Clinical review: balancing the therapeutic, safety, and economic issues underlying effective antipseudomonal carbapenem use

Therapeutic drug monitoring of six contraindicated/co-administered drugs by simple and green RP-HPLC-PDA; application to spiked human plasma

Therapeutic drug monitoring is an important clinical testing of the drugs to monitor their concentrations in plasma in order to guarantee their optimal impact, and to avoid any side effects resulting from drug-drug interactions. A green reversed-phase high-performance liquid chromatographic method using a photodiode array detector (RP-HPLC-PDA) was developed for the simultaneous determination of three carbapenem antibiotics (Imipenem, ertapenem, and meropenem) with the co-formulated drug (cilastatin) and contraindicated drugs (probenecid and warfarin) in spiked human plasma. The separation was achieved at 25 °C using a gradient elution of a mixture of mobile phase A: methanol and mobile phase B: phosphate buffer (pH 3.0). The photodiode array detector was adjusted at 220 nm. Bioanalytical method validation was carried out as per the FDA guidelines, and the method showed good linearity ranges for the six drugs that included their Cmax levels along with low limits of quantification. Based on the results, the method was found to be accurate and precise; with high % recovery and good % RSD, respectively. The method was successfully applied to spiked human plasma, signifying a good potential to be implemented in future TDM studies of these drugs when co-administered together.

Efficacy of combination therapy with standard-dose carbapenem for treating nosocomial pneumonia caused by carbapenem-resistant Acinetobacter baumannii in intensive care units: A multicentre retrospective propensity score-matched study

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is common worldwide. Despite carbapenem resistance, standard-dose carbapenems are still used in clinical practice. Hence in this study, we aimed to compare the efficacy and outcomes of a regimen containing standard-dose carbapenems with those of a regimen lacking carbapenems during the treatment of critically ill patients with CRAB nosocomial pneumonia in the intensive care unit (ICU). Initially, 735 patients were recruited for this multicentre retrospective cohort study. After exclusion, time-window bias adjustment, and propensity score matching, multiple clinical outcomes were compared between the carbapenem-containing (CC) (n = 166) and no carbapenem-containing (NCC) (n = 166) groups. The CC group showed a higher risk of clinical failure on day 7 than the NCC group (44.6% vs. 33.1%, P = 0.043). The lengths of ICU stay (21 and 16 days, P = 0.024) and hospital stay (61 and 44 days, P = 0.003) were longer in the CC group than in the NCC group. Multivariate analysis showed that the CC regimen was associated with higher clinical failure (adjusted odds ratio (aOR) = 1.64, 95% CI = 1.05-2.56, P = 0.031) and lower microbiological eradication (aOR = 0.48, 95% CI = 0.23-1.00, P = 0.049) at day 7 than the NCC group. Thus, a regimen containing a standard dose of carbapenem should be prescribed with caution for treating CRAB nosocomial pneumonia in the ICU.

From Batch to the Semi-Continuous Flow Hydrogenation of pNB, pNZ-Protected Meropenem

Meropenem is currently the most common carbapenem in clinical applications. Industrially, the final synthetic step is characterized by a heterogeneous catalytic hydrogenation in batch mode with hydrogen and Pd/C. The required high-quality standard is very difficult to meet and specific conditions are required to remove both protecting groups [i.e., p-nitrobenzyl (pNB) and p-nitrobenzyloxycarbonyl (pNZ)] simultaneously. The three-phase gas-liquid-solid system makes this step difficult and unsafe. The introduction of new technologies for small-molecule synthesis in recent years has opened up new landscapes in process chemistry. In this context, we have investigated meropenem hydrogenolysis using microwave (MW)-assisted flow chemistry for use as a new technology with industrial prospects. The reaction parameters (catalyst amount, T, P, residence time, flow rate) in the move from the batch process to semi-continuous flow were investigated under mild conditions to determine their influence on the reaction rate. The optimization of the residence time (840 s) and the number of cycles (4) allowed us to develop a novel protocol that halves the reaction time compared to batch production (14 min vs. 30 min) while maintaining the same product quality. The increase in productivity using this semi-continuous flow technique compensates for the slightly lower yield (70% vs. 74%) obtained in batch mode.

