropriate choice of ligand can significantly sharpen our abilities to describe the interconverting binding poses (conformations) of protein active sites. Specifically, we show how 2-(2'-carboxyphenyl)-benzoyl-6-aminopenicillanic acid (CBAP) exposes otherwise hidden dynamics of a protein active site that binds ß-lactam antibiotics. When CBAP acylates (binds) the active site serine of the ß-lactam sensor domain of BlaR1 (BlaRS), it shifts the time scale of the active site dynamics to the slow exchange regime. Slow exchange enables direct characterization of inter-converting protein and bound ligand conformations using NMR methods. These methods include chemical shift analysis, 2-d exchange spectroscopy, off-resonance ROESY of the bound ligand, and reduced spectral density mapping. The active site architecture of BlaRS is shared by many ß-lactamases of therapeutic interest, suggesting CBAP could expose functional motions in other ß-lactam binding proteins. More broadly, CBAP highlights the utility of identifying chemical probes common to structurally homologous proteins to better expose functional motions of active sites.

Mechanisms of proton relay and product release by Class A ß-lactamase at ultrahigh resolution.

The ß-lactam antibiotics inhibit penicillin-binding proteins (PBPs) by forming a stable, covalent, acyl-enzyme complex. During the evolution from PBPs to Class A ß-lactamases, the ß-lactamases acquired Glu166 to activate a catalytic water and cleave the acyl-enzyme bond. Here we present three product complex crystal structures of CTX-M-14 Class A ß-lactamase with a ruthenocene-conjugated penicillin-a 0.85 Å resolution structure of E166A mutant complexed with the penilloate product, a 1.30 Å resolution complex structure of the same mutant with the penicilloate product, and a 1.18 Å resolution complex structure of S70G mutant with a penicilloate product epimer-shedding light on the catalytic mechanisms and product inhibition of PBPs and Class A ß-lactamases. The E166A-penilloate complex captured the hydrogen bonding network following the protonation of the leaving group and, for the first time, unambiguously show that the ring nitrogen donates a proton to Ser130, which in turn donates a proton to Lys73. These observations indicate that in the absence of Glu166, the equivalent lysine would be neutral in PBPs and therefore capable of serving as the general base to activate the catalytic serine. Together with previous results, this structure suggests a common proton relay network shared by Class A ß-lactamases and PBPs, from the catalytic serine to the lysine, and ultimately to the ring nitrogen. Additionally, the E166A-penicilloate complex reveals previously unseen conformational changes of key catalytic residues during the release of the product, and is the first structure to capture the hydrolyzed product in the presence of an unmutated catalytic serine. DATABASE: Structural data are available in the PDB database under the accession numbers 5TOP, 5TOY, and 5VLE.

Chromatographic Methods for Quantitative Determination of Ampicillin, Dicloxacillin and Their Impurity 6-Aminopenicillanic Acid.

Two accurate, precise and sensitive high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC) methods were developed for assay of ampicillin (AMP) and dicloxacillin (DX) in the presence of their impurity, 6-aminopenicillanic acid (APA). Method (A) is HPTLC method; using silica gel HPTLC F254 plates as a stationary phase with methanol: chloroform: acetic acid (1:9: 0.2, by volume) as a developing system. All the bands were scanned at 220 nm. Method (B) is reversed phase- HPLC which depended on isocratic elution using C18 column and mobile phase consisting of acetonitrile: water (60:40, v/v), pH adjusted to 4 with orthophosphoric acid, at a flow rate of 1 mL min-1 and ultraviolet detection at 240 nm. The proposed methods were validated as per ICH guidelines and their linearity was evident in the ranges of 0.5-2 µg band-1, 0.4-2 µg band-1 and 0.2-1.2 µg band-1 for method (A) and 5-40 µg mL-1, 5-40 µg mL-1 and 2-16 µg mL-1 for method (B) for AMP, DX and APA, respectively. The proposed methods were successfully used for assay of AMP and DX in pure form and in pharmaceutical formulation where no interference from the excipients was detected.

Pharmaceutical Intermediate-Modified Gold Nanoparticles: Against Multidrug-Resistant Bacteria and Wound-Healing Application via an Electrospun Scaffold.

