In vitro activity of the novel siderophore cephalosporin,cefiderocol, in Gram-negative pathogens in Europe by site of infection

ObjectivesWe assessed the activity of the novel siderophore cephalosporin, cefiderocol and selected other antibacterial agents against Gram-negative bacterial isolates in Europe.MethodsIsolates were obtained between 2013 and 2018 from European countries participating in the SIDERO-WT and SIDERO-Proteeae multinational surveillance studies. Isolates were categorised by infection site, focusing on bloodstream infections, hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP), complicated intra-abdominal infections and complicated urinary tract infections. Cefiderocol activity was compared with ceftazidime–avibactam, ceftolozane–tazobactam, colistin and meropenem using standard susceptibility testing methods. European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used to interpret susceptibility data.ResultsIsolates (n = 20 911) were collected from 145 sites in 24 countries in Europe, the highest proportion (34%) being from patients with HABP/VABP. Enterobacterales (66.6% of isolates) were more frequent than glucose non-fermenting species (33.4%) overall, with some differences between infection sites. Across all infection sites, the MIC₅₀/MIC₉₀ for cefiderocol was ≤0.5/≤2 mg/L for Enterobacter spp., ≤0.25/<2 mg/L for Klebsiella spp., 0.12/2 mg/L for Acinetobacter spp., ≤0.25/1 mg/L for Pseudomonas aeruginosa and ≤0.12/≤0.5 mg/L for Stenotrophomonas maltophilia. Across all infection sites, cefiderocol MICs were ≤2 mg/L for ≥96% of Enterobacter spp., ≥95% of Klebsiella spp., ≥90% of Acinetobacter spp. and ≥99% of Pseudomonas aeruginosa and Stenotrophomonas maltophilia isolates. Cefiderocol maintained high activity in carbapenem-resistant isolates, and the difference in activity between carbapenem-resistant (percentage susceptibility at EUCAST breakpoint: E. coli 77.8%, Klebsiella spp. 69.2%, Pseudomonas aeruginosa 97.5%, Acinetobacter spp. 90.7%, Stenotrophomonas maltophilia 99.6%) and carbapenem-susceptible (percentage susceptibility at EUCAST breakpoint: E. coli 99.4%, Klebsiella spp. 98.0%, Pseudomonas aeruginosa 99.7%, Acinetobacter spp. 94.9%) isolates was lower for cefiderocol than other agents.ConclusionsCefiderocol had excellent activity against all Gram-negative species, independent of key infection site and carbapenem MIC. Cefiderocol is a useful addition to the therapeutic options available for these difficult-to-treat infections.     

Influence of Clinical Breakpoint Changes from CLSI 2009 to EUCAST 2011 Antimicrobial Susceptibility Testing Guidelines on Multidrug Resistance Rates of Gram-Negative Rods

Multidrug resistance (MDR) rates of Gram-negative rods were analyzed comparing CLSI 2009 and EUCAST 2011 antibiotic susceptibility testing guidelines. After EUCAST 2011 was applied, the MDR rates increased for Klebsiella pneumoniae (2.2%), Enterobacter cloacae (1.1%), Pseudomonas aeruginosa (0.7%), and Escherichia coli (0.4%). A total of 24% of Enterobacteriaceae MDR isolates and 12% of P. aeruginosa MDR isolates were categorized as MDR due to breakpoint changes.     

What's New from the CLSI Subcommittee on Antimicrobial Susceptibility Testing M100, 29th Edition

The 29th edition of Clinical and Laboratory Standards Institute (CLSI) document M100, Performance Standards for Antimicrobial Susceptibility Testing, was published in January 2019. This edition of the document was corrected in January, February, and May 2019 and revised in March and July 2019. Categorical interpretations were redefined to accommodate the adoption of a susceptible–dose-dependent (SDD) category using off-label drug dosages for Enterococcus faecium treated with daptomycin and methicillin-resistant Staphylococcus aureus (MRSA) treated with ceftaroline. Additional revisions included updated breakpoints for disk diffusion and minimum inhibitory concentrations (MICs) for Enterobacteriaceae treated with meropenem-vaborbactam; investigational intended use of cefiderocol breakpoints for Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter spp., and Stenotrophomonas maltophilia; fluoroquinolone disk diffusion and MIC breakpoints for Enterobacteriaceae and P. aeruginosa; and MIC breakpoints for azithromycin to be used with Neisseria gonorrhoeae. A review of these changes and the rationale supporting the changes are presented here, along with the new and updated recommendations, clarifications, and other less significant changes to the M100 document.     

