Tigecycline-Containing Regimens and Multi Drug-Resistant Acinetobacter baumannii: A Systematic Review and Meta-Analysis

Introduction: The use of tigecycline (TG) for the treatment of Acinetobacter baumannii is controversial. In this systematic review and meta-analysis, we aimed to better explore the safety and efficacy of TG for the treatment of multi drug-resistant (MDR) Acinetobacter. Methods: We searched PubMed/MEDLINE, Scopus, Cochrane Central, and Web of Science to identify studies reporting the clinical and microbiological efficacy and safety of regimens containing TG in patients with drug susceptibility testing (DST)-confirmed MDR A. baumannii, published until December 30, 2022. Observational studies were included if they reported clinical and microbiological efficacy of TG-based regimens. The Newcastle-Ottawa Scale (NOS) and Joana Briggs Institute (JBI) critical appraisal tool were used to assess the quality of included studies. Results: There were 30 observational studies, of which 19 studies were cohort and 11 studies were single group studies. Pooled clinical response and failure rates in the TG-containing regimens group were 58.1 (95% confidence interval [CI] 49.2-66.6) and 40.2 (95% CI 31.1-50.0), respectively. The pooled microbiological response rate was 32.1 (95% CI 19.8-47.5), and the pooled all-cause mortality rate was 41.1 (95% CI 34.1-48.4). Pooled clinical response and failure rates in the colistin-based regimens group were 52.7 (42.7-62.5) and 43.1 (33.1-53.8), respectively. The pooled microbiological response rate was 42.9 (16.2-74.5), and the pooled all-cause mortality rate was 34.3 (26.1-43.5). Conclusions: According to our results, the efficacy of the TG-based regimen is the same as other antibiotics. However, our study showed a high mortality rate and a lower rate of microbiological eradication for TG compared with colistin-based regimen. Therefore, our study does not recommend it for the treatment of MDR A. baumannii. However, this was a prevalence meta-analysis of observational studies, and for better conclusion experimental studies are required.

Tigecycline antibacterial activity, clinical effectiveness, and mechanisms and epidemiology of resistance: narrative review

Tigecycline is unique glycylcycline class of semisynthetic antimicrobial agents developed for the treatment of polymicrobial infections caused by multidrug-resistant Gram-positive and Gram-negative pathogens. Tigecycline evades the main tetracycline resistance genetic mechanisms, such as tetracycline-specific efflux pump acquisition and ribosomal protection, via the addition of a glycyclamide moiety to the 9-position of minocycline. The use of the parenteral form of tigecycline is approved for complicated skin and skin structure infections (excluding diabetes foot infection), complicated intra-abdominal infections, and community-acquired bacterial pneumonia in adults. New evidence also suggests the effectiveness of tigecycline for the treatment of severe Clostridioides difficile infections. Tigecycline showed in vitro susceptibility to Coxiella spp., Rickettsia spp., and multidrug-resistant Neisseria gonnorrhoeae strains which indicate the possible use of tigecycline in the treatment of infections caused by these pathogens. Except for intrinsic, or often reported resistance in some Gram-negatives, tigecycline is effective against a wide range of multidrug-resistant nosocomial pathogens. Herein, we summarize the currently available data on tigecycline pharmacokinetics and pharmacodynamics, its mechanism of action, the epidemiology of tigecycline resistance, and its clinical effectiveness.

Carbapenemase Genes and Multidrug Resistance of Acinetobacter Baumannii: A Cross Sectional Study of Patients with Pneumonia in Southern Vietnam

Background: Acinetobacter baumannii (Ab) is an opportunistic bacterial pathogen found in hospital-acquired infections including nosocomial pneumonia, especially multidrug-resistant Ab. This study aims to survey the drug resistance profiles of Ab isolated from patients in Thong Nhat Dong Nai General Hospital and assess the relationship between genotypes and antibiotic resistance; Methods: Ninety-seven Ab strains isolated from 340 lower respiratory tract specimens among pneumonia patients were used to screen the most common local carbapenemase genes. Antimicrobial susceptibility testing results and demographic data were collected and minimum inhibitory concentrations (MIC) of colistin were also determined; Results: Over 80% and 90% of Ab strains were determined as carbapenem-resistant and multidrug-resistant (MDR), respectively. Most of the strains carried carbapenemase genes, including blaOXA-51, blaOXA-23-like, blaOXA-58-like, and blaNDM-1, with proportions of 97 (100%), 76 (78.4%), 10 (10.3%), 6 (6.2%), respectively. Amongst these genes, blaOXA-23-like was the only gene which significantly influenced the resistance (p < 0.0001); and Conclusions: The severity of Ab antibiotic resistance is urgent and specifically related to carbapenemase encoding genes. Therefore, screening of MDR Ab and carbapenemase for better treatment options is necessary.

