Antimicrobial activity of plazomicin against Enterobacteriaceae-producing carbapenemases from 50 Brazilian medical centers

Environmental health of water bodies from a Brazilian Amazon Metropolis based on a conventional and metagenomic approach

AIMS

The present study aimed to use a conventional and metagenomic approach to investigate the microbiological diversity of water bodies in a network of drainage channels and rivers located in the central area of the city of Belém, northern Brazil, which is considered one of the largest cities in the Brazilian Amazon.

METHODS AND RESULTS

In eight of the analyzed points, both bacterial and viral microbiological indicators of environmental contamination-physical-chemical and metals-were assessed. The bacterial resistance genes, drug resistance mechanisms, and viral viability in the environment were also assessed. A total of 473 families of bacteria and 83 families of viruses were identified. Based on the analysis of metals, the levels of three metals (Cd, Fe, and Mn) were found to be above the recommended acceptable level by local legislation. The levels of the following three physicochemical parameters were also higher than recommended: biochemical oxygen demand, dissolved oxygen, and turbidity. Sixty-three bacterial resistance genes that conferred resistance to 13 different classes of antimicrobials were identified. Further, five mechanisms of antimicrobial resistance were identified and viral viability in the environment was confirmed.

CONCLUSIONS

Intense human actions combined with a lack of public policies and poor environmental education of the population cause environmental degradation, especially in water bodies. Thus, urgent interventions are warranted to restore the quality of this precious and scarce asset worldwide.

Carbapenem-resistant Gram-negative bacteria (CR-GNB) in ICUs: resistance genes, therapeutics, and prevention - a comprehensive review

Intensive care units (ICUs) are specialized environments dedicated to the management of critically ill patients, who are particularly susceptible to drug-resistant bacteria. Among these, carbapenem-resistant Gram-negative bacteria (CR-GNB) pose a significant threat endangering the lives of ICU patients. Carbapenemase production is a key resistance mechanism in CR-GNB, with the transfer of resistance genes contributing to the extensive emergence of antimicrobial resistance (AMR). CR-GNB infections are widespread in ICUs, highlighting an urgent need for prevention and control measures to reduce mortality rates associated with CR-GNB transmission or infection. This review provides an overview of key aspects surrounding CR-GNB within ICUs. We examine the mechanisms of bacterial drug resistance, the resistance genes that frequently occur with CR-GNB infections in ICU, and the therapeutic options against carbapenemase genotypes. Additionally, we highlight crucial preventive measures to impede the transmission and spread of CR-GNB within ICUs, along with reviewing the advances made in the field of clinical predictive modeling research, which hold excellent potential for practical application.

In Vitro Antimicrobial Activity of Five Newly Approved Antibiotics against Carbapenemase-Producing Enterobacteria-A Pilot Study in Bulgaria

To solve the problem with pan-drug resistant and extensively drug-resistant Gram-negative microbes, newly approved drugs such as ceftazidime/avibactam, cefiderocol, plazomicin, meropenem/vaborbactam, and eravacycline have been introduced in practice. The aim of the present study was to collect carbapenemase-producing clinical Enterobacterales isolates, to characterize their carbapenemase genes and clonal relatedness, and to detect their susceptibility to commonly used antimicrobials and the above-mentioned newly approved antibiotics. Sixty-four carbapenemase producers were collected in a period of one year from four Bulgarian hospitals, mainly including Klebsiella pneumoniae (89% of the isolates) and also single Proteus mirabilis, Providencia stuartii and Citrobacter freundii isolates. The main genotype was blaNDM-1 (in 61%), followed by blaKPC-2 (23%), blaVIM-1 (7.8%) and blaOXA-48 (7.8%). Many isolates showed the presence of ESBL (blaCTX-M-15/-3 in 76.6%) and AmpC (blaCMY-4 in 37.5% or blaCMY-99 in 7.8% of isolates). The most common MLST type was K. pneumoniae ST11 (57.8%), followed by ST340 (12.5%), ST258 (6.3%) and ST101 (6.3%). The isolates were highly resistant to standard-group antibiotics, except they were susceptible to tigecycline (83.1%), colistin (79.7%), fosfomycin (32.8%), and aminoglycosides (20.3-35.9%). Among the newly approved compounds, plazomicin (90.6%) and eravacycline (76.3%) showed the best activity. Susceptibility to ceftazidime/avibactam and meropenem/vaborbactam was 34.4% and 27.6%, respectively. For cefiderocol, a large discrepancy was observed between the percentages of susceptible isolates according to EUCAST susceptibility breakpoints (37.5%) and those of CLSI (71.8%), detected by the disk diffusion method. This study is the first report to show patterns of susceptibility to five newly approved antibiotics among molecularly characterized isolates in Bulgaria. The data may contribute to both the improvement of treatment of individual patients and the choice of infection control strategy and antibiotic policy.