Validation of EUCAST zone diameter breakpoints against reference broth microdilution

The European Committee on Antimicrobial Susceptibility Testing (EUCAST) began harmonizing clinical breakpoints in Europe 2002. In 2009, work to develop a disc diffusion method began and the first disc diffusion breakpoints calibrated to EUCAST clinical MIC breakpoints were published in December 2009. In this study we validated EUCAST clinical zone diameter breakpoints against the International Standard Organization (ISO) reference broth microdilution. A collection of 544 isolates (238 Gram-negative and 306 Gram-positive) were tested against a panel of antimicrobial agents. Antimicrobial susceptibility testing was performed with broth microdilution as described by ISO and disc diffusion in accordance with EUCAST methodology. Inhibition zone diameters and MIC values were interpreted and categorized (S, I and R) according to EUCAST clinical breakpoint table version 2.0. Categorical agreement (CA) as well as minor (mD), major (MD) and very major (VMD) discrepancies were determined. There was in general good correlation between susceptibility test results obtained with disc diffusion and broth microdilution. Overall CA was 97.3% for all combinations of organisms and antimicrobial agents (<n = 5231) and the overall discrepancy rates were 110 (2.1%) mD, 24 (0.5%) MD and 7 (0.1%) VMD. The overall CA for Gram-positive and Gram-negative organisms were 98.7% (2346 tests) and 96.2% (2942 tests), respectively. Seven VMD were observed, five for Gram-positive organisms (coagulase negative staphylococci (<n = 2) and Staphylococcus aureus (<n = 3)) and two for Gram-negative organisms (<Pseudomonas aeruginosa). Minor discrepancies were mainly observed in Gram-negatives and were related to different antimicrobial agents and species.     

Impact of Revised Cefepime CLSI Breakpoints on Escherichia coli and Klebsiella pneumoniae Susceptibility and Potential Impact If Applied to Pseudomonas aeruginosa

The CLSI reduced the cefepime Enterobacteriaceae susceptibility breakpoint and introduced the susceptible-dose-dependent (S-DD) category. In this study, MICs were determined for a Gram-negative collection to assess the impact of this change. For Enterobacteriaceae, this resulted in <2% reduction in susceptibility, with 1% being S-DD. If applied to Pseudomonas aeruginosa, the % susceptibility (%S) dropped from 77% to 43%, with 34% being S-DD. The new breakpoints did little to the Enterobacteriaceae %S, but for P. aeruginosa, a profound reduction was seen in %S. The recognition of a S-DD response to cefepime should alert clinicians to the possible need for higher doses.     

Multidrug-resistant,extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance

Many different definitions for multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR) bacteria are being used in the medical literature to characterize the different patterns of resistance found in healthcare-associated, antimicrobial-resistant bacteria. A group of international experts came together through a joint initiative by the European Centre for Disease Prevention and Control (ECDC) and the Centers for Disease Control and Prevention (CDC), to create a standardized international terminology with which to describe acquired resistance profiles in Staphylococcus aureus, Enterococcus spp., Enterobacteriaceae (other than Salmonella and Shigella), Pseudomonas aeruginosa and Acinetobacter spp., all bacteria often responsible for healthcare-associated infections and prone to multidrug resistance. Epidemiologically significant antimicrobial categories were constructed for each bacterium. Lists of antimicrobial categories proposed for antimicrobial susceptibility testing were created using documents and breakpoints from the Clinical Laboratory Standards Institute (CLSI), the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the United States Food and Drug Administration (FDA). MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories, XDR was defined as non-susceptibility to at least one agent in all but two or fewer antimicrobial categories (i.e. bacterial isolates remain susceptible to only one or two categories) and PDR was defined as non-susceptibility to all agents in all antimicrobial categories. To ensure correct application of these definitions, bacterial isolates should be tested against all or nearly all of the antimicrobial agents within the antimicrobial categories and selective reporting and suppression of results should be avoided.     