Clinical experience with tigecycline in the treatment of hospital-acquired pneumonia caused by multidrug resistant Acinetobacter baumannii

Background

Tigecycline, with broad in vitro antibacterial activity, has been widely used off-label for nosocomial pneumonia caused by multi-drug resistant Acinetobacter baumannii (MDRAB). However, many concerns have been raised about the efficacy of tigecycline treatment as the inconsistent results from previous clinical studies.

Methods

This retrospective study evaluated the outcome of adult patients with monomicrobial MDRAB nosocomial pneumonia treated with tigecycline between 2015 and 2017. Results.

A total of 77 patients was eligible for this study, and the overall clinical success and 30-day survival rates were 70.03 and 70.13%, respectively, however, the microbiological eradication rate was relatively low (48%). Multivariate analysis indicated that shorter duration of tigecycline use associated with increased clinical failure, whereas higher CURB65 scores, mechanical ventilation and tigecycline resistant to MDRAB have significant association with 30-day mortality.

Conclusions

Our results suggest that tigecycline is one of the potential choices for the treatment of hospital-acquired pneumonia caused by MDRAB, especially with a MIC≤2 mg/L. In addition, a longer duration of tigecycline treatment may be required to insure better clinical outcomes.

Comparison of Tigecycline or Cefoperazone/Sulbactam therapy for bloodstream infection due to Carbapenem-resistant Acinetobacter baumannii

Background

We retrospectively analyzed the effect of tigecycline and cefoperazone/sulbactam therapies on the prognosis of patients with carbapenem-resistant Acinetobacter baumannii bloodstream infection (CRAB-BSI).

Methods

CRAB-BSI patients receiving tigecycline therapy or cefoperazone/sulbactam therapy between January 2012 and December 2017 was enrolled, and strict exclusion criteria were followed. The 28-day mortality of patients was analyzed. The impact of cefoperazone/sulbactam therapy on prognosis was evaluated using Cox multivariate regression analysis. The 28-day mortality of patients receiving cefoperazone/sulbactam monotherapy and cefoperazone/sulbactam-based combination therapy was also compared.

Results

Three hundred forty eight patients with CRAB-BSI were enrolled in the study. Two hundred ten patients were included after applying the exclusion criteria. Of these, 135 patients received tigecycline therapy and 75 patients received cefoperazone/sulbactam therapy. The 28-day mortality of patients in the latter group was, significantly lower than that of the tigecycline group [29.3% vs. 51.9%; P = 0.001]. Cox multivariate regression analysis revealed that cefoperazone/sulbactam therapy exerted a protective effect on the prognosis of patients [hazard ratio 0.566, 95% confidence interval (0.342–0.940); P = 0.028]. Kaplan-Meier survival curve analysis indicated that the 28-day mortality of patients receiving cefoperazone/sulbactam therapy was lower than that of patients receiving cefoperazone/sulbactam monotherapy, but the difference was not significant (22.2% vs. 40%; P = 0.074). However, the mortality of patients receiving cefoperazone/sulbactam with imipenem/cilastatin was significantly lower than that of patients receiving cefoperazone/sulbactam monotherapy (P = 0.048).

Conclusions

Patients treated with cefoperazone/sulbactam therapy had a better clinical outcome. The mortality of patients receiving cefoperazone/sulbactam with imipenem/cilastatin seems to be the lowest.

Electronic supplementary material

The online version of this article (10.1186/s13756-019-0502-x) contains supplementary material, which is available to authorized users.

Efficacy of intravenous tigecycline in patients with Acinetobacter complex infections: results from 14 Phase III and Phase IV clinical trials

Background

Acinetobacter infections, especially multidrug-resistant (MDR) Acinetobacter infections, are a global health problem. This study aimed to describe clinical outcomes in patients with confirmed Acinetobacter spp. isolates who were treated with tigecycline in randomized clinical trials.

Materials and methods

Data from 14 multinational, randomized (open-label or double-blind), and active-controlled (except one) Phase III and IV studies were analyzed using descriptive statistics.

