Shifting Gears: The Future of Polymyxin Antibiotics

Antimicrobial resistance crisis: could artificial intelligence be the solution?

Antimicrobial resistance is a global public health threat, and the World Health Organization (WHO) has announced a priority list of the most threatening pathogens against which novel antibiotics need to be developed. The discovery and introduction of novel antibiotics are time-consuming and expensive. According to WHO's report of antibacterial agents in clinical development, only 18 novel antibiotics have been approved since 2014. Therefore, novel antibiotics are critically needed. Artificial intelligence (AI) has been rapidly applied to drug development since its recent technical breakthrough and has dramatically improved the efficiency of the discovery of novel antibiotics. Here, we first summarized recently marketed novel antibiotics, and antibiotic candidates in clinical development. In addition, we systematically reviewed the involvement of AI in antibacterial drug development and utilization, including small molecules, antimicrobial peptides, phage therapy, essential oils, as well as resistance mechanism prediction, and antibiotic stewardship.

Acinetobacter baumannii: an evolving and cunning opponent

Acinetobacter baumannii is one of the most common multidrug-resistant pathogens causing nosocomial infections. The prevalence of multidrug-resistant A. baumannii infections is increasing because of several factors, including unregulated antibiotic use. A. baumannii drug resistance rate is high; in particular, its resistance rates for tigecycline and polymyxin-the drugs of last resort for extensively drug-resistant A. baumannii-has been increasing annually. Patients with a severe infection of extensively antibiotic-resistant A. baumannii demonstrate a high mortality rate along with a poor prognosis, which makes treating them challenging. Through carbapenem enzyme production and other relevant mechanisms, A. baumannii has rapidly acquired a strong resistance to carbapenem antibiotics-once considered a class of strong antibacterials for A. baumannii infection treatment. Therefore, understanding the resistance mechanism of A. baumannii is particularly crucial. This review summarizes mechanisms underlying common antimicrobial resistance in A. baumannii, particularly those underlying tigecycline and polymyxin resistance. This review will serve as a reference for reasonable antibiotic use at clinics, as well as new antibiotic development.

Antimicrobial Resistance Profiles and Co-Existence of Multiple Antimicrobial Resistance Genes in mcr-Harbouring Colistin-Resistant Enterobacteriaceae Isolates Recovered from Poultry and Poultry Meats in Malaysia

The co-existence of the colistin resistance (mcr) gene with multiple drug-resistance genes has raised concerns about the possibility of the development of pan-drug-resistant bacteria that will complicate treatment. This study aimed to investigate the antibiotic resistance profiles and co-existence of antibiotic resistance genes among the colistin-resistant Enterobacteriaceae isolates recovered from poultry and poultry meats. The antibiotic susceptibility to various classes of antibiotics was performed using the Kirby-Bauer disk diffusion method and selected antimicrobial resistance genes were detected using PCR in a total of 54 colistin-resistant Enterobacteriaceae isolates including Escherichia coli (E. coli) (n = 32), Salmonella spp. (n = 16) and Klebsiella pneumoniae (K. pneumoniae) (n = 6) isolates. Most of the isolates had multi-drug resistance (MDR), with antibiotic resistance against up to seven classes of antibiotics. All mcr-harbouring, colistin-resistant Enterobacteriaceae isolates showed this MDR (100%) phenotype. The mcr-1 harbouring E. coli isolates were co-harbouring multiple antibiotic resistance genes. The seven most commonly identified resistance genes (^blaTEM, tetA, floR, aac-3-IV, aadA1, fosA, aac(6_)-lb) were detected in an mcr-1-harbouring E. coli isolate recovered from a cloacal swab. The mcr-5 harbouring Salmonella spp. isolate recovered from poultry meats was positive for ^blaTEM, tetA, floR, aac-3-IV, fosA and aac(6_)-lb genes. In conclusion, the colistin-resistant Enterobacteriaceae with mcr genes co-existing multiple clinically important antimicrobial resistance genes in poultry and poultry meats may cause potential future threats to infection treatment choices in humans and animals.