Remedying a multidrug-resistant (MDR) bacteria wound infection is a major challenge due to the inability of conventional antibiotics to treat such infections against MDR bacteria. Thus, developing wound dressings for wound care, particularly against MDR bacteria, is in huge demand. Here, we present a strategy in designing wound dressings: we use a small molecule (6-aminopenicillanic acid, APA)-coated gold nanoparticles (AuNPs) to inhibit MDR bacteria. We dope the AuNPs into electrospun fibers of poly(ε-caprolactone) (PCL)/gelatin to yield materials that guard against wound infection by MDR bacteria. We systematically evaluate the bactericidal activity of the AuNPs and wound-healing capability via the electrospun scaffold. APA-modified AuNPs (Au_APA) exhibit remarkable antibacterial activity even when confronted with MDR bacteria. Meanwhile, Au_APA has outstanding biocompatibility. Moreover, an in vivo bacteria-infected wound-healing experiment indicates that it has a striking ability to remedy a MDR bacteria wound infection. This wound scaffold can assist the wound care for bacterial infections.

99m Tc-tazobactam, a novel infection imaging agent: Radiosynthesis, quality control, biodistribution, and infection imaging studies.

The radiolabeled drug 99m Tc-tazobactam (99m Tc-TZB) was developed and assessed as an infection imaging agent in Pseudomonas aeruginosa and Salmonella enterica infection-induced animal models by comparing with inflammation induced animal models. Radiosynthesis of 99m Tc-TZB was assessed while changing ligand concentration, reducing agent concentration, pH, and reaction time while keeping radioactivity constant (~370 MBq). Percent labeling of the resulting complex was measured using paper chromatography and instant thin layer chromatography. The analysis of the 99m Tc-TZB complex indicated >95% labeling yield and electrophoresis revealed complex is neutral in nature. The biodistribution study also showed predominantly renal excretion; however liver, stomach, and intestine also showed slight tracer agent uptake. The agent significantly accumulated in Pseudomonas aeruginosa and Salmonella enterica infection induced tissues 3.58 ± 0.26% and 2.43 ± 0.42% respectively at 1 hour postinjection. The inflamed tissue failed to uptake noticeable activity at 1 hour time point. The scintigraphic study results were found in accordance with biodistribution pattern. On the basis of our preliminary results, the newly developed 99m Tc-TZB can be used to diagnose bacterial infection and to discriminate between infected and inflamed tissues.

Physical compatibility of ceftolozane-tazobactam with selected i.v. drugs during simulated Y-site administration.

PURPOSE: Results of a study to examine the physical compatibility of ceftolozane-tazobactam with common i.v. medications during simulated Y-site administration are presented. METHODS: Ceftolozane-tazobactam was reconstituted according to manufacturer recommendations and diluted with 0.9% sodium chloride or 5% dextrose to solutions containing 15 mg (10 mg of ceftolozane and 5 mg of tazobactam)/mL. All other i.v. drugs were prepared according to manufacturer recommendations and diluted with 0.9% sodium chloride or 5% dextrose to standard concentrations used clinically. Y-site administration was simulated by mixing ceftolozane-tazobactam solution with each tested drug solution at a 1:1 ratio. Solutions were inspected for visual, turbidity, and pH changes immediately and 15, 60, and 120 minutes after mixing. Incompatibility was defined as precipitation, color change, a positive Tyndall test, a change in turbidity of ≥0.5 nephelometric turbidity unit, or a change in pH of ≥1 unit during the 120-minute observation period. RESULTS: Of the 95 i.v. drugs tested, ceftolozane-tazobactam was compatible with 86 drugs in both diluents; notably, it was compatible with metronidazole in both solutions. No substantial pH changes were observed in any tested combination. Ceftolozane-tazobactam was incompatible with albumin, amphotericin B, caspofungin, cyclosporine, nicardipine, and phenytoin sodium due to turbidity changes and with propofol due to formation of an oily layer. CONCLUSION: Ceftolozane-tazobactam 15 mg (10 mg of ceftolozane and 5 mg of tazobactam)/mL was physically compatible with 86 of 95 study drugs tested in both 0.9% sodium chloride injection and 5% dextrose injection during simulated Y-site administration.

Subcritical water oxidation of 6-aminopenicillanic acid and cloxacillin using H2O2, K2S2O8, and O2.