Dosing Strategy Based on Prevailing Aminoglycoside Minimum Inhibitory Concentration in India: Evidence and Issues

Aminoglycosides are important agents used for treating drug-resistant infections. The current dosing regimen of aminoglycosides does not achieve sufficient serum level concentration for the infected bacterial pathogen interpreted as susceptible based on laboratory testing. Minimum inhibitory concentration was determined for nearly 2000 isolates of Enterobacteriaceae and Pseudomonas aeruginosa by broth microdilution method. Results were interpreted based on CLSI and EUCAST interpretative criteria and the inconsistencies in the susceptibility profile were noted. This study provides insights into the inconsistencies existing in the laboratory interpretation and the corresponding clinical success rates. This urges the need for revising clinical breakpoints for amikacin, to resolve under dosing leading to clinical failure.     

3-0-demethyl fortimicin A: In vitro activity and interpretive zone standards for disk diffusion susceptibility tests

The in vitro activity of 3-0-demethyl fortimicin A was compared to that of amikacin and tobramycin against 5,230 clinical isolates in four institutions. Amikacin and tobramycin were more active than 3-0-demethyl fortimicin A againstPseudomonas aeruginosa andAcinetobacter spp., but all three drugs had similar activity against theEnterobacteriaceae andStaphylococcus aureus. Additional tests with 335 representative gram-negative bacilli compared five different aminoglycosides, demonstrating differences with some isolates. Standardized disk diffusion tests were also performed with 30μg 3-0-demethyl fortimicin A disks, according to the National Committee for Clinical Laboratory Standards. The following interpretive breakpoints are proposed: ? 11 mm for resistant (MIC ?32μg/ml) and ? 15 mm for susceptible (MIC ? 16μg/ml).     

Assessment of the Phoenix™ automated system and EUCAST breakpoints for antimicrobial susceptibility testing against isolates expressing clinically relevant resistance mechanisms

EUCAST breakpoint criteria are being adopted by automatic antimicrobial susceptibility testing systems. The accuracy of the Phoenix Automated System in combination with 2012 EUCAST breakpoints against recent clinical isolates was evaluated. A total of 697 isolates (349 Enterobacteriaceae, 113 Pseudomonas spp., 25 Acinetobacter baumannii, 11 Stenotrophomonas maltophilia, 95 Staphylococcus aureus, 6 coagulase negative staphylococci, 77 enterococci and 21 Streptococcus pneumoniae) with defined resistance phenotypes and well-characterized resistance mechanisms recovered in Spain (n = 343) and Italy (n = 354) were tested. Comparator antimicrobial susceptibility testing data were obtained following CLSI guidelines. Experimental agreement (EA), defined as MIC agreement ±1 log₂ dilution, category agreement (CA) and relative discrepancies (minor (mD), major (MD) and very major discrepancies (VMD)) were determined. The overall EA and CA for all organism-antimicrobial agent combinations (n = 6.294) were 97.3% and 95.2%, respectively. mD, MD and VMD were 4.7%, 1.3% and 2.7%, all of them in agreement with the ISO (ISO20776–2:2007) acceptance criteria for assessment of susceptibility testing devices. VMD were mainly observed in amoxicillin-clavulanate and cefuroxime in Enterobacteriaceae and gentamicin in Pseudomonas aeruginosa, whereas MD were mainly observed in amoxicillin-clavulante in Enterobacteriaceae. mD were mainly observed in Enterobacteriaceae but distributed in different antimicrobials. For S. aureus and enterococci relative discrepancies were low. The Phoenix system showed accuracy assessment in accordance with the ISO standards when using EUCAST breakpoints. Inclusion of EUCAST criteria in automatic antimicrobial susceptibility testing systems will facilitate the implementation of EUCAST breakpoints in clinical microbiology laboratories.     

Comparative In Vitro Potency of Gemifloxacin and Fluoroquinolones Against Recent European Clinical Isolates from a Global Surveillance Study

Gemifloxacin, a new fluoroquinolone with enhanced activity against gram-positive aerobes, was compared to ciprofloxacin, levofloxacin and ofloxacin against 21,464 recent isolates from 16 European countries. Gemifloxacin was the most potent fluoroquinolone against streptococci including penicillin-, macrolide- and ciprofloxacin-resistant Streptococcus pneumoniae, Staphylococcus aureus, coagulase-negative staphylococci, Acinetobacter spp., Haemophilus spp. and Moraxella catarrhalis. This drug was more potent than or comparable to ciprofloxacin against members of the family Enterobacteriaceae, Burkholderia cepacia, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. Gemifloxacin is a promising fluoroquinolone with potent in vitro activity. Electronic Publication     

