Laurent Poirel

Emerging broad-spectrum resistance in Pseudomonas aeruginosa and Acinetobacter baumannii: Mechanisms and epidemiology

Multidrug resistance is quite common among non-fermenting Gram-negative rods, in particular among clinically relevant species including Pseudomonas aeruginosa and Acinetobacter baumannii. These bacterial species, which are mainly nosocomial pathogens, possess a diversity of resistance mechanisms that may lead to multidrug or even pandrug resistance. Extended-spectrum β-lactamases (ESBLs) conferring resistance to broad-spectrum cephalosporins, carbapenemases conferring resistance to carbapenems, and 16S rRNA methylases conferring resistance to all clinically relevant aminoglycosides are the most important causes of concern. Concomitant resistance to fluoroquinolones, polymyxins (colistin) and tigecycline may lead to pandrug resistance. The most important mechanisms of resistance in P. aeruginosa and A. baumannii and their most recent dissemination worldwide are detailed here.

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.

Carbapenemase-producing Enterobacteriaceae in Europe: A survey among national experts from 39 countries, February 2013

The spread of carbapenemase-producing Enterobacteriaceae (CPE) is a threat to healthcare delivery, although its extent differs substantially from country to country. In February 2013, national experts from 39 European countries were invited to self-assess the current epidemiological situation of CPE in their country. Information about national management of CPE was also reported. The results highlight the urgent need for a coordinated European effort on early diagnosis, active surveillance, and guidance on infection control measures.

Intercontinental spread of OXA-48 beta-lactamase-producing Enterobacteriaceae over a 11-year period, 2001 to 2011

OXA-48 beta-lactamase producers are emerging as an important threat mostly in the Mediterranean area. We report here the molecular epidemiology of a collection of OXA-48 beta-lactamase-positive enterobacterial isolates (n=107) recovered from European and north-African countries between January 2001 and December 2011. This collection included 67 Klebsiella pneumoniae, 24 Escherichia coli and 10 Enterobacter cloacae. Using the EUCAST breakpoints, ninety-eight isolates (91.6%) were of intermediate susceptibility or resistant to ertapenem, whereas 66% remained susceptible to imipenem. Seventy-five per cent of the isolates co-produced an extended-spectrum beta-lactamase, most frequently CTX-M-15 (77.5%). Susceptibility testing to non-beta-lactam antibiotics showed that colistin, tigecycline, amikacin, and fosfomycin remain active against most of the isolates. Multilocus sequence typing indicated that the most common sequence types (ST) were ST101 and ST38 for K. pneumoniae and E. coli, respectively. The bla(OXA-48) gene was located on a 62 kb IncL/M plasmid in 92.5% of the isolates, indicating that a single plasmid was mainly responsible for the spread of that gene. In addition, this study identified multiple cases of importation of OXA-48 beta-lactamase producers at least in Europe, and spread of OXA-48 beta-lactamase producers giving rise to an endemic situation, at least in France.

Polymyxins: Antibacterial Activity, Susceptibility Testing, and Resistance Mechanisms Encoded by Plasmids or Chromosomes

SUMMARY Polymyxins are well-established antibiotics that have recently regained significant interest as a consequence of the increasing incidence of infections due to multidrug-resistant Gram-negative bacteria. Colistin and polymyxin B are being seriously reconsidered as last-resort antibiotics in many areas where multidrug resistance is observed in clinical medicine. In parallel, the heavy use of polymyxins in veterinary medicine is currently being reconsidered due to increased reports of polymyxin-resistant bacteria. Susceptibility testing is challenging with polymyxins, and currently available techniques are presented here. Genotypic and phenotypic methods that provide relevant information for diagnostic laboratories are presented. This review also presents recent works in relation to recently identified mechanisms of polymyxin resistance, including chromosomally encoded resistance traits as well as the recently identified plasmid-encoded polymyxin resistance determinant MCR-1. Epidemiological features summarizing the current knowledge in that field are presented.

Co-occurrence of extended spectrum β lactamase and MCR-1 encoding genes on plasmids