Different concentrations of vancomycin with gentamicin loaded PMMA to inhibit biofilm formation of Staphylococcus aureus and their implications

BACKGROUND

This study aimed to evaluate different concentrations of vancomycin and/or gentamicin loaded polymethylmethacrylate (PMMA) against biofilm formation of Staphylococcus aureus.

METHODS

Biofilm production of S. aureus in PMMA loaded with different concentrations of vancomycin and gentamicin were evaluated by quantitative analysis of biofilm cells, scanning electronic microscopy, viability assay, Fourier transform infrared spectroscopy, and checkerboard. Statistical analysis was performed by Mann Whitney test. The difference in colony forming units per mL was significant when p < 0.05.

RESULTS

All loaded PMMA presented a reduction in the number of colony forming units per mL (p < 0.05). The gentamicin-loaded PMMA could inhibits the grown of sessile cells (p < 0.05), where the group vancomycin 4 g + gentamicin 500 mg presented a better result. The Fourier transform infrared spectra showed no significant differences, and checkerboard of vancomycin and gentamicin showed synergism.

CONCLUSION

Effects against adherence and bacterial development in PMMA loaded with antibiotics were mainly seen in the group vancomycin 4 g + gentamicin 500 mg, and synergic effect can be applied in antibiotic-loaded cement.

Optimization of Antimicrobial Stewardship Programs Using Therapeutic Drug Monitoring and Pharmacokinetics-Pharmacodynamics Protocols: A Cost-Benefit Review

PURPOSE

Antimicrobial stewardship programs are important for reducing antimicrobial resistance because they can readjust antibiotic prescriptions to local guidelines, switch intravenous to oral administration, and reduce hospitalization times. Pharmacokinetics-pharmacodynamics (PK-PD) empirically based prescriptions and therapeutic drug monitoring (TDM) programs are essential for antimicrobial stewardship, but there is a need to fit protocols according to cost benefits. The cost benefits can be demonstrated by reducing toxicity and hospital stay, decreasing the amount of drug used per day, and preventing relapses in infection. Our aim was to review the data available on whether PK-PD empirically based prescriptions and TDM could improve the cost benefits of an antimicrobial stewardship program to decrease global hospital expenditures.

METHODS

A narrative review based on PubMed search with the relevant studies of vancomycin, aminoglycosides, beta-lactams, and voriconazole.

RESULTS

TDM protocols demonstrated important cost benefit for patients treated with vancomycin, aminoglycosides, and voriconazole mainly due to reduce toxicities and decreasing the hospital length of stay. In addition, PK-PD strategies that used infusion modifications to meropenem, piperacillin-tazobactam, ceftazidime, and cefepime, such as extended or continuous infusion, demonstrated important cost benefits, mainly due to reducing daily drug needs and lengths of hospital stays.

CONCLUSIONS

TDM protocols and PK-PD empirically based prescriptions improve the cost-benefits and decrease the global hospital expenditures.

Dissemination of NDM-producing bacteria in Southern Brazil

BACKGROUND

The dissemination of NDM-1 carbapenemases (New Delhi Metallo-β-lactamase) is a global public health problem, mainly in developing countries. The aim of this study was to characterize the spread of NDM-producing bacteria in the Southern Brazilian states analyzing epidemiological, molecular, and antimicrobial susceptibility aspects.

METHODS

A total of 10,684 carbapenem-resistant isolates of Enterobacterales, Pseudomonas spp. and Acinetobacter spp. obtained from several hospitals in eight cities in Southern Brazil were screened, and 486 NDM-producing bacteria were selected.

RESULTS

The incidence varied from 0.5 to 77 cases/100.000 habitants. ST11, ST15, ST340 and ST674 were the most common in K. pneumoniae. A total of 5 plasmids were identified in one K. pneumoniae strain: Col440I, Col440II, IncFIA(HI1), IncFIB(K), IncFIB(pQil)/ IncFII(K), and IncR.

CONCLUSIONS

The number of patients with NDM-producing bacteria has increased in Southern Brazil, whose gene is present in different plasmids, explaining the expansion of this enzyme.

Antimicrobial Treatment of Staphylococcus aureus Biofilms

Staphylococcus aureus is a microorganism frequently associated with implant-related infections, owing to its ability to produce biofilms. These infections are difficult to treat because antimicrobials must cross the biofilm to effectively inhibit bacterial growth. Although some antibiotics can penetrate the biofilm and reduce the bacterial load, it is important to understand that the results of routine sensitivity tests are not always valid for interpreting the activity of different drugs. In this review, a broad discussion on the genes involved in biofilm formation, quorum sensing, and antimicrobial activity in monotherapy and combination therapy is presented that should benefit researchers engaged in optimizing the treatment of infections associated with S. aureus biofilms.

