Characterization of OXA-181, a carbapenem-hydrolyzing class D beta-lactamase from Klebsiella pneumoniae

War wound treatment complications due to transfer of an IncN plasmid harboring bla(OXA-181) from Morganella morganii to CTX-M-27-producing sequence type 131 Escherichia coli

A 22-year-old male developed a recurrent sacral abscess associated with embedded shrapnel following a blast injury. Cultures grew extended-spectrum β-lactamase (ESBL)-producing, carbapenem-susceptible Escherichia coli. Ertapenem was administered, but the infection recurred after each course of antibiotics. Initial surgical interventions were unsuccessful, and subsequent cultures yielded E. coli and Morganella morganii, both nonsusceptible to carbapenems. The isolates were Carba NP test negative, gave ambiguous results with the modified Hodge test, and amplified the bla(OXA48)-like gene by real-time PCR. All E. coli isolates were sequence type 131 (ST131), carried nine resistance genes (including bla(CTX-M-27)) on an IncF plasmid, and were identical by genome sequencing, except for 150 kb of plasmid DNA in carbapenem-nonsusceptible isolates only. Sixty kilobases of this was shared by M. morganii and represented an IncN plasmid harboring bla(OXA-181). In M. morganii, the gene was flanked by IS3000 and ISKpn19, but in all but one of the E. coli isolates containing bla(OXA-181), a second copy of ISKpn19 had inserted adjacent to IS3000. To the best of our knowledge, this is the first report of bla(OXA-181) in the virulent ST131 clonal group and carried by the promiscuous IncN family of plasmids. The tendency of M. morganii to have high MICs of imipenem, a bla(OXA-181) substrate profile that includes penicillins but not extended-spectrum cephalosporins, and weak carbapenemase activity almost resulted in the presence of bla(OXA-181) being overlooked. We highlight the importance of surveillance for carbapenem resistance in all species, even those with intrinsic resistances, and the value of advanced molecular techniques in detecting subtle genetic changes.

Genetic and biochemical characterization of OXA-405, an OXA-48-type extended-spectrum β-lactamase without significant carbapenemase activity

The epidemiology of carbapenemases worldwide is showing that OXA-48 variants are becoming the predominant carbapenemase type in Enterobacteriaceae in many countries. However, not all OXA-48 variants possess significant activity toward carbapenems (e.g., OXA-163). Two Serratia marcescens isolates with resistance either to carbapenems or to extended-spectrum cephalosporins were successively recovered from the same patient. A genomic comparison using pulsed-field gel electrophoresis and automated Rep-PCR typing identified a 97.8% similarity between the two isolates. Both strains were resistant to penicillins and first-generation cephalosporins. The first isolate was susceptible to expanded-spectrum cephalosporins, was resistant to carbapenems, and had a significant carbapenemase activity (positive Carba NP test) related to the expression of OXA-48. The second isolate was resistant to expanded-spectrum cephalosporins, was susceptible to carbapenems, and did not express a significant imipenemase activity, (negative for the Carba NP test) despite possessing a blaOXA-48-type gene. Sequencing identified a novel OXA-48-type β-lactamase, OXA-405, with a four-amino-acid deletion compared to OXA-48. The blaOXA-405 gene was located on a ca. 46-kb plasmid identical to the prototype IncL/M blaOXA-48-carrying plasmid except for a ca. 16.4-kb deletion in the tra operon, leading to the suppression of self-conjugation properties. Biochemical analysis showed that OXA-405 has clavulanic acid-inhibited activity toward expanded-spectrum activity without significant imipenemase activity. This is the first identification of a successive switch of catalytic activity in OXA-48-like β-lactamases, suggesting their plasticity. Therefore, this report suggests that the first-line screening of carbapenemase producers in Enterobacteriaceae may be based on the biochemical detection of carbapenemase activity in clinical settings.

Heterogeneous hydrolytic features for OXA-48-like β-lactamases

OBJECTIVES

Carbapenem-hydrolysing class D β-lactamases of the OXA-48 type are increasingly reported from Enterobacteriaceae. β-Lactamase OXA-48 hydrolyses penicillins very efficiently, but carbapenems only weakly and spares broad-spectrum cephalosporins. Recently, diverse OXA-48-like β-lactamases have been identified worldwide (OXA-162, OXA-181, OXA-163, OXA-204 and OXA-232). They differ by few amino acid substitutions or by amino acid deletions.

