Synergistic effect of tryptamine-urea derivatives to overcome the chromosomally-mediated colistin resistance in Klebsiella pneumoniae

Colistin is considered as the last-resort antibiotics to treat multi-drug resistant Gram-negative bacterial infections in humans. However, the clinical use of colistin was limited because of the apparition of chromosomal mutations and mobile colistin resistance genes in bacterial isolates. One promising strategy is to combine existing antibiotics with promising non-antibiotics to overcome the widespread emergence of antibiotic-resistant pathogens. Moreover, colistin resistance would be regulated by two component systems PhoP/PhoQ which leads to permanent synthesis of cationic groups compensating for Mg2+ deficiency. In this study, the synthesis of a small library of tryptamine urea derivatives was carried out. In addition, antibiotic susceptibility, antibiotic adjuvant screening and checkerboard assays were used to investigate the antibacterial activity of these synthesized compounds and the potential synergistic activity of their combination with colistin. Conformational analysis of the docked binding modes of the active compound in the predicted binding pocket of bacterial response regulator PhoP were carried out, to see if the active compound inhibits PhoP which is involved in colistin resistance. Finally, hemolytic activity studies have been conducted on the most active compound.

Continuous infusion of meropenem-vaborbactam for a KPC-3-producing Klebsiella pneumoniae bloodstream infection in a critically ill patient with augmented renal clearance

PURPOSE

To demonstrate the feasibility of continuous infusion of meropenem-vaborbactam to optimize the treatment of carbapenem-resistant Enterobacterales.

METHODS

Report of a case of a Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae bloodstream infection comfirmed by whole genome sequencing and therapeutic drug monitoring (TDM) of meropenem.

RESULTS

A patient with augmented renal clearance (ARC) went into septic shock caused by an ST11 KPC-3-producing K. pneumoniae bloodstream infection that was successfully treated with a continuous infusion of meropenem-vaborbactam at a dosage of 1 g/1 g q4h as a 4-h infusion. TDM confirmed sustained concentrations of meropenem ranging from 8 to 16 mg/L throughout the dosing interval.

CONCLUSION

Continuous infusion of meropenem-vaborbactam was feasible. It could be appropriate for optimizing the management of critically ill patients with ARC, as it resulted in antibiotic concentrations above the minimum inhibitory concentration for susceptible carbapenem-resistant Enterobacterales (up to 8 mg/L) throughout the dosing interval.

In Vivo-Acquired Resistance to Daptomycin during Methicillin-Resistant Staphylococcus aureus Bacteremia

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.

Contribution of efflux and mutations in fluoroquinolone susceptibility in MDR enterobacterial isolates: a quantitative and molecular study

OBJECTIVES

The emergence of MDR strains is a public health problem in the management of associated infections. Several resistance mechanisms are present, and antibiotic efflux is often found at the same time as enzyme resistance and/or target mutations. However, in the laboratory routinely, only the latter two are identified and the prevalence of antibiotic expulsion is underestimated, causing a misinterpretation of the bacterial resistance phenotype. The development of a diagnostic system to quantify the efflux routinely would thus improve the management of patients.

METHODS

A quantitative technique based on detection of clinically used fluoroquinolones was investigated in Enterobacteriaceae clinical strains with a high or basal efflux activity. The detail of efflux involvement was studied from MIC determination and antibiotic accumulation inside bacteria. WGS was carried out on selected strains to determine the genetic background associated with efflux expression.

RESULTS

Only 1 Klebsiella pneumoniae isolate exhibited a lack of efflux whereas 13 isolates had a basal efflux and 8 presented efflux pump overexpression. The antibiotic accumulation evidenced the efficacy of the efflux mechanism in strains, and the contribution of dynamic expulsion versus target mutations in fluoroquinolone susceptibility.

CONCLUSIONS

We confirmed that phenylalanine arginine β-naphthylamide is not a reliable marker of efflux due to the affinity of the AcrB efflux pump for different substrates. We have developed an accumulation test that can be used efficiently on clinical isolates collected by the biological laboratory. The experimental conditions and protocols ensure a robust assay that with improvements in practice, expertise and equipment could be transferred to the hospital laboratory to diagnose the contribution of efflux in Gram-negative bacteria.

Antimicrobial activity of antibiotics on biofilm formed by Staphylococcus aureus and Pseudomonas aeruginosa in an open microfluidic model mimicking the diabetic foot environment

BACKGROUND

Diabetic foot infections (DFIs) represent a public health problem because of their frequency and the severity of their consequences, i.e. amputation and mortality. Polymicrobial biofilms on the skin surface of these ulcers complicate wound healing. Few in vitro models exist to study the antibiotics activity in this context.

OBJECTIVES

This study evaluated the in vitro activity of antibiotics against the two main bacteria isolated in DFI, Staphylococcus aureus and Pseudomonas aeruginosa, using a dynamic system (BioFlux™ 200) and a chronic wound-like medium (CWM) that mimic the foot ulcer environment.

METHODS

Reference strains and two pairs of clinical S. aureus and P. aeruginosa isolated together from a DFI were cultivated in brain heart infusion and CWM media during 72 h at 37°C, alone and combined in the BioFlux™ 200 system. Antibiotic activity was evaluated after a mechanical debridement. The activities were measured by the reduction of biofilm percentage of bacteria in the microfluidic system using microscopy.

RESULTS

Daptomycin for S. aureus and ceftazidime for P. aeruginosa showed excellent activity to reduce biofilm biomass, whereas linezolid action was more mitigated and dalbavancin was ineffective. Ceftazidime + daptomycin presented the most potent in vitro activity on a mixed biofilm.

CONCLUSIONS

The combination of CWM and the BioFlux™ microfluidic system represents a valuable tool to screen the potential antimicrobial activity of antibiotics under conditions mimicking those encountered in DFI. It could help clinicians in their management of chronic wounds.

Effect of Antibiotic Exposure on Staphylococcus epidermidis Responsible for Catheter-Related Bacteremia

Coagulase-negative staphylococci (CoNS) and especially Staphylococcus epidermidis are responsible for health care infections, notably in the presence of foreign material (e.g., venous or central-line catheters). Catheter-related bacteremia (CRB) increases health care costs and mortality. The aim of our study was to evaluate the impact of 15 days of antibiotic exposure (ceftobiprole, daptomycin, linezolid and vancomycin) at sub-inhibitory concentration on the resistance, fitness and genome evolution of 36 clinical strains of S. epidermidis responsible for CRB. Resistance was evaluated by antibiogram, the ability to adapt metabolism by the Biofilm Ring test^® and the in vivo nematode virulence model. The impact of antibiotic exposure was determined by whole-genome sequencing (WGS) and biofilm formation experiments. We observed that S. epidermidis strains presented a wide variety of virulence potential and biofilm formation. After antibiotic exposure, S. epidermidis strains adapted their fitness with an increase in biofilm formation. Antibiotic exposure also affected genes involved in resistance and was responsible for cross-resistance between vancomycin, daptomycin and ceftobiprole. Our data confirmed that antibiotic exposure modified bacterial pathogenicity and the emergence of resistant bacteria.

