Epstein-Barr in a Patient Presenting with Right Upper Quadrant Pain: A Case Report from the Emergency Department.

BACKGROUND: Right upper quadrant abdominal pain and elevated cholestasis blood tests are usually associated with bacterial calculous cholecystitis. However, viral infections, such as Epstein-Barr virus (EBV) can also manifest with a similar clinical picture and is an important differential diagnosis. CASE REPORT: This case report discusses a young woman presenting to the emergency department with acute right upper quadrant abdominal pain. The initial assessment revealed a positive Murphy's sign, elevated white blood count, and a cholestatic pattern on liver function tests, leading one to suspect bacterial calculous cholecystitis and initiating antibiotic therapy. However, clinical examination also revealed tonsillar exudates and differential white blood cell count revealed monocytosis and lymphocytosis rather than a high neutrophil count. The patient tested positive for EBV. Furthermore, ultrasound and magnetic resonance imaging revealed gallbladder wall edema with no gallstones, leading one to conclude that the clinical manifestation and laboratory results were due to an EBV infection. Antibiotic therapy was ceased and the patient did not require surgical intervention. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Calculous bacterial cholecystitis usually entails antibiotic therapy and cholecystectomy. It is important to be aware of the differential diagnosis of EBV, as it usually does not require either of these and resolves spontaneously.

Evolution of antimicrobial resistance in E. coli biofilm treated with high doses of ciprofloxacin.

The evolution of antimicrobial resistance (AMR) has mainly been studied in planktonic bacteria exposed to sub-inhibitory antimicrobial (AM) concentrations. However, in a number of infections that are treated with AMs the bacteria are located in biofilms where they tolerate high doses of AM. In the present study, we continuously exposed biofilm residing E. coli at body temperature to high ciprofloxacin (CIP) concentrations increasing from 4 to 130 times the minimal inhibitory concentration (MIC), i.e., from 0.06 to 2.0 mg/L. After 1 week, the biofilms were full of CIP resistant bacteria. The evolutionary trajectory observed was the same as described in the literature for planktonic bacteria, i.e., starting with a single mutation in the target gene gyrA followed by mutations in parC, gyrB, and parE, as well as in genes for regulation of multidrug efflux pump systems and outer membrane porins. Strains with higher numbers of these mutations also displayed higher MIC values. Furthermore, the evolution of CIP resistance was more rapid, and resulted in strains with higher MIC values, when the bacteria were biofilm residing than when they were in a planktonic suspension. These results may indicate that extensive clinical AM treatment of biofilm-residing bacteria may not only fail to eradicate the infection but also pose an increased risk of AMR development.

Escherichia coli multilocus sequence type 38 from humans and broiler production represent distinct monophyletic groups.

Escherichia coli belonging to multilocus sequence type 38 (ST38) is a well-known cause of extra-intestinal infections in humans, and are frequently associated with resistance to extended-spectrum cephalosporins (ESCs). Resistance to carbapenems, mediated by blaOXA-genes has also been reported in this ST. Recently, the European Centre for Disease Prevention and Control (ECDC) released a rapid risk assessment on the increased detection of OXA-244 producing E. coli ST38 in humans, requesting further knowledge to determine the source. ST38 is also one of the most common STs among ESC-resistant E. coli from broiler production. Our aim was to investigate the genetic characteristics and relationship between E. coli ST38 from broiler production and humans, and to investigate if there has been a potential spillover between these sources. A total of 288 E. coli ST38 genomes isolated from humans in Europe (collected 2009-2019) and from Nordic broiler production (collected 2011-2014) were analyzed. The results showed distinct monophyletic clades associated to humans and broiler production. Furthermore, there were differences in the ESC resistance genes present in E. coli ST38 from the two sources. The blaOXA-244 gene was not present in E. coli from broiler production. Our results show that ST38 from humans and broiler production belong to well-separated clades, and suggest that the increased detection of OXA-244-producing E. coli ST38 in humans is not associated with spillover from broiler production.

