Treatment of severe pneumonia in hospitalized patients: results of a multicenter, randomized, double-blind trial comparing intravenous ciprofloxacin with imipenem-cilastatin. The Severe Pneumonia Study Group

What is the most effective antibiotic monotherapy for severe Pseudomonas aeruginosa infection? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVES

Severe infections caused by Pseudomonas aeruginosa are associated with significant morbidity and mortality, particularly in hospitalized and immunocompromised patients. Determining the optimal definitive monotherapy for these infections is critical. The main objective was to compile the evidence of subgroups of patients with Pseudomonas aeruginosa infection from randomized control trials (RCTs) evaluating different definite antipseudomonal monotherapies for severe P. aeruginosa infection.

METHODS

Systematic review and meta-analysis of RCTs that assessed monotherapy with an antipseudomonal drug versus another antipseudomonal for definite treatment, and reported on the subgroup of patients with P. aeruginosa infection. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, LILACS and the reference lists of included trials. Eligibility criteria included RCTs enrolling hospitalized adults (≥18 years) with microbiologically confirmed severe P. aeruginosa infections. Studies were excluded if they included >20% of patients receiving combination therapy or if patients had resistant P. aeruginosa strains at recruitment. Antipseudomonal drugs evaluated included cephalosporins, carbapenems, penicillins, quinolones and aztreonam. The primary outcome was 30-day mortality. Risk of bias was assessed using the Cochrane tool. Results were pooled using fixed-effects and random-effects models as appropriate. Relative risk (RR) and 95% CIs were calculated. Sensitivity analyses and subgroup analyses were performed when data were available.

RESULTS

A total of 76 RCTs and 1681 patients with pseudomonal infection were included. Due to the low number of studies which reported our outcomes of interest, all subgroup analyses were underpowered. No difference in all-cause mortality was found for any direct antibiotic comparison. Higher clinical failure rates of carbapenems versus piperacillin-tazobactam were observed for pneumonia in two RCTs (RR, 2.55; 95% CI, 1.29-5.03; I2 = 0%, n = 2), and higher microbiological failure rates with carbapenems versus other comparators (RR, 1.24; 95% CI, 1.02-1.51; I2 = 0%, n = 23). Patients treated with imipenem were more likely to develop resistance to the study drug versus comparators (RR, 2.33; 95% CI, 1.61-3.38; I2 = 0%, n = 7).

CONCLUSIONS

In this systematic review and meta-analysis of definite antipseudomonal monotherapy for P. aeruginosa infection, we found no evidence of clinical benefit differences among direct antibiotic comparisons, but all subgroup analyses were underpowered to detect significant differences.

[Epidemiology, diagnosis and treatment of adult patients with nosocomial pneumonia]

BACKGROUND

 Nosocomial pneumonia, encompassing hospital-acquired (HAP) and ventilator-associated pneumonia (VAP), remains a major cause of morbidity and mortality in hospitalized adults. In response to evolving pathogen profiles and emerging resistance patterns, this updated S3 guideline (AWMF Register No. 020-013) provides an evidence-based framework to enhance the diagnosis, risk stratification, and treatment of nosocomial pneumonia.

METHODS

 The guideline update was developed by a multidisciplinary panel representing key German professional societies. A systematic literature review was conducted with subsequent critical appraisal using the GRADE methodology. Structured consensus conferences and external reviews ensured that the recommendations were clinically relevant, methodologically sound, and aligned with current antimicrobial stewardship principles.

RESULTS

 For the management of nosocomial pneumonia patients should be divided in those with and without risk factors for multidrug-resistant pathogens and/or Pseudomonas aeruginosa. Bacterial multiplex-polymerase chain reaction (PCR) should not be used routinely. Bronchoscopic diagnosis is not considered superior to non-bronchoscopic sampling in terms of main outcomes. Combination antibiotic therapy is now reserved for patients in septic shock and high risk for multidrug-resistant pathogens, while select patients may be managed with monotherapy (e. g., meropenem). In clinically stabilized patients, antibiotic therapy should be de-escalated and focused, as well as duration shortened to 7-8 days. In critically ill patients, prolonged application of suitable beta-lactam antibiotics should be preferred. Patients on the intensive care unit (ICU) are at risk for invasive pulmonary aspergillosis (IPA). Diagnostics for Aspergillus should be performed with an antigen test from bronchial lavage fluid.

CONCLUSION

 This updated S3 guideline offers a comprehensive, multidisciplinary approach to the management of nosocomial pneumonia in adults. By integrating novel diagnostic modalities and refined therapeutic strategies, it aims to standardize care, improve patient outcomes, and enhance antimicrobial stewardship to curb the emergence of resistant pathogens.

Physicochemical characterization and nanochemical analysis of ciprofloxacin hydrophobic ion Pairs for enhanced encapsulation in PLGA nanoparticle

This study investigates the physicochemical transformation of ciprofloxacin (CIP) through hydrophobic ion pairing with five counter ions-sodium oleate, sodium laurate, sodium caprate, disodium pamoate, and sodium deoxycholate-to enhance compatibility with hydrophobic Poly (lactic-co-glycolic acid) (PLGA) nanoparticles. Complexation efficiencies (CE) reached up to 92.26 %, with ciprofloxacin pamoate (CIP-PAM) achieving over 90 % CE at a 1:0.5 M ratio. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses showed reduced crystallinity across all complexes, with CIP-PAM exhibiting an amorphous form. Optical photothermal infrared spectroscopy (O-PTIR) confirmed uniform complexation within particles, while CIP-PAM displayed a broad peak and weak intensity in the 900-1300 cm-1 region, supporting its amorphous nature. Log P values demonstrated increased hydrophobicity for all complexes, with ciprofloxacin oleate (CIP-OLE) showing a 93-fold increase (p < 0.001). In vitro dissociation patterns varied: CIP-OLE maintained steady release in DW (49.7 %) and PBS (32.3 %) over 48 h, whereas CIP-PAM exhibited strong stability in DW (25.2 %) and a contrasting 68.1 % release in PBS, highlighting solvent-dependent dissociation behaviors. PLGA nanoparticles prepared via S/O/W achieved particle sizes under 200 nm, with CIP-PAM showing the highest encapsulation efficiency (63.02 % vs 17.21 % (CIP)). These findings underscore the importance of counter ion selection to optimize CIP compatibility with hydrophobic carriers, providing a basis for improved drug loading of hydrophilic antibiotics.

Ciprofloxacin-Loaded Inhalable Formulations against Lower Respiratory Tract Infections: Challenges, Recent Advances, and Future Perspectives

Inhaled ciprofloxacin (CFX) has been investigated as a treatment for lower respiratory tract infections (LRTIs) associated with cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), and bronchiectasis. The challenges in CFX effectiveness for LRTI treatment include poor aqueous solubility and therapy resistance. CFX dry powder for inhalation (DPI) formulations were well-tolerated, showing a remarkable decline in overall bacterial burden compared to a placebo in bronchiectasis patients. Recent research using an inhalable powder combining Pseudomonas phage PEV20 with CFX exhibited a substantial reduction in bacterial density in mouse lungs infected with clinical P. aeruginosa strains and reduced inflammation. Currently, studies suggest that elevated biosynthesis of fatty acids could serve as a potential biomarker for detecting CFX resistance in LRTIs. Furthermore, inhaled CFX has successfully addressed various challenges associated with traditional CFX, including the incapacity to eliminate the pathogen, the recurrence of colonization, and the development of resistance. However, further exploration is needed to address three key unresolved issues: identifying the right patient group, determining the optimal treatment duration, and accurately assessing the risk of antibiotic resistance, with additional multicenter randomized controlled trials suggested to tackle these challenges. Importantly, future investigations will focus on the effectiveness of CFX DPI in bronchiectasis and COPD, aiming to differentiate prognoses between these two conditions. This review underscores the importance of CFX inhalable formulations against LRTIs in preclinical and clinical sectors, their challenges, recent advancements, and future perspectives.