Karunakaran R, Abdul Jabar K, Ponnampalavanar S, Chong CW, Teh CSJ. A retrospective study on molecular epidemiology trends of carbapenem resistant Enterobacteriaceae in a teaching hospital in Malaysia

BACKGROUND

Carbapenem resistant Enterobacteriaceae (CRE) has rapidly disseminated worldwide and has become a global threat to the healthcare system due to its resistance towards "last line" antibiotics. This study aimed to investigate the prevalence of CRE and the resistance mechanism as well as the risk factors associated with in-hospital mortality.

METHODS

A total of 168 CRE strains isolated from a tertiary teaching hospital from 2014-2015 were included in this study. The presence of carbapenemase genes and minimum inhibitory concentration of imipenem, meropenem and colistin were investigated. All carbapenem-resistant Klebsiella pneumoniae (K. pneumoniae) strains were characterised by PFGE. The risk factors of patients infected by CRE associated with in-hospital mortality were determined statistically.

RESULTS

The predominant CRE species isolated was K. pneumoniae. The carbapenemases detected were blaOXA-48, blaOXA-232, blaVIM and blaNDM of which blaOXA-48 was the predominant carbapenemase detected among 168 CRE strains. A total of 40 CRE strains harboured two different carbapenemase genes. A total of seven clusters and 48 pulsotypes were identified among 140 CRKp strains. A predominant pulsotype responsible for the transmission from 2014 to 2015 was identified. Univariate statistical analysis identified that the period between CRE isolation and start of appropriate therapy of more than 3 days was statistically associated with in-hospital mortality.

Oral meropenem for superbugs: challenges and opportunities

An increase in the number of multidrug-resistant microbial strains is the biggest threat to global health and is projected to cause >10 million deaths by 2055. The carbapenem family of antibacterial drugs are an important class of last-resort treatment of infections caused by drug-resistant bacteria and are only available as an injectable formulation. Given their instability within the gut and poor permeability across the gut wall, oral carbapenem formulations show poor bioavailability. Meropenem (MER), a carbapenem antibiotic, has broad-spectrum antibacterial activity, but suffers from the above-mentioned issues. In this review, we discuss strategies for improving the oral bioavailability of MER, such as inhibiting tubular secretion, prodrug formulations, and use of nanomedicine. We also highlight challenges and emerging approaches for the development of oral MER.

Antimicrobial Resistance Prediction for Gram-Negative Bacteria via Game Theory-Based Feature Evaluation

The increasing prevalence of antimicrobial-resistant bacteria drives the need for advanced methods to identify antimicrobial-resistance (AMR) genes in bacterial pathogens. With the availability of whole genome sequences, best-hit methods can be used to identify AMR genes by differentiating unknown sequences with known AMR sequences in existing online repositories. Nevertheless, these methods may not perform well when identifying resistance genes with sequences having low sequence identity with known sequences. We present a machine learning approach that uses protein sequences, with sequence identity ranging between 10% and 90%, as an alternative to conventional DNA sequence alignment-based approaches to identify putative AMR genes in Gram-negative bacteria. By using game theory to choose which protein characteristics to use in our machine learning model, we can predict AMR protein sequences for Gram-negative bacteria with an accuracy ranging from 93% to 99%. In order to obtain similar classification results, identity thresholds as low as 53% were required when using BLASTp.

Use of meropenem in treating carbapenem-resistant Enterobacteriaceae infections

Introduction: The epidemiology of carbapenem-resistant Enterobacterales (CRE) is increasingly worldwide. Production of carbapenemases is the most common and efficient mechanism of carbapenem resistance, and could theoretically be overcome by optimizing the pharmacokinetic/pharmacodynamic (PK/PD) behavior of meropenem. Areas covered: This article overviews the available literature concerning the potential role that meropenem may still have in the treatment carbapenem-resistant Enterobacteriaceae infections. Clinical studies published in English language until June 2019 were searched on PubMed database. Expert commentary: High-dose continuous infusion meropenem-based combination regimens could still represent a valuable option for treating CRE infections in specific circumstances. Knowledge of the local prevalent mechanisms of carbapenem resistance, of patient clinical severity, of the site of infection, of an accurate minimum inhibitory concentration (MIC) value, coupled with the possibility of carrying-out a real-time therapeutic drug monitoring (TDM)-based PK/PD optimization of drug exposure must all be considered as fundamental for properly pursuing this goal.