Results

A total of 174 microbiologically evaluable patients with Acinetobacter spp. infections (including MDR infections) were identified, and 95 received tigecycline to treat community-acquired pneumonia (CAP), diabetic foot infections (DFIs), hospital-acquired pneumonia (HAP), complicated intra-abdominal infections (cIAIs), infections with resistant pathogens (RPs), or complicated skin and skin-structure infections. The rate of cure of tigecycline for most indications was 70%–80%, with the highest (88.2%) in cIAIs. The rate of cure of the comparators was generally higher than tigecycline, but within each indication the 95% CIs for clinical cure for each treatment group overlapped. For most Acinetobacter isolates, the minimum inhibitory concentration of tigecycline was 0.12–2 μg/mL, with seven at 4 μg/mL and one at 8 μg/mL. The cure rate by tigecycline was 50% (95% CI 12.5%–87.5% in CAP) to 88.2% (95% CI 66.2%–97.1% in cIAIs) for all Acinetobacter, and 72.7% (95% CI 54.5%–93.2% in HAP) to 100% (95% CI 25%–100.0% in cIAIs) for MDR Acinetobacter. For the comparators, it was 83.8% (95% CI 62.8%–95.9% in HAP) to 100% (95% CI 75%–100% in cIAIs and 25%–100.0% in RPs) and 88% (95% CI 66%–97% in HAP) to 100% (95% CI 25%–100% in cIAIs and 75%–100% in DFIs), respectively.

Conclusion

These findings suggest that with appropriate monitoring, tigecycline may be a useful consideration for Acinetobacter infections alone or in combination with other anti-infective agents when other therapies are not suitable.

Tigecycline-based versus sulbactam-based treatment for pneumonia involving multidrug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex

BACKGROUND

The treatment options for pneumonia involving multidrug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii (MDR Acb) complex are limited, and the optimal treatment has not been established.

METHODS

To compare the efficacy of tigecycline-based with sulbactam (or ampicillin/sulbactam)-based therapy for pneumonia involving MDR Acb complex, we conducted a retrospective study comparing 84 tigecycline-treated adult patients during the period August 2007 to March 2010 with 84 sulbactam or ampicillin/sulbactam-treated adult patients during the period September 2004 to July 2007. Both groups had the matched Acute Physiology and Chronic Health Evaluation (APACHE) II score and received treatment for at least 7 days.

RESULTS

The mean APACHE II score was 20.1 for both groups. More patients in sulbactam group had ventilator use (89.3 % versus 69.0 %), bilateral pneumonia (79.8 % versus 60.7 %) and combination therapy (84.5 % versus 53.6 %), particularly with carbapenems (71.4 % versus 6.0 %), while more patients in tigecycline group had delayed treatment (41.7 % versus 26.2 %) (P <0.05). At the end of treatment, more patients in sulbactam group had airway MDR Acb complex eradication (63.5 % versus 33.3 %, P <0.05). The clinical resolution rate was 66.7 % for both groups. The mortality rate during treatment was 17.9 % in sulbactam group, and 25.0 % in tigecycline group (P = 0.259). The multivariate analysis showed that bilateral pneumonia was the only independent predictor for mortality during treatment (adjusted odds ratio, 2.717; 95 % confidence interval, 1.015 to 7.272).

CONCLUSIONS

Patients treated with either tigecycline-based or sulbactam-based therapy had a similar clinical outcome, but tigecycline group had a lower microbiological eradiation rate.

Insights into Newer Antimicrobial Agents Against Gram-negative Bacteria

Currently, drug resistance, especially against cephalosporins and carbapenems, among gram-negative bacteria is an important challenge, which is further enhanced by the limited availability of drugs against these bugs. There are certain antibiotics (colistin, fosfomycin, temocillin, and rifampicin) that have been revived from the past to tackle the menace of superbugs, including members of Enterobacteriaceae, Acinetobacter species, and Pseudomonas species. Very few newer antibiotics have been added to the pool of existing drugs. There are still many antibiotics that are passing through various phases of clinical trials. The initiative of Infectious Disease Society of America to develop 10 novel antibiotics against gram-negative bacilli by 2020 is a step to fill the gap of limited availability of drugs. This review aims to provide insights into the current and newer drugs in pipeline for the treatment of gram-negative bacteria and also discusses the major challenging issues for their management.

Ventilator-Associated Pneumonia (VAP) with Multidrug-Resistant (MDR) Pathogens: Optimal Treatment?