Efficacy and safety of plazomicin in the treatment of Enterobacterales infections: A meta-analysis of randomized controlled trials

Background

In the present study, we aimed to compare the efficacy and safety of plazomicin with comparators for the treatment of Enterobacterales infections.

Methods

Randomized controlled trials (RCTs) assessing plazomicin for Enterobacterales infections were searched on the PubMed, Embase, and Cochrane Library databases. Meta-analyses were used to evaluate the efficacy and safety in RCTs.

Results

A total of 3 RCTs consisting of 761 patients were included in the present analysis. The study population included complex urinary tract infections (cUTIs), bloodstream infections (BSIs), and hospital-acquired pneumonia (HAP). Plazomicin had a clinical remission rate in the modified intention-to-treat (MITT) population that was similar to that of comparators (odds ratio [OR], 1.02; 95% CI, 0.60–1.73; I² = 45%) in the pooled analysis of the 3 studies. The overall microbiologic eradication rate in the microbiological MITT (mMITT) population was similar to that of the comparators group (OR, 1.46; 95% CI, 0.72–2.95; I² = 0%). However, the microbiologic recurrence rate of plazomicin for Enterobacterales was lower than that in the comparators group (OR, 0.38; 95% CI, 0.17–0.86; P = .02; I² = 0%). No significant differences were found between plazomicin and comparators for the risk of any adverse events (OR, 0.78; 95% CI, 0.55–1.11; I² = 0%).

Conclusions

Plazomicin is as good as comparators in terms of efficacy and tolerance in the treatment of Enterobacterales infections. Therefore, plazomicin is a suitable choice for antibiotic treatment in adult patients with cUTIs, BSIs, or HAP.

In-vitro activity of plazomicin, meropenem-vaborbactam, and omadacycline against carbapenem-resistant Gram-negative isolates in Egypt

Anti-microbial resistance is an escalating worldwide threat. Thus, there is an utmost necessity for the introduction of novel anti-microbial agents. This research aimed to evaluate the in-vitro activity of plazomicin, meropenem-vaborbactam, and omadacycline against carbapenem-resistant Gram-negative isolates gathered from one Egyptian University group of Hospitals. 210 intensive care units (ICU) and 113 non-ICU samples were included. Resistance to carbapenems was reported in 37.5% and 21.05% of the isolated Gram-negative ICU and non-ICU organisms respectively (P < 0.001). Via disc diffusion, the sensitivity rates for carbapenem-resistant non-ICU and ICU strains were 68.8% & 64.4% for plazomicin, 68.8% & 48.9% for meropenem-vaborbactam, and 56.25% & 44.5% for omadacycline, respectively. Regarding MIC₅₀/_90, it was 1/16 μg/mL for plazomicin and 4/32 μg/mL for both meropenem-vaborbactam and omadacycline separately. In conclusion, plazomicin displayed potent activity against carbapenem-resistant strains. Moreover, meropenem-vaborbactam and omadacycline demonstrated satisfactory results.

Current status of NDM-producing Enterobacterales in Brazil: a narrative review

New Delhi metallo-β-lactamase (NDM)-producing Enterobacterales was first detected in Brazil in 2014, in a Providencia rettgeri isolate recovered from surveillance swabs in the Southern region. Since then, an increasing number of NDM enzymes have been reported in different species. Nevertheless, comprehensive data on the current epidemiology of NDM-producing Enterobacterales in Brazil are lacking. Therefore, this study reviewed the available information on the status of NDM-producing bacteria in Brazil. The main finding was the diversity of bacteria producing NDM, including Klebsiella, Enterobacter, Morganella, Proteus, Escherichia, and Providencia. Limited data on clonality are available, but a few studies report different clonal backgrounds in NDM-producing K. pneumoniae, likely indicating local outbreaks. Over the years, a rise in the number of reported strains in different locations has been verified; however, different biases may have contributed to this finding. Therefore, a national surveillance study is warranted to identify the actual prevalence and incidence of NDM-producing Enterobacterales in Brazil and their role in patient management and outcome.