Last resort beta-lactam antibiotics for treatment of New-Delhi Metallo-Beta-Lactamase producing Enterobacterales and other Difficult-to-Treat Resistance in Gram-negative bacteria: A real-life study

Introduction

Novel last resort beta-lactam antibiotics are now available for management of infections due to New-Delhi Metallo-Beta-Lactamase (NDM) producing Enterobacterales and non-fermenters with Difficult-to-Treat Resistance. However, data regarding the use of imipenem-cilastatin-relebactam (IMI-REL), cefiderocol (CFD) and ceftazidime-avibactam plus aztreonam (CAZ-AVI-ATM) are scarce in real-life settings. This study aimed to describe the use of last resort beta-lactam antibiotics, the microbiology and the outcome, in patients hospitalized in a tertiary hospital.

Methods

We conducted a monocentric observational cohort study from 2020/01/01, to 2022/08/31. We screened all patients admitted to Nimes University Hospital who have received ≥ 1 dose of last resort beta-lactam antibiotics during the study period, using the Pharmacy database. We included patients treated with IMI-REL, CFD and CAZ-AVI-ATM. The primary endpoint was the infection-free survival rate. We also calculated rates of microbiological and clinical cure, recurrent infection, death and adverse events.

Results

Twenty-seven patients were included in the study and 30 treatment courses were analyzed: CFD (N=24; 80%), CAZ-AVI-ATM (N=3; 10%) and IMI-REL (N=3; 10%). Antibiotics were used in 21 males (70%) and 9 females (30%) with a median age at 65-year-old [50-73.5] and a median Charlson index at 1 [0-2]. Almost all the patients had ≥ 1 risk factor for carbapenem resistant bacteria, a half of them was hospitalized for severe COVID-19, and most of antibiotic courses (N=26; 87%) were associated with ICU admission. In the study population, the probability of infection-free survival at day-90 after last resort beta-lactam therapy initiation was 48.4% CI95% [33.2-70.5]. Clinical failure rate was at 30%, microbiological failure rate at 33% and mortality rate at 23%. Adverse events were documented in 5 antibiotic courses (17%). In details, P. aeruginosa were mainly treated with CFD and IMI-REL, S. maltophilia with CFD and CAZ-AVI-ATM, A. baumannii with CFD, and NDM producing-K. pneumoniae with CAZ-AVI-ATM and CFD. After a treatment course with CFD, CAZ-AVI-ATM and IMI-REL, the probability of infection-free survival was 48% CI95% [10.4-73.5], 33.3% CI95% [6.7-100], 66.7% CI95% [30-100], respectively.

Discussion/conclusion

Use of last resort beta-lactam antimicrobials in real-life settings was a safe and efficient therapeutic option for severe infections related to Gram-negative bacteria with Difficult-to-Treat Resistance.

Polymicrobial Biofilm Organization of Staphylococcus aureus and Pseudomonas aeruginosa in a Chronic Wound Environment

Biofilm on the skin surface of chronic wounds is an important step that involves difficulties in wound healing. The polymicrobial nature inside this pathogenic biofilm is key to understanding the chronicity of the lesion. Few in vitro models have been developed to study bacterial interactions inside this chronic wound. We evaluated the biofilm formation and the evolution of bacteria released from this biofilm on the two main bacteria isolated in this condition, Staphylococcus aureus and Pseudomonas aeruginosa, using a dynamic system (BioFlux™ 200) and a chronic wound-like medium (CWM) that mimics the chronic wound environment. We observed that all species constituted a faster biofilm in the CWM compared to a traditional culture medium (p < 0.01). The percentages of biofilm formation were significantly higher in the mixed biofilm compared to those determined for the bacterial species alone (p < 0.01). Biofilm organization was a non-random structure where S. aureus aggregates were located close to the wound surface, whereas P. aeruginosa was located deeper in the wound bed. Planktonic biofilm-detached bacteria showed decreased growth, overexpression of genes encoding biofilm formation, and an increase in the mature biofilm biomass formed. Our data confirmed the impact of the chronic wound environment on biofilm formation and on bacterial lifecycle inside the biofilm.

JS07.5.A 18F-fluciclovine PET and multi-parametric MRI to distinguish pseudoprogression from tumor progression in post-treatment glioblastoma

Background

Differentiation of tumor progression (TP) from pseudoprogression (PsP) is a major unmet need in glioblastoma (GBM). 18F-Fluciclovine is a synthetic amino acid PET radiotracer with higher uptake in tumor tissue vs. areas of treatment-related change. We aimed to assess the combined value of 18F-Fluciclovine PET and multi-parametric MRI for differentiating PsP from TP.

Material and Methods

We enrolled 30 patients with GBM with a new or enlarging contrast-enhancing lesion on MRI after chemoradiotherapy who were planned for surgical resection of the lesion. Patients underwent pre-operative 18F-Fluciclovine PET and multi-parametric MRI. Following surgery, the relative percentages of viable tumor and therapy-related changes observed on histopathology were quantified. Patients were categorized as TP if viable tumor represented ≥ 50% of the specimen, mixed TP if &lt; 50% and &gt; 10%, and PsP if ≤ 10%. SUVmax, SUVpeak, and 50% threshold SUVmean were calculated and normalized to contralateral brain, pituitary gland, and superior sagittal sinus (SSS). The least absolute shrinkage and selection operator (LASSO) was used to determine the variables most predictive of tumor percentage. The strength of association between the primary outcome and selected variables was assessed by Pearson’s or Point-biserial correlation.

Results

18 patients with TP, 4 with mixed TP-PsP, and 8 with PsP were included. There was a positive correlation between 50% threshold SUV mean measured from PET images acquired 50-60 minutes post-injection and rCBVmax by MRI and tumor percentage by histology (r= 0.56; p= 0.004 and r=0.50; p=0.012 respectively). 40-50 minutes SUVmax (OR=1.78 rpb=0.51) and rCBVmax (OR=1.64, rpb=0.48) were positively correlated with tumor TP/mixed TP group. Patients who demonstrated TP/mixed TP-PsP had significantly higher 40-50 minutes SUVmax compared to patients with histological PsP (6.71±2.03 vs 3.93±1.63; p=0.012). 40-50 minutes SUVmax cut-off of 4.46 provided 90% sensitivity and 80% specificity for differentiation of TP/mixed TP-PsP from PsP (AUC=0.88). Combining a 40-50 minutes SUVmax cut-off of 4.46 and an rCBVmax cut-off of 3.67 provided 100% sensitivity and 100% specificity for differentiating TP/mixed TP-PsP from PsP (AUC=1). Patients who demonstrated TP had a significantly higher 40-50 minutes SUVmax compared to patients with histological PsP (6.99±2.06 vs 3.93±1.63; p=0.008). A 40-50 minutes SUVmax cut-off of 4.66 provided 94% sensitivity and 80% specificity for differentiation of TP from PsP (AUC=0.89).