Ventilator-associated pneumonia (VAP) due to multidrug-resistant bacteria (MDR) is an emerging problem worldwide. Both gram-negative and gram-positive microorganisms are associated with VAP. We first describe the magnitude of the problem of MDR VAP followed by its clinical impact on survival outcomes, with the primary aim to review the optimal antibiotic choices to treat patients with MDR VAP. We discuss the challenges of intravenous and inhaled antibiotic treatments, as well as of monotherapy and combination antimicrobial therapies.

Sulbactam treatment for pneumonia involving multidrug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex

BACKGROUND

Multidrug-resistant (MDR) Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex has become an important cause of nosocomial pneumonia. Sulbactam is a β-lactamase inhibitor with antimicrobial activity against MDR Acb complex.

METHODS

To investigate outcomes of pneumonia involving MDR Acb complex treated with sulbactam or ampicillin/sulbactam for at least 7 days, we conducted a retrospective study of 173 adult patients over a 34 month period.

RESULTS

Of 173 patients, 138 (79.8%) received combination therapy, mainly with carbapenems (119/138, 86.2%). The clinical response rate was 67.6% and the 30 day mortality rate was 31.2%. The independent predictors of clinical failure were malignancy, bilateral pneumonia and shorter duration of treatment. In patients with sulbactam-susceptible strains, there was no difference in clinical and microbiological outcome between combination therapy and monotherapy. Compared to the sulbactam-susceptible group, the sulbactam-resistant group had a lower rate of airway eradication, a longer duration of treatment and a higher rate of combination therapy with predominantly carbapenems (p < 0.05). There was no significant difference between the two groups in clinical resolution and 30 day mortality rates.

CONCLUSIONS

Sulbactam could be a treatment option for pneumonia involving MDR Acb complex, and combination therapy with carbapenems could be considered for sulbactam-resistant cases.

How to treat VAP due to MDR pathogens in ICU patients

Background

The increasing occurrence of multidrug resistant (MDR) bacteria arises at a time when there is a lack of antibiotics active against these pathogens and few new antimicrobials are in the pipelines of the pharmaceutical industry. Treatment of ventilator-associated pneumonia (VAP) caused especially by MDR Gram-negative bacilli (GNB) represents a real challenge due to the dearth of treatment options.

Methods

We searched the medical literature relevant about management of ventilator-associated pneumonia caused by multi-drug resistant pathogens including GNB and methicillin-resistant S. aureus.

Results

Empirical therapy should be prescribed based on the local pattern of susceptibilities. Colistin and tigecycline are in many cases the unique options for the treatment of many episodes of VAP caused by MDR-GNB. Tigecyline (not licensed for treatment of pneumonia) should be used with an initial bolus of 200 mg followed by 100 mg every 12 h. The need for a loading dose and the administration of high doses of colistin (9 million IU/day in two or three doses) is currently accepted. Vancomycin has been considered the treatment of choice for pneumonia due to MRSA although linezolid may provide higher rate of clinical cure for MRSA VAP with a good safety profile. The initial antibiotic treatment must be reassessed and simplify in accordance of culture results.

Conclusions

Empirical treatment of VAP due to MDR pathogens should be based on knowledge of local ecology. A strategy combining early high doses of effective agents with subsequent simplification in the light of microbiologic information is recommended.

Multidrug-resistant and extensively drug-resistant Gram-negative pathogens: current and emerging therapeutic approaches

INTRODUCTION

In the era of multidrug-resistant, extensively drug-resistant (XDR) and even pandrug-resistant Gram-negative microorganisms, the medical community is facing the threat of untreatable infections particularly those caused by carbapenemase-producing bacteria, that is, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Therefore, all the presently available antibiotics, as well as for the near future compounds, are presented and discussed.

AREAS COVERED

Current knowledge concerning mechanisms of action, in vitro activity and interactions, pharmacokinetic/pharmacodynamics, clinical efficacy and toxicity issues for revived and novel antimicrobial agents overcoming current resistance mechanisms, including colistin, tigecycline, fosfomycin, temocillin, carbapenems, and antibiotics still under development for the near future such as plazomicin, eravacycline and carbapenemase inhibitors is discussed.

