A Visualized Mortality Prediction Score Model in Hematological Malignancies Patients with Carbapenem-Resistant Organisms Bloodstream Infection

Background

Bloodstream infection (BSI) due to carbapenem-resistant organisms (CROs) has emerged as a worldwide problem associated with high mortality. This study aimed to evaluate the risk factors associated with mortality in HM patients with CROs BSI and to establish a scoring model for early mortality prediction.

Methods

We conducted a retrospective cohort study at our hematological department from January 2018 to December 2021, including all HM patients with CROs BSI. The outcome measured was death within 30-day of BSI onset. Survivor and non-survivor subgroups were compared to identify predictors of mortality. Univariate and multivariate Cox regression analyses were used to identify prognostic risk factors and develop a nomogram.

Results

In total, 150 HM patients were included in the study showing an overall 30-day mortality rate of 56%. Klebsiella pneumonia was the dominant episode. Cox regression analysis showed that pre-infection length of stay was >14 days (score 41), Pitt score >4 (score 100), mucositis (score 41), CAR (The ratio of C-reactive protein to albumin) >8.8 (score 57), early definitive therapy (score 44), and long-duration (score 78) were positive independent risk predictors associated with 30-day mortality, all of which were selected into the nomogram. Furthermore, all patients were divided into the high-risk group (≥160 points) or the low-risk group based on the prediction score model. The mortality of the high-risk group was 8 times more than the low-risk group. Kaplan-Meier analysis showed that empirical polymyxin B therapy was associated with a lower 30-day mortality rate, which was identified as a good prognostic factor in the high-risk group. In comparison, empirical carbapenems and tigecycline were poor prognostic factors in a low-risk group.

Conclusion

Our score model can accurately predict 30-day mortality in HM patients with CROs BSI. Early administration of CROs-targeted therapy in the high-risk group is strongly recommended to decrease mortality.

Comparison of pneumonia- and non-pneumonia-related Acinetobacter baumannii complex bacteremia: A single-center retrospective study

BACKGROUND

Acinetobacter baumannii complex (ABC) is a group of increasingly prevalent opportunistic pathogens that cause a variety of life-threatening nosocomial infections, especially in the intensive care unit (ICU). This study assessed the differences between pneumonia- and non-pneumonia-related ABC bacteremia and possible independent risk factors for 30-day mortality.

METHODS

The clinical data of ICU patients diagnosed with ABC bacteremia at a tertiary care hospital from January 2009 to December 2020 were collected, and sorted into groups of ABC bacteremia with and without pneumonia.

RESULTS

Significant changes in the incidence of ABC bacteremia and antibiotic resistance were observed over the 12-year study. Compared with nonpneumonia-related ABC bacteremia, pneumonia-related ABC bacteremia was associated with a higher rate of hypertension, less prior tigecycline use, more carbapenem-resistant (CR) strains, and a higher 30-day mortality rate. In multivariate analysis, immunosuppression, higher APACHE II score, and SOFA score were independent risk factors for 30-day mortality. Moreover, the risk of death was 1.919 times higher in the pneumonia-related group.

CONCLUSIONS

Although pneumonia-related ABC bacteremia had worse outcomes, it was not an independent risk factor for death statistically. Immunosuppression and disease severity levels increased the risks of death in ICU patients with ABC bacteremia.

Isolating and sequencing vB_Kpn_3, a lytic bacteriophage against multidrug-resistant Klebsiella pneumoniae

Aim: Phage therapy, as an effective and specific method in the treatment of multidrug-resistant (MDR) bacterial infections, has attracted the attention of many researchers. Methods and results: In this study, a double-stranded DNA phage with the ability of lysing some strains of MDR Klebsiella pneumoniae (vB_Kpn_3) was isolated from hospitals' wastewater and then characterized morphologically and genetically. Transmission electron microscopy and genetic analyses have revealed that vB_Kpn_3 is a member of Siphoviridae family. One-step growth curve also showed a burst time of 35 min and a burst size of 31 PFU/ml. The genome of the phage is composed of 112,080 bp with 41.33% G + C content carrying 186 open reading frames. Conclusion: vB_Kpn_3 is a broad host range phage that infects MDR K. pneumoniae and some other species of Enterobacteriaceae such as Escherichia coli and Salmonella typhi. In addition, no antibiotic resistance and toxin genes were detected in its genome.

Acute pancreatitis caused by tigecycline: A case report and literature review

RATIONALE

There is evidence that tigecycline has broad-spectrum antibiotic activity against a variety of complicated infections. However, adverse effects are inevitable, including gastrointestinal side effects such as nausea, vomiting, and diarrhea; in 2006, acute pancreatitis was also brought into the side-effect list after postmarketing surveillance. Here, we present a case of tigecycline-induced acute pancreatitis.

PATIENT CONCERNS

An 87-year-old female patient with urinary tract infection received an intravenous drip of tigecycline for 6 days, after which she developed abdominal distension, vomiting, abdominal pain, and abdominal rigidity.

DIAGNOSIS

The patient was suspected to have tigecycline-induced acute pancreatitis.

INTERVENTIONS

Tigecycline was discontinued immediately, and the patient received a series of immediate treatments including an indwelling gastric tube for continuous gastrointestinal decompression and inhibition of gastric acid and pancreatic enzyme secretion.

OUTCOMES

Following initial interventions, we observed that the patient's symptoms improved significantly, and abdominal distension, vomiting, abdominal pain, and abdominal rigidity were slightly relieved. After 5 days of follow-up, blood lipase and amylase levels decreased to normal levels. Unfortunately, the patient developed convulsions during the use of multiple antibiotics after 1 week and then died of septic shock and acute liver failure.

LESSONS

Acute pancreatitis caused by tigecycline is rare. However, in the application of antibiotics, the possibility of adverse effects must be considered, and antibiotics should be used reasonably. If the patient has relevant symptoms, it is necessary to stop using tigecycline immediately, carry out symptomatic treatment, and change to other types of antibiotics for antibacterial treatment.

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.

