In vitro evaluation of the activity of two doses of Levofloxacin alone and in combination with other agents against Pseudomonas aeruginosa

Antimicrobial susceptibility of multidrug-resistant Pseudomonas aeruginosa isolated from drinking water and hospitalized patients in Jordan

Pseudomonas aeruginosa (P. aeruginosa) is an important environmental, opportunistic and nosocomial pathogen with a significant threat to public health. The objectives of this study were to determine the in vitro antimicrobial susceptibility patterns of, and antibiotic drug combinations with synergistic effects against P. aeruginosa isolated from drinking water and hospitalized patients in Jordan. A total of 16 P. aeruginosa isolates were obtained from hospitalized patients and 15 were isolated from bottled drinking water were used in the study. Bacterial isolation and identification was performed using routine microbiological methods and confirmed using PCR technique targeting the 16S rDNA gene. The antimicrobial susceptibility patterns were determined by measuring the minimum inhibitory concentration (MIC) using the 2-fold microdilution method. Synergy interaction between various antimicrobials was determined using the checkerboard method and fractional inhibitory concentration index (FICI). The majority of water isolates were sensitive to gentamicin (93.3%), ticarcillin (86.7%) and ciprofloxacin, levofloxacin, amikacin, colistin, piperacillin, azlocillin, aztreonam, ceftazidime and imipenem (100% each). All water isolates (100%) were resistant to amoxicillin, oxytetracycline and doxycycline (93.3% and 86.7, respectively). For the clinical isolates, all (100%) were sensitive to ceftazidime, 81.3% were sensitive to aztreonam, while 62.5% were sensitive to ciprofloxacin, levofloxacin, gentamicin, amikacin, colistin, piperacillin, ticracillin, azlocillin, and imipenem. All clinical isolates (100%) were resistant to oxytetracycline, doxycycline and amoxicillin. Analysis of the checkerboard synergy assay of multi-drug resistant isolates (n=26) showed significant synergism (P ≤ 0.05) when ciprofloxacin or gentamicin were included in the combination. There were no significant differences in synergistic activity between ciprofloxacin and levofloxacin when combined with other antimicrobial agents of the beta-lactams or aminoglycosides classes. There were no significant differences in the synergistic activities between beta lactams - aminoglycoside and beta lactams - fluoroquinolone combinations. Results of this study indicate an alarming widespread presence of multidrug-resistant P. aeruginosa associated with chronic suppurative infections in hospitalized patients and apparently clean drinking water in Jordan. Treatment of clinical suppurative lesions must be based on culture and in vitro susceptibility testing using potent antimicrobial combinations to avoid emergence of resistant strains and to improve the clinical outcome of treated patients.

Systematic review and meta-analysis of in vitro efficacy of antibiotic combination therapy against carbapenem-resistant Gram-negative bacilli

The superiority of combination therapy for carbapenem-resistant Gram-negative bacilli (CR-GNB) infections remains controversial. In vitro models may predict the efficacy of antibiotic regimens against CR-GNB. A systematic review and meta-analysis was performed including pharmacokinetic/pharmacodynamic (PK/PD) and time-kill (TK) studies examining the in vitro efficacy of antibiotic combinations against CR-GNB [PROSPERO registration no. CRD42019128104]. The primary outcome was in vitro synergy based on the effect size (ES): high, ES ≥ 0.75, moderate, 0.35 < ES < 0.75; low, ES ≤ 0.35; and absent, ES = 0). A network meta-analysis assessed the bactericidal effect and re-growth rate (secondary outcomes). An adapted version of the ToxRTool was used for risk-of-bias assessment. Over 180 combination regimens from 136 studies were included. The most frequently analysed classes were polymyxins and carbapenems. Limited data were available for ceftazidime/avibactam, ceftolozane/tazobactam and imipenem/relebactam. High or moderate synergism was shown for polymyxin/rifampicin against Acinetobacter baumannii [ES = 0.91, 95% confidence interval (CI) 0.44-1.00], polymyxin/fosfomycin against Klebsiella pneumoniae (ES = 1.00, 95% CI 0.66-1.00) and imipenem/amikacin against Pseudomonas aeruginosa (ES = 1.00, 95% CI 0.21-1.00). Compared with monotherapy, increased bactericidal activity and lower re-growth rates were reported for colistin/fosfomycin and polymyxin/rifampicin in K. pneumoniae and for imipenem/amikacin or imipenem/tobramycin against P. aeruginosa. High quality was documented for 65% and 53% of PK/PD and TK studies, respectively. Well-designed in vitro studies should be encouraged to guide the selection of combination therapies in clinical trials and to improve the armamentarium against carbapenem-resistant bacteria.

