Genetic background of Escherichia coli and extended-spectrum beta-lactamase type

Characterization of avian pathogenic Escherichia coli isolates based on biofilm formation, ESBL production, virulence-associated genes, and phylogenetic groups

Escherichia coli is a part of both animal and human commensal microbiota. Avian pathogenic E. coli (APEC) is responsible for colibacillosis in poultry, an economically important disease. However, the close similarities among APEC isolates make it difficult to differentiate between pathogenic and commensal bacteria. The aim of this study was to determine phenotypic and molecular characteristics of APEC isolates and to compare them with their in vivo pathogenicity indices. A total of 198 APEC isolates were evaluated for their biofilm-producing ability and extended-spectrum β-lactamase (ESBL) production phenotypes. In addition, 36 virulence-associated genes were detected, and the isolates were classified into seven phylogenetic groups using polymerase chain reaction. The sources of the isolates were not associated with biofilms, ESBL, genes, or phylogroups. Biofilm and ESBL production were not associated with pathogenicity. Group B2 had the highest pathogenicity index. Groups B2 and E were positively associated with high-pathogenicity isolates and negatively associated with low-pathogenicity isolates. In contrast, groups A and C were positively associated with apathogenic isolates, and group B1 was positively associated with low-pathogenicity isolates. Some virulence-associated genes showed positive or negative associations with specific phylogenetic groups. None of the individual techniques produced results that correlated with the in vivo pathogenicity index. However, the combination of two techniques, namely, detection of virulence-associated genes and the phylogenetic groups, could help the classification of the isolates as pathogenic or commensal.

Comparison of Cefotaxime-Resistant Escherichia coli and sul1 and intI1 by qPCR for Monitoring of Antibiotic Resistance of Wastewater, Surface Water, and Recycled Water

Awareness of the need for surveillance of antimicrobial resistance (AMR) in water environments is growing, but there is uncertainty regarding appropriate monitoring targets. Adapting culture-based fecal indicator monitoring to include antibiotics in the media provides a potentially low-tech and accessible option, while quantitative polymerase chain reaction (qPCR) targeting key genes of interest provides a broad, quantitative measure across the microbial community. The purpose of this study was to compare findings obtained from the culture of cefotaxime-resistant (cefR) Escherichia coli with two qPCR methods for quantification of antibiotic resistance genes across wastewater, recycled water, and surface waters. The culture method was a modification of US EPA Method 1603 for E. coli, in which cefotaxime is included in the medium to capture cefR strains, while qPCR methods quantified sul1 and intI1. A common standard operating procedure for each target was applied to samples collected by six water utilities across the United States and processed by two laboratories. The methods performed consistently, and all three measures reflected the same overarching trends across water types. The qPCR detection of sul1 yielded the widest dynamic range of measurement as an AMR indicator (7-log versus 3.5-log for cefR E. coli), while intI1 was the most frequently detected target (99% versus 96.5% and 50.8% for sul1 and cefR E. coli, respectively). All methods produced comparable measurements between labs (p < 0.05, Kruskal-Wallis). Further study is needed to consider how relevant each measure is to capturing hot spots for the evolution and dissemination of AMR in the environment and as indicators of AMR-associated human health risk.

Clonal Complexes 23, 10, 131 and 38 as Genetic Markers of the Environmental Spread of Extended-Spectrum β-Lactamase (ESBL)-Producing E. coli

In accordance with the global action plan on antimicrobial resistance adopted by the World Health Assembly in 2015, there is a need to develop surveillance programs for antimicrobial resistant bacteria. In this context, we have analyzed the clonal diversity of Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli) isolated from aquatic environments and human and food samples in Spain, with the aim of determining possible clonal complexes (CCs) that act as markers of the potential risk of transmission of these resistant bacteria. The phylogenetic groups, sequence types (STs) and CCs were determined by different Polymerase Chain Reaction (PCR) and Multilocus Sequence Typing (MLST) techniques. Phylogroup A was prevalent and was mainly present in food and water strains, while human strains were mostly associated with phylogroup B2. According to the observed prevalence in the different niches, CC23 and CC10 are proposed as markers of phylogroups A and C, related with the spread of bla_CTX-M1 and bla_CTX-M15 genes. Similarly, CC131 and CC38 could be associated to the dissemination of pathogenic strains (phylogroups B2 and D) carrying mainly bla_CTX-M14 and bla_CTX-M15 genes. Some strains isolated from wastewater treatment plants (WWTPs) showed identical profiles to those isolated from other environments, highlighting the importance that water acquires in the dissemination of bacterial resistance. In conclusion, the detection of these genetic markers in different environments could be considered as an alert in the spread of ESBL.

Similarities in Virulence and Extended Spectrum Beta-Lactamase Gene Profiles among Cefotaxime-Resistant Escherichia coli Wastewater and Clinical Isolates

The World Health Organization has identified antibiotic resistance as one of the largest threats to human health and food security. In this study, we compared antibiotic resistance patterns between ESBL-producing Escherichia coli from human clinical diseases and cefotaxime-resistant environmental strains, as well as their potential to be pathogenic. Antibiotic susceptibility was tested amongst clinical isolates (n = 11), hospital wastewater (n = 22), and urban wastewater (n = 36, both influent and treated effluents). Multi-drug resistance predominated (>70%) among hospitalwastewater and urban wastewater influent isolates. Interestingly, isolates from clinical and urban treated effluents showed similar multi-drug resistance rates (~50%). Most hospital wastewater isolates were Phylogroup A, while clinical isolates were predominately B2, with a more diverse phylogroup population in urban wastewater. ESBL characterization of cefotaxime-resistant populations identified blaCTX-M-1 subgroup as the most common, whereby blaKPC was more associated with ceftazidime and ertapenem resistance. Whole-genome sequencing of a carbapenemase-producing hospital wastewater E. coli strain revealed plasmid-mediated blaKPC-2. Among cefotaxime-resistant populations, over 60% of clinical and 30% of treated effluent E. coli encoded three or more virulence genes exhibiting a pathogenic potential. Together, the similarity among treated effluent E. coli populations and clinical strains suggest effluents could serve as a reservoir for future multi-drug resistant E. coli clinical infections.

Prevalence and molecular characterization of extended-spectrum β-lactamase (ESBL) producing Escherichia coli isolated from dogs suffering from diarrhea in and around Kolkata

BACKGROUND

Dogs are the favorite companion animals among humans. The close interaction between dogs and people increases the risk of antibiotic resistance spreading. Surveillance for antimicrobial resistance and the identification of ESBL-producing Escherichia coli as an indicator bacterium is an important tool for managing antimicrobial drug therapy.

AIMS

The present study targeted to identify and characterize ESBL-producing E. coli among dogs suffering from diarrhea in and around Kolkata.

METHODS

Isolation and identification of E. coli from dogs suffering from diarrhea (n=70) along with screening for the production of both ESBL and AmpC. The isolates were further characterized through antimicrobial resistance profiling, resistance genes (bla _CTX-M, bla _TEM, and bla _SHV) screening, and phylogenetic group study.

RESULTS

Among the 70 isolates, 21 (30%) were confirmed ESBL producers. An antibiogram typing of ESBL-producing E. coli revealed that the majority of them were resistant to norfloxacin (85.7%) followed by tetracycline (61.90%), doxycycline (57.14%), piperacillin/tazobactam (52.38%), cotrimoxazole (47.62%), gentamicin (42.62%), amikacin (23.81%), and chloramphenicol (19.05%). Major resistance genes included bla _CTX-M (100%), bla _TEM (28.57%), and bla _SHV (9.50%). The predominant phylogenetic groups were phylogroup A (76%) followed by phylogroup D (24%).

