Optimal tigecycline dosage regimen is urgently needed: results from a pharmacokinetic/pharmacodynamic analysis of tigecycline by Monte Carlo simulation

Serum concentration threshold and risk factors of tigecycline-induced hypofibrinogenaemia in critically ill patients

OBJECTIVES

Hypofibrinogenaemia is a serious adverse reaction associated with tigecycline (TGC) therapy and may lead to the discontinuation of the treatment. This study aimed to explore the relevant factors of TGC-induced hypofibrinogenaemia and determine the thresholds of serum concentration as a predictive indicator of TGC-induced hypofibrinogenaemia.

METHODS

A retrospective single-centre study was conducted on patients with severe infection who were treated with TGC. Clinical data and serum concentration parameters were extracted from the electronic medical records of these patients. Patients were divided into the hypofibrinogenaemia group (< 2.0 g/L) and the normal fibrinogen group (≥ 2.0 g/L) in order to evaluate risk factors associated with TGC-induced hypofibrinogenaemia. Logistic regression analysis and receiver operating characteristic curves were utilized to identify the risk factors associated with TGC-induced hypofibrinogenaemia and to establish plasma concentration thresholds as predictive indicators.

RESULTS

A total of 114 patients were enrolled in this study, with 59.6% experiencing hypofibrinogenaemia. The multivariate regression analysis indicated that baseline fibrinogen level, trough concentration (Cmin), peak concentration (Cmax), the concentration at 6 h after the dosing (C6h) and the area under the concentration-time curve over a 24-h period (AUC0-24) were significantly associated with hypofibrinogenaemia (P < 0.05). Furthermore, it was found that AUC0-24 is the optimal predictor of TGC-induced hypofibrinogenaemia. The optimal cut-off for the AUC0-24 of TGC in ICU patients was determined to be 17.03 mg h/L.

CONCLUSIONS

TGC exposure is highly predictive of TGC-induced hypofibrinogenaemia. We recommend closely monitoring plasma concentrations of TGC in patients to ensure patient efficacy and safety.

Population pharmacokinetics and individualized dosing of tigecycline for critically ill patients: a prospective study with intensive sampling

Background: Due to the heterogeneity of critically ill patients, the pharmacokinetics of tigecycline are unclear, and the optimal dosing strategy is controversial. Methods: A single-center prospective clinical study that included critically ill patients who received tigecycline was performed. Blood samples were intensively sampled (eight samples each), and plasma drug concentrations were determined. A population pharmacokinetic (PPK) model was developed and evaluated by goodness-of-fit plots, bootstrap analysis and visual predictive checks. Monte Carlo simulation was conducted to optimize the dosage regimen. Results: Overall, 751 observations from 98 patients were included. The final PPK model was a two-compartment model incorporating covariates of creatinine clearance on clearance (CL), body weight on both central and peripheral volumes of distribution (V1 and V2), γ-glutamyl transferase and total bilirubin on intercompartment clearance (Q), and albumin on V2. The typical values of CL, Q, V1 and V2 were 3.09 L/h, 39.7 L/h, 32.1 L and 113 L, respectively. A dosage regimen of 50 mg/12 h was suitable for complicated intra-abdominal infections, but 100 mg/12 h was needed for community-acquired pneumonia, skin and skin structure infections and infections caused by less-susceptive bacteria. Conclusion: The Tigecycline PPK model was successfully developed and validated. Individualized dosing of tigecycline could be beneficial for critically ill patients.

Pharmacokinetic/Pharmacodynamic Target Attainment of Tigecycline in Patients with Hepatic Impairment in a Real-World Setting

BACKGROUND

This study aimed to investigate the pharmacokinetic/pharmacodynamic (PK/PD) target attainment of various tigecycline dosing regimens in real-world patients with impaired liver function.

METHODS

The clinical data and serum concentrations of tigecycline were extracted from the patients' electronic medical records. Patients were classified into Child-Pugh A, Child-Pugh B, and Child-Pugh C groups, according to the severity of liver impairment. Furthermore, the minimum inhibition concentration (MIC) distribution and PK/PD targets of tigecycline from the literature were used to obtain a proportion of PK/PD targets attainment of various tigecycline dosing regimens at different infected sites.

RESULTS

The pharmacokinetic parameters revealed significantly higher values in moderate and severe liver failure (groups Child-Pugh B and Child-Pugh C) than those in mild impairment (Child-Pugh A). Considering the target area under the time-concentration curve (AUC 0-24 )/MIC ≥4.5 for patients with pulmonary infection, most patients with high-dose (100 mg, every 12 hours) or standard-dose (50 mg, every 12 hours) for tigecycline achieved the target in groups Child-Pugh A, B, and C. Considering the target AUC 0-24 /MIC ≥6.96 for patients with intra-abdominal infection, when MIC ≤1 mg/L, more than 80% of the patients achieved the target. For an MIC of 2-4 mg/L, only patients with high-dose tigecycline in groups Child-Pugh B and C attained the treatment target. Patients experienced a reduction in fibrinogen values after treatment with tigecycline. In group Child-Pugh C, all 6 patients developed hypofibrinogenemia.

CONCLUSIONS

Severe hepatic impairment may attain higher PK/PD targets, but carries a high risk of adverse reactions.

Rational use of tigecycline and tigecycline blood concentration monitoring in patients with severe infection

Tigecycline, a tetracycline antibiotic, is widely used against antimicrobial resistance; therefore, medical staff should use tigecycline rationally to improve clinical efficacy and reduce resistance to this drug. The present study aimed to enhance the rate of rational tigecycline usage. The patients were divided into a low-dose (50 mg tigecycline twice daily, every 12 h) and a high-dose group (100 mg twice daily, every 12 h). The blood concentrations of tigecycline were examined and the area under the curve (AUC)_{0-12 h} values of the two groups were calculated. Prescriptions of tigecycline for 40 intensive care unit (ICU) cases were reviewed to evaluate the rationality of tigecycline usage. The peak plasma concentrations (the 7th administration after 1 h) of tigecycline were significantly higher in the high-dose group (2.46±0.43 µg/ml) compared with those in the low-dose group (1.25±0.16 µg/ml). The AUC_{0-12 h} was 16.35±3.09 h µg/ml in the high-dose group and 9.83±1.23 h µg/ml in the low-dose group (P<0.001). There were 29 irrational prescriptions identified, involving: i) Lack of consultation records (n=20); ii) inappropriate usage or dosage (n=17); iii) inappropriate drug selection (n=2); or iv) lack of dynamic laboratory tests to evaluate the efficacy (n=4). The irrational use of tigecycline in ICU patients is common. The rate of rational tigecycline usage can be improved by strengthening the management, training and participation of clinical pharmacists.

