Molecularly imprinted polymers for per- and polyfluoroalkyl substances enrichment and detection

Per- and polyfluoroalkyl substances (PFAS) are highly toxic pollutants of significant concern as they are being detected in water, air, fish and soil. They are extremely persistent and accumulate in plant and animal tissues. Traditional methods of detection and removal of these substances use specialised instrumentation and require a trained technical resource for operation. Molecularly imprinted polymers (MIPs), polymeric materials with predetermined selectivity for a target molecule, have recently begun to be exploited in technologies for the selective removal and monitoring of PFAS in environmental waters. This review offers a comprehensive overview of recent developments in MIPs, both as adsorbents for PFAS removal and sensors that selectively detect PFAS at environmentally-relevant concentrations. PFAS-MIP adsorbents are classified according to their method of preparation (e.g., bulk or precipitation polymerization, surface imprinting), while PFAS-MIP sensing materials are described and discussed according to the transduction methods used (e.g., electrochemical, optical). This review aims to comprehensively discuss the PFAS-MIP research field. The efficacy and challenges facing the different applications of these materials in environmental water applications are discussed, as well as a perspective on challenges for this field that need to be overcome before exploitation of the technology can be fully realised.

Highly selective recovery of Ni(II) in neutral and acidic media using a novel Ni(II)-ion imprinted polymer

In this work, an original ion-imprinted polymer (IIP) was synthetized for the highly selective removal of Ni(II) ions in neutral and acidic media. First a novel functional monomer (AMP-MMA) was synthetized through the amidation of 2-(aminomethyl)pyridine (AMP) with methacryloylchloride. Following Ni(II)/AMP-MMA complex formation study, the Ni(II)-IIP was produced via inverse suspension polymerization (DMSO in mineral oil) and characterized with solid state ¹³C CPMAS NMR, FT-IR, SEM and nitrogen adsorption/desorption experiments. The Ni(II)-IIP was then used in solid-phase extraction of Ni(II) exploring a wide range of pH (from neutral to strongly acidic solution), several initial concentrations of Ni(II) (from 0.02 to 1 g/L), and the presence of competitive ions (Co(II), Cu(II), Cd(II), Mn(II), and Mg(II)). The maximum Ni(II) adsorption capacity at pH 2 and pH 7 reached values of 138.9 mg/g and 169.5 mg/g, that are among the best reported in literature. The selectivity coefficients toward Cd(II), Mn(II), Co(II), Mg(II) and Cu(II) are also very high, with values up to 38.6, 32.9, 25.2, 23.1 and 15.0, respectively. The Ni(II)-IIP showed good reusability of up to 5 cycles both with acidic and basic Ni(II) eluents.

Specialization of small non-conjugative plasmids in Escherichia coli according to their family types

We undertook a comprehensive comparative analysis of a collection of 30 small (<25 kb) non-conjugative Escherichia coli plasmids previously classified by the gene sharing approach into 10 families, as well as plasmids found in the National Center for Biotechnology Information (NCBI) nucleotide database sharing similar genomic sequences. In total, 302 mobilizable (belonging to 2 MOB_rep and 5 MOB_RNA families) and 106 non-transferable/relaxase-negative (belonging to three ReL_RNA families) plasmids were explored. The most striking feature was the specialization of the plasmid family types that was not related to their transmission mode and replication system. We observed a range of host strain specificity, from narrow E. coli host specificity to broad host range specificity, including a wide spectrum of Enterobacteriaceae. We found a wide variety of toxin/antitoxin systems and colicin operons in the plasmids, whose numbers and types varied according to the plasmid family type. The plasmids carried genes conferring resistance spanning almost all of the antibiotic classes, from those to which resistance developed early, such as sulphonamides, to those for which resistance has only developed recently, such as colistin. However, the prevalence of the resistance genes varied greatly according to the family type, ranging from 0 to 100 %. The evolutionary history of the plasmids based on the family type core genes showed variability within family nucleotide divergences in the range of E. coli chromosomal housekeeping genes, indicating long-term co-evolution between plasmids and host strains. In rare cases, a low evolutionary divergence suggested the massive spread of an epidemic plasmid. Overall, the importance of these small non-conjugative plasmids in bacterial adaptation varied greatly according to the type of family they belonged to, with each plasmid family having specific hosts and genetic traits.

