Occurrence of multi-carbapenemases producers among carbapenemase-producing Enterobacterales and in vitro activity of combinations including cefiderocol, ceftazidime-avibactam, meropenem-vaborbactam, and aztreonam in the COVID-19 era

Emergence of carbapenem-resistant Klebsiella pneumoniae species complex from agrifood systems: detection of ST6326 co-producing KPC-2 and NDM-1

BACKGROUND

Klebsiella pneumoniae species complex (KpSC) is an important disseminator of carbapenemase-encoding genes, mainly blaKPC-2 and blaNDM-1, from hospitals to the environment. Consequently, carbapenem-resistant strains can be spread through the agrifood system, raising concerns about food safety. This study therefore aimed to isolate carbapenem-resistant KpSC strains from the agricultural and environmental sectors and characterize them using phenotypic, molecular, and genomic analyses.

RESULTS

Klebsiella pneumoniae and Klebsiella quasipneumoniae strains isolated from soils used for lemon, guava, and fig cultivation, and from surface waters, displayed an extensive drug-resistance profile and carried blaKPC-2, blaNDM-1, or both. In addition to carbapenemase-encoding genes, KpSC strains harbor a broad resistome (antimicrobial resistance and metal tolerance) and present putative hypervirulence. Soil-derived K. pneumoniae strains were assigned as high-risk clones (ST11 and ST307) and harbored the blaKPC-2 gene associated with Tn4401b and Tn3-like elements on IncN-pST15 and IncX5 plasmids. In surface waters, the coexistence of blaKPC-2 and blaNDM-1 genes was identified in K. pneumoniae ST6326, a new carbapenem-resistant regional Brazilian clone. In this case, blaKPC-2 with Tn4401a isoform and blaNDM-1 associated with a Tn125-like transposon were located on different plasmids. Klebsiella quasipneumoniae ST526 also presented the blaNDM-1 gene associated with a Tn3000 transposon on an IncX3 plasmid.

CONCLUSION

These findings provide a warning regarding the transmission of carbapenemase-positive KpSC across the agricultural and environmental sectors, raising critical food safety and environmental issues. © 2024 Society of Chemical Industry.

Occurrence of multi-carbapenemase-producing Enterobacterales in a tertiary hospital in Madrid (Spain): A new epidemiologic scenario

INTRODUCTION

Multi-carbapenemase-producing Enterobacterales (M-CPE) are increasingly described. We characterized the M-CPE isolates prospectively recovered in our hospital (Madrid, Spain) over two years (2021-2022).

METHODS

We collected 796 carbapenem resistant Enterobacterales (CRE) from clinical and surveillance samples. Carbapenemase production was confirmed with phenotypic (immunochromatographic, disk diffusion) and molecular (PCR, WGS) techniques. Antimicrobial susceptibility was evaluated by a standard broth microdilution method. Clinical and demographic data were collected.

RESULTS

Overall, 23 M-CPE (10 Klebsiella pneumoniae, 6 Citrobacter freundii complex, 3 Escherichia coli, 2 Klebsiella oxytoca, and 2 Enterobacter hormaechei) isolates were recovered from 17 patients (3% with CPE, 0.26-0.28 cases per 1000 admissions). OXA-48 + KPC-3 (7/23) and KPC-3 + VIM-1 (5/23) were the most frequent carbapenemase combinations. All patients had prior antibiotics exposure, including carbapenems (8/17). High resistance rates to ceftazidime/avibactam (14/23), imipenem/relebactam (16/23) and meropenem/vaborbactam (7/23) were found. Ceftazidime/avibactam + aztreonam combination was synergistic in all metallo-β-lactamase producers. Clonal and non-clonal related isolates were found, particularly in K. pneumoniae (5 ST29, 3 ST147, 3 ST307) and C. freundii (3 ST8, 2 ST125, 1 ST563). NDM-1 + OXA-48 was introduced with the ST147-K. pneumoniae high-risk clone linked to the transfer of a Ukrainian patient. We identified four possible nosocomial clonal transmission events between patients of the same clone with the same combination of carbapenemases (KPC-3 + VIM-1-ST29-K. pneumoniae, NDM-1 + OXA-48-ST147-K. pneumoniae and KPC-2 + VIM-1-ST145-K. oxytoca). Carbapenemase-encoding genes were located on different plasmids, except for VIM-1 + KPC-2-ST145-K. oxytoca. Cross-species transmission and a possible acquisition overtime was found, particularly between K. pneumoniae and E. coli producing OXA-48 + KPC-3.