Pharmacokinetic Alterations of Antimicrobials in the Critically Ill

Critical illness is accompanied by multiple physiologic alterations that affect the pharmacokinetics of antimicrobials. Although the pharmacokinetics of a number of antimicrobials have been studied in critically ill individuals, an understanding of the physiological alterations in critical illness and general pharmacokinetic principles of antimicrobials is imperative for appropriate selection, dosing, and prediction of toxicity.

Levofloxacin and Tobramycin for Severe Bacterial Keratouveitis

PURPOSE

To report on clinical features and outcome of severe bacterial keratouveitis.

METHODS

Twenty patients with severe bacterial keratouveitis treated with topical tobramycin and levofloxacin and oral levofloxacin were included. Main outcome measures were ulcers location, bacterial isolates, risk factors, visual prognosis.

RESULTS

Centrally located ulcer/abscess was present in 65% of patients. Contact lens (CL) wear was the most common risk factor (70%). Bacterial isolates were observed in 58% of patients, none resistant to tobramycin and levofloxacin. Pseudomonas aeruginosa was found in 47% of positive cases and in 64% of CL wearers. After therapy, the mean visual acuity improved significantly (p < 0.0001), particularly in contact lens wearers (p = 0.04) and in patients younger than 60 years old (p < 0.001).

CONCLUSIONS

Pseudomonas aeruginosa is the most frequent cause of bacterial keratouveitis and CL wear the most common risk factor. Topical tobramycin and levofloxacin and oral levofloxacin are effective in the treatment of bacterial keratouveitis.

Preventive antibiotics in pediatric patients with acute myeloid leukemia (AML)

BACKGROUND

Treatment of acute myeloid leukemia (AML) comes with a significant risk of life-threatening infection during periods of prolonged severe neutropenia. We studied the impact of preventive intravenous (IV) antibiotic administration at onset of absolute neutropenia on the incidence and outcome of life-threatening infections during treatment of childhood AML.

PROCEDURES

This is a retrospective study on pediatric patients (aged 0-18 years) consecutively diagnosed with de novo AML and treated at a single institution from April 2005 through February 2013. Patients were treated on the Children's Oncology Group (COG) AAML0531 protocol or with a modified United Kingdom Medical Research Council (UK MRC) AML 10 regimen. Pertinent data were extracted from hard copy or electronic chart review.

RESULTS

A total of 76 chemotherapy phases were analyzed from 29 patients. In each phase reported, preventive antibiotics were initiated when the daily absolute neutrophil count was <500 cells/mcl, before onset of fever. Seven episodes of bacteremia were documented with predominantly coagulase-negative staphylococci and viridans group streptococci. One infection-related death occurred, attributed to progressive respiratory failure occurring months after documented candidal pneumonia.

CONCLUSIONS

Initiation of preventive antibiotics at the onset of absolute neutropenia was associated with no mortality from bacteremia. This preventive approach appears feasible and safe.

Application of Savitzky-Golay differentiation filters and Fourier functions to simultaneous determination of cefepime and the co-administered drug, levofloxacin, in spiked human plasma

The present work is concerned with simultaneous determination of cefepime (CEF) and the co-administered drug, levofloxacin (LEV), in spiked human plasma by applying a new approach, Savitzky-Golay differentiation filters, and combined trigonometric Fourier functions to their ratio spectra. The different parameters associated with the calculation of Savitzky-Golay and Fourier coefficients were optimized. The proposed methods were validated and applied for determination of the two drugs in laboratory prepared mixtures and spiked human plasma. The results were statistically compared with reported HPLC methods and were found accurate and precise.