EXPERT OPINION

Colistin is active in vitro and effective in vivo against XDR carbapenemase-producing microorganisms in the critically ill host, whereas tigecycline, with the exception of P. aeruginosa, has a similar spectrum of activity. The efficacy of combination therapy in bacteremias and ventilator-associated pneumonia caused by K. pneumoniae carbapenemase producers seems to be obligatory, whereas in cases of P. aeruginosa and A. baumannii its efficacy is questionable. Fosfomycin, which is active against P. aeruginosa and K. pneumoniae, although promising, shares poor experience in XDR infections. The in vivo validity of the newer potent compounds still necessitates the evaluation of Phase III clinical trials particularly in XDR infections.

Carbapenem-resistant Acinetobacter ventilator-associated pneumonia: Clinical characteristics and outcome

Objective:

To study the clinical characteristics and 28-days mortality in patients with ventilator-associated pneumonia (VAP) due to carbapenem-resistant Acinetobacter (CRA).

Design:

Retrospective, observational, cohort study.

Setting:

Intensive care unit (ICU) of a university hospital.

Materials and Methods:

Microbiologically confirmed VAP due to CRA infection.

Intervention:

None.

Results:

Out of 87 patients with VAP due to CRA, 60 (69%) were male; whose median age was 51 years; 73 (84%) patients were medical; 26 (30%) had history of hospitalization in last 3 months; median acute physiology and chronic health evaluation (APACHE) II was 15 and median SOFA 9 at admission; primary reason for ICU admission was respiratory failure (34%); 46 (53%) patients had more than 2 organ failure at ICU admission; median length of ICU stay was 19 days; 66 (76%) patients need vasoactive agents during ICU stay, whereas 55 (63%) patients had renal failure; median duration of mechanical ventilation was 17 days; 22 (25%) patients had acute respiratory distress syndrome (ARDS) during ICU stay; 72 (83%) patients had exposure to carbapenem before inclusion in the study; 33 (38%) patients had same organism at other sites. In the follow-up, 47 (54%) patient survived at 28 days after having VAP; whereas only 40 (46%) patients were discharged from the hospital.

Conclusions:

CRA-VAP has high crude mortality. Advanced age; severity of illness and presence of pneumonia at ICU admission; and presence of shock, ARDS and renal failure have impact on outcome in these patients.

Surveillance and management of multidrug-resistant microorganisms

Multidrug-resistant organisms are an established and growing worldwide public health problem and few therapeutic options remain available. The traditional antimicrobials (glycopeptides) for multidrug-resistant Gram-positive infections are declining in efficacy. New drugs that are presently available are linezolid, daptomicin and tigecycline, which have well-defined indications for severe infections, and talavancin, which is under Phase III trial for hospital-acquired pneumonia. Unfortunately the therapies available for multidrug-resistant Gram-negatives, including carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae, are limited to only colistin and tigecycline. Both of these drugs are still not registered for severe infections, such as hospital acquired pneumonia. Consequently, as confirmed by scientific evidence, a multidisciplinary approach is needed. Surveillance, infection control procedures, isolation and antimicrobial stewardship should be implemented to reduce multidrug-resistant organism diffusion.

In vitro pharmacodynamics of human-simulated exposures of ampicillin/sulbactam, doripenem and tigecycline alone and in combination against multidrug-resistant Acinetobacter baumannii

OBJECTIVES

Multidrug resistance is common among Acinetobacter baumannii, limiting the available options used to treat infections caused by this organism. The objective of this study was to compare monotherapy and combination therapy with ampicillin/sulbactam, doripenem and tigecycline against multidrug-resistant A. baumannii using an in vitro pharmacodynamic model.

METHODS

Human free-drug concentration profiles of clinically relevant ampicillin/sulbactam, doripenem and tigecycline were simulated alone and in two-drug combinations against four clinical A. baumannii isolates (MICs: ampicillin/sulbactam, 4/2-64/32 mg/L; doripenem, 16 to ≥64 mg/L; and tigecycline, 1-4 mg/L) over 24 h. Microbiological response was measured as log10 cfu/mL and the area under the bactericidal curve (AUBC).

RESULTS

Control strains grew to 7.11 ± 0.13 log10 cfu/mL. Except for ampicillin/sulbactam-containing regimens against the single ampicillin/sulbactam-susceptible isolate, all A. baumannii demonstrated regrowth to 24 h control levels against all mono and combination regimens. Using AUBC as an endpoint, the most active regimens were 9 g of ampicillin/sulbactam every 8 h (3 h infusion) + 2 g of doripenem every 8 h (4 h infusion; 87.8 ± 21.0), 9 g of ampicillin/sulbactam every 8 h (3 h infusion) + 200 mg of tigecycline every 12 h (30 min infusion; 100.6 ± 33.0) and 9 g of ampicillin/sulbactam every 8 h (3 h infusion) monotherapy (116.7 ± 31.6), followed by 3 g of ampicillin/sulbactam every 6 h (30 min infusion) + 200 mg of tigecycline every 12 h (30 min infusion; 134.0 ± 31.5) and 2 g of doripenem every 8 h (4 h infusion) + 200 mg of tigecycline every 12 h (30 min infusion; 142.7 ± 16.9).