Synergistic antibacterial effect of inhaled aztreonam and tobramycin fixed dose combination to combat multidrug-resistant Gram-negative bacteria

The limited therapeutic option for respiratory infections caused by multi-drug resistant microbial pathogens is a major global health threat. Topical delivery of antibacterial combinations to the lung could dramatically enhance antibacterial activities and provide a means to overcome bacterial resistance development. The aim of the study was to investigate the potential of new inhalable dry powder combinations consisting of a fixed dose of aztreonam (Azt) and tobramycin (Tob) using a spray drying process, against antibiotic resistant Gram-negative respiratory pathogens. The interactions of Azt with Tob on resistant Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii were determined by calculating factional inhibitory concentration indices (FICI). A fixed concentration ratio of Azt and Tob that exhibited a synergistic antimicrobial effect was selected and formulated into inhalable dry powders by co-spray drying with and without L-leucine. The obtained dry powders were characterized with respect to the morphology, particle size distribution, solid state, moisture sorption behaviour, and in vitro dissolution. Storage stability, aerosol performance, and in vitro antibacterial activity were also evaluated. Inhalable dry powders consisting of Azt, Tob and L-leucine could be readily obtained via the spray drying process with a fine particle fraction of above 40% as determined using a next generation impactor. The co-spray drying process resulted in amorphous Azt/Tob dry powders with or without the addition of L-leucine as indicated by X-ray powder diffraction. The dissolution rates of the co-spray dried Azt/Tob dry powders were decreased, and the storage stability was improved with an increase in the proportion of L-leucine in the formulations. The inclusion of L-leucine did not affect the minimum inhibitory concentration and the co-spray dried powders reserved the synergistic antibacterial effects and exhibited enhanced antibacterial activities as compared to the individual antibiotic used alone on multidrug-resistant (Azt and Tob resistant) P. aeruginosa 25756 and A. baumannii K31. This study demonstrates that inhalable Azt/Tob dry powders using L-leucine as a moisture protector as well as a dispersing agent can be readily prepared by the spray drying process. This new inhalable fixed dose combinational dry powders may represent an alternative treatment against multidrug-resistant Gram-negative respiratory pathogens.

Risk factors for tigecycline-induced hypofibrinogenaemia

WHAT IS KNOWN AND OBJECTIVE

Hypofibrinogenaemia is major treatment-related adverse event associated with tigecycline therapy, which in some cases can result in treatment termination. We aimed to identify the risk factors for tigecycline-induced hypofibrinogenaemia.

METHODS

We retrospectively retrieved 426 Chinese patients who were undergoing tigecycline therapy ≥ 3 days.

RESULTS AND DISCUSSION

There were 426 patients treated with tigecycline. The mean age was 60.31 ± 19.23 years, and 299 (70.19%) patients were male. Of the patients, 50.5% developed hypofibrinogenaemia and 10.1% of patients developed bleeding. Compared with before treatment, fibrinogen (FIB) significantly decreased after tigecycline was used while prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) significantly increased (all P < .001). There was no statistically significant difference in platelet count, hepatic function, and renal function before and after tigecycline treatment (all P > .05). In analysing relevant risk factors, extension of the tigecycline treatment course was found to be the main risk factor for tigecycline-induced hypofibrinogenaemia. Regardless of whether patients received the standard dose or high dose of tigecycline, the long treatment course group (>14 days) had more patients with hypofibrinogenaemia than the routine treatment course group (52.21% vs 40.74%, 48.81% vs 19.44%, all P < .05). Renal failure (whether requiring or not requiring dialysis) is also a risk factor for tigecycline-induced hypofibrinogenaemia (OR [95% CI]: 2.450 [1.335-4.496]).

WHAT IS NEW AND CONCLUSION

Tigecycline administration has been related to hypofibrinogenaemia, especially patients with renal failure and when long treatment course of tigecycline are used. We recommend that coagulation function be closely monitored in patients with the aforementioned risk factors for tigecycline-induced hypofibrinogenaemia to ensure patient safety.

Tigecycline Therapy for Infections Caused by Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Critically Ill Patients

: We aimed to evaluate tigecycline on the clinical effectiveness in treating complicated skin and soft tissue infections (cSSTI), complicated intra-abdominal infections (cIAI), and pneumonia, caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, as data are limited. From three medical centers in Taiwan, we retrospectively studied the cSSTI, cIAI, and/or pneumonia caused by ESBL-producing Enterobacteriaceae. Among the 71 patients, including 39 patients infected with Klebsiella pneumoniae, 30 infected with Escherichia coli and others, the clinical success rate of tigecycline-based therapy was 80%-90% for pneumonia and cSSTI caused by E. coli and 50%-60% for cIAI caused by K. pneumoniae and E. coli. Microbiological and clinical outcome of pneumonia caused by carbapenem-resistant K. pneumoniae was poor. Univariate Cox analysis showed that dyspnea, SOFA score, septic shock, thrombocytopenia, prolonged prothrombin time, and lesser microbiological eradication were significant factors associated with 30-day mortality after the end of therapy. Cox regression proportional hazards model revealed dyspnea and a SOFA score > 8 to be independently associated with time to death. For ESBL producers, tigecycline showed good effects for cSSTI and pneumonia by E. coli, ordinary for cIAI, but ineffective for pneumonia by K. pneumoniae. Dyspnea and a high SOFA score predict a poor outcome.

Optimizing therapy of bloodstream infection due to extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE OF REVIEW

Infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are increasing worldwide. Carbapenems are usually regarded as the antibiotics of choice for the treatment of serious ESBL infections. However, because of the alarming emergence or carbapenem resistance, interest in effective alternatives has emerged. The present review summarizes the findings published on the antibiotics currently available for treatment of patients with an ESBL-E bloodstream infection (BSI).

RECENT FINDINGS

Meropenem and imipenem are the drugs recommended for treatment of ESBL BSIs in critically ill patients, and in infections with high bacterial loads or elevated β-lactam minimum inhibitory concentrations. Ertapenem should be reserved for patients with less severe presentations, and should be used at high doses. In milder presentations or BSIs from low-risk sources, other carbapenem-sparing alternatives could be considered: cephamycins, fluoroquinolones, and particularly a β-lactam/β-lactam inhibitor combination (particularly piperacillin/tazobactam). Optimized dosing of piperacillin/tazobactam is recommended (high doses and extended infusion). There are few data on the use of the promising newly available drugs (e.g. ceftolozane/tazobactam, ceftazidime/avibactam, cefiderocol, and plazomicin), and it seems reasonable to reserve them as last-resort drugs.

SUMMARY

Carbapenems should be used in patients with serious infections; alternatives could be used individually, particularly for definitive treatment of patients with milder presentations.

Choice of therapeutic interventions and outcomes for the treatment of infections caused by multidrug-resistant gram-negative pathogens: a systematic review

Background

Antimicrobial resistance is an increasingly serious threat to public health, and the increased occurrence of multidrug-resistant (MDR) bacteria is a concern in both high-income and low- and middle-income countries. The purpose of this systematic review was to identify and critically appraise current antimicrobial treatment options for infections with MDR Gram-negative bacteria.

Methods

A literature search for treatment of MDR extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, A. baumannii, and P. aeruginosa was conducted in MEDLINE in January 2019. Relevant studies published in English, German, and French that evaluated clinical success, microbiological success, and 30-day mortality outcomes were included. The population of interest was adult patients.