A Randomized Clinical Trial of Bayesian-Guided Beta-Lactam Infusion Strategy and Associated Bacterial Resistance and Clinical Outcomes in Patients With Severe Pneumonia

BACKGROUND

Antimicrobial resistance is a growing health concern worldwide. The objective of this study was to evaluate the effect of beta-lactam infusion on the emergence of bacterial resistance in patients with severe pneumonia in the intensive care unit.

METHODS

Adult intensive care patients receiving cefepime, meropenem, or piperacillin-tazobactam for severe pneumonia caused by Gram-negative bacteria were randomized to receive beta-lactams as an intermittent (30 minutes) or continuous (24 hours) infusion. Respiratory samples for culture and susceptibility testing, with minimum inhibitory concentrations (MIC), were collected once a week for up to 4 weeks. Beta-lactam plasma concentrations were measured and therapeutic drug monitoring was performed using Bayesian software as the standard of care.

RESULTS

The study was terminated early owing to slow enrollment. Thirty-five patients were enrolled in this study. Cefepime (n = 22) was the most commonly prescribed drug at randomization, followed by piperacillin (n = 8) and meropenem (n = 5). Nineteen patients were randomized into the continuous infusion arm and 16 into the intermittent infusion arm. Pseudomonas aeruginosa was the most common respiratory isolate (n = 19). Eighteen patients were included in the final analyses. No differences in bacterial resistance were observed between arms ( P = 0.67). No significant differences in superinfection ( P = 1), microbiological cure ( P = 0.85), clinical cure at day 7 ( P = 0.1), clinical cure at end of therapy ( P = 0.56), mortality ( P = 1), intensive care unit length of stay ( P = 0.37), or hospital length of stay ( P = 0.83) were observed. Achieving 100% ƒT > MIC ( P = 0.04) and ƒT > 4 × MIC ( P = 0.02) increased likelihood of clinical cure at day 7 of therapy.

CONCLUSIONS

No differences in the emergence of bacterial resistance or clinical outcomes were observed between intermittent and continuous infusions. Pharmacokinetic/pharmacodynamic target attainment may be associated with a clinical cure on day 7.

Fabrication, characterization, antimicrobial, toxicity and potential drug-delivery studies of PEGylated Sesamum indicum oil based nanoemulsion system

Background

The actively mutating properties of disease-causing pathogens and GI intolerance associated with certain antibiotics among other challenges necessitated the adoption of colloidal system for drug delivery. Nanoemulsions (Ciprofloxacin (Cp) -loaded and non-drug loaded) were prepared by spontaneous emulsification method, characterized using Cryo-TEM, FTIR and Zetasizer. Antimicrobial activities were carried out using agar well diffusion method on Klebsiella pneumoniae and Bacillus subtilis. The in-vitro and dermal toxicological assessment were carried out using adult Wistar rats.

Results

The Cryo-TEM micrographs showed spherical morphology while zetasizer results showed polydispersity index (PDI), mean droplet size and zeta potential (ZP) of 0.553, 124.3 ± 0.29 nm and − 15.3 mV respectively for non-drug loaded sesame oil-based emulsion (SOAB). While 0.295, 244.8 ± 0.33 nm and − 5.54 mV were recorded for Cp-loaded sesame oil-based emulsion (SOAB + Cp). The effective voltage charge of the emulsions was 147.4 V. FTIR results of Cp recorded O–H adsorption value of 3429 cm−1, while SOAB and SOAB + Cp showed superimposition at 3427.76 cm−1 showing no drug-excipient interactions. No skin irritation was observed after 14 days of skin corrosion assessment. No significant difference (p > 0.05) in body weight gain of both test and control animals, the treatment did not cause any observable alterations in blood-chemistry parameters and hematological indices. Photomicrographs of liver and heart shows an uncompromised histological architecture.

Conclusion

The finding of the study shows a skin friendly, nanosized, spherical negatively charged emulsion with no cardiotoxic, hematotoxic and hepatotoxic effects on Wistar rats, and as such appears promising as a safe vehicle for drug delivery.

Graphical Abstract

Pseudomonas aeruginosa Pneumonia: Evolution of Antimicrobial Resistance and Implications for Therapy

Pseudomonas aeruginosa (PA), a non-lactose-fermenting gram-negative bacillus, is a common cause of nosocomial infections in critically ill or debilitated patients, particularly ventilator-associated pneumonia (VAP), and infections of urinary tract, intra-abdominal, wounds, skin/soft tissue, and bloodstream. PA rarely affects healthy individuals, but may cause serious infections in patients with chronic structural lung disease, comorbidities, advanced age, impaired immune defenses, or with medical devices (e.g., urinary or intravascular catheters, foreign bodies). Treatment of pseudomonal infections is difficult, as PA is intrinsically resistant to multiple antimicrobials, and may acquire new resistance determinants even while on antimicrobial therapy. Mortality associated with pseudomonal VAP or bacteremias is high (> 35%) and optimal therapy is controversial. Over the past three decades, antimicrobial resistance (AMR) among PA has escalated globally, via dissemination of several international multidrug resistant "epidemic" clones. We discuss the importance of PA as a cause of pneumonia including health care-associated pneumonia, hospital-acquired pneumonia, VAP, the emergence of AMR to this pathogen, and approaches to therapy (both empirical and definitive).

Beta-Lactam vs. Fluoroquinolone Monotherapy for Pseudomonas aeruginosa Infection: A Systematic Review and Meta-Analysis

Introduction: Pseudomonas aeruginosa (PA) is a leading cause of healthcare-associated infections. A variety of antibiotic classes are used in the treatment of PA infections, including beta-lactams (BLs) and fluoroquinolones (FQs), given either together in combination therapy or alone in monotherapy. A systematic review and meta-analysis were performed to evaluate the therapeutic efficacy of BL agents versus FQ agents as active, definitive monotherapy in PA infections in adults. Methods: Comprehensive literature searches of the Medline and Scopus electronic databases, alongside hand searches of the Cochrane Database of Systematic Reviews, PubMed, and Google Scholar, were performed without a time restriction to identify studies published in English comparing BL and FQ agents given as monotherapy for PA infection in hospitalized adults for which mortality, bacteriological eradication, or clinical response was evaluated. One reviewer screened search results based on pre-defined selection criteria. Two reviewers independently assessed included studies for methodological quality using NIH assessment tools. Two fixed-effects meta-analyses were performed. Results: A total of 368 articles were screened, and six studies involving 338 total patients were included in the meta-analysis. Upon evaluation of methodological quality, two studies were rated good, three fair, and one poor. A meta-analysis of three studies demonstrates FQ monotherapy is associated with significantly improved survival compared to BL monotherapy for patients with PA bacteremia (OR, 3.65; 95% CI, 1.27–10.44; p = 0.02). A meta-analysis of three studies demonstrates FQ monotherapy is associated with equivalent bacteriological eradication compared to BL monotherapy for PA pneumonia or skin and soft tissue infection (RD, 0.07; 95% CI, −0.09 to 0.24; p = 0.39). Conclusion: The meta-analyses demonstrate FQ monotherapy significantly improves survival in PA bacteremia and is associated with similar rates of bacteriological eradication in pneumonia and skin and soft tissue infection caused by PA compared to BL monotherapy. However, more research is needed to make meaningful clinical recommendations.

