First detection of NDM-1 with CTX-M-9, TEM, SHV and rmtC in Escherichia coli ST471 carrying IncI2, A/C and Y plasmids from clinical isolates in Turkey

Resistance pattern of isolated microorganisms from 783 clinical specimen cultures in patients admitted to Yasuj Educational Hospitals, Iran

BACKGROUND

Infectious diseases are still one of the leading causes of morbidity and mortality in resource-limited settings. Serious infection caused mostly by gram-negative pathogens causes significant morbidity. According to the Centers for Disease Control and Prevention, antimicrobial resistance kills over 700,000 people worldwide. Antibiotic resistance is on the rise, and as a consequence, serious public health issues are arising. The present study investigated isolated clinical samples from Yasuj teaching hospitals to determine the antimicrobial resistance profile to various antibiotics.

MATERIALS AND METHODS

Microbial isolates regarding cultures from urine, blood, wound, abdominal tap, throat, stool, cerebrospinal fluid, endotracheal tube, sputum, skin lesion, nasal, and mouth secretion were collected from patients admitted to hospitals affiliated with Yasuj teaching hospitals. Antibiotic susceptibility profiles were determined by using the Kirby-Bauer disc diffusion method. Data were tabulated and analyzed with SPSS version 26.0.

RESULTS

A total of 783 samples were evaluated in our study, with an average of 30.6 years and 54.5% female patients. Most of the bacterial isolates were gram-negative (64.2%). The majority of cultures were Escherichia coli (49.9%), mainly among urine samples (64.2%). The frequency distribution of norfloxacin antibiotic resistance was more common in internal medicine (66.7%), infectious (63.6%), and emergency wards (58.8%). The frequency distribution of penicillin antibiotic resistance was statistically significant in different wards. All cases of oxacillin were resistant.

CONCLUSION

Our data showed a high level of antibiotic resistance among bacterial isolates in our center. Considering widespread empirical antibiotic therapy in Iran, the rate of increasing resistance to common antibiotics prescribed for ambulatory and hospitalized patients is concerning. We recommend providing more strict guidelines and policies to control the overuse and overprescription of antimicrobials by health policy-making organizations.

Occurrence of High-Risk Clonal Lineages ST58, ST69, ST224, and ST410 among Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Healthy Free-Range Chickens (Gallus gallus domesticus) in a Rural Region in Tunisia

Antimicrobial-resistant Escherichia coli isolates have emerged in various ecologic compartments and evolved to spread globally. We sought to (1.) investigate the occurrence of ESBL-producing E. coli (ESBL-Ec) in feces from free-range chickens in a rural region and (2.) characterize the genetic background of antimicrobial resistance and the genetic relatedness of collected isolates. Ninety-five feces swabs from free-range chickens associated with two households (House 1/House 2) in a rural region in northern Tunisia were collected. Samples were screened to recover ESBL-Ec, and collected isolates were characterized for phenotype/genotype of antimicrobial resistance, integrons, and molecular typing (pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST)). Overall, 47 ESBL-Ec were identified, with the following genes detected: 35 bla_CTX-M-1, 5 bla_CTX-M-55, 5 bla_CTX-M-15, 1 bla_SHV-2, and 1 bla_SHV-12. Resistance to fluoroquinolones, tetracycline, sulfonamides, and colistin was encoded by aac(6')-Ib-cr (n = 21), qnrB (n = 1), and qnrS (n = 2); tetA (n = 17)/tetB (n = 26); sul1 (n = 29)/sul2 (n = 18); and mcr-2 (n = 2) genes, respectively. PFGE and MLST identified genetic homogeneity of isolates in House 1; however, isolates from House 2 were heterogeneous. Notably, among nine identified sequence types, ST58, ST69, ST224, and ST410 belong to pandemic high-risk clonal lineages associated with extrapathogenic E. coli. Minor clones belonging to ST410 and ST471 were shared by chickens from both households. The virulence genes fyuA, fimH, papGIII, and iutA were detected in 35, 47, 17, and 23 isolates, respectively. Findings indicate a high occurrence of ESBL-Ec in free-range chickens and highlight the occurrence of pandemic zoonotic clones.

Research Updates of Plasmid-Mediated Aminoglycoside Resistance 16S rRNA Methyltransferase

With the wide spread of multidrug-resistant bacteria, a variety of aminoglycosides have been used in clinical practice as one of the effective options for antimicrobial combinations. However, in recent years, the emergence of high-level resistance against pan-aminoglycosides has worsened the status of antimicrobial resistance, so the production of 16S rRNA methyltransferase (16S-RMTase) should not be ignored as one of the most important resistance mechanisms. What is more, on account of transferable plasmids, the horizontal transfer of resistance genes between pathogens becomes easier and more widespread, which brings challenges to the treatment of infectious diseases and infection control of drug-resistant bacteria. In this review, we will make a presentation on the prevalence and genetic environment of 16S-RMTase encoding genes that lead to high-level resistance to aminoglycosides.

