Genetic acquisition of NDM gene offers sustainability among clinical isolates of Pseudomonas aeruginosa in clinical settings

Neonatal sepsis due to NDM-1 and VIM-2 co-producing Pseudomonas aeruginosa in Morocco

BACKGROUND

Carbapenem-resistant Pseudomonas aeruginosa are being increasingly described worldwide. Here, we investigated the molecular mechanisms underlying carbapenem resistance in an extremely drug-resistant P. aeruginosa isolate from a neonatal intensive care unit in Morocco.

MATERIALS AND METHODS

P. aeruginosa strain O82J1 was identified using MALDI-TOF-MS. Carba NP, immunochromatographic assay NG Carba5 and antimicrobial susceptibility testing using disc diffusion and microbroth were performed. Whole-genome sequencing using the Illumina and MinION technologies and different software packages available at the Center of Genomic Epidemiology were used to predict the resistome, sequence type and plasmid types.

RESULTS

P. aeruginosa O82J1 co-expressed two metallo-β-lactamases, blaNDM-1 and blaVIM-2, and was susceptible to colistin and apramycin only. It belonged to ST773 that is frequently reported worldwide as a high-risk P. aeruginosa clone. The blaVIM-2 gene was integron-borne on a IncP-2 465-kb plasmid, whereas the blaNDM-1 gene was chromosomally encoded and embedded in an integrative conjugative element, probably at the origin of its acquisition. A total of 23 antimicrobial resistance genes were detected including a blaPER-1 ESBL gene, and an 16S-rRNA methyltransferase gene rmtB.

CONCLUSIONS

The isolation of XDR P. aeruginosa isolates expressing several carbapenemases in a neonatal intensive care unit is of great concern due to the reduced treatment options, relying only on colistin, but not recommended in neonates, and apramycin, not yet approved for human therapy. Concerns were further elevated due to the resistance to cefiderocol and ATM/AVI, two novel and last-resort antibiotics recommended to treat infections caused by Gram-negative bacteria, particularly XDR P. aeruginosa in adults.

Carbapenem-Resistant Klebsiella pneumoniae in Southwest China: Molecular Characteristics and Risk Factors Caused by KPC and NDM Producers

Background

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection has attracted worldwide concern and became a serious challenge for clinical treatment. The aims of this study were to evaluate the molecular characteristics and risk factors for CRKP infection.

Methods

All the CRKP strains were screened for antimicrobial resistance genes, virulence genes, and integron by polymerase chain reaction (PCR). Plasmid typing was performed by plasmid conjugation assay and PCR-based replicon typing (PBRT). The genetic environments of bla_KPC-2 and bla_NDM-1 were analyzed by using overlapping PCR and molecular typing was performed by multi-locus sequence typing (MLST). Risk factors for CRKP infection were analyzed by logistic regression model.

Results

All the 66 CRKP isolates were multidrug-resistant, but all of them were susceptible to tigecycline and polymyxin B. Among the CRKP isolates, 42 bla_KPC-2-positive strains were identified carrying IncFII plasmids. Meanwhile, 24 bla_NDM-positive strains were found on lncX3 plasmids, including 20 bla_NDM-1 isolates and 4 bla_NDM-5 isolates. Most of CRKP isolates contained several virulence genes and the class I integron (intl1). The genetic environments of bla_KPC-2 and bla_NDM-1 revealed that the conserved regions (tnpA-tnpR-ISkpn8-bla_KPC-2) and (bla_NDM-1-ble_MBL-trpF-tat) were associated with the dissemination of KPC-2 and NDM-1. ST11 was the most common type in this work. Hematological disease, tracheal cannula, and use of β-lactams and β-lactamase inhibitor combination were identified as independent risk factors for CRKP infection.

Conclusion

This study established the resistance pattern, molecular characteristics, clonal relatedness, and risk factors of CRKP infection. The findings of the novel strain that co-harboring bla_NDM-5 and bla_IMP-4, and the novel ST4495 indicated that the brand-new types have spread in Southwest China, emphasizing the prevent and control the further dissemination of CRKP isolates are highly needed.