Conclusion

18F-Fluciclovine PET uptake is positively correlated with viable tumor quantification on histology and can accurately differentiate PsP from TP in patients with GBM. Further independent studies are required to cross-validate these promising early results.

Dissemination of OXA-48- and NDM-1-Producing Enterobacterales Isolates in an Algerian Hospital

Multidrug-resistant (MDR) Enterobacterales remain an increasing problem in Algeria, notably due to the emergence of carbapenemase producers. We investigated the molecular characteristics of carbapenem-resistant Enterobacterales isolates recovered from outpatients and inpatients in Eastern Algeria. Non-repetitive Enterobacterales with reduced susceptibility to carbapenems were consecutively collected from clinical specimens in Annaba University Hospital (Algeria) between April 2016 and December 2018. Isolates were characterized with regard to antibiotic resistance, resistome and virulome content, clonality, and plasmid support. Of the 168 isolates analyzed, 29 (17.3%) were carbapenemase producers and identified as K. pneumoniae (n = 23), E. coli (n = 5), and E. cloacae (n = 1). bla_OXA-48 was the most prevalent carbapenemase-encoding gene (n = 26/29), followed by bla_NDM-1 gene (n = 3/29). K. pneumoniae isolates harbored some virulence traits (entB, ugeF, ureA, mrkD, fimH), whereas E. coli had a commensal origin (E, A, and B1). Clonality analysis revealed clonal expansions of ST101 K. pneumoniae and ST758 E. coli. Plasmid analysis showed a large diversity of incompatibility groups, with a predominance of IncM (n = 26, 89.7%). A global dissemination of OXA-48-producing Enterobacterales in the Algerian hospital but also the detection of NDM-1-producing E. coli in community settings were observed. The importance of this diffusion must be absolutely investigated and controlled.

Alternative Approaches for the Management of Diabetic Foot Ulcers

Diabetic foot ulcers (DFU) represent a growing public health problem. The emergence of multidrug-resistant (MDR) bacteria is a complication due to the difficulties in distinguishing between infection and colonization in DFU. Another problem lies in biofilm formation on the skin surface of DFU. Biofilm is an important pathophysiology step in DFU and may contribute to healing delays. Both MDR bacteria and biofilm producing microorganism create hostile conditions to antibiotic action that lead to chronicity of the wound, followed by infection and, in the worst scenario, lower limb amputation. In this context, alternative approaches to antibiotics for the management of DFU would be very welcome. In this review, we discuss current knowledge on biofilm in DFU and we focus on some new alternative solutions for the management of these wounds, such as antibiofilm approaches that could prevent the establishment of microbial biofilms and wound chronicity. These innovative therapeutic strategies could replace or complement the classical strategy for the management of DFU to improve the healing process.

Accuracy of gradient diffusion method for susceptibility testing of dalbavancin and comparators

OBJECTIVES

This multicenter study aimed to assess the performances of gradient diffusion (GD) method in comparison to broth microdilution (BMD) method for susceptibility testing of dalbavancin, daptomycin, vancomycin, and teicoplanin.

METHODS

Minimum Inhibitory Concentrations (MICs) were retrospectively determined concomitantly by BMD and GD methods, for 93 staphylococci and enterococci isolated from clinical samples. BMD was considered as the gold standard. Essential (EA) and categorical agreements (CA) were calculated. Discordant categorical results were categorized as major (ME) and very major errors (VME).

RESULTS

EA and CA were 95.7% and 96.8%, 82.8% and 100%, 97.8% and 96.8%, and 94.6% and 95.7% for dalbavancin, daptomycin, vancomycin, and teicoplanin respectively. Concerning dalbavancin, 3 ME without any VME were observed and discrepancies were low (≤ to 2 two-fold dilutions) between both methods. VME were noted in 1 and 3 cases for vancomycin and teicoplanin, respectively, and resulted from 1 two-fold dilution discrepancy in each case. EA was lower for daptomycin. When they were discrepant, BMD MICs were systematically higher than GD ones. Nevertheless, no categorical discrepancy was noted.

CONCLUSIONS

GD appears as an acceptable and convenient alternative for dalbavancin, vancomycin, and teicoplanin MICs determination. Our study also emphasizes how achieving accurate daptomycin MICs remains challenging.

In vitro activity of dalbavancin against Gram-positive bacteria isolated from diabetic foot osteomyelitis

BACKGROUND

Diabetic foot infections (DFIs) represent a serious threat to public health because of their frequency and the severity of their consequences, i.e. osteomyelitis and amputation. The management of diabetic foot osteomyelitis (DFOM) requires prolonged antibiotic therapy. In Western countries, Gram-positive bacteria are the most commonly encountered pathogens.

OBJECTIVES

This study evaluated the in vitro activity of dalbavancin, a novel lipoglycopeptide with extended half-life, recently marketed in Europe for acute bacterial skin and skin structure infections, on a panel of Gram-positive bacteria responsible for DFOM.

METHODS

Dalbavancin activity was evaluated against a panel of Gram-positive bacterial strains isolated from bone biopsies performed by a trained surgeon among patients with suspected DFOM. MICs were determined using MIC Test Strips (Liofilchem) and confirmed with the EUCAST broth microdilution method. Three other antimicrobial agents (vancomycin, teicoplanin and ceftobiprole) were used as comparators.

RESULTS

Dalbavancin showed excellent activity against all Gram-positive bacterial strains tested, including one teicoplanin-resistant Staphylococcus epidermidis isolate. With MIC50 and MIC90 values of 0.047 and 0.094 mg/L, respectively, dalbavancin showed the most potent in vitro activity among antimicrobial agents tested.

CONCLUSIONS

With its efficacy, good tolerability and unique pharmacokinetic properties, dalbavancin appears to be a promising treatment for DFOM involving Gram-positive bacteria.

Escherichia coli Isolated from Diabetic Foot Osteomyelitis: Clonal Diversity, Resistance Profile, Virulence Potential, and Genome Adaptation

This study assessed the clonal diversity, the resistance profile and the virulence potential of Escherichia coli strains isolated from diabetic foot infection (DFI) and diabetic foot osteomyelitis (DFOM). A retrospective single-centre study was conducted on patients diagnosed with E. coli isolated from deep DFI and DFOM at Clinique du Pied Diabétique Gard-Occitanie (France) over a two-year period. Phylogenetic backgrounds, virulence factors (VFs) and antibiotic resistance profiles were determined. Whole-genome analysis of E. coli strains isolated from same patients at different periods were performed. From the two-years study period, 35 E. coli strains isolated from 33 patients were analysed; 73% were isolated from DFOM. The majority of the strains belonged to the virulent B2 and D phylogenetic groups (82%). These isolates exhibited a significant higher average of VFs number than strains belonging to other groups (p < 0.001). papG2 gene was significantly more detected in strains belonging to B2 phylogroup isolated from DFI compared to DFOM (p = 0.003). The most prevalent antibiotic resistance pattern was observed for ampicillin (82%), cotrimoxazole (45%), and ciprofloxacin (33%). The genome analysis of strains isolated at two periods in DFOM showed a decrease of the genome size, and this decrease was more important for the strain isolated at nine months (vs. four months). A shared mutation on the putative acyl-CoA dehydrogenase-encoding gene aidB was observed on both strains. E. coli isolates from DFOM were highly genetically diverse with different pathogenicity traits. Their adaptation in the bone structure could require genome reduction and some important modifications in the balance virulence/resistance of the bacteria.

