Spread of bla(CTX-M-14) is driven mainly by IncK plasmids disseminated among Escherichia coli phylogroups A, B1, and D in Spain

blaNDM-5 carried by an IncX3 plasmid in Escherichia coli sequence type 167

bla(NDM-)5 was found in Escherichia coli strain 0215 from a Chinese patient without travel history. Genomic sequencing and conjugation experiments were performed. Strain 0215 belonged to sequence type 167 (ST167) and had other resistance determinants, including bla(TEM-135), bla(CTX-M-14), and aac(6')-Ib. bla(NDM-5) was carried by a 47-kb self-transmissible IncX3 plasmid and was in a complex genetic context similar to that of bla(NDM-1) on IncX3 plasmids. IncX3 plasmids might have emerged as a common vehicle mediating the spread of bla(NDM).

Overlapped sequence types (STs) and serogroups of avian pathogenic (APEC) and human extra-intestinal pathogenic (ExPEC) Escherichia coli isolated in Brazil

Avian pathogenic Escherichia coli (APEC) strains belong to a category that is associated with colibacillosis, a serious illness in the poultry industry worldwide. Additionally, some APEC groups have recently been described as potential zoonotic agents. In this work, we compared APEC strains with extraintestinal pathogenic E. coli (ExPEC) strains isolated from clinical cases of humans with extra-intestinal diseases such as urinary tract infections (UTI) and bacteremia. PCR results showed that genes usually found in the ColV plasmid (tsh, iucA, iss, and hlyF) were associated with APEC strains while fyuA, irp-2, fepC sitDchrom, fimH, crl, csgA, afa, iha, sat, hlyA, hra, cnf1, kpsMTII, clpVSakai and malX were associated with human ExPEC. Both categories shared nine serogroups (O2, O6, O7, O8, O11, O19, O25, O73 and O153) and seven sequence types (ST10, ST88, ST93, ST117, ST131, ST155, ST359, ST648 and ST1011). Interestingly, ST95, which is associated with the zoonotic potential of APEC and is spread in avian E. coli of North America and Europe, was not detected among 76 APEC strains. When the strains were clustered based on the presence of virulence genes, most ExPEC strains (71.7%) were contained in one cluster while most APEC strains (63.2%) segregated to another. In general, the strains showed distinct genetic and fingerprint patterns, but avian and human strains of ST359, or ST23 clonal complex (CC), presented more than 70% of similarity by PFGE. The results demonstrate that some "zoonotic-related" STs (ST117, ST131, ST10CC, ST23CC) are present in Brazil. Also, the presence of moderate fingerprint similarities between ST359 E. coli of avian and human origin indicates that strains of this ST are candidates for having zoonotic potential.

Co-resistance to different classes of antibiotics among ESBL-producers from aquatic systems

In this study we investigated the co-occurrence of resistance to non-beta-lactams among cefotaxime-resistant extended-spectrum beta-lactamase (ESBL) producers (ESBL(+)) versus non-ESBL producers (ESBL(-)), from aquatic environments. Higher prevalence of resistance to tetracycline, fluoroquinolones and aminoglycosides were observed in ESBL(+). Among ESBL(+) resistant to tetracycline (n = 18), tet(A) was detected in 88.9% and tet(B) in 16.7%. Among fluoroquinolone-resistant-ESBL(+) (n = 15), aacA4-cr and qnrVC4 were identified in 26.6% and 40% strains, respectively. The qnrVC4 gene was detected for the first time in Pseudomonas sp. and Escherichia coli. Class 1 integrase genes were detected in 56.41% of ESBL(+) and in 27.67% ESBL(-). Gene cassette arrays identified conferred resistance to aminoglycosides (aadA-type genes and aacA4), trimethoprim (dfrA17), chloramphenicol (catB8), fluoroquinolones (qnrVC4) and beta-lactams (blaOXA-10). Conjugation experiments were performed with CTX-M-producers. Transconjugants showed multiresistance to 3 or more classes of antibiotics, and conjugative plasmids were assigned to IncF, IncK and IncI1 replicons. Results obtained showed that co-selection of resistance to aminoglycosides, quinolones and tetracyclines is prevalent among ESBL-producers and that these features are successfully mobilized by IncF, IncK and IncI1 conjugative plasmids. This study reinforces the importance of natural aquatic systems as reservoir of mobile genetic platforms carrying multiple resistance determinants. Moreover, to the best of our knowledge, this constitutes the first observation of IncK::CTX-M-3 in Aeromonas hydrophila and the first report of IncK plasmids in Portugal.

Cefotaxime resistant Escherichia coli collected from a healthy volunteer; characterisation and the effect of plasmid loss

In this study 6 CTX-M positive E. coli isolates collected during a clinical study examining the effect of antibiotic use in a human trial were analysed. The aim of the study was to analyse these isolates and assess the effect of full or partial loss of plasmid genes on bacterial fitness and pathogenicity. A DNA array was utilised to assess resistance and virulence gene carriage. Plasmids were characterised by PCR-based replicon typing and addiction system multiplex PCR. A phenotypic array and insect virulence model were utilised to assess the effect of plasmid-loss in E. coli of a large multi-resistance plasmid. All six E. coli carrying bla_CTX-M-14 were detected from a single participant and were identical by pulse field gel electrophoresis and MLST. Plasmid profiling and arrays indicated absence of a large multi-drug resistance (MDR) F-replicon plasmid carrying blaTEM, aadA4, strA, strB, dfrA17/19, sul1, and tetB from one isolate. Although this isolate partially retained the plasmid it showed altered fitness characteristics e.g. inability to respire in presence of antiseptics, similar to a plasmid-cured strain. However, unlike the plasmid-cured or plasmid harbouring strains, the survival rate for Galleria mellonella infected by the former strain was approximately 5-times lower, indicating other possible changes accompanying partial plasmid loss. In conclusion, our results demonstrated that an apparently healthy individual can harbour bla_CTX-M-14E. coli strains. In one such strain, isolated from the same individual, partial absence of a large MDR plasmid resulted in altered fitness and virulence characteristics, which may have implications in the ability of this strain to infect and any subsequent treatment.