Results

Of 672 studies, 43 met the inclusion criteria. Carbapenems are the most common antibiotics used for the treatment of ESBL-producing Enterobacteriaceae. The clinical and microbiological success was similar for group 1 carbapenems (imipenem, meropenem, or doripenem), group 2 carbapenems (ertapenem), and non-carbapenem antibiotics. Mortality data were contradictory for group 1 carbapenems compared to group 2 carbapenems. The most common treatment option for A. baumannii and P. aeruginosa infections was intravenous colistin, regardless of infection site. Clinical success and mortality were similar in A. baumannii infections treated with colistin combination therapy vs. colistin monotherapy, whereas heterogeneous results were found with respect to microbiological success. Monotherapy and colistin combination therapy were used against P. aeruginosa with clinical and microbiological success (70–100%) depending on the infection site and severity, and the antibiotic used. Ceftazidime-avibactam therapy for ESBL-producing Enterobacteriaceae and P. aeruginosa showed good clinical success in one study.

Conclusion

We did not find robust evidence for antibiotic treatment of any infection with MDR Gram-negative bacteria, including ESBL-producing Enterobacteriaceae, A. baumannii, and P. aeruginosa, that would lead to a firm recommendation for one specific antibiotic over another or for monotherapy over combination therapy. The choice of antibiotic treatment should be based on susceptibility testing balancing the expected clinical success rate against the risk of development of antibiotic resistance and the risk of severe side effects.

A Retrospective Analysis of the Effect of Tigecycline on Coagulation Function

A number of clinical trials demonstrated that tigecycline was effective and well tolerated in the treatment of patients with various bacterial infections, but few literatures had shown the coagulopathy induced by tigecycline. To address this concern, we performed a retrospective analysis to assess the impact of tigecycline treatment on coagulation parameters in 50 patients with bacterial infections in our hospital (Shandong Provincial Hospital, China). These patients were treated with tigecycline at Shandong Provincial Hospital in 2015-2016 at either a recommended (50 mg q12h) or a higher dose (100 mg q12h). Coagulation parameters, including Fibrinogen (FIB) levels, prothrombin time (PT), activated partial thromboplastin time (aPTT), platelet count (PLT) and D-dimer, were evaluated in order to assess the impact of tigecycline treatment in these severely infected patients. What we found was that the plasma fibrinogen (FIB) level was 4.63 ± 1.56 g/L before tigecycline treatment, and decreased to 2.92 ± 1.23 g/L during treatment, which was statistically significant (p < 0.001). The mean values of aPTT and PT were significantly increased from 39.58 ± 8.72 to 44.05 ± 10.45 s (p = 0.002), and from 15.37 ± 1.53 to 16.37 ± 2.64 s (p = 0.004), respectively. This study demonstrates that treatment of tigecycline could reduce FIB, prolong aPTT and PT. In conclusion, we advise that it is necessary for practitioners routinely monitor coagulation level in at-rick patient populations treated with tigecycline.

Once Daily High Dose Tigecycline Is Optimal: Tigecycline PK/PD Parameters Predict Clinical Effectiveness

OBJECTIVE

The clinical effectiveness of tigecycline depends on appropriate use, and PK/PD (pharmacokinetic/pharmacodynamic) parameters related to dose and dosing interval.

METHODS

In our 600-bed university-affiliated teaching hospital, we conducted a tigecycline efficacy review over a three-month period in 34 evaluable patients. Parameters assessed included clinical response, cure or treatment failure, once daily as q12h dosing, maintenance dosing, high dose vs. standard loading regimens, adverse effects, and the effect of infectious disease consultation on outcomes.

RESULTS

We found once daily high dose tigecycline (HDT) was highly effective in treating serious systemic infections due to MDR Gram-positive/negative pathogens as well as C. difficile colitis. Adverse effects were infrequent and limited to mild nausea/vomiting. Once daily HDT was highly effective, and the few treatment failures were related to suboptimal/split dosing regimens.

CONCLUSION

Once daily HDT was highly effective when used to treat susceptible pathogens and when optimally dosed, i.e., 200-400 mg (IV) loading dose ×1, followed by a once daily maintenance dose of 100-200 mg (IV) q24h.

Treatment of Infections Caused by Extended-Spectrum-Beta-Lactamase-, AmpC-, and Carbapenemase-Producing Enterobacteriaceae

Therapy of invasive infections due to multidrug-resistant Enterobacteriaceae (MDR-E) is challenging, and some of the few active drugs are not available in many countries. For extended-spectrum β-lactamase and AmpC producers, carbapenems are the drugs of choice, but alternatives are needed because the rate of carbapenem resistance is rising. Potential active drugs include classic and newer β-lactam-β-lactamase inhibitor combinations, cephamycins, temocillin, aminoglycosides, tigecycline, fosfomycin, and, rarely, fluoroquinolones or trimethoprim-sulfamethoxazole. These drugs might be considered in some specific situations. AmpC producers are resistant to cephamycins, but cefepime is an option. In the case of carbapenemase-producing Enterobacteriaceae (CPE), only some "second-line" drugs, such as polymyxins, tigecycline, aminoglycosides, and fosfomycin, may be active; double carbapenems can also be considered in specific situations. Combination therapy is associated with better outcomes for high-risk patients, such as those in septic shock or with pneumonia. Ceftazidime-avibactam was recently approved and is active against KPC and OXA-48 producers; the available experience is scarce but promising, although development of resistance is a concern. New drugs active against some CPE isolates are in different stages of development, including meropenem-vaborbactam, imipenem-relebactam, plazomicin, cefiderocol, eravacycline, and aztreonam-avibactam. Overall, therapy of MDR-E infection must be individualized according to the susceptibility profile, type, and severity of infection and the features of the patient.

Escherichia coli: an old friend with new tidings

Escherichia coli is one of the most-studied microorganisms worldwide but its characteristics are continually changing. Extraintestinal E. coli infections, such as urinary tract infections and neonatal sepsis, represent a huge public health problem. They are caused mainly by specialized extraintestinal pathogenic E. coli (ExPEC) strains that can innocuously colonize human hosts but can also cause disease upon entering a normally sterile body site. The virulence capability of such strains is determined by a combination of distinctive accessory traits, called virulence factors, in conjunction with their distinctive phylogenetic background. It is conceivable that by developing interventions against the most successful ExPEC lineages or their key virulence/colonization factors the associated burden of disease and health care costs could foreseeably be reduced in the future. On the other hand, one important problem worldwide is the increase of antimicrobial resistance shown by bacteria. As underscored in the last WHO global report, within a wide range of infectious agents including E. coli, antimicrobial resistance has reached an extremely worrisome situation that ‘threatens the achievements of modern medicine’. In the present review, an update of the knowledge about the pathogenicity, antimicrobial resistance and clinical aspects of this ‘old friend’ was presented.

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.

Clinical and molecular characteristics, risk factors and outcomes of Carbapenem-resistant Klebsiella pneumoniae bloodstream infections in the intensive care unit

Background

To analyze the clinical characteristics and outcomes of carbapenem-resistant Klebsiella pneumoniae (CRKp) and carbapenem-susceptible K. pneumoniae (CSKp) bloodstream infections (BSIs), and to study the risk factors for development of CRKp BSI and K. pneumoniae BSI-related mortality.