Tigecycline Pharmacokinetic and Pharmacodynamic Profile in Patients with Chronic Obstructive Pulmonary Disease Exacerbation

BACKGROUND

We aimed to evaluate the pharmacokinetic profile of tigecycline in plasma and its penetration to sputum in moderately ill patients with an infectious acute exacerbation of chronic obstructive pulmonary disease (COPD).

METHODS

Eleven patients hospitalized with acute respiratory failure due to an acute COPD exacerbation with clinical evidence of an infectious cause received tigecycline 50 mg twice daily after an initial loading dose of 100 mg. Blood and sputum samples were collected at steady state after dose seven.

RESULTS

In plasma, mean C_max pl was 975.95 ± 490.36 ng/mL and mean C_min pl was 214.48 ±140.62 ng/mL. In sputum, mean C_{max sp} was 641.91 ± 253.07 ng/mL and mean C_{min sp} was 308.06 ± 61.7 ng/mL. In plasma, mean AUC _{0-12 pl} was 3765.89 ± 1862.23 ng*h/mL, while in sputum mean AUC _{0-12 sp} was 4023.27 ± 793.37 ng*h/mL. The mean penetration ratio for the 10/11 patients was 1.65 ± 1.35. The mean Free AUC_{0-24 pl}/MIC ratio for Streptococcus pneumoniae and Haemophilus influenzae was 25.10 ± 12.42 and 6.02 ± 2.97, respectively.

CONCLUSIONS

Our findings support the clinical effectiveness of tigecycline against commonly causative bacteria in COPD exacerbations and highlight its sufficient lung penetration in pulmonary infections of moderate severity.

Measurement of tigecycline in dried blood spots by LC-MS/MS and comparison tigecycline concentrations between whole blood and plasma

RATIONALE

An LC-MS/MS method was established to measure tigecycline in dried blood spots (DBSs).

METHODS

The DBS specimens obtained by applying 30 μl of blood to filter paper were extracted with hydrogen oxide and subsequently precipitated protein with perchloric acid, then the extract was directly analyzed by liquid chromatography tandem mass spectrometry. A Hypersil GOLD aQ column was utilized for separating the analytes, and detection was carried out in positive and selective reaction monitoring modes. The precursors to product ion transitions m/z 586.3 → 513.1 and m/z 586.3 → 569.2 were monitored for tigecycline, and m/z 473.2 → 456.0 and m/z 473.2 → 367.0 for 9-amino minocycline as internal standard.

RESULTS

The validation parameters of specificity and selectivity, linearity (0.02-5 μg ml^-1 ), sensitivity (limit of quantification 0.02 μg ml^-1 ), intra- and interday precision (within 15%) and relative error (within ±15%) were acceptable. The recoveries were from 84.65% to 90.49% and from 85.41% to 95.72% for tigecycline and internal standard, respectively, and the matrix effect was not evident to influence accuracy. The impact of hematocrit on measurement of the analyte was negligible, and after preserving at ambient temperature for 24 h and at 4°C for 1 month it remained steady.

CONCLUSIONS

The advantages of nonintrusive blood collection and micro-volume sample requirements make DBS a potent surrogate to conventional venepuncture for sampling.

Serum concentration as a predictor of tigecycline-induced hypofibrinogenemia in critically ill patients: a retrospective cohort study

OBJECTIVES

The objective of this study was to determine the thresholds of serum concentration as a predictor of tigecycline-induced hypofibrinogenemia in critically ill patients.

METHODS

A retrospective cohort study was conducted in ICU patients treated with tigecycline. The clinical data and serum concentration were extracted from the patients' electronic medical records. Patients were divided into hypofibrinogenemia (HF) group and normal group according to fibrinogen (FIB) value. The receiver operating characteristic (ROC) curves and logistic regression was used to derive serum concentration thresholds and quantify the association between exposure thresholds and hypofibrinogenemia while adjusting for confounders.

RESULTS

In total, 100 patients were included. ROC curves analyse showed that tigecycline concentration parameters were strongly predictive of hypofibrinogenemia. Adjusting for duration of tigecycline, C_1/2 ≥ 0.645 mg/L, AUC_0-24 ≥ 20.76 mg∙h/L and C_min ≥ 0.455mg/L were associated with a 3- to 5-fold increased risk of tigecycline-induced hypofibrinogenemia in logistic regression.

CONCLUSION

The findings from this study provide evidence that tigecycline exposure is highly predictive of hypofibrinogenemia, with approximately 3- to 5-fold increased risk. C_1/2 ≥ 0.645 mg/L with best area under ROC curve and NPV appears to be the most appropriate toxicity threshold.

Tigecycline Dosing Strategies in Critically Ill Liver-Impaired Patients

This study investigated tigecycline exposure in critically ill patients from a population pharmacokinetic perspective to support rational dosing in intensive care unit (ICU) patients with acute and chronic liver impairment. A clinical dataset of 39 patients served as the basis for the development of a population pharmacokinetic model. The typical tigecycline clearance was strongly reduced (8.6 L/h) as compared to other populations. Different models were developed based on liver and kidney function-related covariates. Monte Carlo simulations were used to guide dose adjustments with the most predictive covariates: Child–Pugh score, total bilirubin, and MELD score. The best performing covariate, guiding a dose reduction to 25 mg q12h, was Child–Pugh score C, whereas patients with Child–Pugh score A/B received the standard dose of 50 mg q12h. Of note, the obtained 24 h steady-state area under the concentration vs. time curve (AUCss) range using this dosing strategy was predicted to be equivalent to high-dose tigecycline exposure (100 mg q12h) in non-ICU patients. In addition, 26/39 study participants died, and therapy failure was most correlated with chronic liver disease and renal failure, but no correlation between drug exposure and survival was observed. However, tigecycline in special patient populations needs further investigations to enhance clinical outcome.