PlaScope: a targeted approach to assess the plasmidome from genome assemblies at the species level

Plasmid prediction may be of great interest when studying bacteria of medical importance such as Enterobacteriaceae as well as Staphylococcus aureus or Enterococcus. Indeed, many resistance and virulence genes are located on such replicons with major impact in terms of pathogenicity and spreading capacities. Beyond strain outbreak, plasmid outbreaks have been reported in particular for some extended-spectrum beta-lactamase- or carbapenemase-producing Enterobacteriaceae. Several tools are now available to explore the ‘plasmidome’ from whole-genome sequences with various approaches, but none of them are able to combine high sensitivity and specificity. With this in mind, we developed PlaScope, a targeted approach to recover plasmidic sequences in genome assemblies at the species or genus level. Based on Centrifuge, a metagenomic classifier, and a custom database containing complete sequences of chromosomes and plasmids from various curated databases, PlaScope classifies contigs from an assembly according to their predicted location. Compared to other plasmid classifiers, PlasFlow and cBar, it achieves better recall (0.87), specificity (0.99), precision (0.96) and accuracy (0.98) on a dataset of 70 genomes of Escherichia coli containing plasmids. In a second part, we identified 20 of the 21 chromosomal integrations of the extended-spectrum beta-lactamase coding gene in a clinical dataset of E. coli strains. In addition, we predicted virulence gene and operon locations in agreement with the literature. We also built a database for Klebsiella and correctly assigned the location for the majority of resistance genes from a collection of 12 Klebsiella pneumoniae strains. Similar approaches could also be developed for other well-characterized bacteria.

Modified 3D-printed device for mercury determination in waters

3D printing technology is increasingly used in flow analysis, to develop low cost and tailor-made devices. The possibility of grafting specific molecules onto 3D printed parts offers new perspectives for the development of flow systems. In this study, a MPFS system including a dicarboxylate 1,5-diphenyl-3-thiocarbazone grafted 3D-printed device has been developed for mercury determination. For this purpose, the surface of 3D-printed cuboids was first modified with amine functional groups and then grafted with dicarboxylate 1,5-diphenyl-3-thiocarbazone. This new grafted device resulted in selective mercury preconcentration with extraction and elution yields higher than 90% even at high sampling flow rates. The detection can then be carried out in two ways: a direct detection of mercury extracted onto 3D-printed grafted cuboids by atomic absorption spectrophotometry after amalgam on gold or a detection of mercury in solution after elution with l-cysteine by spectrophotometry or cold vapour atomic absorption spectrometry.

Risk Factors for Infant Colonization by Hypervirulent CC17 Group B Streptococcus: Toward the Understanding of Late-onset Disease

The hypervirulent group B Streptococcus clone CC17 accounts for the majority of infant late-onset disease (LOD). We provide evidence that the high incidence of CC17 in LOD is likely due to an enhanced post-delivery mother-to-infant transmission.

Extended-spectrum β-lactamase-encoding genes are spreading on a wide range of Escherichia coli plasmids existing prior to the use of third-generation cephalosporins