CONCLUSIONS

Although specific combination regimens displayed additive activity at aggressive doses against these multidrug-resistant A. baumannii, none of the regimens could maintain cfu reductions against the more resistant isolates.

Clinical outcomes of tigecycline in the treatment of multidrug-resistant Acinetobacter baumannii infection

PURPOSE

Acinetobacter baumannii (A. baumannii) has emerged as a major cause of nosocomial pneumonia and sepsis in seriously ill patients. Multidrug-resistant A. baumannii (MDRAB) is increasing in frequency, and the management of it's infections is consequently difficult. Therefore, tigecycline is considered to be the drug of choice for MDRAB treatment. The aim of our study was to evaluate the microbiological eradication and clinical effectiveness of tigecycline against MDRAB in seriously ill patients, including patients with ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

We conducted a retrospective study including patients with A. baumannii infections who were treated with tigecycline between April 1, 2009 and March 31, 2010. We treated 27 patients with tigecycline for MDRAB infections.

RESULTS

The mean age of patients was 66.2 years, and 20 (74.1%) patients were male. The median length of stay at hospital was 74.6 days. MDRAB was eradicated from the site of infection in 23 cases (85.2%), however, only 17 cases (63.0%) showed positive clinical responses. Overall, an in-hospital mortality rate of 51.9% was observed, and 4 cases of death were attributable to sepsis. The combination therapy showed better clinical and microbial success rates than the monotherapy without significant difference.

CONCLUSION

We observed the relatively low clinical success rate although the microbial eradication rate was high, probably due to superinfections in VAP and bacteremia. We suggest that clinicians should limit tigecycline monotherapy for MDRAB infection in critically ill patients, until large controlled clinical trials should be conducted.

Impact of inappropriate empiric antimicrobial therapy on mortality of septic patients with bacteremia: a retrospective study

Background. Inappropriate empiric antimicrobials could be a major cause of unfavorable mortality rates in co-morbid patients. This study aimed to assess the prevalence and impact of first-dose and 24-hour inappropriate antimicrobials on mortality rates of bacteremic septic patients. Methods. A retrospective cohort study was employed. Case record forms of patients diagnosed as sepsis, severe sepsis, or septic shock with positive hemoculture during 2009 were retrieved from the medical wards, Siriraj Hospital. Demographic data, antimicrobial use, types of bacteria isolated from blood and susceptibilities, patients' comorbidities, 28-day and overall mortality rates were collected and analyzed. Results. There were 229 cases, mean age (SD) of 63.5 (17.2) years and mean (SD) APACHE II score of 24.7 (6.8). The prevalence of first-dose and 24-hour inappropriate antimicrobials was 29.7% and 25.3%, respectively. The 28-day and overall mortality rates between first-dose inappropriate and appropriate antimicrobial were 67.6% versus 60.2% (P = 0.301) and 75.0% versus 68.3% (P = 0.345), consequently. Patients with septic shock and inappropriate first-dose antimicrobials significantly had higher 28-day mortality rate (61.6% versus 41.9%; P = 0.017). Conclusion. Higher mortality rates in bacteremic septic patients were substantially associated with inappropriate first-dose antimicrobials and 3-hour delayed antimicrobial administration after sepsis diagnosis.

Clinical experience of tigecycline treatment in infections caused by extensively drug-resistant Acinetobacter spp

BACKGROUND

Tigecycline has broad spectrum antimicrobial activity and is approved for complicated intra-abdominal infections, complicated skin and soft tissue infections, and community-acquired pneumonia. There are few data on clinical experience of tigecycline in hospital-acquired pneumonia (HAP) and Acinetobacter spp. infection.

METHODS

A retrospective study was performed at eight hospitals in Korea from May 2009 to January 2010. Adult patients treated with tigecycline regardless of their source of infection or pathogens were enrolled.