Colistin-Resistant Enterobacterales Isolated from Chicken Meat in Western Algeria

Aim: In Algeria, colistin is used as a metaphylactic treatment in the poultry industry for the treatment of Gram-negative gastrointestinal infections and also as a feed additive to promote animal growth. The aim of this study was to investigate the importance and genetic characteristics of colistin-resistant Enterobacterales from chicken meat in Western Algeria. Results: A total of 181 samples of chicken meat were collected from three poultry farms across three provinces in Western Algeria. The presence of colistin-resistant Enterobacterales isolates was screened on selective media. Resistance and virulence profiles were characterised by PCR and sequencing. The clonal relatedness of the different mcr positive isolates was studied using repetitive sequence-based PCR (Rep-PCR) and multilocus sequence typing. Transferability and characteristics of plasmids harboring mcr-1 positive gene were performed using conjugation, PCR-based replicon typing, and whole-genome sequencing. A total of 22 isolates with acquired colistin resistance were identified giving an overall prevalence of 12.2% (22/181): 17 Escherichia coli (predominantly ST224 [n = 4, 23.5%]) and 5 Klebsiella pneumoniae (ST17 [n = 2, 40%], ST646 [n = 2, 40%], and ST944 [n = 1, 20%]). mcr-1 gene was exclusively found in 11 E. coli (prevalence of 6.1% [11/181]) and was associated with IncFV (n = 7) and IncFIIK (n = 4) plasmids. All the isolates had a commensal origin (n = 11). One isolate harbored virulence profile, a high colistin resistance (minimum inhibitory concentration = 96 mg/L), with some new mutations in the chromosomic colistin-resistant genes and different pathogenicity islands typically identified in uropathogenic E. coli. Conclusions: This study reports the diffusion of mcr-1 producing Enterobacterales from chicken meat in Western Algeria. This represents a worrisome situation needing continuous monitoring.

Evaluation of Two Methods for the Detection of Third Generation Cephalosporins Resistant Enterobacterales Directly From Positive Blood Cultures

Due to the importance of a rapid determination of patients infected by multidrug resistant bacteria, we evaluated two rapid diagnostic tests for the detection of third-generation cephalosporins (3GC)-resistant Enterobacterales directly from positive blood cultures within 1 h: BL-RED^TM (electrochemical method) and β-LACTA^TM test (chromogenic method). A panel of 150 clinical strains characterized for their resistance profiles (e.g., penicillinases, extended-spectrum beta-lactamases (ESBLs), overproduction of cephalosporinase, carbapenemases, impermeability) was tested. Approximately 100 CFU of each isolate was spiked into sterile blood culture bottles and incubated in a BD BACTEC^TM FX automated system (Becton Dickinson, USA). Positive blood cultures were examined to parallel testing using the BL-RED^TM and β-LACTA^TM tests and conventional susceptibility method (disc diffusion following EUCAST recommendations). For all phenotypes combined, the sensitivity, specificity, positive predictive value, and negative predictive value in the detection of 3GC resistance were, respectively (i) with BL-RED^TM: 45.7, 100, 100, and 54.2% and (ii) with β-LACTA^TM test: 52.2, 100, 100, and 56.9%. The positivity of tests allows to adapt antibiotic treatment whereas the negative result requires other tests. Moreover, these tests detect most Ambler class A-producing Enterobacterales (KPC, ESBL, extended-spectrum OXY) with sensitivities and specificities of 87.5 and 99% for BL-RED^TM, respectively and both 100% for β-LACTA^TM test (47/47 isolates). These two rapid tests failed to detect AmpC overexpressed (sensitivities of 2.7% for BL-RED^TM and 0% for β-LACTA^TM test) and Ambler class B-producing Enterobacterales (sensitivities of 40% for both tests) notably strains without ESBLs associated (sensitivities of 0% for both tests). BL-RED^TM and β-LACTA^TM tests are easy-to-use and mainly attractive when a positive result is obtained notably to detect most of the Ambler class A-producing Enterobacterales in <1 h after the positivity of the blood culture, allowing a rapid adaptation of the antibiotic therapy in patients.

Spread of OXA-48 and NDM-1-Producing Klebsiella pneumoniae ST48 and ST101 in Chicken Meat in Western Algeria

Aim: We investigated the prevalence of carbapenemase-producing Enterobacteriaceae (CPE) in chicken meat in Western Algeria in 2017. Results: From February to July 2017, samples of chicken meat from three poultry farms in Western Algeria were screened for the presence of CPE. Strains were characterized with regard to antibiotic resistance, β-lactamase content, Plasmid-mediated quinolone resistance, sulfonamide resistance genes, clonality (repetitive sequence-based profiles and multilocus sequence typing) and virulence traits. Of 181 samples analyzed, 29 (16.0%) carbapenemase-producing Klebsiella pneumoniae were detected. Twenty-three OXA-48-producers (79.3%) and six (20.7%) New Delhi metallo (NDM)-1-producers were observed. Clonality analysis showed three distinct lineages and clonal expansions of the OXA-48-producing K. pneumoniae ST48 and the NDM-1-producing K. pneumoniae ST101. These isolates harbored fimH, ureA, mrkD, entB, uge, and wabG. Neither capsular serotype genes nor hypermucoviscous phenotype were detected. Plasmid analysis confirmed that all these isolates harbored the transferable IncL and IncFIIK plasmids. Conclusions: This study reports the spread of OXA-48 and NDM-1-producing K. pneumoniae ST48 and ST101 in chicken meat in Western Algeria and demonstrates that food represents a reservoir of the carbapenemases encoding genes.

Performance of the Accelerate Pheno™ system for identification and antimicrobial susceptibility testing of a panel of multidrug-resistant Gram-negative bacilli directly from positive blood cultures

Objectives

To evaluate the performance of the Accelerate Pheno™ system for the identification and antimicrobial susceptibility testing (AST) of a panel of Gram-negative bacilli (GNB) with different resistance profiles (e.g. penicillinases, ESBLs, cephalosporinase overproduction, carbapenemases, impermeability) directly from positive blood cultures in <7 h.

Methods

A panel of 105 clinical strains previously characterized for the presence of β-lactamase-encoding genes was tested. Approximately 100 cfu of each isolate was inoculated into sterile blood culture bottles and incubated in a BD BACTEC™ FX automated system (Becton Dickinson, USA). Positive blood cultures were subjected to parallel testing using the Accelerate Pheno™ system and conventional culture methods [identification of isolated colonies by MALDI-TOF and VITEK® 2 system (bioMérieux, France), and AST by disc diffusion and Etest following EUCAST recommendations].