Evaluation of antibiotic appropriateness at an outpatient oncology centre

Current evidence supporting antimicrobial stewardship programs focused largely in inpatient setting. With the shift in cancer management from inpatient to ambulatory setting, it is crucial to examine the prevalence and predictors of inappropriate antibiotics prescribing. This is a retrospective cross-sectional study conducted at the National Cancer Centre Singapore (NCCS). Patients at least 21 years, with an active or past cancer diagnosis and prescribed with at least one oral antibiotic by a NCCS physician from 1st July to 30th September 2019 were included. Antibiotic appropriateness was assessed using institutional antibiotic guidelines or published clinical practice guidelines. For cases where antibiotics appropriateness cannot be ascertained using these guidelines, an independent three-member expert panel was consulted. A total of 815 patients were screened; 411 (59.4% females) were included with mean age of 62.4 years. The top three cancer diagnoses were breast (26.5%), lung (15.6%) and head and neck (13.6%). More than half (58.6%) received appropriate antibiotic choice. Of which, 235 (97.5%), 238 (98.8%) and 194 (80.5%) received appropriate dose, frequency and duration respectively. The presence of non-oncologic immunosuppressive comorbidities (OR 4.890, 95% CI 1.556-15.369, p-value = 0.007), antibiotic allergy (OR 2.352, 95% CI 1.178-4.698, p-value = 0.015) and skin and soft tissue infections (OR 2.004, 95% CI 1.276-3.146, p-value = 0.003) were associated with a higher incidence of inappropriate antibiotic choice. This study highlighted that inappropriate antibiotic prescribing is prevalent in the ambulatory oncology setting. Predicators identified can aid in the design of targeted strategies to optimise antibiotic use in ambulatory oncology patients.

In Vitro Potency and Spectrum of the Novel Polymyxin MRX-8 Tested against Clinical Isolates of Gram-Negative Bacteria

The polymyxins display excellent in vitro antimicrobial activity against most Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates, but their clinical utility has been limited because of class-specific toxicity problems. Therefore, new polymyxin analogs with improved safety properties are needed to combat serious infections caused by resistant Gram-negative pathogens. MRX-8 is a novel polymyxin B analog that displays reduced toxicity in in vitro and animal assays and is currently being evaluated in a phase 1 clinical trial. In this nonclinical study, the in vitro potency and spectrum of MRX-8 and comparators were evaluated against a large set of Gram-negative clinical isolates collected in the United States in 2017 to 2020. MRX-8, colistin, and polymyxin B exhibited nearly identical antimicrobial activities against the Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii isolate sets. MRX-8 MIC₅₀ and MIC₉₀ values were 0.12 and 0.25 mg/L, respectively, for the set of Enterobacterales isolates not intrinsically resistant to colistin and 0.5 and 1 mg/L, respectively, against both the A. baumannii and P. aeruginosa isolate sets. All three polymyxin-class compounds retained activity against meropenem-resistant and multidrug-resistant isolate subsets but were inactive against isolates displaying acquired or intrinsic resistance to polymyxins. These results support the continued development of MRX-8 to treat serious Gram-negative infections.

Polymyxin resistance in Enterobacterales: overview and epidemiology in the Americas

The worldwide spread of carbapenem- and polymyxin-resistant Enterobacterales represents an urgent public-health threat. However, for most countries in the Americas, the available data are limited, although Latin America has been suggested as a silent spreading reservoir for isolates carrying plasmid-mediated polymyxin resistance mechanisms. This work provides an overall update on polymyxin and polymyxin resistance and focuses on uses, availability and susceptibility testing. Moreover, a comprehensive review of the current polymyxin resistance epidemiology in the Americas is provided. We found that reports in the English and Spanish literature show widespread carbapenemase-producing and colistin-resistant Klebsiella pneumoniae in the Americas determined by the clonal expansion of the pandemic clone ST258 and mgrB-mediated colistin resistance. In addition, widespread IncI2 and IncX4 plasmids carrying mcr-1 in Escherichia coli come mainly from human sources; however, plasmid-mediated colistin resistance in the Americas is underreported in the veterinary sector. These findings demonstrate the urgent need for the implementation of polymyxin resistance surveillance in Enterobacterales as well as appropriate regulatory measures for antimicrobial use in veterinary medicine.