Risk factors for infection and mortality caused by carbapenem-resistant Klebsiella pneumoniae: a large multicentre case-control and cohort study

OBJECTIVES

To elucidate the predictors of carbapenem-resistant Klebsiella pneumoniae (CRKP) infection and help clinicians better identify CRKP infection at an early age.

METHODS

We conducted a multicentre case-control study of 422 patients with CRKP infection and 948 with carbapenem-susceptible K. pneumoniae (CSKP) infection from March to July 2017. Binary logistic regression was used to identify risk factors for CRKP infection. The subgroups of CRKP respiratory infection, intra-abdominal infection, and bloodstream infection were also evaluated. Patients were followed up for 28 days. Independent risk factors for 28-day crude mortality of CRKP infection were analysed using Cox proportional hazards regression models.

RESULTS

Longer stay of hospitalization, stay in the ICU, previous exposure to antibacterial agents (especially carbapenems, quinolones, aminoglycosides, and tigecycline), invasive procedures, intravascular catheter use, tracheotomy, or admission to ICU in the preceding 90 days were risk factors for CRKP infection. Carbapenem exposure was the only common predictor of different types of CRKP infection. The 28-day mortality of CRKP infection was 13.1% and was independently associated with sex, admitted unit, and types of infection.

CONCLUSIONS

Strict policies for antibiotic use, cautious decisions regarding the implementation of invasive procedures, and careful management of patients with catheters, especially intravascular catheters, are necessary to handle CRKP infection.

Population pharmacokinetics and exposure-response analysis of tigecycline in patients with hospital-acquired pneumonia

BACKGROUND

Tigecycline has been widely used to treat hospital-acquired pneumonia (HAP) off-label since it is effective against a wide range of multidrug-resistant bacteria. However, no recommended dosage for this indication has been evaluated, resulting in possible inadequate treatment.

AIMS

The aims of this study are to establish the population pharmacokinetic (PPK) model of tigecycline in Chinese patients with HAP, as well as to evaluate the exposure-response relationship for the treatment of HAP with multidrug-resistant gram-negative bacteria.

METHODS

A PPK analysis of tigecycline was conducted on pooled data from 328 blood samples obtained from 89 patients with HAP. Tigecycline plasma concentrations were measured by a two-dimensional liquid chromatographic system and the data were analysed using Phoenix NLMETM software. Exposure-response analyses for efficacy were performed based on the data from 79 HAP patients with multidrug-resistant gram-negative infections. Classification and regression tree and logistic regression analyses were employed to identify which pharmacokinetic-pharmacodynamic (PK-PD) indices and magnitudes were the significant predictors of tigecycline efficacy.

RESULTS

A two-compartment model with zero-order absorption and first-order elimination adequately described the data. A larger body weight was associated with increased central volume of distribution and clearance (P < .005), and increased age, baseline creatinine concentration and aspertate aminotransferase were associated with decreased clearance (P < .005). The AUC_0-12h  × V/MIC ratio, APACHEII score and combined Pseudomonas aeruginosa infection are the strong predictors for tigecycline clinical response. Classification and regression tree analyses indicated that the combination of APACHEII score < 24 and AUC_0-12h  × V/MIC ratio ≥ 100 was associated with clinical success.

CONCLUSIONS

The proposed PPK model may serve as the basis for estimating tigecycline exposure for PK-PD analyses, and the PK-PD index and magnitude found in this study could be used for designing proper dosage regimens of tigecycline.

Dose optimisation based on pharmacokinetic/pharmacodynamic target of tigecycline

Tigecycline, a new first-in-class glycylcycline antibiotic, has shown promising efficacy against a broad range of micro-organisms. It is widely prescribed for various infections, with most prescriptions being considered for off-label use. However, only a few years after its approval by the US Food and Drug Administration (FDA), tigecycline is suspected of increasing all-cause mortality. Some clinicians have suggested such unfavourable outcomes correlate with inadequate drug exposure at the infection site. The pharmacokinetic/pharmacodynamic (PK/PD) profile of a drug plays an important role in predicting its antibiotic effect, which for tigecycline is determined as the ratio of area under the concentration-time curve (AUC) to minimum inhibitory concentration (MIC). In this study, PK/PD targets based on infection sites, bacterial isolates and patient populations are discussed. Generally, a higher dosage of tigecycline for the treatment of serious infections has been recommended in previous reports. However, the latest finding of tigecycline's atypical protein binding property requires consideration when recommending further use. In addition, combination therapy with other antibiotics provides another option by potentially lowering the MICs of multidrug-resistant bacteria.

Monte Carlo simulation evaluation of tigecycline dosing for bacteria with raised minimum inhibitory concentrations in non-critically ill adults

PURPOSE

Tigecycline is one of few antibiotics active against multidrug-resistant bacteria; however, the assessment of dosing strategies to optimize its activity is needed. The purpose was to use Monte Carlo Simulation (MCS) to determine if safe tigecycline dosing options attaining breakpoints for pharmacokinetic/pharmacodynamic (PK-PD) targets in non-critically ill adults could be identified.

METHODS

Publications that evaluated tigecycline dosing regimens and provided mean PK variables of interest (minimum 2 of: elimination rate constant or half-life and volume of distribution or clearance), with SDs, were included. Weighted mean (±SDs) for each PK parameter were determined. Food and Drug Administration minimum inhibitory concentration (MIC) tigecycline breakpoints for susceptible (MIC ≤ 2 μg/mL), intermediate (MIC 4 μg/mL), and resistant (MIC ≥ 8 μg/mL) Enterobacteriaceae were used. MCS probability distributions for PK-PD target attainment of AUC for total tigecycline plasma concentration from 0 to 24 h following an intravenous dose (AUC_{total, 0-24h}) to MIC ratios of ≥ 18, 7, and 4.5 were generated, with success defined as ≥ 80% probability of target attainment at a given MIC.