Coexistence of bla NDM-1 and rmtC on a Transferrable Plasmid of a Novel ST192 Klebsiella aerogenes Clinical Isolate

Introduction

The occurrence and development of antibiotic resistance are mainly caused by the spread of large plasmids carrying multiple antibiotic resistance genes. Recently, the association between 16S rRNA methyltransferase genes and β-lactamase genes carried by the same plasmid is of concern.

Methods

The Klebsiella aerogenes 1564 was isolated from the catheter tip of a patient in a tertiary hospital, Shanghai, China. The presence of the bla _NDM-1 and rmtC genes were assessed by PCR. Complete sequence of plasmid p1564 was determined. The K. aerogenes 1564 was characterized by antimicrobial susceptibility testing, Carbapenemase phenotype confirmation testing, conjugation experiment, S1-PFGE and multilocus sequence typing (MLST).

Results

Herein, we found that a New Delhi Metallo-β-lactamase-1 gene (bla _NDM-1) and a 16S rRNA methyltransferase gene (rmtC) coexisted on a transferrable plasmid of a carbapenem-resistant K. aerogenes clinical isolate. The K. aerogenes clinical isolate was found to belong to a novel sequence type 192 (ST192) determined by MLST. The sequencing results of the plasmid p1564 carrying bla _NDM-1 gene and rmtC gene showed that the size and guanine-cytosine content of the plasmid were 136, 902 bp and 51.8%, with 164 putative ORFs and two multidrug resistance gene islands. In addition to bla _NDM-1and rmtC, the plasmid contained bleomycin resistance gene (ble _MBL), CMY-6β-lactamase gene (bla _CMY-6), quaternary ammonium compound resistance gene (sugE), truncated quaternary ammonium compound resistance gene (qacEΔ1), aminoglycoside resistance gene (aacA4) and sulfonamide resistance gene (sul1). By comparison, p1564 has high homology with pHS36-NDM from Salmonella enterica subsp. enterica serovar Stanley reported in China, with similar size and both belonging to plasmid incompatibility group A/C.

Conclusion

The present study demonstrated for the first time the co-existence of rmtC and bla _NDM-1 in a novel ST192 K. aerogenes. The spread of plasmids harboring both bla _NDM-1 and rmtC may occur among Enterobacteriaceae in China.

Epidemiology and Mechanisms of Resistance of Extensively Drug Resistant Gram-Negative Bacteria

Antibiotic resistance has increased markedly in gram-negative bacteria over the last two decades, and in many cases has been associated with increased mortality and healthcare costs. The adoption of genotyping and next generation whole genome sequencing of large sets of clinical bacterial isolates has greatly expanded our understanding of how antibiotic resistance develops and transmits among bacteria and between patients. Diverse mechanisms of resistance, including antibiotic degradation, antibiotic target modification, and modulation of permeability through the bacterial membrane have been demonstrated. These fundamental insights into the mechanisms of gram-negative antibiotic resistance have influenced the development of novel antibiotics and treatment practices in highly resistant infections. Here, we review the mechanisms and global epidemiology of antibiotic resistance in some of the most clinically important resistance phenotypes, including carbapenem resistant Enterobacteriaceae, extensively drug resistant (XDR) Pseudomonas aeruginosa, and XDR Acinetobacter baumannii. Understanding the resistance mechanisms and epidemiology of these pathogens is critical for the development of novel antibacterials and for individual treatment decisions, which often involve alternatives to β-lactam antibiotics.

Extended Spectrum Beta-Lactamase-Producing Gram-Negative Bacteria Recovered From an Amazonian Lake Near the City of Belém, Brazil

