Multidrug resistance in Salmonella isolates of swine origin: mobile genetic elements and plasmids associated with cephalosporin resistance with potential transmission to humans

The emergence of foodborne Salmonella strains carrying antimicrobial resistance (AMR) in mobile genetic elements (MGE) is a significant public health threat in a One Health context requiring continuous surveillance. Resistance to ciprofloxacin and cephalosporins is of particular concern. Since pigs are a relevant source of foodborne Salmonella for human beings, we studied transmissible AMR genes and MGE in a collection of 83 strains showing 9 different serovars and 15 patterns of multidrug resistant (MDR) previously isolated from pigs raised in the conventional breeding system of Northern Spain. All isolates were susceptible to ciprofloxacin and three isolates carried blaCMY-2 or blaCTX-M-9 genes responsible for cefotaxime resistance. Filter mating experiments showed that the two plasmids carrying blaCTX-M-9 were conjugative while that carrying blaCMY-2 was self-transmissible by transformation. Whole-genome sequencing and comparative analyses were performed on the isolates and plasmids. The IncC plasmid pSB109, carrying blaCMY-2, was similar to one found in S. Reading from cattle, indicating potential horizontal transfer between serovars and animal sources. The IncHI2 plasmids pSH102 in S. Heidelberg and pSTM45 in S. Typhimurium ST34, carrying blaCTX-M-9, shared similar backbones and two novel "complex class 1 integrons" containing different AMR and heavy metal genes. Our findings emphasize the importance of sequencing techniques to identify emerging AMR regions in conjugative and stable plasmids from livestock production. The presence of MGE carrying clinically relevant AMR genes raises public health concerns, requiring monitoring to mitigate the emergence of bacteria carrying AMR genes and subsequent spread through animals and food.IMPORTANCEThe emergence of foodborne Salmonella strains carrying antimicrobial resistance (AMR) in mobile genetic elements (MGE) is a significant public health threat in a One Health context. Since pigs are a relevant source of foodborne Salmonella for humans, in this study, we investigate different aspects of AMR in a collection of 83 Salmonella showing nine different serovars and 15 patterns of multidrug resistant (MDR) isolated from pigs raised in the conventional breeding system. Our findings emphasize the importance of sequencing techniques to identify emerging AMR regions in conjugative and stable plasmids from livestock production. The presence of MGE carrying clinically relevant AMR genes raises public health concerns, requiring monitoring to mitigate the emergence of bacteria carrying AMR genes and subsequent spread through animals and food.

Detection of ESBL and AmpC producing Klebsiella pneumoniae ST11 and ST147 from urinary tract infections in Iran

In the present study a total of 200 Klebsiella pneumoniae isolates were collected from patients with urinary tract infections (UTIs) in Tehran, Iran. Antibiotic resistance was determined by disk diffusion and broth dilution methods. Detection of extended-spectrum β-lactamases (ESBLs) and AmpCs was performed using phenotypic tests. Polymerase chain reaction (PCR) was applied to detect the ESBL, AmpC, and integron genes. Analysis of AmpC and cassette arrays of integron genes was performed using DNA sequencing. Plasmids were analyzed by PCR-based replicon typing and conjugation. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were applied to explore the genomic relatedness among the isolates. The highest levels of resistance were observed against ampicillin (100%), followed by piperacillin (57.5%), ceftazidime (46%), trimethoprim/sulfamethoxazole (44%), ciprofloxacin (32.5%), and imipenem (19%). Approximately, 66.5% of isolates harbored at least one of the beta-lactamase genes (blaTEM, blaSHV, blaCTX-M, and blaOXA-1). In addition, 22.5% of isolates carried at least one of the AmpC genes including blaDHA and blaCIT. Integron class I was the most prevalent integron among resistant isolates. According to the results of replicon typing, IncFII, IncL/M, and IncA/C were the most frequent replicons, respectively. All selected isolates were able to transfer blaCTX-M, also two isolates transferred the blaDHA-1 gene to Escherichia coli K12 through conjugation. Finally, 21 isolates were categorized into 4 pulsotypes and 11 unique clusters in PFGE. MLST identified ST147 and ST11 sequence types but ST147 was the most prevalent in the current study.

Deciphering the fate of antibiotic resistance genes in norfloxacin wastewater treated by a bio-electro-Fenton system

The misuse of antibiotics has increased the prevalence of antibiotic resistance genes (ARGs), considered a class of critical environmental contaminants due to their ubiquitous and persistent nature. Previous studies reported the potentiality of bio-electro-Fenton processes for antibiotic removal and ARGs control. However, the production and fate of ARGs in bio-electro-Fenton processes triggered by microbial fuel cells are rare. In this study, the norfloxacin (NFLX) average residual concentrations within two days were 2.02, 6.07 and 14.84 mg/L, and the average removal efficiency of NFLX was 79.8 %, 69.6 % and 62.9 % at the initial antibiotic concentrations of 10, 20 and 40 mg/L, respectively. The most prevalent resistance gene type in all processes was the fluoroquinolone antibiotic gene. Furthermore, Proteobacteria was the dominant ARG-carrying bacteria. Overall, this study can provide theoretical support for the efficient treatment of high antibiotics-contained wastewater by bio-electro-Fenton systems to better control ARGs from the perspective of ecological security.

Tracking Antimicrobial Resistant E. coli from Pigs on Farm to Pork at Slaughter

Antimicrobial-resistant bacteria might be transferred via the foodchain. However, that risk is rarely tracked along different production steps, e.g., from pigs at farm to meat. To close that gap, we performed a prospective study in four conventional and two organic farms from the moment pigs entered the farm until meat sampling at slaughter. Antimicrobial use was recorded (0 to 11 agents). Antimicrobial susceptibility (AMS) against 26 antibiotics, including critically important substances, was tested by microdilution, and tetA-tetB-sulI-sulII-strA-strB-bla-CTXM-qacEΔ1 were included in PCR-genotyping. From 244 meat samples of 122 pigs, 54 samples (22.1%) from 45 animals were positive for E. coli (n = 198). MICs above the breakpoint/ECOFF occurred for all antibiotics except meropenem. One isolate from organic farming was markedly resistant against beta-lactams including fourth-generation cefalosporines. AMS patterns differed remarkably between isolates from one piece of meat, varying from monoresistance to 16-fold multiresistance. Amplicon-typing revealed high similarity between isolates at slaughter and on farm. Prior pig lots andeven the farmer might serve as reservoirs for E. coli isolated from meat at slaughter. However, AMS phenotyping and genotyping indicate that antimicrobial resistance in E. coli is highly dynamic, impairing reliable prediction of health risks from findings along the production chain.

Dynamics of Salmonella enterica and antimicrobial resistance in the Brazilian poultry industry and global impacts on public health