CONCLUSION

The current investigation reported a high prevalence of both ESBL and AmpC β-lactamase (AmpC) producing E. coli, co-resistance to a distinct group of antibiotics, and co-existence of different ESBL genes in dogs. Our findings highlight the importance of diagnostic antimicrobial susceptibility testing for proper antimicrobial therapy and to prevent antimicrobial resistance from spreading to humans from dogs in Kolkata and the surrounding area.

Phylum barrier and Escherichia coli intra-species phylogeny drive the acquisition of antibiotic-resistance genes

Escherichia coli is a ubiquitous bacterium that has been widely exposed to antibiotics over the last 70 years. It has adapted by acquiring different antibiotic-resistance genes (ARGs), the census of which we aim to characterize here. To do so, we analysed 70 301 E. coli genomes obtained from the EnteroBase database and detected 1 027 651 ARGs using the AMRFinder, Mustard and ResfinderFG ARG databases. We observed a strong phylogroup and clonal lineage specific distribution of some ARGs, supporting the argument for epistasis between ARGs and the strain genetic background. However, each phylogroup had ARGs conferring a similar antibiotic class resistance pattern, indicating phenotypic adaptive convergence. The G+C content or the type of ARG was not associated with the frequency of the ARG in the database. In addition, we identified ARGs from anaerobic, non-Proteobacteria bacteria in four genomes of E. coli, supporting the hypothesis that the transfer between anaerobic bacteria and E. coli can spontaneously occur but remains exceptional. In conclusion, we showed that phylum barrier and intra-species phylogenetic history are major drivers of the acquisition of a resistome in E. coli.

The Travelling Particles: Investigating microplastics as possible transport vectors for multidrug resistant E. coli in the Weser estuary (Germany)

The prevalence of multidrug-resistant Gram-negative bacteria in aquatic environments has been a long withstanding health concern, namely extended-spectrum beta-lactamase (ESBL) producing Escherichia coli. Given increasing reports on microplastic (MP) pollution in these environments, it has become crucial to better understand the role of MP particles as transport vectors for such multidrug-resistant bacteria. In this study, an incubation experiment was designed where particles of both synthetic and natural material (HDPE, tyre wear, and wood) were sequentially incubated at multiple sites along a salinity gradient from the Lower Weser estuary (Germany) to the offshore island Helgoland (German Bight, North Sea). Following each incubation period, particle biofilms and water samples were assessed for ESBL-producing E. coli, first by the enrichment and detection of E. coli using Fluorocult® LMX Broth followed by cultivation on CHROMAgar™ ESBL media to select for ESBL-producers. Results showed that general E. coli populations were present on the surfaces of wood particles across all sites but none were found to produce ESBLs. Additionally, neither HDPE nor tyre wear particles were found to harbour any E. coli. Conversely, ESBL-producing E. coli were present in surrounding waters from all sites, 64% of which conferred resistances against up to 3 other antibiotic groups, additional to the beta-lactam resistances intrinsic to ESBL-producers. This study provides a first look into the potential of MP to harbour and transport multidrug-resistant E. coli across different environments and the approach serves as an important precursor to further studies on other potentially harmful MP-colonizing species.

Molecular characteristics of extended-spectrum β-lactamase/AmpC-producing Salmonella enterica serovar Virchow isolated from food-producing animals during 2010-2017 in South Korea

Global dissemination of non-typhoidal Salmonella producing extended-spectrum β-lactamase (ESBL) is a public-health concern. Recently, the prevalence of Salmonella spp. resistant to third-generation cephalosporins has been increasing in food-producing animals in Korea. In this study, we investigated resistance mechanisms and molecular characteristics of S. Virchow isolates resistant to extended-spectrum cephalosporins (ESCs). We obtained 265 S. Virchow isolates from fecal and carcasses samples of cattle (n = 2), pigs (n = 7), and chickens (n = 256) during 2010-2017, and observed high ESC-resistance (63.8%, 169/265); most of the resistant isolates (96.4%) were obtained from chickens. ESC-resistant S. Virchow isolates (n = 169) showed significantly higher resistance rates to other antimicrobials (especially aminoglycosides and tetracycline, p-value <0.0001), as well as prevalence of multidrug resistance, than did ESC-susceptible S. Virchow isolates (n = 96). All ESC-resistant S. Virchow produced CTX-M-15-type ESBL (n = 147) and/or CMY-2-type AmpC β-lactamase (n = 23). ESC-resistant S. Virchow represented seven pulsotypes, predominantly composed of type II (58.6%) and III (26.0%), detected in 69 farms in 10 provinces, and 33 farms in 7 provinces, respectively. Genes encoding ESC-resistance were horizontally transferred by conjugation to recipient E. coli J53; this was demonstrated in 28.8% (42/146) of bla_CTX-M-15-positive isolates and in 50.0% (11/22) of bla_CMY-2-positive isolates. All conjugative plasmids carrying bla_CTX-M-15 and bla_CMY-2 genes belonged to ST2-IncHI2 and ST12/CC12-IncI1, respectively. Genetic features of transferred bla genes were involved with ISEcp1 in both bla_CTX-M-15 and bla_CMY-2; ISEcp1 plays a critical role in the efficient capture, expression, and mobilization of bla genes. In addition to bla_CTX-M-15 genes, resistance markers to aminoglycosides and/or tetracycline were co-transferred to recipient E. coli J53. Our results show a high prevalence of ESBL-producing S. Virchow in chickens and chicken carcasses. Specific bla_CTX-M-15 and bla_CMY-2-carrying S. Virchow clones and plasmids were predominant in food-producing animals nationwide. Restriction of antimicrobial use and proper biosecurity practices at the farm level should be urgently implemented in the poultry industry.

MOLECULAR CHARACTERIZATION OF FECAL ESCHERICHIA COLI ISOLATED FROM ZOO ANIMALS

Accredited zoos and animal parks play an important role in animal health research and conservation, providing important insights on matters of public health including zoonotic infectious diseases and antimicrobial resistance (AMR). The emergence and spread of AMR is a complex phenomenon that jeopardizes human and animal health and also threatens the long-term survival of endangered species. The presence of β-lactamases in clinical isolates is particularly significant as they can jeopardize the efficacy of critically important antimicrobials. Although the presence of β-lactamases and extended-spectrum β-lactamases (ESBLs) producing Enterobacteriaceae in zoo animals has been reported, data are not available for northern European countries. In addition, few data are available on phylogenetic grouping of Escherichia coli isolated from zoo animals that can provide additional information on the host-bacterium relationship and on the pathogenicity of isolates. This study aimed to characterize fecal E. coli isolated from 33 healthy zoo animals from 22 species in Ireland, using conventional and molecular microbiological methods. All E. coli isolates were ampicillin resistant, but combined resistance to amoxicillin and clavulanic acid was not detected. Three E. coli isolates sampled from one Amur tiger, one Bornean orangutan, and one Southern white rhino were multidrug resistant, and blaTEM was detected in E. coli recovered from the Amur tiger and the Bornean orangutan. Other β-lactamases, including ESBLs and AmpCs and plasmid-mediated mcr-1 and mcr-2, were not detected. Overall, E. coli isolates investigated were susceptible to the majority of the antimicrobials tested, and only two animals shed E. coli carrying β-lactamase-encoding genes. The majority of isolates belonged to phylogenetic group B1. The screening of the AMR phenotype and genotype of zoo animal E. coli provides useful data that is relevant to antimicrobial stewardship in the zoo veterinary services and relevant to the bank of knowledge needed for tackling AMR.