RESULTS

Tigecycline was administered in 108 patients. Pneumonia was the most common infection (43.5%), followed by skin and soft tissue infections (20.4%). Acinetobacter baumannii was isolated from 83 patients (76.9%) accounting for 50.3% of isolated pathogens, showing a resistance rate of 67.5% to carbapenems. Superinfection was identified in 32 patients (29.6%). Pseudomonas aeruginosa was most common microorganism causing superinfection (46.9%). Overall 30-day mortality rate was 52.9%. Thirty-day mortality rate of HAP and Acinetobacter spp. infection was 60.5% and 59.4%, respectively.

CONCLUSION

Tigecycline can be considered as an alternative therapy in patients with HAP or infections caused by Acinetobacter spp., especially extensively drug-resistant A. baumannii.

Management of antimicrobial use in the intensive care unit

Critically ill patients admitted to the intensive care unit (ICU) are frequently treated with antimicrobials. The appropriate and judicious use of antimicrobial treatment in the ICU setting is a constant clinical challenge for healthcare staff due to the appearance and spread of new multiresistant pathogens and the need to update knowledge of factors involved in the selection of multiresistance and in the patient's clinical response. In order to optimize the efficacy of empirical antibacterial treatments and to reduce the selection of multiresistant pathogens, different strategies have been advocated, including de-escalation therapy and pre-emptive therapy as well as measurement of pharmacokinetic and pharmacodynamic (pK/pD) parameters for proper dosing adjustment. Although the theoretical arguments of all these strategies are very attractive, evidence of their effectiveness is scarce. The identification of the concentration-dependent and time-dependent activity pattern of antimicrobials allow the classification of drugs into three groups, each group with its own pK/pD characteristics, which are the basis for the identification of new forms of administration of antimicrobials to optimize their efficacy (single dose, loading dose, continuous infusion) and to decrease toxicity. The appearance of new multiresistant pathogens, such as imipenem-resistant Pseudomonas aeruginosa and/or Acinetobacter baumannii, carbapenem-resistant Gram-negative bacteria harbouring carbapenemases, and vancomycin-resistant Enterococcus spp., has determined the use of new antibacterials, the reintroduction of other drugs that have been removed in the past due to toxicity or the use of combinations with in vitro synergy. Finally, pharmacoeconomic aspects should be considered for the choice of appropriate antimicrobials in the care of critically ill patients.

Comparison of tigecycline with imipenem/cilastatin for the treatment of hospital-acquired pneumonia

To compare efficacy and safety of a tigecycline regimen with an imipenem/cilastatin regimen in hospital-acquired pneumonia patients, a phase 3, multicenter, randomized, double-blind, study evaluated 945 patients. Coprimary end points were clinical response in clinically evaluable (CE) and clinical modified intent-to-treat (c-mITT) populations at test-of-cure. Cure rates were 67.9% for tigecycline and 78.2% for imipenem (CE patients) and 62.7% and 67.6% (c-mITT patients), respectively. A statistical interaction occurred between ventilator-associated pneumonia (VAP) and non-VAP subgroups, with significantly lower cure rates in tigecycline VAP patients compared to imipenem; in non-VAP patients, tigecycline was noninferior to imipenem. Overall mortality did not differ between the tigecycline (14.1%) and imipenem regimens (12.2%), although more deaths occurred in VAP patients treated with tigecycline than imipenem. Overall, the tigecycline regimen was noninferior to the imipenem/cilastatin regimen for the c-mITT but not the CE population; this difference appears to have been driven by results in VAP patients.

Comprehensive assessment of tigecycline activity tested against a worldwide collection of Acinetobacter spp. (2005-2009)

A total of 5127 Acinetobacter spp. were collected from 140 hospitals in 32 countries in North America (17.1%), Europe (22.9%), Latin America (25.2%), and the Asia-Pacific (APAC) region (34.8%). Tigecycline MIC distributions were bimodal against isolates from North America and APAC region, while a unimodal pattern was noted for strains from Latin America. A variable MIC distribution was noted in Europe. Only tigecycline (MIC(50/90), 0.5/2 μg/mL) and polymyxin B (MIC(50/90), 0.5/1 μg/mL; 98.6% susceptible) exhibited high activity against Acinetobacter spp. Overall, tigecycline inhibited at least 90.0% of Acinetobacter spp. isolates from all countries evaluated at ≤2 μg/mL, as well as 95.0% of those displaying multidrug resistance. Other tested agents showed limited activity and a significant (P < 0.001) trend toward decreased susceptibility during the study period.

