Clinical and Microbiological Outcomes of Ceftazidime-Avibactam Treatment in Adults with Gram-Negative Bacteremia: A Subset Analysis from the Phase 3 Clinical Trial Program.

INTRODUCTION: This exploratory analysis assessed efficacy and safety outcomes in patients with Gram-negative bacteremia treated with ceftazidime-avibactam or comparator across five phase 3, randomized, controlled, multi-center trials in adults with complicated intra-abdominal infection (cIAI), complicated urinary tract infection (cUTI)/pyelonephritis, hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP). METHODS: In each trial, RECLAIM and RECLAIM 3 (cIAI; NCT01499290/NCT01726023), REPRISE (cIAI/cUTI; NCT01644643), RECAPTURE (cUTI; NCT01595438/NCT01599806), and REPROVE (HAP/VAP; NCT01808092), patients were randomized 1:1 to intravenous ceftazidime-avibactam (plus metronidazole for those with cIAI) or comparators (carbapenems in > 97% patients) for 5-21 days. Efficacy assessments included clinical and microbiological responses at the test-of-cure visit in the pooled Gram-negative extended microbiologically evaluable (GNeME) population (bacteremia subset). Safety outcomes were summarized for patients with positive bacterial blood culture(s) at baseline who received ≥ 1 dose of study treatment. RESULTS: The overall safety population included 4050 patients (ceftazidime-avibactam, n = 2024; comparator, n = 2026). The GNeME population (bacteremia subset) comprised 101 patients (ceftazidime-avibactam, n = 54; comparator, n = 47). Clinical cure rates (all indications combined) were 47/54 (87.0%) for ceftazidime-avibactam and 39/47 (83.0%) for comparators; favorable microbiological response rates were 43/54 (79.6%) and 32/47 (68.1%), respectively. Clinical and microbiological responses in the bacteremia subset were generally similar to those in the overall set. The pattern of adverse events in patients with bacteremia was similar between treatment groups and was consistent with the known safety profile of ceftazidime-avibactam. CONCLUSION: This analysis provides supportive evidence of the efficacy and safety of ceftazidime-avibactam in patients with Gram-negative bacteremia associated with cIAI, cUTI/pyelonephritis, or HAP/VAP.

Safety Profile of Ceftazidime-Avibactam: Pooled Data from the Adult Phase II and Phase III Clinical Trial Programme.

INTRODUCTION: Ceftazidime-avibactam combines the established anti-pseudomonal cephalosporin, ceftazidime, with the novel non-ß-lactam ß-lactamase inhibitor, avibactam. OBJECTIVES: The aim of this study was to evaluate the safety of ceftazidime-avibactam in adults using pooled data from two phase II (NCT00690378, NCT00752219) and five phase III (NCT01499290, NCT01726023, NCT01644643, NCT01808093 and NCT01595438/NCT01599806) clinical studies. METHODS: Safety data from seven multicentre, randomised, active-comparator studies were pooled by study group at the patient level for descriptive analyses, comprising patients with complicated urinary tract infection (cUTI), including pyelonephritis, complicated intra-abdominal infection (cIAI), or nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP), treated with ceftazidime-avibactam ± metronidazole or comparator. RESULTS: In total, 4050 patients (ceftazidime-avibactam ± metronidazole, n = 2024; comparator, n = 2026) were included in the pooled analysis. Adverse events (AEs) up to the last study visit occurred in 996 (49.2%) and 965 (47.6%) patients treated with ceftazidime-avibactam ± metronidazole and comparator, respectively. The most common AEs across treatment groups were diarrhoea, nausea, headache, vomiting and pyrexia. There were few discontinuations due to AEs (2.5% and 1.7% for ceftazidime-avibactam ± metronidazole and comparators, respectively). Overall rates of serious AEs were 8.7% for ceftazidime-avibactam ± metronidazole and 7.2% for comparators; respective rates of AEs with an outcome of death were 2.0% and 1.8%. AEs considered causally related to the study drug or procedures occurred in 10.7% and 9.6% of patients treated with ceftazidime-avibactam ± metronidazole and comparators; the most common drug-related AEs in both groups were diarrhoea, headache, nausea and increased alanine aminotransferase. No impact to the safety profile of ceftazidime-avibactam ± metronidazole was found with regard to intrinsic factors, such as age or renal function at baseline, or extrinsic factors, such as geographical origin. Potentially clinically significant changes in laboratory parameters were infrequent with no trends or safety concerns identified. CONCLUSION: The observed safety profile of ceftazidime-avibactam across infection types is consistent with the established safety profile of ceftazidime monotherapy and no new safety findings were identified. This analysis supports the use of ceftazidime-avibactam as a treatment option in adults with cUTI, cIAI and NP, including VAP.