Characterizing Antimicrobial Resistance in Clinically Relevant Bacteria Isolated at the Human/Animal/Environment Interface Using Whole-Genome Sequencing in Austria.

Antimicrobial resistance (AMR) is a public health issue attributed to the misuse of antibiotics in human and veterinary medicine. Since AMR surveillance requires a One Health approach, we sampled nine interconnected compartments at a hydrological open-air lab (HOAL) in Austria to obtain six bacterial species included in the WHO priority list of antibiotic-resistant bacteria (ARB). Whole genome sequencing-based typing included core genome multilocus sequence typing (cgMLST). Genetic and phenotypic characterization of AMR was performed for all isolates. Eighty-nine clinically-relevant bacteria were obtained from eight compartments including 49 E. coli, 27 E. faecalis, 7 K. pneumoniae and 6 E. faecium. Clusters of isolates from the same species obtained in different sample collection dates were detected. Of the isolates, 29.2% were resistant to at least one antimicrobial. E. coli and E. faecalis isolates from different compartments had acquired antimicrobial resistance genes (ARGs) associated with veterinary drugs such as aminoglycosides and tetracyclines, some of which were carried in conjugative and mobilizable plasmids. Three multidrug resistant (MDR) E. coli isolates were found in samples from field drainage and wastewater. Early detection of ARGs and ARB in natural and farm-related environments can identify hotspots of AMR and help prevent its emergence and dissemination along the food/feed chain.

Closed Genome Sequences of Providencia alcalifaciens Isolates from Dogs.

Eight Providencia alcalifaciens isolates from eight different dogs in Norway with acute hemorrhagic diarrhea were sequenced. Based on Illumina and Oxford Nanopore Technologies sequencing, all of the genomes were complete and closed after hybrid assembly.

Longitudinal Sampling Reveals Persistence of and Genetic Diversity in Extended-Spectrum Cephalosporin-Resistant Escherichia coli From Norwegian Broiler Production.

There are knowledge gaps concerning dynamics of extended-spectrum cephalosporin (ESC)-resistant Escherichia coli and their plasmids in broiler production and the persistence of strains on broiler farms. Thus, we aimed at characterising ESC-resistant Escherichia coli collected from all flocks reared on 10 different farms during a six-months sampling period. All isolates (n = 43) were subjected to whole-genome sequencing, and a subset of isolates (n = 7) were also sequenced using oxford nanopore technology and subsequent hybrid assembly in order to do in-depth characterisation of the ESC resistance plasmids. The 43 isolates belonged to 11 different sequence types, and three different ESC resistance gene/plasmid combinations were present, namely, IncK2/bla CMY-2 (n = 29), IncI1/bla CMY-2 (n = 6) and IncI1/bla CTX-M-1 (n = 8). ESC-resistant E. coli of different STs and with different ESC resistance gene/plasmid combinations could be present on the same farm, while a single ST and ESC resistance gene/plasmid displaying zero or few SNP differences were present on other farms. In-depth characterisation of IncK2/bla CMY-2 plasmids revealed that at least two distinct variants circulate in the broiler production. These plasmids showed close homology to previously published plasmids from other countries. Our longitudinal study show that ESC-resistant E. coli belong to a multitude of different STs and that different ESC resistance genes and plasmids occur. However, there is also indication of persistence of both ESC-resistant E. coli strains and IncK2/bla CMY-2 plasmids on farms. Further studies are warranted to determine the dynamics of strains, plasmids and ESC resistance genes within single broiler flocks.

Corrigendum: bla CTX-M-1/IncI1-Iγ Plasmids Circulating in Escherichia coli From Norwegian Broiler Production Are Related, but Distinguishable.

[This corrects the article DOI: 10.3389/fmicb.2020.00333.].

Interference of ISEcp1-blaCTX-M-1 with the shufflon rearrangement in IncI1 plasmids.

