Evaluation of standardized automated rapid antimicrobial susceptibility testing of Enterobacterales-containing blood cultures: a proof-of-principle study.

Background: Rapid antimicrobial susceptibility testing (RAST) of bacteria causing bloodstream infections is critical for implementation of appropriate antibiotic regimens.

Objectives: We have established a procedure to prepare standardized bacterial inocula for Enterobacterales-containing clinical blood cultures and assessed antimicrobial susceptibility testing (AST) data generated with the WASPLabTM automated reading system.

Methods: A total of 258 blood cultures containing Enterobacterales were examined.

Co-occurrence of aminoglycoside and β-lactam resistance mechanisms in aminoglycoside- non-susceptible Escherichia coli isolated in the Zurich area, Switzerland.

The co-occurrence of aminoglycoside and β-lactam resistance was assessed in 3358 consecutive Escherichia coli clinical isolates collected in 2014 in the greater Zurich area, Switzerland. Non-susceptibility to at least one of the tested aminoglycosides was observed in 470/3358 E. coli strains (14%).

Reducing antibiotic prescribing and addressing the global problem of antibiotic resistance by targeted hygiene in the home and everyday life settings: A position paper.

Antimicrobial resistance (AMR) continues to threaten global health. Although global and national AMR action plans are in place, infection prevention and control is primarily discussed in the context of health care facilities with home and everyday life settings barely addressed. As seen with the recent global SARS-CoV-2 pandemic, everyday hygiene measures can play an important role in containing the threat from infectious microorganisms.

Tentative breakpoints and areas of technical uncertainty for early reading automated disc diffusion for Enterobacterales.

Background: Disc diffusion is a reliable, accurate and cost-efficient procedure for antimicrobial susceptibility testing (AST) but requires long (18-24 h) incubation times. Reading of disc diffusion after short incubation times (6-8 h) by automated systems is feasible but should be categorized with time-adapted breakpoints to reduce errors.

Objectives: This study systematically compared early readings (6 and 8 h) of disc diffusion using an automated system with that of the standard 18 h EUCAST method.

Antibiotic resistance: turning evolutionary principles into clinical reality.

Antibiotic resistance is one of the major challenges facing modern medicine worldwide. The past few decades have witnessed rapid progress in our understanding of the multiple factors that affect the emergence and spread of antibiotic resistance at the population level and the level of the individual patient. However, the process of translating this progress into health policy and clinical practice has been slow.

Structural characterization of aminoglycoside 4'-O-adenylyltransferase ANT(4')-IIb from Pseudomonas aeruginosa.

Aminoglycosides were one of the first classes of broad-spectrum antibacterial drugs clinically used to effectively combat infections. The rise of resistance to these drugs, mediated by enzymatic modification, has since compromised their utility as a treatment option, prompting intensive research into the molecular function of resistance enzymes. Here, we report the crystal structure of aminoglycoside nucleotidyltransferase ANT(4')-IIb in apo and tobramycin-bound forms at a resolution of 1.

Population-based inference of aminoglycoside resistance mechanisms in Escherichia coli.

Background: Interpretative reading of antimicrobial susceptibility test (AST) results allows inferring biochemical resistance mechanisms from resistance phenotypes. For aminoglycosides, however, correlations between resistance pathways inferred on the basis of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) clinical breakpoints and expert rules versus genotypes are generally poor. This study aimed at developing and validating a decision tree based on resistance phenotypes determined by disc diffusion and based on epidemiological cut-offs (ECOFFs) to infer the corresponding resistance mechanisms in Escherichia coli.

Deciphering Multifactorial Resistance Phenotypes in by Genomics and Targeted Label-free Proteomics.

Resistance to β-lactams in involves various mechanisms. To decipher them, whole genome sequencing (WGS) and real-time quantitative polymerase chain reaction (RT-qPCR) were complemented by mass spectrometry (MS) in selected reaction monitoring mode (SRM) in 39 clinical isolates. The targeted label-free proteomic approach enabled, in one hour and using a single method, the quantitative detection of 16 proteins associated with antibiotic resistance: eight acquired β-lactamases ( GES, NDM-1, OXA-23, OXA-24, OXA-58, PER, TEM-1, and VEB), two resident β-lactamases ( ADC and OXA-51-like) and six components of the two major efflux systems ( AdeABC and AdeIJK).