Manual Reading of Sensititre Broth Microdilution System Panels Improves Accuracy of Susceptibility Reporting for Polymyxin Antibiotics

Accurate and reproducible antimicrobial susceptibility testing (AST) of polymyxin antibiotics is critical, as these drugs are last-line therapeutic options for the treatment of multidrug-resistant Gram-negative bacterial infections. However, polymyxin AST in the routine laboratory remains challenging. In this study, we evaluated the performance of an automated broth microdilution (BMD) system (Sensititre, ThermoFisher) compared to that of agar dilution (AD) for colistin and polymyxin B AST of 129 Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex clinical isolates. MICs derived from the Sensititre instrument based on two operator comparisons demonstrated overall categorical agreement (CA) of 86% and 89% compared to AD for colistin and 89% and 92% compared to AD for polymyxin B. However, error rates were higher than recommended by CLSI. Manual inspection of microdilution wells revealed microbial growth and skip wells which were erroneously interpreted by the Aris 2X instrument. Using manually interpreted BMD MICs read by two operators increased the overall categorical agreements to 88% and 95% compared to AD for colistin and 92% and 96% compared to AD for polymyxin B. Laboratories choosing to use the Sensititre platform for polymyxin AST should consider manual evaluation of wells as part of their algorithm.

Antibiotic resistance and detection of plasmid mediated colistin resistance mcr-1 gene among Escherichia coli and Klebsiella pneumoniae isolated from clinical samples

BACKGROUND

The prevalence of antimicrobial resistance (AMR) among Gram-negative bacteria is alarmingly high. Reintroduction of colistin as last resort treatment in the infections caused by drug-resistant Gram-negative bacteria has led to the emergence and spread of colistin resistance. This study was designed to determine the prevalence of drug-resistance among beta-lactamase-producing strains of Escherichia coli and Klebsiella pneumoniae, isolated from the clinical specimens received at a tertiary care centre of Kathmandu, Nepal during the period of March to August, 2019.

METHODS

A total of 3216 different clinical samples were processed in the Microbiology laboratory of Kathmandu Model Hospital. Gram-negative isolates (E. coli and K. pneumoniae) were processed for antimicrobial susceptibility test (AST) by using modified Kirby-Bauer disc diffusion method. Drug-resistant isolates were further screened for extended-spectrum beta-lactamase (ESBL), metallo-beta-lactamase (MBL), carbapenemase and K. pneumoniae carbapenemase (KPC) production tests. All the suspected enzyme producers were processed for phenotypic confirmatory tests. Colistin resistance was determined by minimum inhibitory concentration (MIC) using agar dilution method. Colistin resistant strains were further screened for plasmid-mediated mcr-1 gene using conventional polymerase chain reaction (PCR).

RESULTS

Among the total samples processed, 16.4% (529/3216) samples had bacterial growth. A total of 583 bacterial isolates were recovered from 529 clinical samples. Among the total isolates, 78.0% (455/583) isolates were Gram-negative bacteria. The most predominant isolate among Gram-negatives was E. coli (66.4%; 302/455) and K. pneumoniae isolates were 9% (41/455). In AST, colistin, polymyxin B and tigecycline were the most effective antibiotics. The overall prevalence of multidrug-resistance (MDR) among both of the isolates was 58.0% (199/343). In the ESBL testing, 41.1% (n = 141) isolates were confirmed as ESBL-producers. The prevalence of ESBL-producing E. coli was 43% (130/302) whereas that of K. pneumoniae was 26.8% (11/41). Similarly, 12.5% (43/343) of the total isolates, 10.9% (33/302) of E. coli and 24.3% of (10/41) K. pneumoniae were resistant to carbapenem. Among 43 carbapenem resistant isolates, 30.2% (13/43) and 60.5% (26/43) were KPC and MBL-producers respectively. KPC-producers isolates of E. coli and K. pneumoniae were 33.3% (11/33) and 20% (2/10) respectively. Similarly, 63.6% (21/33) of the E. coli and 50% (5/10) of the K. pneumoniae were MBL-producers. In MIC assay, 2.2% (4/179) of E. coli and 10% (2/20) of K. pneumoniae isolates were confirmed as colistin resistant (MIC ≥ 4 µg/ml). Overall, the prevalence of colistin resistance was 3.1% (6/199) and acquisition of mcr-1 was 16.6% (3/18) among the E. coli isolates.

CONCLUSION

High prevalence of drug-resistance in our study is indicative of a deteriorating situation of AMR. Moreover, significant prevalence of resistant enzymes in our study reinforces their roles in the emergence of drug resistance. Resistance to last resort drug (colistin) and the isolation of mcr-1 indicate further urgency in infection management. Therefore, extensive surveillance, formulation and implementation of effective policies, augmentation of diagnostic facilities and incorporation of antibiotic stewardship programs can be some remedies to cope with this global crisis.

Lipid A profiling and metabolomics analysis of paired polymyxin-susceptible and -resistant MDR Klebsiella pneumoniae clinical isolates from the same patients before and after colistin treatment

BACKGROUND

The increased incidence of polymyxin-resistant MDR Klebsiella pneumoniae has become a major global health concern.