CONCLUSION

M-CPE is an emerging threat in our hospital. Co-production of different carbapenemases, including metallo-β-lactamases, limits therapeutic options and depicts the need to reinforce infection control measures.

Characterization of carbapenemase-producing Enterobacterales from rectal swabs of patients in the intensive care units of a tertiary hospital in Cali-Colombia

Background

Carbapenemase-producing Enterobacterales (CPE) represents a significant threat to global health. This study aimed to characterize clinically and molecularly the CPE isolated from rectal swabs of patients in the intensive care units (ICUs) of a tertiary hospital in Cali, Colombia.

Methods

This was a cross-sectional observational study. Rectal swabs from patients admitted to the ICUs were collected. Bacterial identification and carbapenemase production were determined using phenotypic and molecular methods. Demographic and clinical data were extracted from electronic medical records.

Results

The study included 223 patients. Thirty-six patients (36/223, 16.14 %) were found to be colonized or infected by CPE. Factors such as prolonged stay in the ICU, previous exposure to carbapenem antibiotics, use of invasive procedures, and admission due to trauma were associated with CPE. Klebsiella pneumoniae (52.5 %) was the most prevalent microorganism, and the dominant carbapenemases identified were KPC (57.8 %) and NDM (37.8 %).

Conclusion

Distinguishing carbapenemase subtypes can provide crucial insights for controlling dissemination in ICUs in Cali, Colombia.

In vitro activity of cefiderocol against European Enterobacterales, including isolates resistant to meropenem and recentβ-lactam/β-lactamase inhibitor combinations

Carbapenem-resistant Enterobacterales represent a major health threat and have few approved therapeutic options. Enterobacterales isolates were collected from hospitalized inpatients from 49 sites in six European countries (1 January-31 December 2020) and underwent susceptibility testing to cefiderocol and β-lactam/β-lactamase inhibitor combinations. Meropenem-resistant (MIC >8 mg/L) and cefiderocol-susceptible isolates were analyzed by PCR, and cefiderocol-‍resistant isolates by whole-genome sequencing, to identify resistance mechanisms. Overall, 1,909 isolates (including 970 Klebsiella spp., 382 Escherichia coli, and 244 Enterobacter spp.) were collected, commonly from bloodstream infections (43.6%). Cefiderocol susceptibility was higher than approved β-lactam/β-lactamase inhibitor combinations and largely comparable to cefepime-taniborbactam and aztreonam-avibactam against all Enterobacterales (98.1% vs 78.1%-‍97.4% and 98.7%-99.1%, respectively) and Enterobacterales resistant to meropenem (n = 148, including 125 Klebsiella spp.; 87.8% vs 0%-71.6% and 93.2%-98.6%, respectively), β-lactam/β-lactamase inhibitor combinations (66.7%-‍92.1% vs 0%-‍88.1% and 66.7%-97.9%, respectively), and to both meropenem and β-‌lactam/β-lactamase inhibitor combinations (61.9%-65.9% vs 0%-‍20.5% and 76.2%-97.7%, respectively). Susceptibilities to approved and developmental β-lactam/β-lactamase inhibitor combinations against cefiderocol-resistant Enterobacterales (n = 37) were 10.8%-‍56.8% and 78.4%-94.6%, respectively. Most meropenem-resistant Enterobacterales harbored Klebsiella pneumoniae carbapenemase (110/148) genes, although metallo-β-lactamase (35/148) and oxacillinase (OXA) carbapenemase (6/148) genes were less common; cefiderocol susceptibility was retained in β-lactamase producers, other than NDM, AmpC, and non-carbapenemase OXA producers. Most cefiderocol-resistant Enterobacterales had multiple resistance mechanisms, including ≥1 iron uptake-related mutation (37/37), carbapenemase gene (33/37), and ftsI mutation (24/37). The susceptibility to cefiderocol was higher than approved β-lac‌tam/β-lactamase inhibitor combinations against European Enterobacterales, including meropenem- and β-lactam/β-lactamase inhibitor combination-resistant isolates.