New aminoglycoside-modifying enzymes APH(3')-VIII and APH(3')-IX in Acinetobacter rudis and Acinetobacter gerneri.

Analysis of whole-genome sequences of 133 strains of Acinetobacter detected two genes for new types of aminoglycoside 3'-O-phosphotransferase [APH(3')], type VIII in Acinetobacter rudis and IX in A. gerneri. The enzymes were related to each other (49% identity) and to APH(3')-VI (61% and 51% identity, respectively), which is intrinsic to A.

First Detection of GES-5 Carbapenemase-Producing Acinetobacter baumannii Isolate.

This study was conducted to investigate the molecular epidemiology of resistance in Acinetobacter baumannii isolates collected at a hospital in Riyadh, Saudi Arabia, from January through December 2010. Twenty-seven A. baumannii were highly resistant (MIC > 256 μg/ml) to ceftazidime, cefepime, and aztreonam.

Structural and Biochemical Characterization of Acinetobacter spp. Aminoglycoside Acetyltransferases Highlights Functional and Evolutionary Variation among Antibiotic Resistance Enzymes.

Modification of aminoglycosides by N-acetyltransferases (AACs) is one of the major mechanisms of resistance to these antibiotics in human bacterial pathogens. More than 50 enzymes belonging to the AAC(6') subfamily have been identified in Gram-negative and Gram-positive clinical isolates. Our understanding of the molecular function and evolutionary origin of these resistance enzymes remains incomplete.

Diversity of Molecular Mechanisms Conferring Carbapenem Resistance to Pseudomonas aeruginosa Isolates from Saudi Arabia.

Background. This study described various molecular and epidemiological characters determining antibiotic resistance patterns in Pseudomonas aeruginosa isolates. Methods.

Contribution of the Ade Resistance-Nodulation-Cell Division-Type Efflux Pumps to Fitness and Pathogenesis of Acinetobacter baumannii.

Unlabelled: Overexpression of chromosomal resistance-nodulation-cell division (RND)-type efflux systems with broad substrate specificity contributes to multidrug resistance (MDR) in Acinetobacter baumannii We have shown that modulation of expression of the structural genes for the efflux systems AdeABC and AdeIJK confers MDR and results in numerous alterations of membrane-associated cellular functions, in particular biofilm formation. However, the contribution of these RND pumps to cell fitness and virulence has not yet been studied. The biological cost of an antibiotic resistance mechanism is a key parameter in determining its stability and dissemination.

Origin in Acinetobacter gyllenbergii and dissemination of aminoglycoside-modifying enzyme AAC(6')-Ih.

Objectives: The aac(6')-Ih gene encoding aminoglycoside 6'-N-acetyltransferase type I subtype h [AAC(6')-Ih] is plasmid-borne in Acinetobacter baumannii where it confers high-level amikacin resistance, but its origin remains unknown. We searched for the gene in the genomes of a collection of 133 Acinetobacter spp. and studied its species specificity, expression and dissemination.

Structural and Functional Adaptation of Vancomycin Resistance VanT Serine Racemases.

Unlabelled: Vancomycin resistance in Gram-positive bacteria results from the replacement of the D-alanyl-D-alanine target of peptidoglycan precursors with D-alanyl-D-lactate or D-alanyl-D-serine (D-Ala-D-Ser), to which vancomycin has low binding affinity. VanT is one of the proteins required for the production of D-Ala-D-Ser-terminating precursors by converting L-Ser to D-Ser. VanT is composed of two domains, an N-terminal membrane-bound domain, likely involved in L-Ser uptake, and a C-terminal cytoplasmic catalytic domain which is related to bacterial alanine racemases.

AAC(3)-XI, a new aminoglycoside 3-N-acetyltransferase from Corynebacterium striatum.

Corynebacterium striatum BM4687 was resistant to gentamicin and tobramycin but susceptible to kanamycin A and amikacin, a phenotype distinct among Gram-positive bacteria. Analysis of the entire genome of this strain did not detect any genes for known aminoglycoside resistance enzymes. Yet, annotation of the coding sequences identified 12 putative acetyltransferases or GCN5-related N-acetyltransferases.

Structural and functional plasticity of antibiotic resistance nucleotidylyltransferases revealed by molecular characterization of lincosamide nucleotidylyltransferases lnu(A) and lnu(D).