Determination of carbapenem antibiotics using a purpose-made capillary electrophoresis instrument with contactless conductivity detection

In this study, the employment of a purpose-made capillary electrophoresis (CE) instrument with capacitively coupled contactless conductivity detection (C⁴D) as a simple and cost-effective approach for simultaneous determination of different carbapenem antibiotics is reported. The developed CE-C⁴D approach was for the first time applied for quality control of various pharmaceutical formulations in Vietnam, as well as for therapeutic monitoring of these antibiotics in plasma samples from patients under intensive care. Four of the most popular carbapenems in Vietnam, doripenem, meropenem, imipenem and ertapenem, were determined using an electrolyte composed of 10 mM Tris adjusted to pH 8.0 with acetic acid. The best detection limits achieved using the developed CE-C⁴D method were 0.36 mg/L and 0.45 mg/L for pharmaceutical and plasma samples, respectively. Good agreement between results from CE-C⁴D and the confirmation method (HPLC-PDA) was achieved, with a coefficient of determination (r²) for the two pairs of data of 0.9967.

Does nephrotoxicity develop less frequently when vancomycin is combined with imipenem-cilastatin than with meropenem? A comparative study

Introduction: Nephrotoxicity is a frequent complication of vancomycin therapy. Experimental studies in different animal species have demonstrated the attenuation of vancomycin-associated nephrotoxicity with cilastatin administration. This study aimed to evaluate if imipenem-cilastatin attenuates vancomycin-associated nephrotoxicity, in patients treated with combinations of vancomycin and carbapenems. Methods: This retrospective, propensity-score matched study was conducted at King Faisal Specialist Hospital and Research Centre, Riyadh and Jeddah. Nephrotoxicity was compared in patients who received imipenem-cilastatin + vancomycin or meropenem + vancomycin. Patients with no history of renal disease who received imipenem-cilastatin + vancomycin or meropenem + vancomycin for a minimum of 72 h, from 1 January 2017 to 31 December 2017, were included. Nephrotoxicity was defined according to the RIFLE criteria (Risk, Injury, Failure, Loss, End-stage renal disease) if sustained for least 72 h. Results: A total of 227 patients were included in the analysis, consisting of 121 patients in the imipenem-cilastatin + vancomycin group, and 106 patients in the meropenem + vancomycin group. In the unmatched data set the rate of nephrotoxicity was 8.2% in imipenem-cilastatin + vancomycin group and 20.7% in the meropenem + vancomycin group (p = .007). Logistic regression analysis showed that imipenem-cilastatin + vancomycin therapy was associated with a 56% lower rate of nephrotoxicity compared to meropenem + vancomycin therapy. Propensity-score matching resulted in rates of nephrotoxicity of 6.2% and 17.1% in the imipenem-cilastatin + vancomycin group and the meropenem + vancomycin groups, respectively (p = .034). Conclusion: Vancomycin-associated nephrotoxicity developed less frequently when vancomycin was combined with imipenem-cilastatin than when combined with meropenem.

Too much of a good thing: a retrospective study of β-lactam concentration-toxicity relationships

Objectives

To determine the existence of concentration-toxicity relationships for common β-lactam antibiotic adverse effects and define thresholds above which toxicity is more likely.

Patients and methods

Retrospective review of consecutive patients treated with piperacillin, meropenem or flucloxacillin who underwent therapeutic drug monitoring (TDM) at St Vincent's Hospital (Sydney, Australia) between January 2013 and December 2015. Adverse events investigated included neurotoxicity, nephrotoxicity, hepatotoxicity and opportunistic Clostridium difficile infection. Toxicity was measured using observational grading criteria, clinical assessment and relevant serum biomarkers. These findings were correlated with trough TDM measurements at the time of toxicity presentation.