IMPORTANCE

This study collected a notably large number of Enterobacterales isolates from Europe, including meropenem- and β-lactam/β-lactamase inhibitor combination-resistant isolates against which the in vitro activities of cefiderocol and developmental β-lactam/β-lactamase inhibitor combinations were directly compared for the first time. The MIC breakpoint for high-dose meropenem was used to define meropenem resistance, so isolates that would remain meropenem resistant with doses clinically available to patients were included in the data. Susceptibility to cefiderocol, as a single active compound, was high against Enterobacterales and was higher than or comparable to available β-lactam/β-lactamase inhibitor combinations. These results provide insights into the treatment options for infections due to Enterobacterales with resistant phenotypes. Early susceptibility testing of cefiderocol in parallel with β-lactam/β-lactamase inhibitor combinations will allow patients to receive the most appropriate treatment option(s) available in a timely manner. This is particularly important when options are more limited, such as against metallo-β-lactamase-producing Enterobacterales.

Synergistic Combination of Aztreonam and Ceftazidime-Avibactam-A Promising Defense Strategy against OXA-48 + NDM Klebsiella pneumoniae in Romania

With the increasing burden of carbapenem-resistant Klebsiella pneumoniae (CR-Kp), including high rates of healthcare-associated infections, treatment failure, and mortality, a good therapeutic strategy for attacking this multi-resistant pathogen is one of the main goals in current medical practice and necessitates the use of novel antibiotics or new drug combinations.

OBJECTIVES

We reviewed the clinical and microbiological outcomes of seven patients treated at the "Agrippa Ionescu" Clinical Emergency Hospital between October 2023 and January 2024, aiming to demonstrate the synergistic activity of the ceftazidime-avibactam (C/A) plus aztreonam (ATM) combination against the co-producers of blaNDM + blaOXA-48-like CR-Kp.

MATERIAL AND METHODS

Seven CR-Kp with blaNDM and blaOXA-48 as resistance mechanisms were tested. Seven patients treated with C/A + ATM were included. The synergistic activity of C/A + ATM was proven through double-disk diffusion in all seven isolates. Resistance mechanisms like KPC, VIM, OXA-48, NDM, IMP, and CTX-M were assessed through immunochromatography.

RESULTS

With a mean of nine days of treatment with the synergistic combination C/A + ATM, all patients achieved clinical recovery, and five achieved microbiological recovery.

CONCLUSIONS

With the emerging co-occurrence of blaOXA-48 and blaNDM among Kp in Romania, the combination of C/A and ATM could be a promising therapeutic option.

Molecular characterization and descriptive analysis of carbapenemase-producing Gram-negative rod infections in Bogota, Colombia

In this study, the genetic differences and clinical impact of the carbapenemase-encoding genes among the community and healthcare-acquired infections were assessed. This retrospective, multicenter cohort study was conducted in Colombia and included patients infected with carbapenem-resistant Gram-negative rods between 2017 and 2021. Carbapenem resistance was identified by Vitek, and carbapenemase-encoding genes were identified by whole-genome sequencing (WGS) to classify the alleles and sequence types (STs). Descriptive statistics were used to determine the association of any pathogen or gene with clinical outcomes. A total of 248 patients were included, of which only 0.8% (2/248) had community-acquired infections. Regarding the identified bacteria, the most prevalent pathogens were Pseudomonas aeruginosa and Klebsiella pneumoniae. In the WGS analysis, 228 isolates passed all the quality criteria and were analyzed. The principal carbapenemase-encoding gene was blaKPC, specifically blaKPC-2 [38.6% (88/228)] and blaKPC-3 [36.4% (83/228)]. These were frequently detected in co-concurrence with blaVIM-2 and blaNDM-1 in healthcare-acquired infections. Notably, the only identified allele among community-acquired infections was blaKPC-3 [50.0% (1/2)]. In reference to the STs, 78 were identified, of which Pseudomonas aeruginosa ST111 was mainly related to blaKPC-3. Klebsiella pneumoniae ST512, ST258, ST14, and ST1082 were exclusively associated with blaKPC-3. Finally, no particular carbapenemase-encoding gene was associated with worse clinical outcomes. The most identified genes in carbapenemase-producing Gram-negative rods were blaKPC-2 and blaKPC-3, both related to gene co-occurrence and diverse STs in the healthcare environment. Patients had several systemic complications and poor clinical outcomes that were not associated with a particular gene.IMPORTANCEAntimicrobial resistance is a pandemic and a worldwide public health problem, especially carbapenem resistance in low- and middle-income countries. Limited data regarding the molecular characteristics and clinical outcomes of patients infected with these bacteria are available. Thus, our study described the carbapenemase-encoding genes among community- and healthcare-acquired infections. Notably, the co-occurrence of carbapenemase-encoding genes was frequently identified. We also found 78 distinct sequence types, of which two were novel Pseudomonas aeruginosa, which could represent challenges in treating these infections. Our study shows that in low and middle-income countries, such as Colombia, the burden of carbapenem resistance in Gram-negative rods is a concern for public health, and regardless of the allele, these infections are associated with poor clinical outcomes. Thus, studies assessing local epidemiology, prevention strategies (including trials), and underpinning genetic mechanisms are urgently needed, especially in low and middle-income countries.