In Vitro Activity of Ceftazidime-Avibactam against Isolates from Respiratory and Blood Specimens from Patients with Nosocomial Pneumonia, Including Ventilator-Associated Pneumonia, in a Phase 3 Clinical Trial.

Nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP), is increasingly associated with multidrug-resistant Gram-negative pathogens. This study describes the in vitro activity of ceftazidime-avibactam, ceftazidime, and relevant comparator agents against bacterial pathogens isolated from patients with NP, including VAP, enrolled in a ceftazidime-avibactam phase 3 trial. Gram-positive pathogens were included if coisolated with a Gram-negative pathogen. In vitro susceptibility was determined at a central laboratory using Clinical and Laboratory Standards Institute broth microdilution methods. Of 817 randomized patients, 457 (55.9%) had ≥1 Gram-negative bacterial pathogen(s) isolated at baseline, and 149 (18.2%) had ≥1 Gram-positive pathogen(s) coisolated. The most common isolated pathogens were Klebsiella pneumoniae (18.8%), Pseudomonas aeruginosa (15.8%), and Staphylococcus aureus (11.5%). Ceftazidime-avibactam was highly active in vitro against 370 isolates of Enterobacteriaceae, with 98.6% susceptible (MIC90, 0.5 µg/ml) compared with 73.2% susceptible for ceftazidime (MIC90, >64 µg/ml). The percent susceptibility values for ceftazidime-avibactam and ceftazidime against 129 P. aeruginosa isolates were 88.4% and 72.9% (MIC90 values of 16 µg/ml and 64 µg/ml), respectively. Among ceftazidime-nonsusceptible Gram-negative isolates, ceftazidime-avibactam percent susceptibility values were 94.9% for 99 Enterobacteriaceae and 60.0% for 35 P. aeruginosa MIC90 values for linezolid and vancomycin (permitted per protocol for Gram-positive coverage) were within their respective MIC susceptibility breakpoints against the Gram-positive pathogens isolated. This analysis demonstrates that ceftazidime-avibactam was active in vitro against the majority of Enterobacteriaceae and P. aeruginosa isolates from patients with NP, including VAP, in a phase 3 trial. (This study has been registered at ClinicalTrials.gov under identifier NCT01808092.).

Clinical activity of ceftazidime/avibactam against MDR Enterobacteriaceae and Pseudomonas aeruginosa: pooled data from the ceftazidime/avibactam Phase III clinical trial programme.

Objectives: This analysis evaluated the clinical activity of ceftazidime/avibactam against MDR Enterobacteriaceae and Pseudomonas aeruginosa isolates pooled from the adult Phase III clinical trials in patients with complicated intra-abdominal infection (cIAI), complicated urinary tract infection (cUTI) or nosocomial pneumonia (NP) including ventilator-associated pneumonia (VAP). Methods: Baseline isolates from five Phase III randomized controlled trials of ceftazidime/avibactam versus predominantly carbapenem comparators in patients with cIAI (RECLAIM 1 and 2; NCT01499290 and RECLAIM 3; NCT01726023), cUTI (RECAPTURE 1 and 2; NCT01595438 and NCT01599806), NP including VAP (REPROVE; NCT01808092) and cIAI or cUTI caused by ceftazidime-non-susceptible Gram-negative pathogens (REPRISE; NCT01644643) were tested for MDR status and susceptibility to ceftazidime/avibactam and carbapenem-based comparators using CLSI broth microdilution methodology. Microbiological and clinical responses for patients with ≥1 MDR Enterobacteriaceae or P. aeruginosa isolate were assessed at the test-of-cure (TOC) visit. Results: In the pooled microbiologically modified ITT population, 1051 patients with MDR Enterobacteriaceae and 95 patients with MDR P. aeruginosa isolates were identified. Favourable microbiological response rates at TOC for all MDR Enterobacteriaceae and MDR P. aeruginosa were 78.4% and 57.1%, respectively, for ceftazidime/avibactam and 71.6% and 53.8%, respectively, for comparators. The proportions of patients with ≥1 MDR isolate who were clinically cured at TOC were similar in the ceftazidime/avibactam (85.4%) and comparator (87.9%) arms. Conclusions: Ceftazidime/avibactam demonstrated similar clinical efficacy to predominantly carbapenem comparators against MDR Enterobacteriaceae and P. aeruginosa, and may be a suitable alternative to carbapenem-based therapies for cIAI, cUTI and NP/VAP caused by MDR Gram-negative pathogens.