RESULTS

Ten studies (n = 442) were eligible. Tigecycline 150 mg IV q12h for ward patients with resistant bacteria up to a MIC of 0.48, 1, and 2 μg/mL for an AUC_{total, 0-24h}/MIC target attainment of 18, 7, and 4.5, respectively, may be appropriate.

CONCLUSION

Bacterial infections with tigecycline MICs ≥ 0.48-2 μg/mL, depending on AUC_{total, 0-24h}/MIC target, may require treatment with alternate antibiotics due to target attainment failure.

Effect of pharmacokinetic/pharmacodynamic ratio on tigecycline clinical response and toxicity in critically ill patients with multidrug-resistant Gram-negative infections

Introduction:

The information about the pharmacokinetics and optimal dose of tigecycline in critically ill patients with severe underlying diseases is limited and controversial. In this study, we evaluate the pharmacokinetic parameters of tigecycline in critically ill patients with multidrug-resistant Gram-negative infection and explore the association between the pharmacokinetic/pharmacodynamic ratio and treatment response.

Methods:

A prospective study was designed including critically ill patients treated with tigecycline for multidrug-resistant Gram-negative infections. Blood samples were collected at day 3–5 of treatment, and pharmacokinetics parameters were evaluated using NONMEM^® software. Relationship between area under the free concentration–time curve and minimum inhibitory concentration ratio (fAUC/MIC) and treatment failure was evaluated. Association between tigecycline fAUC and hepatobiliary toxicity was also investigated.

Results:

Twenty-five critically ill patients were included in the study. In the pharmacokinetic model, weight and total bilirubin level were found to be significant predictors of tigecycline clearance. Fifteen (60.0%) patients achieved an fAUC/MIC ratio >4.5, seven (28.0%) an fAUC/MIC > 6.96 and only three (12.0%) an fAUC/MIC > 17.9. No differences in fAUC/MIC ratio were obtained between those patients with and without clinical failure (5.28 (IC95%: 2.57–7.94) vs 8.71 (3.57–13.84)). fAUC values were higher in those patients who suffered hepatobiliary disorders (7.63 (3.93–11.34) vs 17.63 (7.85–26.28) mg/L/h).

Conclusion:

An important percentage of critically ill patients with multidrug-resistant Gram-negative infection treated with tigecycline do not achieve an appropriate pharmacokinetic/pharmacodynamic value. Tigecycline fAUC seems to be associated with hepatobiliary disorders in this study population. The effect of fAUC/MIC ratio on clinical response remains unclear.

Safety and Efficacy of Tigecycline in Intensive Care Unit Patients Based on Therapeutic Drug Monitoring

OBJECTIVE

Tigecycline exerts significant beneficial effects against drug-resistant bacterial infections. The largely empirical medications used in clinical practice are often associated with wide individual differences in efficacy and safety. We investigated the associations between the pharmacokinetics of tigecycline and its efficacy and safety in intensive care unit (ICU) patients, with the aim of facilitating clinical applications of tigecycline.

METHODS

ICU patients who were prescribed tigecycline in a hospital setting were prospectively included. Factors related to the clinical efficacy and safety of tigecycline were assessed by univariate and multivariate analyses.

RESULTS

This study included 45 patients, from whom a total of 63 blood samples were collected to determine steady-state trough plasma concentrations (Cmin) of tigecycline. The Cmin of tigecycline was 417.1 ± 263.8 ng/mL (mean ± SD). The multivariate analysis showed that the APACHE II scores [odds ratio (OR) = 0.874, 95% confidence interval (CI) = 0.733-0.901, P = 0.048] were significantly correlated with the efficacy of tigecycline, whereas there was no correlation between Cmin of tigecycline and efficacy. In safety, the risk factors significantly associated with hepatotoxicity were sex (OR = 0.562, 95% CI = 0.191-0.774, P = 0.023), APACHE II score (OR = 1.061, 95% CI = 1.039-1.392, P = 0.045), and Cmin (OR = 1.210, 95% CI = 1.014-1.336, P = 0.008). The optimal cut-off for hepatotoxicity in ICU patients treated with tigecycline was 474.8 ng/mL.

CONCLUSIONS

There was considerable variability in the Cmin of tigecycline among the ICU patients in this study and it is at risk of high exposure in women. Cmin can be a useful predictor of hepatotoxicity with a cut-off of 474.8 ng/mL.

Optimization of tigecycline dosage regimen for different infections in the patients with hepatic or renal impairment

OBJECTIVE

The objective of this study was to investigate the cumulative fraction of response (CFR) of various tigecycline dosing regimens in patients with hepatic or renal impairment.

METHODS

Monte Carlo simulations were performed using pharmacokinetic parameters and microbiological data to evaluate various tigecycline regimens in patients with hepatic or renal impairment.

RESULTS

For HAP and cIAI, the regimen of 25 mg q12h achieved CFR values of >90% in Child-Pugh C patients against Gram-positive bacteria and partial Gram-negative bacteria (Escherichia coli and Klebsiella oxytoca). However, dose increases of tigecycline was mostly required for Enterobacter cloacae, Klebsiella pneumoniae and Acinetobacter baumanni. The conventional tigecycline regimen (50 mg q12h) was effective for HAP and cIAI caused by Gram-positive bacteria and Escherichia coli in patients with renal impairment. For HAP caused by Klebsiella pneumoniae and Enterobacter cloacae, patients with severe renal failure can use the standard dose regimen 50 mg q12h, and other patients need to increase the dose of tigecycline. However, when treating cSSSI caused by Acinetobacter baumannii, Enterobacter cloacae and Klebsiella pneumoniae, all tigecycline maintenance doses have a CFR <90%.