OBJECTIVES

To characterize the lipid A profiles and metabolome differences between paired polymyxin-susceptible and -resistant MDR K. pneumoniae clinical isolates.

METHODS

Three pairs of K. pneumoniae clinical isolates from the same patients were examined [ATH 7 (polymyxin B MIC 0.25 mg/L) versus ATH 8 (64 mg/L); ATH 15 (0.5 mg/L) versus ATH 16 (32 mg/L); and ATH 17 (0.5 mg/L) versus ATH 18 (64 mg/L)]. Lipid A and metabolomes were analysed using LC-MS and bioinformatic analysis was conducted.

RESULTS

The predominant species of lipid A in all three paired isolates were hexa-acylated and 4-amino-4-deoxy-l-arabinose-modified lipid A species were detected in the three polymyxin-resistant isolates. Significant metabolic differences were evident between the paired isolates. Compared with their corresponding polymyxin-susceptible isolates, the levels of metabolites in amino sugar metabolism (UDP-N-acetyl-α-d-glucosamine and UDP-N-α-acetyl-d-mannosaminuronate) and central carbon metabolism (e.g. pentose phosphate pathway and tricarboxylic acid cycle) were significantly reduced in all polymyxin-resistant isolates [fold change (FC) > 1.5, P < 0.05]. Similarly, nucleotides, amino acids and key metabolites in glycerophospholipid metabolism, namely sn-glycerol-3-phosphate and sn-glycero-3-phosphoethanolamine, were significantly reduced across all polymyxin-resistant isolates (FC > 1.5, P < 0.05) compared with polymyxin-susceptible isolates. However, higher glycerophospholipid levels were evident in polymyxin-resistant ATH 8 and ATH 16 (FC > 1.5, P < 0.05) compared with their corresponding susceptible isolates.

CONCLUSIONS

To our knowledge, this study is the first to reveal significant metabolic perturbations associated with polymyxin resistance in K. pneumoniae.

Polymyxin-induced nephrotoxicity and its predictors: a systematic review and meta-analysis of studies conducted using RIFLE criteria of acute kidney injury

Polymyxins are last-resort antibiotics re-emerged to treat infections caused by multidrug resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacterial infections. However, polymyxin-associated nephrotoxicity has become the main safety concern. Therefore, we conducted this systematic review and meta-analysis on polymyxin-induced nephrotoxicity and its predictors using studies conducted based on the validated RIFLE (Risk, Injury, Failure, Loss of Function and End-stage renal disease) criteria of acute kidney damage. Literature search was carried out through visiting legitimate databases and indexing services including PubMed, MEDLINE (Ovid®), EMBASE (Ovid®), and Scopus to retrieve relevant studies. Following screening and eligibility evaluation, relevant data were extracted from included studies and analyzed using STATA 15.0 and Rev-Man 5.3. Inverse variance method with random effects pooling model was used for the analysis of outcome measures at 95% confidence interval. Besides, meta-regression, meta-influence, and publication bias analyses were conducted. A total of 48 studies involving 6,199 adult patients aged ≥ 18 years were included for systematic review and meta-analysis. The pooled incidence of polymyxin-induced nephrotoxicity was found to be 45% (95% CI: 41- 49%; I² = 92.52%). Stratifying with RIFLE severity scales, pooled estimates of polymyxin-treated patients identified as 'risk', 'injury' and 'failure' were 17% (95% CI: 14-20%), 13% (95% CI: 11-15%), and 10% (95% CI: 9-11%), respectively. Besides, the pooled incidence of colistin-induced nephrotoxicity was about 48% (95% CI: 42-54%), whereas that of polymyxin B was 38% (95% CI: 32-44%). Likewise, colistin had 37% increased risk of developing nephrotoxicity compared to the polymyxin B treated cohorts (RR = 1.37, 95% CI: 1.13-1.67; I² = 57%). Older age (AOR = 1.03, 95% CI: 1.01-1.05), daily dose (AOR = 1.46, 95% CI: 1.09-1.96), underlying diabetes mellitus (AOR = 1.81, 95% CI: 1.25-2.63), and concomitant nephrotoxic drugs (AOR = 2.31, 95% CI: 1.79-3.00) were independent risk factors for polymyxin-induced nephrotoxicity. Patients with high serum albumin level were less likely (AOR = 0.69, 95% CI: 0.56-0.85] to experience nephrotoxicity compared to those with low albumin level. Despite the resurgence of these antibiotics for the chemotherapy of MDR/XDR-Gram-negative superbugs, the high incidence of nephrotoxicity has become a contemporary clinical concern. Being elderly, high daily dose, having underlying diseases such as diabetes, and use of concomitant nephrotoxic drugs were independent predictors of nephrotoxicity. Therefore, therapeutic drug monitoring should be done to these patients to outweigh the potential benefits of polymyxin therapy from its risk.