Elevated Level of Imipenem-Resistant Gram-Negative Bacteria Isolated from Patients Attending Health Centers in North Gondar, Ethiopia

Background

The frequent identification of resistant bacteria in hospitals constantly presents antimicrobial therapy with a challenge. Imipenem, once considered an extremely powerful antibiotic against multidrug-resistant bacterial infections, is losing its effectiveness. Its use in empirical therapy with inadequate or nonexistent antimicrobial stewardship programs has further triggered bacterial resistance in low-income countries. Therefore, this study aimed at identifying imipenem-resistant Gram-negative bacteria from patients who were referred to health centers in North Gondar, Ethiopia.

Methods

A total of 153 sputum samples were used to isolate Gram-negative bacteria. The isolates, which were resistant to imipenem, were identified by standard biochemical tests and 16S rRNA sequencing. The Kirby-Bauer disk diffusion method was used to determine the sensitivity or resistance of the isolate to diverse antimicrobial agents.

Results

The study identified 79 imipenem-resistant bacterial isolates from eight genera with clinically relevant microorganisms, including Acinetobacter baumannii (20.77%), Klebsiella pneumoniae (19.48%), Pseudomonas aeruginosa (16.88%), and Serratia marcescens (14.28%). Overall, imipenem-resistant bacterial isolates were detected in 31 samples (20.26%). Additionally, a remarkably high level of resistance to most antibiotics was observed among isolates of Klebsiella pneumoniae and Acinetobacter baumannii. Gentamycin is the most active antibiotic against many of the isolates, while β-lactams appear to be less effective.

Conclusion

The study indicated that many Gram-negative bacteria were resistant to imipenem with parallel resistances to other antimicrobials. Hence, the prescription of imipenem within the region should be according to the antibiotic resistance profiles of the multi-drug resistant bacteria.

Carbapenem Antibiotics for the Empiric Treatment of Nosocomial Pneumonia: A Systematic Review and Meta-analysis

BACKGROUND

Previous meta-analyses suggested that treating hospital-acquired pneumonia (HAP), including ventilator-associated pneumonia (VAP), with empiric carbapenems was associated with lower mortality rates but higher rates of clinical failure for pseudomonal pneumonia. This study was an updated meta-analysis with sensitivity analyses and meta-regression to better understand the impact of carbapenem use in HAP/VAP.

RESEARCH QUESTION

What is the efficacy of carbapenems for empiric treatment of nosocomial pneumonia?

STUDY DESIGN AND METHODS

Databases were searched for randomized controlled studies evaluating empiric treatment for HAP and/or VAP, and studies were included comparing carbapenem- vs non-carbapenem-containing regimens. The primary outcome was all-cause mortality. Secondary outcomes included subgroup stratification and resistance development.

RESULTS

Of 9,140 references, 20 trials enrolling 5,489 patients met inclusion criteria. For mortality, carbapenem use had a risk ratio (RR) of 0.84 (95% CI, 0.74-0.96; P = .01). Stratified according to VAP proportion (< 33%, 33%-66%, and > 66%), RRs were 0.95 (95% CI, 0.77-1.17; P = .66), 0.78 (95% CI, 0.57-1.07; P = .13), and 0.81 (95% CI, 0.65-0.99; P = .04), respectively. Stratified according to severity, only groups with Acute Physiology and Chronic Health Evaluation II scores < 14 and between 14 and 17 showed mortality benefit (RRs of 0.64 [95% CI, 0.45-0.92; P = .01] and 0.77 [95% CI, 0.61-0.97; P = .03]). Meta-regression did not show an association between Pseudomonas prevalence and mortality (P = .44). Carbapenem use showed a trend toward developing resistance (RR, 1.40; 95% CI, 0.95-2.06; P = .09) and a 96% probability of resistance emergence.

INTERPRETATION

Carbapenem-based empiric regimens were associated with lower mortality rates compared with non-carbapenems, largely driven by trials of VAP. The mortality effect was not observed in trials with high disease severity and was not associated with Pseudomonas. The mortality difference was observed mainly in studies that used ceftazidime as control. There was a trend toward increasing resistance associated with carbapenems.

TRIAL REGISTRY

International Prospective Register of Systematic Reviews; No. CRD42018093602; URL: https://www.crd.york.ac.uk/prospero/.

Calculated parenteral initial treatment of bacterial infections: Respiratory infections

This is the fifth chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. It provides recommendations for the empirical and targeted antimicrobial treatment of lower respiratory tract infections, with a special emphasis on the treatment of acute exacerbation of COPD, community-acquired pneumonia and hospital-acquired pneumonia.

Levofloxacin-ceftazidime administration regimens combat Pseudomonas aeruginosa in the hollow-fiber infection model simulating abnormal renal function in critically ill patients

BACKGROUND

The purpose of this study was to investigate the bactericidal effects of levofloxacin and ceftazidime as both monotherapy and combination therapy, and to determine their effects on resistance suppression in patients with normal and abnormal (Ccr:16-20 mL/min) renal function. Common clinical administration regimens to provide reference values were further evaluated.

METHODS

The 7-d hollow-fiber infection model was used to inject the Pseudomonas aeruginosa standard strain (ATCC27853), which simulated common clinical administration regimens for patients with different renal function. Ten regimens were stratified into 2 categories based on renal function, and each category contained 3 monotherapy regimens and 2 combination therapy regimens. Total and resistant populations were quantified. Drug concentrations were determined by high-performance liquid chromatography (HPLC).

RESULTS

Monotherapy regimens resulted in about 0.5-log-CFU/mL bacterial kill in the total population at 6 or 8 h, whilst combination regimens resulted in 2- to 3-log-CFU/mL within 2 days. For levofloxacin monotherapy regimens in patients with normal renal function, resistance emergence was seen after 6 h, and was seen at 0 h in the ceftazidime monotherapy regimen, as well as in all regimens of patients with abnormal renal function. Although resistant subpopulation in combination regimens with abnormal renal function began to increase at 0 h, there was a definite downward trend after 8 h, while resistant population in the normal renal function group increased after 16 h.

CONCLUSIONS

Combination therapy had greater bactericidal efficacy and resistance inhibition compared with monotherapy. Studying combination regimens in randomized clinical trials is warranted.

