Moraxella species are fastidious Gram-negative bacteria capable of causing opportunistic infections, including bloodstream infections, especially in immunocompromised patients. Data on their epidemiology, antimicrobial susceptibility, and phylogenomics in Europe remains limited. We conducted a multicentre, retrospective, observational study across 56 European hospital centres between January 1st 2020 and December 31st 2024. All Moraxella species isolated from blood cultures (BCs) were included. Species distribution and antimicrobial susceptibility profiles were analysed. We also performed a phylogenomic analysis of Moraxella genomes deposited in GenBank. A total of 709 Moraxella isolates were included. Moraxella osloensis (61.1

Introduction Aeromonas species are Gram-negative bacilli capable of causing bloodstream infections in both immunocompromised and otherwise healthy individuals. However, data on their epidemiology and antimicrobial resistance remain limited in Europe. Methods We conducted a multicentre, retrospective, observational study that included all Aeromonas species isolates recovered from blood cultures in 56 European hospitals between January 1st 2020 and December 31st 2024. Epidemiological features and antimicrobial susceptibility profiles were analyzed. Results A total of 590 Aeromonas isolates were included. Most were recovered from polymicrobial blood cultures (73.1%), and catheter-related bloodstream infections were frequent (21.7%). The most commonly reported species were A. caviae (30.1%), isolates without conclusive species identification (Aeromonas spp., 24.8%), A. hydrophila (20.7%), and A. veronii (19.1%). At the genus level, susceptibility to aztreonam, ceftazidime, and cefepime exceeded 90%. Resistance to fluoroquinolones (∼10%) and sulfamethoxazole/trimethoprim (up to 11%) was observed. Species-level analyses showed higher resistance rates to fluoroquinolones and sulfamethoxazole/trimethoprim among A. caviae and A. hydrophila, and increased resistance to ceftazidime among Aeromonas spp. Conclusions Aeromonas species in Europe showed high susceptibility to ceftazidime and cefepime, alongside with emerging resistance to fluoroquinolones and sulfamethoxazole/trimethoprim. Species-specific findings should be interpreted cautiously due to limitations in routine identification methods, underscoring the need for sustained surveillance and harmonised diagnostic standards across Europe.

Background. Descriptions of genomic characters and dynamics related to Pseudomonas aeruginosa (PA) adaptation and survival in hospital water networks remain scarce but necessary for sustainable water management in hospitals.Methods. A new copper water network in an intensive care unit (ICU) was chronically colonized by a genotype sequence type (ST) 299 of PA and sporadically by a genotype ST2685. Sixty-eight ST299-PA and four ST2685-PA strains from ICU-water samples collected over 29 months and 4 months, respectively, were studied for genomic adaptation to copper water network. PFGE and whole-genome sequencing allowing SNP, comparative genomics, resistome, virulome and pangenome analyses were performed. In order to understand the adaptive phenomena linked to the colonization niche, 16 isolates of ST299-PA colonizing a cystic fibrosis (CF) patient during 16 months were included.Results and discussion. The 68 ST299-PA ICU-water differed by <0.15 SNPs on average. No recombination regions nor patho-adaptive mutations were identified. Resistome, virulome and pangenome were stable over the time. The genomic content included a copper resistance operon, mainly metal resistance genes, a Tn4661-like transposon, the class 1 integron and broad-spectrum efflux pumps. These elements, absent in ST2685-PA ICU-water, support the survival of ST299-PA in the copper water network. The evolutionary speed of ST299-PA CF was faster with 12.9 SNPs among strains mostly affecting genes of patho-adaptation, arguing that the primo-colonization strain was probably not adapted to the niche, in contrast to the high genomic stability observed for the ST299-PA ICU-water population signifying the primary adaptation to the water network.