IncI1 plasmids are known disseminators of the extended-spectrum cephalosporin resistance (ESC) gene blaCTX-M-1, among species of the Enterobacteriaceae family. In several IncI1 plasmids, this gene was found incorporated into the transposition unit, ISEcp1-blaCTX-M-1-orf477, interrupting a shufflon region, a hallmark of IncI1 conjugative plasmids. The shufflon diversifies pilV gene that encodes the adhesine-type protein found on the tip of the conjugative pilus. To further elucidate the shufflon rearrangement, we examined to what extent the shufflon rearrangement was affected by the transposition-unit insertion. As expected, the interrupted shufflons generated a lower number of shufflon variants and exhibited an altered segment-deletion pattern compared to the non-interrupted shufflon. Interestingly, segment-loss frequency of the interrupted shufflons was distinctive in different plasmid hosts. Finally, the analysis of the 3' end of the pilV gene revealed that shufflon rearrangement favoured segment A to complete pilV partial open reading frame regardless of the shufflon. Thereby, it could be assumed that the A-segment has greater importance during conjugation, however, this remained a hypothesis. Further exploration of shufflon rearrangement and its importance in the plasmid-recipient selection during conjugation would be beneficial as the knowledge could be applied in developing a strategy to limit IncI1 mediated antimicrobial resistance dissemination.

Corrigendum: bla CTX-M-1 /IncI1-Iγ Plasmids Circulating in Escherichia coli From Norwegian Broiler Production Are Related, but Distinguishable.

[This corrects the article DOI: 10.3389/fmicb.2020.00333.].

Population structure and uropathogenic potential of extended-spectrum cephalosporin-resistant Escherichia coli from retail chicken meat.

BACKGROUND: Food-producing animals and their products are considered a source for human acquisition of antimicrobial resistant (AMR) bacteria, and poultry are suggested to be a reservoir for Escherichia coli resistant to extended-spectrum cephalosporins (ESC), a group of antimicrobials used to treat community-onset urinary tract infections in humans. However, the zoonotic potential of ESC-resistant E. coli from poultry and their role as extraintestinal pathogens, including uropathogens, have been debated. The aim of this study was to characterize ESC-resistant E. coli isolated from domestically produced retail chicken meat regarding their population genetic structure, the presence of virulence-associated geno- and phenotypes as well as their carriage of antimicrobial resistance genes, in order to evaluate their uropathogenic potential. RESULTS: A collection of 141 ESC-resistant E. coli isolates from retail chicken in the Norwegian monitoring program for antimicrobial resistance in bacteria from food, feed and animals (NORM-VET) in 2012, 2014 and 2016 (n = 141) were whole genome sequenced and analyzed. The 141 isolates, all containing the beta-lactamase encoding gene blaCMY-2, were genetically diverse, grouping into 19 different sequence types (STs), and temporal variations in the distribution of STs were observed. Generally, a limited number of virulence-associated genes were identified in the isolates. Eighteen isolates were selected for further analysis of uropathogen-associated virulence traits including expression of type 1 fimbriae, motility, ability to form biofilm, serum resistance, adhesion- and invasion of eukaryotic cells and colicin production. These isolates demonstrated a high diversity in virulence-associated phenotypes suggesting that the uropathogenicity of ESC-resistant E. coli from chicken meat is correspondingly highly variable. For some isolates, there was a discrepancy between the presence of virulence-associated genes and corresponding expected phenotype, suggesting that mutations or regulatory mechanisms could influence their pathogenic potential. CONCLUSION: Our results indicate that the ESC-resistant E. coli from chicken meat have a low uropathogenic potential to humans, which is important knowledge for improvement of future risk assessments of AMR in the food chains.

The Effect of Antimicrobial Resistance Plasmids Carrying blaCMY-2 on Biofilm Formation by Escherichia coli from the Broiler Production Chain.