Fluoroquinolones and Cardiovascular Risk: A Systematic Review, Meta-analysis and Network Meta-analysis

INTRODUCTION

Several fluoroquinolone antibiotics have been associated with cardiac adverse effects, leading to the withdrawal of some of these agents from the market. Cardiac side effects such as QT prolongation and torsades de pointes (TdP) have also been observed with fluoroquinolones currently on the market. In order to evaluate the cardiac risk of fluoroquinolones as a class, and the comparative risk for each individual drug, we conducted a systematic review, meta-analysis, and network meta-analysis.

METHODS

MEDLINE, EMBASE and the Cochrane Library were searched, up to March 2018, for randomized controlled trials, cohort studies, and case-control studies that investigated the association between fluoroquinolone treatment and the risk of cardiovascular events and cardiovascular mortality. We followed the PRISMA 2009 guidelines for data selection and extraction. Outcomes were pooled using random effects models. Direct and indirect comparisons in network meta-analysis were performed using frequentist methods.

RESULTS

Thirteen studies were included in our analyses. Fluoroquinolone use was associated with a statistically significant 85% increase in the risk for arrhythmia (odds ratio [OR] 1.85; 95% confidence interval [CI] 1.22-2.81) and 71% increase in the risk for cardiovascular mortality (OR 1.71; 95% CI 1.39-2.09). Moxifloxacin ranked most likely to have the highest risk for arrhythmia (P-score 0.99) and for cardiovascular mortality (P-score 0.95) by network meta-analysis.

CONCLUSIONS

Our findings show a significant association between fluoroquinolone use and an increased risk for arrhythmia and cardiovascular mortality. Moxifloxacin ranked with the highest probability for cardiovascular adverse events. Further study is required to determine how to reduce the risk for fluoroquinolone-associated cardiac toxicity.

Antibiotic selection in the treatment of acute invasive infections by Pseudomonas aeruginosa

Pseudomonas aeruginosa is characterized by an important intrinsic resistance to antibiotics and it possess an extraordinary ability to develop resistance to nearly all available antimicrobials through selection of mutations. We review some of the pharmacodynamic principles of antibiotics predicting efficacy, clinical experience with monotherapy and combination therapy, and principles for antibiotic treatment for empirical and directed treatment of P. aeruginosa invasive infections.

The Combination of Fosfomycin plus Meropenem Is Synergistic for Pseudomonas aeruginosa PAO1 in a Hollow-Fiber Infection Model

Treating high-density bacterial infections is a challenging clinical problem. We have a paucity of new agents that can address this problem. Pseudomonas aeruginosa is a particularly difficult pathogen to treat effectively because of the plethora of resistance mechanisms it carries. Fosfomycin is an agent discovered circa 40 years ago. Recently, it has been resurrected in the United States and studied for intravenous therapy. We hypothesized that, to maximize its utility, it would require combination chemotherapy when used in a clinical circumstance in high-bacterial-burden infections. We chose to examine the combination of meropenem plus fosfomycin. These agents were studied in the hollow-fiber infection model. We utilized a fully factorial study design, looking at 2 doses of meropenem alone (1 and 2 g 8-hourly) and two doses of fosfomycin alone (6 and 8 g 8-hourly), as well as all possible combinations plus a no-treatment control. We used a high-dimensional model of 5 inhomogeneous differential equations with 5 system outputs to analyze all data simultaneously. Combination therapy outperformed all monotherapy regimens, with all combinations driving >6 log₁₀ CFU/ml of bacterial killing. Combination therapy was able to counterselect resistance emergence (meropenem mutants being killed by the combination, as well as fosfomycin mutants being killed by the combination) in all regimens studied. The analysis demonstrated that the combination was significantly synergistic for bacterial cell killing and resistance suppression. Meropenem plus fosfomycin is a promising combination for therapy of high-burden Pseudomonas aeruginosa infections and requires further study.

Impact of carbapenem versus non-carbapenem treatment on the rates of superinfection: A meta-analysis of randomized controlled trials

Imipenem and meropenem are the recommended antipseudomonal carbapenems for nosocomial pneumonia per clinical practice guidelines. However, these agents have a relatively broader spectrum of activity than other antibiotics and need to be reserved. Carbapenems might cause higher rate of superinfection. The aim of this study was to compare the rate of superinfection between patients who received imipenem or meropenem versus those who received non-carbapenem treatment. PubMed, EMBASE, Cochrane Library databases and two trial registries were searched for relevant randomized controlled trials of hospitalized adults with pneumonia through February 24, 2017 without date or language restrictions. Risk ratios (RRs) with 95% confidence intervals (CIs) were estimated using random-effects models. The primary outcome was based on the intention-to-treat analysis while clinically evaluable patients were analyzed as secondary outcome. Eight RCTs were included in this meta-analysis. A statistically higher risk of superinfection with low heterogeneity (RR = 1.690, 95% CI 1.247-2.291, p = 0.001, I² = 0%) was associated with the two carbapenems compared to non-carbapenems. However, in comparison with non-carbapenems, superinfection with imipenem was significantly higher (RR = 1.694, 95% CI 1.234-2.325, p = 0.001, I² = 0%), while it was non-significant with meropenem (RR = 1.647, 95% CI 0.552-4.919, p = 0.371, I² = 0%). Superinfection was statistically higher in both double-blind and open-label studies and when carbapenems were compared to other antipseudomonal beta-lactams. This meta-analysis identified significantly higher superinfection with imipenem compared to non-carbapenems. The findings confirm the theory of higher superinfections with broader spectrum agents and provide additional support for reserving carbapenems for the treatment of infections caused by multidrug-resistant organisms.

Early Clinical Assessment of the Antimicrobial Activity of Finafloxacin Compared to Ciprofloxacin in Subsets of Microbiologically Characterized Isolates

Two phase II studies were performed with patients with uncomplicated urinary tract infections (uUTIs) and complicated urinary tract infections (cUTIs) or acute pyelonephritis (PN) to compare finafloxacin (300 mg twice a day [b.i.d.] orally for uUTI and 800 mg once a day [q.d.] intravenously [i.v.] for cUTI/PN) and ciprofloxacin (250 mg b.i.d. orally for uUTI and 400 mg b.i.d. i.v. for cUTI/PN). The early response to the study medications was evaluated in the microbiological intent-to-treat population (mITT) at day 3. A total of 21% of the isolates were ciprofloxacin resistant, 13.7% were primed pathogens carrying a mutation(s) potentially fostering fluoroquinolone resistance development, and 7.1% produced extended-spectrum β-lactamases (ESBLs). Finafloxacin demonstrated very good early clinical activity, with microbiological eradication rates of 88.6% (n = 132), compared to 78.7% (n = 61) for ciprofloxacin, and 69.6% (n = 23), compared to 35.7% (n = 14) for ciprofloxacin, in patients with ciprofloxacin-resistant uropathogens; 94.1% (n = 17), compared to 80.0% (n = 10) for ciprofloxacin, in patients infected with uropathogens primed for fluoroquinolone resistance uropathogens; and 91.7% (n = 11), compared to 0% for ciprofloxacin, in patients infected with ESBL producers. Finafloxacin demonstrated early and rapid activity against uropathogens, including fluoroquinolone-resistant and/or multiresistant pathogens or ESBL producers, while ciprofloxacin was less active against this subset of resistant pathogens. Susceptibilities of pathogens were quantitated by broth microdilution. Isolates were subgrouped according to their susceptibility patterns, in particular first-step quinolone resistance, quinolone resistance, and ESBL production. Eradication was defined as the elimination or reduction of study entry pathogens to <10³ CFU/ml in urine culture. (The studies described in this paper have been registered at ClinicalTrials.gov under identifiers NCT00722735 and NCT01928433.).