Results

The overall identification agreement between the Accelerate Pheno™ system and conventional culture methods was 100% (105/105). The overall categorical agreement between the system and culture-based AST was 94.9% (1169/1232), with rates for minor errors of 4.1% (51/1232), major errors 0.3% (4/1232) and very major errors 0.7% (8/1232). The Accelerate Pheno™ system produced AST results indicative of third-generation cephalosporinases (26/26) and carbapenem-resistant strains (52/55).

Conclusions

The Accelerate Pheno™ system is an accurate, sensitive and easy-to-use test for the rapid identification and AST of MDR GNB in bloodstream infections. Given the burden of multidrug resistance, its implementation in the microbiology laboratory could be a useful tool for prompt management of sepsis.

Distribution of Toxinogenic Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus from Different Ecological Niches in Algeria

The diffusion of Panton-Valentine leukocidin (PVL)-positive methicillin-resistant S. aureus (MRSA) is a health problem in Algeria. The objectives of the study were to investigate the global distribution of methicillin-susceptible S. aureus (MSSA) and MRSA isolates in different ecological niches in this country. In total, 2246 samples were collected from humans, livestock, wild animals, pets, food products and the aquatic environment, from 12 Algerian provinces. A total of 312 S. aureus were detected from 2446 samples (12.7%) in the screened niches. We observed the emergence of toxinogenic S. aureus representing 41% of the isolates. Among them, we noted the diffusion of ST80-IV CA-MRSA PVL + strains isolated in human, animals, and food and genetic diversity of MSSA PVL + isolates. This study suggests an alarming dissemination of MRSA-ST80 PVL + in both human and extra-human sources in Algeria. Moreover, MSSA may become a permanent reservoir of the PVL genes necessary for human infections.

Performance of a new in-house medium Carba MTL-broth for the rapid detection of carbapenemase-producing Enterobacteriaceae

INTRODUCTION

The spread of carbapenemase-producing Enterobacteriaceae (CPE) represents a major public health issue. Methods allowing rapid detection of carbapenemases in developing countries are therefore urgently needed. In the current study, we developed a new in-house medium for the rapid detection of CPE isolates, especially OXA-48 producers.

METHODOLOGY

A panel of 144 clinical strains previously characterized was tested on in-house Carba MTL-broth medium using four different concentrations of ertapenem (0.5 to 2 mg/L), and compared to chromID® OXA-48 and chromID® CARBA (BioMérieux) media.

RESULTS

Comparative evaluation of the Carba MTL-broth with chromID® OXA-48 and chromID® CARBA showed that chromID® OXA-48 and Carba MTL-broth had the highest sensitivity for detection of OXA-48 producers (93.9% and 100%, respectively) comparatively to chromID® CARBA (21.2%). The chromID® OXA-48 had the highest specificity (100%), as compared to the Carba MTL-broth (65.5%) and chromID® CARBA (84.4%) for the detection of OXA-48 producers.

CONCLUSIONS

The in-house Carba MTL-broth developed in this study is sensitive, inexpensive, an easy-to-use phenotypic method for the detection of OXA-48-producing enterobacteria. Given the burden of pan-drug resistance, its implementation in the microbiology laboratory of developing countries could be a useful tool for rapid detection of these bacteria.

Surgical site infection after hip replacement due to a novel Peptoniphilus species, provisionally named 'Peptoniphilus nemausus' sp. nov

We report a case of surgical site infection after total hip prosthesis replacement due to an ofloxacin-resistant Peptoniphilus isolate belonging to an unknown species for which the name 'Peptoniphilus nemausus' sp. nov. is proposed. Follow-up was favourable under clindamycin and rifampin for 3 months in this patient whom had a Proteus mirabilis infection treated by fluoroquinolone.

Successful implementation of infection control measure in a neonatal intensive care unit to combat the spread of pathogenic multidrug resistant Staphylococcus capitis

Background

Once present in a neonatal intensive care unit (NICU), multidrug resistant Staphylococcus capitis NRCS-A is able to settle and diffuse.

Objective

The objective of this study was to evaluate the impact of infection control (IC) interventions to reduce the spread of Staphylococcus capitis NRCS-A in a NICU.

Methods

Between December 2012 and December 2017, all patients presenting positive sampling (blood, skin or catheter) to S. capitis were included, and clinical data were recorded from electronic clinical charts. The IC team has continually implemented measures of control infections (hand hygiene, standard precautions, patient contact isolation and disinfection of the inanimate environment). From May 2015, a steam cleaner was implemented in the cleaning procedure instead of disinfectant to disinfect heating tables and incubators. Four periods were determined: Period 1 (P1) before steam cleaner acquisition; Period 2 (P2) after implementation steam cleaner; Period 3 (P3) when the steam cleaner had broken down, and Period 4 (P4) when the steam cleaner was functional again. The consumption of antibiotics and the epidemiology of infections inside the NICU were investigated during the study period.

Results

During the studied period, 37 infants were infected or colonized by S. capitis. The incidences of infection or colonization by S. capitis were P1 = 1.04‰, P2 = 0.55‰, P3 = 3.95 ‰ and P4 = 0‰ and were significantly different between P1-P3 and P2-P4 (p < 0.001). During the different periods, antibiotics consumption and bacterial epidemiology of the ward were stable.

Conclusions

The use of steam vapor system was associated with a significantly decreased incidence of S. capitis NRCS-A infection or colonization and could constitute an effective and safe procedure to control and eradicate its diffusion inside NICUs.

Abstract PD4-11: [18F]Fluciclovine PET tracks cellular glutamine pool size in breast cancer and changes in response to metabolic inhibition

Background: Some forms of triple negative breast cancer (TNBC) rely on glutamine (Gln) metabolism for survival and growth (1), therefore, targeting this metabolic pathway provides a viable strategy for managing TNBC. Drugs that inhibit glutaminase (GLS), a key enzyme of glutaminolysis, are being developed (1,2). [18F]Fluciclovine is a PET imaging agent that enters/exits cells via glutamine transporters and undergoes minimal metabolism. Therefore, we hypothesize, that akin to our prior work with [18F]fluoroglutamine (3), the distribution volume (VT) of fluciclovine obtained from dynamic PET can be used to estimate the cellular glutamine level (pool size) and to mark the effect of pharmacological inhibitors of tumor glutaminase (GLS). We tested this hypothesis in human TNBC and ER+ breast cancer xenograft exhibiting a high and low GLS activity, respectively.

Methods: To make [18F]fluciclovine preparation suitable for mouse imaging, citrate in the formulation was removed and replaced with PBS by eluting through a column (Bio-Rad). Cellular uptake was performed in the presence and absence of Gln transporter inhibitors and GLS inhibitor. In vivo dynamic PET imaging were performed on mice bearing HCC1806 (TNBC) and MCF-7 (ER+ BC) xenografts. Dynamic PET images were analyzed by Logan Plot (PMOD) to estimate VT.