Ceftazidime-avibactam versus meropenem in nosocomial pneumonia, including ventilator-associated pneumonia (REPROVE): a randomised, double-blind, phase 3 non-inferiority trial.

BACKGROUND: Nosocomial pneumonia is commonly associated with antimicrobial-resistant Gram-negative pathogens. We aimed to assess the efficacy and safety of ceftazidime-avibactam in patients with nosocomial pneumonia, including ventilator-associated pneumonia, compared with meropenem in a multinational, phase 3, double-blind, non-inferiority trial (REPROVE). METHODS: Adults with nosocomial pneumonia (including ventilator-associated pneumonia), enrolled at 136 centres in 23 countries, were randomly assigned (1:1) to 2000 mg ceftazidime and 500 mg avibactam (by 2 h intravenous infusion every 8 h) or 1000 mg meropenem (by 30-min intravenous infusion every 8 h) for 7-14 days; regimens were adjusted for renal function. Computer-generated randomisation codes were stratified by infection type and geographical region with a block size of four. Participants and investigators were masked to treatment assignment. The primary endpoint was clinical cure at the test-of-cure visit (21-25 days after randomisation). Non-inferiority was concluded if the lower limit of the two-sided 95% CI for the treatment difference was greater than -12·5% in the coprimary clinically modified intention-to-treat and clinically evaluable populations. This trial is registered with ClinicalTrials.gov (NCT01808092) and EudraCT (2012-004006-96). FINDINGS: Between April 13, 2013, and Dec 11, 2015, 879 patients were randomly assigned. 808 patients were included in the safety population, 726 were included in the clinically modified intention-to-treat population, and 527 were included in the clinically evaluable population. Predominant Gram-negative baseline pathogens in the microbiologically modified intention-to-treat population (n=355) were Klebsiella pneumoniae (37%) and Pseudomonas aeruginosa (30%); 28% were ceftazidime-non-susceptible. In the clinically modified intention-to-treat population, 245 (68·8%) of 356 patients in the ceftazidime-avibactam group were clinically cured, compared with 270 (73·0%) of 370 patients in the meropenem group (difference -4·2% [95% CI -10·8 to 2·5]). In the clinically evaluable population, 199 (77·4%) of 257 participants were clinically cured in the ceftazidime-avibactam group, compared with 211 (78·1%) of 270 in the meropenem group (difference -0·7% [95% CI -7·9 to 6·4]). Adverse events occurred in 302 (75%) of 405 patients in the ceftazidime-avibactam group versus 299 (74%) of 403 in the meropenem group (safety population), and were mostly mild or moderate in intensity and unrelated to study treatment. Serious adverse events occurred in 75 (19%) patients in the ceftazidime-avibactam group and 54 (13%) patients in the meropenem group. Four serious adverse events (all in the ceftazidime-avibactam group) were judged to be treatment related. INTERPRETATION: Ceftazidime-avibactam was non-inferior to meropenem in the treatment of nosocomial pneumonia. These results support a role for ceftazidime-avibactam as a potential alternative to carbapenems in patients with nosocomial pneumonia (including ventilator-associated pneumonia) caused by Gram-negative pathogens. FUNDING: AstraZeneca.

A randomised, double-blind, phase 3 study comparing the efficacy and safety of ceftazidime/avibactam plus metronidazole versus meropenem for complicated intra-abdominal infections in hospitalised adults in Asia.