Polymyxin NP tests (from colonies and directly from blood cultures): accurate and rapid methodologies to detect polymyxin B susceptibility among Enterobacterales

Detection of polymyxins susceptibility is challenging. We aimed to evaluate Rapid Polymyxin NP from colonies (NP-colony) and directly from positive blood bottles (NP-bottle), using polymyxin B instead of colistin among Enterobacterales. Both had similar and acceptable accuracy. This is the first study performing NP-bottle using polymyxin B instead of colistin.

Activities of Cefiderocol with Simulated Human Plasma Concentrations against Carbapenem-Resistant Gram-Negative Bacilli in an In Vitro Chemostat Model

Activities of cefiderocol under simulated human plasma concentrations at the recommended dosing regimen of 2 g every 8 h with a 3-h infusion were evaluated using an in vitro chemostat model. Against a total of 6 meropenem-resistant Gram-negative strains with cefiderocol MICs of 0.5 to 4 μg/ml, including metallo-β-lactamase producers and carbapenem-resistant Acinetobacter baumannii, cefiderocol treatment showed a bactericidal effect within 8 h and sustained efficacy with no marked bacterial regrowth over 24 h.

Overcoming Intrinsic and Acquired Resistance Mechanisms Associated with the Cell Wall of Gram-Negative Bacteria

The global increase in multi-drug-resistant bacteria is severely impacting our ability to effectively treat common infections. For Gram-negative bacteria, their intrinsic and acquired resistance mechanisms are heightened by their unique cell wall structure. The cell wall, while being a target of some antibiotics, represents a barrier due to the inability of most antibacterial compounds to traverse and reach their intended target. This means that its composition and resulting mechanisms of resistance must be considered when developing new therapies. Here, we discuss potential antibiotic targets within the most well-characterised resistance mechanisms associated with the cell wall in Gram-negative bacteria, including the outer membrane structure, porins and efflux pumps. We also provide a timely update on the current progress of inhibitor development in these areas. Such compounds could represent new avenues for drug discovery as well as adjuvant therapy to help us overcome antibiotic resistance.

Performance of polymyxin B Etest in a setting of high prevalence of KPC-producing Klebsiella pneumoniae

OBJECTIVES

Polymyxin resistance has been increasing in many regions, and appropriate determination of polymyxin susceptibility is now a major challenge worldwide. Many clinical laboratories rely on gradient diffusion methods to assess polymyxin susceptibility, although broth microdilution (BMD) is the only method currently recommended by the CLSI and EUCAST. The aim of this study was to assess the performance of the polymyxin B (PMB) Etest in a setting with a high prevalence of KPC-producing Klebsiella pneumoniae (KPC-KP).

METHODS

A commercial Etest susceptibility testing method was evaluated and compared with the reference BMD method, considering isolates with a minimum inhibitory concentration (MIC) ≤2 mg/L for PMB as susceptible to this drug. A total of 310 clinical KPC-KP isolates were evaluated.

RESULTS

Susceptibility was significantly higher by Etest compared with BMD (82.6% vs. 75.8%). The MIC₅₀, MIC₉₀ and modal MICs for PMB were 0.25, 32 and 0.25 mg/L (27.1%) by BMD and 0.5, 16 and 0.5 mg/L (49.7%) by Etest, respectively. Although categorical agreement was 90.0%, there was poor essential agreement (50.6%). A high rate (34.7%) of very major errors (VMEs) and a relatively low rate (2.1%) of major errors were found.

CONCLUSION

The considerable number of resistant isolates in this study allowed an accurate estimation of VME rates and, consequently, a more comprehensive assessment of susceptibility testing for polymyxins. Etest did not meet fully the acceptance criteria for US FDA requirements. These data do not support the use of this commercial method for determining PMB MICs in carbapenem-resistant Enterobacterales populations.