Non-typhoidal Salmonella enterica is a common cause of diarrhoeal disease; in humans, consumption of contaminated poultry meat is believed to be a major source. Brazil is the world’s largest exporter of chicken meat globally, and previous studies have indicated the introduction of Salmonella serovars through imported food products from Brazil. Here we provide an in-depth genomic characterisation and evolutionary analysis to investigate the most prevalent serovars and antimicrobial resistance (AMR) in Brazilian chickens and assess the impact to public health of products contaminated with S. enterica imported into the United Kingdom from Brazil. To do so, we examine 183 Salmonella genomes from chickens in Brazil and 357 genomes from humans, domestic poultry and imported Brazilian poultry products isolated in the United Kingdom. S. enterica serovars Heidelberg and Minnesota were the most prevalent serovars in Brazil and in meat products imported from Brazil into the UK. We extended our analysis to include 1,259 publicly available Salmonella Heidelberg and Salmonella Minnesota genomes for context. The Brazil genomes form clades distinct from global isolates, with temporal analysis suggesting emergence of these Salmonella Heidelberg and Salmonella Minnesota clades in the early 2000s, around the time of the 2003 introduction of the Enteritidis vaccine in Brazilian poultry. Analysis showed genomes within the Salmonella Heidelberg and Salmonella Minnesota clades shared resistance to sulphonamides, tetracyclines and beta-lactams conferred by sul2, tetA and bla_CMY-2 genes, not widely observed in other co-circulating serovars despite similar selection pressures. The sul2 and tetA genes were concomitantly carried on IncC plasmids, whereas bla_CMY-2 was either co-located with the sul2 and tetA genes on IncC plasmids or independently on IncI1 plasmids. Long-term surveillance data collected in the UK showed no increase in the incidence of Salmonella Heidelberg or Salmonella Minnesota in human cases of clinical disease in the UK following the increase of these two serovars in Brazilian poultry. In addition, almost all of the small number of UK-derived genomes which cluster with the Brazilian poultry-derived sequences could either be attributed to human cases with a recent history of foreign travel or were from imported Brazilian food products. These findings indicate that even should Salmonella from imported Brazilian poultry products reach UK consumers, they are very unlikely to be causing disease. No evidence of the Brazilian strains of Salmonella Heidelberg or Salmonella Minnesota were observed in UK domestic chickens. These findings suggest that introduction of the Salmonella Enteritidis vaccine, in addition to increasing antimicrobial use, could have resulted in replacement of salmonellae in Brazilian poultry flocks with serovars that are more drug resistant, but less associated with disease in humans in the UK. The plasmids conferring resistance to beta-lactams, sulphonamides and tetracyclines likely conferred a competitive advantage to the Salmonella Minnesota and Salmonella Heidelberg serovars in this setting of high antimicrobial use, but the apparent lack of transfer to other serovars present in the same setting suggests barriers to horizontal gene transfer that could be exploited in intervention strategies to reduce AMR. The insights obtained reinforce the importance of One Health genomic surveillance.

Non-typhoidal Salmonella enterica is a common cause of diarrhoeal disease; in humans, consumption of contaminated poultry meat is believed to be a major source. Here we determine that S. enterica serovars Heidelberg and Minnesota were the most prevalent serovars in Brazilian poultry and in poultry products imported from Brazil into the UK. However, long-term surveillance data collected by the UK Health Security Agency showed no increase in the incidence of Salmonella Heidelberg or Salmonella Minnesota in human cases of clinical disease in the UK following the increase of these two serovars in Brazilian poultry. Salmonella Heidelberg and Salmonella Minnesota clades shared resistance to sulphonamides, tetracyclines and beta-lactams conferred by sul2, tetA and bla_CMY-2 genes, not widely observed in other co-circulating serovars despite similar selection pressures. The sul2 and tetA genes were concomitantly carried on IncC plasmids, whereas bla_CMY-2 was either co-located with the sul2 and tetA genes on IncC plasmids or independently on IncI1 plasmids. These findings suggest that introduction of the Salmonella Enteritidis vaccine, in addition to increasing antimicrobial use, could have resulted in replacement of salmonellae in Brazilian poultry flocks with serovars that are more drug resistant, but less associated with disease in humans in the UK.

Antimicrobial susceptibility, plasmid replicon typing, phylogenetic grouping, and virulence potential of avian pathogenic and faecal Escherichia coli isolated from meat chickens in Australia

Globally, avian colibacillosis is a leading cause of morbidity and mortality in poultry, associated with economic losses and welfare problems. Here, clinical avian pathogenic E. coli isolates (CEC; n=50) and faecal E. coli isolates from healthy (FEC; n=187) Australian meat chickens collected between 2006 and 2014 were subjected to antimicrobial susceptibility testing, phylogenetic grouping, plasmid replicon (PR) typing, multilocus sequence typing, and virulence gene (VG) profiling. Extended-spectrum cephalosporin (ESC)- and fluoroquinolone (FQ)-resistant E. coli isolates underwent further genetic characterisation. Significant proportions of CEC and FEC were respectively susceptible (13/50 [26%]; 48/187 [26%],) or MDR (9/50 [18%]; 26/187 [14%]) to 20 tested antimicrobials. Phylogenetic groups A and C, and PR types IncFIB and IncFrep were most commonly represented. Five tested CEC-associated VGs were more prevalent in CEC (≥90%) compared to FEC isolates (≤58%). Some isolates (CEC n=3; FEC n=7) were resistant to ESCs and/or FQs and possessed signature mutations in chromosomal FQ target genes and plasmid-mediated qnrS, bla_CMY-2, and bla_DHA-1 genes. Sequence type 354 (n=4), associated with extraintestinal infections in a broad range of hosts, was prevalent among the ESC- and/or FQ-resistant FEC.This study confirmed the existence of a small reservoir of ESC- and FQ-resistant E. coli in Australian commercial meat chickens despite the absence of use in the industry of these drug classes. Otherwise, a diversity of VGs and PR types in both faecal and clinical E. coli populations were identified. It's hypothesised that the source of ESC- and FQ-resistant E. coli may be external to poultry production facilities.Highlights1. Low-level resistance to older and newer generation antimicrobial drugs detected2. The most common sequence type (ST) associated with FQ resistance was ST354 (4/10)3. A small proportion of CEC (n=3) and FEC (n=7) were resistant to ESCs and/or FQs.

PLASmid TAXonomic PCR (PlasTax-PCR), a Multiplex Relaxase MOB Typing to Assort Plasmids into Taxonomic Units

Plasmids transmissible by conjugation are responsible for disseminating antibiotic-resistance genes, making plasmid detection relevant for pathogen tracking. We describe the use of a multiplex PCR method for the experimental identification of specific plasmid taxonomic units (PTUs) of transmissible plasmids. The PCR primers were designed to target conserved segments of the relaxase MOB gene of PTUs encoding adaptive traits for enterobacteria (antimicrobial resistance, virulence, and metabolism). In this way, PlasTax-PCR detects the presence of these plasmids and allows their direct assignation to a PTU.

Genetic Characterization of AmpC and Extended-Spectrum Beta-Lactamase Phenotypes in Escherichia coli and Salmonella From Alberta Broiler Chickens

Horizontal gene transfer is an important mechanism which facilitates bacterial populations in overcoming antimicrobial treatment. In this study, a total of 120 Escherichia coli and 62 Salmonella enterica subsp. enterica isolates were isolated from broiler chicken farms in Alberta. Fourteen serovars were identified among Salmonella isolates. Thirty one percent of E. coli isolates (37/120) were multiclass drug resistant (resistant to ≥ 3 drug classes), while only about 16% of Salmonella isolates (10/62) were multiclass drug resistant. Among those, eight E. coli isolates had an AmpC-type phenotype, and one Salmonella isolate had an extended-spectrum beta-lactamase (ESBL)-type beta-lactamase phenotype. We identified both AmpC-type (bla_CMY-2) and ESBL-type (bla_TEM) genes in both E. coli and Salmonella isolates. Plasmids from eight of nine E. coli and Salmonella isolates were transferred to recipient strain E. coli J53 through conjugation. Transferable plasmids in the eight E. coli and Salmonella isolates were also transferred into a lab-made sodium azide-resistant Salmonella recipient through conjugation. The class 1 integrase gene, int1, was detected on plasmids from two E. coli isolates. Further investigation of class 1 integron cassette regions revealed the presence of an aadA gene encoding streptomycin 3’’-adenylyltransferase, an aadA1a/aadA2 gene encoding aminoglycoside 3’’-O-adenyltransferase, and a putative adenylyltransferase gene. This study provides some insight into potential horizontal gene transfer events of antimicrobial resistance genes between E. coli and Salmonella in broiler chicken production.