Clinical Outcomes of Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae Infections with Susceptibilities among Levofloxacin, Cefepime, and Carbapenems

PURPOSE

Highly resistant Gram-negative bacterial infections are associated with high mortality. Increasing resistance to standard therapy illustrates the need for alternatives when treating resistant organisms, especially extended-spectrum beta-lactamase- (ESBL-) producing Enterobacteriaceae.

METHODS

A retrospective chart review at a community hospital was performed. Patients who developed ESBL-producing infections were included. Patients less than eighteen years old, who were pregnant, or who were incarcerated were excluded. The primary outcome was hospital mortality. The secondary outcomes included intensive care unit (ICU) mortality, ICU length of stay, and hospital length of stay.

RESULTS

113 patients with ESBL-producing infections met the criteria for review. Hospital mortality: carbapenem (16.6%), cefepime (0%), and levofloxacin (15.3%) (p=0.253). ICU mortality: carbapenem (4.5%), cefepime, (0%), and levofloxacin (3.7%) (p=0.616). Mean ICU and hospital length of stay: carbapenem (9.8 ± 16, 12.1 ± 1 days), cefepime (7.8 ± 6, 11.1 ± 10.5 days), and levofloxacin (5.4 ± 4.1, 11.1 ± 10.4 days) (p=0.805, 0.685). No predictors were clearly found between the source of infection and mortality.

CONCLUSION

Cefepime or levofloxacin can be a potential alternative agent for infections with ESBL-producing Enterobacteriaceae, and larger clinical trials investigating these outcomes are warranted.

Antibiotic selection in the treatment of acute invasive infections by Pseudomonas aeruginosa: Guidelines by the Spanish Society of Chemotherapy

Pseudomonas aeruginosa is characterized by a notable intrinsic resistance to antibiotics, mainly mediated by the expression of inducible chromosomic β-lactamases and the production of constitutive or inducible efflux pumps. Apart from this intrinsic resistance, P. aeruginosa possess an extraordinary ability to develop resistance to nearly all available antimicrobials through selection of mutations. The progressive increase in resistance rates in P. aeruginosa has led to the emergence of strains which, based on their degree of resistance to common antibiotics, have been defined as multidrug resistant, extended-resistant and panresistant strains. These strains are increasingly disseminated worldwide, progressively complicating the treatment of P. aeruginosa infections. In this scenario, the objective of the present guidelines was to review and update published evidence for the treatment of patients with acute, invasive and severe infections caused by P. aeruginosa. To this end, mechanisms of intrinsic resistance, factors favoring development of resistance during antibiotic exposure, prevalence of resistance in Spain, classical and recently appeared new antibiotics active against P. aeruginosa, pharmacodynamic principles predicting efficacy, clinical experience with monotherapy and combination therapy, and principles for antibiotic treatment were reviewed to elaborate recommendations by the panel of experts for empirical and directed treatment of P. aeruginosa invasive infections.

Determining β-lactam exposure threshold to suppress resistance development in Gram-negative bacteria

Objectives

β-Lactams are commonly used for nosocomial infections and resistance to these agents among Gram-negative bacteria is increasing rapidly. Optimized dosing is expected to reduce the likelihood of resistance development during antimicrobial therapy, but the target for clinical dose adjustment is not well established. We examined the likelihood that various dosing exposures would suppress resistance development in an in vitro hollow-fibre infection model.

Methods

Two strains of Klebsiella pneumoniae and two strains of Pseudomonas aeruginosa (baseline inocula of ∼10 8  cfu/mL) were examined. Various dosing exposures of cefepime, ceftazidime and meropenem were simulated in the hollow-fibre infection model. Serial samples were obtained to ascertain the pharmacokinetic simulations and viable bacterial burden for up to 120 h. Drug concentrations were determined by a validated LC-MS/MS assay and the simulated exposures were expressed as C min /MIC ratios. Resistance development was detected by quantitative culture on drug-supplemented media plates (at 3× the corresponding baseline MIC). The C min /MIC breakpoint threshold to prevent bacterial regrowth was identified by classification and regression tree (CART) analysis.

Results

For all strains, the bacterial burden declined initially with the simulated exposures, but regrowth was observed in 9 out of 31 experiments. CART analysis revealed that a C min /MIC ratio ≥3.8 was significantly associated with regrowth prevention (100% versus 44%, P  = 0.001).

Conclusions

The development of β-lactam resistance during therapy could be suppressed by an optimized dosing exposure. Validation of the proposed target in a well-designed clinical study is warranted.

Predicting and preventing antimicrobial resistance utilizing pharmacodynamics: part II Gram-negative bacteria

INTRODUCTION

Antimicrobial resistance is a serious health threat worldwide. Better understanding of exposure targets that could suppress resistance amplification is necessary to guide the dosing of currently available agents as well as new therapies in the drug development process. Areas covered: This review will discuss studies that focused on predicting development of resistance using the pharmacokinetic-pharmacodynamic approach and how to design dosing regimens that can successfully suppress resistance emergence in Gram-negative bacteria. Expert opinion: Pharmacokinetic-pharmacodynamic targets could provide useful insights to guide antimicrobial dosing to prevent resistance emergence. Exposure targets required for resistance suppression are higher than those for efficacy and might not be clinically feasible. Combination therapy is a possible approach to improve the efficacy and minimize the resistance emergence for difficult-to-treat infections.

Meropenem by Continuous Versus Intermittent Infusion in Ventilator-Associated Pneumonia due to Gram-Negative Bacilli

Background:

It is known that β-lactam antibiotics exhibit time-dependent bactericidal activity. Several studies have found continuous infusion of meropenem more effective than intermittent infusion in maintaining constant serum concentrations in excess of the minimum inhibitory concentration. However, limited data exist on the clinical efficacy of meropenem administered by continuous infusion.

Objective:

To evaluate the clinical efficacy of continuous versus intermittent infusion of meropenem for the treatment of ventilator-associated pneumonia (VAP) due to gram-negative bacilli.

Methods:

A retrospective cohort study was conducted of patients with VAP caused by gram-negative bacilli who received initial empiric antibiotic therapy with meropenem. We analyzed 2 contemporary cohorts: one group received meropenem by continuous infusion (1 g over 360 min every 6 h), the other by intermittent infusion (1 g over 30 min every 6 h). The administration method was prescribed according to the physician's discretion. Patients received meropenem plus tobramycin for 14 days.

Results:

There were no significant differences between patient groups with regard to gender, age, APACHE-II at intensive care unit admission, diagnosis, microorganism responsible for VAP, or organ dysfunction severity at the time VAP was suspected. The group receiving medication by continuous infusion showed a greater clinical cure rate than the group treated with intermittent infusion (38 of 42, 90.47%, vs 28 of 47, 59.57%, respectively, with OR 6.44 [95% Cl 1.97 to 21.05; p < 0.001]).

