New Delhi metallo 1: have carbapenems met their doom?

Molecular characterization of carbapenem-resistant Enterobacterales in thirteen tertiary care hospitals in Saudi Arabia

BACKGROUND

Carbapenems are the antibiotics of last-resort for the treatment of bacterial infections caused by multidrug-resistant organisms. The emergence of resistance is a critical and worrisome problem for clinicians and patients. Carbapenem-resistant Enterobacterales (CRE) are spreading globally, are associated with an increased frequency of reported outbreaks in many regions, and are becoming endemic in many others.

OBJECTIVES

Determine the molecular epidemiology of CRE isolates from various regions of Saudi Arabia to identify the genes encoding resistance and their clones for a better understanding of the epidemio-logical origin and national spread.

DESIGN

Multicenter, cross-sectional, laboratory-based study.

SETTING

Samples were collected from 13 Ministry of Health tertiary-care hospitals from five different regions of Saudi Arabia.

METHODS

Isolates were tested using the GeneXpert molecular platform to classify CRE.

MAIN OUTCOME MEASURES

Prevalence of various types of CRE in Saudi Arabia.

SAMPLE SIZE

519 carbapenem-resistant isolates.

RESULT

Of 519 isolates, 440 (84.7%) were positive for CRE, with Klebsiella pneumoniae (410/456, 90%) being the most commonly isolated pathogen. The distribution of the CRE-positive K pneumoniae resistance genes was as follows: OXA-48 (n=292, 71.2%), NDM-1 (n=85, 20.7%), and NDM+OXA-48 (n=33, 8%). The highest percentage of a single blaOXA-48 gene was detected in the central and eastern regions (77%), while the blaNDM-gene was the predominant type in the northern region (27%). The southern regions showed the lowest percentages for harboring both blaOXA-48 and blaNDM genes (4%), while the western region isolates showed the highest percentage of harboring both genes (14%).

CONCLUSION

The results illustrate the importance of molecular characterization of CRE isolates for patient care and infection prevention and control. Larger multicenter studies are needed to critically evaluate the risk factors and trends over time to understand the dynamics of spread and effective methods of control.

LIMITATIONS

Lack of phenotypic susceptibility and clinical data.

CONFLICT OF INTEREST

None.

Highly multidrug-resistant Morganella morganii clinical isolates from Nepal co-producing NDM-type metallo-β-lactamases and the 16S rRNA methylase ArmA

Morganella morganii can harbour extended-spectrum β-lactamases and carbapenemases, resulting in increased resistance to multiple antibiotics and a high mortality rate. This study describes the emergence of highly multidrug-resistant clinical isolates of M. morganii from Nepal co-producing NDM-type metallo-β-lactamases, including NDM-1 and NDM-5, and the 16S rRNA methylase ArmA. This is the first report of M. morganii clinical isolates from Nepal co-producing NDM-1/-5 and ArmA. It is important to establish infection control systems and effective treatments against multidrug-resistant M. morganii.

The Epidemiology of Carbapenem-Resistant Enterobacteriaceae: The Impact and Evolution of a Global Menace

Carbapenem-resistant Enterobacteriaceae (CRE) are a serious public health threat. Infections due to these organisms are associated with significant morbidity and mortality. Mechanisms of drug resistance in gram-negative bacteria (GNB) are numerous; β-lactamase genes carried on mobile genetic elements are a key mechanism for the rapid spread of antibiotic-resistant GNB worldwide. Transmissible carbapenem-resistance in Enterobacteriaceae has been recognized for the last 2 decades, but global dissemination of carbapenemase-producing Enterobacteriaceae (CPE) is a more recent problem that, once initiated, has been occurring at an alarming pace. In this article, we discuss the evolution of CRE, with a focus on the epidemiology of the CPE pandemic; review risk factors for colonization and infection with the most common transmissible CPE worldwide, Klebsiella pneumoniae carbapenemase-producing K. pneumoniae; and present strategies used to halt the striking spread of these deadly pathogens.

What tuberculosis can teach us about combating multidrug-resistant Gram negative bacilli

There are striking similarities between the dual pandemics of multidrug-resistant tuberculosis (MDR TB) and multidrug-resistant Gram negative bacilli (MDR GNB) despite fundamental differences in the pathogenesis and epidemiology of these pathogens. In this perspective, we highlight several strategies that have been used by the global TB community to address the MDR TB problem, including approaches to: encourage appropriate use of anti-TB medications, enhance appropriate utilization of molecular diagnostic testing, facilitate development of new antimicrobial agents, and strengthen surveillance systems and infection control practices. Understanding the successes and challenges of these strategies for MDR TB control will be instructive for efforts to curb emergence and spread of MDR GNB.