Genetic diversity and co-prevalence of ESBLs and PMQR genes among plasmid-mediated AmpC β-lactamase-producing Klebsiella pneumoniae isolates causing urinary tract infection

Klebsiella pneumoniae is an opportunistic pathogen that frequently causes nosocomial urinary tract infection (UTI). The aim of this study was to investigate the prevalence of extended-spectrum β-lactamases (ESBL), plasmid-mediated quinolone resistance (PMQR) genes, in acquired AmpC (ac-AmpC) β‑lactamase‑producing K. pneumoniae isolates from patients with nosocomial UTI and to characterize the transmissibility of plasmids harbouring multiple resistance genes. From January 2017 to June 2018, we collected 46 ac-AmpC-producing K. pneumoniae isolates causing UTI from a tertiary care hospital in China. Antimicrobial susceptibility assays showed that non-susceptibility of all isolates to third-generation cephalosporin and fluoroquinolone was very high (>80%). Diverse types of ESBLs and PMQR genes, including bla_SHV-12 (n = 23), bla_SHV-27 (n = 1)_, bla_SHV-28 (n = 2)_, bla_SHV-33 (n = 4), bla_CTX-M-3 (n = 24)_, bla_CTX-M-14 (n = 6)_, bla_CTX-M-15 (n = 6)_, bla_CTX-M-22 (n = 1) and bla_OXA-10 (n = 26)_, as well as qnrA (n = 2), qnrB (n = 39) and qnrS (n = 2) genes were identified amongst AmpC-producing K. pneumoniae isolates. The bla_AmpC, qnrB and several ESBLs genes from six strains harbouring multiple AmpC (at least two ampC) were co-transferrable to recipients via conjugation or electroporation, with IncFIA, IncFIB and IncA/C being the dominant replicons. Conserved genetic context associated with the mobilization of bla_ampC genes was detected. Forty-six isolates were categorized into 25 enterobacterial repetitive intergenic consensus (ERIC) types, and the 6 isolates harbouring multiple AmpC genes belonged to ST1 lineage. This work reports that the emergence of plasmids co-harbouring multiple resistance determinants and mediating the local prevalence in K. pneumoniae causing UTI in China.

Resistance of Klebsiella pneumoniae Strains Carrying bla NDM-1 Gene and the Genetic Environment of bla NDM-1

OBJECTIVE

Regional dissemination is the major cause of the widespread prevalence of a plasmid-encoding NDM-1 enzyme. We investigated the drug resistance, joint efficiency, and gene environment of a Klebsiella pneumoniae strain carrying bla NDM-1 gene.

MATERIALS AND METHODS

Carbapenem-non-susceptible strains were analyzed using the VITEK 2 Compact. Strains carrying bla NDM-1 were identified using polymerase chain reaction and sequencing. Antimicrobial susceptibility testing and plasmid conjugation experiments were then conducted. Strains carrying bla NDM-1 were subjected to Southern blot analysis. After the gene mapping of bla NDM-1, library construction, and sequencing, plasmids were subsequently spliced and genotyped using the software Glimmer 3.0, and then analyzed using Mauve software.

RESULTS

Among 1735 carbapenem-non-susceptible strains, 54 strains of bla NDM-1-positive bacteria were identified, which consisted of 44 strains of K. pneumoniae, 8 strains of Acinetobacter baumannii and 2 strains of Escherichia coli. Strains carrying bla NDM-1 had a resistance rate of more than 50% in most antibiotics. Plasmid conjugation between strains carrying bla NDM-1 and E. coli strain J53 had a success rate of 50%. Southern blot analysis indicated that each strain had multiple plasmids containing bla NDM-1. Among the five plasmids containing bla NDM-1 in K. pneumoniae for sequencing, two plasmids with complete sequences were obtained. The findings were as follows: (i) The p11106 and p12 plasmids were highly similar to pNDM-BTR; (ii) the p11106 and p12 plasmids showed differences in the 20-30 kb region (orf00032-orf00043) from the other six plasmids; and (iii) bla NDM-1 was located at orf00037, while ble was found at orf00038. Two tnpA genes were located in the upstream region, and orf00052 (tnpA) in the 36 kb region was in the downstream sequence.

CONCLUSION

bla NDM-1-containing bacteria exhibit multidrug resistance, which rapidly spreads and is transferred through efficient plasmid conjugation; the multidrug resistance of these bacteria may be determined by analyzing their drug-resistant plasmids. The presence of ble and tnpA genes suggests a possible hypothesis that bla NDM-1 originates from A. baumannii, which is retained in K. pneumoniae over a long period by transposition of mobile elements.

Molecular Characterization of Fecal Extended-Spectrum β-Lactamase- and AmpC β-Lactamase-Producing Escherichia coli From Healthy Companion Animals and Cohabiting Humans in South Korea

This study aimed to describe the distribution and characterization of fecal extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli isolates from healthy companion animals and cohabiting humans. A total of 968 rectal swab samples from 340 participants, including healthy companion animals and cohabiting humans, were collected from 130 households in South Korea from 2018 to 2019. To determine the bacterial profiles of the participants, several experiments were performed as follows: antimicrobial susceptibility testing, PCR and direct sequencing for ESBL/AmpC production, PFGE, MLST, whole genome sequencing and qRT-PCR. A total of 24.9 and 21.5% of the E. coli isolates from healthy companion animals and cohabiting humans were ESBL/AmpC producers, respectively. The bla_CTX–M–14 gene was the most prevalent ESC resistance gene in both pets (n = 25/95, 26.3%) and humans (n = 44/126, 34.9%). The bla_CMY–2 gene was also largely detected in pets (n = 19, 20.0%). Overall, intrahousehold pet-human sharing of ESBL/AmpC E. coli isolates occurred in 4.8% of households, and the isolates were all CTX-M-14 producers. In particular, ten CMY-2-producing E. coli isolates from seven dogs and three humans in the different households belonged to the same pulsotype. The MIC values of cefoxitin and the transcription level in CMY-2-producing E. coli isolates were proportional to the bla_CMY–2 copy number on the chromosome. Our results showed that the clonal spread of fecal ESBL/AmpC-producing E. coli households’ isolates between healthy companion animals and cohabiting humans was rare, but it could happen. In particular, E. coli ST405 isolates carrying multiple bla_CMY–2 genes on the chromosome was sporadically spread between companion animals and humans in South Korea.

Dynamics of clonal and plasmid backgrounds of Enterobacteriaceae producing acquired AmpC in Portuguese clinical settings over time

OBJECTIVES

The objective of this work was to provide detailed molecular data on clinically acquired AmpC (qAmpC)-producing Enterobacteriaceae from two different periods (2002-2008 and 2010-2013) in order to clarify the contribution of clonal and plasmid genetic platforms for the current epidemiological scenario concerning extended-spectrum beta-lactams resistance.

METHODS

We analysed 1246 Enterobacteriaceae non-susceptible to third-generation cephalosporins from two hospitals and one community laboratory between 2010 and 2013. Bacterial identification, antibiotic susceptibility, identification of qAmpC and plasmid-mediated quinolone resistance genes, clonal (pulsed-field gel electrophoresis (PFGE), Multilocus sequence typing (MLST)) and plasmid (S1-/I-CeuI-PFGE, replicon typing, hybridization) analysis were performed by standard methods. Whole-genome sequencing (WGS) was performed in two ST11-Klebsiella pneumoniae isolates harbouring DHA-1.

RESULTS

The occurrence of qAmpC was lower (2.6%) than that observed in a previous survey (7.4%), and varied slightly over time. Isolates produced DHA-1 (53%), CMY-2 (44%) or DHA-6 (3%), but significant epidemiological changes were observed in the two surveys. While DHA-1 persisted in different institutions by selection of a worldwide epidemic IncR plasmid in an ST11 harbouring KL105, CMY-2 rates increased over time linked to IncI1 plasmids (instead of IncK or IncA/C₂) in multiple Escherichia coli clones.

CONCLUSIONS

The higher frequency of DHA-1 qAmpC in these species contrasts with the scenario in most European countries. Furthermore, the different genetic backgrounds associated with either extended-spectrum β-lactamases (ESBLs) or acquired AmpC β-lactamases (qAmpC) in our country might have contributed to their differential expansion.