Conclusions:

Meropenem administered by continuous infusion may have more clinical efficacy than intermittent infusion.

The growing threat of multidrug-resistant Gram-negative infections in patients with hematologic malignancies

Prolonged neutropenia and chemotherapy-induced mucositis render patients with hematologic malignancies highly vulnerable to Gram-negative bacteremia. Unfortunately, multidrug-resistant (MDR) Gram-negative bacteria are increasingly encountered globally, and current guidelines for empirical antibiotic coverage in these patients may not adequately treat these bacteria. This expansion of resistance, coupled with traditional culturing techniques requiring 2-4 days for bacterial identification and antimicrobial susceptibility results, have grave implications for these immunocompromised hosts. This review characterizes the epidemiology, risk factors, resistance mechanisms, recommended treatments, and outcomes of the MDR Gram-negative bacteria that commonly cause infections in patients with hematologic malignancies. We also examine the infection prevention strategies in hematology patients, such as infection control practices, antimicrobial stewardship, and targeted decolonization. Finally, we assess the strategies to improve outcomes of the infected patients, including gastrointestinal screening to guide empirical antibiotic therapy, new rapid diagnostic tools for expeditious identification of MDR pathogens, and use of two new antimicrobial agents, ceftolozane/tazobactam and ceftazidime/avibactam.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Role for phospholipid acyl chains and cholesterol in pulmonary infections and inflammation

Review on how complex mixtures of bioactive lipids and cholesterol may influence the pulmonary immune response during infection.

Bacterial and viral respiratory tract infections result in millions of deaths worldwide and are currently the leading cause of death from infection. Acute inflammation is an essential element of host defense against infection, but can be damaging to the host when left unchecked. Effective host defense requires multiple lipid mediators, which collectively have proinflammatory and/or proresolving effects on the lung. During pulmonary infections, phospholipid acyl chains and cholesterol can be chemically and enzymatically oxidized, as well as truncated and modified, producing complex mixtures of bioactive lipids. We review recent evidence that phospholipids and cholesterol and their derivatives regulate pulmonary innate and adaptive immunity during infection. We first highlight data that oxidized phospholipids generated in the lung during infection stimulate pattern recognition receptors, such as TLRs and scavenger receptors, thereby amplifying the pulmonary inflammatory response. Next, we discuss evidence that oxidation of endogenous pools of cholesterol during pulmonary infections produces oxysterols that also modify the function of both innate and adaptive immune cells. Last, we conclude with data that n‐3 polyunsaturated fatty acids, both in the form of phospholipid acyl chains and through enzymatic processing into endogenous proresolving lipid mediators, aid in the resolution of lung inflammation through distinct mechanisms. Unraveling the complex mechanisms of induction and function of distinct classes of bioactive lipids, both native and modified, may hold promise for developing new therapeutic strategies for improving pulmonary outcomes in response to infection.

Pooled population pharmacokinetic model of imipenem in plasma and the lung epithelial lining fluid

AIMS

Several clinical trials have confirmed the therapeutic benefit of imipenem for treatment of lung infections. There is however no knowledge of the penetration of imipenem into the lung epithelial lining fluid (ELF), the site of action relevant for lung infections. Furthermore, although the plasma pharmacokinetics (PK) of imipenem has been widely studied, most studies have been based on selected patient groups. The aim of this analysis was to characterize imipenem plasma PK across populations and to quantify imipenem ELF penetration.

METHODS

A population model for imipenem plasma PK was developed using data obtained from healthy volunteers, elderly subjects and subjects with renal impairment, in order to identify predictors for inter-individual variability (IIV) of imipenem PK. Subsequently, a clinical study which measured plasma and ELF concentrations of imipenem was included in order to quantify lung penetration.

RESULTS

A two compartmental model best described the plasma PK of imipenem. Creatinine clearance and body weight were included as subject characteristics predictive for IIV on clearance. Typical estimates for clearance, central and peripheral volume, and inter-compartmental clearance were 11.5 l h(-1) , 9.37 l, 6.41 l, 13.7 l h(-1) , respectively (relative standard error (RSE) <8%). The distribution of imipenem into ELF was described using a time-independent penetration coefficient of 0.44 (RSE 14%).

CONCLUSION

The identified lung penetration coefficient confirms the clinical relevance of imipenem for treatment of lung infections, while the population PK model provided insights into predictors of IIV for imipenem PK and may be of relevance to support dose optimization in various subject groups.

Development of Liposomal Ciprofloxacin to Treat Lung Infections

Except for management of Pseudomonas aeruginosa (PA) in cystic fibrosis, there are no approved inhaled antibiotic treatments for any other diseases or for infections from other pathogenic microorganisms such as tuberculosis, non-tuberculous mycobacteria, fungal infections or potential inhaled biowarfare agents including Francisella tularensis, Yersinia pestis and Coxiella burnetii (which cause pneumonic tularemia, plague and Q fever, respectively). Delivery of an antibiotic formulation via the inhalation route has the potential to provide high concentrations at the site of infection with reduced systemic exposure to limit side effects. A liposomal formulation may improve tolerability, increase compliance by reducing the dosing frequency, and enhance penetration of biofilms and treatment of intracellular infections. Two liposomal ciprofloxacin formulations (Lipoquin^® and Pulmaquin^®) that are in development by Aradigm Corporation are described here.

Suppression of Emergence of Resistance in Pathogenic Bacteria: Keeping Our Powder Dry, Part 2

We are in a crisis of bacterial resistance. For economic reasons, most pharmaceutical companies are abandoning antimicrobial discovery efforts, while, in health care itself, infection control and antibiotic stewardship programs have generally failed to prevent the spread of drug-resistant bacteria. At this point, what can be done? The first step has been taken. Governments and international bodies have declared there is a worldwide crisis in antibiotic drug resistance. As discovery efforts begin anew, what more can be done to protect newly developing agents and improve the use of new drugs to suppress resistance emergence? A neglected path has been the use of recent knowledge regarding antibiotic dosing as single agents and in combination to minimize resistance emergence, while also providing sufficient early bacterial kill. In this review, we look at the data for resistance suppression. Approaches include increasing the intensity of therapy to suppress resistant subpopulations; developing concepts of clinical breakpoints to include issues surrounding suppression of resistance; and paying attention to the duration of therapy, which is another important issue for resistance suppression. New understanding of optimizing combination therapy is of interest for difficult-to-treat pathogens like Pseudomonas aeruginosa, Acinetobacter spp., and multidrug-resistant (MDR) Enterobacteriaceae. These lessons need to be applied to our old drugs as well to preserve them and to be put into national and international antibiotic resistance strategies. As importantly, from a regulatory perspective, new chemical entities should have a resistance suppression plan at the time of regulatory review. In this way, we can make the best of our current situation and improve future prospects.