Methods

A retrospective case control study of patients with K. pneumoniae BSI was conducted in the intensive care unit of the First Affiliated Hospital, Medical of College, Zhejiang University from January 2013 to December 2014. Carbapenem resistance was defined in accordance with the Clinical and Laboratory Standards Institute 2016 guidelines. Risk factors for the development of CRKp BSI and risk factors for mortality due to K. pneumoniae BSI were assessed. Virulence genes were detected by polymerase chain reaction assay.

Results

In total, 48 patients were enrolled in the study, including 31 (65%) patients with CRKp BSI and 17 (35%) patients with CSKp BSI. CSKp infection was associated with more severe clinical symptoms, particularly a higher serum creatinine level (165.06 ± 127.01 in the CSKp group vs. 93.77 ± 84.35 μmol/L in the CRKp group, p = 0.039), but there was no significant difference in prognosis between the CSKp and CRKp groups. On multivariate analysis, indwelling central venous catheter (p = 0.045) was the only factor independently associated with CRKp bacteremia. However, the mortality of K. pneumoniae BSI patients was not correlated with carbapenem resistance. In addition, the isolates had diverse clonality and different origins. The frequency of detection of the allS and magA virulence genes was higher in the CSKp group than in the CRKp group (alls p = 0.04; magA p = 0.047).

Conclusions

Patients in the CSKp group experienced more severe clinical symptoms, although mortality did not differ significantly between the CRKp and CSKp groups. An indwelling central venous catheter was the only factor independently associated with CRKp BSI. The mortality of patients with K. pneumoniae BSI was not associated with carbapenem resistance. The frequency of virulence genes was higher in the CSKp group than in the CRKp group.

Can Pharmacokinetic and Pharmacodynamic Principles Be Applied to the Treatment of Multidrug-Resistant Acinetobacter?

OBJECTIVE:

To discuss treatment options that can be used for treatment of Acinetobacter infections.

DATA SOURCES:

A MEDLINE search (1966-November 2010) was conducted to identify English-language literature on pharmacotherapy of Acinetobacter and the bibliographies of pertinent articles. Programs and abstracts from infectious diseases meetings were also searched. Search terms included Acinetobacter, multidrug resistance, pharmacokinetics, pharmacodynamics, Monte Carlo simulation, nosocomial pneumonia, carbapenems, polymyxins, sulbactam, aminoglycosides, tetracyclines, tigecycline, rifampin, and fluoroquinolones.

DATA SELECTION AND DATA EXTRACTION:

All articles were critically evaluated and all pertinent information was included in this review.

DATA SYNTHESIS:

Multidrug resistant (MDR) Acinetobacter, defined as resistance to 3 or more antimicrobial classes, has increased over the past decade. The incidence of carbapenem-resistant Acinetobacter is also increasing, leading to an increased use of dose optimization techniques and/or alternative antimicrobials, which is driven by local susceptibility patterns. However, Acinetobacter infections that are resistant to all commercially available antibiotics have been reported. General principles are available to guide dose optimization of aminoglycosides, β-lactams, fluoroquinolones, and tigecycline for infections due to gram-negative pathogens. Unfortunately, data specific to patients with Acinetobacter infections are limited. Recent pharmacokinetic-pharmacodynamic information has shed light on colistin dosing. The dilemma with colistin is its concentration-dependent killing, which makes once-daily dosing seem like an attractive option, but its short postantibiotic effect limits a clinician's ability to extend the dosing interval. Localized delivery of antimicrobials is also an attractive option due to the ability to increase drug concentration at the infection site while minimizing systemic adverse events, but more data are needed regarding this approach.

CONCLUSIONS:

Increased reliance on dosage optimization, combination therapy, and localized delivery of antimicrobials are methods to pursue positive clinical outcomes in MDR Acinetobacter infections since novel antimicrobials will not be available for several years. Well-designed clinical trials with MDR Acinetobacter are needed to define the best treatment options for these patients.

Polymyxin B in combination with doripenem against heteroresistant Acinetobacter baumannii: pharmacodynamics of new dosing strategies

OBJECTIVES

Polymyxin B is being increasingly utilized as a last resort against resistant Gram-negative bacteria. We examined the pharmacodynamics of novel dosing strategies for polymyxin B combinations to maximize efficacy and minimize the emergence of resistance and drug exposure against Acinetobacter baumannii.

METHODS

The pharmacodynamics of polymyxin B together with doripenem were evaluated in time-kill experiments over 48 h against 10⁸ cfu/mL of two polymyxin-heteroresistant A. baumannii isolates (ATCC 19606 and N16870). Pharmacokinetic/pharmacodynamic relationships were mathematically modelled using S-ADAPT. A hollow-fibre infection model (HFIM) was also used to simulate clinically relevant polymyxin B dosing strategies (traditional, augmented 'front-loaded' and 'burst' regimens), together with doripenem, against an initial inoculum of 10⁹ cfu/mL of ATCC 19606.

RESULTS

In static time-kill studies, polymyxin B concentrations >4 mg/L in combination with doripenem 25 mg/L resulted in rapid bactericidal activity against both strains with undetectable bacterial counts by 24 h. The mathematical model described the rapid, concentration-dependent killing as subpopulation and mechanistic synergy. In the HFIM, the traditional polymyxin B combination regimen was synergistic, with a >7.5 log₁₀ reduction by 48 h. The polymyxin B 'front-loaded' combination resulted in more rapid and extensive initial killing (>8 log₁₀) within 24 h, which was sustained over 10 days. With only 25% of the cumulative drug exposure, the polymyxin B 'burst' combination demonstrated antibacterial activity similar to traditional and 'front-loaded' combination strategies. The polymyxin B 'front-loaded' and 'burst' combination regimens suppressed the emergence of resistance.

CONCLUSIONS

Early aggressive dosing regimens for polymyxin combinations demonstrate promise for treatment of heteroresistant A. baumannii infections.

Characteristics of superinfections during treatment with tigecycline

Tigecycline has a broad-spectrum in vitro activity against Gram-positive and Gram-negative bacteria, including multidrug-resistant (MDR) strains. However, some Gram-negative bacteria are intrinsically resistant or have reduced susceptibility to tigecycline. We performed a prospective, observational study of 43 patients who received tigecycline as the treatment for serious infections due to MDR Gram-negative microorganisms, to evaluate superinfections. In 60.5% of our patients, tigecycline-resistant (T-R) Gram-negative microorganisms were isolated, representing superinfection in 37.2% and colonization in 23.5%. Pseudomonas aeruginosa was the predominant pathogen (48.4%) followed by Providencia stuartii, Proteus mirabilis and Stenotrophomonas maltophilia. Median time elapsed between tigecycline prescription and isolation of T-R pathogens was 7 days. The 16 superinfections consisted of ventilator-associated pneumonias (43.75%), catheter-related bloodstream infections (37.5%), intra-abdominal infections (12.5%) and urinary tract infection (6.25%). Attributed mortality to superinfections was 31.25%. The comparison of various potential risk factors for isolation of T-R microorganisms did not reveal statistically significant results.