Molecular and phenotypic characterization of Escherichia coli isolated from broiler chicken flocks in Egypt

Avian pathogenic Escherichia coli (APEC) infection is responsible for great economic losses to the poultry industry worldwide and there is increasing evidence of its zoonotic importance. In this study, 219 E. coli isolates from 84 poultry flocks in Egypt, including 153 APEC, 30 avian fecal E. coli (AFEC), and 36 environmental E. coli, were subjected to phylogenetic grouping and virulence genotyping. Additionally, 50 of these isolates (30 APEC from colisepticemia and 20 AFEC) were subjected to a more-extensive characterization which included serogrouping, antimicrobial susceptibility analysis, screening for seven intestinal E. coli virulence genes (stx1, stx2, eae, espP, KatP, hlyA, and fliCh7), multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and in vivo virulence testing. More than 90% of the total APEC examined possessed iroN, ompT, hlyF, iss, and iutA, indicating that Egyptian APECs, like their counterparts from the United States, harbor plasmid pathogenicity islands (PAIs). The majority of APEC and AFEC were of phylogenetic groups A, B1, and D. For the 50-isolate subgroup, more than 70% of APEC and 80% ofAFEC were multidrug resistant. Among the subgroup of APEC, MLST analysis identified 11 sequence types (ST) while seven STs were found among AFEC. Based on PFGE, the genetic relatedness of APEC and AFEC ranged from 50%-100% and clustered into four primary groups at 50% similarity. Two of the eight APEC strains tested in chickens were able to induce 25% mortality in 1-day-old chicks. APECs were distinguished from AFECs and environmental E. coli by their content of plasmid PAI genes, whereas APEC isolated from colisepticemia and AFEC were not distinguishable based on their antimicrobial resistance patterns, as both groups were multidrug resistant. Avian E. coli strains from broiler flocks in Egypt show similar sequence types to E. coli associated with human infection.

Microbiological quality of ready-to-eat salads: an underestimated vehicle of bacteria and clinically relevant antibiotic resistance genes

The increase demand for fresh vegetables is causing an expansion of the market for minimally processed vegetables along with new recognized food safety problems. To gain further insight on this topic we analyzed the microbiological quality of Portuguese ready-to-eat salads (RTS) and their role in the spread of bacteria carrying acquired antibiotic resistance genes, food products scarcely considered in surveillance studies. A total of 50 RTS (7 brands; split or mixed leaves, carrot, corn) were collected in 5 national supermarket chains in Porto region (2010). They were tested for aerobic mesophilic counts, coliforms and Escherichia coli counts as well as for the presence of Salmonella and Listeria monocytogenes. Samples were also plated in different selective media with/without antibiotics before and after enrichment. The E. coli, other coliforms and Enterococcus recovered were characterized for antibiotic resistance profiles and clonality with phenotypic and genetic approaches. A high number of RTS presented poor microbiological quality (86%--aerobic mesophilic counts, 74%--coliforms, 4%--E. coli), despite the absence of screened pathogens. In addition, a high diversity of bacteria (species and clones) and antibiotic resistance backgrounds (phenotypes and genotypes) were observed, mostly with enrichment and antibiotic selective media. E. coli was detected in 13 samples (n=78; all types and 4 brands; phylogenetic groups A, B1 and D; none STEC) with resistance to tetracycline [72%; tet(A) and/or tet(B)], streptomycin (58%; aadA and/or strA-strB), sulfamethoxazole (50%; sul1 and/or sul2), trimethoprim (50%; dfrA1 or dfrA12), ampicillin (49%; blaTEM), nalidixic acid (36%), ciprofloxacin (5%) or chloramphenicol (3%; catA). E. coli clones, including the widespread group D/ST69, were detected in different samples from the same brand or different brands pointing out to a potential cross-contamination. Other clinically relevant resistance genes were detected in 2 Raoultella terrigena carrying a bla(SHV-2) and 1 Citrobacter freundii isolate with a qnrB9 gene. Among Enterococcus (n=108; 35 samples; Enterococcus casseliflavus--40, Enterococcus faecalis--20, Enterococcus faecium--18, Enterococcus hirae--9, Enterococcus gallinarum--5, and Enterococcus spp.--16) resistance was detected for tetracyclines [6%; tet(M) and/or tet(L)], erythromycin [3%; erm(B)], nitrofurantoin (1%) or ciprofloxacin (1%). The present study places ready-to-eat salads within the spectrum of ecological niches that may be vehicles for antibiotic resistance bacteria/genes with clinical interest (e.g. E. coli-D-ST69; bla(SHV-2)) and these findings are worthy of attention as their spread to humans by ingestion cannot be dismissed.

Diversity and biofilm-production ability among isolates of Escherichia coli phylogroup D belonging to ST69, ST393 and ST405 clonal groups

Background

Phylogenetic group D Escherichia coli clones (ST69, ST393, ST405) are increasingly reported as multidrug resistant strains causing extra-intestinal infections. We aim to characterize inter- and intraclonal diversity of a broad sample (isolates from different geographic locations and origins with variable antibiotic resistance profiles, 1980-2010) and their ability to adhere and form biofilm by both a modified quantitative biofilm producing assay and Field Emission Scanning Electron Microscopy (FESEM).

Results

High virulence scores were observed among ST69 (median 14/range 9–15) and ST393 (median 14/range 8–15) clones, particularly enriched in pap alleles, iha, kpsMTII-K5 and ompT, in contrast with ST405 (median 6/range 2–14) isolates, exhibiting frequently fyuA, malX and traT. All ST69 and ST393 and only two ST405 isolates were classified as ExPEC. Biofilm production was detected in two non-clinical ST69 and three ST393 isolates from different origins showing variable virulence profiles. Within each clonal group, and despite the high diversity of PFGE-types observed, isolates from different countries and recovered over large periods of time were clustered in a few groups sharing common virulence gene profiles among ST69 (n = 10 isolates) and ST393 (n = 9 isolates) (fimH-iha-iutA-kpsMTII-K5-(traT)-sat-(ompT)-papA-papEF-papGII-papC) or ST405 (n = 6 isolates) (fimH-traT-fyuA-malX).

Conclusions

This study highlights the circulation of highly transmissible ST69, ST393 and ST405 variants among different settings. Biofilm production seems not to be directly correlated with their epidemiological success.

Cross-sectional study on prevalence and molecular characteristics of plasmid mediated ESBL/AmpC-producing Escherichia coli isolated from veal calves at slaughter

Objectives

The presence of ESBL/AmpC-producing E. coli in cattle has been reported previously, however information on veal calves is limited. This study describes the prevalence and molecular characteristics of E. coli with non-wild type susceptibility to cefotaxime in veal calves at slaughter.

Methods

Faecal samples from 100 herds, 10 individual animals per herd, were screened for E. coli with non-wild type susceptibility for cefotaxime. Molecular characterization of ESBL/AmpC genes and plasmids was performed on one isolate per herd by microarray, PCR and sequence analysis.