Findings reported by Yi-Yun Liu and colleagues identified the plasmidborne gene mcr-1 encoding resistance to colistin with a high prevalence in Escherichia coli isolates from animals, foodstuff , and human beings in China. The same gene was then reported in Europe (Denmark) among extendedspectrum β lactamase (ESBL) and AmpC-producing E coli isolates from chicken meat and human infections, but at a very low prevalence. We screened ESBL-positive E coli isolates collected in France for colistin resistance. Isolates were collected between 2005 and mid-2014 from faeces of diarrhoeic veal calves at farms, as part of a survey in the context of the French antimicrobial resistance Resapath surveillance network for animal pathogens. We screened these isolates for colistin resistance using disk diff usion and minimum inhibitory concentration determination by broth microdilution. We analysed plasmids bearing the mcr-1 gene by conjugation, S1-pulsed-fi eld gel electrophoresis, PCRbased replicon typing, and Southern blot. We analysed clonal relationship of all isolates by enterobacterial repetitive intergenic consensus PCR and pulsedfi eld gel electrophoresis. Of 517 ESBL-producing E coli isolates collected, 106 (21%) were mcr-1 positive. Notably, the oldest mcr-1positive E coli isolate had been collected in 2005. The 106 mcr-1-positive E coli isolates originated from diff erent individuals located in 94 widely distant farms, and they were clonally unrelated. Sequencing of the whole mcr-1 gene in 75 mcr-1-positive isolates revealed a 100% identity compared with the original sequence. Co-occurrence of the mcr-1 and ESBL genes was identifi ed in a subset of seven isolates, with mcr-1 and blaCTX-M-1 being found on a large and conjugative IncHI2type plasmid together with genes conferring resistance to sulfonamides and tetracyclines, two antibiotics widely used in veterinary medicine. These findings demonstrate a colocation of the mcr-1 gene along with an ESBL gene on a single plasmid, and additional studies are needed to clarify the diversity of the plasmid backbones spreading these two genes within our collection. Noticeably, the prevalence of the mcr-1 gene among ESBL producers in veal calves was much higher than that found in ESBL-positive E coli isolates in human beings and chicken meat reported in Denmark. This diff erence may refl ect a major spread of the mcr-1 gene in European live animals. We showed that the dissemination of mcr-1, at least in France, had already occurred more than a decade ago, with one E coli isolate collected in 2005 identifi ed as mcr-1 positive. Altogether, available data reveal the occurrence of mcr-1 among diff erent animals and human contexts over time. Worryingly, we show that selection pressure with broadspectrum cephalosporins may select for colistin resistance and vice-versa, further highlighting the likelihood of a pandemic spread of mcr-1. Of note, the substantial use of tetracyclines and sulfonamides in animals might also substantially contribute to the dissemination of mcr-1 plasmids. In a one-health perspective, and considering the renewed importance of colistin in human medicine, our data and those from others underscore the urgent need to limit the spread of mcr-1-positive plasmids by reconsidering the massive use of colistin in veterinary medicine worldwide.

Seagulls and Beaches as Reservoirs for Multidrug-Resistant Escherichia coli

A variety of extended-spectrum β-lactamase–producing Escherichia coli isolates, with a high rate of cefotaximase-15 resistance, were identified in seagull feces from Porto, Portugal, beaches. Beaches may therefore present a risk to public health because of the potential pathogen-spreading capacity of migratory birds.

Plasmid-mediated carbapenem and colistin resistance in a clinical isolate of Escherichia coli

Performance standards for antimicrobial susceptibility testing. CLSI M100-S25. Wayne, PA: Clinical and Laboratory Standards Institute, 2015. 3 Poirel L, Savov E, Nazli A, et al. Outbreak caused by NDM-1and RmtB-producing Escherichia coli in Bulgaria. Antimicrob Agents Chemother 2014; 58: 2472–74. 4 Tartof SY, Solberg OD, Manges AR, et al. Analysis of a uropathogenic Escherichia coli clonal group by multilocus sequence typing. J Clin Microbiol 2005; 43: 5860–44. Plasmid-mediated carbapenem and colistin resistance in a clinical isolate of Escherichia coli

Occurrence of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in the European survey of carbapenemase-producing Enterobacteriaceae (EuSCAPE): a prospective, multinational study

BACKGROUND Gaps in the diagnostic capacity and heterogeneity of national surveillance and reporting standards in Europe make it difficult to contain carbapenemase-producing Enterobacteriaceae. We report the development of a consistent sampling framework and the results of the first structured survey on the occurrence of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in European hospitals. METHODS National expert laboratories recruited hospitals with diagnostic capacities, who collected the first ten carbapenem non-susceptible clinical isolates of K pneumoniae or E coli and ten susceptible same-species comparator isolates and pertinent patient and hospital information. Isolates and data were relayed back to national expert laboratories, which made laboratory-substantiated information available for central analysis. FINDINGS Between Nov 1, 2013, and April 30, 2014, 455 sentinel hospitals in 36 countries submitted 2703 clinical isolates (2301 [85%] K pneumoniae and 402 (15%) E coli). 850 (37%) of 2301 K pneumoniae samples and 77 (19%) of 402 E coli samples were carbapenemase (KPC, NDM, OXA-48-like, or VIM) producers. The ratio of K pneumoniae to E coli was 11:1. 1·3 patients per 10 000 hospital admissions had positive clinical specimens. Prevalence differed greatly, with the highest rates in Mediterranean and Balkan countries. Carbapenemase-producing K pneumoniae isolates showed high resistance to last-line antibiotics. INTERPRETATION This initiative shows an encouraging commitment by all participants, and suggests that challenges in the establishment of a continent-wide enhanced sentinel surveillance for carbapenemase-producing Enterobacteriaeceae can be overcome. Strengthening infection control efforts in hospitals is crucial for controlling spread through local and national health care networks. FUNDING European Centre for Disease Prevention and Control.

Impact of the isolation medium for detection of carbapenemase-producing Enterobacteriaceae using an updated version of the Carba NP test.

Carbapenem resistance in Enterobacteriaceae is now emerging worldwide at an alarming rate, causing both nosocomial and now communityacquired infections (Nordmann et al., 2012a). A variety of carbapenemases have been reported in Enterobacteriaceae such as KPC (Ambler class A), metallo-blactamases of VIM-, IMPand NDM-type (Ambler class B), and OXA-48-types (Ambler class D). Thus, an efficient strategy for detection of carbapenemase producers is becoming critical for the determination of appropriate therapeutic schemes and the implementation of infection control measures (Nordmann & Poirel, 2013). Recently, the Carba NP test has been developed for rapid identification of carbapenemase production in Enterobacteriaceae (Nordmann et al., 2012b). Here, we further improve and evaluate the ability of the Carba NP test to detect carbapenemase producers among Enterobacteriaceae recovered from various commercial media (selective, non-selective and screening media) used in clinical situations.