Risk Factors and Clinical Outcomes for Patients With Acinetobacter baumannii Bacteremia

Acinetobacter (A.) baumannii, an opportunistic nosocomial pathogen that can cause significant morbidity and mortality, has emerged as a worldwide problem. This study aimed to analyze the clinical features and outcomes of patients with A. baumannii bacteremia and determine the factors influencing survival by using 14-day mortality as the primary endpoint. A 6-year retrospective study of 122 cases with monomicrobial A. baumannii bacteremia was conducted in Chinese People's Liberation Army (PLA) General Hospital from January 2008 to April 2014. Predictors of 14-day mortality were identified by logistic regression analysis. The overall 14-day mortality rate was 40.2% (49 of 122 patients). Multivariable analysis revealed that independent predictors of 14-day mortality included severity of illness defined by Pitt Bacteremia Score (PBS) (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.340-0.619; P < 0.001), neutropenia (OR, 18.02; 95% CI, 1.667-194.67; P = 0.017), and malignancy (OR, 4.63; 95% CI, 1.292-16.588; P = 0.019). The effect of malignancy was influenced by neutropenia (OR for interaction term, 1.60; 95% CI, 1.15-2.22; P = 0.005). A subgroup analysis revealed that 14-day mortality rate for patients with underlying hematological malignancies and solid tumors was 75% (12/16) and 40% (12/30), respectively. Survival analysis revealed that mortality in patients with hematological malignancies was higher than that in patients with solid tumors (P = 0.032). The outcomes of patients with A. baumannii bacteremia were related to PBS, neutropenia, and malignancy. Compared with solid tumors, patients with hematological malignancies had a higher mortality in the setting of A. baumannii bacteremia.

Multidrug-Resistant Gram-Negative Bacterial Infections in the Hospital Setting: Overview, Implications for Clinical Practice, and Emerging Treatment Options

The increasing prevalence of infections due to multidrug-resistant (MDR) gram-negative bacteria constitutes a serious threat to global public health due to the limited treatment options available and the historically slow pace of development of new antimicrobial agents. Infections due to MDR strains are associated with increased morbidity and mortality and prolonged hospitalization, which translates to a significant burden on healthcare systems. In particular, MDR strains of Enterobacteriaceae (especially Klebsiella pneumoniae and Escherichia coli), Pseudomonas aeruginosa, and Acinetobacter baumannii have emerged as particularly serious concerns. In the United States, MDR strains of these organisms have been reported from hospitals throughout the country and are not limited to a small subset of hospitals. Factors that have contributed to the persistence and spread of MDR gram-negative bacteria include the following: overuse of existing antimicrobial agents, which has led to the development of adaptive resistance mechanisms by bacteria; a lack of good antimicrobial stewardship such that use of multiple broad-spectrum agents has helped perpetuate the cycle of increasing resistance; and a lack of good infection control practices. The rising prevalence of infections due to MDR gram-negative bacteria presents a significant dilemma in selecting empiric antimicrobial therapy in seriously ill hospitalized patients. A prudent initial strategy is to initiate treatment with a broad-spectrum regimen pending the availability of microbiological results allowing for targeted or narrowing of therapy. Empiric therapy with newer agents that exhibit good activity against MDR gram-negative bacterial strains such as tigecycline, ceftolozane-tazobactam, ceftazidime-avibactam, and others in the development pipeline offer promising alternatives to existing agents.

Tigecycline treatment causes a decrease in fibrinogen levels

The objective of this study was to assess the impact of tigecycline treatment on coagulation parameters, specifically fibrinogen, in patients with severe infections. We examined 20 cases of tigecycline-treated patients with severe infections, including hospital-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, and bloodstream infections. We monitored the relative markers of coagulation and renal and liver function before, during, and after treatment. Fibrinogen (FIB) levels decreased significantly after the use of tigecycline and normalized after the cessation of treatment. FIB levels significantly decreased in the patients treated with the recommended dose or a higher treatment dose. The FIB levels decreased more in the higher-treatment-dose group. There was no difference in the decrease in FIB levels or the FIB level recovery by age. Prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT) were prolonged after tigecycline use. The TT decreased after the cessation of treatment, and the PT and APTT also decreased but not to a significant level. There was no change in platelet, alanine aminotransferase (ALT), or creatinine (Cr) levels associated with treatment. The use of tigecycline was associated with decreased FIB levels, which returned to normal after the cessation of treatment. A high-dose treatment group showed greater decreases in FIB levels than did patients treated with the recommended dose. The decline in FIB was not related to patient age. The use of tigecycline was associated with prolonged PT, APTT, and TT.

In vitro potential of Lycosin-I as an alternative antimicrobial drug for treatment of multidrug-resistant Acinetobacter baumannii infections

The resistance of multidrug-resistant Acinetobacter baumannii (MDRAB) isolates to most traditional antibiotics results in huge challenges for infection therapy. We investigated the in vitro activities of both l- and d-lycosin-I against MDRAB. These two compounds displayed high antibacterial activities and rapid bactericidal effects against MDRAB. Moreover, the compounds retained their activity even at high salt (Mg(2+) or Ca(2+)) concentrations. These results demonstrate the potential of lycosin-I to be developed as a new antibiotic.

Tigecycline use in critically ill patients: a multicentre prospective observational study in the intensive care setting

PURPOSE

This prospective observational study aimed at describing prescription patterns of tigecycline and patient outcomes in 26 French intensive care units (ICU).

METHODS

Data of consecutive cases of adult patients treated with tigecycline were collected from the initiation until 7 days after the end of treatment. Response to treatment was classified as success, failure or undetermined and analyses were presented according to severity (SOFA score <7 or ≥7). Survival was recorded at 28 days.

RESULTS

A total of 156 patients were included (64% male, age 60 ± 15 years). At inclusion, 53% had a SOFA score ≥7; 93% had received prior anti-infective agents. Tigecycline was given as first-line treatment in 47% of patients, mostly in combination (67%), for intra-abdominal (IAI 56%), skin and soft tissue (SSTI 19%) or other infections. A total of 76% of the treated infections were hospital-acquired. Bacteraemia was reported in 12% of patients. Median treatment duration was 9 days. Tigecycline was prematurely stopped in 42% patients. The global success rate was 60% at the end of treatment, and significantly higher with treatment duration more than 9 days (76 vs. 47%, P < 0.001). Success rate was 65% for patients alive at the end of treatment. Success rates tended to decrease with illness severity, immunosuppression, bacteraemia and obesity. Survival rate at day 28 was 85% in the whole cohort and significantly higher in the less severely ill patients (P < 0.001).

CONCLUSIONS

Tigecycline success rates appear comparable to those reported in clinical studies in ICU with severe infections. Tigecycline could be an alternative in ICU patients.