Acquisition of plasmid-mediated cephalosporinase producing Enterobacteriaceae after a travel to the tropics

Travelers are at high risk of acquiring multi-drug resistant Enterobacteriaceae (MRE) while traveling abroad. Acquisition of extended spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E) while traveling has been extensively described, but not that of plasmid-mediated cephalosporinase producing Enterobacteriaceae (pAmpC-E). Here, we characterized the pAmpC-E acquired in 574 French travelers to tropical areas enrolled in the VOYAG-R study. Among the 526 MRE isolated at return, 57 (10.8%) from 49 travelers were pAmpC-E. The acquisition rate of pAmpC-E was 8.5% (49/574) ranging from 12.8% (25/195) in Asia, 7.6% (14/184) in Latin America to 5.1% (10/195) in Africa. The highest acquisition rates were observed in Peru (21.9%), India (21.4%) and Vietnam (20%). The carriage of pAmpC-E decreased quickly after return with 92.5% of colonized travelers being negative at one month. Most enzymes were CMY types (96.5%, n = 55, only met in Escherichia coli), including 40 CMY-2 (70.2%), 12 CMY-42 (21.1%), 1 CMY-6 and two new CMY-2 variants. The remaining were two DHA observed in Klebsiella pneumoniae. CMY-2 producing strains were acquired worldwide whereas CMY-42, except for one, were all acquired in Asia. Bla_CMY-2 genes were associated with different plasmid types, including IncI1 (45. 2%), IncF (10%), IncF-IncI (7.5%), IncA/C (5%) and IncR (2.5%) whereas bla_CMY-42 were all associated with IncI1 plasmids. Even though the pAmpC-E acquisition rate was much lower than that of ESBL-E, it was significant, especially in Asia, showing that pAmpC-E, especially CMY-type producing E. coli have spread in the community settings of tropical regions.

ISEcp1-mediated transposition of chromosome-borne blaCMY-2 into an endogenous ColE1-like plasmid in Escherichia coli

Background

CMY-2 is the most prevalent pAmpC β-lactamase, but the chromosomal bla_CMY-2 gene transfer via horizontal transmission has been seldom reported. This study aimed to describe an ISEcp1-mediated transposition of a chromosomal bla_CMY-2 gene from Escherichia coli into a small endogenous ColE1-like plasmid, resulting in elevated resistance to extended-spectrum cephalosporins.

Methods

Three ESCs-resistant ST641 E. coli strains EC6413, EC4103 and EC5106 harbored the bla_CMY-2 gene. S1-PFGE, I-ceu I-PFGE, Southern blotting and electroporation experiments were performed to investigate the location and transferability of bla_CMY-2. The genetic context and gene expression of bla_CMY-2 in the original isolates and the corresponding electroporants were explored by PCR mapping, primer walking strategy and RT-qPCR.

Results

The bla_CMY-2-containing region (ISEcp1-bla_CMY-2-∆blc-∆yggR-∆tnp1-orf7-orf8-orf9-∆tnp2-∆hsdR) was transposed into endogenous ColE1-like plasmid pSC137 in the process of electroporation at very low frequencies (10^-8-10^-9). The transpositions resulted in novel larger bla_CMY-2-harboring ColE1-like plasmids with size of 14,845 bp, enabling increase in MICs of 2 to 8-fold for cefotaxime, ceftiofur, and ceftazidime in recipient strains over their respective original counterparts. Transcriptional level analysis revealed that the increased bla_CMY-2 expression was correlated with elevated MIC values of cephalosporins. The bla_CMY-2 transposition unit was identical to that in a clinical isolate E. coli TN44889 from France isolated in 2004.

Conclusions

Our results firstly demonstrated that ISEcp1 mediated a transposition of chromosome-borne bla_CMY-2 into an endogenous ColE1-like plasmid by electroporation. Amplification of the bla_CMY-2 gene facilitates the strain adaptation to a changed environment with an elevated antibiotic pressure.

Genetic Environment of blaTEM-1, blaCTX-M-15, blaCMY-42 and Characterization of Integrons of Escherichia coli Isolated From an Indian Urban Aquatic Environment

The presence of antibiotic resistance genes (ARGs) including those expressing ESBLs and AmpC-β-lactamases in Escherichia coli inhabiting the aquatic environments is a serious health problem. The situation is further complicated by the fact that ARGs can be easily transferred among bacterial species with the help of mobile genetic elements – plasmids, integrons, insertion sequences (IS), and transposons. Therefore, the analysis of genetic environment and mobile genetic elements associated with ARGs is important as these provide useful information about the epidemiology of these genes. In our previous study, we had reported presence of various β-lactam resistance genes present in E. coli strains inhabiting the river Yamuna traversing the National Capital Territory of Delhi (India). In the present study, we have analyzed the genetic environment of three ARGs bla_TEM-1, bla_CTX-M-15, and bla_{CMY -42} of those E. coli strains. The structure of class 1 integrons and their gene cassettes was also analyzed. Insertion sequence IS26 was present upstream of bla_TEM-1, ISEcp1 was present upstream of bla_CTXM-15 gene and orf477 was present downstream of bla_CTXM-15. ISEcp1 was also present upstream of bla_{CMY -42} and, blc and sugE genes were present in the downstream region of this gene. Thus, the overall genetic environment surrounding these genes was similar to that reported from E. coli strains isolated globally. Conjugation assays, isolation and analysis of plasmid DNA of the transconjugants indicated that bla_TEM-1, bla_CTX-M-15, bla_{CMY -42} and class 1 integron were plasmid-mediated and possibly transmit between genera through horizontal gene transfer (HGT). This might lead to dissemination of antimicrobial resistance genes in aquatic environment. The work embodied in this paper is the first describing the genetic environment of bla and integrons in aquatic E. coli isolated from India.

Occurrence of bla DHA-1 mediated cephalosporin resistance in Escherichia coli and their transcriptional response against cephalosporin stress: a report from India

Background

Treatment alternatives for DHA-1 harboring strains are challenging as it confers resistance to broad spectrum cephalosporins and may further limit treatment option when expressed at higher levels. Therefore, this study was designed to know the prevalence of DHA genes and analyse the transcription level of DHA-1 against different β-lactam stress.

Methods

Screening of AmpC β-lactamase phenotypically by modified three dimensional extract method followed by Antimicrobial Susceptibility and MIC determination. Genotyping screening of β-lactamase genes was performed by PCR assay followed by their sequencing. The bla_DHA-1 transcriptional response was evaluated under different cephalosporin stress by RT PCR. Transferability of bla_DHA gene was performed by transformation and conjugation and plasmid incompatibility typing, DNA fingerprinting by enterobacterial repetitive intergenic consensus sequences PCR.

Results

16 DHA-1 genes were screened positive from 176 Escherichia coli isolates and primer extension analysis showed a significant increase in DHA-1 mRNA transcription in response to cefotaxime at 8 µg/ml (6.99 × 10² fold), ceftriaxone at 2 µg/ml (2.63 × 10³ fold), ceftazidime at 8 µg/ml (7.06 × 10³ fold) and cefoxitin at 4 µg/ml (3.60 × 10⁴ fold) when compared with untreated strain. These transcription data were found significant when analyzed statistically using one way ANOVA. Four different ESBL genes were detected in 10 isolates which include CTX-M (n = 6), SHV (n = 4), TEM (n = 3) and OXA-10 (n = 1), whereas, carbapenemase gene (NDM) was detected only in one isolate. Other plasmid mediated AmpC β-lactamases CIT (n = 9), EBC (n = 2) were detected in nine isolates. All DHA-1 genes detected were encoded in plasmid and incompatibility typing from the transformants indicated that the plasmid encoding bla_DHA-1 was carried mostly by the FIA and L/M Inc group.