Distribution and Relationships of Antimicrobial Resistance Determinants among Extended-Spectrum-Cephalosporin-Resistant or Carbapenem-Resistant Escherichia coli Isolates from Rivers and Sewage Treatment Plants in India

To determine the distribution and relationship of antimicrobial resistance determinants among extended-spectrum-cephalosporin (ESC)-resistant or carbapenem-resistant Escherichia coli isolates from the aquatic environment in India, water samples were collected from rivers or sewage treatment plants in five Indian states. A total of 446 E. coli isolates were randomly obtained. Resistance to ESC and/or carbapenem was observed in 169 (37.9%) E. coli isolates, which were further analyzed. These isolates showed resistance to numerous antimicrobials; more than half of the isolates exhibited resistance to eight or more antimicrobials. The blaNDM gene was detected in 14/21 carbapenem-resistant E. coli isolates: blaNDM-1 in 2 isolates, blaNDM-5 in 7 isolates, and blaNDM-7 in 5 isolates. The blaCTX-M gene was detected in 112 isolates (66.3%): blaCTX-M-15 in 108 isolates and blaCTX-M-55 in 4 isolates. We extracted 49 plasmids from selected isolates, and their whole-genome sequences were determined. Fifty resistance genes were detected, and 11 different combinations of replicon types were observed among the 49 plasmids. The network analysis results suggested that the plasmids sharing replicon types tended to form a community, which is based on the predicted gene similarity among the plasmids. Four communities each containing from 4 to 17 plasmids were observed. Three of the four communities contained plasmids detected in different Indian states, suggesting that the interstate dissemination of ancestor plasmids has already occurred. Comparison of the DNA sequences of the blaNDM-positive plasmids detected in this study with known sequences of related plasmids suggested that various mutation events facilitated the evolution of the plasmids and that plasmids with similar genetic backgrounds have widely disseminated in India.

New Delhi Metallo-beta-lactamase around the world: An eReview using Google Maps

Gram-negative carbapenem-resistant bacteria, in particular those producing New Delhi Metallo-beta-lactamase-1 (NDM-1), are a major global health problem. To inform the scientific and medical community in real time about worldwide dissemination of isolates of NDM-1-producing bacteria, we used the PubMed database to review all available publications from the first description in 2009 up to 31 December 2012, and created a regularly updated worldwide dissemination map using a web-based mapping application. We retrieved 33 reviews, and 136 case reports describing 950 isolates of NDM-1-producing bacteria. Klebsiella pneumoniae (n= 359) and Escherichia coli (n=268) were the most commonly reported bacteria producing NDM-1 enzyme. Several case reports of infections due to imported NDM-1 producing bacteria have been reported in a number of countries, including the United Kingdom, Italy, and Oman. In most cases (132/153, 86.3%), patients had connections with the Indian subcontinent or Balkan countries. Those infected were originally from these areas, had either spent time and/or been hospitalised there, or were potentially linked to other patients who had been hospitalised in these regions. By using Google Maps, we were able to trace spread of NDM-1-producing bacteria. We strongly encourage epidemiologists to use these types of interactive tools for surveillance purposes and use the information to prevent the spread and outbreaks of such bacteria.

Worldwide dissemination of the NDM-type carbapenemases in Gram-negative bacteria

The emergence of one of the most recently described carbapenemases, namely, the New Delhi metallo-lactamase (NDM-1), constitutes a critical and growingly important medical issue. This resistance trait compromises the efficacy of almost all lactams (except aztreonam), including the last resort carbapenems. Therapeutical options may remain limited mostly to colistin, tigecycline, and fosfomycin. The main known reservoir of NDM producers is the Indian subcontinent whereas a secondary reservoir seems to have established the Balkans regions and the Middle East. Although the spread of bla NDM-like genes (several variants) is derived mostly by conjugative plasmids in Enterobacteriaceae, this carbapenemase has also been identified in P. aeruginosa and Acinetobacter spp. Acinetobacter sp. may play a pivotal role for spreading bla NDM genes for its natural reservoir to Enterobacteriaceae. Rapid diagnostic techniques (Carba NP test) and screening of carriers are the cornerstone to try to contain this outbreak which threatens the efficacy of the modern medicine.