Results: Cellular uptake of [18F]fluciclovine in HCC1806 and MCF-7 cells were sensitively inhibited by cold glutamine (Gln) and GPNA (a pharmacologic inhibitor of ASCT-2), confirming that the uptake is mediated by Gln transporters. The peak uptake in MCF-7 cells was 5-fold higher than HCC1806. In mouse models, VT from in vivo [18F]Fluciclovine PET in MCF-7 tumor is 1.4-fold of HCC1806. These data are consistent with a higher cellular Gln pool size in MCF-7 as the result of its lower GLS activity. After inhibition of tumor GLS activity, VT of [18F]fluciclovine in HCC-1806 tumors was increased by 56% from baseline values (n=2), whereas VT in MCF-7 tumors decreased 1% after treatment (n=2). Only a small change of FDG PET signal (5% decrease, n=5) was detected in TNBC tumors after GLS inhibitor treatment.

Discussions: These data suggest that VT obtained from [18F]fluciclovine PET is sensitive to changes of the Gln pool size induced by GLS inhibition whereas FDG PET is not. Since the Gln pool size is inversely related to the GLS activity, increased VT is consistent with the increased intracellular Gln level when metabolic conversion of Gln to glutamate by GLS is inhibited. Our results suggest that [18F]fluciclovine, an imaging agent approved for prostate cancer imaging, may be useful for assessing glutamine pool size in breast cancer and changes in response to GLS inhibition

Support: R21CA198563, R01CA211337, and Komen SAC130060. We thank Blue Earth Diagnostics for supplies of [18F]fluciclovine.

1.Gross MI, Demo SD, Dennison JB, et al. Mol Cancer Ther 2014;13(4):890-901.

2.Le A, Lane AN, Hamaker M, et al. Cell Metab 2012;15(1):110-21.

3.Zhou R, Pantel AR, Li S, et al. Cancer Res 2017;77(6):1476-84.

Citation Format: Cao J, Choi H, Pantel A, Kranseler D, Lee H, Mankoff D, Zhou R. [18F]Fluciclovine PET tracks cellular glutamine pool size in breast cancer and changes in response to metabolic inhibition [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-11.

Relationship Between Different Resistance Mechanisms and Virulence in Acinetobacter baumannii

Aim: This study analyzed the virulence of several Acinetobacter baumannii strains expressing different resistance mechanisms using the Caenorhabditis elegans infection model. Results: Strains susceptible/resistant to carbapenems (presenting class D (OXA-23, OXA-24), class B metallo-β-lactamase (MBL) (NDM-1), penicillin binding protein (PBP) altered and decreased expression of Omp 33-36 kDa) and isogenic A. baumannii strains susceptible/resistant to colistin (presenting loss of lipopolysaccharide (LPS) and pmrA mutations) were included to evaluate the virulence using the C. elegans infection model. The nematode killing assay, bacterial ingestion in worms, and bacterial lawn avoidance assay were performed with the Fer-15 mutant line. A. baumannii strains generally presented low virulence, showing no difference between carbapenem-resistant strains (expressing class D, MBLs, or altered PBP) and their isogenic susceptible strains. In contrast, the absence of the Omp 33-36 kDa protein in the knockout was associated with a decrease of virulence, and a significant difference was observed between colistin-resistant mutants and their susceptible counterpart when the mechanism of resistance was associated with the loss of LPS but not with its modification. Conclusions: Resistance to carbapenems in A. baumannii associated with the production of OXA-type or NDM-type enzymes does not seem to affect their virulence in the C. elegans infection model. In contrast, the presence of Omp 33-36 kDa, and high level resistance to colistin related with the loss of LPS, might contribute with the virulence profile in A. baumannii.

Carbapenemase-producing Enterobacteriaceae among pregnant women and newborns in Algeria: Prevalence, molecular characterization, maternal-neonatal transmission, and risk factors for carriage

The diffusion of carbapenemase-producing Enterobacteriaceae (CPE) represents a worldwide public health problem. This study revealed that the prevalence of OXA-48-producing enterobacteria was 4.6% (19/414) and 1.6% (7/422) in mothers and newborns, respectively, from 2 maternity units in Algeria. Previous hospital admission was an independent factor associated with an increased risk of CPE carriage in the mothers (P = .021). The low birth weight was significantly associated with this carriage in the newborns (P = .008). The screening of these bacteria is essential to prevent the dissemination of CPE.

First molecular characterization of related cases of healthcare-associated infections involving multidrug-resistant Enterococcus faecium vanA in Algeria

Purpose

Vancomycin-resistant Enterococcus (VRE) faecium (VREfm) are highly resistant bacteria emerging worldwide and rarely studied using molecular tools in Algeria since their first report in 2006. The aim of the study was to investigate healthcare-associated infections (HAIs) involving the first VRE in Batna University Hospital, Algeria, and characterize isolates using molecular tools.

Patients and methods

Medical charts were reviewed for patients with VREfm. van genes were detected by multiplex polymerase chain reaction (PCR), and strains were characterized by automated repetitive sequence-based PCR (rep-PCR), multiplex rep-PCR, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST).

Results

During a 6-month period, VREfm infections occurred in four patients hospitalized in three wards. The four isolates were E. faecium vanA belonging to the hospital-adapted clonal complex 17. PCR-based methods did not discriminate the isolates but MLST and PFGE delineated a subgroup of three VREfm of identical pulsotype and sequence type (ST) 80 (yet identified for five isolates in the international PubMLST database) while the fourth isolate was of ST789 (not previously identified for a VREfm) and displayed an unrelated pulsotype. The three genotypically related isolates were recovered in patients who underwent surgery in the same department, suggesting an outbreak for which the source and route of transmission remained unidentified.

Conclusion

This first molecular epidemiology study of VRE in Algeria was useful in delimiting an outbreak involving three of the four HAI cases and revealed rarely encountered genotypes. Considering the threat and burden of VRE infections worldwide, particularly in the USA, and the late emergence in Algeria, our study supports the urgent need for improved and early adequate infection control measures to avoid VRE spread in North African hospitals.

OXA-48-like carbapenemases producing Enterobacteriaceae in different niches

The emergence of carbapenem-resistant enterobacterial species poses a serious threat to public health worldwide. OXA-48-type carbapenem-hydrolyzing class D β-lactamases are widely distributed among Enterobacteriaceae, with significant geographical differences. To date, 11 OXA-48-like variants have been identified, with classical OXA-48 being the most widespread. These enzymes show high-level hydrolytic activity against penicillins and low-level hydrolysis towards carbapenems. Since the first description of the OXA-48 carbapenemase in Turkey, bacterial strains producing the enzyme have been extensively reported in nosocomial and community outbreaks in many parts of the word, particularly in the Mediterranean area and European countries. The rapid spread of Enterobacteriaceae producing OXA-48-like enzymes in different ecosystems has become a serious issue recently. The number of reservoirs for such organisms is increasing, not only in hospitals, but also in the community, among animals (e.g., livestock, companion animals, and wildlife) and in the environment. This review aims to summarize the main characteristics of the OXA-48-type carbapenemases, covering genetic and enzymatic traits, their epidemiology, clonality and associated genes, correlation with extended-spectrum β-lactamases (ESBLs) or plasmidic AmpC (pAmpC) in different bacterial species worldwide.