To understand the evolutionary dynamics of extended-spectrum β-lactamase (ESBL)-encoding genes in Escherichia coli, we undertook a comparative genomic analysis of 116 whole plasmid sequences of human or animal origin isolated over a period spanning before and after the use of third-generation cephalosporins (3GCs) using a gene-sharing network approach. The plasmids included 82 conjugative, 22 mobilizable and 9 non-transferable plasmids and 3 P-like bacteriophages. ESBL-encoding genes were found on 64 conjugative, 6 mobilizable, 2 non-transferable plasmids and 2 P1-like bacteriophages, indicating that these last three types of mobile elements also play a role, albeit modest, in the diffusion of the ESBLs. The network analysis showed that the plasmids clustered according to their genome backbone type, but not by origin or period of isolation or by antibiotic-resistance type, including type of ESBL-encoding gene. There was no association between the type of plasmid and the phylogenetic history of the parental strains. Finer scale analysis of the more abundant clusters IncF and IncI1 showed that ESBL-encoding plasmids and plasmids isolated before the use of 3GCs had the same diversity and phylogenetic history, and that acquisition of ESBL-encoding genes had occurred during multiple independent events. Moreover, the blaCTX-M-15 gene, unlike other CTX-M genes, was inserted at a hot spot in a blaTEM-1-Tn2 transposon. These findings showed that ESBL-encoding genes have arrived on wide range of pre-existing plasmids and that the successful spread of blaCTX-M-15 seems to be favoured by the presence of well-adapted IncF plasmids that carry a Tn2-blaTEM-1 transposon.

Hypervirulent Klebsiella pneumoniae, a 5-year study in a French ICU

PURPOSE

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a leading cause of severe community-acquired pneumonia, liver abscess and disseminated infection in the Far East. Data regarding the incidence, clinical features and microbiological characteristics related to hvKp infections in the Western world are scarce.

METHODOLOGY

The incidence, clinical features and microbiological characteristics of hvKp infections were investigated through a 5-year survey conducted in a single French intensive care unit. K. pneumoniae strains were screened for hypermucoviscosity based on a string test. Multilocus sequence typing and multiplex PCR analysis targeting virulence genes were performed on string test-positive strains.

RESULTS

Over a 53-month period, a total of 59 infections due to K. pneumoniae were identified including 26 community-onset infections. Twelve hvKp infections were documented, accounting for 46.1 % of community-acquired K. pneumoniae. Community-acquired pneumonia (n=6), aspiration pneumonia (n=4) and liver abscess (n=2) represented initial sites and mode of infection. Compared to non-hvKp infections, patients with hvKp infections displayed higher rates of multi-organ failure (83.3 % vs 35.7 %; P=0.04), but mortality rates were not different (50 % vs 35 %; P=0.71). Strains K1/ST23 (n=5) and K2/ST86 (n=5) predominated. All hvKp strains displayed wild-type susceptibility.

CONCLUSION

hvKp represent a potentially underestimated cause of fatal infections in the Western world.

3D-printed flow system for determination of lead in natural waters

The development of 3D printing in recent years opens up a vast array of possibilities in the field of flow analysis. In the present study, a new 3D-printed flow system has been developed for the selective spectrophotometric determination of lead in natural waters. This system was composed of three 3D-printed units (sample treatment, mixing coil and detection) that might have been assembled without any tubing to form a complete flow system. Lead was determined in a two-step procedure. A preconcentration of lead was first carried out on TrisKem Pb Resin located in a 3D-printed column reservoir closed by a tapped screw. This resin showed a high extraction selectivity for lead over many tested potential interfering metals. In a second step, lead was eluted by ammonium oxalate in presence of 4-(2-pyridylazo)-resorcinol (PAR), and spectrophotometrically detected at 520nm. The optimized flow system has exhibited a linear response from 3 to 120µgL^-1. Detection limit, coefficient of variation and sampling rate were evaluated at 2.7µgL^-1, 5.4% (n=6) and 4 sampleh^-1, respectively. This flow system stands out by its fully 3D design, portability and simplicity for low cost analysis of lead in natural waters.

Phylogenetic, virulence and antibiotic resistance characteristics of commensal strain populations of Escherichia coli from community subjects in the Paris area in 2010 and evolution over 30 years