The global spread of healthcare-associated multidrug-resistant bacteria: a perspective from Asia

Since antibiotics were first used, each new introduced class has been followed by a global wave of emergent resistance, largely originating in Europe and North America where they were first used. Methicillin-resistant Staphylococcus aureus spread from the United Kingdom and North America across Europe and then Asia over more than a decade. Vancomycin-resistant enterococci and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae followed a similar path some 20 years later. Recently however, metallo-β-lactamases have originated in Asia. New Delhi metallo-β-lactamase-1 was found in almost every continent within a year of its emergence in India. Metallo-β-lactamase enzymes are encoded on highly transmissible plasmids that spread rapidly between bacteria, rather than relying on clonal proliferation. Global air travel may have helped facilitate rapid dissemination. As the antibiotic pipeline offers little in the short term, our most important tools against the spread of antibiotic resistant organisms are intensified infection control, surveillance, and antimicrobial stewardship.

Current epidemiology and growing resistance of gram-negative pathogens

In the 1980s, gram-negative pathogens appeared to have been beaten by oxyimino-cephalosporins, carbapenems, and fluoroquinolones. Yet these pathogens have fought back, aided by their membrane organization, which promotes the exclusion and efflux of antibiotics, and by a remarkable propensity to recruit, transfer, and modify the expression of resistance genes, including those for extended-spectrum β-lactamases (ESBLs), carbapenemases, aminoglycoside-blocking 16S rRNA methylases, and even a quinolone-modifying variant of an aminoglycoside-modifying enzyme. Gram-negative isolates--both fermenters and non-fermenters--susceptible only to colistin and, more variably, fosfomycin and tigecycline, are encountered with increasing frequency, including in Korea. Some ESBLs and carbapenemases have become associated with strains that have great epidemic potential, spreading across countries and continents; examples include Escherichia coli sequence type (ST)131 with CTX-M-15 ESBL and Klebsiella pneumoniae ST258 with KPC carbapenemases. Both of these high-risk lineages have reached Korea. In other cases, notably New Delhi Metallo carbapenemase, the relevant gene is carried by promiscuous plasmids that readily transfer among strains and species. Unless antibiotic stewardship is reinforced, microbiological diagnosis accelerated, and antibiotic development reinvigorated, there is a real prospect that the antibiotic revolution of the 20th century will crumble.

Fourteen years in resistance

Resistance trends have changed greatly over the 14 years (1997-2011) whilst I was Director of the UK Antibiotic Resistance Monitoring and Reference Laboratory (ARMRL). Meticillin-resistant Staphylococcus aureus (MRSA) first rose, then fell with improved infection control, although with the decline of one major clone beginning before these improvements. Resistant pneumococci too have declined following conjugate vaccine deployment. If the situation against Gram-positive pathogens has improved, that against Gram-negatives has worsened, with the spread of (i) quinolone- and cephalosporin-resistant Enterobacteriaceae, (ii) Acinetobacter with OXA carbapenemases, (iii) Enterobacteriaceae with biochemically diverse carbapenemases and (iv) gonococci resistant to fluoroquinolones and, latterly, cefixime. Laboratory, clinical and commercial aspects have also changed. Susceptibility testing is more standardised, with pharmacodynamic breakpoints. Treatments regimens are more driven by guidelines. The industry has fewer big profitable companies and more small companies without sales income. There is good and bad here. The quality of routine susceptibility testing has improved, but its speed has not. Pharmacodynamics adds science, but over-optimism has led to poor dose selection in several trials. Guidelines discourage poor therapy but concentrate selection onto a diminishing range of antibiotics, threatening their utility. Small companies are more nimble, but less resilient. Last, more than anything, the world has changed, with the rise of India and China, which account for 33% of the world's population and increasingly provide sophisticated health care, but also have huge resistance problems. These shifts present huge challenges for the future of chemotherapy and for the edifice of modern medicine that depends upon it.

Is screening patients for antibiotic-resistant bacteria justified in the Indian context?