Finegoldia spp. are Gram-positive anaerobic cocci increasingly recognized as opportunistic pathogens, particularly in bone infections. Linezolid (LZD), an oxazolidinone with activity against anaerobes, is frequently used in orthopedic infections but is subject to various resistance mechanisms. Here, we characterized the molecular basis of LZD resistance in Finegoldia sp. isolates from three separate cases of bone infection. Antimicrobial susceptibility testing (AST) was performed according to Antibiotic Susceptibility Committee of the French Society of Microbiology (CA-SFM) recommendations. Whole-genome sequences were analyzed to challenge mass spectrometry identification (ANIb, isDDH), determine isolate relatedness (SNP analysis), and characterize the genetic support of resistance (ABRicate, AMRFinderPlus). LZD-resistant strains were isolated following LZD treatment in all three patients. In one case, low SNP divergence between susceptible and resistant isolates supported in vivo emergence of resistance. Genomic analyses suggested that the strains probably belong to undescribed Finegoldia species. LZD resistance was mediated by the cfr(C) gene encoding a 23S rRNA methyltransferase, and in two isolates with high-level resistance, was associated with a G71D mutation in the ribosomal protein L4-encoding gene. The cfr(C) gene was located on two distinct integrative and conjugative elements closely related to ones previously described in Clostridioides difficile and Faecalibacterium taiwanense. In anaerobes, LZD resistance remains rarely reported in the literature, except in non-fragilis Bacteroides species. However, LZD resistance in the Finegoldia genus highlighted in this study supports the need for systematic AST of Finegoldia sp. isolates, particularly in polymicrobial infections, when LZD is considered for the treatment. If LZD is ineffective, tedizolid testing may be suggested as a potential therapeutic alternative.

Achromobacter xylosoxidans is an opportunistic pathogen in both cystic fibrosis (CF) and non-CF patients, in whom biofilm formation contributes to bacterial persistence and antibiotic tolerance. This study aimed to characterize early and mature biofilm formation in 57 clinical A. xylosoxidans isolates using complementary and physiologically relevant approaches and to compare biofilm phenotypes according to isolate origin (CF/non-CF). Early adhesion was assessed using the Biofilm Ring Test®, mature biofilm viable biomass was quantified under static conditions by colony-forming units counts, and biofilm dynamics were analyzed in a continuous-flow microfluidic system. The effects of five clinically relevant antibiotics (trimethoprim-sulfamethoxazole, piperacillin-tazobactam, meropenem, imipenem, and cefiderocol) were evaluated under dynamic conditions at sub-inhibitory concentrations (0.5 × Minimum Inhibitory Concentration (MIC)) and on preformed biofilm at inhibitory concentrations (10 × MIC). Non-CF isolates displayed faster early adhesion than CF isolates, whereas mature biofilm biomass was comparable between groups. If early adhesion did not predict mature biofilm biomass, dynamic biofilm coverage under flow conditions correlated with static mature biofilm levels. Sub-inhibitory antibiotic concentrations failed to prevent initial adhesion and elicited three distinct responses: biofilm formation enhancement (piperacillin-tazobactam, meropenem, imipenem), no effect (trimethoprim-sulfamethoxazole), or biofilm reduction (cefiderocol). Exposing mature biofilm to 10 × MIC identified trimethoprim-sulfamethoxazole and cefiderocol as the most effective agents in biofilm biomass reduction, whereas carbapenems and piperacillin-tazobactam were less effective. These findings provide new insights into A. xylosoxidans biofilm biology and may help guide therapeutic strategies for infections caused by this emerging, increasingly drug-resistant pathogen.

Objectives Epidemiological studies on Bacteroides fragilis group (BFG) species and their antimicrobial resistance (AMR) profiles remain scarce worldwide and are lacking in France. The aim of this study was to provide comprehensive national data on the distribution of BFG species, isolation sites, AMR and its potential regional disparity. Methods A retrospective multicenter study was conducted from January 2022 to December 2023 using routine data from 45 French hospitals. A total of 9,458 BFG isolates identified to the species level by MALDI-ToF were included. Antimicrobial susceptibility testing (AST) was performed according to French guidelines using either disc diffusion or gradient diffusion methods. AST results were collected for ten antibiotics: amoxicillin-clavulanate (AMC), piperacillin-tazobactam (PIT), imipenem (IMI), clindamycin (CLI), metronidazole (MET), moxifloxacin, tigecycline, linezolid, rifampicin, and chloramphenicol. A Bayesian statistical model was applied to estimate regional resistance frequencies with corresponding credible intervals. Results Bacteroides fragilis sensu stricto (B. fragilis) was the most prevalent species (62.4%), followed by Bacteroides thetaiotaomicron (14.2%). Resistance to IMI and MET remained low, while AMC, PIT, and CLI resistance varied markedly across species: 5.2%, 3.6%, and 34.4% for B. fragilis; 18.0%, 50.1%, and 72.9% for B. thetaiotaomicron; and 32.1%, 19.5%, and 75.2% for Parabacteroides distasonis, respectively. Bayesian modelling produced robust regional estimates for B. fragilis, revealing noticeable regional disparities, particularly for AMC, PIT, and MET. Conclusion Bayesian modeling revealed substantial interspecies and interregional differences in BFG resistance, highlighting the importance of species-level identification and localized surveillance to inform empirical antibiotic therapy.