In vitro activity of meropenem-vaborbactam plus aztreonam against metallo-β-lactamase-producing Klebsiella pneumoniae

We evaluated the in vitro activity of meropenem-vaborbactam plus aztreonam (MEV-ATM) against 140 metallo-β-lactamase (MBL)-producing Klebsiella pneumoniae isolates. Among them, 25 isolates (17.9%) displayed minimum inhibitory concentrations (MIC) ≥ 8 µg/mL, while 112 (80.0%) had MIC ≤ 2 µg/mL. Genomic analysis and subsequent gene cloning experiments revealed OmpK36 134-135GD-insertion and increased carbapenemase gene (blaNDM-1 and blaOXA-48-like) copy numbers are the main factors responsible for MEV-ATM non-susceptibility. Notably, MEV-ATM is actively against aztreonam-avibactam-resistant mutants due to CMY-16 mutations.

Virulent Klebsiella pneumoniae ST11 clone carrying blaKPC and blaNDM from patients with and without COVID-19 in Brazil

AIMS

Investigated and compared the occurrence of virulence genes fimH, mrkD, irp2, entB, cps, rmpA, and wabG, resistance genes blaKPC and blaNDM, and the genetic variability and clonal relationship of 29 Klebsiella pneumoniae clinical isolates of patients with and without COVID-19, from a hospital in Brazil.

METHODS AND RESULTS

All isolates were resistant to beta-lactams. The genes were investigated by PCR, and for molecular typing, enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and MLST were used. The detection of blaNDM was greater (n = 23) when compared to that of blaKPC (n = 14). The virulence genes that most occurred were fimH, entB, cps, and wabG, which are responsible for adhesins, siderophore enterobactin, capsule, and lipopolysaccharides, respectively. Among the isolates, 21 distinct genetic profiles were found by ERIC-PCR, with multiclonal dissemination. Four isolates belonged to the ST11 clone.

CONCLUSIONS

The occurrence of the ST11 is worrying as it is a high-risk clone involved in the dissemination of virulent strains throughout the world.

Antimicrobial and Diagnostic Stewardship of the Novel β-Lactam/β-Lactamase Inhibitors for Infections Due to Carbapenem-Resistant Enterobacterales Species and Pseudomonas aeruginosa

Carbapenem-resistant Gram-negative bacterial infections are a major public health threat due to the limited therapeutic options available. The introduction of the new β-lactam/β-lactamase inhibitors (BL/BLIs) has, however, altered the treatment options for such pathogens. Thus, four new BL/BLI combinations-namely, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, and ceftolozane/tazobactam-have been approved for infections attributed to carbapenem-resistant Enterobacterales species and Pseudomonas aeruginosa. Nevertheless, although these antimicrobials are increasingly being used in place of other drugs such as polymyxins, their optimal clinical use is still challenging. Furthermore, there is evidence that resistance to these agents might be increasing, so urgent measures should be taken to ensure their continued effectiveness. Therefore, clinical laboratories play an important role in the judicious use of these new antimicrobial combinations by detecting and characterizing carbapenem resistance, resolving the presence and type of carbapenemase production, and accurately determining the minimum inhibitor concentrations (MICs) for BL/BLIs. These three targets must be met to ensure optimal BL/BLIs use and prevent unnecessary exposure that could lead to the development of resistance. At the same time, laboratories must ensure that results are interpreted in a timely manner to avoid delays in appropriate treatment that might be detrimental to patient safety. Thus, we herein present an overview of the indications and current applications of the new antimicrobial combinations and explore the diagnostic limitations regarding both carbapenem resistance detection and the interpretation of MIC results. Moreover, we suggest the use of alternative narrower-spectrum antibiotics based on susceptibility testing and present data regarding the effect of synergies between BL/BLIs and other antimicrobials. Finally, in order to address the absence of a standardized approach to using the novel BL/BLIs, we propose a diagnostic and therapeutic algorithm, which can be modified based on local epidemiological criteria. This framework could also be expanded to incorporate other new antimicrobials, such as cefiderocol, or currently unavailable BL/BLIs such as aztreonam/avibactam and cefepime/taniborbactam.