It is important to study commensal populations of Escherichia coli because they appear to be the reservoir of both extra-intestinal pathogenic E. coli and antibiotic resistant strains of E. coli. We studied 279 dominant faecal strains of E. coli from 243 adults living in the community in the Paris area in 2010. The phylogenetic group and subgroup [sequence type complex (STc)] of the isolates and the presence of 20 virulence genes were determined by PCR assays. The O-types and resistance to 18 antibiotics were assessed phenotypically. The B2 group was the most frequently recovered (34.0 %), followed by the A group (28.7 %), and other groups were more rare. The most prevalent B2 subgroups were II (STc73), IV (STc141), IX (STc95) and I (STc131), with 22.1, 21.1, 16.8 and 13.7 %, respectively, of the B2 group strains. Virulence factors (VFs) were more common in B2 group than other strains. One or more resistances were found in 125 strains (44.8 % of the collection) but only six (2.2 % of the collection) were multiresistant; no extended-spectrum beta-lactamase-producing strain was isolated. The C phylogroup and clonal group A strains were the most resistant. No trade-off between virulence and resistance was evidenced. We compared these strains with collections of strains gathered under the same conditions 30 and 10 years ago. There has been a parallel and linked increase in the frequency of B2 group strains (from 9.4 % in 1980, to 22.7 % in 2000 and 34.0 % in 2010) and of VFs. Antibiotic resistance also increased, from 22.6 % of strains resistant to at least one antibiotic in 1980, to 31.8 % in 2000 and 44.8 % in 2010; resistance to streptomycin, however, remained stable. Commensal human E. coli populations have clearly evolved substantially over time, presumably reflecting changes in human practices, and particularly increasing antibiotic use.

Risk Factors forClostridium difficileInfection in a Hepatology Ward

During 2001,Clostridium difficileinfection was observed in 23 patients hospitalized in a hepatology ward (attack rate, 0.9%). Since strain typing ruled out a clonal dissemination, we performed a case-control study. In addition to antibiotic use as a risk factor, theC. difficileinfection rate was higher among patients with autoimmune hepatitis (P< .01).

Prevalence of day-care centre children (France) with faecal CTX-M-producing Escherichia coli comprising O25b:H4 and O16:H5 ST131 strains

OBJECTIVES

Determining the prevalence of children in day-care centres (DCCs) carrying faecal extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and molecularly characterizing those belonging to the Escherichia coli species.

METHODS

Stools were collected from children's diapers (January-April 2012) in randomly chosen DCCs and plated onto ChromID ESBL. Colonies growing on this medium were identified by the Vitek 2 system and tested for antibiotic susceptibility and for ESBL production by the double-disc synergy test. ESBL genotypes were determined as well as phylogenetic groups, ERIC-2 (enterobacterial repetitive intergenic consensus) PCR profiles and sequence types (STs) for the E. coli isolates. Serotypes, virotypes, fimH alleles, ESBL-carrying plasmids and PFGE patterns were determined for the ST131 E. coli isolates.

RESULTS

Among 419 children from 25 participating DCCs, 1 was colonized by CTX-M-15-producing Klebsiella pneumoniae and 27 (6.4%) by E. coli, which all produced CTX-M enzymes [CTX-M-15 (37%), CTX-M-1 (26%), CTX-M-14 (22%), CTX-M-27 (11%) and CTX-M-22 (4%)]. The 27 E. coli isolates, 55.5% belonging to group B2, displayed 20 ERIC-2 PCR profiles and 16 STs. The ST131 E. coli isolates were dominant (44%), displayed serotypes O25b:H4 and O16:H5, fimH alleles 30 and 41 and virotypes A and C. According to the PFGE patterns, one strain of E. coli ST131 producing a CTX-M-15 enzyme carried by an IncF F2:A1:B- plasmid had spread within one DCC.

CONCLUSIONS

This study shows a notable prevalence (6.4%) of DCC children with faecal CTX-M-producing E. coli isolates comprising a high proportion of E. coli ST131 isolates, suggesting that these children might be a reservoir of this clone.

Complexity of Escherichia coli bacteremia pathophysiology evidenced by comparison of isolates from blood and portal of entry within single patients

The portal of entry of Escherichia coli bacteremia, a frequent and severe disease, is most commonly the urinary tract followed by the digestive tract. Recent reports have evidenced the presence of several distinct E. coli clones within a single patient suffering of extra-intestinal infection. To explore the relationships between the blood and portal of entry strains, we thoroughly studied 98 bacteremic patients from the French prospective COLIBAFI cohort. In these patients, we compared genotypically and phenotypically E. coli strains isolated from the blood and the suspected portal of entry [non-urinary pus (n=52) and urine (n=52)]. We found genetically distinct strains exhibiting distinct antibiotypes in the blood and pus samples (8 patients; 15%) and the blood and urine samples (2 patients; 3.8%) (p=0.09). These data highlight the complexity of pathophysiology of E. coli bacteremia and should be taken into consideration when strain antibiotic susceptibility is tested, especially in bacteremia of pus origin.