High Prevalence of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Wild Fish from the Mediterranean Sea in Algeria

AIM

We investigated the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae among wild fish from the coast of Bejaia (Algeria) in the Mediterranean Sea.

RESULTS

From March 2012 to August 2013, gut and gill samples of wild fish were screened for the presence of ESBL-producing Enterobacteriaceae. Strains were characterized with regard to antibiotic resistance, β-lactamase content, plasmid-mediated quinolone resistance, aminoglycoside resistance genes, and clonality (repetitive sequence-based polymerase chain reaction profiles and multilocus sequence typing). Virulence traits were performed for Escherichia coli and Klebsiella pneumoniae isolates. Of the 300 fish studied, 64 (21.3%) isolates were screened as positive for ESBL producing by the double-disc method. The isolates corresponded to E. coli, K. pneumoniae, Enterobacter cloacae, Morganella morganii, Citrobacter freundii, and Proteus vulgaris. A predominance of bla_CTX-M gene was observed with a prevalence of 60.5% (n = 46). Furthermore, our study describes the association of important coresistance and virulence factors in E. coli and K. pneumoniae. Twelve of the ESBL producers carried genes of the qnr family and oqxAB gene and six carried the aac(6')-Ib-cr gene.

CONCLUSIONS

Our results highlight for the first time the diffusion of multidrug-resistant Enterobacteriaceae isolates carrying resistance and virulence genes in fish from the Mediterranean Sea in Algeria.

First report of cavitary pneumonia due to community-acquired Acinetobacter pittii, study of virulence and overview of pathogenesis and treatment

Background

Acinetobacter pittii is a nosocomial pathogen rarely involved in community-acquired infections. We report for the first time that A. pittii can be responsible for cavitary community-acquired pneumonia and study its virulence, and discuss its pathogenesis and treatment options.

Case presentation

A 45-year-old woman with a history of smoking and systemic lupus was admitted to Nimes University Hospital (France) with coughing and sputum lasting for three weeks. Thoracic CT scanner showed cavitary pneumonia. Broncho-alveolar lavage cultures found community-acquired Acinetobacter calcoaceticus-baumannii complex. The clinical outcome was favourable after twenty-one days of antimicrobial treatment by piperacillin/tazobactam and amikacin then cefepime. Multilocus sequence typing (MLST) analyses identified an A. pittii ST249. Despite the atypical clinical presentation with an unexpected partial destruction of lung parenchyma, we found very low virulence potential of the A. pittii strain with nematode killing assays and biofilm formation test. The median time required to kill 50% of the nematodes was 7 ± 0.3 days for A. pittii ST249, 7 ± 0.2 days for A. baumanii NAB ST2 and 8 ± 0.2 days for E. coli OP50, (p > 0,05). A. pittii ST249 showed significantly slower biofilm formation than A. baumanii NAB ST2: BFI = 8.83 ± 0.59 vs 3.93 ± 0.27 at 2 h (p < 0.0001), BFI = 6.3 ± 0.17 vs 1.87 ± 0.12 at 3 h (p < 0.0001) and BFI = 3.67 ± 0.41 vs 1.7 ± 0.06 after 4 h of incubation (p < 0.01).

Conclusions

Community-acquired A. pittii should be considered as possible cause of sub-acute cavitary pneumonia particularly in a smoking and/or immunocompromised patient despite its low virulence potential.

Persisting transmission of carbapenemase-producing Klebsiella pneumoniae due to an environmental reservoir in a university hospital, France, 2012 to 2014

In France, the proportion of episodes of carbapenemase-producing Enterobacteriaceae (CPE) with no recent stay or hospitalisation abroad is increasing. In this study, we investigate epidemiological links between apparently unrelated cases of OXA-48-producing Klebsiella pneumoniae (Kp OXA-48) colonisation or infection. We genotyped detected organisms by repetitive sequence-based PCR, and used a dynamic registry of cases and contacts to cross-reference patients' hospital stays. Between 1 November 2012 and 28 February 2014, 23 Kp OXA-48 cases were detected in a university hospital in Montpellier, of which 15 were involved in three outbreaks: outbreaks I and II occurred in November 2012 and outbreak III in October 2013. Molecular comparison of bacterial strains revealed clonal identity between cases involved in outbreaks II and III and four single cases. Cross-referencing of hospital stays revealed that these single cases and the index case of outbreak III had occupied the same room. Active case search among former occupants of that room found an additional Kp OXA-48 carrier. A clonal strain was isolated from the sink of that room. The epidemiological link between the contaminated room and outbreak II remained undetected. This study is a reminder that environmental reservoirs should be considered as a source of CPE transmission.

Development of an algorithm for phenotypic screening of carbapenemase-producing Enterobacteriaceae in the routine laboratory

Background

Carbapenemase-producing Enterobacteriaceae (CPE) are difficult to identify among carbapenem non-susceptible Enterobacteriaceae (NSE). We designed phenotypic strategies giving priority to high sensitivity for screening putative CPE before further testing.

Methods

Presence of carbapenemase-encoding genes in ertapenem NSE (MIC > 0.5 mg/l) consecutively isolated in 80 French laboratories between November 2011 and April 2012 was determined by the Check-MDR-CT103 array method. Using the Mueller-Hinton (MH) disk diffusion method, clinical diameter breakpoints of carbapenems other than ertapenem, piperazicillin+tazobactam, ticarcillin+clavulanate and cefepime as well as diameter cut-offs for these antibiotics and temocillin were evaluated alone or combined to determine their performances (sensitivity, specificity, positive and negative likelihood ratios) for identifying putative CPE among these ertapenem-NSE isolates. To increase the screening specificity, these antibiotics were also tested on cloxacillin-containing MH when carbapenem NSE isolates belonged to species producing chromosomal cephalosporinase (AmpC) but Escherichia coli.

Results

Out of the 349 ertapenem NSE, 52 (14.9%) were CPE, including 39 producing OXA-48 group carbapenemase, eight KPC and five MBL. A screening strategy based on the following diameter cut offs, ticarcillin+clavulanate <15 mm, temocillin <15 mm, meropenem or imipenem <22 mm, and cefepime <26 mm, showed 100% sensitivity and 68.1% specificity with the better likelihood ratios combination. The specificity increased when a diameter cut-off <32 mm for imipenem (76.1%) or meropenem (78.8%) further tested on cloxacillin-containing MH was added to the previous strategy for AmpC-producing isolates.

Conclusion

The proposed strategies that allowed for increasing the likelihood of CPE among ertapenem-NSE isolates should be considered as a surrogate for carbapenemase production before further CPE confirmatory testing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2174-y) contains supplementary material, which is available to authorized users.