Conclusion

This study demonstrates the prevalence of DHA-1 gene in this region and highlights high transcription of DHA-1 when induced with different β-lactam antibiotics. Therefore, cephalosporin treatment must be restricted for the patients infected with pathogen expressing this resistance determinant.

IncHI2 Plasmids Are Predominant in Antibiotic-Resistant Salmonella Isolates

The wide usage of antibiotics contributes to the increase in the prevalence of antibiotic-resistant Salmonella. Plasmids play a critical role in horizontal transfer of antibiotic resistance markers in Salmonella. This study aimed to screen and characterize plasmid profiles responsible for antibiotic resistance in Salmonella and ultimately to clarify the molecular mechanism of transferable plasmid-mediated antibiotic resistance. A total of 226 Salmonella isolates were examined for antimicrobial susceptibility by a disk diffusion method. Thirty-two isolates (14.2%) were resistant to at least one antibiotic. The presence of plasmid-mediated quinolone resistance (PMQR) genes and β-lactamase genes were established by PCR amplification. PCR-based replicon typing revealed that these 32 isolates represented seven plasmid incompatibility groups (IncP, HI2, A/C, FIIs, FIA, FIB, and I1), and the IncHI2 (59.4%) was predominant. Antibiotic resistance markers located on plasmids were identified through plasmid curing. Fifteen phenotypic variants were obtained with the curing efficiency of 46.9% (15/32). The cured plasmids mainly belong to the HI2 incompatibility group. The elimination of IncHI2 plasmids correlated with the loss of β-lactamase genes (blaOXA-1 and blaTEM-1) and PMQR genes (qnrA and aac(6')-Ib-cr). Both IncHI2 and IncI1 plasmids in a S. enterica serovar Indiana isolate SJTUF 10584 were lost by curing. The blaCMY -2-carrying plasmid pS10584 from SJTUF 10584 was fully sequenced. Sequence analysis revealed that it possessed a plasmid scaffold typical for IncI1 plasmids with the unique genetic arrangement of IS1294-ΔISEcp1-blaCMY -2-blc-sugE-ΔecnR inserted into the colicin gene cia. These data suggested that IncHI2 was the major plasmid lineage contributing to the dissemination of antibiotic resistance in Salmonella and the activity of multiple mobile genetic elements may contribute to antibiotic resistance evolution and dissemination between different plasmid replicons.

A multi-drug resistant Salmonella Typhimurium ST213 human-invasive strain (33676) containing the bla CMY-2 gene on an IncF plasmid is attenuated for virulence in BALB/c mice

Background

Classical strains of Salmonella enterica serovar Typhimurium (Typhimurium) predominantly cause a self-limiting diarrheal illness in humans and a systemic disease in mice. In this study, we report the characterization of a strain isolated from a blood-culture taken from a 15-year old woman suffering from invasive severe salmonellosis, refractory to conventional therapy with extended-spectrum cephalosporin (ESC).

Results

The strain, named 33676, was characterized as multidrug-resistant Salmonella serogroup A by biochemical, antimicrobial and serological tests. Multilocus sequence typing (MLST) and XbaI macrorestrictions (PFGE) showed that strain 33676 belonged to the Typhimurium ST213 genotype, previously described for other Mexican Typhimurium strains. PCR analyses revealed the presence of IncA/C, IncFIIA and ColE1-like plasmids and the absence of the Salmonella virulence plasmid (pSTV). Conjugation assays showed that the ESC-resistance gene bla_CMY-2 was carried on the conjugative IncF plasmid, instead of the IncA/C plasmid, as found in previously studied ST213 strains. Although the IncA/C plasmid conferred most of the observed antimicrobial resistances it was not self-conjugative; it was rather able to conjugate by co-integrating with the IncF plasmid. Strain 33676 was fully attenuated for virulence in BALB/c mice infections. Both type-three secretion system (T3SS), encoded in Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2), were functional in the 33676 strain and, interestingly, this strain produced the H2 FljB flagellin instead of the H1 FliC flagellin commonly expressed by S. enterica strains.

Conclusions

Strain 33676 showed two main features that differentiate it from the originally described ST213 strains: 1) the bla_CMY-2 gene was not carried on the IncA/C plasmid, but on a conjugative IncF plasmid, which may open a new route of dissemination for this ESC-resistance gene, and 2) it expresses the H2 FljB flagella, in contrast with the other ST213 and most Typhimurium reference strains. To our knowledge this is the first report of an IncF bla_CMY-2-carrying plasmid in Salmonella.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0633-7) contains supplementary material, which is available to authorized users.

Frequency of Plasmid-Mediated AmpC β-Lactamases in Escherichia coli Isolates from Urine Samples in São Paulo, Brazil

Plasmid-mediated AmpC β-lactamases (PMACBLs) in Enterobacteriaceae encode resistance to third-generation cephalosporins, and these can mediate carbapenem resistance when associated with porin loss. However, no standardized phenotypic method is available for detecting these enzymes in the clinical microbiology laboratory. Limited data are available concerning the frequency of PMACBLs in Enterobacteriaceae in Brazil. This study was conducted in response to an increased cefoxitin (CFO) resistance rate of 3.7% in Escherichia coli isolates from urine samples from patients with suspected urinary tract infections during 2010. We collected 2,266 E. coli isolates prospectively during January 2012. A total of 109 (4.8%) isolates were nonsusceptible to CFO. These strains were further examined using multiplex PCR for the presence of genes encoding PMACBLs and using inhibitor assays with CFO and ceftazidime (CAZ) disks with and without phenylboronic acid. Pulsed-field gel electrophoresis was used to evaluate clonal dissemination. Genes encoding PMACBLs were detected in 1.8% of the isolates from inpatients and 0.46% of isolates from outpatients. The most prevalent gene was blaCMY-2 and blaCMY-4 was also detected. The phenotypic analysis showed 100% sensitivity and specificity for CMY-2 and CMY-4 when CFO-resistant isolates with a minimum zone diameter difference of 5 mm for CAZ or CAZ and CFO were considered positive. Although most of the isolates were nonclonal, one clonal group with two isolates was observed. Thus, the most frequent PMACBL in E. coli from São Paulo, Brazil is CMY-2, and both clonal and plasmid-mediated dissemination occur.

Molecular characterisation of acquired and overproduced chromosomal blaAmpC in Escherichia coli clinical isolates

Escherichia coli recovered from three hospitals in Barcelona (Spain) were studied to determine the prevalence of isolates with acquired AmpC (ac-AmpC) and/or overproduced chromosomal AmpC (c-AmpC). Mechanisms involved in blac-AmpC overexpression, blaac-AmpC and the plasmids associated with their distribution as well as the prevalence of plasmid-mediated quinolone resistance (PMQR) in AmpC-producing isolates were also determined. Isolates were selected according to their resistance phenotype. blaac-AmpC, alterations in the blac-AmpC promoter/attenuator, and PMQR genes [qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA] were characterised by PCR and sequencing. blac-AmpC expression was determined by qRT-PCR. Population structure analysis was performed using PFGE, MLST and phylogenetic group PCR. Plasmids carrying blaac-AmpC were characterised by PCR-based replicon typing and S1-PFGE. IncI1 and IncF plasmids were also analysed by plasmid MLST and replicon sequence typing, respectively. Among 21563 E. coli isolates, 240 (1.1%) overproduced AmpC β-lactamases, including 180 (75.0%) harbouring ac-AmpC (132 CMY-2 variants and 48 DHA-1) and 60 (25.0%) c-AmpC enzymes. Three mutation profiles in the blac-AmpC promoter/attenuator were associated with a 72.5-, 19.9- and 5.8-fold increased expression, respectively. Moreover, 63.3% of ac-AmpC and 43.3% of c-AmpC isolates belonged to B2, D, E or F phylogenetic groups. PMQR was found in 31% of ac-AmpC isolates [38 qnrB4, 8 aac(6')-Ib-cr, 6 qnrS1 and 3 qnrB19] and in 10% of c-AmpC isolates [5 aac(6')-Ib-cr and 1 qnrS1]. IncI1-ST12 and IncF were associated with blaCMY-2 and blaDHA-1, respectively. These results suggest that ac-AmpC β-lactamases were the main mechanism of AmpC production. Isolates and plasmids both showed high genetic diversity.