Longitudinal study assessing the return of chloroquine susceptibility of Plasmodium falciparum in isolates from travellers returning from West and Central Africa, 2000-2011

Background

Chloroquine (CQ) was the main malaria therapy worldwide from the 1940s until the 1990s. Following the emergence of CQ-resistant Plasmodium falciparum, most African countries discontinued the use of CQ, and now promote artemisinin-based combination therapy as the first-line treatment. This change was generally initiated during the last decade in West and Central Africa. The aim of this study is to describe the changes in CQ susceptibility in this African region, using travellers returning from this region as a sentinel system.

Methods

The study was conducted by the Malaria National Reference Centre, France. The database collated the pfcrtK76T molecular marker for CQ susceptibility and the in vitro response to CQ of parasites from travellers’ isolates returning from Senegal, Mali, Ivory Coast or Cameroon. As a proxy of drug pressure, data regarding CQ intake in febrile children were collated for the study period. Logistic regression models were used to detect trends in the proportions of CQ resistant isolates.

Results

A total of 2874 parasite isolates were genotyped between 2000–2011. The prevalence of the pfcrt76T mutant genotype significantly decreased for Senegal (from 78% to 47%), Ivory Coast (from 63% to 37%), Cameroon (from 90% to 59%) and remained stable for Mali. The geometric mean of the 50% inhibitory concentration (IC₅₀) of CQ in vitro susceptibility and the proportion of resistant isolates (defining resistance as an IC50 value > 100 nM) significantly decreased for Senegal (from 86 nM (59%) to 39 nM (25%)), Mali (from 84 nM (50%) to 51 nM (31%)), Ivory Coast (from 75 nM (59%) to 29 nM (16%)) and Cameroon (from 181 nM (75%) to 51 nM (37%)). Both analyses (molecular and in vitro susceptibility) were performed for the 2004–2011 period, after the four countries had officially discontinued CQ and showed an accelerated decline of the resistant isolates for the four countries. Meanwhile, CQ use among children significantly deceased in this region (fixed effects slope = −0.3, p < 10^-3).

Conclusions

An increase in CQ susceptibility following official withdrawal of the drug was observed in travellers returning from West and Central African countries. The same trends were observed for molecular and in vitro analysis between 2004-2011and they correlated to the decrease of the drug pressure.

Bacteraemia caused by third-generation cephalosporin-resistant Escherichia coli in France: prevalence, molecular epidemiology and clinical features

Escherichia coli is one of the major pathogens responsible for bactaeremia. Empirical antibiotherapy of these infections usually relies on third-generation cephalosporins (3GCs). Thus, the occurrence and epidemiology of 3GC-resistant strains have to be monitored. The French prospective multicentre study COLIBAFI collected 1081 strains of E. coli responsible for bacteraemia in 2005. In the present work, the prevalence of resistance to 3GCs was evaluated, and the implicated molecular mechanisms were characterized by specific PCR and sequencing. Phylogenetic grouping, O-typing, pulsed-field gel electrophoresis and virulence factor analysis were used to investigate the genetic background of the 3GC-resistant (3GC-R) strains. Clinical features of the patients with documented data (n = 1051) were analysed. Decreased susceptibility to 3GCs was observed in 41 strains (3.8%): 19, 18 and four had extended-spectrum β-lactamase (ESBL), AmpC cephalosporinase and OXA-type penicillinase phenotypes, respectively. Pulsed-field gel electrophoresis revealed that the 3GC-R strains constitute a diverse population. All but one of the strains with an ESBL phenotype produced a CTX-M-type enzyme, and six of them belonged to the widespread intercontinental clone O25b:H4-ST131. AmpC phenotype strains harboured various chromosomal ampC promoter and coding region mutations and/or the bla(CMY-2) plasmidic gene. 3GC-R strains carried fewer virulence factors and were more co-resistant to other antibiotics than 3GC-susceptible (3GC-S) strains. Infections with 3GC-R strains were mostly community-acquired and, as compared with those caused by their 3GC-S counterparts, were more severe. Underlying chronic disease and prior use of antibiotics were independent risk factors for development of a 3GC-R strain bacteraemia. The fact that the molecular support of 3GC resistance is mainly plasmid-mediated represents a potentially epidemic threat.