INTRODUCTION:Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas and Acinetobacter species remain largely underrepresented in systematic surveillance programs across Europe. METHODS:We conducted a multicentre retrospective observational study analysing all minor NFGNB isolates recovered from blood cultures in 56 European Hospital Centres over a 5-year period (2020-2024). Diagnostic approach, epidemiology and antimicrobial susceptibility according to European Committee on Antimicrobial Susceptibility Testing v. 15.0 were investigated. RESULTS:A total of 4420 minor NFGNB isolates were included. In 43.6% of cases, the isolates were recovered from polymicrobial blood cultures, and 40.6% were detected during microbiologically defined catheter-related bloodstream infections. Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-ToF) mass spectrometry was the most widely used tool for species identification (98%). Antimicrobial susceptibility testing was conducted in all centres, using mostly broth microdilution commercial systems (57%), disk diffusion (57%) and gradient diffusion MIC strip (54%) methods, mainly according to European Committee on Antimicrobial Susceptibility Testing guidelines (67.9%). The most prevalent species were Stenotrophomonas maltophilia (52.4%), Achromobacter xylosoxidans (7.8%), Sphingomonas paucimobilis (5.3%) and the Burkholderia cepacia complex (4.8%). S. maltophilia displayed a high rate of resistance to sulfamethoxazole/trimethoprim (11%), and 2% of the isolates were found to be likely resistant to cefiderocol. A. xylosoxidans showed high resistance to meropenem (10%), piperacillin/tazobactam (24%) and sulfamethoxazole/trimethoprim (53%) when tested by MIC methods, while showing over 90% susceptibility to meropenem when tested by disk diffusion. S. paucimobilis displayed over 90% susceptibility to amoxicillin/clavulanate, ampicillin/sulbactam, imipenem, meropenem and tetracycline. CONCLUSIONS:This study provides an updated overview of the diagnostic approaches and epidemiology of minor NFGNB across Europe, supporting future comparative analyses and improved diagnostic and antimicrobial strategies.

Cefiderocol, a newly introduced siderophore cephalosporin, exhibits activity against various multidrug-resistant (MDR) Gram-negative bacilli (GNB), including producers of Ambler class A, B and D carbapenemases. The TROJAN-MDR study aimed to (i) compare the in vitro activity of cefiderocol with other last-resort antibiotics against a well-characterized collection of Enterobacterales and Pseudomonas aeruginosa strains from Southern France, and (ii) assess the performance of available cefiderocol antimicrobial susceptibility testing (AST) methods. The collection comprised 127 Enterobacterales from various clones, including 119 carbapenemase producers (93.7

The colonization and persistence of Pseudomonas aeruginosa in chronically diseased lungs are driven by various virulence factors. However, pulmonary infections in cystic fibrosis (CF) patients are predominantly polymicrobial. While Achromobacter xylosoxidans is an opportunistic pathogen in these patients, its impact on P. aeruginosa virulence during co-infection remains largely unknown. This study investigated P. aeruginosa interaction with two clonally related A. xylosoxidans strains, Ax 198 and Ax 200, co-isolated from CF sputum. We found that the interaction was strain-dependent, with Ax 200 significantly reducing P. aeruginosa virulence in a zebrafish model, providing the first in vivo evidence of this interaction. Proteomic analysis revealed that P. aeruginosa proteome was differently impacted by the two A. xylosoxidans strains, with Ax 200 altering proteins involved in biofilm formation, swimming motility, iron acquisition, and secretion systems. These findings were validated by phenotypic assays, confirming that A. xylosoxidans affected major P. aeruginosa virulence phenotypes, including biofilm formation, swimming motility, and siderophore production. Genetic analysis confirmed that distinct regulatory mechanisms, including iron cycle pathways, may account for the strain-dependent effects. These findings reveal a novel multi-target competitive mechanism through which A. xylosoxidans significantly disrupts P. aeruginosa virulence.