In vitro activities of doripenem and other carbapenems against clinically important bacteria isolated in intensive care units: nationwide data from the SMART Programme

This nationwide surveillance of clinically important bacteria from the intensive care units (ICUs) of major teaching hospitals throughout Taiwan investigated the susceptibilities to doripenem and other comparator carbapenems from September through November 2005. Minimum inhibitory concentrations (MICs) were determined for 1,311 clinical isolates using the broth microdilution method according to Clinical and Laboratory Standards Institute (CLSI) 2005 guidelines. Doripenem showed similar (within four-fold difference of MICs) in vitro activity to meropenem for Enterobacteriaceae and probably comparable activity to meropenem against important nosocomial non-fermentative Gram-negative bacilli (NFGNBs), including Pseudomonas aeruginosa, Acinetobacter baumannii and Burkholderia cepacia. Among the four carbapenems analysed, doripenem and meropenem exhibited better in vitro activity than imipenem or ertapenem against extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae and Escherichia coli isolates. However, the meropenem MIC₉₀ against ESBL-producing K. pneumoniae isolates was 2 µg/ml. Besides, doripenem with the MIC₉₀ of 0.5 µg/ml to Streptococcus pneumoniae possibly suggested its potential therapeutic effect regarding community-acquired pneumonia. Because of the heavy resistance burden in Taiwan, closely monitoring the evolutionary trend of carbapenem susceptibilities against clinically important pathogens is crucial in the future.     

Comparative activity of the new fluoroquinolone rufloxacin (MF 934) against clinical isolates of gram-negative and gram-positive bacteria

The antibacterial activity of the new fluoroquinolone rufloxacin (MF 934) was evaluated against 1095 clinical isolates and compared with that of other quinolones and various commonly used antibiotics. Rufloxacin was highly effective against members of theEnterobacteriaceae, inhibiting 98 % of the isolates at a concentration of 1 mg/l. Ninety-two percent ofAeromonas hydrophila and 65 %Acinetobacter strains tested were inhibited by 1 mg/l of rufloxacin, whereas 98 % of methicillin-susceptible and 87 % of methicillin-resistantStaphylococcus aureus strains and 76 % of coagulase-negative staphylococci strains required 4 mg/l for growth inhibition. The MIC values of rufloxacin for most bacteria were 4–16 times higher than those of ciprofloxacin and norfloxacin. Rufloxacin had little activity against xanthomonads, pseudomonads and enterococci. Approximately 95–96 % of isolates ofPseudomonas aeruginosa were inhibited by 2 mg/l of ciprofloxacin and norfloxacin as compared to 29 % inhibited by rufloxacin at this concentration.     

Transplantation-Associated Long-Term Immunosuppression Promotes Oral Colonization by Potentially Opportunistic Pathogens without Impacting Other Members of the Salivary Bacteriome

Solid-organ transplant recipients rely on pharmacological immunosuppression to prevent allograft rejection. The effect of such chronic immunosuppression on the microflora at mucosal surfaces is not known. We evaluated the salivary bacterial microbiome of 20 transplant recipients and 19 nonimmunosuppressed controls via 454 pyrosequencing of 16S rRNA gene amplicons. Alpha-diversity and global community structure did not differ between transplant and control subjects. However, principal coordinate analysis showed differences in community membership. Taxa more prevalent in transplant subjects included operational taxonomic units (OTUs) of potentially opportunistic Gammaproteobacteria such as Klebsiella pneumoniae, Pseudomonas fluorescens, Acinetobacter species, Vibrio species, Enterobacteriaceae species, and the genera Acinetobacter and Klebsiella. Transplant subjects also had increased proportions of Pseudomonas aeruginosa, Acinetobacter species, Enterobacteriaceae species, and Enterococcus faecalis, among other OTUs, while genera with increased proportions included Klebsiella, Acinetobacter, Staphylococcus, and Enterococcus. Furthermore, in transplant subjects, the dose of the immunosuppressant prednisone positively correlated with bacterial richness, while prednisone and mycophenolate mofetil doses positively correlated with the prevalence and proportions of transplant-associated taxa. Correlation network analysis of OTU relative abundance revealed a cluster containing potentially opportunistic pathogens as transplant associated. This cluster positively correlated with serum levels of C-reactive protein, suggesting a link between the resident flora at mucosal compartments and systemic inflammation. Network connectivity analysis revealed opportunistic pathogens as highly connected to each other and to common oral commensals, pointing to bacterial interactions that may influence colonization. This work demonstrates that immunosuppression aimed at limiting T-cell-mediated responses creates a more permissive oral environment for potentially opportunistic pathogens without affecting other members of the salivary bacteriome.     