Characterization of Beta-lactamases in Faecal Enterobacteriaceae Recovered from Healthy Humans in Spain: Focusing on AmpC Polymorphisms

The intestinal tract is a huge reservoir of Enterobacteriaceae, some of which are opportunist pathogens. Several genera of these bacteria harbour intrinsic antibiotic resistance genes, such as ampC genes in species of Citrobacter, Enterobacter or Escherichia genera. In this work, beta-lactamases and other resistance mechanisms have been characterized in Enterobacteriaceae isolates recovered from healthy human faecal samples, focusing on the ampC beta-lactamase genes. Fifty human faecal samples were obtained, and 70 Enterobacteriaceae bacteria were isolated: 44 Escherichia coli, 4 Citrobacter braakii, 9 Citrobacter freundii, 8 Enterobacter cloacae, 1 Proteus mirabilis, 1 Proteus vulgaris, 1 Klebsiella oxytoca, 1 Serratia sp. and 1 Cronobacter sp. A high percentage of resistance to ampicillin was detected (57%), observing the AmpC phenotype in 22 isolates (31%) and the ESBL phenotype in 3 isolates. AmpC molecular characterization showed high diversity into bla CMY and bla ACT genes from Citrobacter and Enterobacter species, respectively, and the pulsed-field gel electrophoresis (PFGE) analysis demonstrated low clonality among them. The prevalence of people colonized by strains carrying plasmid-mediated ampC genes obtained in this study was 2%. The unique plasmid-mediated bla AmpC identified in this study was the bla CMY-2 gene, detected in an E. coli isolate ascribed to the sequence type ST405 which belonged to phylogenetic group D. The hybridization and conjugation experiments demonstrated that the ISEcp1-bla CMY-2-blc structure was carried by a ~78-kb self-transferable IncK plasmid. This study shows a high polymorphism among beta-lactamase genes in Enterobacteriaceae from healthy people microbiota. Extensive AmpC-carrier studies would provide important information and could allow the anticipation of future global health problems.

Mobile genetic elements related to the diffusion of plasmid-mediated AmpC β-lactamases or carbapenemases from Enterobacteriaceae: findings from a multicenter study in Spain

We examined the genetic context of 74 acquired ampC genes and 17 carbapenemase genes from 85 of 640 Enterobacteriaceae isolates collected in 2009. Using S1 pulsed-field gel electrophoresis and Southern hybridization, 37 of 74 bla AmpC genes were located on large plasmids of different sizes belonging to six incompatibility groups. We used sequencing and PCR mapping to investigate the regions flanking the acquired ampC genes. The bla CMY-2-like genes were associated with ISEcp1; the surrounding bla DHA genes were similar to Klebsiella pneumoniae plasmid pTN60013 associated with IS26 and the psp and sap operons; and the bla ACC-1 genes were associated with IS26 elements inserted into ISEcp1. All of the carbapenemase genes (bla VIM-1, bla IMP-22, and bla IMP-28) were located in class 1 integrons. Therefore, although plasmids are the main cause of the rapid dissemination of ampC genes among Enterobacteriaceae, we need to be aware that other mobile genetic elements, such as insertion sequences, transposons, or integrons, can be involved in the mobilization of these genes of chromosomal origin. Additionally, three new integrons (In846 to In848) are described in this study.

Dissemination of the chromosomally encoded CMY-2 cephalosporinase gene in Escherichia coli isolated from animals

In this study, 619 individual Escherichia coli isolates from food-producing and companion animals were analysed to determine the prevalence of the cephalosporinase gene blaCMY-2. In total, 18 CMY-2-producers (2.9%) were detected and exhibited multidrug-resistant phenotypes. One of the CMY-2-producers was found to possess a novel blaCMY-2-like allele, blaCMY-130. The isolates belonged to distinct pulsotypes, suggesting that the blaCMY-2 gene was not disseminated by clonal expansion of blaCMY-2-positive strains. The blaCMY-2 genes were located on IncA/C-, IncHI2- or IncX-type plasmids in 9 (50%) of the 18 E. coli isolates. However, in the other nine isolates I-CeuI-PFGE and hybridisation analyses revealed that the blaCMY-2 gene was chromosomally located. A CMY gene-containing region composed of five open reading frames (ORFs) (ISEcp1-blaCMY-2-blc-sugE-ΔencR) was observed in plasmids from eight strains. A CMY gene-containing region composed of ten ORFs was observed in all of the nine chromosomally encoded blaCMY-2 genes, including a putative IS66-like element inserted in this conserved CMY genetic region in three strains. This conserved CMY genetic region was also found to be inserted into the oriVγ (putative gamma origin), part of the IncX plasmid backbone, by a complete transposition unit flanked by 5-bp DRs (direct repeat sequence) in pS62T. These results demonstrate the high prevalence of the chromosomally encoded blaCMY-2 gene in E. coli. This is the first study reporting a chromosomally encoded blaCMY-2 gene in E. coli. Chromosomally encoded blaCMY-2 might be a source of some plasmid-mediated blaCMY-2 genes and this probably facilitates the spread of cephalosporin-resistant strains.

Degenerate primer MOB typing of multiresistant clinical isolates of E. coli uncovers new plasmid backbones

Degenerate Primer MOB Typing is a PCR-based protocol for the classification of γ-proteobacterial transmissible plasmids in five phylogenetic relaxase MOB families. It was applied to a multiresistant E. coli collection, previously characterized by PCR-based replicon-typing, in order to compare both methods. Plasmids from 32 clinical isolates of multiresistant E. coli (19 extended spectrum beta-lactamase producers and 13 non producers) and their transconjugants were analyzed. A total of 95 relaxases were detected, at least one per isolate, underscoring the high potential of these strains for antibiotic-resistance transmission. MOBP12 and MOBF12 plasmids were the most abundant. Most MOB subfamilies detected were present in both subsets of the collection, indicating a shared mobilome among multiresistant E. coli. The plasmid profile obtained by both methods was compared, which provided useful data upon which decisions related to the implementation of detection methods in the clinic could be based. The phylogenetic depth at which replicon and MOB-typing classify plasmids is different. While replicon-typing aims at plasmid replication regions with non-degenerate primers, MOB-typing classifies plasmids into relaxase subfamilies using degenerate primers. As a result, MOB-typing provides a deeper phylogenetic depth than replicon-typing and new plasmid groups are uncovered. Significantly, MOB typing identified 17 plasmids and an integrative and conjugative element, which were not detected by replicon-typing. Four of these backbones were different from previously reported elements.

Ordering the bestiary of genetic elements transmissible by conjugation

Phylogenetic reconstruction of three highly conserved proteins involved in bacterial conjugation (relaxase, coupling protein and a type IV secretion system ATPase) allowed the classification of transmissible elements in relaxase MOB families and mating pair formation MPF groups. These evolutionary studies point to the existence of a limited number of module combinations in transmissible elements, preferentially associated with specific genetic or environmental backgrounds. A practical protocol based on the MOB classification was implemented to detect and assort transmissible plasmids and integrative elements from γ-Proteobacteria. It was called “Degenerate Primer MOB Typing” or DPMT. It resulted in a powerful technique that discovers not only backbones related to previously classified elements (typically by PCR-based replicon typing or PBRT), but also distant new members sharing a common evolutionary ancestor. The DPMT method, conjointly with PBRT, promises to be useful to gain information on plasmid backbones and helpful to investigate the dissemination routes of transmissible elements in microbial ecosystems.