CONCLUSIONS

It is necessary to optimize tigecycline dosage regimens in patients with hepatic or renal impairment in order to maximise clinical response and minimise the probability of exposure-related toxicity.

A new HPLC-DAD method for contemporary quantification of 10 antibiotics for therapeutic drug monitoring of critically ill pediatric patients

The common practice of therapeutic drug monitoring (TDM) involves the quantification of drug plasma concentrations at a specific time in a dosing window. Although TDM for antibiotics is not considered mandatory, it may represent a valid tool for clinicians in order to limit antibiotic resistance and avoid therapeutic failures. The aim of our study was to develop and validate a high-performance liquid chromatography-diode array detection method for simultaneous quantification of 10 antibiotics in plasma. This method has a fast analytical procedure that uses the same chromatographic conditions to quantify ceftazidime, ceftriaxone, meropenem, ertapenem, ciprofloxacin, tigecycline, ampicillin, levofloxacin and piperacillin, plus the β-lactamase inhibitor tazobactam. Method validation was ensured by testing selectivity, accuracy, precision, limits of detection and quantification, recovery and stability. The calibration ranges, established accordingly to the expected plasma concentration in patients, showed a coefficient of determination >0.996 for all compounds. Within- and between-days precisions reported a coefficient of variation >15%. Similarly, the accuracy evaluation reported a relative standard deviation of <10% for each antibiotic. The recovery ranged between 97 and 103% for all compounds. This method could represent a useful tool for TDM of antibiotics.

Clinical study on the safety and efficacy of high-dose tigecycline in the elderly patients with multidrug-resistant bacterial infections: A retrospective analysis

Multidrug-resistant bacterial (MDRB) infections have been difficult to treat clinically. Tigecycline (TIG) has several advantages, especially in the treatment of severe infections. Many clinicians have considered increasing the TIG dose to improve the efficacy of this molecule. The safety and efficacy of high-dose TIG in elderly patients with MDRB infections were investigated in this study.We conducted a retrospective analysis of the elderly patients with MDRB infections who were treated at the First Affiliated Hospital. A total of 106 patients received a conventional dose (CD-TIG group: 50 mg every 12 hours) of TIG and 51 received a high dose (HD-TIG group: 100 mg every 12 hours). The data from all patients were collected for examining the clinical features and performing the microbiological analysis. The safety profile and efficacy of the HD regimen were investigated.The clinical efficacy and microbiological eradication in the patients with MDRB infection were higher in the HD-TIG group than the CD-TIG group. The independent predictors of clinical cure were the use of TIG at HD (odd ratio [OR], 5.129; 95% confidence interval [CI] [1.890, 13.921]; P = .001) and microbiological eradication (OR, 3.049; 95% CI, [1.251, 7.430]; P = .014). In the ventilator-associated pneumonia (VAP) and bloodstream infection (BSI) subgroups, the sole independent predictor of clinical cure was the HD of TIG, and no significant adverse events were observed. The occurrence of multidrug-resistant Acinetobacter baumannii infection and an MIC value of 1 to 2 g/mL for TIG were independently associated with clinical failure in the VAP subgroup.HDs of TIG was found to associate with better clinical efficacy and microbiological eradication than its CDs in the elderly patients with MDRB infections. In the VAP and BSIs subgroups, administration of HDs of TIG was associated with better outcomes.

Pharmacokinetic and pharmacodynamic profiling of four antimicrobials against Acinetobacter baumannii infection

BACKGROUND

The aim of this study was to evaluate common antimicrobial regimens used in eradicating Acinetobacter baumannii in Shenyang, China.

METHODS

Monte Carlo simulation was conducted to estimate the probability target attainment (PTA) and cumulative fraction of response (CFR) for imipenem, cefoperazone/sulbactam (2:1), tigecycline and colistin methanesulfonate.

RESULTS

For the results of PTAs, imipenem following administration of 0.5 g q6 h, 1 g q8 h, and 1 g q6 h for both 0.5 h and 2 h infusion achieved＞90% PTAs when MIC was 8 μg/ml; cefoperazone/ sulbactam (2:1) following administration of 4.5 g q6 h and 6 g q6 h achieved＞90% PTAs when MIC was 64μg/ml; tigecycline following administration of 50 mg q12 h and 100 mg q12 h achieved＞90% PTAs when MIC was 1 μg/ml; colistin methanesulfonate with high dosages (3MU q8 h) could provide high PTA (95.13%) in patients with CL_Cr＜60 ml/min when MIC was 2 μg/ml. As for CFR values of four antibiotics, imipenem achieved the lowest CFR values. For cefoperazone/sulbactam (2:1) and tigecycline, with simulated regimens improvement, the CFR values were both increased, and there were obviously increasing CFR values against Acinetobacter baumannii. For colistin methanesulfonate, the most aggressive dosage of 3MU q8 h could provide satisfactory CFR values (≥86.94%) against Acinetobacter baumannii in patients at various CL_Cr.

CONCLUSION

This study suggested that measurement of MICs, individualized therapy and therapeutic drug-level monitoring should be considered together to achieve the optimal drug exposure. That will provide the best chance of achieving the highest probability of a successful clinical or microbiological response, and avoiding the induced resistance.

Efficacy and safety of high-dose tigecycline for the treatment of infectious diseases: A meta-analysis

BACKGROUND

High-dose (HD) tigecycline regimen is increasingly used in infectious diseases, however its efficacy and safety versus low-dose (LD) is still unclear.

METHODS

A systematic review and meta-analysis was performed; PubMed, Embase, Cochrane Library, ScienceDirect, Web of Science, clinicalTrials.gov, Wanfang, VIP, and China National Knowledge Infrastructure (CNKI), were searched using terms "tigecycline" AND "dose" up to October 31, 2018. Eligible studies were randomized trials or cohort studies comparing mortality, clinical response, microbiological eradication and safety of different tigecycline dose regimens for any bacterial infection. The primary outcome was mortality, and the secondary outcomes were clinical response rate, microbiological eradiation rate and adverse events (AEs). Meta-analysis was done with random-effects model, with risk ratios (RR) and 95% confidence intervals (CI) calculated for all outcomes.