Development of EUCAST zone diameter breakpoints and quality control criteria for ceftazidime-avibactam 10-4 μg

Ceftazidime-avibactam disk studies were performed for disk mass selection and for establishing EUCAST quality control ranges and zone diameter breakpoints. The disk mass study included disk diffusion testing with ceftazidime-avibactam 10-4 and 10-6 μg disks and broth microdilution MIC testing for challenge set of 94 Enterobacteriaceae and 45 Pseudomonas aeruginosa. EUCAST SOP 9.0-based QC and MIC-disk correlations studies were followed for development of ceftazidime-avibactam 10-4 μg ranges for Escherichia coli ATCC 25922, P. aeruginosa ATCC 27583, and Klebsiella pneumoniae ATCC 700603 and for zone diameter breakpoint determination. The ceftazidime-avibactam 10-4 and 10-6 μg disks performed similar in comparison to broth microdilution, with zones ≤?14 mm for all resistant strains. The 10-4 μg disk was selected and used in QC and breakpoint studies. There was minimal variation of ceftazidime-avibactam 10-4 μg QC study results between disks, media, and sites. The QC ranges were within 7 mm for all strains. The zone diameter breakpoint study demonstrated good correlation of MIC and disk results. The established zone diameter breakpoints resulted in false susceptible rates of 1.6 and 4.0% for Enterobacteriaceae and P. aeruginosa. EUCAST selected the ceftazidime-avibactam 10-4 μg disk and established QC ranges for E. coli 25922 of 24–30 mm, P. aeruginosa ATCC 27853 of 21–27 mm, and K. pneumoniae ATCC 700603 of 18–24 mm. The zone diameter breakpoints that correlated best with the MIC breakpoints of susceptible ≤?8 mg/L and resistant >?8 mg/L were Enterobacteriaceae (S?≥?13, R?<?13 mm) and P. aeruginosa (S?≥?17, R?<?17 mm).     

Antibody Responses to Acinetobacter spp. and Pseudomonas aeruginosa in Multiple Sclerosis: Prospects for Diagnosis Using the Myelin-Acinetobacter-Neurofilament Antibody Index

Antibody responses to Acinetobacter (five strains), Pseudomonas aeruginosa, Escherichia coli, myelin basic protein (MBP), and neurofilaments were measured in sera from 26 multiple sclerosis (MS) patients, 20 patients with cerebrovascular accidents (CVA), 10 patients with viral encephalitis, and 25 healthy blood donors. In MS patients, elevated levels of antibodies against all strains of Acinetobacter tested were present, as well as antibodies against P. aeruginosa, MBP, and neurofilaments, but not antibodies to E. coli, compared to the CVA group and controls. The myelin-Acinetobacter-neurofilament antibody index appears to distinguish MS patients from patients with CVAs or healthy controls. The relevance of such antibodies to the neuropathology of MS requires further evaluation.     

Comparison of disk diffusion,Etest and VITEK2 for detection of carbapenemase‐producing Klebsiella pneumoniae with the EUCAST and CLSI breakpoint systems

The aim of this study was to compare CLSI and EUCAST MIC and disk diffusion carbapenem breakpoints for the detection of carbapenemase‐producing Klebsiella pneumoniae. K. pneumoniae strains with known KPC (n = 31) or VIM (n = 20) carbapenemases were characterized by disk diffusion (Oxoid) and Etest (bioMérieux) vs. imipenem, meropenem and ertapenem, and with VITEK2 (bioMérieux, five different cards). Extended‐spectrum β‐lactamase (ESBL) testing was performed with VITEK2 (bioMérieux), ESBL combination disks (Becton Dickinson) and the ESBL Etest (bioMérieux). With CLSI and EUCAST MIC breakpoints, respectively, 11 and seven of the strains were susceptible to imipenem, 12 and eight to meropenem, and seven and none to ertapenem. The EUCAST epidemiological cut‐off (ECOFF) values for meropenem and ertapenem identified all carbapenemase producers, whereas the imipenem ECOFF failed in five strains. All carbapenemase producers were detected with EUCAST disk diffusion breakpoints for ertapenem and meropenem, and four strains were susceptible to imipenem. CLSI disk diffusion breakpoints characterized 18 (imipenem), 14 (meropenem) and three (ertapenem) isolates as susceptible. When cards with a single carbapenem were used, detection failures with VITEK2 were four for imipenem, none for meropenem and one for ertapenem. Cards containing all three carbapenems had one to two failures. With ESBL combination disks, 21/31 KPC producers and 2/20 VIM producers were positive. With VITEK2, no VIM producers and between none and seven KPC producers were ESBL‐positive. All carbapenemase producers were detected with the meropenem MIC ECOFF, or the clinical EUCAST breakpoint for ertapenem. EUCAST disk diffusion breakpoints for meropenem and ertapenem detected all carbapenemase producers. VITEK2 had between none and four failures in detecting carbapenemase producers, depending on the antibiotic card.     