Methicillin-resistant Staphylococcus aureus infection epidemiology and clinical response from tigecycline soft tissue infection trials

Given increasing resistance, therapeutic options to treat MRSA soft tissue infections should be evaluated. This pooled analysis evaluated data from subjects enrolled in 6 tigecycline clinical trials with documented MRSA complicated skin and skin structure infections or diabetic foot infections (DFIs). Baseline characteristics were compared between subjects with and without molecularly classified community-acquired (CA) MRSA, specifically staphylococcal cassette chromosome mec (SCCmec) IV. Clinical response was compared by CA-MRSA designation and treatment group. A total of 378 subjects with MRSA soft tissue infections were identified, including 79 with DFI. A total of 249 (65.9%) were molecularly classified as CA-MRSA. Clinical response rates for MRSA soft tissue infection were similar between tigecycline and vancomycin (treatment difference, 1.0%; 95% confidence interval: -9.3, 12.0) as well as by infection type, SCCmec, and Panton-Valentine leukocidin (PVL) status. Tigecycline demonstrated comparable efficacy for treatment of MRSA soft tissue infections regardless of infection type, SCCmec, or PVL status.

Prescription behaviours for tigecycline in real-life clinical practice from five European observational studies

OBJECTIVES

There is limited information on the use of tigecycline in real-life clinical practice. This analysis aims to identify and understand tigecycline prescribing patterns and associated patient outcomes for approved indications.

PATIENTS AND METHODS

A pooled analysis of patient-level data collected on the prescription of tigecycline in five European observational studies (July 2006 to October 2011) was conducted.

RESULTS

A total of 1782 patients who received tigecycline were included in the analysis. Of these patients, 61.6% were male, the mean age was 63.4 ± 14.7 years, 56.4% were in intensive care units, 80.2% received previous antibiotic treatment and 91% had one or more comorbid conditions. The mean Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores at the beginning of treatment were 17.7 ± 7.9 and 7.0 ± 4.0, respectively. The majority of patients (58.3%) received tigecycline for treatment of complicated skin and soft-tissue infections (cSSTIs; n = 254) or complicated intra-abdominal infections (cIAIs; n = 785). Tigecycline was given at the standard dose (100 mg plus 50 mg twice daily) to 89.3% of patients for a mean duration of 11.1 ± 6.4 days. The main reasons for prescribing tigecycline were failure of previous therapy (46.1%), broad-spectrum antibiotic coverage (41.4%) and suspicion of a resistant pathogen (39.3%). Tigecycline was prescribed first-line in 36.3% of patients and as monotherapy in 50.4%. Clinical response rates to treatment with tigecycline alone or in combination were 79.6% (183/230; cSSTIs) and 77.4% (567/733; cIAIs).

CONCLUSIONS

Although tigecycline prescription behaviour showed some heterogeneity across the study sites, these results confirm a role for tigecycline in real-life clinical practice for the treatment of complicated infections, including those in critically ill patients, across Europe.

Tigecycline therapy for infections due to carbapenemase-producing Klebsiella pneumoniae in critically ill patients

BACKGROUND

The aim of this study was to assess the efficacy of tigecycline in the treatment of infections due to carbapenemase-producing Klebsiella pneumoniae (CPKP) in critically ill patients.

METHODS

A retrospective observational study was conducted in critically ill patients receiving different tigecycline doses for severe CPKP infections. We evaluated demographic data, localization and severity of infection, response to therapy, and mortality.

RESULTS

Fifteen patients received tigecycline for 16 episodes of CPKP infection. The main infections were pneumonia (31%), urinary tract infection (31%), peritonitis (20%), catheter-related bacteraemia (12%), and meningitis (6%). Most infections were complicated with severe sepsis (44%), septic shock (12%), and/or bacteraemia (19%). The daily maintenance dose of tigecycline was 200 mg in 10 episodes and 100 mg in 6 episodes. The overall 30-day mortality rate was 25%. Univariate analysis showed that mortality was significantly associated (p < 0.01) with mean APACHE II and SOFA scores and the presence of immunosuppression, but not with the tigecycline dose.

CONCLUSIONS

Tigecycline appears to be an effective therapy for severe infections due to CPKP in critically ill patients. Mortality is related to the severity of the underlying disease. We observed no benefit from a higher maintenance dose of tigecycline, although the number of patients included in the study was too small to draw any general conclusions in this regard.

[Lower respiratory tract infections related to Stenotrophomonas maltophilia and Acinetobacter baumannii]

Stenotrophomonas maltophilia and Acinetobacter baumannii are both non-fermenting ubiquitous Gram-negative bacilli. The incidence of lower respiratory tract infections related to these microorganisms is increasing, especially in intensive care units. Their capacity to acquire resistance against several antimicrobials is challenging for clinicians and microbiologists. Despite their low virulence, these pathogens are responsible for colonization and infection in patients with comorbidities, immunosuppression, and critically ill patients. S. maltophilia and A. baumannii are mainly identified in nosocomial infections: ventilator-associated pneumonia, bacteremia and surgical wound infection. Infections related to these microorganism are associated with high mortality and morbidity. Trimethoprime-sulfamethoxazole and carbapenem are the first line treatment for infections related to S. maltophilia and A. baumannii respectively. However, the increasing rate of resistance against these agents results in difficulties in treating patients with infections related to these pathogens. New antimicrobial agents and further randomized studies are needed to improve the treatment of these infections. Prevention of spared of these multidrug-resistant bacteria is mandatory, including hand-hygiene, environment cleaning, and limited usage of large spectrum antibiotics.

Patients enrolled in randomised clinical trials are not representative of critically ill patients in clinical practice: observational study focus on tigecycline

It is being increasingly recognised by clinicians and scientists that participants in randomised clinical trials (RCTs) of antibiotics of last resort do not represent the patients who will later be treated with these drugs. Data on this subject are limited and have not been investigated systematically. This observational study aimed to examine this hypothesis quantitatively, using the example of tigecycline. To evaluate the influence of recruitment, patients eligible for clinical trials were retrospectively compared with ineligible patients regarding baseline and clinical characteristics as well as outcome parameters, e.g. length of hospital stay, intensive care unit (ICU) stay, ventilation and mortality. The clinical characteristics of 187 patients illustrated differences in the nature and severity of disease, co-morbidities and outcome. Eligible and ineligible patients differed in a number of parameters, e.g. median APACHE II score (15.5 vs. 28.0), number of liver transplantations (5% vs. 18%; P=0.048), septic shock (21% vs. 49%; P=0.001), need for mechanical ventilation (30% vs. 79%; P<0.001), mean length of ICU stay (19.3 days vs. 40.7 days) and death (19% vs. 46%; P=0.001). Critically ill patients were under-represented in clinical trials. Moreover, only a minority of patients in clinical practice (13%) were potentially eligible for a pivotal RCT. The disparities likely result from strict exclusion criteria in RCTs and recruitment bias. These data emphasise the importance of including critically ill patients in RCTs of antibiotics against multiresistant bacteria in order to account for those who will later be treated.