High prevalence of carbapenem resistance among plasmid-mediated AmpC β-lactamase-producing Klebsiella pneumoniae during outbreaks in liver transplantation units

During a prospective surveillance using PCR for the detection of plasmid-mediated AmpC β-lactamase (pAmpC)-producing Enterobacteriaceae, outbreaks due to pAmpC-producing Klebsiella pneumoniae (pAmpC-Kp) occurred in an adult liver transplantation unit (aLTU) and a paediatric liver transplantation unit (pLTU), with carbapenem-resistant (CR) variants. Between April 2010 and March 2012, a total of 32 patients infected with pAmpC-Kp were found by prospective surveillance using PCR detection at a Japanese university hospital. Multilocus sequence typing, analysis of outer membrane proteins, and detection of carbapenemases were performed. Clinical courses of patients with bloodstream infection (BSI) were reviewed. Of 32 pAmpC-Kp isolates from each patient, 20 (18 from aLTU patients) were DHA-1-producing sequence type 11 (DHA-1-ST11), 9 were CMY-2-ST45/778 (all from pLTU patients) and the other 3 isolates had different sequence types. CR variants were isolated from 8 aLTU patients with DHA-1-ST11 and from 1 pLTU patient with CMY-2-ST45. All of the pAmpC-Kp isolates, including CR variants, were negative for carbapenemases. All of the DHA-1-ST11 and CMY-2-ST45 isolates lacked OmpK35, and seven CR variants also lacked OmpK36. BSIs due to DHA-1-ST11 isolates, including CR variants, occurred in six aLTU patients, four of whom died. The outbreaks were controlled after application of intensified infection control measures. During pAmpC-Kp outbreaks involving 27 liver transplants, CR variants with porin loss developed in nine patients, and DHA-1-ST11 K. pneumoniae caused BSIs with high mortality.

Complete sequencing of IncI1 sequence type 2 plasmid pJIE512b indicates mobilization of blaCMY-2 from an IncA/C plasmid

Sequencing of pJIE512b, a 92.3-kb IncI1 sequence type 2 (ST2) plasmid carrying bla(CMY-2), revealed a bla(CMY-2) context that appeared to have been mobilized from an IncA/C plasmid by the insertion sequence IS1294. A comparison with published plasmids suggests that bla(CMY-2) has been mobilized from IncA/C to IncI1 plasmids more than once by IS1294-like elements. Alignment of pJIE512b with the only other available IncI1 ST2 plasmid revealed differences across the backbones, indicating variability within this sequence type.

Molecular characterization of DHA-1-producing Klebsiella pneumoniae isolates collected during a 4-year period in an intensive care unit

Seventeen Klebsiella pneumoniae isolates producing DHA-1 β-lactamase were collected in an intensive care unit between 2006 and 2010. Molecular analysis revealed the predominance of ST48 and ST1263 clones of K. pneumoniae and the spread of DHA-1-encoding plasmids belonging to incompatibility group IncL/M or IncHI2.

Expansive spread of IncI1 plasmids carrying blaCMY-2 amongst Escherichia coli

Escherichia coli is a leading cause of urinary tract infections. One of the most common antibiotic classes used to treat such infections is the β-lactams, including cephalosporins. Resistance to the third-generation cephalosporins can be caused by production of extended-spectrum β-lactamases (ESBLs) or plasmid-mediated AmpC β-lactamases. The most commonly reported AmpC β-lactamase in E. coli is CMY-2. Plasmid-mediated CMY-2 has been frequently reported in E. coli and Salmonella sp. from food-producing animals. This study aimed to elucidate the molecular characteristics of clinical E. coli isolates carrying plasmids encoding CMY-2. A total of 67 CMY-2-producing E. coli were characterised by clonal analysis and phylogenetic typing. Characterisation of the plasmids carrying blaCMY-2 included replicon typing, plasmid profiling, plasmid transferability and sequencing of the blaCMY-2 genetic environment. As a result, E. coli producing CMY-2 was found to be highly polyclonal. The majority of CMY-2-producing E. coli belonged to phylogenetic group D. IncI1 plasmids were predominant among those carrying blaCMY-2 (96%). Restriction analysis revealed a single IncI1 plasmid carrying blaCMY-2 to be predominant and present in different clones of E. coli. IS1294-ISEcp1 complex or ISEcp1 that was truncated by IS1294 was the predominant insertion sequence upstream of blaCMY-2. The homogeneous genetic environment of blaCMY-2 observed among different strains of E. coli strongly suggests horizontal transfer of this IncI1, blaCMY-2-carrying plasmid. In summary, horizontal plasmid transfer plays a major role in the spread of blaCMY-2 in E. coli.

Diversity of extended-spectrum and plasmid-mediated AmpC β-lactamases in Enterobacteriaceae isolates from Portuguese health care facilities

A group of 124 Enterobacteriaceae isolates resistant to third generation cephalosporins, and collected in distinct health care facilities of different Portuguese regions was analysed. The great majority of the isolates were also resistant to fourth generation cephalosporins (83.9%), monobactam (96%), amoxicillin plus clavulanic acid (85.5%), and piperacillin plus tazobactam (66.9%). Overall, 84.7% (105/124) were multidrug resistant. Molecular methods enabled us to identify 86.3% (107/124) extended-spectrum β-lactamases (ESBL) producers, revealing a diversity of class A β-lactamases from different families, like TEM (TEM-1, TEM-10, TEM-24, and TEM-52), SHV (SHV-1, SHV-12, and SHV-28), CTX-M (CTX-M-1, CTX-M-9, CTX-M-14, CTX-M-15, and CTXM-32), and GES (GES-1). We have also detected class C enzymes like plasmid-mediated AmpC β-lactamases (PMAβs, DHA-1, and CMY-2) and chromosomal AmpCs in Enterobacter and Citrobacter spp. The PMAβ genetic context mapping suggests association with mobile elements, plasmid importation and the potential emergence of these β-lactamases. The most prevalent β-lactamase detected was CTX-M-15 (66.1%) and in 41.1% of the isolates it was associated with TEM-, OXA-type β-lactamases and Aac(6)᾿Ib-cr, which might indicate that the respective genotype has settled in our country. Indeed, CTX-M-15 was distributed amongst distinct clinical settings of several health care facilities (93.5%) from various regions. We provide evidence of a concerning clinical situation that includes vast occurrence of ESBLs, the settling of CTX-M β-lactamases, and the report of plasmidic and chromosomal AmpC in Portugal.

IncA/C plasmid-mediated spread of CMY-2 in multidrug-resistant Escherichia coli from food animals in China

Objectives

To obtain a broad molecular epidemiological characterization of plasmid-mediated AmpC β-lactamase CMY-2 in Escherichia coli isolates from food animals in China.

Methods

A total of 1083 E. coli isolates from feces, viscera, blood, drinking water, and sub-surface soil were examined for the presence of CMY-2 β-lactamases. CMY-2-producing isolates were characterized as follows: the bla_CMY-2 genotype was determined using PCR and sequencing, characterization of the bla_CMY-2 genetic environment, plasmid sizing using S1 nuclease pulsed-field gel electrophoresis (PFGE), PCR-based replicon typing, phylogenetic grouping, XbaI-PFGE, and multi-locus sequence typing (MLST).

Results

All 31 CMY-2 producers were only detected in feces, and presented with multidrug resistant phenotypes. All CMY-2 strains also co-harbored genes conferring resistance to other antimicrobials, including extended spectrum β-lactamases genes (bla_CTX-M-14 or bla_CTX-M-55), plasmid-mediated quinolone resistance determinants (qnr, oqxA, and aac-(6′)-Ib-cr), floR and rmtB. The co-transferring of bla_CMY-2 with qnrS1 and floR (alone and together) was mainly driven by the Inc A/C type plasmid, with sizes of 160 or 200 kb. Gene cassette arrays inserted in the class 1 or class 2 integron were amplified among 12 CMY-2 producers. CMY-2 producers belonged to avirulent groups B1 (n = 12) and A (n = 11), and virulent group D (n = 8). There was a good correlation between phylogenetic groups and sequence types (ST). Twenty-four STs were identified, of which the ST complexes (STC) 101/B1 (n = 6), STC10/A (n = 5), and STC155/B1 (n = 3) were dominant.