Ciprofloxacin-Loaded Keratin Hydrogels Prevent Pseudomonas aeruginosa Infection and Support Healing in a Porcine Full-Thickness Excisional Wound

Objective: Cutaneous wound infection can lead to impaired healing, multiple surgical procedures, and increased hospitalization time. We tested the effectiveness of keratin-based hydrogels (termed "keratose") loaded with ciprofloxacin to inhibit infection and support healing when topically administered to porcine excision wounds infected with Pseudomonas aeruginosa. Approach: Using a porcine excisional wound model, 10 mm full-thickness wounds were inoculated with 10⁶ colony-forming units of P. aeruginosa and treated on days 1 and 3 postinoculation with ciprofloxacin-loaded keratose hydrogels. Bacteria enumeration and wound healing were assessed on days 3, 7, and 11 postinjury. Results: Ciprofloxacin-loaded keratose hydrogels reduced the amount of P. aeruginosa in the wound bed by 99.9% compared with untreated wounds on days 3, 7, and 11 postinjury. Ciprofloxacin-loaded keratose hydrogels displayed decreased wound contraction and reepithelialization at day 7 postinjury. By day 11, wounds treated with ciprofloxacin-keratose hydrogels contained collagen-rich granulation tissue and myofibroblasts. Wounds treated with ciprofloxacin-loaded keratose hydrogels exhibited a transient increase in macrophages in the wound bed at day 7 postinjury that subsided by day 11. Innovation: Current therapies for wound infection include systemic antibiotics, which could lead to antibiotic resistance, and topical antimicrobial treatments, which require multiple applications and can delay healing. Here, we show that ciprofloxacin-loaded keratose hydrogels inhibit cutaneous wound infection without interfering with key aspects of the healing process including granulation tissue deposition and remodeling. Conclusions: Ciprofloxacin-loaded keratose hydrogels have the potential to serve as a point-of-injury antibiotic therapy that prevents infection and supports healing following cutaneous injury.

SeverePseudomonas aeruginosainfections

Pseudomonas aeruginosa infections are a frequent cause of morbidity and mortality in hospitalized patients. Treatment of these infections is complicated by the intrinsic and acquired resistance of this bacterium to many commonly used antimicrobial agents. In this article, Drs Hauser and Sriram argue that careful consideration of the mechanisms by which P. aeruginosa resists the activity of antimicrobial agents is essential for optimal treatment decisions. Although many aspects of treatment of severe P. aeruginosa infections remain controversial, the authors suggest specific treatment options for patients both before and after susceptibilities are known.

Loss of Antimicrobial Susceptibility in Aerobic Gram-Negative Bacilli Repeatedly Isolated From Patients in Intensive-Care Units

Objective:

To study the loss of antimicrobial susceptibility in repeat (same patient, same bacterial species, and same site) aerobic gram-negative bacilli (AGNB) isolated from individual patients during their stay in the intensive-care unit (ICU).

Setting:

A 792-bed, tertiary-care community hospital with a total of 107 adult, pediatric, and neonatal ICU beds. METHOD: An obser vational prospective study performed November 1992 through mid-July 1993.

Results:

Of 594 consecutive AGNB from 287 ICU patients, 117 isolates (20%) from 55 patients (19%) were repeat isolates, with the majority obtained from respiratory secretions (83%). Pseudomonas aeruginosa and Enterobacter species accounted for 61% of the isolates. Forty-two (36%) of the repeat isolates from 24 patients (44%) had >4-fold increase in minimum inhibitory concentration to at least one antibiotic and no longer were considered fully susceptible based on National Committee on Clinical Laboratory Standards criteria. Loss of antimicrobial susceptibility often developed within several (median 8) days and was associated only infrequently with simultaneous transition from colonization to infection in the individual patient. Use of certain β-lactam antibiotics was associated with increasing resistance to several other antibiotics in the same class. Concurrent use of β-lactams and aminoglycosides did not prevent loss of antimicrobial susceptibility to the former in repeat isolates.

Conclusion:

We conclude that loss of antimicrobial susceptibility in repeat AGNB isolated from ICU patients is common, usually is not associated with transition from colonization to infection, and often is associated with prior use of antibiotics. Minimizing antibiotic use in ICU patients should help reduce the risk of antimicrobial resistance in repeat AGNB isolates.

Nosocomial Infection Caused by Antibiotic-Resistant Organisms in the Intensive-Care Unit

Resistance to antimicrobial agents is an evolving process, driven by the selective pressure of heavy antibiotic use in individuals living in close proximity to others. The intensive care unit (ICU), crowded with debilitated patients who are receiving broad-spectrum antibiotics and being cared for by busy physicians, nurses, and technicians, serves as an ideal environment for the emergence of antibiotic resistance. Problem pathogens presently include multiply resistant gram-negative bacilli, methicillin-resistantStaphylococcus aureus, and the recently emerged vancomycin-resistant enterococci. The prevention of antimicrobial resistance in ICUs should focus on recognition via routine unit-based sur veillance, improved compliance with handwashing and barrier precautions, and antibiotic-use policies tailored to individual units within hospitals.

Recurrent Pseudomonas aeruginosa Infection in Chronic Lung Diseases: Relapse or Reinfection?

Background

Pseudomonas aeruginosa infection is particularly associated with progressive and ultimately chronic recurrent respiratory infections in chronic obstructive pulmonary disease, bronchiectasis, chronic destroyed lung disease, and cystic fibrosis. Its treatment is also very complex because of drug resistance and recurrence.

Methods

Forty eight cultures from 18 patients with recurrent P. aeruginosa pneumonia from 1998 to 2002 were included in this study. Two or more pairs of sputum cultures were performed during 2 or more different periods of recurrences. The comparison of strains was made according to the phenotypic patterns of antibiotic resistance and chromosomal fingerprinting by pulsed field gel electrophoresis (PFGE) using the genomic DNA of P. aeruginosa from the sputum culture.

Results

Phenotypic patterns of antibiotic resistance of P. aeruginosa were not correlated with their prior antibiotic exposition. Fifteen of 18 patients (83.3%) had recurrent P. aeruginosa pneumonia caused by the strains with same PFGE pattern.

Conclusion

These data suggest that the most of the recurrent P. aeruginosa infections in chronic lung disease occurred due to the relapse of prior infections. Further investigations should be performed for assessing the molecular mechanisms of the persistent colonization and for determining how to eradicate clonal persistence of P. aeruginosa.

Interaction of drug- and granulocyte-mediated killing of Pseudomonas aeruginosa in a murine pneumonia model

BACKGROUND

Killing of bacterial pathogens by granulocytes is a saturable process, as previously demonstrated. There is virtually no quantitative information about how granulocytes interact with antimicrobial chemotherapy to kill bacterial cells.

METHODS

We performed a dose-ranging study with the aminoglycoside plazomicin against Pseudomonas aeruginosa ATCC27853 in a granulocyte-replete murine pneumonia model. Plazomicin was administered in a humanized fashion (ie, administration of decrementing doses 5 times over 24 hours, mimicking a human daily administration profile). Pharmacokinetic profiling was performed in plasma and epithelial lining fluid. All samples were simultaneously analyzed with a population model. Mouse cohorts were treated for 24 hours; other cohorts treated with the same therapy were observed for another 24 hours after therapy cessation, allowing delineation of the therapeutic effect necessary to reduce the bacterial burden to a level below the half-saturation point.