CRISPR distribution within the Escherichia coli species is not suggestive of immunity-associated diversifying selection

In order to get further insights into the role of the clustered, regularly interspaced, short palindromic repeats (CRISPRs) in Escherichia coli, we analyzed the CRISPR diversity in a collection of 290 strains, in the phylogenetic framework of the strains represented by multilocus sequence typing (MLST). The set included 263 natural E. coli isolates exposed to various environments and isolated over a 20-year period from humans and animals, as well as 27 fully sequenced strains. Our analyses confirm that there are two largely independent pairs of CRISPR loci (CRISPR1 and -2 and CRISPR3 and -4), each associated with a different type of cas genes (Ecoli and Ypest, respectively), but that each pair of CRISPRs has similar dynamics. Strikingly, the major phylogenetic group B2 is almost devoid of CRISPRs. The majority of genomes analyzed lack Ypest cas genes and contain CRISPR3 with spacers matching Ypest cas genes. The analysis of relatedness between strains in terms of spacer repertoire and the MLST tree shows a pattern where closely related strains (MLST phylogenetic distance of <0.005 corresponding to at least hundreds of thousands of years) often exhibit identical CRISPRs while more distantly related strains (MLST distance of >0.01) exhibit completely different CRISPRs. This suggests rare but radical turnover of spacers in CRISPRs rather than CRISPR gradual change. We found no link between the presence, size, or content of CRISPRs and the lifestyle of the strains. Our data suggest that, within the E. coli species, CRISPRs do not have the expected characteristics of a classical immune system.

Molecular and evolutionary bases of within-patient genotypic and phenotypic diversity in Escherichia coli extraintestinal infections

Although polymicrobial infections, caused by combinations of viruses, bacteria, fungi and parasites, are being recognised with increasing frequency, little is known about the occurrence of within-species diversity in bacterial infections and the molecular and evolutionary bases of this diversity. We used multiple approaches to study the genomic and phenotypic diversity among 226 Escherichia coli isolates from deep and closed visceral infections occurring in 19 patients. We observed genomic variability among isolates from the same site within 11 patients. This diversity was of two types, as patients were infected either by several distinct E. coli clones (4 patients) or by members of a single clone that exhibit micro-heterogeneity (11 patients); both types of diversity were present in 4 patients. A surprisingly wide continuum of antibiotic resistance, outer membrane permeability, growth rate, stress resistance, red dry and rough morphotype characteristics and virulence properties were present within the isolates of single clones in 8 of the 11 patients showing genomic micro-heterogeneity. Many of the observed phenotypic differences within clones affected the trade-off between self-preservation and nutritional competence (SPANC). We showed in 3 patients that this phenotypic variability was associated with distinct levels of RpoS in co-existing isolates. Genome mutational analysis and global proteomic comparisons in isolates from a patient revealed a star-like relationship of changes amongst clonally diverging isolates. A mathematical model demonstrated that multiple genotypes with distinct RpoS levels can co-exist as a result of the SPANC trade-off. In the cases involving infection by a single clone, we present several lines of evidence to suggest diversification during the infectious process rather than an infection by multiple isolates exhibiting a micro-heterogeneity. Our results suggest that bacteria are subject to trade-offs during an infectious process and that the observed diversity resembled results obtained in experimental evolution studies. Whatever the mechanisms leading to diversity, our results have strong medical implications in terms of the need for more extensive isolate testing before deciding on antibiotic therapies.