This study was undertaken to investigate the degradation of 6-aminopenicillanic acid (6-APA) and cloxacillin in aqueous solution by the combined effect of subcritical water and the oxidising agents O2, H2O2, and K2S2O8. Nano ZnO was used as a solid catalyst. Response surface methodology was used to determine the optimum experimental parameters (temperature, treatment time, and concentration of oxidising agent). For 6-APA, the maximum organic carbon (TOC) removal rates of 83.54%, 81.11% and 42.42% were obtained using H2O2, K2S2O8, and O2, respectively. For cloxacillin, the maximum TOC removal rates of 67.69%, 76.02% and 14.45% were obtained using H2O2, K2S2O8, and O2, respectively. Additionally, the impact of nano and commercial ZnO on TOC removal rates was determined. Secondary ions produced during the degradation process-such as nitrite, nitrate, sulphate and chloride-were determined using ion chromatography.

Preparation and Biochemical Property of Penicillin G Amidase-Loaded Alginate and Alginate/Chitosan Hydrogel Beads.

BACKGROUND: Penicillin G amidase (PGA) (EC 3.5.1.11) are enzymes that are mainly involved in the synthesis of semi-synthetic }-lactam antibiotics. Soluble PGA is costly and lacks long term operational stability. We revised most of the patents related to Penicillin G amidase (PGA) immobilization in the section "Recent Patents on Immobilized Penicillin G Amidase". OBJECTIVE: The aim of this work was to study comparative biochemical property of PGA enzyme immobilized in two hydro-gel beads - Ca-alginate and alginate+chitosan hybrid and morphologically characterised by SEM. METHODS: PGA immobilized in alginate+chitosan hybrid bead shows high pH and thermal stability. Km, Vmax and Effectiveness factor (1) value of free PGA were 56.19 mg/ml, 1.786 U/ml and 1, respectively. These parameters for PGA immobilized alginate beads were 64.84 mg/ml, 0.781U/ml and 0.437, respectively and for PGA immobilized alginate+chitosan hybrid beads were 87.08 mg/ml, 0.622 U/ml and 0.348, respectively. RESULTS: Immobilized PGA on alginate+chitosan hybrid beads gave the highest thermal stability, reusability and storage stability than alginate immobilized PGA. CONCLUSION: The entrapment of PGA on alginate+chitosan hybrid beads revealed several advantages and could be used in 6APA (6- aminopenicillanic acid) production.

Epidemiology and Outcome of Ventilator-Associated Pneumonia in a Heterogeneous ICU Population in Qatar.

Objective. The purpose of this study is to collect data on epidemiology, microbiology, and outcome of VAP in our ICUs for reevaluation of the therapeutic strategies. Methods. This retrospective study involved all adult patients, 15 years of age or older, diagnosed with VAP in multidisciplinary ICUs at Hamad General Hospital between January 2010 and December 2012. Results. A total of 106 patients were enrolled. The mean incidence of VAP was 5.0 per 1000 ventilator-days. It was predominant among younger age group (<60 years), male patients (80.2%), and trauma ICU admissions (49.0%). The most common comorbidity was hypertension (34%) and polytrauma (36.8%) was the most frequent admission diagnosis. 30-day mortality was 23.6% and it was significantly higher in ≥60 years age group, female gender, patients with diabetes mellitus, hypertension, chronic respiratory disease, ≥1 comorbidity, and poor functional status, smokers, medical and surgical ICU admissions, and patients with previous stay in medical/surgical wards, inappropriate empirical therapy, and admission diagnosis of respiratory failure. Gram-negative bacilli were the most frequent respiratory specimen isolates, Pseudomonas spp. being the most common. Majority of our Acinetobacter isolates were multidrug resistant. Conclusion. The incidence of VAP in our ICUs was low. Higher mortality rates were observed in certain subgroup of patients. Resistance to commonly used antimicrobials is likely to require reevaluation of the therapeutic strategies at our institution.

Degradation Kinetics and Mechanism of a ß-Lactam Antibiotic Intermediate, 6-Aminopenicillanic Acid, in a New Integrated Production Process.

In an effort to promote sustainability and to reduce manufacturing costs, the traditional production process for 6-aminopenicillanic acid (6-APA) has been modified to include less processing units. The objectives of this study are to investigate the degradation kinetics of 6-APA, to propose a reasonable degradation mechanism, and to optimize the manufacturing conditions within this new process. A series of degradation kinetic studies were conducted in the presence of impurities, as well as at various chemical and physical conditions. The concentrations of 6-APA were determined by high-performance liquid chromatography. An Arrhenius-type kinetic model was established to give a more accurate prediction on the degradation rates of 6-APA. A hydrolysis degradation mechanism is shown to be the major pathway for 6-APA. The degradation mechanisms and the kinetic models for 6-APA in the new system enable the design of a good manufacturing process with optimized parameters.