SUMMARYDiabetic foot infections (DFI) are a public health problem worldwide. DFI are polymicrobial, biofilm-associated infections involving complex bacterial communities organized in functional equivalent pathogroups, all including anaerobes. Indeed, multiple pathophysiological factors favor the growth of anaerobes in this context. However, the prevalence, role, and contribution of anaerobes in wound evolution remain poorly characterized due to their challenging detection. Studies based on culture reviewed herein showed a weighted average of 17% of patients with anaerobes. Comparatively, the weighted average of patients with anaerobes identified by 16S rRNA gene sequencing was 83.8%. Culture largely underestimated not only the presence but also the diversity of anaerobes compared with cultivation-independent approaches but both methods showed that anaerobic Gram-negative bacilli and Gram-positive cocci were the most commonly identified in DFI. Anaerobes were more present in deeper lesions, and their detection was associated with fever, malodorous lesions, and ulcer depth and duration. More specifically, initial abundance of Peptoniphilus spp. was associated with ulcer-impaired healing, Fusobacterium spp. detection was significantly correlated with the duration of DFI, and the presence of Bacteroides spp. was significantly associated with amputation. Antimicrobial resistance of anaerobes in DFI remains slightly studied and warrants more consideration in the context of increasing resistance of the most frequently identified anaerobes in DFI. The high rate of patients with DFI-involving anaerobes, the increased knowledge on the species identified, their virulence factors, and their potential role in wound evolution support recommendations combining debridement and antibiotic therapy effective on anaerobes in moderate and severe DFI.

Cefiderocol is a siderophore-conjugated cephalosporin increasingly used in the management of Achromobacter infections. Testing for cefiderocol susceptibility is challenging with distinct recommendations depending on the pathogens. We evaluated the performance of commercial tests for testing cefiderocol susceptibility in the Achromobacter genus and reviewed the literature. Diffusion (disks, MIC gradient test strips [MTS], Liofilchem) and broth microdilution (BMD) methods (ComASP™, Liofilchem; UMIC®, Bruker) were compared with the BMD reference method according to the EUCAST guidelines on 143 Achromobacter strains from 14 species with MIC50/90 of ≤ 0.015/0.5 mg/L. A literature search was conducted regardless of method or species. None of the methods tested fulfilled an acceptable essential agreement (EA). MTS displayed the lowest EA (30.8

Objectives: To assess the performance of the rapid syndromic BioFire (R) Joint Infection Panel (BF-JIP) to detect bacterial and fungal pathogens, as well as antibiotic resistance genes, directly in synovial fluid specimens collected from patients with acute arthritis. Methods: The study was conducted in six French bacteriological laboratories. To assess the performances of BF-JIP, results were compared with those of synovial fluid 14 -day culture and, in case of discrepancy, with those of complementary molecular methods and intraoperative samples. A total of 308 synovial fluid specimens were tested after collection from 308 adults and children presenting with clinical and biological suspicion of acute arthritis; patients presenting with acute periprosthetic joint infection were included according to the European Bone and Joint Infection Society 2021 criteria. Results: Only one specimen failed (no result). On the basis of the consolidated data, the BF-JIP was concordant with the 14 -day culture in 280 (91.2%) of the 307 specimens finally included in the study. The positive percentage agreement was 84.9% (95% CI, 78.8-89.8%) and the negative percentage agreement was 100% (95% CI, 97.2-10 0%). The positive predictive value was extremely high (100%; 95% CI, 97.6 -10 0%), whereas the negative predictive value was lower (82.6%; 95% CI, 75.7-88.2%), partially explained by the missing target species in the panel. Discussion: The BF-JIP showed high performances to detect pathogens involved in acute arthritis. Tiphaine Gaillard, Clin Microbiol Infect 2024;30:905 (c) 2024 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Objective: To assess the residual risk of waterborne contamination by Pseudomonas aeruginosa from a water network colonized by a single genotype [sequence type (ST) 299] despite the presence of antimicrobial filters in a medical intensive care unit (ICU). Methods: During the first 19-month period since the ICU opened, contamination of the water network was assessed monthly by collecting water upstream of the filters. Downstream water was also sampled to assess the efficiency of the filters. P. aeruginosa isolates from patients were collected and compared with the waterborne ST299 P. aeruginosa by multiplex-rep polymerase chain reaction (PCR), pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing. Cross-transmission events by other genotypes of P. aeruginosa were also assessed. Results: Overall, 1.3% of 449 samples of filtered water were positive for P. aeruginosa in inoculum, varying between 1 and 10 4 colony-forming units/100 mL according to the tap. All P. aeruginosa hydric isolates belonged to ST299 and displayed fewer than two single nucleotide polymorphisms (SNPs). Among 278 clinical isolates from 122 patients, 10 isolates in five patients showed identical profiles to the hydric ST299 clone on both multiplex-rep PCR and PFGE, and differed by an average of fewer than five SNPs, confirming the water network reservoir as the source of contamination by P. aeruginosa for 4.09% of patients. Cross -transmission events by other genotypes of P. aeruginosa were responsible for the contamination of 1.75% of patients. Discussion/conclusion: Antimicrobial filters are not sufficient to protect patients from waterborne pathogens when the water network is highly contaminated. A microbiological survey of filtered water may be needed in units hosting patients at risk of P. aeruginosa infections, even when all water points -of -use are fitted with filters. 2024 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