Treatment ofPseudomonas aeruginosainfection in critically ill patients

Critically ill patients are on the increase in the present clinical setting. Aging of our population and increasingly aggressive medical and therapeutic interventions, including implanted foreign bodies, organ transplantation and advances in the chemotherapy of malignant diseases, have created a cohort of particularly vulnerable patients. Pseudomonas aeruginosa is one of the leading gram-negative organisms associated with nosocomial infections. This organism is frequently feared because it causes severe hospital-acquired infections, especially in immunocompromised hosts, and is often antibiotic resistant, complicating the choice of therapy. The epidemiology, microbiology, mechanisms of resistance and currently available and future treatment options for the most relevant infections caused by P. aeruginosa are reviewed.

Clinical practice guideline for the use of antimicrobial agents in neutropenic patients with cancer: 2010 update by the infectious diseases society of america

This document updates and expands the initial Infectious Diseases Society of America (IDSA) Fever and Neutropenia Guideline that was published in 1997 and first updated in 2002. It is intended as a guide for the use of antimicrobial agents in managing patients with cancer who experience chemotherapy-induced fever and neutropenia. Recent advances in antimicrobial drug development and technology, clinical trial results, and extensive clinical experience have informed the approaches and recommendations herein. Because the previous iteration of this guideline in 2002, we have a developed a clearer definition of which populations of patients with cancer may benefit most from antibiotic, antifungal, and antiviral prophylaxis. Furthermore, categorizing neutropenic patients as being at high risk or low risk for infection according to presenting signs and symptoms, underlying cancer, type of therapy, and medical comorbidities has become essential to the treatment algorithm. Risk stratification is a recommended starting point for managing patients with fever and neutropenia. In addition, earlier detection of invasive fungal infections has led to debate regarding optimal use of empirical or preemptive antifungal therapy, although algorithms are still evolving. What has not changed is the indication for immediate empirical antibiotic therapy. It remains true that all patients who present with fever and neutropenia should be treated swiftly and broadly with antibiotics to treat both gram-positive and gram-negative pathogens. Finally, we note that all Panel members are from institutions in the United States or Canada; thus, these guidelines were developed in the context of North American practices. Some recommendations may not be as applicable outside of North America, in areas where differences in available antibiotics, in the predominant pathogens, and/or in health care-associated economic conditions exist. Regardless of venue, clinical vigilance and immediate treatment are the universal keys to managing neutropenic patients with fever and/or infection.

Executive Summary: Clinical Practice Guideline for the Use of Antimicrobial Agents in Neutropenic Patients with Cancer: 2010 Update by the Infectious Diseases Society of America

This document updates and expands the initial Infectious Diseases Society of America (IDSA) Fever and Neutropenia Guideline that was published in 1997 and first updated in 2002. It is intended as a guide for the use of antimicrobial agents in managing patients with cancer who experience chemotherapy-induced fever and neutropenia.

Recent advances in antimicrobial drug development and technology, clinical trial results, and extensive clinical experience have informed the approaches and recommendations herein. Because the previous iteration of this guideline in 2002, we have a developed a clearer definition of which populations of patients with cancer may benefit most from antibiotic, antifungal, and antiviral prophylaxis. Furthermore, categorizing neutropenic patients as being at high risk or low risk for infection according to presenting signs and symptoms, underlying cancer, type of therapy, and medical comorbidities has become essential to the treatment algorithm. Risk stratification is a recommended starting point for managing patients with fever and neutropenia. In addition, earlier detection of invasive fungal infections has led to debate regarding optimal use of empirical or preemptive antifungal therapy, although algorithms are still evolving.

What has not changed is the indication for immediate empirical antibiotic therapy. It remains true that all patients who present with fever and neutropenia should be treated swiftly and broadly with antibiotics to treat both gram-positive and gram-negative pathogens.

Finally, we note that all Panel members are from institutions in the United States or Canada; thus, these guidelines were developed in the context of North American practices. Some recommendations may not be as applicable outside of North America, in areas where differences in available antibiotics, in the predominant pathogens, and/or in health care–associated economic conditions exist. Regardless of venue, clinical vigilance and immediate treatment are the universal keys to managing neutropenic patients with fever and/or infection.