Ceftazidime/avibactam comprises the broad-spectrum cephalosporin ceftazidime and the non-ß-lactam ß-lactamase inhibitor avibactam. This phase 3, randomised, double-blind study (NCT01726023) assessed the efficacy and safety of ceftazidime/avibactam plus metronidazole compared with meropenem in patients with complicated intra-abdominal infection (cIAI) in Asian countries. Subjects aged 18-90 years and hospitalised with cIAI requiring surgical intervention were randomised 1:1 to receive every 8 h either: ceftazidime/avibactam (2000/500 mg, 2-h infusion) followed by metronidazole (500 mg, 60-min infusion); or meropenem (1000 mg, 30-min infusion). Non-inferiority of ceftazidime/avibactam plus metronidazole to meropenem was concluded if the lower limit of the 95% confidence interval (CI) for the between-group difference in clinical cure rate was greater than -12.5% at the test-of-cure (TOC) visit (28-35 days after randomisation) in the clinically evaluable (CE) population. Safety was also evaluated. Of 441 subjects randomised, 432 received at least one dose of study medication (ceftazidime/avibactam plus metronidazole, n = 215; meropenem, n = 217). In the CE population at the TOC visit, non-inferiority of ceftazidime/avibactam plus metronidazole to meropenem was demonstrated, with clinical cure reported for 93.8% (166/177) and 94.0% (173/184) of subjects, respectively (between-group difference, -0.2, 95% CI -5.53 to 4.97). The clinical cure rate with ceftazidime/avibactam plus metronidazole was comparable in subjects with ceftazidime-non-susceptible and ceftazidime-susceptible isolates (95.7% vs. 92.1%, respectively). Adverse events were similar between the study groups. Ceftazidime/avibactam plus metronidazole was non-inferior to meropenem in the treatment of cIAIs in Asian populations and was effective against ceftazidime-non-susceptible pathogens. No new safety concerns were identified.

A randomized, double-blind, multicenter study of caspofungin versus liposomal amphotericin B for empiric antifungal therapy in pediatric patients with persistent fever and neutropenia.

BACKGROUND: Persistently febrile neutropenic children at risk for invasive fungal infections receive empiric antifungal therapy as a standard of care. However, little is known about the role of echinocandins and liposomal amphotericin B (L-AmB) for empiric antifungal therapy in pediatric patients. METHODS: Patients between the ages of 2 to 17 years with persistent fever and neutropenia were randomly assigned to receive caspofungin (70 mg/m loading dose on day 1, then 50 mg/m daily [maximum 70 mg/d]) or L-AmB (3 mg/kg daily) in a 2:1 ratio. Evaluation of safety was the primary objective of the study. Efficacy was also evaluated, with a successful outcome defined as fulfilling all components of a prespecified 5-part composite endpoint. Suspected invasive fungal infections were evaluated by an independent, treatment-blinded adjudication committee. RESULTS: Eighty-two patients received study therapy (caspofungin 56, L-AmB 26), and 81 were evaluated for efficacy (caspofungin 56; L-AmB 25). Outcomes for safety and efficacy endpoints were similar for both study arms. Adverse drug-related event rates [95% confidence interval] were similar between the caspofungin and L-AmB groups (clinical 48.2% [34.7-62.0] versus 46.2% [26.6-66.6]; laboratory 10.7% [4.0-21.9] versus 19.2% [6.6-39.4]). Serious drug-related adverse events occurred in 1 (1.8%) of caspofungin-treated patients and 3 (11.5%) of L-AmB-treated patients. Overall success rates [95% CI] were 46.4% [33.4-59.5] for caspofungin and 32.0% [13.7-50.3] for L-AmB. CONCLUSIONS: Caspofungin and L-AmB were comparable in tolerability, safety, and efficacy as empiric antifungal therapy for persistently febrile neutropenic pediatric patients.

Mutant APH(2'')-IIa enzymes with increased activity against amikacin and isepamicin.

Directed evolution by random PCR mutagenesis of the gene for the aminoglycoside 2''-IIa phosphotransferase generated R92H/D268N and N196D/D268N mutant enzymes, resulting in elevated levels of resistance to amikacin and isepamicin but not to other aminoglycoside antibiotics. Increases in the activities of the mutant phosphotransferases for isepamicin are the result of decreases in K(m) values, while improved catalytic efficiency for amikacin is the result of both a decrease in K(m) values and an increase in turnover of the antibiotic. Enzymes with R92H, D268N, and D268N single amino acid substitutions did not result in elevated MICs for aminoglycosides.