Extended-spectrum cephalosporin-resistant Escherichia coli (ESCR E. coli) with plasmids carrying the blaCMY-2 resistance gene have been isolated from the Norwegian broiler production chain through the Norwegian monitoring program for antimicrobial resistance in animals, food and feed, NORM-VET. The aim of the present study was to investigate the biofilm forming abilities of these strains, and in particular to see whether these might be influenced by the carriage of blaCMY-2 plasmids. The ESCR E. coli from the broiler production chain displayed relatively low biofilm forming abilities in the crystal violet biofilm assay as compared to quinolone-resistant E. coli (QREC) from the same population (mean ± SD = 0.686 ± 0.686 vs. 1.439 ± 0.933, respectively). Acquisition of two different blaCMY-2 plasmids by QREC strains reduced their biofilm production in microtiter plates, but not their biofilm production on Congo Red agar plates. Furthermore, motility was reduced, but not planktonic growth. We hypothesize that genes carried by these plasmids may have caused the observed reduction in biofilm formation, possibly mediated through changes in flagellar expression or function. Furthermore, this may help explain the different biofilm forming abilities observed between ESCR E. coli and QREC. The results also indicate that the risk of biofilm reservoirs of antimicrobial resistant E. coli on in the broiler production is lower for ESCR E. coli than for QREC.

blaCTX-M-1/IncI1-Iγ Plasmids Circulating in Escherichia coli From Norwegian Broiler Production Are Related, but Distinguishable.

Escherichia coli carrying blaCTX-M-1 mediating resistance to extended-spectrum cephalosporins was recently described as a new genotype in Norwegian broiler production. The aim of this study was to characterize these isolates (n = 31) in order to determine whether the emergence of the genotype was caused by clonal expansion or horizontal dissemination of blaCTX-M-1-carrying plasmids. All included isolates were subjected to whole genome sequencing. Plasmid transferability was determined by conjugation, and plasmid replicons in the transconjugants were described using PCR-based replicon typing. Plasmid sizes were determined using S1 nuclease digestion. Plasmids in a subset of strains were reconstructed and compared to plasmids from broiler production in other European countries. The isolates belonged to nine different sequence types (STs), with the largest group being ST57 (n = 12). The vast majority of blaCTX-M-1-carrying plasmids were conjugative. All transconjugants were positive for the IncI1-Iγ replicon, and several also harbored the IncFIB replicon. Highly similar plasmids were present in different E. coli STs. Additionally, high similarity to previously published plasmids was detected. A reconstructed plasmid from an ST57 isolate harbored both IncI1-Iγ and IncFIB replicons and was considered to be co-integrated. The presence of one large plasmid was confirmed by S1 nuclease digestion. Our results show that dissemination of blaCTX-M-1 in Norwegian broiler production is due to both clonal expansion and horizontal transfer of plasmids carrying blaCTX-M-1. The blaCTX-M-1/IncI1-Iγ plasmids grouped into two main lineages, namely clonal complex (CC)-3 and CC-7. The genetic diversity at both strain and plasmid level indicates multiple introductions to Norway. We also show that the blaCTX-M-1 plasmids circulating in Norwegian broiler production are highly similar to plasmids previously described in other countries.

Biofilm forming properties of quinolone resistant Escherichia coli from the broiler production chain and their dynamics in mixed biofilms.