Class 1 integrons as predominant carriers in Escherichia coli isolates from waterfowls in Hainan, China

This study was conducted to determine the prevalence of integrons and associated gene cassettes in Escherichia coli (E. coli) isolates from waterfowls in Hainan, China. The antimicrobial resistance profile of the isolates was examined by using disc diffusion test. In addition, PCR, RFLP, plasmid replicon typing and DNA sequencing analyses were used for the characterization of integrase genes (class 1, 2 and 3) and associated gene cassettes. Approximatively, 90% of the isolates were positive for the integrase genes by PCR. Specifically, class 1 and class 2 integrons were found in 252 (81%) and 7 (2.3%) strains, respectively. While 21 (6.7%) isolates were positive for both class 1 and class 2 integrons. However, none of the isolate was positive for the class 3 integrons. In addition, 5 various cassette arrays, dfrA1-orfC, aadA2, aadA1, dfrA1-aadA1, and dfrA1-orfC- aadA1, were found within the variable regions (VRs) of class 1 integron isolates. While only single cassette array, dfrA1-sat2- aadA1, was identified within VRs of class 2 integron isolates. We identified incF plasmid as the most common plasmid type, which was detected in 81 of 243 VRs containing isolates. This study is the first report showing the baseline characteristics of integrons in E. coli isolates from waterfowls in Hainan, China. Our results provide evidence of the waterfowl birds as a reservoir of class 1 and class 2 integrons carrying antibiotic resistance gene cassettes. Therefore, strict preventive measures should be taken to avoid the spread of mobile genetic resistance elements in waterfowls in China.

Plasmid Distribution among Escherichia coli from Livestock and Associated Wastewater: Unraveling Factors That Shape the Presence of Genes Conferring Third-Generation Cephalosporin Resistance

A key concern with agricultural wastewater storage ponds is that they may provide an environment conducive for horizontal exchange of antibiotic resistance genes (ARGs), thereby facilitating the emergence of antibiotic resistant pathogens. Central to this exchange are mobile genetic elements like plasmids; yet, the factors shaping their presence in agricultural environments remain poorly understood. Here, using Escherichia coli as a model bacterium, we examined genetic backgrounds and plasmid profiles of generic fecal and wastewater isolates and those possessing bla_CTX-M and bla_CMY-2 genes (which confer resistance to third-generation cephalosporins) to delineate factors shaping the environmental persistence of plasmid-associated ARGs in beef cattle feedlots. The wastewater environment exerted minimal influence on plasmid repertoires, as the number of plasmids and distribution of different incompatibility groups did not differ between generic fecal and wastewater isolates. The bla_CTX-M and bla_CMY-2 genes were associated with IncF and IncA/C plasmids, respectively, and host isolates possessing these ARGs had fewer plasmids than generic isolates, suggesting ARG-bearing plasmids may associate predominantly with such hosts to compensate for the metabolic burden imposed by these plasmids. Phylogeny also appeared to be a factor for bla_CTX-M genes, as their bacterial hosts were restricted to particular genetic lineages, including the environmentally adapted ET-1 clade, as noted previously for these genes. Ultimately, these findings have important implications for evaluating human health risks of agricultural wastewater with respect to environmental persistence of ARGs and may help identify options for improving wastewater treatment.

Phylogenic classification and virulence genes profiles of uropathogenic E. coli and diarrhegenic E. coli strains isolated from community acquired infections

The emergence of E.coli strains displaying patterns of virulence genes from different pathotypes shows that the current classification of E.coli pathotypes may be not enough, the study aimed to compare the phylogenetic groups and urovirulence genes of uropathogenic Escherichia coli (UPEC) and diarrheagenic E.coli (DEC) strains to extend the knowledge of E.coli classification into different pathotypes. A total of 173 UPEC and DEC strains were examined for phylogenetic typing and urovirulence genes by PCR amplifications. In contrast to most reports, phylogenetic group A was the most prevalent in both UPEC and DEC strains, followed by B2 group. Amplification assays revealed that 89.32% and 94.29% of UPEC and DEC strains, respectively, carried at least one of the urovirulence genes, 49.5% and 31.4% of UPEC and DEC strains, respectively, carried ≥ 2 of the urovirulence genes, fim H gene was the most prevalent (66.9% and 91.4%) in UPEC and DEC strains respectively. Twenty different patterns of virulence genes were identified in UPEC while 5 different patterns in DEC strains. Strains with combined virulence patterns of four or five genes were belonged to phylogenetic group B2. Our finding showed a closer relationship between the DEC and UPEC, so raised the suggestion that some DEC strains might be potential uropathogens. These findings also provide different insights into the phylogenetic classification of E. coli as pathogenic or commensals where group A can be an important pathogenic type as well as into the classification as intestinal or extra- intestinal virulence factors.

The Arginine Deiminase Operon Is Responsible for a Fitness Trade-Off in Extended-Spectrum-β-Lactamase-Producing Strains of Escherichia coli

We previously identified an operon involved in an arginine deiminase (ADI) pathway (arc operon) on a CTX-M-producing plasmid from an O102-ST405 strain of Escherichia coli As the ADI pathway was shown to be involved in the virulence of various Gram-positive bacteria, we tested whether the ADI pathway could be involved in the epidemiological success of extended-spectrum-β-lactamase (ESBL)-producing E. coli strains. We studied two collections of human E. coli isolated in France (n = 493) and England (n = 1,509) and show that the prevalence of the arc operon (i) is higher in ESBL-producing strains (12.1%) than in nonproducers (2.5%), (ii) is higher in CTX-M-producing strains (16%) than in other ESBL producers (3.5%), and (iii) increased over time in ESBL-producing strains from 0% before 2000 to 43.3% in 2011 to 2012. The arc operon, found in strains from various phylogenetic backgrounds, is carried by IncF plasmids (85%) or chromosomes (15%) in regions framed by numerous insertion sequences, indicating multiple arrivals. Competition experiments showed that the arc operon enhances fitness of the strain in vitro in lysogeny broth with arginine. In vivo competition experiments showed that the arc operon is advantageous for the strain in a mouse model of urinary tract infection (UTI), whereas it is a burden in a mouse model of intestinal colonization. In summary, we have identified a trait linked to CTX-M-producing strains that is responsible for a trade-off between two main E. coli lifestyles, UTI and gut commensalism. This trait alone cannot explain the wide spread of ESBLs in E. coli but merits epidemiological surveillance.