Safety experience with caspofungin in pediatric patients.

We analyzed the caspofungin safety experience in 5 clinical registration studies in 171 pediatric patients, 1 week to 17 years of age. Caspofungin was administered for 1 to 87 (mean 12.1) days. The most common drug-related adverse events were fever, increased AST, increased ALT, and rash; few events were serious or required treatment discontinuation. Caspofungin was well tolerated in this pediatric population.

A prospective, multicenter study of caspofungin for the treatment of documented Candida or Aspergillus infections in pediatric patients.

OBJECTIVE: We evaluated the safety, tolerability, and efficacy of caspofungin in pediatric patients with invasive aspergillosis, invasive candidiasis, or esophageal candidiasis. METHODS: This was a multicenter, prospective, open-label study in children 3 months to 17 years of age with proven or probable invasive aspergillosis, proven invasive candidiasis, or proven esophageal candidiasis. All of the patients received caspofungin 70 mg/m(2) on day 1, followed by 50 mg/m(2) per day (maximum: 70 mg/day), as primary or salvage monotherapy. Favorable response was defined as complete resolution of clinical findings and microbiologic (or radiographic/endoscopic) eradication (complete response) or significant improvement in these parameters (partial response). Efficacy was assessed at the end of caspofungin therapy in patients with a confirmed diagnosis who received >/=1 dose of caspofungin. The primary safety evaluation was the proportion of patients with clinical or laboratory drug-related adverse events. RESULTS: Of the 49 patients enrolled, 3 were <2 years of age, 30 were 2 to 11 years of age, and 16 were 12 to 17 years of age. Forty-eight patients had confirmed disease: invasive aspergillosis (10), invasive candidiasis (37), and esophageal candidiasis (1). Eight of 10 patients with invasive aspergillosis had pulmonary involvement; 34 of 37 patients with invasive candidiasis had candidemia. Caspofungin was given for 2 to 87 days. Success at end of therapy was achieved in 5 of 10 patients with invasive aspergillosis, 30 of 37 with invasive candidiasis, and 1 of 1 with esophageal candidiasis. One patient (invasive candidiasis) relapsed during the 28-day follow-up period. Drug-related clinical or laboratory adverse events occurred in 27% and 35% of patients, respectively. There were no serious drug-related adverse events or discontinuations of caspofungin because of toxicity. CONCLUSIONS: Caspofungin was generally well tolerated in pediatric patients aged 6 months through 17 years. Efficacy outcomes in patients with invasive aspergillosis or invasive candidiasis were consistent with previous adult studies in these indications.

Source of phosphate in the enzymic reaction as a point of distinction among aminoglycoside 2''-phosphotransferases.

Aminoglycoside 2''-phosphotransferases are clinically important enzymes that cause high levels of resistance to aminoglycoside antibiotics by the organisms that harbor them. These enzymes phosphorylate aminoglycosides, and the modified antibiotics show significant reduction in the binding ability to target the bacterial ribosome. This report presents a detailed characterization of the antibiotic resistance profile and the aminoglycoside and nucleotide triphosphate substrate profiles of four common aminoglycoside 2''-phosphotransferases widely distributed in clinically important Gram-positive microorganisms. Although the antibiotic resistance phenotypes exhibited by these enzymes are similar, their aminoglycoside and nucleotide triphosphate substrate profiles are distinctive. Contrary to the dogma that these enzymes use ATP as the source of phosphate in their reactions, two of the four aminoglycoside 2'-phosphotransferases utilize GTP as the phosphate donor. Of the other two enzymes, one exhibits preference for ATP, and the other can utilize either ATP or GTP as nucleotide triphosphate substrate. A new nomenclature for these enzymes is put forth that takes into account the differences among these enzymes based on their respective substrate preferences. These nucleotide triphosphate preferences should have ramifications for understanding of the evolution, selection, and dissemination of the genes for these important resistance enzymes.

In vitro susceptibilities of aerobic and facultatively anaerobic gram-negative bacilli isolated from patients with intra-abdominal infections worldwide: 2005 results from Study for Monitoring Antimicrobial Resistance Trends (SMART).