Pyomelanin-producing Pseudomonas aeruginosa selected during chronic infections have a large chromosomal deletion which confers resistance to pyocins

When bacterial lineages make the transition from free-living to permanent association with hosts, they can undergo massive gene losses, for which the selective forces within host tissues are unknown. We identified here melanogenic clinical isolates of Pseudomonas aeruginosa with large chromosomal deletions (66 to 270 kbp) and characterized them to investigate how they were selected. When compared with their wild-type parents, melanogenic mutants (i) exhibited a lower fitness in growth conditions found in human tissues, such as hyperosmolarity and presence of aminoglycoside antibiotics, (ii) narrowed their metabolic spectrum with a growth disadvantage with particular carbon sources, including aromatic amino acids and acyclic terpenes, suggesting a reduction of metabolic flexibility. Despite an impaired fitness in rich media, melanogenic mutants can inhibit their wild-type parents and compete with them in coculture. Surprisingly, melanogenic mutants became highly resistant to two intraspecific toxins, the S-pyocins AP41 and S1. Our results suggest that pyocins produced within a population of infecting P. aeruginosa may have selected for bacterial mutants that underwent massive gene losses and that were adapted to the life in diverse bacterial communities in the human host. Intraspecific interactions may therefore be an important factor driving the continuing evolution of pathogens during host infections.

Environmental persistence of OXA-48-producing Klebsiella pneumoniae in a French intensive care unit

The spread of carbapenemase-producing Gram-negative rods is an emerging global problem. This study describes the epidemiologic features of an outbreak caused by an environmental reservoir of OXA-48-producing Klebsiella pneumoniae caused by persistence of the bacteria during 20 months in an intensive care unit in France. This report emphasizes the importance of early environmental screening to interrupt the transmission of carbapenemase-producingEnterobacteriaceae.

Carbapenemase-producing Enterobacteriaceae: use of a dynamic registry of cases and contacts for outbreak management

BACKGROUND

The emergence and spread of carbapenemase-producing Enterobacteriaceae (CPE) have become a major public health problem. Control and prevention of CPE infections hinge on isolation precautions for carriers and active screening and follow-up of contacts.

AIM

To implement an open registry of cases and contacts for acute outbreak management, long-term data collection and epidemiological investigation.

METHODS

All cases, defined as patients (infected or colonized) with a CPE-positive culture during their hospitalization, and contacts (e.g. patients cared for by the same healthcare team as a case) were registered in an ongoing database. Hospital stays were cross-referenced for every new entry and epidemiological links (e.g. shared contacts) investigated. All cases and contacts not cleared by complete screening were registered on an active list.

FINDINGS

Between October 2012 and November 2014, we registered 30 cases and 1268 contacts, among which 24 were linked to two or three separate cases. Only 6.5% of contacts fulfilled complete screening with three rectal swabs, and 1145 contacts are still registered on the active surveillance list. Two outbreaks (12 and nine cases) occurred nine months apart. Cross-referencing of hospital stays using the registry revealed epidemiological links between seemingly unrelated cases of CPE-positive patients and suggested an environmental source of transmission, which was demonstrated thereafter.

CONCLUSION

We implemented a simple and multi-purpose tool to manage CPE episodes and investigate epidemiological links. Efforts are necessary to improve screening of contact patients who may be occult sources of transmission. A regional registry could be helpful.

Faecal carriage of carbapenemase-producing Gram-negative bacilli in hospital settings in southern France

The emergence of carbapenemase-producing Gram-negative bacilli is a worldwide problem. To date, no study has evaluated the prevalence of faecal carriage of carbapenemase-producing and carbapenem-resistant Gram-negative bacilli (CR GNB) in France. From 1 February to 30 April 2012, we conducted a prospective, multicentre study in three University Hospitals and four General Hospitals in the south of France. The carriage of carbapenemase-producing Enterobacteriaceae (CPE) and other CR GNB was screened by both cultivation on chromID® CARBA and chromID® OXA-48 media (bioMérieux) and molecular tools [multiplex polymerase chain reaction (PCR) and NucliSENS EasyQ® KPC (bioMérieux)]. The genetic relationship between isolates was assessed by rep-PCR (DiversiLab, bioMérieux) or multilocus sequence typing (MLST). The prevalences of CR GNB and carbapenemase-producing bacteria were 2.4 % (27/1,135) and 0.4 % (n = 5), respectively. Two strains corresponded to OXA-23-producing Acinetobacter baumannii and belonged to the widespread sequence type (ST) 2/international clone II, whereas one strain was an ST15 OXA-48-producing Klebsiella pneumoniae. Two OXA-48-producers were detected exclusively by PCR. This first French study revealed the very low dissemination of carbapenemase-producing bacteria in patients attending hospitals in southern France during a non-outbreak situation. However, the increasing description of epidemic cases in this area must reinforce the use of hygiene procedures to prevent diffusion of these multidrug-resistant microorganisms.

Molecular epidemiology of OXA-48-producing Klebsiella pneumoniae in France

We characterized 53 OXA-48-producing Klebsiella pneumoniae (OXA-48-Kp) isolated between 2011 and 2013 in 21 French hospitals. All the isolates were genotyped using MLST and PFGE and the population structure of the species was determined by a nucleotide-based analysis of the entire K. pneumoniae MLST database. Most of the OXA-48-Kp isolates also produced CTX-M-15 and remained susceptible to imipenem and meropenem. The isolates were distributed into 20 STs, of which five were dominant (ST15, ST101, ST147, ST395 and ST405). All the OXA-48-Kp clustered in the major clade of K. pneumoniae KpI.

French regional surveillance program of carbapenemase-producing Gram-negative bacilli: results from a 2-year period

In February 2011, the CARB-LR group was created as a sentinel laboratory-based surveillance network to control the emergence of carbapenem-resistant Gram-negative bacilli (CR GNB) in a French Southern Region. We report the epidemiological results of a 2-year study. All the Gram-negative bacilli isolates detected in the different labs (hospital and community settings) of a French Southern Region and with reduced susceptibility to ertapenem and/or imipenem were characterised with regard to antibiotic resistance, bla genes content, repetitive sequence-based polymerase chain reaction (rep-PCR) profiles and multilocus sequence typing (MLST). A total of 221 strains were analysed. Acinetobacter baumannii was the most prevalent carbapenemase-producing bacteria, with a majority of OXA-23 producers (n = 37). One isolate co-produced OXA-23 and OXA-58 enzymes. Klebsiella pneumoniae was the most frequent carbapenemase-producing Enterobacteriaceae (CPE) (OXA-48 producer: n = 29, KPC producer: n = 1), followed by Escherichia coli (OXA-48 producer: n = 8, KPC producer: n = 1) and Enterobacter cloacae (OXA-48 producer, n = 1). One isolate of Pseudomonas aeruginosa produced a VIM-1 carbapenemase. A clonal diversity of carbapenemase-producing K. pneumoniae and E. coli was noted with different MLSTs. On the other hand, almost all OXA-23-producing A. baumannii strains belonged to the widespread ST2/international clone II. The link between the detection of CR GNB and a foreign country was less obvious, suggesting the beginning of a local cross-transmission. The number of CR GNB cases in our French Southern Region has sharply increased very recently due to the diffusion of OXA-48 producers.