Results

66% of the herds were positive for E. coli with non-wild type susceptibility for cefotaxime. Within-herd prevalence varied from zero to 90%. 83% of E. coli producing ESBL/AmpC carried bla_CTX-M genes, of which bla_CTX-M-1, bla_CTX-M-14 and bla_CTX-M-15 were most prevalent. The dominant plasmids were IncI1 and IncF-type plasmids.

Conclusions

A relatively high prevalence of various bla_CTX-M producing E. coli was found in veal calves at slaughter. The genes were mainly located on IncI1 and IncF plasmids.

Direct sequencing of small genomes on the Pacific Biosciences RS without library preparation

We have developed a sequencing method on the Pacific Biosciences RS sequencer (the PacBio) for small DNA molecules that avoids the need for a standard library preparation. To date this approach has been applied toward sequencing single-stranded and double-stranded viral genomes, bacterial plasmids, plasmid vector models for DNA-modification analysis, and linear DNA fragments covering an entire bacterial genome. Using direct sequencing it is possible to generate sequence data from as little as 1 ng of DNA, offering a significant advantage over current protocols which typically require 400-500 ng of sheared DNA for the library preparation.

Molecular characterization of multiresistant Escherichia coli producing or not extended-spectrum β-lactamases

BACKGROUND

The prevalence and type of plasmids, resistance genes and integrons carried by two collections of multiresistant E. coli producing or not extended-spectrum β-lactamases have been compared. Rep-PCR was used to determine the clonal relationship of the organisms. Plasmids were classified according to their incompatibility. Class 1 and Class 2 integrons and antibiotic resistance genes were analysed by PCR and sequencing.

RESULTS

Both collections of organisms contained a large diversity of unrelated strains with some clones distributed in both groups of isolates. Large plasmids were identified in the two groups of organisms. Plasmids with replicons repK and repColE were more frequent among ESBL-producing isolates, while repFIA, repFII and repA/C replicons were more frequent in isolates lacking ESBL. Conjugative plasmids with repK and repA/C replicons coded for CTX-M-14 and CMY-2 β-lactamases, respectively. No significant differences were observed in the distribution of class 1 and class 2 integrons among multiresistant E. coli producing or not ESBL, and dfrA17-ant(3")-Ie was the cassette arrangement most commonly found.

CONCLUSIONS

In the concrete temporal and geographical context of this study, multiresistant E. coli producing ESBL or other mechanisms of resistance were largely clonally diverse and present some differences in the types of harboured plasmids. Still, some clones were found in both ESBL-producing and -lacking isolates.

Molecular characterization of CTX-M β-lactamase and associated addiction systems in Escherichia coli circulating among cattle, farm workers, and the farm environment

A total of 84 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates from cattle, farm workers, and the farm environment isolated from February to September 2008 in the Republic of Korea were investigated. All 84 ESBL-producing isolates carried blaCTX-M genes that belonged to the CTX-M-1 (n = 35) or CTX-M-9 (n = 49) family. The most predominant CTX-M type identified was CTX-M-14 (n = 49), followed by CTX-M-32 (n = 26). The blaCTX-M genes were identified most commonly in E. coli isolates from feces (n = 29), teats (n = 25), and milk (n = 14). A blaCTX-M-14 gene was also detected in an E. coli isolate from a farmer's hand. Transfer of the blaCTX-M gene from 60 blaCTX-M-positive E. coli isolates to the recipient E. coli J53 strain by conjugation was demonstrated. Plasmid isolation from blaCTX-M-positive transconjugants revealed a large (95- to 140-kb) conjugative plasmid. Almost all (82/84) blaCTX-M genes possessed an insertion sequence, ISEcp1, upstream of the blaCTX-M gene. Only in the case of the CTX-M-14 genes was IS903 downstream of the gene. The blaCTX-M genes were associated with seven kinds of addiction systems. Among them, pndAC, hok-sok, and srnBC were the most frequently identified addiction systems in both wild strains and transconjugants. The spread of blaCTX-M genes was attributed to both clonal expansion and horizontal dissemination. Our data suggest that a combination of multiple addiction systems in plasmids carrying blaCTX-M genes could contribute to their maintenance in the host cells. To our knowledge, the blaCTX-M-32 gene has not previously been reported in animal isolates from the Republic of Korea.

Commensal Enterobacteriaceae as reservoirs of extended-spectrum beta-lactamases, integrons, and sul genes in Portugal

Bacteria colonizing the human intestine have a relevant role in the spread of antimicrobial resistance. We investigated the faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in healthy humans from Portugal and analyzed the distribution of sul genes and class 1 and 2 integrons. Faecal samples (n = 113) were recovered from healthy persons (North/Centre of Portugal, 2001-2004) and plated on MacConkey agar with and without ceftazidime (1 mg/L) or cefotaxime (1 mg/L). Isolates representing different morphotypes/plate and antibiotic susceptibility patterns (n = 201) were selected. Isolates resistant to sulfonamides and/or streptomycin, gentamicin, and trimethoprim were screened (PCR and sequencing) for sul genes (sul1, sul2, sul3) and class 1 and 2 integrons. Presence of ESBLs was inferred using the double disk synergy test (DDST) and further confirmed by PCR and sequencing. ESBL producers were selected for clonal analysis, plasmid characterization and conjugation assays by standard methods. ESBL-producing isolates were found in 1.8% (2/113) of samples, corresponding to Escherichia coli of phylogroups A (n = 1) and B1 (n = 1) carrying transferable bla CTX-M-14 and the new bla TEM-153, respectively. A 80kb IncK plasmid bearing bla CTX-M-14 was found, being highly related to that widely spread among CTX-M-14 producers of humans and animals from Portugal and other European countries. sul genes were found in 88% (22/25; sul2-60%, sul1-48%, sul3-4%) of the sulfonamide resistant isolates. Class 1 integrons were more frequently found than class 2 (7%, 14/201 vs. 3%, 6/201). Interestingly, gene cassette arrangements within these platforms were identical to those commonly observed among Enterobacteriaceae from Portuguese food-producing animals, although aadA13 is here firstly described in Morganella morganii. These results reinforce the relevance of human commensal flora as reservoir of clinically relevant antibiotic resistance genes including bla ESBLs, and highly transferable genetic platforms as IncK epidemic plasmids.