Antimicrobial Resistance and Molecular Characterization of Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Ducks in South Korea

Ducks are potential carriers of pathogenic bacteria, which are capable of transmitting zoonotic diseases to humans. The global spread of Enterobacteriaceae carrying extended-spectrum β-lactamase (ESBL) genes is a public health concern. This study investigated the prevalence of antimicrobial resistance in Escherichia coli isolated from ducks in Korea and described the molecular characteristics of the ESBLs they produced. A total of 146 E. coli isolates from 404 duck fecal and carcass samples in 85 duck farms were tested for antimicrobial resistance using the broth dilution method and were further characterized using molecular methods. We observed high resistance rates to tetracycline, trimethoprim/sulfamethoxazole, nalidixic acid, ampicillin, and ciprofloxacin. In total, six ceftiofur-resistant isolates (4.1%) were observed, which produced CTX-M-55 (n = 3) or CTX-M-65 β-lactamase (n = 3). All CTX-M-producing E. coli isolates were also resistant to ciprofloxacin, with mutations in the quinolone resistance determining region of GyrA (S83L with or without D87N) and ParC (S80I), and three CTX-M-producing E. coli isolates carried plasmid-mediated quinolone resistance (PMQR) genes, qepA (n = 1), qnrS, and acc(6')-Ib-cr (n = 2). The transfer of bla_CTX-M genes was observed in one isolate mediated by IncF-family plasmids but not in the co-resistant isolates carrying both bla_CTX-M and PMQR genes. Pulsed-field gel electrophoresis and multilocus sequence typing demonstrated that CTX-M-producing isolates were heterogeneous; however, identical isolates were found in different farms and slaughterhouses. This study presents baseline data on antimicrobial resistance of E. coli derived from duck samples and is the first report of CTX-M-55 and CTX-M-65 β-lactamase-producing E. coli isolated from ducks in Korea. The dissemination of ESBL-producing E. coli poses a potential risk to public health and therefore should be monitored.

A nonlinear time-series analysis approach to identify thresholds in associations between population antibiotic use and rates of resistance

Balancing access to antibiotics with the control of antibiotic resistance is a global public health priority. At present, antibiotic stewardship is informed by a 'use it and lose it' principle, in which antibiotic use by the population is linearly related to resistance rates. However, theoretical and mathematical models suggest that use-resistance relationships are nonlinear. One explanation for this is that resistance genes are commonly associated with 'fitness costs' that impair the replication or transmissibility of the pathogen. Therefore, resistant genes and pathogens may only gain a survival advantage where antibiotic selection pressures exceed critical thresholds. These thresholds may provide quantitative targets for stewardship-optimizing the control of resistance while avoiding over-restriction of antibiotics. Here, we evaluated the generalizability of a nonlinear time-series analysis approach for identifying thresholds using historical prescribing and microbiological data from five populations in Europe. We identified minimum thresholds in temporal relationships between the use of selected antibiotics and incidence rates of carbapenem-resistant Acinetobacter baumannii (Hungary), extended-spectrum β-lactamase-producing Escherichia coli (Spain), cefepime-resistant E. coli (Spain), gentamicin-resistant Pseudomonas aeruginosa (France) and methicillin-resistant Staphylococcus aureus (Northern Ireland) in different epidemiological phases. Using routinely generated data, our approach can identify context-specific quantitative targets for rationalizing population antibiotic use and controlling resistance. Prospective intervention studies that restrict antibiotic consumption are needed to validate these thresholds.

Impact of l-Arginine and l-Histidine on the structural, optical and antibacterial properties of Mg doped ZnO nanoparticles tested against extended-spectrum beta-lactamases (ESBLs) producing Escherichia coli

Magnesium doped Zinc oxide nanoparticles (Mg:ZnO NPs) were synthesized by co-precipitation method. The synthesized Mg:ZnO NPs exhibited hexagonal wurtzite structure, which was confirmed by X-ray diffraction results. After structural confirmation of Mg doped ZnO NPs, base amino acids like l-Arginine and l-Histidine were separately incorporated with the Mg: ZnO NPs. l-Arginine added Mg:ZnO (Mg:ZnO:LA) and l-Histidine added Mg:ZnO (Mg:ZnO: LH) NPs retained the same wurtzite hexagonal structure and average crystallite sizes of Mg: ZnO:LA and Mg: ZnO:LH NPs were found to be 25 nm and 20 nm respectively. The sizes of Mg:ZnO:LH and Mg: ZnO: LA NPs decreased as compared to that of the Mg doped ZnO NPs. From the FT-IR spectra, the ZnO stretching frequencies were observed at 516, 517 and 518 cm^-1 for Mg:ZnO, Mg:ZnO: LA and Mg: ZnO:LH NPs respectively. From the FESEM images, the morphologies of ZnO:Mg and ZnO:Mg:LA NPs were spherical and the Mg: ZnO: LH NPs formed nano-flakes structure. From the EDAX study, the amount of elements incorporated in the samples was determined. The photoluminescence measurements revealed the existence of zinc vacancies, oxygen vacancies and surface defects of the samples. Antibacterial activity of the amino acid added Mg doped ZnO NPs was studied against extended-spectrum beta-lactamases (ESBLs) producing Escherichia coli (E. coli).The Minimal Inhibitory Concentration (MIC) of the LH added ZnO:Mg NPs was found to be 1000 μg/ml for which the growth of E. coli completely inhibited. l-Histidine added Mg doped ZnO NPs showed the highest antibacterial activity as compared to that of the Mg:ZnO NPs and ZnO:Mg:LA NPs.

Phenotypic and Genotypic Characterization of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Asymptomatic Bacteriuria in Pregnancy

Asymptomatic bacteriuria (ASB) has been consistently observed in pregnancy. However, there is a paucity of data on the prevalence and characteristics of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in ASB in pregnant women. Therefore, we sought to investigate ESBL-producing and multidrug-resistant Enterobacteriaceae in antenatal women with ASB. Urine samples were collected from 310 asymptomatic pregnant women attending primary antenatal clinics and screened for significant bacteriuria. Isolates of Enterobacteriaceae were phenotypically tested for their ESBL production. ESBL genes (CTX-M, TEM, and SHV genes) were then amplified by polymerase chain reaction (PCR). Multiplex PCRs were used to perform phylogenetic typing of ESBL-producing Escherichia coli isolates and to examine the commonality of sequence type 131 (ST131)-O25b and ST131-O16. A total of 103 (33.2%) pregnant women were positive for significant bacteriuria (80 Enterobacteriaceae). Of these isolates, 32.5% (n = 26) were ESBL producers and had a higher rate of multidrug resistance than non-ESBL producers. Genotypic characterization of ESBL-producing isolates showed that 84.6% had the bla_CTX-M gene (bla_CTX-M-15 = 77.3%; bla_CTX-M-9 = 18.2%). None of the isolates were of the TEM or SHV type. Half of the ESBL-producing E. coli isolates were of the phylogroup B2, and 4 (20%) isolates were of the ST131-O16 clonal subgroup. This study is the first in Egypt to provide evidence for the high prevalence of ESBL-producing Enterobacteriaceae in pregnant women with ASB. It also represents an important step toward genotypic characterization of this resistant form of bacteria, which may be useful for future antimicrobial studies.

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.