Visual and absorbance analyses of admixtures containing vancomycin and piperacillin-tazobactam at commonly used concentrations.

PURPOSE: The compatibility of vancomycin and piperacillin-tazobactam in concentrations typically used in extended-infusion dosing schemes was evaluated. METHODS: Piperacillin-tazobactam was reconstituted and diluted to concentrations of 33.75, 45, 50, 60, 67.5, 80, and 90 mg/mL. Vancomycin was diluted to concentrations of 4-8, 10, and 12 mg/mL. The resultant admixtures were visually observed after preparation against black and white backgrounds each hour between hours 1 through 4 and after 24 hours. Frozen products of each medication and brand-name Zosyn powder for reconstitution also were studied. Each combination of products and concentrations was tested for precipitation using simulated Y-site administration. Absorbance and microscopic analyses were performed to discern less perceptible incompatibilities in combinations that did not result in visual precipitation. Changes in absorbance were evaluated using two-way repeated-measures analysis of variance with post hoc Bonferroni corrections. RESULTS: No tested concentrations of piperacillin-tazobactam showed precipitations with vancomycin up to concentrations of 7 mg/mL. Piperacillin-tazobactam 80-90 mg/mL formed reversible precipitation with vancomycin 8 mg/mL. All tested concentrations of piperacillin-tazobactam formed a reversible precipitate with vancomycin 10 mg/mL. Irreversible precipitation was noted with all combinations of piperacillin-tazobactam and vancomycin 12 mg/mL. No significant changes in absorbance analyses were identified for all tested piperacillin-tazobactam concentrations and vancomycin 4-10 mg/mL compared with 0.9% sodium chloride injection (p > 0.05). Similar results were observed using frozen preparations and brand-name Zosyn. CONCLUSION: Visual, microscopic, and absorbance analyses showed no evidence of incompatibility when piperacillin-tazobactam 33.75-90 mg/mL was combined with vancomycin ≤7 mg/mL. Reversible and irreversible precipitates formed when piperacillin-tazobactam was combined with vancomycin ≥8 mg/mL.

Characterization of VCC-1, a Novel Ambler Class A Carbapenemase from Vibrio cholerae Isolated from Imported Retail Shrimp Sold in Canada.

One of the core goals of the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) is to monitor major meat commodities for antimicrobial resistance. Targeted studies with methodologies based on core surveillance protocols are used to examine other foods, e.g., seafood, for antimicrobial resistance to detect resistances of concern to public health. Here we report the discovery of a novel Ambler class A carbapenemase that was identified in a nontoxigenic strain of Vibrio cholerae (N14-02106) isolated from shrimp that was sold for human consumption in Canada. V. cholerae N14-02106 was resistant to penicillins, carbapenems, and monobactam antibiotics; however, PCR did not detect common ß-lactamases. Bioinformatic analysis of the whole-genome sequence of V. cholerae N14-02106 revealed on the large chromosome a novel carbapenemase (referred to here as VCC-1, for Vibrio cholerae carbapenemase 1) with sequence similarity to class A enzymes. Two copies of blaVCC-1 separated and flanked by ISVch9 (i.e., 3 copies of ISVch9) were found in an acquired 8.5-kb region inserted into a VrgG family protein gene. Cloned blaVCC-1 conferred a ß-lactam resistance profile similar to that in V. cholerae N14-02106 when it was transformed into a susceptible laboratory strain of Escherichia coli. Purified VCC-1 was found to hydrolyze penicillins, 1st-generation cephalosporins, aztreonam, and carbapenems, whereas 2nd- and 3rd-generation cephalosporins were poor substrates. Using nitrocefin as a reporter substrate, VCC-1 was moderately inhibited by clavulanic acid and tazobactam but not EDTA. In this report, we present the discovery of a novel class A carbapenemase from the food supply.

Novel Penicillin-Type Analogues Bearing a Variable Substituted 2-Azetidinone Ring at Position 6: Synthesis and Biological Evaluation.