Multidrug Resistant Acinetobacter baumannii: Resistance by Any Other Name Would Still be Hard to Treat

PURPOSE OF REVIEW

Acinetobacter baumannii (AB) is an infamous nosocomial pathogen with a seemingly limitless capacity for antimicrobial resistance, leading to few treatment options and poor clinical outcomes. The debatably low pathogenicity and virulence of AB are juxtaposed by its exceptionally high rate of infection-related mortality, likely due to delays in time to effective antimicrobial therapy secondary to its predilection for resistance to first-line agents. Recent studies of AB and its infections have led to a burgeoning understanding of this critical microbial threat and provided clinicians with new ammunition for which to target this elusive pathogen. This review will provide an update on the virulence, resistance, diagnosis, and treatment of multidrug resistant (MDR) AB.

RECENT FINDINGS

Advances in bacterial genomics have led to a deeper understanding of the unique mechanisms of resistance often present in MDR AB and how they may be exploited by new antimicrobials or optimized combinations of existing agents. Further, improvements in rapid diagnostic tests (RDTs) and their more pervasive use in combination with antimicrobial stewardship interventions have allowed for more rapid diagnosis of AB and decreases in time to effective therapy. Unfortunately, there remains a paucity of high-quality clinical data for which to inform the optimal treatment of MDR AB infections. In fact, recently completed studies have failed to identify a combination regimen that is consistently superior to monotherapy, despite the benefits demonstrated in vitro. Encouragingly, new and updated guidelines offer strategies for the treatment of MDR AB and may help to harmonize the use of high toxicity agents such as the polymyxins. Finally, new antimicrobial agents such as eravacycline and cefiderocol have promising in vitro activity against MDR AB but their place in therapy for these infections remains to be determined. Notwithstanding available clinical trial data, polymyxin-based combination therapies with either a carbapenem, minocycline, or eravacycline remain the treatment of choice for MDR, particularly carbapenem-resistant, AB. Incorporating antimicrobial stewardship intervention with RDTs relevant to MDR AB can help avoid potentially toxic combination therapies and catalyze the most important modifiable risk factor for mortality-time to effective therapy. Further research efforts into pharmacokinetic/pharmacodynamic-based dose optimization and clinical outcomes data for MDR AB continue to be desperately needed.

Multicenter Evaluation of Colistin Broth Disk Elution and Colistin Agar Test: a Report from the Clinical and Laboratory Standards Institute

Susceptibility testing of the polymyxins (colistin and polymyxin B) is challenging for clinical laboratories. The Clinical and Laboratory Standards Institute (CLSI) Antimicrobial Susceptibility Testing Subcommittee evaluated two methods to enable accurate testing of these agents. These methods were a colistin broth disk elution (CBDE) and a colistin agar test (CAT), the latter of which was evaluated using two inoculum volumes, 1 μl (CAT-1) and 10 μl (CAT-10). The methods were evaluated using a collection of 270 isolates of Enterobacterales, 122 Pseudomonas aeruginosa isolates, and 106 Acinetobacter spp. isolates. Overall, 94.4% of CBDE results were in essential agreement and 97.9% in categorical agreement (CA) with reference broth microdilution MICs. Nine very major errors (VME; 3.2%) and 3 major errors (ME; 0.9%) were observed. With the CBDE, 98.6% CA was observed for Enterobacterales (2.5% VME, 0% ME), 99.3% CA was observed for P. aeruginosa (0% VME, 0.7% ME), and 93.1% CA was observed for Acinetobacter spp. (5.6% VME, 3.3% ME). Overall, CA was 94.9% with 6.8% VME using CAT-1 and improved to 98.3% with 3.9% VME using CAT-10. No ME were observed using either CAT-1 or CAT-10. Using the CAT-1/CAT-10, the CA observed was 99.4%/99.7% for Enterobacterales (1%/0.5% VME), 98.7%/100% for P. aeruginosa (8.3%/0% VME), and 88.5%/92.3% for Acinetobacter spp. (21.4%/14.3% VME). Based on these data, the CLSI antimicrobial susceptibility testing (AST) subcommittee endorsed the CBDE and CAT-10 methods for colistin testing of Enterobacterales and P. aeruginosa.

Current trends in targeted therapy for drug-resistant infections

Escalating antibiotic resistance is now a serious menace to global public health. It may be led to the emergence of "postantibiotic age" in which most of infections are untreatable. At present, there is an essential need to explore novel therapeutic strategies as a strong and sustainable pipeline to combat antibiotic-resistant infections. This review focuses on recent advances in this area including therapeutic antibodies, antimicrobial peptides, vaccines, gene therapy, genome editing, and phage therapy for tackling drug-resistant infections.