Clinical outcomes of tigecycline alone or in combination with other antimicrobial agents for the treatment of patients with healthcare-associated multidrug-resistant Acinetobacter baumannii infections

Tigecycline (TG) has been shown to be active in vitro against Acinetobacter baumannii, although data on the clinical efficacy of TG alone or in combination for the treatment of infections due to multidrug-resistant A. baumannii (MDRAB) remain limited. The purpose of this study was to investigate the clinical outcomes of patients with healthcare-associated infections (HAIs) caused by MDRAB who were treated with imipenem/cilastatin and sulbactam, and TG alone or in combination with other antibiotics. A total of 386 patients with HAIs caused by MDRAB were retrospectively analyzed and grouped into TG and non-TG groups, depending on whether they received TG treatment. Of the 266 patients in the TG group, 108 were treated with TG alone and 158 were treated with TG in combination with ceftazidime, ceftriaxone, piperacillin/tazobactam, or a carbapenem. All 120 patients in the non-TG group were treated with imipenem/cilastatin and sulbactam. The primary outcome measure was 30-day mortality after TG treatment and the secondary outcome was clinical outcome. There were no significant differences in survival rates between the two groups. However, the rate of unfavorable outcome was significantly lower (p < 0.05) among patients in the TG group than among patients in the non-TG group. The most significant predictor of unfavorable outcome was sepsis, whereas TG treatment and microbial eradication were the most significant predictors of favorable outcomes. Our study represents the largest study of patients with MDRAB infection treated with TG and expands our understanding of the role of TG therapy alone or in combination with other agents for the treatment of HAI caused by MDRAB.

Tigecycline: an update

Tigecycline is a broad-spectrum antibiotic with activity against difficult-to-treat pathogens such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., Acinetobacter baumannii, and Gram-negative bacterial strains that produce extended-spectrum β-lactamases. Minimal organ toxicity and lack of dosage adjustment in most patients are important considerations for tigecycline use. Tigecycline has been shown to be as effective and safe as standard antimicrobial therapy for treatment of adults with complicated intra-abdominal infections, complicated skin and skin structure infections, and community-acquired bacterial pneumonia. The clearest applications of tigecycline are for on-label indications. Whether tigecycline should be utilized as therapy for other infections including hospital-acquired infections with a high likelihood of multidrug-resistant pathogens is a complex issue that requires ongoing assessment. This article offers an updated overview of tigecycline clinical studies, current microbial resistance patterns, pharmacokinetic/pharmacodynamic investigations, and safety analyses.

Tigecycline in carbapenem-resistant Acinetobacter baumannii bacteraemia: susceptibility and clinical outcome

Although tigecycline is considered one of the few therapeutic options for carbapenem-resistant Acinetobacter baumannii (CRAB) bacteraemia, its role in the treatment of CRAB bacteraemia remains unclear. We describe the clinical outcomes of 9 patients who received tigecycline for CRAB bacteraemia. Although all CRAB blood isolates were susceptible to tigecycline, 5 (56%) deaths were related to CRAB bacteraemia and 1 case of breakthrough CRAB bacteraemia was observed during tigecycline therapy. Clinical outcomes of tigecycline therapy may be poor in patients with tigecycline-susceptible CRAB bacteraemia, although multiple factors including delayed treatment could contribute to the poor outcomes.

Therapy of 1,025 severely ill patients with complicated infections in a German multicenter study: safety profile and efficacy of tigecycline in different treatment modalities

This large prospective non-interventional study investigated the effects of tigecycline either as single agent or in combination with other antimicrobial agents in 1,025 patients treated in clinical routine at German hospitals. Sixty-five percent of the patients had APACHE II scores > 15, indicating high overall disease severity. Complicated intra-abdominal infections (cIAI) or complicated skin and skin tissue infections (cSSTI) were the most common indications, with Staphylococcus aureus, Enterococcus faecium and Escherichia coli being the most frequently isolated pathogens. Clinical success was reported at the end of tigecycline therapy in 74.2% of the total population, in 75.4% of the cIAI and in 82.2% of the cSSTI patients. The subpopulation (28.0% of the patients) infected with multidrug-resistant pathogens (methicillin-resistant S. aureus, extended-spectrum β-lactamase producers and vancomycin-resistant enterococci) were treated with similar success rates as the overall population. Tigecycline was generally well tolerated. Drug-related adverse events (AEs) were reported in 7.7% of the total population; 2.5% had serious AEs mostly attributable to inefficacy of therapy or deterioration of the disease. Mortality rates were consistent with the types of infection and severity of illness. There was no indication of excessive mortality associated with tigecycline as had been suggested in previously performed meta-analyses. In this large non-interventional study performed in the clinical routine setting, tigecycline achieved favorable clinical success rates in a patient population with high severity of illness and a high prevalence of multidrug-resistant pathogens and showed a good safety and tolerability profile.

White paper: recommendations on the conduct of superiority and organism-specific clinical trials of antibacterial agents for the treatment of infections caused by drug-resistant bacterial pathogens

There is a critical need for new pathways to develop antibacterial agents to treat life-threatening infections caused by highly resistant bacteria. Traditionally, antibacterial agents have been studied in noninferiority clinical trials that focus on one site of infection (eg, pneumonia, intra-abdominal infection). Conduct of superiority trials for infections caused by highly antibiotic-resistant bacteria represents a new, and as yet, untested paradigm for antibacterial drug development. We sought to define feasible trial designs of antibacterial agents that could enable conduct of superiority and organism-specific clinical trials. These recommendations are the results of several years of active dialogue among the white paper's drafters as well as external collaborators and regulatory officials. Our goal is to facilitate conduct of new types of antibacterial clinical trials to enable development and ultimately approval of critically needed new antibacterial agents.

Global spread of drug-resistant Acinetobacter baumannii: molecular epidemiology and management of antimicrobial resistance

Acinetobacter baumannii is an opportunistic Gram-negative pathogen with increasing relevance in a variety of hospital-acquired infections especially among intensive care unit patients. Resistance to antimicrobial agents is the main reason for A. baumannii spread. A. baumannii outbreaks described worldwide are caused by a limited number of genotypic clusters of multidrug-resistant strains that successfully spread among hospitals of different cities and countries. In this article, we will focus on the mechanisms responsible for resistance to antimicrobials and disinfectants in A. baumannii and the epidemiology of drug-resistant A. baumannii in healthcare facilities. We will also discuss the therapeutic and infection control strategies for management of drug-resistant A. baumannii epidemics.

Outcomes in patients infected with carbapenem-resistant Acinetobacter baumannii and treated with tigecycline alone or in combination therapy

PURPOSE

Acinetobacter baumannii is a non-fermenting aerobic gram-negative bacteria and one of the important nosocomial pathogens, especially in intensive care units (ICUs). In recent years, multidrug-resistant (MDR) isolates have been an emerging problem, with limited therapeutic options. Tigecycline is a novel antimicrobial, with its in vitro activity against most gram-positive and gram-negative pathogens.