One of the main mechanisms of resistance to lincosamide and aminoglycoside antibiotics is their inactivation by O-nucleotidylyltransferases (NTases). Significant sequence variation of lincomycin nucleotidylyltransferase (Lnu) and aminoglycoside nucleotidylyltransferase (ANT) enzymes plus lack of detailed information about the molecular basis for specificity of these enzymes toward chemically distinct antibiotic scaffolds hinders development of a general strategy to curb this resistance mechanism. We conducted an extensive sequence analysis identifying 129 putative antibiotic NTases constituting six distinct subfamilies represented by Lnu(A), Lnu(B), Lnu(C), Lnu(D), Lnu(F)/(G) plus ANT(2") enzymes.

Competition between VanU(G) repressor and VanR(G) activator leads to rheostatic control of vanG vancomycin resistance operon expression.

Enterococcus faecalis BM4518 is resistant to vancomycin by synthesis of peptidoglycan precursors ending in D-alanyl-D-serine. In the chromosomal vanG locus, transcription of the resistance genes from the PYG resistance promoter is inducible and, upstream from these genes, there is an unusual three-component regulatory system encoded by the vanURS(G) operon from the P(UG) regulatory promoter. In contrast to the other van operons in enterococci, the vanG operon possesses the additional vanU(G) gene which encodes a transcriptional regulator whose role remains unknown.

Contribution of resistance-nodulation-cell division efflux systems to antibiotic resistance and biofilm formation in Acinetobacter baumannii.

Unlabelled: Acinetobacter baumannii is a nosocomial pathogen of increasing importance due to its multiple resistance to antibiotics and ability to survive in the hospital environment linked to its capacity to form biofilms. To fully characterize the contribution of AdeABC, AdeFGH, and AdeIJK resistance-nodulation-cell division (RND)-type efflux systems to acquired and intrinsic resistance, we constructed, from an entirely sequenced susceptible A. baumannii strain, a set of isogenic mutants overexpressing each system following introduction of a point mutation in their cognate regulator or a deletion for the pump by allelic replacement.

A vanG-type locus in Clostridium argentinense.

Objectives: The objective was to study a new vanG-type locus in Clostridium argentinense vanGCar and to determine its impact on glycopeptide susceptibility of the host.

Methods: The whole genome of C. argentinense NCIB 10714 was sequenced using Illumina single-reads sequencing technology.

Antimicrobial Activity of Plectasin NZ2114 in Combination with Cell Wall Targeting Antibiotics Against VanA-Type Enterococcus faecalis.

Antimicrobial peptide plectasin targeting bacterial cell wall precursor Lipid II has been reported to be active against benzylpenicillin-resistant Streptococcus pneumoniae but less potent against vancomycin-resistant enterococci than their susceptible counterparts. The aim of this work was to test plectasin NZ2114 in combination with cell wall targeting antibiotics on vancomycin-resistant Enterococcus faecalis. The activity of antibiotic combinations was evaluated against VanA-type vancomycin-resistant E.

The Resistant-Population Cutoff (RCOFF): a New Concept for Improved Characterization of Antimicrobial Susceptibility Patterns of Non-Wild-Type Bacterial Populations.

This study aimed to determine resistant-population cutoffs (RCOFFs) to allow for improved characterization of antimicrobial susceptibility patterns in bacterial populations. RCOFFs can complement epidemiological cutoff (ECOFF)-based settings of clinical breakpoints (CBPs) by systematically describing the correlation between non-wild-type and wild-type populations. We illustrate this concept by describing three paradigmatic examples of wild-type and non-wild-type Escherichia coli populations from our clinical strain database of disk diffusion diameters.

The clinical positioning of telavancin in Europe.

Telavancin was the first marketed lipoglycopeptide. Although licensed in Europe in 2011 for the treatment of nosocomial pneumonia caused by meticillin-resistant Staphylococcus aureus (MRSA), it did not become clinically available until March 2014. Given the limited clinical experience with telavancin in Europe, this review provides an overview of its antimicrobial and clinical activity as well as its position among today's antimicrobials, with particular focus on the implications of its licensing requirements.

Molecular epidemiology of carbapenem non-susceptible Acinetobacter baumannii in France.

Carbapenem-resistant Acinetobacter baumannii have emerged globally. The objective of this study was to investigate the epidemiology, clonal diversity and resistance mechanisms of imipenem non-susceptible A. baumannii isolates in France.