Aquatic systems have been described as antibiotic resistance reservoirs, where water may act as a vehicle for the spread of resistant bacteria and resistance genes. We evaluated the occurrence and diversity of third generation cephalosporin-resistant gram-negative bacteria in a lake in the Amazonia region. This water is used for human activities, including consumption after appropriate treatment. Eighteen samples were obtained from six sites in October 2014. Water quality parameters were generally within the legislation limits. Thirty-three bacterial isolates were identified as Escherichia (n = 7 isolates), Acinetobacter, Enterobacter, and Klebsiella (n = 5 each), Pseudomonas (n = 4), Shigella (n = 3), and Chromobacterium, Citrobacter, Leclercia, Phytobacter (1 isolate each). Twenty nine out of 33 isolates (88%) were resistant to most beta-lactams, except carbapenems, and 88% (n = 29) were resistant to antibiotics included in at least three different classes. Among the beta-lactamase genes inspected, the bla_CTX–M was the most prevalent (n = 12 positive isolates), followed by bla_TEM (n = 5) and bla_SHV (n = 4). bla_CTX–M–15 (n = 5), bla_CTX–M–14 (n = 1) and bla_CTX–M–2 (n = 1) variants were detected in conserved genomic contexts: bla_CTX–M–15 flanked by ISEcp1 and Orf477; bla_CTX–M–14 flanked by ISEcp1 and IS903; and bla_CTX–M–2 associated to an ISCR element. For 4 strains the transfer of bla_CTX–M was confirmed by conjugation assays. Compared with the recipient, the transconjugants showed more than 500-fold increases in the MICs of cefotaxime and 16 to 32-fold increases in the MICs of ceftazidime. Two isolates (Escherichia coli APC43A and Acinetobacter baumannii APC25) were selected for whole genome analysis. APC43A was predicted as a E. coli pathogen of the high-risk clone ST471 and serotype O154:H18. bla_CTX–M–15 as well as determinants related to efflux of antibiotics, were noted in APC43A genome. A. baumannii APC25 was susceptible to carbapenems and antibiotic resistance genes detected in its genome were intrinsic determinants (e.g., bla_OXA–208 and bla_ADC–like). The strain was not predicted as a human pathogen and belongs to a new sequence type. Operons related to metal resistance were predicted in both genomes as well as pathogenicity and resistance islands. Results suggest a high dissemination of ESBL-producing bacteria in Lake Água Preta which, although not presenting characteristics of a strongly impacted environment, contains multi-drug resistant pathogenic strains.

Occurrence of blaNDM Variants Among Enterobacteriaceae From a Neonatal Intensive Care Unit in a Northern India Hospital

Carbapenem-resistance among enterobacteriaceae has become a global health concern. The objective of this study was to understand NDM producing enterobacteriaceae and their genetic basis of resistance, spreading in neonatal intensive care unit. Carbapenem resistant NDM producing enterobacteriaceae isolates were recovered from rectal swab and blood sample of infants admitted in NICU. These were determined by using Carba-NP test. All isolates were identified using BD Phoenix^TM−100 and MICs were determined by broth microdilution method. The bla_NDM and associated resistant markers were checked by PCR followed by sequencing. Moreover, ERIC-PCR and genetic environment of bla_NDM gene were also performed for the analysis of clonal relationship and genetic surrounding of the strains. We characterized 44 isolates with bla_NDM variants in Escherichia coli (45.5%), Klebsiella pneumoniae (40.9%), Citrobacter freundii (4.5%), Citrobacter braakii (2.3%), Klebsiella oxytoca (2.3%), Enterobacter cloacae (2.3%), Enterobacter aerogenes (2.2%) from NICU, showing resistance against all antibiotics except colistin and polymixin B. ISAba125 and bleomycin gene were found surrounding all bla_NDM variants, besides class I integron on plasmid. (ERIC)-PCR data revealed non-clonal relatedness among most of the isolates. The transfer of resistant markers was confirmed by conjugation experiment. The PCR-based replicon typing was carried out using DNA of transconjugants. These isolates carried NDM-1 (20.45%), NDM-4 (36.36%), NDM-5 (38.64%), NDM-7 (4.55%), along with OXA, CMY, and SHV variants on conjugative plasmid of IncFIA, IncFIC, IncF, IncK, IncFIB, IncB/O, IncHI1, IncP, IncY, IncFIIA, IncI1, and IncN types. An increased number of carbapenem-resistant NDM producing enterobacteriaceae isolates recovered from NICU which is alarming signal for health workers and policy makers. Hence, it is utmost important to think about infection control measures.

Structure, Genetics and Worldwide Spread of New Delhi Metallo-β-lactamase (NDM): a threat to public health

Background

The emergence of carbapenemase producing bacteria, especially New Delhi metallo-β-lactamase (NDM-1) and its variants, worldwide, has raised amajor public health concern. NDM-1 hydrolyzes a wide range of β-lactam antibiotics, including carbapenems, which are the last resort of antibiotics for the treatment of infections caused by resistant strain of bacteria.

Main body

In this review, we have discussed bla_NDM-1variants, its genetic analysis including type of specific mutation, origin of country and spread among several type of bacterial species. Wide members of enterobacteriaceae, most commonly Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and gram-negative non-fermenters Pseudomonas spp. and Acinetobacter baumannii were found to carry these markers. Moreover, at least seventeen variants of bla_NDM-type gene differing into one or two residues of amino acids at distinct positions have been reported so far among different species of bacteria from different countries. The genetic and structural studies of these variants are important to understand the mechanism of antibiotic hydrolysis as well as to design new molecules with inhibitory activity against antibiotics.

Conclusion

This review provides a comprehensive view of structural differences among NDM-1 variants, which are a driving force behind their spread across the globe.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1012-8) contains supplementary material, which is available to authorized users.