Epidemiology and in vitro activity of ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, eravacycline, plazomicin, and comparators against Greek carbapenemase-producing Klebsiella pneumoniae isolates

BACKGROUND

The increase in carbapenem-resistant Klebsiella pneumoniae (CRKP) infections is of great concern because of limited treatment options. New antimicrobials were recently approved for clinical therapy. This study evaluated the epidemiology of carbapenemase-producing K. pneumoniae isolates collected at a Greek university hospital during 2017-2020, and their susceptibilities to ceftazidime-avibactam (CAZ/AVI), meropenem-vaborbactam (M/V), imipenem-relebactam (I/R), eravacycline, plazomicin, and comparators.

METHODS

Minimum inhibitory concentrations (MICs) were evaluated by Etest. Only colistin MICs were determined by the broth microdilution method. Carbapenemase genes were detected by PCR. Selected isolates were typed by multilocus sequence typing (MLST).

RESULTS

A total of 266 carbapenemase-producing K. pneumoniae strains were isolated during the 4-year study period. Among them, KPC was the most prevalent (75.6%), followed by NDM (11.7%), VIM (5.6%), and OXA-48 (4.1%). KPC-producing isolates belonged mainly to ST258 and NDM producers belonged to ST11, whereas OXA-48- and VIM producers were polyclonal. Susceptibility to tigecycline, fosfomycin, and colistin was 80.5%, 83.8%, and 65.8%, respectively. Of the novel agents tested, plazomicin was the most active inhibiting 94% of the isolates at ≤ 1.5 μg/ml. CAZ/AVI and M/V inhibited all KPC producers and I/R 98.5% of them. All OXA-48 producers were susceptible to CAZ/AVI and plazomicin. The novel β-lactam/β-lactamase inhibitors (BLBLIs) tested were inactive against MBL-positive isolates, while eravacycline inhibited 61.3% and 66.7% of the NDM and VIM producers, respectively.

CONCLUSIONS

KPC remains the predominant carbapenemase among K. pneumoniae, followed by NDM. Novel BLBLIs, eravacycline, and plazomicin are promising agents for combating infections by carbapenemase-producing K. pneumoniae. However, the emergence of resistance to these agents highlights the need for continuous surveillance and application of enhanced antimicrobial stewardship.

Comparison of in vitro activities of plazomicin and other aminoglycosides against clinical isolates of Klebsiella pneumoniae and Escherichia coli

OBJECTIVES

To compare the in vitro activity of plazomicin and two older aminoglycosides (gentamicin and amikacin) against 180 isolates of Escherichia coli and Klebsiella pneumoniae, including subsets of 60 non-ESBL-producing, 60 ESBL-producing and 60 carbapenem-resistant (46 carrying blaOXA-48, 11 carrying blaNDM and 3 carrying blaOXA-48 and blaNDM) strains.

METHODS

MICs of plazomicin, gentamicin and amikacin were determined by a gradient diffusion method. Gentamicin and amikacin MICs were interpreted according to CLSI criteria and EUCAST breakpoint tables. Plazomicin MICs were interpreted using FDA-defined breakpoints.

RESULTS

All non-ESBL-producing and ESBL-producing isolates were susceptible to plazomicin. The plazomicin susceptibility rate (71.7%) in carbapenem-resistant isolates was significantly higher than those observed for gentamicin (45%) and amikacin (56.7% and 51.7% according to CLSI and EUCAST breakpoints, respectively). Gentamicin, amikacin and plazomicin susceptibility rates (35.6% for gentamicin; 44.4% and 37.8% for amikacin according to CLSI and EUCAST breakpoints, respectively; 64.4% for plazomicin) in carbapenem-resistant K. pneumoniae were significantly lower than those observed for carbapenem-resistant E. coli isolates (73.3% for gentamicin; 93.3% for amikacin and plazomicin). Gentamicin, amikacin and plazomicin susceptibility rates for blaNDM-positive isolates were lower than those observed for blaOXA-48-positive isolates, but differences were not statistically significant. Among the isolates that were non-susceptible to both gentamicin and amikacin, the plazomicin susceptibility rate was less than 30%.

CONCLUSIONS

Although plazomicin showed excellent in vitro activity against carbapenem-susceptible isolates, the plazomicin resistance rate increased to 35.6% among carbapenem-resistant K. pneumoniae and further increased to 45.5% among blaNDM-positive isolates.

Distribution of genes encoding 16S rRNA methyltransferase in plazomicin-nonsusceptible carbapenemase-producing Enterobacterales in Brazil

BACKGROUND

The presence of 16S rRNA methyltranferases (16S-RMTases) in carbapenemase-producing Enterobacterales (CPE) is a major concern because it inactivates all clinical use of aminoglycosides, including plazomicin. The aim of this study is to investigate the prevalence of 16S-RMTases in CPE nonsusceptible to plazomicin collected in different Brazilian hospitals.

METHODS

All isolates with plazomicin MIC ≥ 4 µg/mL (n = 67) were screened for the presence of 16S-RMTases by sequencing.