Results

TDM results from 378 patients (piperacillin = 223, meropenem = 94 and flucloxacillin = 61) were investigated. There was no difference in baseline patient characteristics across antibiotic groups. A statistically significant elevation in mean serum trough concentrations (Cmin) was found in patients diagnosed with neurotoxicity (piperacillin, P < 0.01; meropenem, P = 0.04; flucloxacillin, P = 0.01) and those who developed nephrotoxicity whilst being treated with piperacillin (P < 0.01) or meropenem (P < 0.01). Incidence of hepatotoxicity and C. difficile was not related to Cmin. Threshold concentrations for which there is 50% risk of developing a neurotoxicity event (piperacillin, Cmin >361.4 mg/L; meropenem, Cmin >64.2 mg/L; flucloxacillin, Cmin >125.1 mg/L) or nephrotoxicity (piperacillin, Cmin >452.65 mg/L; meropenem, Cmin >44.45 mg/L) varied across antibiotics.

Conclusions

Our data reveal an association between toxic concentrations for a number of β-lactam agents and neurotoxic/nephrotoxic effects. We have defined threshold concentrations above which these toxicities become more likely. Clinicians should balance concerns for therapeutic efficacy with potential toxicity when considering aggressive therapy.

Pharmacokinetics of meropenem in septic patients on sustained low-efficiency dialysis: a population pharmacokinetic study

BACKGROUND

The aim of the study was to describe the population pharmacokinetics (PK) of meropenem in critically ill patients receiving sustained low-efficiency dialysis (SLED).

METHODS

Prospective population PK study on 19 septic patients treated with meropenem and receiving SLED for acute kidney injury. Serial blood samples for determination of meropenem concentrations were taken before, during and after SLED in up to three sessions per patient. Nonparametric population PK analysis with Monte Carlo simulations were used. Pharmacodynamic (PD) targets of 40% and 100% time above the minimal inhibitory concentration (f T _{> MIC}) were used for probability of target attainment (PTA) and fractional target attainment (FTA) against Pseudomonas aeruginosa.

RESULTS

A two-compartment linear population PK model was most appropriate with residual diuresis supported as significant covariate affecting meropenem clearance. In patients without residual diuresis the PTA for both targets (40% and 100% f T _{> MIC}) and susceptible P. aeruginosa (MIC ≤ 2 mg/L) was > 95% for a dose of 0.5 g 8-hourly. In patients with a residual diuresis of 300 mL/d 1 g 12-hourly and 2 g 8-hourly would be required to achieve a PTA of > 95% and 93% for targets of 40% f T _{> MIC} and 100% f T _{> MIC}, respectively. A dose of 2 g 8-hourly would be able to achieve a FTA of 97% for 100% f T _{> MIC} in patients with residual diuresis.

CONCLUSIONS

We found a relevant PK variability for meropenem in patients on SLED, which was significantly influenced by the degree of residual diuresis. As a result dosing recommendations for meropenem in patients on SLED to achieve adequate PD targets greatly vary. Therapeutic drug monitoring may help to further optimise individual dosing.

TRIAL REGISTRATION

Clincialtrials.gov, NCT02287493 .

blaVIM and blaIMP Genes Detection in Isolates of Carbapenem Resistant P. aeruginosa of Hospitalized Patients in Two Hospitals in Iran

BACKGROUND & OBJECTIVE

Beta-lactam antibiotics resistance specifically Imipenem and Meropenem, the last choices of treatment, causes fatal events in patients with P.aeruginosa infection. The aim of this study was to detect the VIM and IMP of metallo-beta-lactamase genes in 103 isolates of P. aeruginosa in two Iranian hospitals.