In Vitro Synergy of Levofloxacin Plus Piperacillin/Tazobactam against Pseudomonas aeruginosa

In vitro synergy testing using levofloxacin (LVX) plus piperacillin/tazobactam (TZP) was performed by Etest and time-kill assay (TKA) for 31 unique fluoroquinolone-resistant Pseudomonas aeruginosa isolates. The Etest method showed synergy for 9/31 (29%) of isolates, while TKA showed synergy with 14/31 (45%) of isolates. When comparing the Etest method and TKA, concordant results for synergy, antagonism, and indifference were obtained for 24/31 (77%) of the isolates tested.

In vitro synergism of beta-lactams with ciprofloxacin and moxifloxacin against genetically distinct multidrug-resistant isolates of Pseudomonas aeruginosa

In vitro combinations of beta-lactams with fluoroquinolones against multidrug-resistant (MDR) Pseudomonas aeruginosa were tested. From a total of 200 isolates, 24 genetically distinct isolates defined by pulsed-field gel electrophoresis (PFGE) were selected. The isolates were exposed over time to imipenem, meropenem and ceftazidime as well as to their combinations with ciprofloxacin and moxifloxacin. All isolates were resistant to all agents tested at concentrations equal to their average serum level. Synergy of any of the tested combinations was found in 10 isolates (41.7%). This was shown after 4h and 6h of exposure accompanied by re-growth after 24h. Not all the tested combinations were active against the same isolates. The combinations of imipenem+ciprofloxacin, ceftazidime+ciprofloxacin and imipenem+moxifloxacin were the most active. When time-kill assays were repeated for the latter isolates at antimicrobial concentrations equal to their maximum serum levels, synergy was prolonged to 24h. The present findings should be interpreted with caution for the management of infections by MDR P. aeruginosa. They underscore the potential interest of reporting synergism between beta-lactams and fluoroquinolones in the nosocomial setting when a MDR isolate emerges.

Combination drugs, an emerging option for antibacterial therapy

The emerging and sustained resistance to antibiotics and the poor pipeline of new antibacterials is creating a major health issue worldwide. Bacterial pathogens are increasingly becoming resistant even to the most recently approved antibiotics. Few antibiotics are being approved by regulatory organizations, which reflects both the difficulty of developing such agents and the fact that antibiotic discovery programs have been terminated at several major pharmaceutical companies in the past decade. As a result, the output of the drug pipelines is simply not well positioned to control the growing army of resistant pathogens, although academic institutions and smaller companies are trying to fill that gap. An emerging option to fight such pathogens is combination therapy. Combinations of two antibiotics or antibiotics with adjuvants are emerging as a promising therapeutic approach. This article provides and discusses clinical and scientific challenges to support the development of combination therapy to treat bacterial infections.

Levofloxacin in the treatment of ventilator-associated pneumonia

The use of levofloxacin in critically ill patients has progressively increased since commercial marketing of the drug in 1999, despite the fact that few studies have been designed to assess the use of levofloxacin in this population. Pharmacological characteristics, broad spectrum of activity, and tolerability account for the high interest in the drug for the treatment of different infectious diseases, including ventilator-associated pneumonia (VAP), and the recommendation of levofloxacin in guidelines developed by a number of scientific societies. According to pharmacokinetic-pharmacodynamic data, it seems reasonable to assume that an increase in activity follows from a larger dose, so that 500 mg/12 h is adequate in patients with VAP. In critically ill patients with VAP, levofloxacin monotherapy is indicated for empirical treatment of patients with early onset pneumonia without risk factors for multiresistant pathogens, and in combination therapy for late onset VAP or for patients at risk for multiresistant pathogens. The use of levofloxacin in combination therapy is supported by multiple reasons, including: increased empirical coverage in infections with suspected intracellular pathogens; substitution for more toxic antimicrobial agents (e.g., aminoglycosides) in patients with renal dysfunction and in those at risk for renal insufficiency; and severity of systemic response to infection (septic shock) that justifies multiple treatment with better tolerated antibiotics. The availability of the oral formulation allows sequential therapy, switching from the intravenous route to the oral route. Levofloxacin is well tolerated by critically ill patients, with few adverse events of mild to moderate severity.