RESULTS

54 (80.6%) isolates encoded 16S-RMTase genes (41 rmtB1, 7 armA, 3 rmtD2, 1 rmtD1 and 2 rmtC). Among 41 samples rmtB1 positive, 40 co-harbored bla_KPC-2 and 1 bla_OXA-48 gene. Of the seven isolates harboring armA gene, 6 were New Delhi Metallo-beta-lactamase (NDM)-producer. rmtD was only found in isolates Klebsiella pneumoniae Carbapenemase (KPC)-producers, one in Serratia marcescens with rmtD2, not reported in Brazil.

CONCLUSION

The co-existence of 16S-RMTase and CPE is worrisome because of limited treatment options and the endemic characteristic of (KPC) and NDM in Brazil.

Plazomicin: a new aminoglycoside in the fight against antimicrobial resistance

Objective

To review the mechanism of action, mechanisms of resistance, in vitro activity, pharmacokinetics, pharmacodynamics, and clinical data for a novel aminoglycoside.

Data sources

A PubMed search was performed from January 2006 to August 2019 using the following search terms: plazomicin and ACHN-490. Another search was conducted on clinicaltrials.gov for published clinical data. References from selected studies were also used to find additional literature.

Study selection and data extraction

All English-language studies presenting original research (in vitro, in vivo, pharmacokinetic, and clinical) were evaluated.

Data synthesis

Plazomicin has in vitro activity against several multi-drug-resistant organisms, including carbapenem-resistant Enterobacteriaceae. It was Food and Drug Administration (FDA) approved to treat complicated urinary tract infections (cUTIs), including acute pyelonephritis, following phase II and III trials compared with levofloxacin and meropenem, respectively. Despite the FDA Black Box Warning for aminoglycoside class effects (nephrotoxicity, ototoxicity, neuromuscular blockade, and pregnancy risk), it exhibited a favorable safety profile with the most common adverse effects being decreased renal function (3.7%), diarrhea (2.3%), hypertension (2.3%), headache (1.3%), nausea (1.3%), vomiting (1.3%), and hypotension (1.0%) in the largest in-human trial.

Relevance to patient care and clinical practice

Plazomicin will likely be used in the treatment of multi-drug-resistant cUTIs or in combination to treat serious carbapenem-resistant Enterobacteriaceae infections.

Conclusions

Plazomicin appears poised to help fill the need for new agents to treat infections caused by multi-drug-resistant Enterobacteriaceae.

The Infectious Diseases Society of America's 10 × '20 Initiative (10 New Systemic Antibacterial Agents US Food and Drug Administration Approved by 2020): Is 20 × '20 a Possibility?

BACKGROUND

Infections caused by antibiotic-resistant bacteria, including carbapenem-resistant Enterobacteriaceae, have increased in frequency, resulting in significant patient morbidity and mortality. The Infectious Diseases Society of America continues to propose legislative, regulatory, and funding solutions to address this escalating crisis. This report updates the status of development and approval of systemic antibiotics in the United States as of late 2018.

METHODS

We performed a review of the published literature and on-line clinical trials registry at www.clinicaltrials.gov to identify new systemically acting orally and/or intravenously administered antibiotic drug candidates in the development pipeline, as well as agents approved by the US Food and Drug Administration since 2012.

RESULTS

Since our 2013 pipeline status report, the number of new antibiotics annually approved for marketing in the United States has reversed its previous decline, likely influenced by new financial incentives and increased regulatory flexibility. Although our survey demonstrates progress in development of new antibacterial drugs that target infections caused by resistant bacterial pathogens, the majority of recently approved agents have been modifications of existing chemical classes of antibiotics, rather than new chemical classes. Furthermore, larger pharmaceutical companies continue to abandon the field, and smaller companies face financial difficulties as a consequence.

CONCLUSIONS

Unfortunately, if 20 × '20 is achieved due to efforts embarked upon in decades past, it could mark the apex of antibiotic drug development for years to come. Without increased regulatory, governmental, industry, and scientific support and collaboration, durable solutions to the clinical, regulatory, and economic problems posed by bacterial multidrug resistance will not be found.

In vitro activity of plazomicin compared to other clinically relevant aminoglycosides in carbapenem-resistant Enterobacteriaceae

We evaluated the in vitro activity of plazomicin against other aminoglycosides in 122 clinical carbapenem-resistant Enterobacteriaceae isolates using several clinical susceptibility breakpoints. Plazomicin had excellent in vitro activity with 98% overall susceptibility. Amikacin was the next most active with 86% overall susceptibility. This dropped to 55% when switching from Clinical Laboratory and Standards Institute to US Committee on Antimicrobial Susceptibility Testing breakpoints.

