Evaluation of the Reveal® rapid AST system to assess the susceptibility of Pseudomonas aeruginosa from blood cultures.

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 ß-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.

Mutations in ß-Lactamase AmpC Increase Resistance of Pseudomonas aeruginosa Isolates to Antipseudomonal Cephalosporins.

Mutation-dependent overproduction of intrinsic ß-lactamase AmpC is considered the main cause of resistance of clinical strains of Pseudomonas aeruginosa to antipseudomonal penicillins and cephalosporins. Analysis of 31 AmpC-overproducing clinical isolates exhibiting a greater resistance to ceftazidime than to piperacillin-tazobactam revealed the presence of 17 mutations in the ß-lactamase, combined with various polymorphic amino acid substitutions. When overexpressed in AmpC-deficient P. aeruginosa 4098, the genes coding for 20/23 of these AmpC variants were found to confer a higher (2-fold to >64-fold) resistance to ceftazidime and ceftolozane-tazobactam than did the gene from reference strain PAO1. The mutations had variable effects on the MICs of ticarcillin, piperacillin-tazobactam, aztreonam, and cefepime. Depending on their location in the AmpC structure and their impact on ß-lactam MICs, they could be assigned to 4 distinct groups. Most of the mutations affecting the omega loop, the R2 domain, and the C-terminal end of the protein were shared with extended-spectrum AmpCs (ESACs) from other Gram-negative species. Interestingly, two new mutations (F121L and P154L) were predicted to enlarge the substrate binding pocket by disrupting the stacking between residues F121 and P154. We also found that the reported ESACs emerged locally in a variety of clones, some of which are epidemic and did not require hypermutability. Taken together, our results show that P. aeruginosa is able to adapt to efficacious ß-lactams, including the newer cephalosporin ceftolozane, through a variety of mutations affecting its intrinsic ß-lactamase, AmpC. Data suggest that the rates of ESAC-producing mutants are ≥1.5% in the clinical setting.

Recurrent pyelonephritis due to NDM-1 metallo-beta-lactamase producing Pseudomonas aeruginosa in a patient returning from Serbia, France, 2012.

We describe the first isolation in France of a New-Delhi metallo-beta-lactamase-1 (NDM-1) producing Pseudomonas aeruginosa. In March 2012, a patient with history of prior hospitalisation in Serbia was diagnosed in France with acute pyelonephritis due to NDM-1 producing P. aeruginosa. Clinical and microbiological cure was obtained under appropriate antibiotic treatment. Two months later, she presented with a recurrence due to the same bacteria, with a favourable evolution. During both hospitalisations, contact isolation precautions were implemented and no cross-transmission was observed.

Elizabethkingia anophelis outbreak in France.

OBJECTIVE: We report an outbreak of Elizabethkingia anophelis infections in France. To the best of our knowledge, this is the first outbreak described in Europe. METHODS: Each E. anophelis-positive microbiological sample was considered a case. All patients were hospitalized in an infectious diseases unit. Clinical, environmental, and microbiological investigations (MALDI-TOF mass spectrometry, PCR, E-test) were performed for each case. RESULTS: Twenty cases were reported from September 2020 to September 2021, mainly community-acquired infections, responsible for nine deaths. The phylogenetic analysis showed a clonal origin and excluded nosocomial transmission. Despite the analysis of multiple environmental specimens, no source of contamination was identified. All strains were highly resistant to cefotaxime, ceftazidime, and imipenem. CONCLUSIONS: Clinicians and microbiologists should be aware of this multidrug-resistant bacterium, capable of causing severe infections. Most strains showed the lowest minimum inhibitory concentration values for cotrimoxazole and ciprofloxacin, making them the best choice for empirical antibiotic therapy.

Number, type and cost of microbiological tests during HIV Pre-Exposure Prophylaxis: The experience of a French hospital.

BACKGROUND: Microbiological tests are required for individuals on HIV Pre-Exposure Prophylaxis (PrEP), but their real-life numbers, types and cost are poorly described. METHODS: Number, type, and results of microbiological tests performed in a Besançon Hospital-associated laboratory, France, from 2016 to 2019, in the setting of PrEP consultations were retrospectively collected. Costs were estimated by the current reimbursement rate set by the French national protection system. RESULTS: 756 consultations for PrEP initiation or follow-up of 135 persons were performed over 4 years. Among 3434 tests performed in the institution-associated laboratory, 1083 and 2351 were virological and bacteriological tests, respectively. Serology was predominant in virology (98% of virological tests), with HIV, HCV, and HBV screening as the 3 more frequent assays, whereas molecular biology was predominant in bacteriology (63.1% of bacteriological tests) with N. gonorrhoeae and C. trachomatis screening as leader assays. Agar-based culture accounted for 1% of bacterial tests. The global cost of microbiological tests was 45,983.20 euros, corresponding to a mean cost of 60.80 euros per consultation. Virological and bacteriological tests accounted for 37.7% and 62.3% of this budget, respectively. No seroconversion was observed for HIV or HCV. N. gonorrhoeae and C. trachomatis were detected at least once in 39.3% and 22.4% of individuals, respectively, with 15% of symptomatic episodes in both cases. Active syphilis infection was detected in 15.4% of individuals. CONCLUSIONS: Since numerous microbiological tests are required during PrEP, the availability of specific technical platforms should not be neglected by centers wishing to set up PrEP consultations.

[Low-level resistance to fluoroquinolones conferred by efflux overproduction in Pseudomonas aeruginosa: clinical significance and routine detection]. / Résistance de bas niveau aux fluoroquinolones par surexpression de l'efflux chez Pseudomonas aeruginosa: conséquences thérapeutiques et détection au laboratoire.

The aim of this study was (i) to assess the impact of stable overproduction of efflux systems MexAB-OprM and MexXY-OprM on the bacteriostatic activities of fluoroquinolones in clinical Pseudomonas aeruginosa strains and (ii) to find a convenient test for screening isolates with a low level resistance to fluoroquinolones. The minimal inhibitory concentrations (MICs) of ciprofloxacin and levofloxacin were determined for clinical isolates of P. aeruginosa overexpressing MexAB-OprM or MexXY-OprM. Efflux pumps derepression was associated with a modest two- to fourfold increase in resistance to the tested fluoroquinolones. Clinical significance of low level resistance conferred by the efflux mechanism was evaluated with a Monte Carlo simulation with various fluoroquinolone regimens. With this model, low levels of resistance to ciprofloxacin (MIC > or =0.25 mg/L) or levofloxacin (MIC > or =1 mg/L) such as those due to overproduced MexAB-OprM or MexXY-OprM were predicted to result in poor clinical outcomes. Altogether these data strongly suggest that when derepressed MexAB-OprM or MexXY-OprM provides P. aeruginosa with a resistance that may be sufficient to impair the efficacy of single therapy with highly potent fluoroquinolones such as ciprofloxacin and levofloxacin. Routine detection of clinical strains that displayed low-level resistance to fluoroquinolones with a Mueller Hinton agar containing 0.20 mg/L of ciprofloxacin will help clinician in his therapeutical choice.