The synthesis and the biological activity of novel semi-synthetic ß-lactam compounds containing an azetidinone moiety joined to the amino-nitrogen of the (+)-6-aminopenicillanic acid (6-APA) as new antibacterial agents is reported. The synthesized compounds were screened for their in vitro antimicrobial activity against a panel of Gram positive and Gram negative pathogens and environmental bacteria. Tested compounds displayed good antimicrobial activity against all tested Gram positive bacteria and for Staphylococcus aureus and Staphylococcus epidermidis antimicrobial activity resulted higher than that of the reference antibiotic. Additionally, in vitro cytotoxic screening was also carried out indicating that the compounds do not cause a cell vitality reduction effective at concentration next to and above those shown to be antimicrobial.

Ceftolozane-tazobactam: A new-generation cephalosporin.

PURPOSE: The chemistry, pharmacokinetic and pharmacodynamic properties, efficacy, and safety of the recently introduced combination antimicrobial agent ceftolozane-tazobactam are reviewed. SUMMARY: Ceftolozane-tazobactam (Zerbaxa, Cubist Pharmaceuticals) is a cephalosporin ß-lactam and ß-lactamase inhibitor marketed as a fixed-dose combination agent for the treatment of complicated urinary tract and intraabdominal infections. Its dosing and chemistry provide expansive antimicrobial coverage of gram-negative organisms, including Pseudomonas aeruginosa, and stable activity against many ß-lactamases, as well as coverage of most extended-spectrum ß-lactamase-producing organisms and some anaerobes. Ceftolozane-tazobactam is susceptible to hydrolysis by carbapenemase enzymes but is not affected by other resistance mechanisms such as efflux pumps and porin loss. Clinical trials demonstrated that combination treatment with ceftolozane-tazobactam plus metronidazole had efficacy comparable to that of levofloxacin in patients with complicated urinary tract infections, including pyelonephritis, and comparable to that of meropenem against complicated intraabdominal infections. A Phase III trial of ceftolozane-tazobactam versus meropenem for treatment of bacterial pneumonia, including ventilator-associated pneumonia, is underway. Adverse effects reported with ceftolozane-tazobactam use are comparable to those seen with other ß-lactams (e.g., hypersensitivity, nausea, diarrhea, headache). Initially, ceftolozane-tazobactam may be reserved for targeted therapy against multidrug-resistant pathogens. CONCLUSION: Ceftolozane-tazobactam is a new cephalosporin with enhanced activity against multidrug-resistant P. aeruginosa and other gram-negative pathogens.

Ceftolozane/Tazobactam: A Novel Cephalosporin/ß-Lactamase Inhibitor Combination.

Ceftolozane/tazobactam is a novel antipseudomonal ß-lactam/ß-lactamase inhibitor combination that is currently approved by the United States Food and Drug Administration for the treatment of complicated intraabdominal infections (cIAI) and complicated urinary tract infections (cUTI). It exhibits bactericidal properties through inhibition of bacterial cell wall biosynthesis, which is mediated through penicillin-binding proteins (PBPs). Ceftolozane is a potent PBP3 inhibitor and has a higher affinity for PBP1b compared with other ß-lactam agents. Ceftolozane/tazobactam differs from other cephalosporins due to its increased activity against some AmpC ß-lactamases and Pseudomonas aeruginosa. The addition of tazobactam provides enhanced activity against extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae and certain anaerobic organisms. Population pharmacokinetic studies for ceftolozane and ceftolozane/tazobactam are best described by a two-compartment model with zero-order input and linear elimination. Similar to other cephalosporins, the best pharmacodynamic property to predict efficacy for ceftolozane/tazobactam is a concentration that remains above the minimum inhibitory concentration (MIC) for 40-50% of the dosing interval. For Enterobacteriaceae and P. aeruginosa strains, the time above the MIC (T > MIC) needed to produce bactericidal activity was much less with ceftolozane than other cephalosporins, with T > MIC requirements of approximately 30%. For currently approved indications, the dose of ceftolozane/tazobactam is 1.5 g (ceftolozane 1 g/tazobactam 0.5 g) intravenously every 8 hours given as a 1-hour infusion. Ceftolozane has low plasma protein binding (20%) and is predominantly excreted unchanged in the urine (≥ 92%). Dosage adjustments are required for moderate-to-severe renal impairment and in patients receiving hemodialysis. Based on data from clinical trials, adverse effects due to ceftolozane/tazobactam do not differ considerably from other cephalosporins, with the most common being nausea, diarrhea, headache, and pyrexia. Ceftolozane/tazobactam is a promising new agent for the treatment of cIAI and cUTI, including those caused by multidrug-resistant gram-negative organisms.