Escherichia coli colonizing healthy children in Tunisia: High prevalence of extra-intestinal pathovar and occurrence of non-extended-spectrum-β-lactamase-producing ST131 clone

This study was performed to investigate the distribution of antimicrobial resistance genes and extra-intestinal virulence determinants in a collection of 98 Escherichia coli strains isolated from rectal swabs of healthy children. Forty-six isolated strains were resistant to at least one of the tested antibiotics (usually active against enterobacteria). They were mainly resistant to ampicillin and ticarcillin (42.97%), tetracyclin (26.5%), and trimethoprim/sulfamethoxazole (18.4%). No resistance to the third generation of cephalosporins, carbapenems, aminoglycosides and colistin was found. Resistance to penicillins was encoded by bla_TEM-1 (n=34) and bla_SHV-1 genes (n=4). Tetracyclin resistance was encoded by tetB (n=12), tetA (n= 5), and tetC (n=1) genes. Amongst resistant quinolones isolated (n=5), chromosomal mutations in gyrA and parC genes were detected in four isolates and qnrS1 gene in two strains. Nine plasmid replicon types were detected; IncFIB (n=36) and IncI1 (n=7) were the most frequent ones. Isolates frequently belonged to phylogenetic groups A (51.1%) and D (27.5%). Extra-intestinal pathovar (n=38) occurred mainly in B2 phylogroup (P=0.0002). Amongst them, two isolates (non-extended-spectrum-β-lactamase (ESBL)-producers) belonged to the pandemic clone ST131. A significant distribution of virulence determinants and pathogenicity island marker was observed within strains belonging to B2 and D phylogroups. Interestingly, our results showed that ExPEC strains, including ST131 pandemic clone, are present within fecal isolates in healthy children. These findings highlight the importance of intestinal microbiota as a reservoir for virulent and resistant strains. Thus, reinforcing hand hygiene and antibiotic rational use is imperative to avoid the diffusion of these pathogens in the community.

Diversity of CTX-M Extended-Spectrum β-Lactamases in Escherichia coli Isolates from Retail Raw Ground Beef: First Report of CTX-M-24 and CTX-M-32 in Algeria

The aim of this study was to investigate the prevalence and molecular features of extended-spectrum cephalosporin resistance in Escherichia coli isolates contaminating ground beef at retail in Algeria. Of 371 ground beef samples, 27.5% were found to contain cefotaxime-resistant E. coli isolates distributed into A (24.5%), B1 (60.8%), and D (14.7%) phylogroups. A rate of 88.2% of isolates had a multidrug-resistance phenotype. All strains were producers of CTX-M type extended-spectrum β-lactamases (ESBLs): CTX-M-1, CTX-M-3, CTX-M-14, CTX-M-15, CTX-M-24, or CTX-M-32. Conjugation assays allowed the transfer of bla_CTX-M-1 in association with IncI1 plasmids, bla_CTX-M-15 with IncI1 and IncK+B/O plasmids, bla_CTX-M-3 with IncK plasmids, and bla_CTX-M-14 with IncF1B or IncK plasmids. Sequence analysis of gyrA and parC genes showed mutations in 98.6% of ciprofloxacin-resistant isolates. The patterns "GyrA: S83L+D87N, ParC: S80I" (46.5%) and "ParC: S80I" (42.3%) were predominant. qnrS1, qnrB, and aac(6')-Ib-cr were detected in 18.7% of isolates. The tet genes, tetA, tetB, and tetA+tetB, were present in 95.7% of tetracycline-resistant isolates. The sul genes (sul1, sul2, sul3, sul1+sul2, sul2+sul3, and sul1+sul3) and the dfr gene clusters (dfrA1, dfrA5, dfrA7, dfrA8, dfrA12, dfrA5+dfrA12, dfrA1+dfrA5, dfrA7+dfrA12, dfrA5+dfrA7, and dfrA1+dfrA5+dfrA7) were found in 96.4% and 85.5% of sulfamethoxazole/trimethoprim-resistant isolates, respectively. Classes 1 and 2 integrons were detected in 67.6% and 9.8% of isolates, respectively. This study highlighted the significant presence of resistance genes, in particular those of CTXM ESBLs, in the beef meat, with the risk of their transmission to humans through food chain.

Molecular detection of β-lactamase and integron genes in clinical strains of Klebsiella pneumoniae by multiplex polymerase chain reaction

INTRODUCTION:

Infections caused by β-lactamase-producing gram-negative bacteria, such as Klebsiella pneumoniae, are increasing globally with high morbidity and mortality. The aim of the current study was to determine antimicrobial susceptibility patterns and the prevalence of antibiotic resistance genes (β-lactamase and integron genes) using multiplex PCR.

METHODS

One-hundred K. pneumoniae isolates were collected from different clinical samples. Antibiotic susceptibility testing was performed with thirteen different antibiotics. Multiplex-PCR was used to detect β-lactamase (bla TEM, bla CTX-M, bla SHV , bla VEB, bla PER, bla GES, bla VIM, bla IMP, bla OXA, and bla KPC) and integron genes (int I, int II, and int III).

RESULTS:

The highest and lowest rate of resistance was exhibited against amikacin (93%) and imipenem (8%), respectively. The frequency of β-lactamase-positive K. pneumoniae was 37%, and the prevalence of the bla TEM, bla CTX-M, bla SHV , bla VEB, bla PER, bla GES, bla VIM, bla IMP, bla OXA, and bla KPC genes was 38%, 24%, 19%, 12%, 6%, 11%, 33%, 0%, 28%, and 23%, respectively. Of the 100 isolates, eight (8%) were positive for class I integrons; however, class II and III integrons were not detected in any of the strains.

CONCLUSIONS:

These results indicate co-carriage of a number of β-lactamase genes and antibiotic resistance integrons on the same plasmids harboring multi-drug resistance genes. It seems that these properties help to decrease treatment complications due to resistant bacterial infections by rapid detection, infection-control programs and prevention of transmission of drug resistance.

In vitro antibacterial activity of ZnO and Nd doped ZnO nanoparticles against ESBL producing Escherichia coli and Klebsiella pneumoniae

Pure ZnO and Neodymium (Nd) doped ZnO nanoparticles (NPs) were synthesized by the co-precipitation method. The synthesized nanoparticles retained the wurtzite hexagonal structure. From FESEM studies, ZnO and Nd doped ZnO NPs showed nanorod and nanoflower like morphology respectively. The FT-IR spectra confirmed the Zn-O stretching bands at 422 and 451 cm(-1) for ZnO and Nd doped ZnO NPs respectively. From the UV-VIS spectroscopic measurement, the excitonic peaks were found around 373 nm and 380 nm for the respective samples. The photoluminescence measurements revealed that the broad emission was composed of ten different bands due to zinc vacancies, oxygen vacancies and surface defects. The antibacterial studies performed against extended spectrum β-lactamases (ESBLs) producing strains of Escherichia coli and Klebsiella pneumoniae showed that the Nd doped ZnO NPs possessed a greater antibacterial effect than the pure ZnO NPs. From confocal laser scanning microscopic (CLSM) analysis, the apoptotic nature of the cells was confirmed by the cell shrinkage, disorganization of cell wall and cell membrane and dead cell of the bacteria. SEM analysis revealed the existence of bacterial loss of viability due to an impairment of cell membrane integrity, which was highly consistent with the damage of cell walls.

Multidrug Resistant CTX-M-Producing Escherichia coli: A Growing Threat among HIV Patients in India

Extended Spectrum β-Lactamases (ESBLs) confer resistance to third-generation cephalosporins and CTX-M types have emerged as the most prominent ESBLs worldwide. This study was designed to determine the prevalence of CTX-M positive ESBL-producing urinary E. coli isolates from HIV patients and to establish the association of multidrug resistance, phylogeny, and virulence profile with CTX-M production. A total of 57 ESBL producers identified among 76 E. coli strains isolated from HIV patients from South India were screened for bla_CTX-M, AmpC production, multidrug resistance, and nine virulence associated genes (VAGs), fimH, pap, afa/dra, sfa/foc, iutA, fyuA, iroN, usp, and kpsMII. The majority (70.2%) of the ESBL producers harbored bla_CTX-M and were AmpC coproducers. Among the CTX-M producers, 47.5% were found to be UPEC, 10% harbored as many as 7 VAGs, and 45% possessed kpsMII. Multidrug resistance (CIP^RSXT^RGEN^R) was significantly more common among the CTX-M producers compared to the nonproducers (70% versus 41.2%). However, 71.4% of the multidrug resistant CTX-M producers exhibited susceptibility to nitrofurantoin thereby making it an effective alternative to cephalosporins/fluoroquinolones. The emergence of CTX-M-producing highly virulent, multidrug resistant uropathogenic E. coli is of significant public health concern in countries like India with a high burden of HIV/AIDS.