BACKGROUND: Quinolone resistant Escherichia coli (QREC) have been found in samples from Norwegian broiler chicken, despite quinolones not being administered to poultry in Norway. Biofilm production may be one factor contributing to the observed persistence in the broiler production chain. In the present study, 158 QREC strains from chicken caecal and retail meat samples were screened for biofilm production in microtiter plates, biofilm morphotype on Congo Red (CR) agar plates and phylotype by multiplex PCR. Furthermore, the dynamics in mixed biofilms with strains of different morphotypes were studied on glass slides and on CR agar plates. RESULTS: All strains but one produced biofilm in microtiter plates and/or on CR agar plates at room temperature. There were no differences between strains from chicken caecum and chicken retail meat in the mean amount of biofilm produced in microtiter plates. Furthermore, no differences in biofilm production were observed between phylotypes. However, significant differences in biofilm production were found between biofilm morphotypes. The morphotype RDAR (red dry and rough, which has both curli and cellulose in the matrix, was displayed by 70% of the strains. Mean biofilm production by these strains were significantly higher than by strains with the morphotypes PDAR (pink dry and rough) with only cellulose or BDAR (brown dry and rough) with only curli. Interestingly, the two latter morphotypes produced biofilms with the morphotype RDAR when grown together. None of the strains achieved significantly higher numbers of colony forming units (cfu) in mixed biofilms than in single strain biofilms on glass slides. CONCLUSIONS: The results indicate that QREC can form biofilm reservoirs on both inert and organic surfaces in production environments, as well as on meat. This may contribute to persistence and dissemination of the strains. Strains with both curli and cellulose in the biofilm matrix were significantly better biofilm formers than strains lacking one of these components. However, strains with only one of the components could compensate for this by producing mixed biofilms with strains having the other component, and thereby most likely enhance their probabilities of persistence in the production environment.

Occurrence of and risk factors for extended-spectrum cephalosporin-resistant Enterobacteriaceae determined by sampling of all Norwegian broiler flocks during a six month period.

All broiler flocks reared and slaughtered in Norway from May-October 2016 (n = 2110) were screened for the presence of extended-spectrum cephalosporin (ESC) -resistant Enterobacteriaceae. Furthermore, we investigated possible risk factors for occurrence of such bacteria in broiler flocks. The odds of a flock being positive for ESC-resistant Enterobacteriaceae increased if the previous flock in the same house was positive, and if the flock was reared during September-October. However, we cannot exclude seasonal fluctuations in occurrence of ESC-resistant Enterobacteriaceae during the months November to April. The overall occurrence of ESC-resistant Enterobacteriaceae was 10.4%, and primarily linked to the presence of blaCMY (82.6%) in positive isolates. We describe the first findings of Escherichia coli with blaCTX-M-1, Klebsiella pneumoniae with both blaCTX-M-15 and blaSHV-12, and K. pneumoniae with blaCMY isolated from Norwegian broiler production. This study gives us a unique overview and estimate of the true occurrence of ESC-resistant Enterobacteriaceae in Norwegian broilers over a six-month period. To the best of our knowledge, this is the most comprehensive study performed on the occurrence of ESC-resistant Enterobacteriaceae in a broiler population.

What does the fox say? Monitoring antimicrobial resistance in the environment using wild red foxes as an indicator.

The objective of this study was to estimate and compare the occurrence of AMR in wild red foxes in relation to human population densities. Samples from wild red foxes (n = 528) included in the Norwegian monitoring programme on antimicrobial resistance in bacteria from food, feed and animals were included. All samples were divided into three different groups based on population density in the municipality where the foxes were hunted. Of the 528 samples included, 108 (20.5%), 328 (62.1%) and 92 (17.4%) originated from areas with low, medium and high population density, respectively. A single faecal swab was collected from each fox. All samples were plated out on a selective medium for Enterobacteriaceae for culturing followed by inclusion and susceptibility testing of one randomly selected Escherichia coli to assess the overall occurrence of AMR in the Gram-negative bacterial population. Furthermore, the samples were subjected to selective screening for detection of E. coli displaying resistance towards extended-spectrum cephalosporins and fluoroquinolones. In addition, a subset of samples (n = 387) were subjected to selective culturing to detect E. coli resistant to carbapenems and colistin, and enterococci resistant to vancomycin. Of these, 98 (25.3%), 200 (51.7%) and 89 (23.0%) originated from areas with low, medium and high population density, respectively. Overall, the occurrence of AMR in indicator E. coli from wild red foxes originating from areas with different human population densities in Norway was low to moderate (8.8%). The total occurrence of AMR was significantly higher; χ2 (1,N = 336) = 6.53, p = 0.01 in areas with high population density compared to areas with medium population density. Similarly, the occurrence of fluoroquinolone resistant E. coli isolated using selective detection methods was low in areas with low population density and more common in areas with medium or high population density. In conclusion, we found indications that occurrence of AMR in wild red foxes in Norway is associated with human population density. Foxes living in urban areas are more likely to be exposed to AMR bacteria and resistance drivers from food waste, garbage, sewage, waste water and consumption of contaminated prey compared to foxes living in remote areas. The homerange of red fox has been shown to be limited thereby the red fox constitutes a good sentinel for monitoring antimicrobial resistance in the environment. Continuous monitoring on the occurrence of AMR in different wild species, ecological niches and geographical areas can facilitate an increased understanding of the environmental burden of AMR in the environment. Such information is needed to further assess the impact for humans, and enables implementation of possible control measures for AMR in humans, animals and the environment in a true "One Health" approach.