RESULTS

Of 951 publications retrieved, 17 studies (n = 1041) were pooled in our meta-analysis. The primary outcome was available in 11 studies, and the RR for mortality was 0.67 (95% CI 0.53-0.84, P < .001). Clinical response (RR 1.46, 95% CI 1.30-1.65, P < .001) and microbiological eradication rate (RR 1.61, 95% CI 1.35-1.93, P < .001) were both higher in HD than in LD tigecycline regimen. However, non-Chinese study subgroup presented no statistical significance between HD and LD regimen, RR for mortality, clinical response and microbiological eradication were 0.79 (95% CI 0.56-1.14, P = .21), 1.35 (95% CI 0.96-1.92, P = .26), 1.00 (95% CI 0.22-4.43, P = 1.00), respectively. AEs did not differ between HD and LD tigecycline (RR 1.00, 95% CI 0.80-1.26, P = .97).

CONCLUSION

HD tigecycline regimen reduced mortality meanwhile improved clinical efficacy and should be considered in serious infections caused by multidrug-resistant and extensively drug-resistant (MDR/XDR) bacteria.

Evaluation of the ratio of the estimated area under the concentration-time curve to minimum inhibitory concentration (estimated AUIC) as a predictor of the outcome for tigecycline treatment for pneumonia due to multidrug-resistant bacteria in an intensive care unit

OBJECTIVES

Based on pharmacokinetics/pharmacodynamics (PK/PD) and the minimum inhibitory concentration (MIC) of tigecycline (TGC), dose increases have been advocated to maximize the efficacy against pneumonia that is suspected to be due to multidrug-resistant (MDR) bacteria in an intensive care unit. This practice-based study explored the relationship between the predicted PK parameter, the ratio of the area under the concentration-time curve to the 24 h of dosing/minimum inhibitory concentration (AUC_0-24/MIC or AUIC), and the clinical and microbiological outcomes in critically ill patients with pneumonia due to MDR bacteria.

METHODS

We conducted a prospective cohort study of the treatment of pneumonia due to MDR bacteria in an intensive care unit. The study patients were recruited and assigned to either TGC standard dose (SD, 50 mg q12 h) or high dose (HD, 100 mg q12 h) for the treatment of pneumonia due to MDR bacteria depending on the doctors' decisions. The relationships between the PK/PD parameters and outcomes were examined.

RESULTS

Over the study period, 105 patients were included in the study. Whereas C1/2, Cmin, MIC and AUC were dramatically higher in the HD group than in the SD group (all P < 0.05), the Cmax and AUIC had no difference in both groups (all P > 0.05). The patients in the HD group had a higher clinical cure rate than those in the SD group (P = 0.029), but the bacterial eradication rate and survival rate of the patients in the HD group were not better than those in SD group (P = 0.279 and 0.416, respectively). The Cmax, C1/2, Cmin and AUC in the cured group were higher than those in failure group (all P < 0.05). The MICs were dramatically higher in the failure group than those in cure group (P = 0.0001), which led to significantly lower AUICs (P = 0.0001). In the ROC analysis, the areas of Cmax, C1/2, Cmin, AUC, negative-MIC and AUIC under the ROC curve were 0.64, 0.69, 0.67, 0.66, 0.73 and 0.82, respectively. The sensitivity was ascertained to be 75% and the specificity was 89% when the AUIC cut-off value was considered to be 10.12. Moreover, the sensitivity was ascertained to be 63% and the specificity was 80% when the MIC cut-off value was considered to be 1.75 mg/L.

CONCLUSIONS

The AUIC and MIC are associated with tigecycline treatment outcomes in pneumonia due to MDR bacteria, and aiming to achieve an individualized AUIC ≥ 10.12 when MIC < 1.75 mg/L could improve outcomes.

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.

Use of Monte Carlo simulation to evaluate the efficacy of tigecycline and minocycline for the treatment of pneumonia due to carbapenemase-producing Klebsiella pneumoniae

BACKGROUND

Pneumonia caused by carbapenemase-producing Klebsiella pneumoniae (CP-KP) are increasingly encountered in hospitals worldwide, causing high mortality due to lack of treatment options. The goal of this study was to assess the efficacy of tigecycline and minocycline for CP-KP hospital-acquired pneumonia (HAP) by using Monte Carlo simulation.

METHODS

A total of 164 non-duplicated CP-KP strains were collected from sputum or blood in patients with HAP. The MICs for antimicrobials were determined by the agar dilution method. A 10,000-patient Monte Carlo Simulation based on a PK/PD model incorporating the MICs and population pharmacokinetic parameters were conducted to calculate probability of target attainment (PTA) at each MIC value and total cumulative fraction of response (CFR).

RESULTS

The susceptibility rate of tigecycline and minocycline were 79.9% and 41.5%, respectively. At recommended doses, an optimal PTA of 90% was obtained for treating HAP caused by CP-KP with MICs of tigecycline ≤0.5 mg/L or minocycline ≤4 mg/L. The CFR of tigecycline at the recommended dose and double dose (100 mg q12h) were 71.2% and 90.2%, respectively. The CFR of minocycline at recommended dose and double dose (200 mg q12h) was 53.4% and 77.2%, respectively.

CONCLUSIONS

The findings of this study suggest that the recommended dose of tigecycline was not effective in HAP caused by CP-KP, and a higher CFR indicating a better clinical efficacy can be gained by doubling the dose (100 mg q12h). minocycline (200 mg q12h) might be a potential alternative of tigecycline to against strains with MICs ≤ 8 mg/L.