In Vitro Activity of "Old" and "New" Antimicrobials against the Klebsiella pneumoniae Complex

The Klebsiella pneumoniae complex is a commonly isolated bacteria in human infections. These opportunistic pathogens pose a serious threat to public health due to their potential transmission to the human population. Resistance to carbapenems is a significant antimicrobial resistance mechanism, leading to limited therapeutic options. Therefore, the aim of this study was to evaluate the in vitro activity of fosfomycin, colistin, ceftazidime-avibactam, and meropenem-vaborbactam against multidrug-resistant K. pneumoniae complex strains. This study involved 160 strains of Gram-negative rods, comprising 138 K. pneumoniae and 22 K. variicola. The minimal inhibitory concentration of fosfomycin was estimated using the agar dilution method, and for colistin, the microdilution method was employed. Susceptibility to ceftazidime-avibactam and meropenem-vaborbactam was determined using the gradient strip method. All analyzed K. pneumoniae complex isolates produced extended-spectrum β-lactamases, and 60.0% exhibited carbapenemases. The majority of the analyzed strains were susceptible to fosfomycin and colistin (62.5%). Among pandrug-resistant K. pneumoniae complex isolates, the highest susceptibility was observed with colistin (43.9%). Fosfomycin demonstrated good activity against ESβLs- and VIM-positive isolates from this complex. Colistin also exhibited satisfactory in vitro activity against VIM- and KPC-positive isolates from the K. pneumoniae complex. Ceftazidime-avibactam displayed good activity against K. pneumoniae complex strains producing ESβLs, KPC, and OXA enzymes. Additionally, meropenem-vaborbactam showed satisfactory in vitro activity against ESβLs- and KPC-positive isolates from this complex.

Multicenter study on the prevalence of colonization due to carbapenem-resistant Enterobacterales strains before and during the first year of COVID-19, Italy 2018-2020

Background

Among multidrug-resistant (MDR) bacteria able to threaten human health, carbapenem-resistant Enterobacterales (CRE) have become a major public health threat globally. National and international guidelines point out the importance of active routine surveillance policies to prevent CRE transmission. Therefore, defining lines of intervention and strategies capable of containing and controlling the spread of CRE is considered determinant. CRE screening is one of the main actions to curb transmission and control outbreaks, outlining the presence and also the prevalence and types of carbapenemase enzymes circulating locally.

Objective

The purpose of this study was to outline the epidemiology of CRE colonization in Italy, detecting CRE-colonized patients at admission and during hospitalization, before and during the first year of COVID-19.

Materials and methods

A total of 11,063 patients admitted to seven different hospitals (Bologna, Catania, Florence, Genoa, Naples, Palermo, and Turin) in Intensive Care Units (ICU) and other wards (non-ICU) located in the North, Center, and South of Italy were enrolled and screened for CRE carriage at admission (T0) and during the first 3 weeks of hospitalization (T1-T3). The study spanned two periods, before (September 2018-Septemeber 2019, I observational period) and during the COVID-19 pandemic (October 2019-September 2020, II observational period).

Results

Overall, the prevalence of CRE-colonized patients at admission in ICU or in other ward, ranged from 3.9 to 11.5%, while a percentage from 5.1 to 15.5% of patients acquired CRE during hospital stay. There were large differences between the I and II period of study according to the different geographical areas and enrolling centers. Overall, comparison of prevalence of CRE-positive patients showed a significant increased trend between I and II observational periods both in ICU and non-ICU wards, mostly in the Southern participating centers. KPC-producing Klebsiella pneumoniae was the most frequent CRE species-carbapenemase combination reported in this study. In particular, the presence of KPC-producing K. pneumoniae was reported in period I during hospitalization in all the CRE-positive patients enrolled in ICU in Turin (North Italy), while in period II at admission in all the CRE-positive patients enrolled in ICU in Catania and in 58.3% of non-ICU CRE-positive patients in Naples (both centers in South Italy).

Conclusion

The prevalence of CRE in Italy highly increased during the COVID-19 pandemic, mostly in the Southern hospital centers. KPC-producing K. pneumoniae was the most frequent colonizing CRE species reported. The results of our study confirmed the crucial value of active surveillance as well as the importance of multicenter studies representing diverse geographical areas even in endemic countries. Differences in CRE colonization prevalence among centers suggest the need for diversified and center-specific interventions as well as for strengthening efforts in infection prevention and control practices and policies.