The role of the natural environment in the emergence of antibiotic resistance in gram-negative bacteria

During the past 10 years, multidrug-resistant Gram-negative Enterobacteriaceae have become a substantial challenge to infection control. It has been suggested by clinicians that the effectiveness of antibiotics is in such rapid decline that, depending on the pathogen concerned, their future utility can be measured in decades or even years. Unless the rise in antibiotic resistance can be reversed, we can expect to see a substantial rise in incurable infection and fatality in both developed and developing regions. Antibiotic resistance develops through complex interactions, with resistance arising by de-novo mutation under clinical antibiotic selection or frequently by acquisition of mobile genes that have evolved over time in bacteria in the environment. The reservoir of resistance genes in the environment is due to a mix of naturally occurring resistance and those present in animal and human waste and the selective effects of pollutants, which can co-select for mobile genetic elements carrying multiple resistant genes. Less attention has been given to how anthropogenic activity might be causing evolution of antibiotic resistance in the environment. Although the economics of the pharmaceutical industry continue to restrict investment in novel biomedical responses, action must be taken to avoid the conjunction of factors that promote evolution and spread of antibiotic resistance.

CTX-M-type β-lactamases: a successful story of antibiotic resistance

Production of extended-spectrum β-lactamases (ESBLs) is the principal mechanism of resistance to oxyimino-cephalosporins evolved by members of the family Enterobacteriaceae. Among the several ESBLs emerged among clinical pathogens, the CTX-M-type enzymes have proved the most successful in terms of promiscuity and diffusion in different epidemiological settings, where they have largely replaced and outnumbered other types of ESBLs. Originated by the capture and mobilization of chromosomal β-lactamase genes of strains of Kluyvera species, the blaCTX-M genes have become associated with a variety of mobile genetic elements that have mediated rapid and efficient inter-replicon and cell-to-cell dissemination involving highly successful enterobacterial lineages (e.g. Escherichia coli ST131 and ST405, or Klebsiella pneumoniae CC11 and ST147) to yield high-risk multiresistant clones that have spread on a global scale. The CTX-Mβ-lactamase lineage exhibits a striking plasticity, with a large number of allelic variants belonging in several sublineages, which can be associated with functional heterogeneity of clinical relevance. This review article provides an update on CTX-M-type ESBLs, with focus on structural and functional diversity, epidemiology and clinical significance.

Antibiotic resistance shaping multi-level population biology of bacteria

Antibiotics have natural functions, mostly involving cell-to-cell signaling networks. The anthropogenic production of antibiotics, and its release in the microbiosphere results in a disturbance of these networks, antibiotic resistance tending to preserve its integrity. The cost of such adaptation is the emergence and dissemination of antibiotic resistance genes, and of all genetic and cellular vehicles in which these genes are located. Selection of the combinations of the different evolutionary units (genes, integrons, transposons, plasmids, cells, communities and microbiomes, hosts) is highly asymmetrical. Each unit of selection is a self-interested entity, exploiting the higher hierarchical unit for its own benefit, but in doing so the higher hierarchical unit might acquire critical traits for its spread because of the exploitation of the lower hierarchical unit. This interactive trade-off shapes the population biology of antibiotic resistance, a composed-complex array of the independent "population biologies." Antibiotics modify the abundance and the interactive field of each of these units. Antibiotics increase the number and evolvability of "clinical" antibiotic resistance genes, but probably also many other genes with different primary functions but with a resistance phenotype present in the environmental resistome. Antibiotics influence the abundance, modularity, and spread of integrons, transposons, and plasmids, mostly acting on structures present before the antibiotic era. Antibiotics enrich particular bacterial lineages and clones and contribute to local clonalization processes. Antibiotics amplify particular genetic exchange communities sharing antibiotic resistance genes and platforms within microbiomes. In particular human or animal hosts, the microbiomic composition might facilitate the interactions between evolutionary units involved in antibiotic resistance. The understanding of antibiotic resistance implies expanding our knowledge on multi-level population biology of bacteria.

Extended-spectrum cephalosporin-resistant Gram-negative organisms in livestock: an emerging problem for human health?

Escherichia coli, Salmonella spp. and Acinetobacter spp. are important human pathogens. Serious infections due to these organisms are usually treated with extended-spectrum cephalosporins (ESCs). However, in the past two decades we have faced a rapid increasing of infections and colonization caused by ESC-resistant (ESC-R) isolates due to production of extended-spectrum-β-lactamases (ESBLs), plasmid-mediated AmpCs (pAmpCs) and/or carbapenemase enzymes. This situation limits drastically our therapeutic armamentarium and puts under peril the human health. Animals are considered as potential reservoirs of multidrug-resistant (MDR) Gram-negative organisms. The massive and indiscriminate use of antibiotics in veterinary medicine has contributed to the selection of ESC-R E. coli, ESC-R Salmonella spp. and, to less extent, MDR Acinetobacter spp. among animals, food, and environment. This complex scenario is responsible for the expansion of these MDR organisms which may have life-threatening clinical significance. Nowadays, the prevalence of food-producing animals carrying ESC-R E. coli and ESC-R Salmonella (especially those producing CTX-M-type ESBLs and the CMY-2 pAmpC) has reached worryingly high values. More recently, the appearance of carbapenem-resistant isolates (i.e., VIM-1-producing Enterobacteriaceae and NDM-1 or OXA-23-producing Acinetobacter spp.) in livestock has even drawn greater concerns. In this review, we describe the aspects related to the spread of the above MDR organisms among pigs, cattle, and poultry, focusing on epidemiology, molecular mechanisms of resistance, impact of antibiotic use, and strategies to contain the overall problem. The link and the impact of ESC-R organisms of livestock origin for the human scenario are also discussed.

Comparable high rates of extended-spectrum-beta-lactamase-producing Escherichia coli in birds of prey from Germany and Mongolia

Frequent contact with human waste and liquid manure from intensive livestock breeding, and the increased loads of antibiotic-resistant bacteria that result, are believed to be responsible for the high carriage rates of ESBL-producing E. coli found in birds of prey (raptors) in Central Europe. To test this hypothesis against the influence of avian migration, we initiated a comparative analysis of faecal samples from wild birds found in Saxony-Anhalt in Germany and the Gobi-Desert in Mongolia, regions of dissimilar human and livestock population characteristics and agricultural practices. We sampled a total of 281 wild birds, mostly raptors with primarily north-to-south migration routes. We determined antimicrobial resistance, focusing on ESBL production, and unravelled the phylogenetic and clonal relatedness of identified ESBL-producing E. coli isolates using multi-locus sequence typing (MLST) and macrorestriction analyses. Surprisingly, the overall carriage rates (approximately 5%) and the proportion of ESBL-producers among E. coli (Germany: 13.8%, Mongolia: 10.8%) were similar in both regions. Whereas bla(CTX-M-1) predominated among German isolates (100%), bla(CTX-M-9) was the most prevalent in Mongolian isolates (75%). We identified sequence types (STs) that are well known in human and veterinary clinical ESBL-producing E. coli (ST12, ST117, ST167, ST648) and observed clonal relatedness between a Mongolian avian ESBL-E. coli (ST167) and a clinical isolate of the same ST that originated in a hospitalised patient in Europe. Our data suggest the influence of avian migratory species in the transmission of ESBL-producing E. coli and challenge the prevailing assumption that reducing human influence alone invariably leads to lower rates of antimicrobial resistance.