Pharmacokinetic/pharmacodynamic parameters for treatment optimization of infection due to antibiotic resistant bacteria: a summary for practical purposes in children and adults

In the last years, there has been a tremendous increase in the incidence of bacterial infections due to resistant strains, especially multi-drug resistant Gram-negative bacilli. In Europe, a north to south and a west to east gradient was noticed, with more than one third of the K. pneumonia isolates being resistant to carbapenems in few countries. New antibiotics are lacking and, as a consequence, pharmacokinetic/pharmacodynamic parameters, normalized to pathogen minimal inhibitory concentration, are used with increased frequency to treat infections due to difficult-to-treat pathogens. These parameters are available at least for the adult population, but sparse in many different publications. This review wants to provide a comprehensive and 'easy to read' text for everyday practice, briefly summarizing the presently available knowledge on pharmacokinetic/pharmacodynamic parameters (normalized for minimal inhibitory concentration values) of different class drugs, that can be applied for an effective antibacterial treatment infections due to antibiotic-resistant pathogens.

Acinetobacter Prosthetic Joint Infection Treated with Debridement and High-Dose Tigecycline

Prosthesis retention is not recommended for multidrug-resistant Acinetobacter prosthetic joint infection due to its high failure rate. Nevertheless, replacing the prosthesis implies high morbidity and prolonged hospitalization. Although tigecycline is not approved for the treatment of prosthetic joint infection due to multidrug resistant Acinetobacter baumannii, its appropriate use may preclude prosthesis exchange. Since the area under the curve divided by the minimum inhibitory concentration is the best pharmacodynamic predictor of its efficacy, we used tigecycline at high dose, in order to optimize its efficacy and achieve implant retention in 3 patients who refused prosthesis exchange. All patients with prosthetic joint infections treated at our Institution are prospectively registered in a database. Three patients with early prosthetic joint infection of total hip arthroplasty due to multidrug resistant A. baumannii were treated with debridement, antibiotics and implant retention, using a high maintenance dose of tigecycline (100 mg every 12 hours). The cases were retrospectively reviewed. All patients signed informed consent for receiving off-label use of tigecycline.

Tigecycline was well tolerated, allowing its administration at high maintenance dose for a median of 40 days (range 30–60). Two patients were then switched to minocycline at standard doses for a median of 3.3 months in order to complete treatment. Currently, none of the patients showed relapse. Increasing the dose of tigecycline could be considered as a means to better attain pharmacodynamic targets in patients with severe or difficult-to-treat infections. Tigecycline at high maintenance dose might be useful when retention of the implant is attempted for treatment for prosthetic joint infections due to multidrug resistant Acinetobacter. Although this approach might be promising, off-label use of tigecycline should be interpreted cautiously until prospective data are available. Tigecycline is probably under-dosed for the treatment of implant and biofilm associated infections.

Impact of bacterial load on pharmacodynamics and susceptibility breakpoints for tigecycline and Klebsiella pneumoniae

OBJECTIVES

In the absence of other therapeutic options, tigecycline is used to treat bloodstream infections and pneumonia caused by carbapenemase-producing Klebsiella pneumoniae (CP-Kp). In this study, the standard and high tigecycline dosing regimens were simulated and tested against different inocula of CP-Kp isolates in an in vitro pharmacokinetic (PK)/pharmacodynamic (PD) model.

METHODS

Four susceptible isolates (EUCAST MICs of 0.125-1 mg/L) and two intermediately susceptible CP-Kp clinical isolates (MICs of 2 mg/L) were tested at three different inocula (10⁷, 10⁵ and 10³ cfu/mL), simulating tigecycline serum and lung fC_max concentrations of 0.15 and 1.5 mg/L, respectively, of 50 mg tigecycline every 12 h for 48 h. The exposure-effect relationships were described and the probability of target attainment was calculated for each inoculum in order to determine PK/PD susceptibility breakpoints.

RESULTS

No cfu reduction was observed at serum concentrations. At lung concentrations and low inocula, a bacteriostatic and killing effect was found for isolates with MICs of 0.25 and 0.125 mg/L, respectively. The fAUC_0-24/MIC (tAUC_0-24/MIC) associated with half-maximal activity was 16 (150) with 10³ cfu/mL, 28 (239) with 10⁵ cfu/mL and 79 (590) with 10⁷ cfu/mL. A PK/PD susceptibility breakpoint of ≤0.06 and ≤0.125 mg/L for bacteraemia with ≤10¹ cfu/mL and ≤0.25 and ≤0.5 mg/L for pneumonia with ≤10³ cfu/g was determined for the standard tigecycline dose of 50 mg and the higher dose of 100 mg, respectively.

CONCLUSIONS

Tigecycline monotherapy with either 50 or 100 mg would not be sufficient for most patients with bacteraemia, though the higher dose of 100 mg could be effective for patients with pneumonia with low bacterial load.

Combinatorial pharmacodynamics of polymyxin B and tigecycline against heteroresistant Acinetobacter baumannii

The prevalence of heteroresistant Acinetobacter baumannii is increasing. Infections due to these resistant pathogens pose a global treatment challenge. Here, the pharmacodynamic activities of polymyxin B (PMB) (2-20 mg/L) and tigecycline (0.15-4 mg/L) were evaluated as monotherapy and in combination using a 4 × 4 concentration array against two carbapenem-resistant and polymyxin-heteroresistant A. baumannii isolates. Time Kill Experiments was employed at starting inocula of 10(6) and 10(8) CFU/mL over 48 h. Clinically relevant combinations of PMB (2 mg/L) and tigecycline (0.90 mg/L) resulted in greater reductions in the bacterial population compared with polymyxin alone by 8 h (ATCC 19606, -6.38 vs. -3.43 log10 CFU/mL; FADDI AB115, -1.38 vs. 2.08 log10 CFU/mL). At 10× the clinically achievable concentration (PMB 20 mg/L in combination with tigecycline 0.90 mg/L), there was bactericidal activity against FADDI AB115 by 4 h that was sustained until 32 h, and against ATCC 19606 that was sustained for 48 h. These studies show that aggressive polymyxin-based dosing in combination with clinically achievable tigecycline concentrations results in early synergistic activity that is not sustained beyond 8 h, whereas combinations with higher tigecycline concentrations result in sustained bactericidal activity against both isolates at both inocula. These results indicate a need for optimised front-loaded polymyxin-based combination regimens that utilise high polymyxin doses at the onset of treatment to achieve good pharmacodynamic activity whilst minimising adverse events.