Global emergence of carbapenem-resistant Klebsiella pneumoniae co-carrying multiple carbapenemases

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) co-carrying multiple carbapenemases is complicating clinical treatment. This study aimed to investigate the global dissemination trends of CRKP strains that co-carry multiple carbapenemases. The CRKP isolate KP424 co-carrying bla_NDM-1 and bla_KPC-2, recovered from a stool specimen, was identified by the NG-Test Carba 5 test, and the genome sequence was further determined by using Nanopore MinION and Illumina NovaSeq 6000 technologies. The genome sequences of the CRKP strains carrying multiple carbapenemase genes were further retrieved from the NCBI GenBank database. Thirteen antimicrobial resistance genes, including bla_NDM-1 and bla_KPC-2, have been identified in KP424, with bla_NDM-1 and bla_KPC-2 located on different plasmids. In total, 832 genome sequences of CRKP strains co-carrying two carbapenemase genes were retrieved from the NCBI database. Strains carrying both bla_NDM and bla_OXA-48-like accounted for 665 (79.9 %) of the total strains, ranking first, and those carrying both bla_KPC and bla_NDM accounted for 103 (12.4 %), ranking second. The prevalence of CRKP strains co-carrying two carbapenemase genes increased significantly over time, from 0.40 % in 2010 to 9.67 % in 2021. The proportion of strains carrying both bla_KPC and bla_NDM has also increased, from 0.00 % in 2010 to 4.40 % in 2021. The strains carrying both bla_KPC and bla_NDM had the highest prevalence (66.7 %, 52/78) in China, while those carrying both bla_NDM and bla_OXA-48-like had the highest prevalence worldwide. Multiple-carbapenemase producers pose a great threat to public health; further research on the mechanisms underlying multiple carbapenemase gene occurrence is required to prevent their global dissemination.

Evaluation of Aztreonam and Ceftazidime/Avibactam Synergism against Klebsiella pneumoniae by MALDI-TOF MS

INTRODUCTION

Resistance to carbapenems due to the co-production of NDM and ESBL or NDM and KPC is increasing. Therefore, combined therapy with aztreonam (ATM) plus ceftazidime/avibactam (CZA) has been recommended. Then, it is necessary to develop and evaluate fast and simple methods to determine synergism in vitro in microbiology laboratories.

OBJECTIVE

To develop a method to determine the synergism of ATM and CZA by MALDI-TOF MS (SynMALDI).

METHOD

Klebsiella pneumoniae (n = 22) isolates with bla_NDM and/or bla_KPC genes were tested. The time-kill curve assay was performed for four isolates (three positives for bla_NDM and bla_KPC and one positive for bla_NDM only). For SynMALDI, each isolate was incubated for 3 h in 4 tubes containing brain-heart infusion broth with the following: (1) no antibiotic; (2) ATM at 64 mg/L; (3) CZA at 10/4 mg/L; and (4) ATM at 64 mg/L plus CZA at 10/4 mg/L. After incubation, the bacterial protein extract was analyzed by MALDI-TOF MS, and the relative growth (RG) was determined for each isolate, considering intensities of the peaks of the bacterium incubated with antibiotic (tubes 2, 3, and 4) to the same bacterium incubated without antibiotic (tube 1), as follows: RG = Intensity_{With antibiotic}/Intensity_{Without antibiotic}. The combination was determined as synergistic when there was an RG decrease of 0.3 in the antibiotic combination in relation to the RG of the most active antibiotic alone.

RESULTS

The combination of ATM plus CZA proved to be synergic by time-kill curve assay. All isolates tested with the SynMALDI method also presented synergism.

CONCLUSIONS

Detection of synergism for ATM plus CZA combination can be determined by MALDI-TOF MS, providing fast results in order to improve patient treatment.

ESKAPE and Beyond: The Burden of Coinfections in the COVID-19 Pandemic

The ESKAPE group constitute a threat to public health, since these microorganisms are associated with severe infections in hospitals and have a direct relationship with high mortality rates. The presence of these bacteria in hospitals had a direct impact on the incidence of healthcare-associated coinfections in the SARS-CoV-2 pandemic. In recent years, these pathogens have shown resistance to multiple antibiotic families. The presence of high-risk clones within this group of bacteria contributes to the spread of resistance mechanisms worldwide. In the pandemic, these pathogens were implicated in coinfections in severely ill COVID-19 patients. The aim of this review is to describe the main microorganisms of the ESKAPE group involved in coinfections in COVID-19 patients, addressing mainly antimicrobial resistance mechanisms, epidemiology, and high-risk clones.