Conclusions

CMY-2 is the dominant AmpC β-lactamase in food animals and is associated with a transferable replicon IncA/C plasmid in the STC101, STC10, and STC155 strains.

First description of NDM-1-, KPC-2-, VIM-2- and IMP-4-producing Klebsiella pneumoniae strains in a single Chinese teaching hospital

A total of 180 non-duplicate carbapenem-resistant Klebsiella pneumoniae isolates were recovered from patients hospitalized between December 2010 and January 2012 at a Chinese hospital. Eight KPC-2, four NDM-1, one VIM-2, and five KPC-2 plus IMP-4 producers were identified and all were multidrug resistant due to the presence of other resistance determinants, including extended-spectrum β-lactamases (CTX-M-15, SHV-12), 16S rRNA methylases (armA, rmtB) and plasmid-mediated quinolone-resistance determinants (qnrA, B, S, aac(6')-Ib-cr). Nine K. pneumoniae clones (Kpn-A1/ST395, Kpn-A3/ST11, Kpn-A2/ST134, Kpn-B/ST263, Kpn-C/ST37, Kpn-D/ST39, Kpn-E/ST1151, Kpn-F/ST890, Kpn-G/ST1153) were identified. bla KPC-2 was located on transferable ~65 kb IncL/M (ST395, ST11, ST134, ST39) and ~100 kb IncA/C (ST37, ST1153, ST890) plasmids, respectively. On the other hand, bla NDM-1 was associated with a ~70 kb IncA/C plasmid (ST263). However, non-typable plasmids of ~40 kb containing bla VIM-2 were detected in the ST1151 clone. This work reports the first co-occurrence of four diverse types of carbapenemase of K. pneumoniae clones from a single hospital in China. IncA/C, IncL/M, and other successful plasmids may be important for the dissemination of carbapenemases, producing a complex epidemiological picture.

Risk factors of community-onset urinary tract infections caused by plasmid-mediated AmpC β-lactamase-producing Enterobacteriaceae

BACKGROUND

The AmpC β-lactamase (AmpC)-producing Enterobacteriaceae emerged worldwide. This study was conducted to determine the risk factors of community-onset urinary tract infections (UTIs) caused by plasmid-mediated AmpC-producing Enterobacteriaceae.

METHODS

Patients who were diagnosed as community-onset UTIs caused by Enterobacteriaceae in a tertiary-care teaching hospital from December 2010 to January 2012 were included. Extended-spectrum β-lactamase (ESBL)-producing isolates were excluded. We identified plasmid-mediated AmpC-producing Enterobacteriaceae both phenotypically (by disk potentiation test and double-disk synergy test) and genotypically (by Multiplex polymerase chain reaction (PCR) assay). The demographic data, clinical characteristics, and risk factors of acquisition were described.

RESULTS

Among the 323 non-ESBL-producing Enterobacteriaceae identified in community-onset UTIs, 50 isolates were phenotypically positive for AmpC. Escherichia coli was the most common AmpC-producing organism (60%), followed by Klebsiella pneumonia (8%), and Enterobacter cloacae and Proteus mirabilis (6% for each species). The independent risk factors for acquisition of AmpC-producing Enterobacteriaceae included prior history of cerebral vascular accident [odds ratio (OR) = 2.014; 95% confidence interval (CI) = 1.007-4.031; p = 0.0048], and prior use of fluoroquinolones (OR = 4.049; 95% CI = 1.759-9.319; p = 0.001) and cephamycin (OR = 9.683; 95% CI = 2.007-45.135; p = 0.004). AmpC-producing isolates were multidrug resistant. Carbapenems, cefepime, and piperacillin/tazobactam had the best in vitro efficacy. The most commonly identified plasmid-mediated AmpC gene was bla(CIT), followed by bla(DHA)/bla(EBC), and bla(MOx).

CONCLUSION

For community-onset UTIs, AmpC-producing Enterobacteriaceae should be suspected in those with prior history of cerebral vascular accident and prior use of antimicrobials. To treat these multiple-resistant isolates, carbapenems, cefepime, and piperacillin/tazobactam may be considered.

Long-term dissemination of acquired AmpC β-lactamases among Klebsiella spp. and Escherichia coli in Portuguese clinical settings

We investigated the occurrence, diversity and molecular epidemiology of genes coding for acquired AmpC β-lactamases (qAmpC) among clinical isolates of Enterobacteriaceae lacking inducible chromosomal AmpCs in Portugal. A total of 675 isolates non-susceptible to broad-spectrum cephalosporins obtained from four hospitals and three community laboratories during a 7-year period (2002-2008) were analysed. The presence of genes coding for qAmpC was investigated by phenotypic criteria, polymerase chain reaction (PCR) and sequencing. Bacterial identification, antibiotic susceptibility testing, conjugation assays and clonal analysis were performed by standard procedures. The presence of bla(qAmpC) genes was detected in 50 % (50/100; 41 Klebsiella pneumoniae, 5 Escherichia coli, 4 Klebsiella oxytoca) of the presumptive qAmpC producers. DHA-1, detected in those species, was the most prevalent qAmpC (94 %, 47/50), being identified since 2003 and throughout the studied period in different institutions. Despite the high clonal diversity observed, three DHA-1-producing Klebsiella spp. clones were more frequently identified. CMY-2 (6 %, 3/50) was observed in B1-E. coli clones. Conjugative transfer was only observed in one (2 %) CMY-2-producing isolate. Most qAmpC producers (94 %, 47/50) co-expressed SHV-type and/or OXA-1 or CTX-M-32 extended-spectrum β-lactamases (ESBLs). To the authors' knowledge, this is the first description of the molecular epidemiology and the long-term dissemination of qAmpC-producing Enterobacteriaceae in Portuguese clinical settings, highlighting an evolution towards a more complex epidemiological situation regarding cephalosporin resistance in Portugal.

Identification of the first blaCMY-2 gene in Salmonella enterica serovar Typhimurium isolates obtained from cases of paediatric diarrhoea illness detected in South America

The objectives of this study were to investigate clinical isolates of Salmonella enterica serovar Typhimurium resistant to β-lactam antibiotics, to characterise their mechanisms of antibiotic resistance and to evaluate the possible biological cost of expressing resistance genes. Two oxyimino-cephalosporin-resistant Salmonella isolates obtained from children with diarrhoea were characterised. The occurrence of plasmid-encoded bla_CMY-2 genes was confirmed by molecular methods and conjugation assays; transcription levels were determined by quantitative real-time PCR (qRT-PCR). The genomic context of the β-lactamases, replicon type and addiction systems were analysed by PCR. Genomic relatedness of both isolates was studied by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) assays. Growth curves, motility and invasiveness assays in Caco-2 cells were performed to analyse the bacterial fitness of both isolates. Both isolates carried a bla_CMY-2-like allele in an IncI plasmid and belonged to the same MLST sequence type (ST19); nevertheless, they showed extensive differences in their PFGE profiles and virulotypes. Isolate STM709 appeared to lack the Salmonella virulence plasmid and displayed less motility and invasiveness in cultured cells than isolate STM910. qRT-PCR showed that isolate STM709 had higher bla_CMY-2 mRNA levels compared with STM910. Altogether, the results suggest that a plasmid carrying bla_CMY-2 could be disseminating among different clones of S. Typhimurium. Different levels of bla_CMY-2 mRNA could have an effect on the fitness of this micro-organism, resulting in lower invasiveness and motility.

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

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