IncF Plasmids Are Commonly Carried by Antibiotic Resistant Escherichia coli Isolated from Drinking Water Sources in Northern Tanzania

The aim of this study was to identify the replicon types of plasmids, conjugation efficiencies, and the complement of antibiotic resistance genes for a panel of multidrug resistant E. coli isolates from surface waters in northern Tanzania. Standard membrane filtration was used to isolate and uidA PCR was used to confirm the identity of strains as E. coli. Antibiotic susceptibility was determined by breakpoint assay and plasmid conjugation was determined by filter-mating experiments. PCR and sequencing were used to identify resistance genes and PCR-based replicon typing was used to determine plasmid types. Filter mating experiments indicated conjugation efficiencies ranged from 10(-1) to 10(-7). Over 80% of the donor cells successfully passed their resistance traits and eleven different replicon types were detected (IncI1, FIC, P, FIIA, A/C, FIB, FIA, H12, K/B B/O, and N). IncF plasmids were most commonly detected (49% of isolates), followed by types IncI1 and IncA/C. Detection of these public health-relevant conjugative plasmids and antibiotic resistant traits in Tanzanian water suggests the possible pollution of these water sources from human, livestock, and wild animal wastes and also shows the potential of these water sources in the maintenance and transmission of these resistance traits between environments, animals, and people.

Community fecal carriage of broad-spectrum cephalosporin-resistant Escherichia coli in Tunisian children

The spread of extended spectrum β-lactamases (ESBL) and plasmid mediated AmpC β-lactamases (pAmpC) was evaluated in Escherichia coli strains collected from the intestinal microbiota of healthy children in Tunisia. The carriage rate of CTX^RE. coli was 6.6% (7 of 105 samples) and one strain/sample was further characterized (7 isolates). These isolates harbored bla_CTX-M-1 (n = 4), bla_CTX-M-15 (n = 2), and bla_CMY-2 gene (n = 1), which were usually located on FIB replicon type and carried class 1 integrons. The acc(6')-Ib-cr variant was identified in one isolate that harbored bla_CTX-M-15. CTX^RE. coli isolates were genetically unrelated and belonged to B1 (n = 3/ST155/ST398/ST58), D (n = 2/ST117/ST493), B2 (n = 1/ST127), and A (n = 1/ST746) phylogroups. Strain virulence scores varied from 3 to 12, and frequently harbored the pathogenicity island PAI IV₅₃₆. The intestinal tract of healthy children constitute an important reservoir of ESBL producing E. coli. Thus, improvement of hygiene measures mainly in the school environment and rational use of antibiotics would be of great help in preventing selection and diffusion of resistant strains from intestinal microbiota.

Resistance and virulence potential of uropathogenic Escherichia coli strains isolated from patients hospitalized in urology departments: a French prospective multicentre study

We characterized antibiotic resistance and virulence of uropathogenic Escherichia coli (UPEC) strains isolated from urinary tract infections (UTIs) in patients hospitalized in urology departments. A prospective multicentre study was initiated from March 2009 and lasted until February 2010 in French urology units. All patients with asymptomatic bacteriuria (ABU), acute cystitis, acute pyelonephritis or acute prostatitis in whom UPEC was detected were included. Antimicrobial resistance and virulence factors were compared among the different groups. To identify independent associations between virulence markers and the risk of UTI, we used a multivariate logistic regression. We included 210 patients (mean age: 65.8 years; 106 female). Episode of UTI was community acquired in 72.4 %. ABU was diagnosed in 67 cases (31.9 %), cystitis in 52 cases (24.7 %), pyelonephritis in 35 cases (16.7 %) and prostatitis in 56 cases (26.7 %). ABU was more frequent in patients with a urinary catheter (76.1 vs 23.9 %, P<0.001). The resistance rate was 7.6 and 24.8 % for cefotaxime and ciprofloxacin, respectively. UPEC isolated from infections belonged more frequently to phylotypes B2 and D (P =0.07). The papG allele II and papA, papC, papE, kpsMTII and iutA genes were significantly more frequent in infecting strains (P<0.05). In multivariate analysis, strains susceptible to ciprofloxacin were significantly associated with papG allele II (P=0.007), kpsMTK1 (P<0.001) and hlyA (P<0.001) compared with the ciprofloxacin-resistant strains. To the best of our knowledge, this is the first study evaluating the antibiotic resistance and virulence features of UPEC isolated from patients hospitalized in urology departments. High resistance rates were observed, notably for ciprofloxacin, highlighting the importance of a reinforced surveillance in this setting.

Antibiotic Resistance, RAPD- PCR Typing of Multiple Drug Resistant Strains of Escherichia Coli From Urinary Tract Infection (UTI)

INTRODUCTION

Global spreading of multidrug resistant strains of Escherichia coli is responsible for Urinary Tract Infection (UTI) which is a major health problem in of concern. Among the gram negative bacteria, the major contributors for UTI belongs to the family Enterobacteriaceae, which includes E. coli, Klebsiella, Citrobacter and Proteus. However, E. coli accounts for the major cause of Urinary tract infections (UTIs) and accounts for 75% to 90% of UTI isolates.

AIM

The main aim of this study is to analyse the phylogenetic grouping of clinical isolates of UTI E. coli.

MATERIALS AND METHODS

In this study nearly 58 E. coli strains were isolated and confirmed through microbiological, biochemical characterization. The urine samples were collected from outpatients having symptoms of UTI, irrespective of age and sex in Tamil Nadu, India. The isolates were subjected to analyse for ESBL and AmpC β-lactamase production. To understand its genetic correlation, molecular typing was carried out using RAPD-PCR method.

RESULTS

Here we noted phenotypically twenty seven isolates were positive for ESBL and seven for AmpC β-lactamase production. However, among the ESBL isolates higher sensitivity was noted for Nitrofurantoin and Cefoxitin. It is worth to note that the prevalence of UTIs was more common among female and elderly male. Phylogenetic grouping revealed the presence of 24 isolates belonged to B2 group followed by 19 isolates to group A, eight isolates to group B1 and Seven isolates to group D.

CONCLUSION

Phenotypically most of the strains were positive for ESBL and showed high sensitivity for Nitrofurantoin and cefoxitin.