Comparative Study of CDST & Multiplex PCR to Detect MBL Producing Gram-Negative Bacilli among VAP Patients Admitted in a Public Medical College Hospital of Bangladesh

Background: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units (ICU), which accounts for 25% of all ICU infection. Documenting carbapenem-resistant gram-negative bacilli is very important as these strains may often cause outbreaks in the ICU setting and are responsible for the increased mortality and morbidity or limiting therapeutic options. The classical phenotypic method cannot provide an efficient means of diagnosis of the metallo-β-lactamases (MBLs) producer. Polymerase chain reaction (PCR) assays have lessened the importance of the phenotypic approach by detecting metallo-β-lactamase resistance genes such as New Delhi metallo-β-lactamase (NDM), Imipenemase (IMP), Verona integron-encoded metallo-β-lactamase (VIM), Sao Paulo metallo-β-lactamase (SPM), Germany Imipenemase (GIM). Objective: To compare the results of the Combined Disc Synergy Test (CDST) with that of the multiplex PCR to detect MBL-producing gram-negative bacilli. Materials and Method: A total of 105 endotracheal aspirates (ETA) samples were collected from the ICU of a public school in Bangladesh. This cross-sectional study was carried out in the Department of Microbiology, Chittagong for quantitative culture, CDST test, and multiplex PCR for bla_IMP, bla_VIM, bla_NDM genes of MBL producers. Results: Among the 105 clinically suspected VAP cases, the quantitative culture was positive in 95 (90%) and among 95 g-negative bacilli isolated from VAP patients, 46 (48.42%) were imipenem resistant, 30 (65.22%) were MBL producers by CDST, 21 (45.65%) were identified as MBL producers by multiplex PCR. Conclusion: PCR was highly sensitive and specific for the detection of MBL producers.

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.

Occurrence of co-existing bla VIM-2 and bla NDM-1 in clinical isolates of Pseudomonas aeruginosa from India

BACKGROUND

bla VIM-2 harboring Pseudomonas aeruginosa has been reported worldwide and considered as the most prevalent metallo-β-lactamase after NDM which are found horizontally transferable and mostly associated with integron gene cassettes. The present study investigates the genetic background, transmission dynamics as well as stability of bla VIM-2 in clinical isolates of P. aeruginosa harbor bla NDM-1 as well which were collected from October 2012 to September 2013.

METHODS

Two P. aeruginosa strains harboring bla VIM-2 along with bla NDM-1 were isolated from Silchar Medical College and Hospital, India. Genetic environment of these resistance determinants was determined and transferability was checked by transformation and conjugation assay which was further confirmed by Southern hybridization. Replicon typing was performed to determine the incompatibility group of the resistant plasmid and their stability was checked by serial passage method. Antimicrobial susceptibility pattern of the isolates was determined and their clonal relatedness was checked by pulsed field gel electrophoresis.

RESULTS

bla VIM-2 was found to be horizontally transferable through an Inc F type plasmid of approximately 30 kb in size. bla VIM-2 was found to be associated with integron gene cassette and was flanked by two different types of cassette arrays. Both the isolates were co-harboring bla NDM-1 which was carried within Inc N type of plasmid with an approximate 24 kb in size and associated with ISAba125 in their upstream region. Reduced susceptibility rate as well as high MIC range was observed in case of wild strains and transformants carrying bla VIM-2 and bla NDM-1.

CONCLUSIONS

The detection of this co-existence of multiple carbapenem resistance genes in this part of world is worrisome and further investigation is required in order to trace the source and to initiate proper treatment option.

Colistin-Nonsusceptible Pseudomonas aeruginosa Sequence Type 654 with blaNDM-1 Arrives in North America

This study describes 3 different blaNDM-1 genetic platforms in 3 different species obtained from the same patient who was directly transferred to an institution in Calgary, Alberta, Canada, following a prolonged hospital stay in India. The blaNDM-1 in the Escherichia coli isolate was located on a 176-kb IncA/C plasmid contained within an ISCR1 region. The blaNDM-1 in the Providencia rettgeri isolate was located on a 117-kb IncT plasmid contained within Tn3000, while the blaNDM-1 in the Pseudomonas aeruginosa isolate was located on the chromosome within an ISCR3 region. This report highlights the plasticity of the genetic regions and environments associated with blaNDM-1. To the best of our knowledge, this is the first report of P. aeruginosa with blaNDM-1 identified in North America and the first report of blaOXA-181 in P. rettgeri. The P. aeruginosa isolate belonged to the international high-risk sequence type 654 clone and was nonsusceptible to colistin. This case emphasizes the need for the use of appropriate infection prevention and control measures and vigilant screening for carbapenem-resistant Gram-negative bacteria in patients with a history of travel to areas of endemicity, such as the Indian subcontinent.