Pharmacodynamic assessment of the activity of high-dose (750 mg) levofloxacin, ciprofloxacin, and gatifloxacin against clinical strains of Pseudomonas aeruginosa

The objective of this study was to comparatively evaluate specific bacterial killing ability of high-dose (750 mg) levofloxacin, ciprofloxacin, and gatifloxacin against 2 clinical isolates of Pseudomonas aeruginosa (PA-21 and PA-2105). An in vitro pharmacodynamic modeling apparatus was used to expose the P. aeruginosa isolates to total peak concentrations and elimination characteristics associated with each quinolone. All experiments were conducted over 24 h, and a subsequent dose of ciprofloxacin was given at 12 h to emulate twice-daily dosing. Respective 3-log reductions in PA-24 occurred after 0.6, 1.0, and 2.6 h for levofloxacin, ciprofloxacin, and gatifloxacin; regrowth was seen with all 3 agents, but was greatest with gatifloxacin. PA-2105 had 2- to 4-fold higher minimal inhibitory concentrations (MICs) than PA-24. Gatifloxacin failed to achieve a 3-log reduction. Levofloxacin and ciprofloxacin took roughly 3.5 h to decrease initial inoculum by 3 logs, but regrowth of PA-2105 followed. Simulated doses of levofloxacin and ciprofloxacin showed comparable activity against each study isolate; less activity was observed with gatifloxacin. Levofloxacin versus PA-24 was the only regimen that approached the desired AUC/MIC(0-24) ratio of greater than 100-125 and achieved the targeted peak/MIC ratio of > or =8. Although quinolones are typically used in combination with other antibiotics for P. aeruginosa, differences in activity favor the use of levofloxacin or ciprofloxacin for the study isolates. Use of gatifloxacin may contribute to the increased rate of quinolone-resistant P. aeruginosa.

In vitro selection of resistance in Pseudomonas aeruginosa and Acinetobacter spp. by levofloxacin and ciprofloxacin alone and in combination with β-lactams and amikacin

OBJECTIVES

The aim of this study was to evaluate the ability of levofloxacin and ciprofloxacin alone and in combination with either ceftazidime, cefepime, imipenem, piperacillin-tazobactam or amikacin to select for antibiotic-resistant mutants of Pseudomonas aeruginosa and Acinetobacter spp.

METHODS

Clinical strains of P. aeruginosa (n = 5) and Acinetobacter spp. (n = 5) susceptible to all the drugs used in the study were assayed. Development of resistance was determined by multi-step and single-step methodologies. For multi-step studies, MICs were determined after five serial passages on antibiotic-gradient plates containing each antibiotic alone or in combination with levofloxacin or ciprofloxacin. Acquisition of resistance was defined as an increase of >or=4-fold from the starting MIC. In single-step studies, the frequency of spontaneous mutations was calculated after a passage on plates containing antibiotics alone and in combinations at concentrations equal to the highest NCCLS breakpoints.

RESULTS

Serial passages on medium containing single antibiotics resulted in increased MICs for each antibiotic; MIC increases were limited by antibiotics in combination. A decrease in the number of strains with MICs above the NCCLS breakpoints occurred when fluoroquinolones were combined with a second antibiotic for both P. aeruginosa and Acinetobacter spp. isolates. Frequencies of mutation were higher for antibiotics alone than for combinations.

CONCLUSIONS

Use of combinations of fluoroquinolones with beta-lactams and amikacin reduces the risk for in vitro selection of resistant P. aeruginosa and Acinetobacter spp.

Combination treatment of invasive fungal infections

The persistence of high morbidity and mortality from systemic fungal infections despite the availability of novel antifungals points to the need for effective treatment strategies. Treatment of invasive fungal infections is often hampered by drug toxicity, tolerability, and specificity issues, and added complications often arise due to the lack of diagnostic tests and to treatment complexities. Combination therapy has been suggested as a possible approach to improve treatment outcome. In this article, we undertake a historical review of studies of combination therapy and also focus on recent studies involving newly approved antifungal agents. The limitations surrounding antifungal combinations include nonuniform interpretation criteria, inability to predict the likelihood of clinical success, strain variability, and variations in pharmacodynamic/pharmacokinetic properties of antifungals used in combination. The issue of antagonism between polyenes and azoles is beginning to be addressed, but data regarding other drug combinations are not adequate for us to draw definite conclusions. However, recent data have identified potentially useful combinations. Standardization of assay methods and adoption of common interpretive criteria are essential to avoid discrepancies between different in vitro studies. Larger clinical trials are needed to assess whether combination therapy improves survival and treatment outcome in the most seriously debilitated patients afflicted with life-threatening fungal infections.