Efficacy and Safety of Tigecycline for Patients with Hospital-Acquired Pneumonia

BACKGROUND

Tigecycline is an antibiotic agent with a broad spectrum, which has an antibacterial effect against many multidrug-resistant organisms. However, its clinical efficacy in the treatment of hospital-acquired pneumonia (HAP) is disputed.

MATERIALS AND METHODS

In this report, a systematic review and meta-analysis were conducted to evaluate the efficacy and safety of tigecycline for the treatment of HAP. The primary outcome was the rate of clinical cure, and the secondary outcomes were mortality and adverse events (AEs).

RESULTS

Four trials involving 1,234 patients were included. The standard-dose tigecycline and comparator groups did not differ significantly in their rates of clinical cure. However, high-dose tigecycline was more effective than standard-dose tigecycline or the comparators for the treatment of HAP. There was no significant difference in mortality between the standard-dose or high-dose regimen and the comparators. Although the safety profile of standard-dose tigecycline was similar to the comparators, the high-dose regimen exhibited more AEs compared with the other groups.

CONCLUSION

High-dose tigecycline is efficient for the treatment of HAP but is associated with more AEs.

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.

Hospital Readmissions in Patients With Carbapenem-Resistant Klebsiella pneumoniae

BACKGROUND

Various transmission routes contribute to spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) in hospitalized patients. Patients with readmissions during which CRKP is again isolated ("CRKP readmission") potentially contribute to transmission of CRKP.

OBJECTIVE

To evaluate CRKP readmissions in the Consortium on Resistance against Carbapenems in K. pneumoniae (CRaCKLe).

DESIGN

Cohort study from December 24, 2011, through July 1, 2013.

SETTING

Multicenter consortium of acute care hospitals in the Great Lakes region.

PATIENTS

All patients who were discharged alive during the study period were included. Each patient was included only once at the time of the first CRKP-positive culture.

METHODS

All readmissions within 90 days of discharge from the index hospitalization during which CRKP was again found were analyzed. Risk factors for CRKP readmission were evaluated in multivariable models.

RESULTS

Fifty-six (20%) of 287 patients who were discharged alive had a CRKP readmission. History of malignancy was associated with CRKP readmission (adjusted odds ratio [adjusted OR], 3.00 [95% CI, 1.32-6.65], P<.01). During the index hospitalization, 160 patients (56%) received antibiotic treatment against CRKP; the choice of regimen was associated with CRKP readmission (P=.02). Receipt of tigecycline-based therapy (adjusted OR, 5.13 [95% CI, 1.72-17.44], using aminoglycoside-based therapy as a reference in those treated with anti-CRKP antibiotics) was associated with CRKP readmission.

CONCLUSION

Hospitalized patients with CRKP-specifically those with a history of malignancy-are at high risk of readmission with recurrent CRKP infection or colonization. Treatment during the index hospitalization with a tigecycline-based regimen increases this risk.

Modeling and forecasting Acinetobacter baumannii resistance to set appropriate use of cefoperazone-sulbactam: Results from trend analysis of antimicrobial consumption and development of resistance in a tertiary care hospital

BACKGROUND

Antibiotic resistance in Acinetobacter baumannii (AB) is increasingly recognized as a major threat to global health. The extensive use of antimicrobial chemotherapy in clinical environments is considered a factor associated with the enhanced occurrence of antimicrobial resistance.

METHODS

The autoregressive integrated moving average model was used to forecast the trend of drug resistance of AB in the coming years, combined with assessment of relationships between antibiotic consumption and AB resistance to set appropriate antibiotic use.

RESULTS

A total of 4,377 AB isolates were collected and were associated with a resistance rate of >80% of major antibiotics. A significant increase in resistance in AB to cefoperazone-sulbactam (C-S) (r(2) = 0.98, P = .001) was observed. C-S consumption was correlated with the development of resistance in AB (r = 0.99, P = .02). From 2009-2012, the percentage of AB resistance to C-S was <35%; however, it increased sharply (67.3%) because the annual consumption of C-S was >20 defined daily dose (DDD)/1,000 patient days in 2013.Increased consumption of C-S may contribute to the emergence of multidrug-resistant AB and the increasing prevalence of hospital-acquired infection.

CONCLUSION

A recommendation of limiting the use of C-S to <20 DDD/1,000 patient days annually was proposed for inhibiting the sharp increment of the AB resistance rate in our hospital.

Intravenous Antibiotics Used in the Treatment of Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) continues to cause significant morbidity and mortality. Despite advances in medical care, the prevalence of both community-acquired and hospital-acquired MRSA has progressively increased. Community-acquired MRSA typically occurs in patients without recent illness or hospitalization, presents as acute skin and soft tissue infections, and is usually not multidrug resistant. Hospital-acquired MRSA, however, presents in patients recently hospitalized or treated in long-term care settings and in those who have had medical procedures and is usually associated with multidrug-resistant strains. Both types of infections, if not properly treated, have the potential to become invasive. This article discusses current intravenous antibiotics that are available for the empiric treatment of MRSA infections along with a newer phenomenon known as the "seesaw effect."

Intravenous Antibiotics Used in the Treatment of Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) continues to cause significant morbidity and mortality. Despite advances in medical care, the prevalence of both community-acquired and hospital-acquired MRSA has progressively increased. Community-acquired MRSA typically occurs in patients without recent illness or hospitalization, presents as acute skin and soft tissue infections, and is usually not multidrug resistant. Hospital-acquired MRSA, however, presents in patients recently hospitalized or treated in long-term care settings and in those who have had medical procedures and is usually associated with multidrug-resistant strains. Both types of infections, if not properly treated, have the potential to become invasive. This article discusses current intravenous antibiotics that are available for the empiric treatment of MRSA infections along with a newer phenomenon known as the “seesaw effect.”

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.