ABSTRACTAchromobacter spp. are opportunistic pathogens of environmental origin increasingly isolated in patients with underlying conditions like cystic fibrosis (CF). Despite recent advances, their virulence factors remain incompletely studied, and siderophore production has not yet been investigated in this genus. The aim of this study was to evaluate the production of siderophores in a large collection of Achromobacter spp. and evaluate the variability according to the origin of the strain and species. A total of 163 strains were studied, including 128 clinical strains (CF and non-CF patients) and 35 strains of environmental origin. Siderophores were quantified by the liquid chrome azurol-sulphonate assay. Species were identified by nrdA gene-based phylogeny. Strains were assigned to 20 species, with Achromobacter xylosoxidans being the most represented (51.5% of strains). Siderophore production was observed in 72.4% of the strains, with amounts ranging from 10.1% to 90% siderophore units. A significantly higher prevalence of siderophore-producing strains and greater production of siderophores were observed for clinical strains compared with strains of environmental origin. Highly variable observations were made according to species: A. xylosoxidans presented unique characteristics (one of the highest prevalence of producing strains and highest amounts produced, particularly by CF strains). Siderophores are important factors for bacterial growth commonly produced by members of the Achromobacter genus. The significance of the observations made during this study must be further investigated. Indeed, the differences observed according to species and the origin of strains suggest that siderophores may represent important determinants of the pathophysiology of Achromobacter spp. infections and also contribute to the particular epidemiological success of A. xylosoxidans in human infections.IMPORTANCEAchromobacter spp. are recognized as emerging opportunistic pathogens in humans with various underlying diseases, including cystic fibrosis (CF). Although their pathophysiological traits are increasingly studied, their virulence factors remain incompletely described. Particularly, siderophores that represent important factors of bacterial growth have not yet been studied in this genus. A population-based study was performed to explore the ability of members of the Achromobacter genus to produce siderophores, both overall and in relevant subgroups (Achromobacter species; strain origin, either clinical—from CF or non-CF patients—or environmental). This study provides original data showing that siderophore production is a common trait of Achromobacter strains, particularly observed among clinical strains. The major species, Achromobacter xylosoxidans, encompassed both one of the highest prevalence of siderophore-producing strains and strains producing the largest amounts of siderophores, particularly observed for CF strains. These observations may represent additional advantages accounting for the epidemiological success of this species.

Abstract Background Achromobacter spp. are opportunistic pathogens, mostly infecting immunocompromised patients and patients with cystic fibrosis (CF) and considered as difficult-to-treat pathogens due to both intrinsic resistance and the possibility of acquired antimicrobial resistance. Species identification remains challenging leading to imprecise descriptions of resistance in each taxon. Cefiderocol is a broad-spectrum siderophore cephalosporin increasingly used in the management of Achromobacter infections for which susceptibility data remain scarce. We aimed to describe the susceptibility to cefiderocol of a collection of Achromobacter strains encompassing different species and isolation sources from CF or non-CF (NCF) patients. Methods We studied 230 Achromobacter strains (67 from CF, 163 from NCF patients) identified by nrdA gene-based analysis, with available susceptibility data for piperacillin–tazobactam, meropenem and trimethoprim–sulfamethoxazole. Minimal inhibitory concentrations (MICs) of cefiderocol were determined using the broth microdilution reference method according to EUCAST guidelines. Results Strains belonged to 15 species. A. xylosoxidans represented the main species (71.3%). MICs ranged from ≤ 0.015 to 16 mg/L with MIC50/90 of ≤ 0.015/0.5 mg/L overall and 0.125/2 mg/L against 27 (11.7%) meropenem-non-susceptible strains. Cefiderocol MICs were not related to CF/NCF origin or species although A. xylosoxidans MICs were statistically lower than those of other species considered as a whole. Considering the EUCAST non-species related breakpoint (2 mg/L), 228 strains (99.1%) were susceptible to cefiderocol. The two cefiderocol-resistant strains (A. xylosoxidans from CF patients) represented 3.7% of meropenem-non-susceptible strains and 12.5% of MDR strains. Conclusions Cefiderocol exhibited excellent in vitro activity against a large collection of accurately identified Achromobacter strains, irrespective of species and origin.