Characterization of blaKPC-2 and blaNDM-1 Plasmids of a K. pneumoniae ST11 Outbreak Clone

The most common resistance mechanism to carbapenems is the production of carbapenemases. In 2021, the Pan American Health Organization warned of the emergence and increase in new carbapenemase combinations in Enterobacterales in Latin America. In this study, we characterized four Klebsiella pneumoniae isolates harboring bla_KPC and bla_NDM from an outbreak during the COVID-19 pandemic in a Brazilian hospital. We assessed their plasmids' transference ability, fitness effects, and relative copy number in different hosts. The K. pneumoniae BHKPC93 and BHKPC104 strains were selected for whole genome sequencing (WGS) based on their pulsed-field gel electrophoresis profile. The WGS revealed that both isolates belong to ST11, and 20 resistance genes were identified in each isolate, including bla_KPC-2 and bla_NDM-1. The bla_KPC gene was present on a ~56 Kbp IncN plasmid and the bla_NDM-1 gene on a ~102 Kbp IncC plasmid, along with five other resistance genes. Although the bla_NDM plasmid contained genes for conjugational transfer, only the bla_KPC plasmid conjugated to E. coli J53, without apparent fitness effects. The minimum inhibitory concentrations (MICs) of meropenem/imipenem against BHKPC93 and BHKPC104 were 128/64 and 256/128 mg/L, respectively. Although the meropenem and imipenem MICs against E. coli J53 transconjugants carrying the bla_KPC gene were 2 mg/L, this was a substantial increment in the MIC relative to the original J53 strain. The bla_KPC plasmid copy number was higher in K. pneumoniae BHKPC93 and BHKPC104 than in E. coli and higher than that of the bla_NDM plasmids. In conclusion, two ST11 K. pneumoniae isolates that were part of a hospital outbreak co-harbored bla_KPC-2 and bla_NDM-1. The bla_KPC-harboring IncN plasmid has been circulating in this hospital since at least 2015, and its high copy number might have contributed to the conjugative transfer of this particular plasmid to an E. coli host. The observation that the bla_KPC-containing plasmid had a lower copy number in this E. coli strain may explain why this plasmid did not confer phenotypic resistance against meropenem and imipenem.

Investigation of antimicrobial resistance patterns and molecular typing of Pseudomonas aeruginosa isolates among Coronavirus disease-19 patients

BACKGROUND

Pseudomonas aeruginosa is a common co-infecting pathogen recognized among COVID-19 patients. We aimed to investigate the antimicrobial resistance patterns and molecular typing of Pseudomonas aeruginosa isolates among Coronavirus disease-19 patients.

METHODS

Between December 2020 and July 2021, 15 Pseudomonas aeruginosa were isolated from COVID-19 patients in the intensive care unit at Sina Hospital in Hamadan, west of Iran. The antimicrobial resistance of the isolates was determined by disk diffusion and broth microdilution methods. The double-disk synergy method, Modified Hodge test, and polymerase chain reaction were utilized to detect Pseudomonas aeruginosa extended spectrum beta-lactamase and carbapenemase producers. Microtiter plate assay was performed to evaluate the biofilm formation ability of the isolates. The isolates phylogenetic relatedness was revealed using the multilocus variable-number tandem-repeat analysis method.

RESULTS

The results showed Pseudomonas aeruginosa isolates had the most elevated resistance to imipenem (93.3%), trimethoprim-sulfamethoxazole (93.3%), ceftriaxone (80%), ceftazidime (80%), gentamicin (60%), levofloxacin (60%), ciprofloxacin (60%), and cefepime (60%). In the broth microdilution method, 100%, 100%, 20%, and 13.3% of isolates showed resistance to imipenem, meropenem, polymyxin B, and colistin, respectively. Ten (66.6%) isolates were identified as multiple drug resistance. Carbapenemase enzymes and extended spectrum beta-lactamases were identified in 66.6% and 20% of the isolates, respectively and the biofilm formation was detected in 100% of the isolates. The blaOXA-48, blaTEM, blaIMP, blaSPM, blaPER, blaVEB, blaNDM, blaSHV, and blaCTX-M genes were detected in 100%, 86.6%, 86.6%, 40%, 20%, 20%, 13.3%, 6.6%, and 6.6% of the isolates, respectively. The blaVIM, blaGIM, blaGES, and blaMCR-1 genes were not identified in any of the isolates. The MLVA typing technique showed 11 types and seven main clusters and most isolates belong to cluster I, V and VII.