BACKGROUND: The Study for Monitoring Antimicrobial Resistance Trends (SMART) is examining aerobic and facultatively anaerobic gram-negative bacilli (GNB) isolated from intra-abdominal infections. This report summarizes the 2005 annual data. METHODS: During 2005, 76 medical centers in 31 countries in five regions collected intra-abdominal GNB for antimicrobial susceptibility testing using broth microdilution according to the Clinical and Laboratory Standards Institute guidelines. RESULTS: A total of 5,476 unique aerobic and facultatively anaerobic GNB were isolated. Enterobacteriaceae accounted for 86% (4,711) of the total isolates. Among the 12 antimicrobial agents tested, the carbapenems and amikacin were the most reliably active against the Enterobacteriaceae, whereas ampicillin/sulbactam most often was the least active. Escherichia coli was the species most commonly isolated, at 48% (2,654). Extended-spectrum beta-lactamases (ESBLs) were detected phenotypically in 12% (325/2,329) of E. coli and 18% (151/856) of Klebsiella spp. In general, ESBL producers demonstrated lower susceptibility to the majority of the antibiotics than the non-producers; however, ESBL producers usually were susceptible to the carbapenems tested. CONCLUSIONS: In 2005, antibiotic resistance continued to be a problem among GNB isolated from intra-abdominal infections, with the highest resistance rates observed in the Asia/Pacific region. Imipenem-cilastatin, ertapenem, and amikacin were the agents most consistently active in vitro against the Enterobacteriaceae isolated.

Pharmacokinetics and safety of caspofungin in neonates and infants less than 3 months of age.

Candida infections represent a major threat in neonatal intensive care units. This is the first prospective study to obtain caspofungin plasma levels and safety data for neonates and very young infants. Patients of <3 months of age receiving intravenous amphotericin B for documented or highly suspected candidiasis were enrolled in a single-dose (n = 6) or subsequent multiple-dose (n = 12) panel; all received caspofungin at 25 mg/m(2) once daily as a 1-hour infusion. Caspofungin plasma levels were measured by high-performance liquid chromatography and compared to historical data from adults. Patient chronological ages ranged from 1 to 11 weeks, and weights ranged from 0.68 to 3.8 kg. Gestational ages ranged from 24 to 41 weeks. Geometric mean (GM) peak (C(1 h)) and trough (C(24 h)) caspofungin levels were 8.2 and 1.8 microg/ml, respectively, on day 1, and 11.1 and 2.4 microg/ml, respectively, on day 4. GM ratios for C(1 h) and C(24 h) for neonates/infants relative to adults receiving caspofungin at 50 mg/day were 1.07 and 1.36, respectively, on day 1, and 1.18 and 1.21, respectively, on day 4. Clinical and laboratory adverse events occurred in 17 (94%) and 8 (44%) patients, respectively. Five patients (28%) had serious adverse events, none of which were considered drug related. Caspofungin at 25 mg/m(2) once daily was well tolerated in this group of neonates/infants of <3 months of age and appears to provide relatively similar plasma exposure to that obtained in adults receiving 50 mg/day. However, the small number of patients studied precludes any definitive recommendations about caspofungin dosing for this group comprising a broad range of ages and weights.

Aminoglycoside 2''-phosphotransferase type IIIa from Enterococcus.

Aminoglycoside 2''-phosphotransferases mediate high level resistance to aminoglycoside antibiotics in Gram-positive microorganisms, thus posing a serious threat to the treatment of serious enterococcal infections. This work reports on cloning, purification, and detailed mechanistic characterization of aminoglycoside 2''-phosphotransferase, known as type Ic enzyme. In an unexpected finding, the enzyme exhibits strong preference for guanosine triphosphate over adenosine triphosphate as the phosphate donor, a unique observation among all characterized aminoglycoside phosphotransferases. The enzyme phosphorylates only certain 4,6-disubstituted aminoglycosides exclusively at the 2''-hydroxyl with k(cat) values of 0.5-1.0 s(-1) and K(m) values in the nanomolar range for all substrates but kanamycin A. Based on this unique substrate profile, the enzyme is renamed aminoglycoside 2''-phosphotransferase type IIIa. Product and dead-end inhibition patterns indicated a random sequential Bi Bi mechanism. Both the solvent viscosity effect and determination of the rate constant for dissociation of guanosine triphosphate indicated that at pH 7.5 the release of guanosine triphosphate is rate-limiting. A computational model for the enzyme is presented that sheds light on the structural aspects of interest in this family of enzymes.