METHODS

In this study, we evaluated the susceptibility of P. aeruginosa to a range of β-lactam antibiotics using disk diffusion method as a standard biochemical test. Combined disk test of Imipenem (IMP) and Imipenem plus Ethylenediaminetetraacetic acid (EDTA) was performed as a phenotypic method to find metallo-beta-lactamase producing isolates.Using conventional PCR method; we evaluated VIM and IMP of metallo-beta-lactamase (MBL) genes in 103 isolates of P.aeruginosa.

RESULTS

Twenty six (25.2%) out of 103 isolates were resistant to Imipenem and 26 (25.2%) to Meropenem. Among 26 Imipenem and Meropenem-resistant strains (25.2%), 19 cases (73.0%) were MBL producing. Using PCR method, we detected the bla_VIM and bla_IMP genes in 6 (5.8%) and 2(1.9%) of 19 MBL producing isolates, respectively.

CONCLUSIONS

Evaluation of these carbepenemases genes improve epidemiologic researches and also, can be used as a diagnostic tool for discriminating between antibiotics resistant and sensitive strains of P.aeruginosa as well as follow-up the patients after treatment.

Pharmacodynamic profiling of doripenem, imipenem and meropenem against prevalent Gram-negative organisms in the Asia-Pacific region

Carbapenems are increasingly being utilised owing to the escalating prevalence of antimicrobial-resistant Gram-negative bacteria from community and hospital settings. In this study, pharmacodynamic profiles of doripenem, imipenem and meropenem were evaluated against Gram-negative bacteria isolated from hospitalised patients. MICs for carbapenems were determined for Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii obtained from the COMPACT II programme conducted in the Asia-Pacific region. Monte Carlo simulations were undertaken to assess the pharmacodynamic profile of carbapenems against each of the pathogens. All carbapenem regimens achieved optimal exposures [cumulative fraction of response (CFR) ≥90%] against E. coli and K. pneumoniae. Against P. aeruginosa, doripenem achieved 81.3-95.3% CFR, imipenem achieved 55.2-77.9% CFR and meropenem achieved 71.9-91.3% CFR; only doripenem regimens of 4-h infusion of 1000 mg every 8h (q8h) and 1-h and 4-h infusion of 2000 mg q8h and a meropenem regimen of 3-h infusion of 2000 mg q8h obtained optimal exposures; all carbapenem regimens showed slight (1-7%) improvement in CFRs in favour of isolates collected from ICU sources. Against A. baumannii, CFRs were much lower (25.9-46.7% CFR) and no carbapenem regimens achieved optimal exposure in or outside the ICU. Owing to the high potency of carbapenems against these Enterobacteriaceae populations, standard regimens are likely to perform well in the Asia-Pacific region. However, larger doses combined with prolonged infusions will be required to increase the CFR for these carbapenems against resistant non-fermenting Gram-negatives such as P. aeruginosa and A. baumannii that are prevalent in these countries.

Antimicrobial activity of different Lactobacillus species against multi- drug resistant clinical isolates of Pseudomonas aeruginosa

BACKGROUND

Lactobacilli are the well known friendly bacteria for their probiotic activities against pathogens. The inhibitory activity of different strains of lactobacilli either obtained as commercial products or isolated from human feces was investigated against the clinical isolates of Pseudomonas aeruginosa. The isolates were selected as the most resistant strains when challenged with anti-pseudomonal antibiotics already in clinical practice.

MATERIALS AND METHODS

Both the plate spot test as well as the agar cup method were used for screening of Lactobacillus strains against Pseudomonas aeruginosa.

RESULTS

A Lactobacillus acidophilus strain isolated from feces of an Iranian child showed a strong anti-pseudomonal activity (90 percent after 72h incubation) against the multi-drug resistant clinical isolates while a Lactobacillus reuteri strain isolated from a commercial oral product resulted in relatively weak response and a Lactobacillus acidophilus strain isolated from a commercial vaginal product did not show any inhibitory activity. In a kinetic study the lactobacillus sensitive Pseudomonas aeruginosa showed a significant bacteriostatic activity in vitro in the presence of lactobacillus supernatants.

CONCLUSION

Some lactobacilli exhibit significant inhibitory activity against the multidrug resistant clinical isolates of Pseudomonas aeruginosa.