Systematic review and meta-analysis of the effectiveness and safety of tigecycline for treatment of infectious disease

The aim of this study was to compare the efficacy and safety of tigecycline, a newly developed glycylcycline antibiotic, with those of empirical antibiotic regimens which have been reported to possess good efficacy for complicated skin and skin structure infections (cSSSIs), complicated intra-abdominal infections (cIAIs), community-acquired pneumonia (CAP), and other infections caused by methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE). A meta-analysis of randomized controlled trials (RCTs) identified in PubMed, the Cochrane Library, and Embase was performed. Eight RCTs involving 4,651 patients were included in the meta-analysis. Compared with therapy with empirical antibiotic regimens, tigecycline monotherapy was associated with similar clinical treatment success rates (for the clinically evaluable [CE] population, odds ratio [OR] = 0.92, 95% confidence interval [CI] = 0.76 to 1.12, P = 0.42; for the clinical modified intent-to-treat [c-mITT] population, OR = 0.86, 95% CI = 0.74 to 1.01, P = 0.06) and similar microbiological treatment success rates (for the microbiologically evaluable [ME] population, OR = 0.86, 95% CI = 0.69 to 1.07, P = 0.19). The incidence of adverse events in the tigecycline group was significantly higher than that in the other therapy groups with a statistical margin (for the modified intent-to-treat [mITT] population, OR = 1.33, 95% CI = 1.17 to 1.52, P < 0.0001), especially in the digestive system (mITT population, OR = 2.41, 95% CI = 1.67 to 3.46, P < 0.00001). No difference regarding all-cause mortality and drug-related mortality between tigecycline and the other regimens was found, although numerically higher mortality was found in the tigecycline group. This meta-analysis provides evidence that tigecycline monotherapy may be used as effectively as the comparison therapy for cSSSI, cIAIs, CAP, and infections caused by MRSA/VRE. However, because of the high risk of mortality, AEs, and emergence of resistant isolates, prudence with the clinical use of tigecycline monotherapy in infections is required.

Multidrug-resistant Gram-negative infections: what are the treatment options?

The emergence of multidrug-resistant (MDR) Gram-negative bacilli creates a challenge in the treatment of nosocomial infections. While the pharmaceutical pipeline is waning, two revived old antibacterials (colistin and fosfomycin), a newer one (tigecycline) and an 'improved' member of an existing class (doripenem) are the only therapeutic options left. The class of polymyxins, known since 1947 and represented mostly by polymyxin B and polymyxin E (colistin), has recently gained a principal role in the treatment of the most problematic MDR Gram-negative pathogens (such as Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia). Future prospective studies are needed to answer important clinical questions, such as the possible benefit of combination with other antimicrobials versus monotherapy, the efficacy of colistin in neutropenic hosts and the role of inhaled colistin. As new pharmacokinetic data emerge, clarification of the pharmacokinetic/pharmacodynamic (PK/PD) profile of colistin as well as appropriate dosing seems urgent, while development of resistance must be carefully monitored. Fosfomycin tromethamine, a synthetic salt of fosfomycin discovered in 1969, has regained attention because of its in vitro activity against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and MDR P. aeruginosa. Although in use for decades in oral and parenteral formulations for a variety of infections without significant toxicity, its clinical utility in MDR infections remains to be explored in future studies. Tigecycline, the first representative of the new class of glycylcyclines, holds promise in infections from MDR K. pneumoniae (K. pneumoniae carbapenemase [KPC]- and ESBL-producing strains) and Enterobacteriaceae with various mechanisms of resistance. The in vitro activity of tigecycline against A. baumannii makes it a tempting option, as it is currently the most active compound against MDR strains along with colistin. However, the usual minimum inhibitory concentration values of this pathogen are approximately 2 mg/L and compromise clinical outcomes based on PK/PD issues. Its advantageous penetration into various tissues is useful in infections of the skin and soft tissues as well as intra-abdominal infections (official indications), whereas low serum concentrations compromise its use in bloodstream infections. Therefore, prospective studies with dose escalation are urgently needed, as well as clarification of its role in nosocomial pneumonia, after poor results in the study of ventilator-associated pneumonia. Finally, doripenem, the recently licensed member of the carbapenems (without significant spectrum alterations from the ascendant members) seems to possess a lower potential for resistance selection and a more favourable pharmacokinetic profile when given as an extended infusion. The latter strategy could prove helpful in overcoming low level resistance of A. baumannii and P. aeruginosa strains.