Emergence of Antimicrobial-Resistant Escherichia coli of Animal Origin Spreading in Humans

In the context of the great concern about the impact of human activities on the environment, we studied 403 commensal Escherichia coli/Escherichia clade strains isolated from several animal and human populations that have variable contacts to one another. Multilocus sequence typing (MLST) showed a decrease of diversity 1) in strains isolated from animals that had an increasing contact with humans and 2) in all strains that had increased antimicrobial resistance. A specific B1 phylogroup clonal complex (CC87, Institut Pasteur schema nomenclature) of animal origin was identified and characterized as being responsible for the increased antimicrobial resistance prevalence observed in strains from the environments with a high human-mediated antimicrobial pressure. CC87 strains have a high capacity of acquiring and disseminating resistance genes with specific metabolic and genetic determinants as demonstrated by high-throughput sequencing and phenotyping. They are good mouse gut colonizers but are not virulent. Our data confirm the predominant role of human activities in the emergence of antimicrobial resistance in the environmental bacterial strains and unveil a particular E. coli clonal complex of animal origin capable of spreading antimicrobial resistance to other members of microbial communities.

Incidence, Antimicrobial Resistance, and Molecular Characteristics of Nontyphoidal Salmonella Including Extended-Spectrum β-Lactamase Producers in Retail Chicken Meat

The present study was undertaken to determine the prevalence of Salmonella in 100 chicken carcass samples from five integrated broiler operation brands in Korea. Serotypes, antibiotic resistance patterns, extended-spectrum β-lactamase (ESBL) genotype, and clonal divergence using multilocus sequence typing of the isolated strains were analyzed. A total of 42 chicken samples were contaminated with nontyphoidal Salmonella (NTS) isolates: 16 isolates (38%) were Salmonella Virchow, 9 (21%) were Salmonella Bareilly, and 8 (19%) were Salmonella Infantis. A multidrug resistance (MDR; resistant to more than three classes of antibiotics) phenotype was observed in 29% of the isolates, which were resistant to five or more classes of antibiotics. The dominant MDR type was resistance to classes of penicillin, cephalosporins, aminoglycosides, quinolones, and tetracyclines. All the MDR isolates were positive for ESBL producers, and all but one (with the CTX-M-1 genotype) had the CTX-M-15 genotype. Multilocus sequence typing of the isolates revealed ST16 as the dominant sequence type; Salmonella Virchow, Salmonella Infantis, and Salmonella Richmond were all ST16, indicating a close genetic relationship between these serovars. This is the first study in Korea showing the CTX-M-1 type of NTS and the prevalence of ESBL-producing strains among NTS isolated from retail chicken meat. Our findings suggest that MDR Salmonella contamination is widely prevalent in retail chicken meat, and consumption of inadequately cooked products could lead to dissemination of NTS, which is hazardous to human health.

Characterization of Escherichia coli-Producing Extended-Spectrum β-Lactamase (ESBL) Isolated from Chicken Slaughterhouses in South Korea

In South Korea, few reports have indicated the occurrence and characteristics of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in food-producing animals, particularly in poultry slaughterhouses. In this study, we investigated the occurrence and antibiotic resistance of ESBL-producing E. coli from whole chicken carcasses (n=156) and fecal samples (n=39) of chickens obtained from 2 slaughterhouses. Each sample enriched in buffered peptone water was cultured on MacConkey agar with 2 mg/L cefotaxime and ESBL agar. ESBL production and antibiotic susceptibility were determined using the Trek Diagnostics system. The ESBL genotypes were determined by polymerase chain reaction (PCR) using the bla(SHV), bla(TEM), and bla(CTX-M) gene sequences. Subtyping using a repetitive sequence-based PCR system (DiversiLab™) and multilocus sequence typing (MLST) were used to assess the interspecific biodiversity of isolates. Sixty-two ESBL-producing E. coli isolates were obtained from 156 samples (39.7%). No bla(SHV) genes were detected in any of the isolates, whereas all contained the bla(TEM) gene. Twenty-five strains (40.3%) harbored the CTX-M group 1 gene. The most prevalent MLST sequence type (ST) was ST 93 (14.5%), followed by ST 117 (9.7%) and ST 2303 (8.1%). This study reveals a high occurrence and β-lactams resistance rate of E. coli in fecal samples and whole chickens collected from slaughterhouses in South Korea.

Extended-Spectrum β-Lactamase- and Carbapenemase-Producing Enterobacteriaceae Isolated from Egyptian Patients with Suspected Blood Stream Infection

Objectives

The aim of the study was to investigate the prevalence of extended-spectrum β-lactamase and carbapenemase production among Enterobacteriaceae isolated from Egyptian patients with suspected blood stream infection.

Methods

Ninety-four Enterobacteriaceae blood culture isolates from Egyptian patients with suspected blood stream infection were collected, one isolate per patient. Identification of bacterial isolates was performed with MALDI-TOF (MS-based Vitek MS system, bioMerieux). Screening for ESBLs and carbapenemases production was done with the Vitek 2 system (bioMérieux). ESBL production was confirmed using the combined disk diffusion method for cefotaxime, ceftazidime, and cefepime, all with and without clavulanic acid (Rosco). Real-time PCR and sequencing were used to characterize the resistance genes. The phylogenetic groups of E. coli were identified by a PCR-based method.

Results

Of the 94 Enterobacteriaceae isolates 46 (48.93%) showed an ESBL phenotype. One Enterobacter spp isolate was ESBL-producer and meropenem-resistant. The genetic analysis showed that CTX-M was present in 89.13% (41/46) of the ESBL-producing Enterobacteriaceae, whereas TEM and SHV were detected in 56.52% (26/46) and 21.74% (10/46) respectively (47.83%) of the ESBL-producing isolates were multidrug resistant (MDR). Eleven out of 30 ESBL-producing E-coli isolates were assigned to phylogroup B2, followed by groups B1 (8 isolates), A (6 isolates) and D (5 isolates).

Conclusions

The high ESBL-E rates (48.93%) found in this study together with the identification of one carbapenem-resistant Enterobacter spp isolate is worrisome. Our results indicate that systems for monitoring and detection of ESBL-producing bacteria in Egyptian hospitals have to be established. Also strict hospital infection control policies with the restriction of the consumption of extended-spectrum cephalosporins are necessary.

Prevalence and characterization of extended-spectrum-β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in ready-to-eat vegetables

The objective of this investigation was to determine the prevalence and characteristics of extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in ready-to-eat (RTE) vegetables. A total of 189 RTE vegetable samples (91 sprouts and 98 mixed salads) were collected in a retail market in South Korea from October 2012 to February 2013. The prevalence of ESBL-producing E. coli and K. pneumoniae was 10.1%. Of these, 94.7% were from the sprout samples. All isolates were resistant to cefotaxime, and many of the ESBL producers were also resistant to non-β-lactam antibiotics, including gentamicin, trimethoprim/sulfamethoxazole, and ciprofloxacin (73.7%, 63.2%, and 26.3% respectively). TEM-1, SHV-1, -2, -11, -12, -27, -28 and -61, and CTX-M-14, -15 and -55 β-lactamases were detected alone or in combination. The genetic platforms of all CTX-M producing isolates were ISEcp1-blaCTX-M-orf477 and ISEcp1-blaCTX-M-IS903 in CTX-M groups 1 and 9, respectively. To our knowledge, this is the first report of the prevalence and characterization of ESBL-producing E. coli and K. pneumoniae isolated from RTE vegetables. The results of this study indicate that RTE vegetables, sprouts, in particular, may play a role in spreading antimicrobial resistant bacteria and ESBL genes to humans.

