The Potential Use of Ceftazidime-Avibactam Against Carbapenem Resistant Klebsiella pneumoniae Clinical Isolates Harboring Different Carbapenemase Types in a Thai University Hospital

Monte Carlo simulation for dosage optimization of the best available therapy for bloodstream infections secondary to carbapenemase-producing Klebsiella pneumoniae in critically ill patients

OBJECTIVE

We aimed to use Monte Carlo simulation, based on pharmacokinetic/pharmacodynamic targets, to investigate and determine the optimal dosage of the available combination therapies for carbapenem-resistant Klebsiella pneumoniae (CRKP) in critically ill patients.

METHODS

We collected CRKP clinical isolates from Phramongkutklao Hospital between October 2020 and June 2022. A molecular study of resistant genes was performed using polymerase chain reaction. Broth microdilution checkerboards were used to evaluate the mono- and synergistic antibiotic activities. Monte Carlo simulation was used to determine the optimal antibiotic regimens, based on the probability of target attainment (PTA) and cumulative fraction of response.

RESULTS

The 54 CRKP isolates were resistant to tigecycline (100%), colistin (75.9%), amikacin (70.4%), and gentamicin (63.0%). The most common carbapenemase genotype was blaoxacillinases (OXA)-48-like (42.6%), followed by blaNew Delhi metallo beta-lactamase (NDM) (29.6%) and coexistence of blaOXA-48-like and blaNDM (22.2%). Based on the PTA, synergistic and additive activities against CRKP isolates were observed with appropriate dosages of tigecycline-colistin (67.9%), tigecycline-gentamicin (62.2%), and tigecycline-amikacin (51.4%).

CONCLUSIONS

Tigecycline-colistin was the best available combination therapy for critically ill patients with CRKP, especially NDM. When used in combination with tigecycline, a colistin creatinine clearance of <90 mL/min can raise the cumulative fraction of response target and less nephrotoxicity.

Efficacy and Safety of Oral Neomycin for the Decolonization of Carbapenem-Resistant Enterobacterales: An Open-Label Randomized Controlled Trial

BACKGROUND

Patients with carbapenem-resistant Enterobacterales (CRE) in the gastrointestinal (GI) tract are at risk for subsequent infections and transmission, necessitating contact precautions. Neomycin has shown in vitro activity against CRE in 66-85% of isolates. This study evaluated the efficacy and safety of neomycin for CRE decolonization.

METHODS

In this open-label randomized controlled trial, stool/rectal swab samples from high-risk patients were collected and tested for CRE colonization in the GI tract. Patients who had CRE and met eligible criteria were divided into a neomycin group (n = 26; treated with 4.2 g/day neomycin for 5 days) and a control group (n = 26). CRE detection in stool/rectal swabs was performed on days 7 ± 2 and 14 ± 2.

RESULTS

The two groups' baseline characteristics were similar. CRE presence on day 7 ± 2 was significantly lower in the neomycin group (46.2%) than in the control group (80.8%, p = 0.01). Efficacy of neomycin (4.2 g/day for 5 days) for CRE decolonization was 42.8-53.8% by day 7. By day 14 ± 2, the CRE rate in the neomycin group had risen to align with the control group's rate (73.1% vs. 61.5%, p = 0.56). The neomycin group experienced mild, temporary, gastrointestinal side-effects.

CONCLUSIONS

Neomycin effectively reduced CRE colonization on day 7 ± 2, but its impact waned by day 14 ± 2. This suggests that neomycin dosage was too low and the duration of treatment was too short for lasting CRE decolonization.

Adequacy of the Dosing and Infusion Time of Ceftazidime/Avibactam for the Treatment of Gram-Negative Bacterial Infections: A PK/PD Simulation Study

Introduction

Recent studies suggested the potential benefits of extended infusion times to optimize the treatment efficacy of ceftazidime/avibactam, which indicated that the current pharmacokinetic/pharmacodynamic (PK/PD) target may not be sufficient, especially for severe infections. The purpose of this study is to assess the adequacy of dosing strategies and infusion durations of ceftazidime/avibactam when applying higher PK/PD targets.

Methods

This study utilized published PK parameters to conduct Monte Carlo simulations. Different dosages including the recommended regimen based on renal function were simulated and evaluated by the probability of target attainment (PTA) and cumulative fraction of response (CFR). Different PK/PD targets were set for ceftazidime and avibactam. MIC distributions from various sources were used to calculate the CFR.