Transfer Potential of Plasmids Conferring Extended-Spectrum-Cephalosporin Resistance in Escherichia coli from Poultry.

Escherichia coli strains resistant to extended-spectrum cephalosporins (ESC) are widely distributed in Norwegian broiler production, and the majority harbor transferable IncK or IncI1 plasmids carrying blaCMY-2 Persistent occurrence in broiler farms may occur through the survival of ESC-resistant E. coli strains in the farm environment, or by transfer and maintenance of resistance plasmids within a population of environmental bacteria with high survival abilities. The aim of this study was to determine the transferability of two successful blaCMY-2-carrying plasmids belonging to the incompatibility groups IncK and IncI1 into E. coli and Serratia species recipients. Initially, conjugative plasmid transfer from two E. coli donors to potential recipients was tested in an agar assay. Conjugation was further investigated for selected mating pairs in surface and planktonic assays at temperatures from 12°C to 37°C. Transfer of plasmids was observed on agar, in broth, and in biofilm at temperatures down to 25°C. The IncK plasmid was able to transfer into Serratia marcescens, and transconjugants were able to act as secondary plasmid donors to different E. coli and Serratia species recipients. All transconjugants displayed an AmpC phenotype corresponding to the acquisition of blaCMY-2 In summary, the results indicate that the IncK plasmid may transfer between E. coli and Serratia spp. under conditions relevant for broiler production.IMPORTANCE Certain blaCMY-2-carrying plasmids are successful and disseminated in European broiler production. Traditionally, plasmid transferability has been studied under conditions that are optimal for bacterial growth. Plasmid transfer has previously been reported between E. coli bacteria in biofilms at 37°C and in broth at temperatures ranging from 8 to 37°C. However, intergenus transfer of blaCMY-2-carrying plasmids from E. coli to environmental bacteria in the food-processing chain has not been previously studied. We demonstrate that blaCMY-2-carrying plasmids are capable of conjugative transfer between different poultry-associated bacterial genera under conditions relevant for broiler production. Transfer to Serratia spp. and to hosts with good biofilm-forming abilities and with the potential to act as secondary plasmid donors to new hosts might contribute to the persistence of these resistance plasmids. These results contribute to increased knowledge of factors affecting the persistence of ESC resistance in broiler production and can provide a basis for improvement of routines and preventive measures.

Risk factors for occurrence of cephalosporin-resistant Escherichia coli in Norwegian broiler flocks.