Multicentre testing of the EUCAST broth microdilution reference method for MIC determination on Mycobacterium tuberculosis

ObjectivesThe first objective of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) subcommittee for antimycobacterial susceptibility testing (AMST), launched in 2016, was to set a reference method for determining the MICs of antituberculous agents, since many protocols are used worldwide and a consensus one is needed for the determination of microbiological breakpoints.MethodsDuring 2017 and 2018, MIC determination protocols were evaluated prospectively in a multicentre study within the four AMST laboratories. MIC results were obtained for isoniazid, levofloxacin and amikacin on the reference strain Mycobacterium tuberculosis H37Rv ATCC 27294. Broth microdilution (BMD) in Middlebrook 7H9 and solid medium dilution (SMD) in Middlebrook 7H10 were performed using two inoculum concentrations. MICs were interpreted with regard to visual and 99% inhibition after 7, 14 or 21 days of incubation for BMD and 21 days for SMD.ResultsFollowing the EUCAST reference protocol, intra- and inter-assay agreements were within ±1 MIC dilution for >95% of the observations for the three drugs in both methods. MIC values, presented as MIC mode (range) for BMD and SMD respectively, were: 0.03 (0.015–0.06) mg/L and 0.12 (0.06–0.25) mg/L for isoniazid, 0.25 mg/L (0.25–0.5) and 0.5 mg/L (0.12–0.5) for levofloxacin, and 0.5 mg/L (0.5–1.0) and 0.5 mg/L (0.5–1.0) for amikacin.ConclusionsBoth SMD and BMD were reproducible and eligible as a reference method for MIC determination of the Mycobacterium tuberculosis complex (MTBC). BMD was finally selected as the EUCAST reference method. From now on it will be used to set epidemiological cut-off values and clinical breakpoints of new and old antituberculous agents.     

ESCMID-EUCIC clinical guidelines on decolonization of multidrug-resistant Gram-negative bacteria carriers

ScopeThe aim of these guidelines is to provide recommendations for decolonizing regimens targeting multidrug-resistant Gram-negative bacteria (MDR-GNB) carriers in all settings.MethodsThese evidence-based guidelines were produced after a systematic review of published studies on decolonization interventions targeting the following MDR-GNB: third-generation cephalosporin-resistant Enterobacteriaceae (3GCephRE), carbapenem-resistant Enterobacteriaceae (CRE), aminoglycoside-resistant Enterobacteriaceae (AGRE), fluoroquinolone-resistant Enterobacteriaceae (FQRE), extremely drug-resistant Pseudomonas aeruginosa (XDRPA), carbapenem-resistant Acinetobacter baumannii (CRAB), cotrimoxazole-resistant Stenotrophomonas maltophilia (CRSM), colistin-resistant Gram-negative organisms (CoRGNB), and pan-drug-resistant Gram-negative organisms (PDRGNB). The recommendations are grouped by MDR-GNB species. Faecal microbiota transplantation has been discussed separately. Four types of outcomes were evaluated for each target MDR-GNB:(a) microbiological outcomes (carriage and eradication rates) at treatment end and at specific post-treatment time-points; (b) clinical outcomes (attributable and all-cause mortality and infection incidence) at the same time-points and length of hospital stay; (c) epidemiological outcomes (acquisition incidence, transmission and outbreaks); and (d) adverse events of decolonization (including resistance development). The level of evidence for and strength of each recommendation were defined according to the GRADE approach. Consensus of a multidisciplinary expert panel was reached through a nominal-group technique for the final list of recommendations.RecommendationsThe panel does not recommend routine decolonization of 3GCephRE and CRE carriers. Evidence is currently insufficient to provide recommendations for or against any intervention in patients colonized with AGRE, CoRGNB, CRAB, CRSM, FQRE, PDRGNB and XDRPA. On the basis of the limited evidence of increased risk of CRE infections in immunocompromised carriers, the panel suggests designing high-quality prospective clinical studies to assess the risk of CRE infections in immunocompromised patients. These trials should include monitoring of development of resistance to decolonizing agents during treatment using stool cultures and antimicrobial susceptibility results according to the EUCAST clinical breakpoints.     