Clonal diversity of ESBL-producing Escherichia coli in pigs at slaughter level in Portugal

We aimed to determine the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in fecal samples of healthy pigs, and to evaluate their clonality and associated resistance. Forty-nine percent of pigs sampled (n=35/71) in a slaughterhouse in Portugal revealed ESBL-producing E. coli isolates. Most isolates produced CTX-M-1 enzyme (71.4%; n=25/35), followed by CTX-M-9 (11.4%; n=4/35), CTX-M-14 (5.7%; n=2/35), SHV-12 (5.7%; n=2/35), and CTX-M-32 (5.7%; n=2/35). Ninety-four percent of the isolates presented a phenotype of multi-resistance. Most isolates belonged to phylogroups B1 (42.8%; n=15/35) and A (40%; n=14/35). Multilocus sequence typing (MLST) analysis revealed nine sequence types (STs) under six clonal complexes (CCs) and nine singletons, including overrepresentation of CC10 and three new STs (ST2524, ST2525, ST2528). We observed the frequent presence of CTX-M-producing E. coli in pigs at slaughter level, most of them belonging to CC10, commonly recovered from clinical samples.

Chicken as reservoir for extraintestinal pathogenic Escherichia coli in humans, Canada

Urinary tract infections can be difficult and expensive to treat. Most (85%) are caused by bacteria called E. coli. Historically, doctors have believed that these urinary tract E. coli came from the patient’s own intestines. But recently, Canadian researchers discovered that not only can these E. coli come from outside the patient’s intestines, they can actually come from outside the patient: from food. After comparing the genetic makeup of E. coli from human urinary tract infections with E. coli from retail meat (chicken, beef, and pork), they concluded that chickens are a likely source of E. coli and that the infections probably come directly from the chickens themselves, not from human contamination during food processing. Therefore, prevention of E. coli urinary tract infections in people might need to start on chicken farms.

We previously described how retail meat, particularly chicken, might be a reservoir for extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections (UTIs) in humans. To rule out retail beef and pork as potential reservoirs, we tested 320 additional E. coli isolates from these meats. Isolates from beef and pork were significantly less likely than those from chicken to be genetically related to isolates from humans with UTIs. We then tested whether the reservoir for ExPEC in humans could be food animals themselves by comparing geographically and temporally matched E. coli isolates from 475 humans with UTIs and from cecal contents of 349 slaughtered animals. We found genetic similarities between E. coli from animals in abattoirs, principally chickens, and ExPEC causing UTIs in humans. ExPEC transmission from food animals could be responsible for human infections, and chickens are the most probable reservoir.

A degenerate primer MOB typing (DPMT) method to classify gamma-proteobacterial plasmids in clinical and environmental settings

Transmissible plasmids are responsible for the spread of genetic determinants, such as antibiotic resistance or virulence traits, causing a large ecological and epidemiological impact. Transmissible plasmids, either conjugative or mobilizable, have in common the presence of a relaxase gene. Relaxases were previously classified in six protein families according to their phylogeny. Degenerate primers hybridizing to coding sequences of conserved amino acid motifs were designed to amplify related relaxase genes from γ-Proteobacterial plasmids. Specificity and sensitivity of a selected set of 19 primer pairs were first tested using a collection of 33 reference relaxases, representing the diversity of γ-Proteobacterial plasmids. The validated set was then applied to the analysis of two plasmid collections obtained from clinical isolates. The relaxase screening method, which we call “Degenerate Primer MOB Typing” or DPMT, detected not only most known Inc/Rep groups, but also a plethora of plasmids not previously assigned to any Inc group or Rep-type.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Molecular and phenotypic characterisation of extended spectrum β-lactamase CTX-M Escherichia coli from farm animals in Great Britain

The aim of this study was to characterise CTX-M Escherichia coli isolates from cattle, chickens and turkeys in Great Britain with respect to CTX-M sequence type, replicon type, ability to transfer plasmids, and for the presence of antibiotic resistance, fitness and virulence genes as determined by micro-arrays. The main CTX-M enzymes identified in E. coli from cattle, chicken and turkeys were 14 and 15, 1 and 15, and 1 and 14 respectively. Most isolates from different animal species transferred their plasmids with similar frequencies. The plasmid replicon type I1-λ was most common and seen in 23%, 95% and 50% of the isolates tested from cattle, chickens and turkeys respectively, whilst types F, FIA, FIB and K were common to isolates from cattle and turkeys only. Thirty-eight different antibiotic resistance genes were detected by micro-array including aad genes, blaCTX-M, blaTEM, cat genes dfrA, floR, strA, strB, sul, sul2 tetA and tetB. Thirty-nine different fitness and virulence genes were also detected by-micro-array, including espP, ireA, lpfA, mchF, prfB and tsh. Fisher exact test and hierarchical clustering of the antibiotic resistance and virulence gene results showed some genes were more commonly associated with isolates from chickens or cattle. This study provides a baseline of the characteristics of CTX-M E. coli isolates from animals in Great Britain and suggests that chicken and cattle CTX-M E. coli represent different populations.

Detection and characterization of pCT-like plasmid vectors for blaCTX-M-14 in Escherichia coli isolates from humans, turkeys and cattle in England and Wales

OBJECTIVES

To detect and characterize Escherichia coli strains and pCT-like plasmids implicated in the dissemination of the CTX-M-14 gene in animals and humans, in England and Wales.

METHODS

UK CTX-M-14-producing E. coli (n=70) from cattle (n=33), turkeys (n=9), sheep (n=2) and humans (n=26) were screened using multiplex PCR for the detection of a previously characterized plasmid, pCT. Isolates found to be carrying two or more pCT genetic markers were further analysed using PFGE. Their antimicrobial-resistance genes and virulence genes were also determined. These plasmids were transferred to Salmonella enterica serotype Typhimurium 26R and further examined for incompatibility type, genetic environment of the bla(CTX-M-14) gene, size, restriction fragment length polymorphism (RFLP) and nikB sequence.