CONCLUSION

Due to the high rate of antimicrobial resistance, as well as the genetic diversity of Pseudomonas aeruginosa isolates from COVID-19 patients, it is indispensable to monitor the antimicrobial resistance pattern and epidemiology of the isolates on a regular basis.

Disc Diffusion and ComASP® Cefiderocol Microdilution Panel to Overcome the Challenge of Cefiderocol Susceptibility Testing in Clinical Laboratory Routine

Cefiderocol susceptibility testing represents a major challenge for clinical microbiology. Although disc diffusion showed robustness to test cefiderocol susceptibility, large areas of technical uncertainty (ATU) are reported by current EUCAST breakpoints. Herein, we evaluated the in vitro activity of cefiderocol on a collection of 286 difficult-to-treat Gram-negative isolates using disc diffusion and ComASP^® cefiderocol microdilution panel. Broth microdilution (BMD) in iron-depleted Mueller-Hinton broth was used as reference method. Following the EUCAST guidelines, disc diffusion allowed to determine cefiderocol susceptibility (susceptible or resistant) in 78.6%, 88.1%, 85.4% and 100% of Enterobacterales, P. aeruginosa, A. baumannii and S. maltophilia isolates tested, respectively. ComASP^® cefiderocol panel showed 94% and 84% of overall categorical agreement and essential agreement. Only one very major error and two major errors were observed, for MIC values nearly close to the resistance breakpoint (2 mg/L). Overall, 20.5% of the carbapenemase-producing Enterobacterales that achieved ATU results by the disc diffusion method tested resistant by both ComASP^® panel and reference BMD. Conversely, all VIM-producing P. aeruginosa showed MIC values in the susceptible range (≤2 mg/L). Lastly, only six out of seven (85.7%) A. baumannii isolates showing inhibition zones <17 mm tested resistant by both ComASP^® panel and the reference BMD suggesting that inhibition zone <17 mm are not unequivocally suggestive of resistance. Our results, although obtained on a limited number of isolates, suggest that the combination of disc diffusion with a ComASP^® cefiderocol microdilution panel could be a viable solution to overcome the challenge of cefiderocol susceptibility testing in routine microbiology laboratories.

Colonization and Healthcare-Associated Infection of Carbapenem-Resistant Enterobacteriaceae, Data from Polish Hospital with High Incidence of Carbapenem-Resistant Enterobacteriaceae, Does Active Target Screening Matter?

The objective of the study was to analyse the incidence of carbapenem-resistant Enterobacteriaceae (CRE) at a provincial hospital from 2019-2021. Multiplex PCR was used to detect the presence of carbapenemase genes. There were 399 cases of CRE detected in total in the analysed period, including 104 healthcare-associated infections. Out of the isolated CRE, 97.7% were Klebsiella pneumoniae with OXA-48 or KPC genes. Overall, among the identified CRE genes, the most frequently present genes were the ones mediating oxacillinase OXA-48 (71%) and KPC (26%), and significantly less often New Delhi NDM metallo-β-lactamase (2.5%). Moreover, two isolates produced two carbapenemases, i.e., OXA-48 and KPC. The conducted research demonstrates that there is a constant need for continuous monitoring of the occurrence of CRE strains and the hospital antibiotic policy, as well as the implementation of procedures to prevent CRE transmission by medical personnel and hospital support staff.

Antibiotics in development for multiresistant gram-negative bacilli

The rapid increase in antibiotic(ATB) resistance among Gram-negative bacilli(BGN), especially in strains of Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii, with high resistance patterns (XDR), poses a huge threat to health systems worldwide. In the last decade, different ATBs have been developed against XDR, some of which combine a lactam β along with a β-lactamase inhibitor, while others use non-β-lactam inhibitors. Most of them have adequate "in vitro" activity on several β-lactamases of class A, C and D of Ambler. However, combinations such as Ceftazidime/avibactam, Ceftolozane/Tazobactam and Meropenem/vaborbactam have no activity against metallo-β-lactamases(MβL). New combinations such as Aztreonan/AVI, Cefepime/Zidebactam, or new cephalosporins such as Cefiderocol, have efficacy against MβL enzymes. Although some of these combinations are already approved and in the commercialization phase, many of them have yet to define their place within the treatment of microorganisms with high resistance through clinical studies.