Use of Pharmacokinetics and Pharmacodynamics to Optimize Antimicrobial Treatment of Pseudomonas aeruginosa Infections

The study of pharmacodynamics has greatly enhanced our understanding of antimicrobials and has enabled us to optimize dosing regimens. Applying this knowledge to the clinical setting can be critical for the treatment of Pseudomonas aeruginosa infections. Because of its selectively permeable outer membrane and multiple efflux pump mechanisms, P. aeruginosa has high intrinsic resistance to many available antimicrobials. Numerous studies have established pharmacodynamic values for concentration-dependent agents (maximum serum concentration : minimum inhibitory concentration [MIC] and area under the serum concentration-time curve : MIC) and concentration-independent agents (i.e., percentage of time that the drug concentration remains greater than the MIC) that help predict the probability of a successful outcome. Current therapies attempt to meet these target values. However, to reduce the risk of clinical failures, combination therapy (typically, a beta -lactam with an aminoglycoside or fluoroquinolone) is commonly used to enhance eradication rates and decrease the risk of developing resistance. Although combination therapy ensures a greater chance of selection of appropriate treatment, timely initial administration of antimicrobial therapy remains a key factor for reducing the likelihood of death for these patients.

Simultaneous determination of cefepime and grepafloxacin in human urine by high-performance liquid chromatography

A liquid chromatographic method with UV detection for simultaneous determination of cefepime and grepafloxacin has been developed. The method uses a C18 column, equipped with a pre-column of the same material, and acetonitrile-0.1 M phosphoric acid/sodium hydroxide buffer (pH 3.0)-0.01 M n-octylamine (pH 3.0) as mobile phase in gradient mode. Mobile flow rate and sample volume injected were 1.3 mL min(-1) and 20 microL, respectively. Detection wavelengths were 259 nm for cefepime and 278 nm for grepafloxacin. The retention times were 4.03 min for cefepime and 8.85 min for grepafloxacin, with detection limits of 1.0 and 1.1 microg mL(-1), respectively. The method was applied to the determination of both antibiotics in spiked samples of human urine.

Relevance of soft-tissue penetration by levofloxacin for target site bacterial killing in patients with sepsis

Antimicrobial therapy of soft tissue infections in patients with sepsis sometimes lacks efficiency, despite the documented susceptibility of the causative pathogen to the administered antibiotic. In this context, impaired equilibration between the antibiotic concentrations in plasma and those in tissues in critically ill patients has been discussed. To characterize the impact of tissue penetration of anti-infective agents on antimicrobial killing, we used microdialysis to measure the concentration-versus-time profiles of levofloxacin in the interstitial space fluid of skeletal muscle in patients with sepsis. Subsequently, we applied an established dynamic in vivo pharmacokinetic-in vitro pharmacodynamic approach to simulate bacterial killing at the site of infection. The population mean areas under the concentration-time curves (AUCs) for levofloxacin showed that levofloxacin excellently penetrates soft tissues, as indicated by the ratio of the AUC from time zero to 8 h (AUC(0-8)) for muscle tissue (AUC(0-8 muscle)) to the AUC(0-8) for free drug in plasma (AUC(0-8 plasma free)) (AUC(0-8 muscle)/AUC(0-8 plasma free) ratio) of 0.85. The individual values of tissue penetration and maximum concentration (C(max)) in muscle tissue were highly variable. No difference in bacterial killing of a select Staphylococcus aureus strain for which the MIC was 0.5 microg/ml was found between individuals after exposure to dynamically changing concentrations of levofloxacin in plasma and tissue in vitro. In contrast, the decrease in the bacterial counts of Pseudomonas aeruginosa (MIC = 2 microg/ml) varied extensively when the bacteria were exposed to levofloxacin at the concentrations determined from the individual concentration-versus-time profiles obtained in skeletal muscle. The extent of bacterial killing could be predicted by calculating individual C(max)/MIC and AUC(0-8 muscle)/AUC(0-8 plasma free) ratios (R = 0.96 and 0.93, respectively). We have therefore shown in the present study that individual differences in the tissue penetration of levofloxacin may markedly affect target site killing of bacteria for which MICs are close to 2 microg/ml.