METHODS

This is a retrospective study that was conducted in a tertiary care hospital with 550 beds in Ankara, Turkey, from January 2009 to July 2010. Thirty-three patients who had carbapenem-resistant Acinetobacter spp. infections and received tigecycline alone or in combination with other antibiotics for at least 3 days were included.

RESULTS

The median age of the patients was 62 (18-87) years. All of the patients were diagnosed and treated in the ICU. Clinical responses were observed in 23 patients (69.7%). Ten patients (30%) had clinical failure. There was no significant difference between ventilator-associated pneumonia (VAP) and bloodstream infection (BSI) in terms of clinical or microbiological outcome (p > 0.05). The microbiological response rate was 50%. Superinfection was detected in 13 patients (43.3%) and Pseudomonas aeruginosa was the most frequently isolated pathogen. The 30-day overall mortality rate and attributable mortality rates were 57.6 and 24.2%, respectively. The attributable mortality rate was higher in the group in which microbiological eradication was not provided.

CONCLUSIONS

Although it is approved by the Food and Drug Administration (FDA) for the treatment of complicated intra-abdominal infections, complicated skin and soft tissue infections, and community-acquired bacterial pneumonia, emerged resistance of Acinetobacter spp. and limited therapeutic options left physicians no choice but to use tigecycline for off-label indications.

Efficacy and safety of tigecycline for the treatment of infectious diseases: a meta-analysis

BACKGROUND

Multidrug resistance among bacteria increases the need for new antimicrobial drugs with high potency and stability. Tigecycline is one candidate drug, and a previous meta-analysis of only published randomised controlled trials suggested that it might as effective as comparator treatments; we did a meta-analysis to include new and unpublished trials to assess its efficacy for the treatment of adult patients with serious bacterial infection.

METHODS

We searched PubMed, Cochrane Central Register, and Embase up to March 30, 2011, to identify published studies, and we searched clinical trial registries to identify completed unpublished studies, the results of which were obtained through the manufacturer. Eligible studies were randomised trials assessing the clinical efficacy, safety, and eradication efficiency of tigecycline versus other antimicrobial agents for any bacterial infection. The primary outcome was treatment success in patients who received at least one dose of the study drug, had clinical evidence of disease, and had complete follow-up (the clinically assessable population). Meta-analysis was done with random-effects models because of heterogeneity across the trials.

FINDINGS

14 randomised trials, comprising about 7400 patients, were included. Treatment success was lower with tigecycline than with control antibiotic agents, but the difference was not significant (odds ratio 0·87, 95% CI 0·74-1·02). Adverse events were more frequent in the tigecycline group than in the control groups (1·45, 1·11-1·88), with significantly more vomiting and nausea. All-cause mortality was higher in the tigecycline group than in the comparator groups, but the difference was not significant (1·28, 0·97-1·69). Eradication efficiency did not differ between tigecycline and control regimens, but the sample size for these comparisons was small.

INTERPRETATION

Tigecycline is not better than standard antimicrobial agents for the treatment of serious infections. Our findings show that assessment with unpublished studies is needed to make appropriate decisions about new agents.

FUNDING

None.

Review of macrolides (azithromycin, clarithromycin), ketolids (telithromycin) and glycylcyclines (tigecycline)

The advanced macrolides, azithromycin and clarithromycin, and the ketolide, telithromycin, are structural analogs of erythromycin. They have several distinct advantages when compared with erythromycin, including enhanced spectrum of activity, more favorable pharmacokinetics and pharmacodynamics, once-daily administration, and improved tolerability. Clarithromycin and azithromycin are used extensively for the treatment of respiratory tract infections, sexually transmitted diseases, and Helicobacter pylori-associated peptic ulcer disease. Telithromycin is approved for the treatment of community-acquired pneumonia. Severe hepatotoxicity has been reported with the use of telithromycin.

Efficacy and safety of tigecycline: a systematic review and meta-analysis

BACKGROUND

Tigecycline is a novel glycylcycline that exhibits broad-spectrum antibacterial activity. Recently, the US FDA issued a warning concerning increased mortality with tigecycline in randomized controlled trials (RCTs).

METHODS

We conducted a systematic review and meta-analysis of RCTs that compared tigecycline with any other antibiotic regimen for the treatment of any infection. A comprehensive search, without publication status or other restrictions, was conducted. The primary outcome was overall 30 day mortality. The secondary outcome included clinical and microbiological failure, superinfections and adverse events (AEs). The trials' risks of bias and their effects on results were assessed. Two reviewers independently extracted the data. Individual trials' relative risks (RRs) were pooled using a fixed effect meta-analysis.

RESULTS

Fifteen trials (7654 patients) were included. Overall mortality was higher with tigecycline compared with other regimens [RR 1.29, 95% confidence interval (CI) 1.02-1.64, without heterogeneity]. The type of infection assessed and the trials' reported risks of bias did not affect this result. Clinical failure was significantly higher with tigecycline (RR 1.16, 95% CI 1.06-1.27) and non-statistically significant higher rates of microbiological failure were demonstrated (RR 1.13, 95% CI 0.99-1.30). Development of septic shock was significantly more frequent with tigecycline (RR 7.01, 95% CI 1.27-38.66). Superinfections were significantly more common with tigecycline and so were AEs, including all AEs and AEs requiring discontinuation.

CONCLUSIONS

In the light of the increased mortality, probably explained by decreased clinical and microbiological efficacy, clinicians should avoid tigecycline monotherapy in the treatment of severe infections and reserve it as a last-resort drug.

Potential role of tigecycline in the treatment of community-acquired bacterial pneumonia

Tigecycline is a member of the glycylcycline class of antimicrobials, which is structurally similar to the tetracycline class. It demonstrates potent in vitro activity against causative pathogens that are most frequently isolated in patients with community-acquired bacterial pneumonia (CABP), including (but not limited to) Streptococcus pneumoniae (both penicillin-sensitive and -resistant strains), Haemophilus influenzae and Moraxella catarrhalis (including β-lactamase-producing strains), Klebsiella pneumoniae, and ‘atypical organisms’ (namely Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila). Comparative randomized clinical trials to date performed in hospitalized patients receiving tigecycline 100 mg intravenous (IV) × 1 and then 50 mg IV twice daily thereafter have demonstrated efficacy and safety comparable to the comparator agent. Major adverse effects were primarily gastrointestinal in nature. Tigecycline represents a parenteral monotherapy option in hospitalized patients with CABP (especially in patients unable to receive respiratory fluoroquinolones). However, alternate and/or additional therapies should be considered in patients with more severe forms of CABP in light of recent data of increased mortality in patients receiving tigecycline for other types of severe infection.