Results

Multiple PK/PD targets have been set in this study, All recommended dosage could easily achieve the target of 50%fT ≥ MIC (ceftazidime) and 50%fT ≥ CT=1.0 mg/L (avibactam). However, for severe infection patients with normal renal function and augmented renal clearance at the recommended dosage (2000 mg/500 mg, every 8 hours), the infusion duration needs to be extended to 3 hours and 4 hours to achieve the targets of 100%fT ≥ MIC and 100%fT ≥ CT=1.0 mg/L. Only continuous infusion at higher dosages achieved 100%fT ≥ 4×MIC and 100%fT ≥ CT=4.0 mg/L targets to all currently recommended regimens. According to the varying MIC distributions, higher concentrations are needed for Pseudomonas aeruginosa, with the attainment rates vary across different regions.

Conclusion

The current recommended dosing regimen of ceftazidime/avibactam is insufficient for severe infection patients, and continuous infusion is suggested.

Mortality factors and antibiotic options in carbapenem-resistant Enterobacterales bloodstream infections: Insights from a high-prevalence setting with co-occurring NDM-1 and OXA-48

Bloodstream infections (BSI) caused by carbapenem-resistant Enterobacterales (CRE) are associated with a high mortality rate. This study aimed to investigate factors associated with 14-day mortality and identify a potential treatment option. A retrospective cohort study was conducted on patients with CRE-BSI in Thailand from 2015 to 2020. The multivariate Cox proportional-hazards model was employed to identify factors influencing 14-day mortality. Out of 134 diagnosed cases of CRE-BSI, the all-cause 14-day mortality rate was 35.1%. The most prevalent organism isolated was Klebsiella pneumoniae (85.8%), followed by Escherichia coli (11.9%). Among the 60 isolates tested for carbapenemase genes, the majority exhibited co-occurring blaNDM-1 and blaOXA-48 (51.7%), followed by blaOXA-48 (31.7%) and blaNDM-1 (15.0%). In the multivariate analysis, neutropenia (adjusted hazard ratio [aHR] 2.55; 95% confidence interval [95%CI] 1.28-5.06; p = 0.008), sepsis/septic shock (aHR 3.02; 95%CI 1.33-6.86; p = 0.008), and previous metronidazole exposures (aHR 3.58; 95%CI 1.89-6.71; p < 0.001) were identified as independent factors for 14-day mortality. The fosfomycin-based regimen was found to be protective (aHR 0.37; 95%CI 0.15-0.92; p = 0.032). In patients with CRE-BSI, particularly in regions with a high occurrence of co-occurring blaNDM-1 and blaOXA-48, neutropenia, sepsis/septic shock, and previous metronidazole exposures emerged as independent risk factors for mortality. Moreover, the fosfomycin-based regimen showed an improvement in the survival rate.

The Challenge of Overcoming Antibiotic Resistance in Carbapenem-Resistant Gram-Negative Bacteria: "Attack on Titan"

The global burden of bacterial resistance remains one of the most serious public health concerns. Infections caused by multidrug-resistant (MDR) bacteria in critically ill patients require immediate empirical treatment, which may not only be ineffective due to the resistance of MDR bacteria to multiple classes of antibiotics, but may also contribute to the selection and spread of antimicrobial resistance. Both the WHO and the ECDC consider carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and carbapenem-resistant Acinetobacter baumannii (CRAB) to be the highest priority. The ability to form biofilm and the acquisition of multiple drug resistance genes, in particular to carbapenems, have made these pathogens particularly difficult to treat. They are a growing cause of healthcare-associated infections and a significant threat to public health, associated with a high mortality rate. Moreover, co-colonization with these pathogens in critically ill patients was found to be a significant predictor for in-hospital mortality. Importantly, they have the potential to spread resistance using mobile genetic elements. Given the current situation, it is clear that finding new ways to combat antimicrobial resistance can no longer be delayed. The aim of this review was to evaluate the literature on how these pathogens contribute to the global burden of AMR. The review also highlights the importance of the rational use of antibiotics and the need to implement antimicrobial stewardship principles to prevent the transmission of drug-resistant organisms in healthcare settings. Finally, the review discusses the advantages and limitations of alternative therapies for the treatment of infections caused by these "titans" of antibiotic resistance.

Prescription Pattern of Intravenous Fosfomycin in a Provincial Hospital in Thailand

BACKGROUND

In Thailand, active antibiotics against Gram-negative bacteria are limited. The re-emergence of intravenous (IV) fosfomycin is an alternative. IV fosfomycin has broad-spectrum activity, relative safety, and availability. The limitations of the clinical use of IV fosfomycin include the lack of susceptibility reports and unclear dosing. Therefore, this study was designed to examine the prescription pattern of IV fosfomycin in Chonburi Hospital, a provincial hospital in Thailand.

MATERIALS AND METHODS

A retrospective descriptive study involving in-patients aged ≥18 years who received IV fosfomycin between February 2019 and January 2020. Data were collected from the electronic patient records.