Bowel colonization with vancomycin-resistant enterococci after antimicrobial therapy for intra-abdominal infections: observations from 2 randomized comparative clinical trials of ertapenem therapy.

The impact of different antimicrobial regimens for intra-abdominal infections on the frequency of bowel colonization with vancomycin-resistant enterococci (VRE) was examined in 2 randomized open-label trials of intra-abdominal infection comparing piperacillin-tazobactam or ceftriaxone/metronidazole with ertapenem. In these short-term studies, overall rates of bowel colonization with VRE were generally comparable after treatment with piperacillin-tazobactam, ceftriaxone/metronidazole, or ertapenem.

Kinetic mechanism of enterococcal aminoglycoside phosphotransferase 2"-Ib.

The major mechanism of resistance to aminoglycosides in clinical bacterial isolates is the covalent modification of these antibiotics by enzymes produced by the bacteria. Aminoglycoside 2''-Ib phosphotransferase [APH(2'')-Ib] produces resistance to several clinically important aminoglycosides in both Gram-positive and Gram-negative bacteria. Nuclear magnetic resonance analysis of the product of kanamycin A phosphorylation revealed that modification occurs at the 2''-hydroxyl of the aminoglycoside. APH(2'')-Ib phosphorylates 4,6-disubstituted aminoglycosides with kcat/Km values of 10(5)-10(7) M-1 s-1, while 4,5-disubstituted antibiotics are not substrates for the enzyme. Initial velocity studies demonstrate that APH(2'')-Ib operates by a sequential mechanism. Product and dead-end inhibition patterns indicate that binding of aminoglycoside antibiotic and ATP occurs in a random manner. These data, together with the results of solvent isotope and viscosity effect studies, demonstrate that APH(2'')-Ib follows the random Bi-Bi kinetic mechanism and substrate binding and/or product release could limit the rate of reaction.

In vitro susceptibilities of aerobic and facultative Gram-negative bacilli isolated from patients with intra-abdominal infections in the Asia-Pacific region: 2004 results from SMART (Study for Monitoring Antimicrobial Resistance Trends).

In the 2004 Study for Monitoring Antimicrobial Resistance Trends (SMART), 14 centres from six countries in Asia-Pacific collected 1198 unique aerobic and facultative Gram-negative bacilli from intra-abdominal infections for susceptibility testing to 12 antimicrobial agents. Enterobacteriaceae comprised 82% of the total isolates. Escherichia coli was the most commonly isolated species (43%). Resistance rates were generally higher in Enterobacteriaceae isolated from Asian centres than those isolated from Oceania centres. There was little difference in susceptibility rates between community- and hospital-acquired Enterobacteriaceae for carbapenems. Extended-spectrum beta-lactamase (ESBL)-producers typically had a more resistant profile than non-ESBL-producers, but were usually susceptible to carbapenems. Of the antimicrobial agents tested, carbapenems were the most reliably active in vitro against Enterobacteriaceae recovered from patients in Asia-Pacific with intra-abdominal infections.

In vitro susceptibilities of aerobic and facultatively anaerobic Gram-negative bacilli isolated from patients with intra-abdominal infections worldwide: 2004 results from SMART (Study for Monitoring Antimicrobial Resistance Trends).

OBJECTIVES: SMART (Study for Monitoring Antimicrobial Resistance Trends) is an ongoing study to monitor worldwide antimicrobial resistance trends among aerobic and facultatively anaerobic Gram-negative bacilli (GNB) isolated from intra-abdominal infections. This 2004 report summarizes the most recently completed annual data from SMART. METHODS: During 2004, 81 medical centres from 28 countries in five global regions collected intra-abdominal GNB for antimicrobial susceptibility testing using broth microdilution according to the Clinical and Laboratory Standards Institute guidelines. RESULTS: A total of 6156 unique aerobic and facultatively anaerobic GNB were isolated from intra-abdominal infections. Enterobacteriaceae composed 86% of the total isolates. Among the 12 antimicrobial agents tested, the carbapenems and amikacin were the most consistently active against the Enterobacteriaceae. Escherichia coli was the most commonly isolated species (48%), and the susceptibility rate to the quinolones was lowest in Asia/Pacific and Latin America. Extended-spectrum beta-lactamases (ESBLs) were detected phenotypically in 10% of E. coli, 17% of Klebsiella spp. and 22% of Enterobacter spp. worldwide, representing a slight increase over the two previous years. ESBL producers typically had a more antibiotic-resistant profile than non-ESBL producers but were usually susceptible to the carbapenems. CONCLUSIONS: Antimicrobial resistance among GNB isolated from intra-abdominal infections continued to be a problem worldwide in 2004, with the highest rates of resistance overall in the Asia/Pacific region. The carbapenems and amikacin were the most consistently active agents in vitro against Enterobacteriaceae isolated from intra-abdominal infections worldwide.