RESULTS

The mean bacterial burden (±SD) at which granulocyte-mediated kill was half saturable was 2.45 × 10(6) ± 6.84 × 10(5) colony-forming units of bacteria per gram of tissue (CFU/g). Higher levels of plazomicin exposure reduced the bacterial burden to <5 log10 CFU/g, allowing granulocytes to kill an additional 1.0-1.5 log CFU/g over the subsequent 24 hours.

CONCLUSIONS

For patients with large bacterial burdens (eg, individuals with ventilator-requiring hospital-acquired pneumonia), it is imperative to kill ≥2 log10 CFU/g early after treatment initiation, to allow the granulocytes to contribute optimally to bacterial clearance.

The risk of seizures among the carbapenems: a meta-analysis

OBJECTIVES

A consensus exists among clinicians that imipenem/cilastatin is the most epileptogenic carbapenem, despite inconsistencies in the literature.

METHODS

We conducted a meta-analysis of all randomized controlled trials comparing carbapenems with each other or with non-carbapenem antibiotics to assess the risk of seizures for imipenem, meropenem, ertapenem and doripenem.

RESULTS

In the risk difference (RD) analysis, there were increased patients with seizure (2 per 1000 persons, 95% CI 0.001, 0.004) among recipients of carbapenems versus non-carbapenem antibiotics. This difference was largely attributed to imipenem as its use was associated with an additional 4 patients per 1000 with seizure (95% CI 0.002, 0.007) compared with non-carbapenem antibiotics, whereas none of the other carbapenems was associated with increased seizure. Similarly, in the pooled OR analysis, carbapenems were associated with a significant increase in the risk of seizures relative to non-carbapenem comparator antibiotics (OR 1.87, 95% CI 1.35, 2.59). The ORs for risk of seizures from imipenem, meropenem, ertapenem and doripenem compared with other antibiotics were 3.50 (95% CI 2.23, 5.49), 1.04 (95% CI 0.61, 1.77), 1.32 (95% CI 0.22, 7.74) and 0.44 (95% CI 0.13, 1.53), respectively. In studies directly comparing imipenem and meropenem, there was no difference in epileptogenicity in either RD or pooled OR analyses.

CONCLUSIONS

The absolute risk of seizures with carbapenems was low, albeit higher than with non-carbapenem antibiotics. Although imipenem was more epileptogenic than non-carbapenem antibiotics, there was no statistically significant difference in the imipenem versus meropenem head-to-head comparison.

Mechanisms of resistance to β-lactams in some common Gram-negative bacteria causing nosocomial infections

Gram-negative bacilli remain major killers of hospitalized patients and continue to evolve new resistance mechanisms. This review describes the mechanisms of resistance to beta-lactam antibiotics from those Gram-negative pathogens most often isolated from nosocomial infections.

Epileptogenic drugs: a systematic review

A wide range of substances, including drugs and illicit compounds, increase the risk of epileptic seizures. In this systematic review, the authors address the issue of the epileptogenic potential of marketed drugs, with the aims of providing criteria for the assessment of the cause-effect relationship between drug exposure and the risk of seizures; and to identify the compounds better fulfilling the requirements of an epileptogenic drug. Finding a correlation between drug exposure and occurrence of seizures does not necessarily establish a causal association. In light of the available evidence, even with these limitations, some conclusive remarks can be made on the epileptogenic potential of some active principles. Drugs with high epileptogenic potential include meperidine, sevoflurane, clozapine, phenothiazines and cyclosporine. Drugs with intermediate epileptogenic potential include propofol, maprotiline, tricyclic antidepressants and chlorambucil. Drugs with low epileptogenic potential include fluorquinolones, carbapenems, bupropion and iodinated contrast media. Drugs with minimal or inconclusive epileptogenic potential include interferon alpha.

APPROPRIATE AND TIMELY EMPIRICAL ANTIMICROBIAL TREATMENT OF ICU INFECTIONS - A ROLE FOR CARBAPENEMS

Treatment of serious nosocomial infections in the intensive care unit requires swift, effective, well-tolerated and appropriate therapy from the outset. The consequences of inappropriate treatment, i.e. the use of antibiotics that are ineffective against the causative pathogen(s) or delayed therapy, are numerous and impact negatively upon both the patient and the ever-dwindling healthcare resources in many hospitals. Although antibiotics have revolutionised the treatment of infections, their inappropriate and untimely use within the intensive care setting has led to the emergence and spread of antibiotic-resistant bacteria worldwide. Consequently, to ensure successful patient outcomes (reduce morbidity and mortality), it is important that any antibiotic treatment employed is right first time. Treatment of serious infections in the intensive care unit requires an empirical stratagem providing broad-spectrum coverage to a wide range of suspected or difficult-to-treat pathogens such as Pseudomonas aeruginosa. However, to prevent the errors of the past, this needs to be tailored as soon as the pathogen has been identified and resistance patterns are known. The carbapenems are potent parenteral antibiotics, with an ultra-broad spectrum of activity that encompasses multi-drug resistant and difficult-to-treat Gram-negative bacteria. Clinical trial data supports the clinical effectiveness of these agents in patients with difficult to treat pathogens.

Evaluation of enrofloxacin use in koalas (Phascolarctos cinereus) via population pharmacokinetics and Monte Carlo simulation

Clinically normal koalas (n = 6) received a single dose of intravenous enrofloxacin (10 mg/kg). Serial plasma samples were collected over 24 h, and enrofloxacin concentrations were determined via high-performance liquid chromatography. Population pharmacokinetic modeling was performed in S-ADAPT. The probability of target attainment (PTA) was predicted via Monte Carlo simulations (MCS) using relevant target values (30-300) based on the unbound area under the curve over 24 h divided by the minimum inhibitory concentration (MIC) (fAUC0-24 /MIC), and published subcutaneous data were incorporated (Griffith et al., 2010). A two-compartment disposition model with allometrically scaled clearances (exponent: 0.75) and volumes of distribution (exponent: 1.0) adequately described the disposition of enrofloxacin. For 5.4 kg koalas (average weight), point estimates for total clearance (SE%) were 2.58 L/h (15%), central volume of distribution 0.249 L (14%), and peripheral volume 2.77 L (20%). MCS using a target fAUC0-24 /MIC of 40 predicted highest treatable MICs of 0.0625 mg/L for intravenous dosing and 0.0313 mg/L for subcutaneous dosing of 10 mg/kg enrofloxacin every 24 h. Thus, the frequently used dosage of 10 mg/kg enrofloxacin every 24 h subcutaneously may be appropriate against gram-positive bacteria with MICs ≤ 0.03 mg/L (PTA > 90%), but appears inadequate against gram-negative bacteria and Chlamydiae in koalas.

Worldwide challenges of multidrug-resistant bacteria in patients with hematologic malignancies

SUMMARY The emergence of infections due to multidrug-resistant (MDR) bacteria poses a major public health threat to all patients, but patients with hematologic malignancies are especially at risk. A common thread across all classes of bacteria is that increased reliance on and usage of broad-spectrum antibacterial agents, combined with the intrinsic ability of bacteria to develop and transmit resistance-conferring mutations, has led to the widespread dissemination of MDR organisms. In this article, we summarize the most worrisome MDR bacteria, assess their clinical impact on patients with hematologic malignancies and outline measures that are required to mitigate this impact.