RESULTS

Of 265 patients, 254 (95.8%) and 11 (4.2%) received IV fosfomycin for treatment and prophylaxis, respectively. IV fosfomycin was prescribed for empirical and definitive treatment. All 166 organisms were Gram-negative bacteria (GNB), including Enterobacterales (47.0%), Acinetobacter baumannii (44.0%), and Pseudomonas aeruginosa (9.0%). Moreover, 141 (87.6%) isolates were carbapenem-resistant GNB (CR-GNB). The most commonly used IV fosfomycin regimen contained colistin or aminoglycosides. Furthermore, 35.3% of the combination regimens contained one active antibiotic. The appropriate dosage of IV fosfomycin for treating urinary tract infection was 71.8%. The 14-day all-cause mortality rate in CR-GNB was 45.0%.

CONCLUSION

IV fosfomycin is reserved for secondary use in treating nosocomial infection with resistant GNB. It is used synergistically with other antibiotics. At least one active antibiotic and the optimal fosfomycin dosage should be considered. An antimicrobial stewardship program should be implemented for the optimal use of fosfomycin.

Association Between Types of Carbapenemase and Clinical Outcomes of Infection Due to Carbapenem Resistance Enterobacterales

Purpose

Compared with non-carbapenemase producing carbapenem-resistant Enterobacterales (non-CP-CRE), carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE) are associated with considerable mortality. However, given that the patients are treated with various therapeutic options, it remains unclear whether differences in types of carbapenemase genes yield different mortality rates. Therefore, this study aims to identify carbapenemase genes and identify whether clinical outcomes differ according to the prevalence of genotype and phenotype of carbapenemase among Enterobacterales clinical isolated.

Patients and Methods

A retrospective cohort study was performed to determine whether types of carbapenemase genes have an impact on clinical outcomes. Carbapenem-resistant clinical isolates were collected at a tertiary care university hospital in Songkhla, Thailand, between June 2018 and February 2020. Demographic and microbiological data such as antimicrobial susceptibility, carbapenemase genes, and overall mortality were evaluated.

Results

A total of 121 Enterobacterales clinical isolated were evaluated. The bla_NDM-1 gene was detected in 44% of the isolates, followed by bla_OXA-48 (28%) and bla_NDM-1/OXA-48 (28%). NDM-1- or NDM-1/OXA-48- producing isolates were more likely to require meropenem MICs of ≥16 mg/L, while OXA-48-producing isolates were more likely to require meropenem MICs of <16 mg/L. The patients with NDM-1 or NDM-1/OXA-48 had a higher 14 days mortality rate than those with OXA-48 after treating with carbapenem-containing regimens (P-value 0.001) or colistin-containing regimens (P-value < 0.001).

Conclusion

Our findings suggest that the mortality for CP-CRE infection in patients with NDM-1 or NDM-1/OXA-48 was higher than the mortality in those with OXA-48, which It seems that the type of carbapenemase gene may affect meropenem MIC levels. Hence, in treatment decisions involving the use of either carbapenem-containing regiment or colistin-containing regiment in patients with CP-CRE infection, especially those in the NDM-1 and NDM-1/OXA-48 groups, the patient symptoms should be closely monitored.

Antimicrobial Activity Profiles and Potential Antimicrobial Regimens against Carbapenem-Resistant Enterobacterales Isolated from Multi-Centers in Western Thailand

The spread of carbapenem-resistant Enterobacterales (CRE) constitutes a global health burden. Antimicrobial susceptibility and types of carbapenemase differ by geographic region. This study aimed to (1) examine the minimum inhibitory concentrations (MICs) and antibiotic resistance genes and (2) investigate antibiotic dosing regimens against CRE using Monte Carlo simulation. Clinical carbapenem-resistant Klebsiella pneumoniae (CRKP), Escherichia coli (CREC), and Enterobacter cloacae (CREclo) isolates were collected from various hospitals in western Thailand. Broth microdilution was performed, and the types of carbapenemase and mcr-1 genes were detected using polymerase chain reaction (PCR). Monte Carlo simulation was used to establish optimal antimicrobial dosing regimens meeting the criterion of a cumulative fraction of response (CFR) >90%. A total of 150 CRE isolates from 12 hospitals were included. The proportion of CRKP (76%) was greater than that of CREC (22%) and CREclo (2%). Regional hospitals reported higher rates of resistance than general hospitals. Most isolates were resistant to aztreonam and ceftazidime/avibactam, whereas they were highly susceptible to aminoglycosides. Most carbapenemases were NDM (47.33%), OXA-48 (43.33%) and NDM plus OXA-48 (6.67%); five OXA-48 positive isolates carried mcr-1 genes. Currently, high-dose tigecycline is the only optimal regimen against CRE isolates. Further extensive research on antibiotic synergism or new antibiotics should be conducted.