We investigated whether an infection is a site of pathogen within-species diversity. Our results indicate that there is indeed extensive diversity during human extraintestinal infections by Escherichia coli. This diversity was of two types, not mutually exclusive, as we found that patients were infected either by several distinct E. coli clones or by members of a single clone that exhibit micro-heterogeneity. The high degree of phenotypic diversity, including antibiotic resistance, suggests that there is no uniform selection pressure leading to a single fitter clone during an infection. We discuss a possible mechanism and a mathematical model that explains these unexpected results. Our data suggest that the evolution of diversity in the course of an infection and in in vitro experimental evolution in the absence of host immune selective pressure may have many parallels. Whatever the mechanisms leading to diversity, our results have strong medical implications in terms of the need for more extensive isolate testing before deciding on antibiotic therapies.

Molecular characterization of addiction systems of plasmids encoding extended-spectrum beta-lactamases in Escherichia coli

OBJECTIVES

Escherichia coli producing CTX-M-type extended-spectrum beta-lactamases (ESBLs) are spreading worldwide. The aim of this work was to investigate the addiction systems carried by the replicons involved in the emergence and spread of ESBLs in relation to ESBL and replicon types.

METHODS

A collection of 125 TEM, SHV and CTX-M ESBL-producing E. coli isolates and their 125 transconjugants or transformants was analysed. Five plasmid protein antitoxin-regulated systems and three plasmid antisense RNA-regulated systems were sought by PCR.

RESULTS

Two hundred and ninety-eight plasmid addiction systems were detected in the parental strains (mean 2.38, range 0-6 per strain) and 86 were detected in the recipient strains (mean 0.69, range 0-5 per strain). PemKI, CcdAB, Hok-Sok and VagCD were the most frequently represented systems in both recipient and parental strains. The parental SHV and CTX-M ESBL-producing strains had more addiction systems than the TEM ESBL producers. In the recipient strains, the frequency of addiction systems was significantly higher in IncF plasmids. Among the IncF replicons carrying CTX-M-type enzymes, the frequency of addiction systems was significantly higher in IncF plasmids carrying CTX-M-15 (mean 3.5) or CTX-M-9 (mean 4) than in those carrying CTX-M-14 (mean 0.6).

CONCLUSIONS

In E. coli producing CTX-M-15 or CTX-M-9 ESBLs, plasmids bearing the bla(CTX-M) gene have multiple addiction systems that could contribute to their maintenance in host strains.

Rapid detection of the O25b-ST131 clone of Escherichia coli encompassing the CTX-M-15-producing strains

OBJECTIVES

Recently, a CTX-M-15 extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli O25b-ST131 clone, belonging to the B2 phylogenetic group and with a high virulence potential, has been reported all over the world, representing a major public health problem. The present study was carried out to develop a rapid and simple detection assay that identifies members of this clone.

METHODS

A total of 627 E. coli isolates of which 373 produced an ESBL, collected across four continents, were screened using a O25b-ST131 clone allele-specific PCR for the pabB gene.

RESULTS

One hundred and forty-three ESBL isolates were found positive with the assay. These isolates were all of O25b type and, when studied by multilocus sequence typing (25 cases), were all of ST131. The O25b-ST131 clone was found to produce ESBLs other than CTX-M-15, specifically CTX-M-2, -3, -14, -27, -32 and -61 as well as TEM-24. This clone represents 3% of non-ESBL B2 isolates originating from urinary tract infections in Paris.

CONCLUSIONS

We have developed a PCR-based assay that easily identifies a clone with high likelihood of producing ESBLs, including CTX-M-15.

