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This study was set up to assess the performance of the Reveal® rapid AST system to determine the drug susceptibility of Pseudomonas aeruginosa strains directly from blood cultures. Two hundred fully sequenced clinical P. aeruginosa strains were selected for the evaluation, of which 26.5% (n = 53) produced transferable β-lactamases, and 2.0 to 33.0% had susceptibility levels close to the EUCAST 2021 breakpoints of 11 commonly used antipseudomonal antibiotics. The Reveal® AST system was run with a commercial MIC microplate designed for fast-growing Gram-negative bacilli (Microscan Neg MDR MIC 1), and was compared to the manually operated GN6F MIC microdilution panel from Thermo Fisher, as a comparator method. The Reveal® AST system provided MIC results for the 11 antipseudomonal antibiotics tested within a mean time to result of 6 h 22 min. By comparison with the GN6F panel, the overall rates of categorical agreement (CA), very major errors (VME), major errors (ME), and minor errors (mE for meropenem only) were 96.1%, 1.6%, 4.2%, and 0.6%, respectively. The Specific Reveal® AST system appears to be a reliable and fast technology to determine the susceptibility of P. aeruginosa to antibiotics, including those with resistance levels near categorical breakpoints, directly from blood cultures. [ABSTRACT FROM AUTHOR]

The aim of this study was to describe the molecular epidemiology and the mechanisms of resistance to β-lactams of emerging extensive-drug-resistant Pseudomonas aeruginosa (XDRPA) in a tertiary-care university hospital over a three-year period. Analysis included antimicrobial susceptibility profiling and pulsed-field gel electrophoresis (PFGE). Resistance mechanisms to β-lactams were identified: production of naturally occurring and acquired β-lactamases, overproduction of MexAB-OprM and MexXY efflux systems and loss of porin OprD were assessed. Eighteen patients were colonised or infected with XDRPA which remained susceptible to colistin and, to a lesser extent, to rifampicin. β-lactam resistance was, in most cases, due to the overproduction of AmpC, overproduction of the MexXY efflux system and loss of porin OprD. One isolate produced the class D extended-spectrum oxacillinase (OXA-ESBL) Oxa-28, but none produced metallo-β-lactamase (MBL) or class A extended-spectrum β-lactamase (ESBL). The XDRPA clustered in eight PFGE patterns and both the acquisition and loss of resistance determinants was observed within a single clone during its spread. The emergence of XDRPA isolates in our university hospital has been characterised by genotypic heterogeneity, variation of mechanisms of resistance to β-lactams in a single clone and the predominance of chromosomally encoded resistance mechanisms [ABSTRACT FROM AUTHOR]

Multidrug efflux systems endow on bacterial cells the ability to limit the access of antimicrobial agents to their targets. By actively pumping out antibiotic molecules, these systems prevent the intracellular accumulation necessary for antibiotics to exert their lethal activity. Drug efflux appears to be one of the most widespread antibiotic resistance mechanisms among microorganisms, since it has been demonstrated to occur in many Gram-positive and Gram-negative bacteria including medically important species like staphylococci, streptococci, enterobacteria and opportunistic pathogens like Pseudomonas aeruginosa. Efflux pumps can be specific for only one substrate or accommodate a more or less wide range of noxious products. Export of structurally unrelated compounds confers a multidrug-resistance phenotype on bacterial cells. Therapeutically critical levels of resistance can be achieved by overexpression of efflux systems, especially in those species such as P. aeruginosa which possess a low outer membrane permeability. It is suspected that the dual physiological function of active efflux systems is both the secretion of intracellular metabolites and the protection against a variety of harmful substances that the microorganism may encounter in its natural environment. [ABSTRACT FROM AUTHOR]

The article focuses on the characterization of methicillin-resistant staphylococcus aureus with reduced susceptibility to teicoplanin in eastern France. Vancomycin and teicoplanin are very important agents for the treatment of infections caused by multidrug-resistant gram-positive bacteria. However, since 1997, numerous authors worldwide have reported the emergence of methicillin-resistant Staphylococcus aureus with reduced susceptibility to glycopeptides. The recent description of two fully vancomycin-resistant strains has underscored the threat caused by these emerging pathogens. In Europe, particularly in France, most glycopeptide-intermediate Staphylococcus aureus strains display decreased susceptibility to teicoplanin but not to vancomycin.