Infection with multi-antibiotic-resistant bacteria is a common clinical problem in India. In some countries and centres, screening patients to detect colonisation by these organisms is used to determine specific interventions such as decolonisation treatment, prophylactic antibiotics prior to surgical interventions or for selection of empirical antibiotic therapy, and to isolate patients so that transmission of these difficult to treat organisms to other patients could be prevented. In India, there is no national guideline or recommendation for screening patients for multi-drug-resistant (MDR) bacteria such as MRSA (methicillin-resistant Staphylococcus aureus), VRE (vancomycin-resistant enterococcus), ESBL (extended spectrum beta-lactamase) or MBL (metallo-beta-lactamase) producers. The present article discusses the relevance of screening patients for multi-antibiotic-resistant bacteria in the Indian context. Literature has been reviewed about antibiotic resistance in India, screening methodology, economic debate about screening. The percentages of strains from various hospitals in India which were reported to be MRSA was between 8 and 71%, those for ESBL between 19 and 60% and carbapenem-resistant Gram-negative bacilli between 5.3 and 59%. There exists culture-based technology for the detection of these resistant organisms from patient samples. For some pathogens, such as MRSA and VRE Polymerase chain reaction-based tests are also becoming available. Screening for MDR bacteria is an option which may be used after appraisal of the resources available, and after exploring possibility of implementing the interventions that may be required after a positive screening test result.

The emerging NDM carbapenemases

Carbapenems were the last β-lactams retaining near-universal anti-Gram-negative activity, but carbapenemases are spreading, conferring resistance. New Delhi metallo-β-lactamase (NDM) enzymes are the latest carbapenemases to be recognized and since 2008 have been reported worldwide, mostly in bacteria from patients epidemiologically linked to the Indian subcontinent, where they occur widely in hospital and community infections, and also in contaminated urban water. The main type is NDM-1, but minor variants occur. NDM enzymes are present largely in Enterobacteriaceae, but also in non-fermenters and Vibrionaceae. Dissemination predominantly involves transfer of the blaNDM-1 gene among promiscuous plasmids and clonal outbreaks. Bacteria with NDM-1 are typically resistant to nearly all antibiotics, and reliable detection and surveillance are crucial.

Dissemination of NDM-1 positive bacteria in the New Delhi environment and its implications for human health: an environmental point prevalence study

BACKGROUND

Not all patients infected with NDM-1-positive bacteria have a history of hospital admission in India, and extended-spectrum β-lactamases are known to be circulating in the Indian community. We therefore measured the prevalence of the NDM-1 gene in drinking water and seepage samples in New Delhi.

METHODS

Swabs absorbing about 100 μL of seepage water (ie, water pools in streets or rivulets) and 15 mL samples of public tap water were collected from sites within a 12 km radius of central New Delhi, with each site photographed and documented. Samples were transported to the UK and tested for the presence of the NDM-1 gene, bla(NDM-1), by PCR and DNA probing. As a control group, 100 μL sewage effluent samples were taken from the Cardiff Wastewater Treatment Works, Tremorfa, Wales. Bacteria from all samples were recovered and examined for bla(NDM-1) by PCR and sequencing. We identified NDM-1-positive isolates, undertook susceptibility testing, and, where appropriate, typed the isolates. We undertook Inc typing on bla(NDM-1)-positive plasmids. Transconjugants were created to assess plasmid transfer frequency and its relation to temperature.

FINDINGS

From Sept 26 to Oct 10, 2010, 171 seepage samples and 50 tap water samples from New Delhi and 70 sewage effluent samples from Cardiff Wastewater Treatment Works were collected. We detected bla(NDM-1) in two of 50 drinking-water samples and 51 of 171 seepage samples from New Delhi; the gene was not found in any sample from Cardiff. Bacteria with bla(NDM-1) were grown from 12 of 171 seepage samples and two of 50 water samples, and included 11 species in which NDM-1 has not previously been reported, including Shigella boydii and Vibrio cholerae. Carriage by enterobacteria, aeromonads, and V cholera was stable, generally transmissible, and associated with resistance patterns typical for NDM-1; carriage by non-fermenters was unstable in many cases and not associated with typical resistance. 20 strains of bacteria were found in the samples, 12 of which carried bla(NDM-1) on plasmids, which ranged in size from 140 to 400 kb. Isolates of Aeromonas caviae and V cholerae carried bla(NDM-1) on chromosomes. Conjugative transfer was more common at 30°C than at 25°C or 37°C.

INTERPRETATION

The presence of NDM-1 β-lactamase-producing bacteria in environmental samples in New Delhi has important implications for people living in the city who are reliant on public water and sanitation facilities. International surveillance of resistance, incorporating environmental sampling as well as examination of clinical isolates, needs to be established as a priority.

FUNDING

European Union.