Activity of Plazomicin Tested against Enterobacterales Isolates Collected from U.S. Hospitals in 2016-2017: Effect of Different Breakpoint Criteria on Susceptibility Rates among Aminoglycosides

Plazomicin was active against 97.0% of 8,783 Enterobacterales isolates collected in the United States (2016 and 2017), and only 6 isolates carried 16S rRNA methyltransferases conferring resistance to virtually all aminoglycosides. Plazomicin (89.2% to 95.9% susceptible) displayed greater activity than amikacin (72.5% to 78.6%), gentamicin (30.4% to 45.9%), and tobramycin (7.8% to 22.4%) against carbapenem-resistant and extensively drug-resistant isolates. The discrepancies among the susceptibility rates for these agents was greater when applying breakpoints generated using the same stringent contemporary methods applied to determine plazomicin breakpoints.

In Vitro Activity of Plazomicin Compared to Amikacin, Gentamicin, and Tobramycin against Multidrug-Resistant Aerobic Gram-Negative Bacilli

The worldwide spread of multidrug-resistant Enterobacterales is a serious threat to public health. Here, we compared the MICs of plazomicin, amikacin, gentamicin, and tobramycin against 303 multinational multidrug-resistant Gram-negative bacilli. We followed Clinical and Laboratory Standards Institute (CLSI) guidelines and applied CLSI breakpoints as well as those of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for amikacin, gentamicin, and tobramycin and of the U.S. Food and Drug Administration for plazomicin. Overall, the highest percentage of susceptible isolates (80.2%) was demonstrated for plazomicin, which had the lowest MIC₅₀ (1 μg/ml) of the aminoglycosides studied. Of the 42 isolates resistant to plazomicin, 34 had MICs of ≥128 μg/ml, with 33 of the 34 having MICs of >128 μg/ml for amikacin, gentamicin, and tobramycin. Among the 42 bla _NDM-positive isolates, 35.7% were plazomicin susceptible, with the percentage of isolates susceptible to amikacin being 38.1% or 35.7% when applying the CLSI or EUCAST breakpoint, respectively. The 20 bla _OXA-48-like-positive isolates showed 50.0% susceptibility to plazomicin. Among 35 isolates with bla _CTX-M as their only characterized resistance mechanism, 68.6% were plazomicin susceptible, while the percentage susceptible to amikacin was 74.3% or 62.9% when applying the CLSI or EUCAST breakpoint, respectively. Among the 117 bla _KPC-positive isolates, 94.9% were susceptible to plazomicin, whereas when the CLSI and EUCAST breakpoints were applied, 43.6% and 25.6%, respectively, were susceptible to amikacin; 56.4% and 44.4%, respectively, were susceptible to gentamicin; and 5.1% and 4.3%, respectively, were susceptible to tobramycin.

Plazomicin: A Novel Aminoglycoside for the Treatment of Resistant Gram-Negative Bacterial Infections

Plazomicin is a novel semisynthetic parenteral aminoglycoside that inhibits bacterial protein synthesis. It was approved by the United States Food and Drug Administration for use in adults with complicated urinary tract infections (cUTI), including pyelonephritis. Plazomicin displays potent in vitro activity against Enterobacteriaceae, including both extended-spectrum β-lactamase-producing and carbapenem-resistant isolates. Plazomicin's enhanced Enterobacteriaceae activity is due to its stability to commonly encountered aminoglycoside-modifying enzymes that compromise the activity of traditional aminoglycosides. Plazomicin resistance in Enterobacteriaceae is via modification of the ribosomal binding site due to expression of 16S rRNA methyltransferases. Plazomicin does not display improved activity over traditional aminoglycosides against other problematic resistant Gram-negative bacteria, namely Pseudomonas aeruginosa and Acinetobacter baumannii. Plazomicin has been assessed in two phase III randomized controlled trials. The EPIC trial compared plazomicin and meropenem for the management of cUTI. In this trial, plazomicin demonstrated superiority in composite cure (81.7% vs 70.1%; difference 11.6%; 95% confidence interval [CI] 2.7-25.7) at the test-of-cure visit, which was driven by enhanced sustained microbiological eradication. The CARE trial compared plazomicin-based and colistin-based combinations in patients with serious infections due to carbapenem-resistant Enterobacteriaceae (CRE). In this analysis, plazomicin-based combinations were associated with numerically decreased mortality or serious disease-related complications when compared with colistin-based combinations (23.5% vs 50%, respectively; 90% CI -0.7 to 51.2). Furthermore, plazomicin was also associated with a lower incidence of nephrotoxicity than colistin. However, small sample sizes limit the interpretation of the findings in the CARE trial. Plazomicin is a novel aminoglycoside that offers clinicians an additional option for the management of CRE infections, with superior activity compared with traditional aminoglycosides and potentially improved efficacy and decreased toxicity compared with colistin.