Achromobacter spp. are emerging pathogens in CF. Based on intrinsic resistance and the report of multidrug resistant strains, Achromobacter spp. are considered as difficult-to-treat pathogens. Cefiderocol is a novel siderophore cephalosporin that has been infrequently used in the management of Achromobacter infections and for which susceptibility data are lacking. We evaluated the cefiderocol susceptibility of a collection of CF Achromobacter strains encompassing different airway colonization types, species and antimicrobial susceptibility patterns. A total of 110 clinically-documented Achromobacter strains from 70 CF patients were included. Strains were identified by nrdA gene sequencing. Antimicrobial susceptibility testing included a standard antibiogram and cefiderocol susceptibility testing using disk diffusion method and Minimal Inhibitory Concentration (MIC) determination by both Etest and ComASP™ microdilution performed according to CA-SFM/EUCAST guidelines. Isolates displayed a high nrdA allele diversity and belonged to 9 species and a group of unassigned isolates. Preliminary results showed: i) MIC values of 0.064 to 1 mg/mL, ii) a A. insuavis strain displaying a MIC of 4 mg/mL, above the resistance breakpoint, iii) an additional incubation time required for the ComASP™ MIC to be readable for some isolates. A full report of the distribution of MIC determined by microdilution will be presented and compared with the distribution of MIC and inhibition zone diameters determined by agar diffusion to evaluate the more accurate method to be used for Achromobacter spp. The study will provide original results on the distribution of MICs and inhibition zone diameters of cefiderocol for a large collection of CF Achromobacter strains with clinical and microbiological documentation allowing specific observations for A. xylosoxidans, the most frequently identified species in CF, and other clinically-relevant species.

Daptomycin (DAP) represents an interesting alternative to treat methicillin-resistant Staphylococcus aureus (MRSA) infections. Different mechanisms of DAP resistance have been described; however, in vivo-acquired resistance is uncharacterized. This study described the phenotypic and genotypic evolution of MRSA strains that became resistant to DAP in two unrelated patients with bacteremia under DAP treatment, in two hospitals in the South of France. DAP MICs were determined using broth microdilution method on the pairs of isogenic (DAP-S/DAP-R) S. aureus isolated from bloodstream cultures. Whole genome sequencing was carried out using Illumina MiSeq Sequencing system. The two cases revealed DAP-R acquisition by MRSA strains within three weeks in patients treated by DAP. The isolates belonged to the widespread ST5 (patient A) and ST8 (patient B) lineages and were of spa-type t777 and t622, respectively. SNP analysis comparing each DAP-S/DAP-R pair confirmed that the isolates were isogenic. The causative mutations were identified in MprF (Multiple peptide resistance Factor) protein: L826F (Patient A) and S295L (Patient B), and in Cls protein: R228H (Patient B). These proteins encoded both proteins of the lipid biosynthetic enzymes. The resistance to DAP is particularly poorly described whereas DAP is highly prescribed to treat MRSA. Our study highlights the non-systematic cross-resistance between DAP and glycopeptides and the importance of monitoring DAP MIC in persistent MRSA bacteremia.

In cystic fibrosis (CF), Pseudomonas aeruginosa (Pa) is a major pathogen that can persistently colonize patients. Genetic studies showed a high diversity of Pa, the success of widespread or 'international' clones and described epidemic clones in CF and Epidemic High-Risk (ERH) clones. Here, we characterized Pa genetic diversity over time after first colonization in CF patients, with the aim of accurately describing the dynamics of colonization in a context of scarce longitudinal studies including the first isolated Pa strain. Results represent the first genotyping data available for CF Pa in France. Forty-four CF patients with a first Pa colonization were included; 265 strains collected over 7 years in these patients were genotyped by multiplex rep-PCR, multilocus sequence typing, pulsed-field gel electrophoresis and/or whole genome sequencing. Forty-one sequence types were identified: 4 were unknown, 22 never previously reported for CF patients, and 6 corresponded to widespread clones colo-nizing 16 patients (36%). Unrelated strains were identified in 41 patients (93%). Twenty-six patients (59%) presented a recurrence during the study period. No specific clones were associated with transient, recurrent or persistent colonization. Our longitudinal study revealed that 9 of the 26 patients with recurrence (35%) harbored strains of different genotypes. Great genetic diversity was observed among initial Pa isolates excluding any cross -transmission. Persistent colonization may appear more complex than expected, imitating persistence, with successive colonization events by unrelated Pa.