Activity of doripenem against extended-spectrum β-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa isolates

The in vitro activity of doripenem was evaluated against a recent collection of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and Pseudomonas aeruginosa isolates (201 ESBL-producing Enterobacteriaceae [153 Escherichia coli and 48 Klebsiella pneumoniae] and 201 P. aeruginosa). Comparator agents included amikacin, tobramycin, ciprofloxacin, cefepime, cefotaxime, ceftazidime piperacillin-tazobactam, imipenem, and meropenem. Both doripenem and meropenem inhibited 100% of the ESBL-producing Enterobacteriaceae at ≤0.5 μg/mL. For these isolates, the MIC₉₀ of doripenem (0.12 μg/mL) was 4-fold lower than that of imipenem (0.5 μg/mL). Against P. aeruginosa, the MIC₉₀ of doripenem and meropenem was 2 μg/mL, 4-fold lower than that of imipenem (8 μg/mL). At an MIC of ≤2 μg/mL, doripenem, meropenem, and imipenem inhibited 90.5%, 89.6%, and 82.1% of P. aeruginosa isolates, respectively. Doripenem maintained activity against imipenem-nonsusceptible isolates of P. aeruginosa; at an MIC of ≤4 μg/mL, it inhibited 15 of the 25 isolates with MICs for imipenem of >4 μg/mL. Doripenem is active against ESBL-producing Enterobacteriaceae and P. aeruginosa isolates. Its activity is similar to that of meropenem and slightly better than that of imipenem. The results of this study suggest that doripenem could be an alternative therapeutic agent for infections caused by these organisms.     

Evaluation of Carbapenemase Screening and Confirmation Tests with Enterobacteriaceae and Development of a Practical Diagnostic Algorithm

Reliable identification of carbapenemase-producing members of the family Enterobacteriaceae is necessary to limit their spread. This study aimed to develop a diagnostic flow chart using phenotypic screening and confirmation tests that is suitable for implementation in different types of clinical laboratories. A total of 334 clinical Enterobacteriaceae isolates genetically characterized with respect to carbapenemase, extended-spectrum β-lactamase (ESBL), and AmpC genes were analyzed. A total of 142/334 isolates (42.2%) were suspected of carbapenemase production, i.e., intermediate or resistant to ertapenem (ETP) and/or meropenem (MEM) and/or imipenem (IPM) according to EUCAST clinical breakpoints (CBPs). A group of 193/334 isolates (57.8%) showing susceptibility to ETP, MEM, and IPM was considered the negative-control group in this study. CLSI and EUCAST carbapenem CBPs and the new EUCAST MEM screening cutoff were evaluated as screening parameters. ETP, MEM, and IPM with or without aminophenylboronic acid (APBA) or EDTA combined-disk tests (CDTs) and the Carba NP-II test were evaluated as confirmation assays. EUCAST temocillin cutoffs were evaluated for OXA-48 detection. The EUCAST MEM screening cutoff (<25 mm) showed a sensitivity of 100%. The ETP APBA CDT on Mueller-Hinton agar containing cloxacillin (MH-CLX) displayed 100% sensitivity and specificity for class A carbapenemase confirmation. ETP and MEM EDTA CDTs showed 100% sensitivity and specificity for class B carbapenemases. Temocillin zone diameters/MIC testing on MH-CLX was highly specific for OXA-48 producers. The overall sensitivity, specificity, positive predictive value, and negative predictive value of the Carba NP-II test were 78.9, 100, 100, and 98.7%, respectively. Combining the EUCAST MEM carbapenemase screening cutoff (<25 mm), ETP (or MEM), APBA, and EDTA CDTs, and temocillin disk diffusion on MH-CLX promises excellent performance for carbapenemase detection.