External validation of the INCREMENT-CPE mortality score in a carbapenem-resistant Klebsiella pneumoniae bacteraemia cohort: the prognostic significance of colistin resistance

External validation of the INCREMENT-CPE risk score (ICS) for 30-day all-cause mortality is needed. There is also scarce information about whether colistin resistance influences the prognosis of carbapenem-resistant Klebsiella pneumoniae (CRKp) bacteraemia. In this study, the ability of ICS to predict all-cause mortality in the KAPECOR cohort was calculated using the area under the receiver operating characteristic (AUROC) curve. The association of colistin resistance with mortality was studied. The ICS showed an AUROC curve of 0.77 (95% CI 0.68-0.86). A cut-off of 8 points showed 96.8% sensitivity and 50.7% specificity. Mortality of low-risk patients was not different in those treated with monotherapy versus combination therapy. However, mortality of high-risk patients treated with combination therapy (37.8%) was significantly lower than in those treated with monotherapy (68.4%) (P = 0.008). To study the prognostic significance of colistin resistance, 83 selected cases of bacteraemia due to colistin-susceptible CRKp were obtained from the INCREMENT cohort for comparison. Colistin resistance could not be shown to be associated with higher mortality in either the high-risk ICS group [adjusted odds ratio (aOR) = 1.56, 95% CI 0.69-3.33; P = 0.29] or in 37 ICS-matched pairs (aOR = 1.38, 95% CI 0.55-3.42; P = 0.49), or in a sensitivity analysis including only KPC isolates (aOR = 1.81, 95% CI 0.73-4.57; P = 0.20), but the precision of estimates was low. These results validate ICS for all-cause mortality and to optimise targeted therapy for CRKp bacteraemia. Colistin resistance was not clearly associated with increased mortality.

Plazomicin Is Active Against Metallo-β-Lactamase-Producing Enterobacteriaceae

Plazomicin is an aminoglycoside that was approved in June 2018 by the US Food and Drug Administration for the treatment of complicated urinary tract infections, including pyelonephritis, due to Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Proteus mirabilis. Plazomicin was engineered to overcome the most common aminoglycoside resistance mechanism, inactivation by aminoglycoside-modifying enzymes, but is not active against the less common 16S ribosomal RNA methyltransferases (16S-RMTase), which confer target site modification. As an aminoglycoside, plazomicin maintains activity against Enterobacteriaceae that express resistance mechanisms to other antibiotic classes, including metallo-β-lactamases. Therefore, in the absence of a 16S-RMTase, plazomicin is active against metallo-β-lactamase-producing Enterobacteriaceae.

Nationwide epidemiology of carbapenem resistant Klebsiella pneumoniae isolates from Greek hospitals, with regards to plazomicin and aminoglycoside resistance

BACKGROUND

To evaluate the in vitro activities of plazomicin and comparator aminoglycosides and elucidate the underlying aminoglycoside resistance mechanisms among carbapenemase-producing K. pneumoniae isolates collected during a nationwide surveillance study in Greek hospitals.

METHODS

Three hundred single-patient carbapenemase-producing K. pneumoniae isolates were studied, including 200 KPC-, 50 NDM-, 21 VIM-, 14 KPC & VIM-, 12 OXA-48-, two NDM & OXA- and one KPC & OXA-producing isolates. Susceptibility testing was performed by broth microdilution, and minimum inhibitory concentrations (MICs) interpreted per EUCAST breakpoints. Carbapenemase-, aminoglycoside modifying enzyme- and 16S rRNA methylase- encoding genes were detected by PCR.

RESULTS

Of 300 isolates tested, 5.7% were pandrug resistant and 29.3% extensively drug resistant. Plazomicin inhibited 87.0% of the isolates at ≤2 mg/L, with MIC₅₀/MIC₉₀ of 0.5/4 mg/L. Apramycin (a veterinary aminoglycoside) inhibited 86.7% of the isolates at ≤8 mg/L and was the second most active drug after plazomicin, followed by gentamicin (S, 43%; MIC₅₀/MIC₉₀, 4/> 256) and amikacin (S, 18.0%; MIC₅₀/MIC₉₀, 32/128). Twenty-three (7.7%) isolates (16 KPC-, 6 VIM- and one KPC & OXA-48-producers) exhibited MICs ≥64 mg/L for plazomicin, and harbored rmtB (n = 22) or armA (n = 1). AAC(6')-Іb was the most common aminoglycoside modifying enzyme (84.7%), followed by AAC(3΄)-IIa (25.3%), while those two enzymes were co-produced by 21.4% of the isolates.