RESULTS

The 25 E. coli isolates carrying pCT genetic markers generated 19 different PFGE profiles, and 23 isolates had different virulence and antimicrobial-resistance gene patterns. One isolate from cattle was a verotoxigenic E. coli ('VTEC'); the rest were commensal or extra-intestinal pathogenic E. coli. pCT-like plasmids with similar molecular characteristics (size, replicon type, RFLP pattern, pCT markers and genetic environment of the bla(CTX-M-14) gene) were detected in 21/25 of the field isolates, which comprised those from cattle (n=9), turkeys (n=8) and humans (n=4). All pCT-like plasmids were conjugative, and most were IncK (n=21) and had the same local genetic environment flanking the bla(CTX-M-14) gene (n=23). RFLP analysis demonstrated ≥ 75% similarity among most plasmids (n=22).

CONCLUSIONS

pCT-like plasmids were common vectors for horizontal dissemination of 30% of the bla(CTX-M-14) genes to different E. coli isolates from humans, cattle and turkeys.

CTX-M Enzymes: Origin and Diffusion

CTX-M β-lactamases are considered a paradigm in the evolution of a resistance mechanism. Incorporation of different chromosomal bla_CTX-M related genes from different species of Kluyvera has derived in different CTX-M clusters. In silico analyses have shown that this event has occurred at least nine times; in CTX-M-1 cluster (3), CTX-M-2 and CTX-M-9 clusters (2 each), and CTX-M-8 and CTX-M-25 clusters (1 each). This has been mainly produced by the participation of genetic mobilization units such as insertion sequences (ISEcp1 or ISCR1) and the later incorporation in hierarchical structures associated with multifaceted genetic structures including complex class 1 integrons and transposons. The capture of these bla_CTX-M genes from the environment by highly mobilizable structures could have been a random event. Moreover, after incorporation within these structures, β-lactam selective force such as that exerted by cefotaxime and ceftazidime has fueled mutational events underscoring diversification of different clusters. Nevertheless, more variants of CTX-M enzymes, including those not inhibited by β-lactamase inhibitors such as clavulanic acid (IR-CTX-M variants), only obtained under in in vitro experiments, are still waiting to emerge in the clinical setting. Penetration and the later global spread of CTX-M producing organisms have been produced with the participation of the so-called “epidemic resistance plasmids” often carried in multi-drug resistant and virulent high-risk clones. All these facts but also the incorporation and co-selection of emerging resistance determinants within CTX-M producing bacteria, such as those encoding carbapenemases, depict the currently complex pandemic scenario of multi-drug resistant isolates.

Dissemination of pCT-like IncK plasmids harboring CTX-M-14 extended-spectrum β-lactamase among clinical Escherichia coli isolates in the United Kingdom

IncK plasmids encoding CTX-M-14 extended-spectrum β-lactamase (ESBL) and highly related to plasmid pCT were detected in 13 of 67 (19%) human clinical isolates of Escherichia coli with a group 9 CTX-M-type ESBL from the United Kingdom and in 2 quality assurance isolates. None of these E. coli strains was related to the cattle strain from which pCT was originally characterized.

Iberian wolf as a reservoir of extended-spectrum β-lactamase-producing Escherichia coli of the TEM, SHV, and CTX-M groups

The intensive use of antibiotics in human and veterinary medicine, associated with mechanisms of bacterial genetic transfer, caused a selective pressure that contributed to the dissemination of antimicrobial resistance in different bacteria groups and throughout different ecosystems. Iberian wolf, due to his predatory and wild nature, may serve as an important indicator of environmental contamination with antimicrobial resistant bacteria. The aim of this study was to characterize the diversity of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates within the fecal microbiota of Iberian wolf. Additionally, the identification of other associated resistance genes, phylogenetic groups, and the detection of virulence determinants were also focused on in this study. From 2008 to 2009, 237 fecal samples from Iberian wolf were collected in Portugal. E. coli isolates with TEM-52, SHV-12, CTX-M-1, and CTX-M-14-type ESBLs were detected in 13 of these samples (5.5%). This study reveals the presence of ESBL-producing E. coli isolates, in a wild ecosystem, which could be disseminated through the environment. Moreover, the presence of resistant genes in integrons and the existence of virulence determinants were shown. The association between antibiotic resistance and virulence determinants should be monitored, as it constitutes a serious public health problem.

Extended-Spectrum Beta-Lactamases Producing E. coli in Wildlife, yet Another Form of Environmental Pollution?

Wildlife is normally not exposed to clinically used antimicrobial agents but can acquire antimicrobial resistant bacteria through contact with humans, domesticated animals and the environment, where water polluted with feces seems to be the most important vector. Escherichia coli, an ubiquitous commensal bacterial species colonizing the intestinal tract of mammals and birds, is also found in the environment. Extended-spectrum beta-lactamases producing E. coli (ESBL-E. coli) represent a major problem in human and veterinary medicine, particular in nosocomial infections. Additionally an onset of community-acquired ESBL-E. coli infections and an emergence in livestock farming has been observed in recent years, suggesting a successful transmission as well as persistence of ESBL-E. coli strains outside clinical settings. Another parallel worldwide phenomenon is the spread of ESBL-E. coli into the environment beyond human and domesticated animal populations, and this seems to be directly influenced by antibiotic practice. This might be a collateral consequence of the community-onset of ESBL-E. coli infections but can result (a) in a subsequent colonization of wild animal populations which can turn into an infectious source or even a reservoir of ESBL-E. coli, (b) in a contribution of wildlife to the spread and transmission of ESBL-E. coli into fragile environmental niches, (c) in new putative infection cycles between wildlife, domesticated animals and humans, and (d) in problems in the medical treatment of wildlife. This review aims to summarize the current knowledge on ESBL-E. coli in wildlife, in turn underlining the need for more large scale investigations, in particular sentinel studies to monitor the impact of multiresistant bacteria on wildlife.