Characterization of Multidrug Resistant Extended-Spectrum Beta-Lactamase-Producing Escherichia coli among Uropathogens of Pediatrics in North of Iran

Escherichia coli remains as one of the most important bacteria causing infections in pediatrics and producing extended-spectrum beta-lactamases (ESBLs) making them resistant to beta-lactam antibiotics. In this study we aimed to genotype ESBL-producing E. coli isolates from pediatric patients for ESBL genes and determine their association with antimicrobial resistance. One hundred of the E. coli isolates were initially considered ESBL producing based on their MIC results. These isolates were then tested by polymerase chain reaction (PCR) for the presence or absence of CTX, TEM, SHV, GES, and VEB beta-lactamase genes. About 30.5% of isolated E. coli was ESBL-producing strain. The TEM gene was the most prevalent (49%) followed by SHV (44%), CTX (28%), VEB (8%), and GES (0%) genes. The ESBL-producing E. coli isolates were susceptible to carbapenems (66%) and amikacin (58%) and showed high resistance to cefixime (99%), colistin (82%), and ciprofloxacin (76%). In conclusion, carbapenems were the most effective antibiotics against ESBl-producing E. coli in urinary tract infection in North of Iran. The most prevalent gene is the TEM-type, but the other resistant genes and their antimicrobial resistance are on the rise.

Partition locus-based classification of selected plasmids in Klebsiella pneumoniae, Escherichia coli and Salmonella enterica spp.: an additional tool

The dissemination of antimicrobial resistance genes in Enterobacteriaceae has been largely attributed to plasmids, circular DNA molecules capable of autonomous replication. Whereas high-copy-number plasmids primarily rely on passive diffusion for plasmid maintenance, low-copy-number plasmids utilize so-called partition (par) systems. Plasmid partition relies on three structures, i.e. a centromere like DNA site, a centromere-binding protein and an ATPase or a GTPase motor protein for plasmid positioning. Identification and classification of plasmids is essential for tracing plasmids conferring drug resistance. PCR-based replicon typing is currently the standard method for plasmid identification but there are new classification schemes, especially the relaxase gene typing (PRaseT). Here we developed a multiplex PCR set targeting par loci found on the plasmids most frequently encountered in Enterobacteriaceae. This method, called "plasmid partition gene typing" (PAR-T), was validated with 136 transconjugants or transformants harboring various replicon types. The method was tested with 30 multidrug-resistant clinical isolates including Escherichia coli, Klebsiella pneumoniae and Salmonella enterica subsp. enterica carrying 1-4 replicons; all replicons were tested in parallel with PRaseT for comparison. Six multiplex PCRs and one simplex PCR including 18 pairs of primers recognized plasmids of groups IncA/C, FIA, FIB, FIC, FIIk, FII, HI1, HI2, I1, L/M, N, X. Our set of multiplex PCRs showed high specificity for the classification of resistance plasmids except for IncX replicons.

Prevalence and characterization of plasmid-mediated quinolone resistance genes in extended-spectrum β-lactamase-producing Enterobacteriaceae in a Tunisian hospital

The objective of the study was to assess the prevalence of plasmid-mediated quinolone resistance (PMQR) genes (qnrA, qnrB, qnrC, qnrD, qnrS, aac(6')-Ib-cr, qepA, and oqxAB) in a collection of 120 extended-spectrum β-lactamases (ESBLs)-producing enterobacteria and to characterize them. Overall, PMQR determinants were detected in 72 (60%) isolates (20 Escherichia coli, 32 Klebsiella pneumoniae, and 20 Enterobacter cloacae). PMQR frequencies were as follows: qnr genes (25.8%), oqxAB (21.6%), and aac(6')-Ib-cr variant (19.2%). Four qnr alleles were identified as qnrB1 (83.8%), qnrB4 (6.4%), qnrB2 (3.2%), and qnrS1 (6.4%). qnr genes were mainly detected in E. cloacae (50%), aac(6')-Ib-cr in E. coli (47.5%), and oqxAB in K. pneumoniae (65%). Overall, blaCTX-M-15 (90.3%) was the most prevalent blaESBL type followed by blaSHV-12 (6.4%) and blaSHV-27 (2.7%). Rates of mutations in gyrA and parC genes were 75% for E. coli, 72.8% for K. pneumoniae, and 50% for E. cloacae. Isolates with mutations in their quinolone resistance-determining regions exhibited high fluoroquinolones resistance levels compared to those with wild ones. Genetic study of PMQR-harboring isolates revealed a great genomic diversity among each Enterobacteriaceae species. Our findings indicate the high prevalence of PMQR determinants among ESBL-producing Enterobacteriaceae isolates from our hospital and their diffusion in various unrelated CTX-M-15-producing clones.

Phylogenetic grouping and pathotypic comparison of urine and fecal Escherichia coli isolates from children with urinary tract infection

The aim of this study was to investigate the phylogenetic background and to assess hlyD (involved in the secretion of haemolysin A) and intI1 (encoding a class 1 integrase) in Escherichia coli isolates derived from urinary and fecal specimens. A total of 200 E. coli isolates was collected from patients presenting with urinary tract infection (UTI) during September 2009 to September 2010 and screened for hlyD and intI1 genes by polymerase chain reaction (PCR). Phylogenetic analysis showed that E. coli is composed of four main phylogenetic groups (A, B1, B2 and D) and that uropathogenic E. coli (UPEC) isolates mainly belong to groups B2 (54%) and D (34%) whereas group A (44%) and D (26%) are predominant among commensal E. coli isolates. In this study, hlyD was present in 26% of UPEC and 2% of commensal E. coli isolates. However, hemolytic activity was detected for 42% of UPEC and 6% of commensal E. coli isolates (p < 0.05). intI1 gene was more frequently expressed in UPEC (24%) in comparison with commensal E. coli isolates (12%). Resistance to aztreonam, co-trimoxazole and cefpodoxime were frequently found among UPEC isolates whereas commensal E. coli isolates were commonly resistant to co-trimoxazole, nalidixic acid and cefotaxime. Concluding, a considerable difference between UPEC and commensal E. coli isolates was observed regarding their phylogenetic groups, presence of class 1 integron and hlyD gene, hemolysin activity and resistance pattern. The detection of class 1 integrons and hlyD gene was higher among UPEC compared with commensal E. coli isolates. These findings may contribute for a better understanding of the factors involved in the pathogenesis of UPEC.

Differences in extended-spectrum beta-lactamase producing Escherichia coli virulence factor genes in the Baltic Sea region

The aim of this study was to compare the prevalence of different virulence factor (VF) genes in extended-spectrum beta-lactamase (ESBL) producing Escherichia coli strains isolated from the Baltic Sea region. A total of 432 strains of phenotypically ESBL positive E. coli were collected from 20 institutions located in Estonia, Latvia, Lithuania, and the region of St. Petersburg in Russia from January to May 2012 and analyzed for phylogenetic group and prevalence of 23 VF genes. The strains were collected from clinical material (urine, blood, wound, and respiratory tract). Bacterial isolates were compared according to phylogenetic group, clinical material, and geographical origin. Most of the VF genes were concentrated within phylogenetic group B2 and/or D. When comparing strains isolated from different countries, it was found that strains originating from Estonia and Latvia belonged mainly to group B2 and strains from Lithuania and Russia mainly to groups B2 and D. The P-fimbrial adhesin gene papEF was more prevalent in Russian strains, colicin gene cvaC in Lithuanian strains, and capsular gene kpsMTII in Latvian strains; serum resistant gene traT was less prevalent in Estonian strains. The regional differences of VF genes remained statistically significant after taking into account the phylogenetic distribution in the countries.