CONCLUSIONS

Plazomicin retains activity against most carbapenemase-producing K. pneumoniae isolated from Greek hospitals, with MICs consistently lower than those of the other aminoglycosides, even in the presence of aminoglycoside modifying enzymes. Dissemination of 16S- rRNA methylases in 8% of the isolates is an unwelcome event that needs strict infection control measures and rigorous stewardship interventions.

In Vitro Activity of Plazomicin against Gram-Negative and Gram-Positive Bacterial Pathogens Isolated from Patients in Canadian Hospitals from 2013 to 2017 as Part of the CANWARD Surveillance Study

The Clinical and Laboratory Standards Institute (CLSI) broth microdilution method was used to evaluate the in vitro activities of plazomicin and comparator antimicrobial agents against 7,712 Gram-negative and 4,481 Gram-positive bacterial pathogens obtained from 2013 to 2017 from patients in Canadian hospitals as part of the CANWARD Surveillance Study. Plazomicin demonstrated potent in vitro activity against Enterobacteriaceae (MIC₉₀ ≤ 1 µg/ml for all species tested except Proteus mirabilis and Morganella morganii), including aminoglycoside-nonsusceptible, extended-spectrum β-lactamase (ESBL)-positive, and multidrug-resistant (MDR) isolates. Plazomicin was equally active against methicillin-susceptible and methicillin-resistant isolates of Staphylococcus aureus.

Frequency of 16S ribosomal RNA methyltransferase detection among Escherichia coli and Klebsiella pneumoniae clinical isolates obtained from patients in Canadian hospitals (CANWARD, 2013-2017)

Pan-aminoglycoside (amikacin, gentamicin, tobramycin, plazomicin)-resistant Escherichia coli and Klebsiella pneumoniae clinical isolates from patients in Canadian Hospitals (2013-2017) were evaluated by whole genome sequencing for 16S ribosomal RNA methyltransferase genes. The rmtB gene was detected in 2 isolates (1 of 3094 E. coli [0.03%], 1 of 1039 K. pneumoniae [0.1%]).

Treatment of Infections by OXA-48-Producing Enterobacteriaceae

Carbapenemase-producing Enterobacteriaceae (CPE) contribute significantly to the global public health threat of antimicrobial resistance. OXA-48 and its variants are unique carbapenemases with low-level hydrolytic activity toward carbapenems but no intrinsic activity against expanded-spectrum cephalosporins. bla _OXA-48 is typically located on a plasmid but may also be integrated chromosomally, and this gene has progressively disseminated throughout Europe and the Middle East. Despite the inability of OXA-48-like carbapenemases to hydrolyze expanded-spectrum cephalosporins, pooled isolates demonstrate high variable resistance to ceftazidime and cefepime, likely representing high rates of extended-spectrum beta-lactamase (ESBL) coproduction. In vitro data from pooled studies suggest that avibactam is the most potent beta-lactamase inhibitor when combined with ceftazidime, cefepime, aztreonam, meropenem, or imipenem. Resistance to novel avibactam combinations such as imipenem-avibactam or aztreonam-avibactam has not yet been reported in OXA-48 producers, although only a few clinical isolates have been tested. Although combination therapy is thought to improve the chances of clinical cure and survival in CPE infection, successful outcomes were seen in ∼70% of patients with infections caused by OXA-48-producing Enterobacteriaceae treated with ceftazidime-avibactam monotherapy. A carbapenem in combination with either amikacin or colistin has achieved treatment success in a few case reports. Uncertainty remains regarding the best treatment options and strategies for managing these infections. Newly available antibiotics such as ceftazidime-avibactam show promise; however, recent reports of resistance are concerning. Newer choices of antimicrobial agents will likely be required to combat this problem.

The Infinity War: How to Cope with Carbapenem-resistant Enterobacteriaceae

Carbapenem-resistant Enterobacteriaceae (CRE) are now spread worldwide. In Korea, the number of CRE isolation is rapidly increasing, and impending endemicity is a concern. To cope well with CRE, thorough infection control, such as active surveillance, early detection, strict contact precaution, cleaning the environment, and antibiotic stewardship is very important. Therapeutic options include polymyxin, tigecycline, fosfomycin or the combination of them with carbapenem, which is currently the mainstay of treatment. In addition, various combination regimens with new carbapenemase inhibitors such as avibactam, vaborbactam, or relebactam, and other classes of antimicrobials such as plazomicin and siderophore cephalosporin are in the process of evaluation.