In vitro susceptibilities of Escherichia coli isolated from patients with intra-abdominal infections worldwide in 2002-2004: results from SMART (Study for Monitoring Antimicrobial Resistance Trends).

BACKGROUND: Since 2002, the worldwide Study for Monitoring Antimicrobial Resistance Trends (SMART) has tracked resistance patterns among aerobic and facultative gram-negative bacilli isolated from patients with intra-abdominal infections. Escherichia coli has been by far the most frequently isolated species. METHODS: Antimicrobial susceptibilities for consecutive non-duplicate isolates of aerobic and facultative gram-negative bacilli recovered from intra-abdominal infections were determined by standard broth microdilution techniques. A subanalysis was performed for E. coli isolates from the first three years of the study. RESULTS: A total of 7,002 E. coli isolates were recovered, most commonly from the peritoneal cavity followed by the biliary tract. Susceptibility rates to the 12 antimicrobial agents tested differed among geographic regions, with isolates from Asia/Pacific generally having the highest resistance rates. Overall, extended-spectrum beta-lactamase (ESBL)-producers had a more antibiotic-resistant profile than non-ESBL-producers but usually were susceptible to the carbapenems and amikacin. Community-acquired E. coli strains comprised slightly more than one-half of the isolates and were susceptible to the agents tested more frequently than were hospital-acquired E. coli. CONCLUSIONS: The prevalence of antimicrobial resistance among E. coli isolated from intraabdominal infections is not inconsequential, especially in the Asia/Pacific region. The carbapenems and amikacin were consistently active in vitro against E. coli isolates worldwide, including ESBL-producers.

Acquisition of resistant bowel flora during a double-blind randomized clinical trial of ertapenem versus piperacillin-tazobactam therapy for intraabdominal infections.

Bowel colonization with resistant bacteria can develop in patients receiving broad-spectrum antimicrobial therapy. We compared the impact of two antimicrobial regimens often used to treat intraabdominal infections on susceptibility patterns of bowel flora at the end of therapy. In a double-blind clinical trial, adults with complicated intraabdominal infection requiring surgery were randomized to receive piperacillin-tazobactam (3.375 g every 6 h) or ertapenem (1 g once a day) for 4 to 14 days. Rectal swabs were obtained at baseline and at the end of study therapy to determine the acquisition rates of Enterobacteriaceae resistant to the study drug, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli or Klebsiella species, Pseudomonas aeruginosa resistant to imipenem or piperacillin-tazobactam, and vancomycin-resistant Enterococcus faecalis or Enterococcus faecium. Treated patients were assessable for the acquisition of resistant bacteria if appropriate specimens were obtained at both time points. Enterobacteriaceae resistant to the treatment received were acquired during study therapy by 8/122 assessable piperacillin-tazobactam recipients (6.6%) compared to 0/122 assessable ertapenem recipients (P = 0.007). Neither ESBL-producing E. coli or Klebsiella species nor P. aeruginosa resistant to piperacillin-tazobactam was isolated from patients in either treatment group. Imipenem-resistant P. aeruginosa was acquired by two of the ertapenem recipients (1.6%) versus zero of the piperacillin-tazobactam recipients (P = 0.50). Vancomycin-resistant enterococci were acquired during therapy by 8/125 assessable ertapenem recipients (6.4%) versus 2/123 assessable piperacillin-tazobactam recipients (1.6%; P = 0.10). In this study, the acquisition of resistant Enterobacteriaceae occurred significantly more often in patients treated with piperacillin-tazobactam than in those treated with ertapenem.