Molecular epidemiology over an 11-year period (2000 to 2010) of extended-spectrum β-lactamase-producing Escherichia coli causing bacteremia in a centralized Canadian region

A study was designed to assess the importance of sequence types among extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates causing bacteremia over an 11-year period (2000 to 2010) in a centralized Canadian region. A total of 197 patients with incident infections were identified; the majority presented with community-onset urosepsis, with a significant increase in the prevalence of ESBL-producing E. coli during the later part of the study. The majority of E. coli isolates produced either CTX-M-15 or CTX-M-14. We identified 7 different major sequence types among 91% of isolates (i.e., the ST10 clonal complex, ST38, ST131, ST315, ST393, ST405, and ST648) and provided insight into their clinical and molecular characteristics. ST38 was the most antimicrobial-susceptible sequence type and predominated during 2000 to 2004 but disappeared after 2008. ST131 was the most antimicrobial-resistant sequence type, and the influx of a single pulsotype of this sequence type was responsible for the significant increase of ESBL-producing E. coli strains since 2007. During 2010, 49/63 (78%) of the ESBL-producing E. coli isolates belonged to ST131, and this sequence type had established itself as a major drug-resistant pathogen in Calgary, Alberta, Canada, posing an important new public health threat within our region. We urgently need well-designed epidemiological and molecular studies to understand the dynamics of transmission, risk factors, and reservoirs for E. coli ST131. This will provide insight into the emergence and spread of this multiresistant sequence type.

Detection of extended-spectrum beta-lactamase-producing Escherichia coli isolates in faecal samples of Iberian lynx

AIMS

To characterize the diversity of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates recovered within the faecal microbiota of Iberian lynx. The identification of other associated resistance genes and the analysis of clonal relationship were also focused in this study.

METHODS AND RESULTS

From 2008 to 2010, 128 faecal samples of Iberian lynx (wild and captive animals) were collected. Eleven tested samples contained cefotaxime-resistant E. coli isolates (all belonging to captive animals) and 10 ESBL-producing isolates were showed. CTX-M-14 and SHV-12 ESBL-types were detected and seven different patterns were identified by pulsed-field gel electrophoresis analysis.

CONCLUSIONS

The occurrence of unrelated multiresistant E. coli in faecal flora of captive specimens of Iberian lynx, including the presence of ESBLs, resistant genes in integrons and virulence determinants was showed in this study.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results obtained in this study highlight the environmental problem as future reintroductions of Iberian lynx could lead to a spread of resistant bacteria. Additionally, ESBL-producing bacteria can represent a health problem for this endangered species.

Extended-spectrum-β-lactamase-producing Escherichia coli as a cause of pediatric infections: report of a neonatal intensive care unit outbreak due to a CTX-M-14-producing strain

Little information is available about pediatric infections caused by extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli. We characterized an outbreak caused by a CTX-M-14-producing E. coli isolate in a neonatal intensive care unit (NICU) and studied other infections caused by ESBL-producing E. coli in non-NICU pediatric units. All children ≤4 years old who were infected or colonized by ESBL-producing E. coli isolates between January 2009 and September 2010 were included. Molecular epidemiology was studied by phylogroup analysis, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing. Antibiotic resistance genes were analyzed by PCR and sequencing. Plasmids were studied by PFGE with S1 nuclease digestion and by incompatibility group analysis using a PCR-based replicon-typing scheme. Of the ESBL-producing E. coli isolates colonizing or infecting the 30 newborns, identical PFGE results were observed for 21 (70%) isolates, which were classified as CTX-M-14-producing E. coli of ST23 phylogroup A. bla(CTX-M-14a) was linked to ISEcp1 and was carried on an ∼80-bp IncK plasmid. A smaller ongoing outbreak due to SHV-12-producing ST131 E. coli was also identified in the same NICU. Fifteen additional infections with ESBL-producing E. coli were identified in non-NICU pediatric units, but none was caused by the CTX-M-14-producing E. coli epidemic clone. Overall, CTX-M-14 (71.1%), CTX-M-15 (13.3%), and SHV-12 (13.3%) were the most important ESBLs causing pediatric infections in this study. Infections of newborns with CTX-M-14-producing E. coli were caused by both clonal and nonclonal isolates.

CTX-M-14 type β-Lactamase producing Escherichia coli isolated from hospitalized patients in Tunisia

Escherichia coli (E.coli) with a CTX-M resistance phenotype was selected from hospitalized patients in a university Hospital of Tunisia between January 2010 and June 2010. PCR analysis and sequencing demonstrated that it harboured CTX-M-14 β-lactamase. Characterization of the regions surrounding the bla(CTX-M-14) showed the ISEcp1 elements located in the upstream region of the bla gene. PFGE and multilocus sequence typing revealed two different types which corresponds to sequence types ST38 complex and ST131. These results reinforce the potential for spreading of this gene among E. coli clinical strains in the coming years in Tunisia.

Identification of bacterial plasmids based on mobility and plasmid population biology

Plasmids contain a backbone of core genes that remains relatively stable for long evolutionary periods, making sense to speak about plasmid species. The identification and characterization of the core genes of a plasmid species has a special relevance in the study of its epidemiology and modes of transmission. Besides, this knowledge will help to unveil the main routes that genes, for example antibiotic resistance (AbR) genes, use to travel from environmental reservoirs to human pathogens. Global dissemination of multiple antibiotic resistances and virulence traits by plasmids is an increasing threat for the treatment of many bacterial infectious diseases. To follow the dissemination of virulence and AbR genes, we need to identify the causative plasmids and follow their path from reservoirs to pathogens. In this review, we discuss how the existing diversity in plasmid genetic structures gives rise to a large diversity in propagation strategies. We would like to propose that, using an identification methodology based on plasmid mobility types, we can follow the propagation routes of most plasmids in Gammaproteobacteria, as well as their cargo genes, in complex ecosystems. Once the dissemination routes are known, designing antidissemination drugs and testing their efficacy will become feasible. We discuss in this review how the existing diversity in plasmid genetic structures gives rise to a large diversity in propagation strategies. We would like to propose that, by using an identification methodology based on plasmid mobility types, we can follow the propagation routes of most plasmids in ?-proteobacteria, as well as their cargo genes, in complex ecosystems.

Complete sequence and molecular epidemiology of IncK epidemic plasmid encoding blaCTX-M-14

This plasmid is disseminated worldwide in Escherichia coli isolated from humans and animals.

Antimicrobial drug resistance is a global challenge for the 21st century with the emergence of resistant bacterial strains worldwide. Transferable resistance to β-lactam antimicrobial drugs, mediated by production of extended-spectrum β-lactamases (ESBLs), is of particular concern. In 2004, an ESBL-carrying IncK plasmid (pCT) was isolated from cattle in the United Kingdom. The sequence was a 93,629-bp plasmid encoding a single antimicrobial drug resistance gene, bla_CTX-M-14. From this information, PCRs identifying novel features of pCT were designed and applied to isolates from several countries, showing that the plasmid has disseminated worldwide in bacteria from humans and animals. Complete DNA sequences can be used as a platform to develop rapid epidemiologic tools to identify and trace the spread of plasmids in clinically relevant pathogens, thus facilitating a better understanding of their distribution and ability to transfer between bacteria of humans and animals.