A longitudinal study of 27 broiler farms including 182 broiler flocks was performed to determine risk factors for occurrence of cephalosporin-resistant Escherichia coli in Norwegian broiler flocks. Information regarding possible risk factors was collected by an online questionnaire and by samples obtained from broiler and parent flocks during the study period. Additional information was provided by the broiler production company. The prevalence of cephalosporin-resistant E. coli in parent flocks and broiler flocks sampled in the study was estimated. Cephalosporin-resistant E. coli was detected in 13.8% of the parent flocks and 22.5% of the broiler flocks included in the study. A multivariable generalized linear model was used to estimate risk factors. The risk for occurrence of cephalosporin-resistant E. coli was associated with the status of the previous flock in the broiler house (odds ratio=12.7), number of parent flocks supplying the broiler flock with day-old chickens (odds ratio=6.3), routines for disinfection of floor between production cycles (odds ratio=0.1), and transport personnel entering the room where the broilers are raised (odds ratio=9.3). Our findings highlights that implementation of a high level of biosecurity with a minimal number of people entering the broiler house during production cycles, as well as rigorous cleaning and disinfection routines between production cycles will contribute to a decrease in the occurrence of cephalosporin-resistant E. coli in broiler flocks provided that there is no selection pressure from antimicrobial use in the broiler production.

Plasmid and Host Strain Characteristics of Escherichia coli Resistant to Extended-Spectrum Cephalosporins in the Norwegian Broiler Production.

Escherichia coli resistant to extended-spectrum cephalosporins have been detected in the Norwegian broiler production, despite the fact that antimicrobial agents are rarely used. The genetic mechanism responsible for cephalosporin resistance is mainly attributed to the presence of the blaCMY-2 gene encoding a plasmid-mediated AmpC-beta-lactamase (pAmpC). The aim of this study was to characterize and compare blaCMY-2 containing Escherichia coli isolated from the intestinal flora of broilers and retail chicken meat (fillets) to identify possible successful clones and/or resistance plasmids widespread in the Norwegian broiler production. Methods used included PCR based phylotyping, conjugation experiments, plasmid replicon typing, pulsed-field gel electrophoresis, multiple locus variable-number tandem-repeats analysis and whole genome sequencing. The nucleotide sequence of an IncK plasmid carrying blaCMY-2 was determined. Intestinal isolates displayed a higher degree of genetic diversity than meat isolates. A cluster of genetically related isolates belonging to ST38, phylogroup D, carrying blaCMY-2 containing IncK plasmids was identified. Furthermore, genes encoding plasmid stability systems (relBE/stbDE and pndAC) were identified on the IncK plasmid. Single nucleotide polymorphism (SNP) analysis of a subset of isolates confirmed a close genetic relationship within the two most prevalent STs. The IncK plasmids within these two STs also shared a high degree of similarity. Cephalosporin-resistant E. coli with the same genetic characteristics have been identified in the broiler production in other European countries, and the IncK plasmid characterized in this study showed close homology to a plasmid isolated from retail chicken meat in the Netherlands. The results indicate that both clonal expansion and horizontal transfer of blaCMY-2 containing plasmids contribute to dissemination of cephalosporin resistant E. coli in the broiler production. The presence of plasmid stability systems may explain why the IncK plasmid containing blaCMY-2 is maintained and disseminated in the Norwegian broiler production in absence of selection pressure from the use of antimicrobial agents.

Emergence of AmpC-producing Escherichia coli in the broiler production chain in a country with a low antimicrobial usage profile.

The aim of this study was to estimate the prevalence of cephalosporin-resistant Escherichia coli at the different levels of the Norwegian broiler production pyramid and identify the mechanisms responsible for the resistance phenotype. Samples from all levels of the broiler production pyramid and retail chicken meat (fillets) were included (n=649). The occurrence of cephalosporin-resistant E. coli at the different production levels ranged from 8 to 43%. All these isolates had an AmpC-phenotype, and the majority carried the blaCMY-2 gene. In addition, a few isolates with up-regulated chromosomal ampC were identified. The results show that Norway has a relatively high prevalence of cephalosporin-resistant E. coli in the broiler production chain in spite of a very low consumption of antimicrobial agents. Cephalosporins have not been used in the Norwegian broiler production, and it has been hypothesised that import of breeding animals and hatching eggs may be the source of these resistant bacteria. We demonstrate that these bacteria are disseminated in the production pyramid despite the lack of selection pressure from antimicrobial agents.