Multiple acquisitions of CTX-M plasmids in the rare D2 genotype of Escherichia coli provide evidence for convergent evolution

Over the last decade, CTX-M enzymes have become the most prevalent extended-spectrum beta-lactamases (ESBLs) worldwide, mostly in Escherichia coli, causing a major health problem. An epidemiological relationship has been established between a rare genotype of E. coli, the D(2) genotype, and the presence of CTX-M genes. We investigated this striking association by exploring the genetic backgrounds of 18 D(2) genotype CTX-M-producing strains and of the plasmids encoding CTX-M enzymes. The 18 strains had different genetic backgrounds, as assessed by multilocus sequence and O typing, and were associated with various plasmids bearing diverse CTX-M genes. The region encompassing the genetic marker of the D(2) genotype (TSPE4.C2) was not correlated with the presence of CTX-M genes. CTX-M-producing D(2) strains had far fewer virulence factors than a control group of 8 non-ESBL-producing D(2) strains, and an inverse relationship was found between the number of co-resistances associated with the CTX-M gene and the number of virulence factors found in the strain. These findings provide evidence for multiple acquisitions of plasmids carrying CTX-M genes in different D(2) genotype strains. They strongly suggest that convergent evolution has occurred, and indicate that there has been selection for the association of a specific genetic background of the strain and the CTX-M gene. This fine-tuning of the relationship between the D(2) genotype and CTX-M genes presumably increases the fitness of the strain, indicating a role for the host cell in the acquisition and dissemination of CTX-M genes.

Methicillin-resistant Staphylococcus aureus carriage in a long-term care facility: hypothesis about selection and transmission

BACKGROUND

many studies have identified long-term care facilities (LTCFs) as reservoirs of patients carrying methicillin-resistant Staphylococcus aureus (MRSA). However, few data about the mechanisms of MRSA diffusion in these settings are available.

OBJECTIVES

the purpose of our study was to suggest hypothesis on the possible ways of MRSA transmission to residents in or outside a LTCF.

METHODS

data concerning patients on the day of the survey and within the preceding year were collected. Multivariate analysis was performed by logistic regression to identify characteristics associated with MRSA carriage. MRSA strains were analysed by pulsed-field gel electrophoresis (PFGE) and the relatedness between DNA patterns was studied with Gel Compar software.

RESULTS

the prevalence of MRSA carriage was 37.6%. Treatment with fluoroquinolones or third-generation cephalosporins [odds ratio (OR) = 12.07; 95% confidence interval (CI) = 5.90-24.7], treatment with other antimicrobial agents (OR = 4.40; 95% CI = 2.43-7.97), at least one medical imaging session (OR = 5.08; 95% CI = 2.66-9.69) within the 12 preceding months, and the presence of a subcutaneous catheter on the day of the survey (OR = 3.09; 95% CI = 1.87-5.10) were independently associated with MRSA carriage. Twenty-eight of the 38 strains tested were clustered in two major groups. In each of these groups, strains had at least a 90% relatedness. These strains were isolated in patients hospitalised in different areas of the LTCF.

CONCLUSION

we identified that both molecular and epidemiological arguments support the hypothesis of the possibility of MRSA cross-transmission inside the LTCF. Further studies are needed to confirm and explain the association identified between MRSA carriage and medical imaging.

The CTX-M-15-producing Escherichia coli diffusing clone belongs to a highly virulent B2 phylogenetic subgroup

OBJECTIVES

A clone of CTX-M-15-producing Escherichia coli has recently been reported to be spreading through Europe and Africa. The aim of this work was to thoroughly characterize this clone.

MATERIALS AND METHODS

Representative isolates of this clone were subjected to multilocus sequence typing, O typing, virulence gene detection, adhesion assay on human cells, biofilm production assay and mouse lethality assay.

RESULTS

The clone: (i) belongs to a unique B2 phylogenetic subgroup encompassing the pyelonephritogenic diffusely adhering EC7372 strain; (ii) exhibits a specific O25b molecular subtype; (iii) is identical to the E. coli clone O25:H4-ST131 producing CTX-M-15; (iv) produces biofilm; and (v) is highly virulent in mice despite lacking classical extraintestinal pathogenicity islands (except for high pathogenicity island) and the afa/dra gene.

CONCLUSIONS

The CTX-M-15-producing E. coli diffusing clone is associated with a high level of antibiotic resistance and with high virulence, showing that, under certain selective pressures, the previously observed trade-off between resistance and virulence may not apply.