Potential pathogenicity and host range of extended-spectrum beta-lactamase-producing Escherichia coli isolates from healthy poultry

Thirty of 33 epidemiologically unrelated extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates from healthy poultry lacked the virulence genes commonly associated with human-pathogenic strains. The main zoonotic risk is associated with the broad host range of avian E. coli belonging to sequence type complex 10 and of IncN and IncI1 plasmids carrying bla(CTX-M) or bla(SHV).

Analysis of antibiotic resistance regions in Gram-negative bacteria

Antibiotic resistance in Gram-negative bacteria is often due to the acquisition of resistance genes from a shared pool. In multiresistant isolates these genes, together with associated mobile elements, may be found in complex conglomerations on plasmids or on the chromosome. Analysis of available sequences reveals that these multiresistance regions (MRR) are modular, mosaic structures composed of different combinations of components from a limited set arranged in a limited number of ways. Components common to different MRR provide targets for homologous recombination, allowing these regions to evolve by combinatorial evolution, but our understanding of this process is far from complete. Advances in technology are leading to increasing amounts of sequence data, but currently available automated annotation methods usually focus on identifying ORFs and predicting protein function by homology. In MRR, where the genes are often well characterized, the challenge is to identify precisely which genes are present and to define the boundaries of complete and fragmented mobile elements. This review aims to summarize the types of mobile elements involved in multiresistance in Gram-negative bacteria and their associations with particular resistance genes, to describe common components of MRR and to illustrate methods for detailed analysis of these regions.

CTX-M-14 β-lactamase-producing Citrobacter freundii isolated in Venezuela

A clinical isolate of C. freundii with reduced susceptibility to extended-spectrum β-lactams from a woman with cystocele associated with recurrent urinary tract infection was analyzed. Susceptibility tests, double disk synergy tests (DDST) and enzymatic activity by the agar iodometric method suggested the presence of ESBLs. Conjugation experiments revealed the presence of a large conjugative plasmid (pLM07/20) with an exclusive FrepB replicon type (IncF/FIB). PCR analysis and sequencing confirmed the presence of the bla_CTX-M-14 gene in the pLM07/20 from C. freundii.LM07/10. Although this is the first report of CTX-M-14 in Venezuela, we alert the medical community that future increase of these β-lactamases in our city could be due to dissemination of plasmids into bacterial populations.

Molecular characterization and antimicrobial susceptibility testing of Escherichia coli isolates from patients with urinary tract infections in 20 Chinese hospitals

A total of 222 urinary Escherichia coli isolates from 20 tertiary hospitals in 15 different provinces and 4 municipalities in mainland China were characterized by antimicrobial susceptibility, phylogrouping, and the presence of plasmid-mediated quinolone resistance genes. A subset of 138 suspected extended-spectrum cephalosporinase (ESC) producers were examined for genes encoding cephalosporin resistance. Forty-three isolates harboring bla(CTX-M-14) or bla(CTX-M-15) were analyzed by pulsed-field gel electrophoresis (PFGE), and plasmids containing these genes were typed using PCR-based replicon typing (PBRT). Thirteen phylogroup B2 bla(CTX-M-14)- and bla(CTX-M-15)-positive isolates were analyzed by multilocus sequence typing (MLST). A frequent occurrence of resistance (>46%) was observed toward cephalosporins, gentamicin, and fluoroquinolones. Among the 222 isolates, 4 qnrS1, 4 qepA, and 16 aac(6')-Ib-cr genes were confirmed. Four major phylogroups (A, B1, B2, and D) and nontypeable isolates (NTs) were found among the isolates, with phylogroup D (54%) being the most common phylogroup. A total of 110 (80%) of the 138 screened isolates harbored bla(CTX-M) genes, with bla(CTX-M-14) (71%) and bla(CTX-M-15) (24%) being the most prevalent of these genes. Nine of the 13 CTX-M-15- or CTX-M-14-containing B2 isolates belonged to ST131. PFGE typing showed a high level of diversity, and plasmid analysis indicated a very large pool of different resistance plasmids mediating the spread of bla(CTX-M) genes in mainland China. An equally very high frequency of resistance and equally high levels of diversity in phylogroups, PFGE types, and plasmids were observed among community- and hospital-acquired E. coli isolates, indicating the presence of a large reservoir in the community and a long-term spread of cephalosporin resistance in China.

Multiresistant Gram-negative bacteria: the role of high-risk clones in the dissemination of antibiotic resistance

Multilocus sequence typing reveals that many bacterial species have a clonal structure and that some clones are widespread. This underlying phylogeny was not revealed by pulsed-field gel electrophoresis, a method better suited to short-term outbreak investigation. Some global clones are multiresistant and it is easy to assume that these have disseminated from single foci. Such conclusions need caution, however, unless there is a clear epidemiological trail, as with KPC carbapenemase-positive Klebsiella pneumoniae ST258 from Greece to northwest Europe. Elsewhere, established clones may have repeatedly and independently acquired resistance. Thus, the global ST131 Escherichia coli clone most often has CTX-M-15 extended-spectrum β-lactamase (ESBL), but also occurs without ESBLs and as a host of many other ESBL types. We explore this interaction of clone and resistance for E. coli, K. pneumoniae, Acinetobacter baumannii- a species where three global lineages dominate--and Pseudomonas aeruginosa, which shows clonal diversity, but includes the relatively 'tight' serotype O12/Burst Group 4 cluster that has proved adept at acquiring resistances--from PSE-1 to VIM-1 β-lactamases--for over 20 years. In summary, 'high-risk clones' play a major role in the spread of resistance, with the risk lying in their tenacity--deriving from poorly understood survival traits--and a flexible ability to accumulate and switch resistance, rather than to constant resistance batteries.

Association of composite IS26-sul3 elements with highly transmissible IncI1 plasmids in extended-spectrum-beta-lactamase-producing Escherichia coli clones from humans

The association of an IS440-sul3 platform with Tn21 class 1 integrons carried by IncI1 plasmids encoding extended-spectrum β-lactamases (ESBLs; mainly SHV-12 and CTX-M-14) among worldwide Escherichia coli clones of phylogroups A (ST10, ST23, and ST46), B1 (ST155, ST351, and ST359), and D/B2 (ST131) is reported. An in silico comparative analysis of sul3 elements available in the GenBank database shows the evolution of sul3 platforms by hosting different transposable elements facilitating the potential genesis of IS26 composite transposons and further insertion element-mediated promoted arrangements.