METHODS

blaOXA-48, blaOXA-162, blaOXA-163, blaOXA-181, blaOXA-204 and blaOXA-232 were cloned into the same expression vector and expressed in the same Escherichia coli background. Kinetic studies were performed with enzymes purified by ion-exchange chromatography. Determination of hydrolytic activities was performed by UV spectrophotometry. MICs were determined for all recombinant strains, using as background either the WT E. coli TOP10 strain or a porin-deficient E. coli strain.

RESULTS

Kinetic studies showed that OXA-162 and OXA-204 shared the same hydrolytic properties as OXA-48. On the other hand, OXA-181 possessed a higher ability to hydrolyse carbapenems, while OXA-232 hydrolysed those substrates less efficiently. In contrast to the other OXA-48-like β-lactamases, OXA-163 hydrolysed broad-spectrum cephalosporins very efficiently, but did not possess significant carbapenemase activity. Although several of these OXA-48-like enzymes possess low activity against carbapenems, MICs of carbapenems were significantly elevated when determined for strains possessing permeability defects.

CONCLUSIONS

A detailed comparative analysis of the kinetic properties of the OXA-48-like β-lactamases is provided here. It clarifies the respective features of each OXA-48-like variant and their respective impacts in terms of carbapenem resistance.

Carbapenem-resistant Enterobacteriaceae: biology, epidemiology, and management

Introduced in the 1980s, carbapenem antibiotics have served as the last line of defense against multidrug-resistant Gram-negative organisms. Over the last decade, carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant public health threat. This review summarizes the molecular genetics, natural history, and epidemiology of CRE and discusses approaches to prevention and treatment.

Acquired Class D β-Lactamases

The Class D β-lactamases have emerged as a prominent resistance mechanism against β-lactam antibiotics that previously had efficacy against infections caused by pathogenic bacteria, especially by Acinetobacter baumannii and the Enterobacteriaceae. The phenotypic and structural characteristics of these enzymes correlate to activities that are classified either as a narrow spectrum, an extended spectrum, or a carbapenemase spectrum. We focus on Class D β-lactamases that are carried on plasmids and, thus, present particular clinical concern. Following a historical perspective, the susceptibility and kinetics patterns of the important plasmid-encoded Class D β-lactamases and the mechanisms for mobilization of the chromosomal Class D β-lactamases are discussed.

Molecular epidemiology of OXA-48-producing Klebsiella pneumoniae in France

We characterized 53 OXA-48-producing Klebsiella pneumoniae (OXA-48-Kp) isolated between 2011 and 2013 in 21 French hospitals. All the isolates were genotyped using MLST and PFGE and the population structure of the species was determined by a nucleotide-based analysis of the entire K. pneumoniae MLST database. Most of the OXA-48-Kp isolates also produced CTX-M-15 and remained susceptible to imipenem and meropenem. The isolates were distributed into 20 STs, of which five were dominant (ST15, ST101, ST147, ST395 and ST405). All the OXA-48-Kp clustered in the major clade of K. pneumoniae KpI.

Epidemiology of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii in Mediterranean countries

The emergence and global spread of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii are of great concern to health services worldwide. These β-lactamases hydrolyse almost all β-lactams, are plasmid-encoded, and are easily transferable among bacterial species. They are mostly of the KPC, VIM, IMP, NDM, and OXA-48 types. Their current extensive spread worldwide in Enterobacteriaceae is an important source of concern. Infections caused by these bacteria have limited treatment options and have been associated with high mortality rates. Carbapenemase producers are mainly identified among Klebsiella pneumoniae, Escherichia coli, and A. baumannii and still mostly in hospital settings and rarely in the community. The Mediterranean region is of interest due to a great diversity and population mixing. The prevalence of carbapenemases is particularly high, with this area constituting one of the most important reservoirs. The types of carbapenemase vary among countries, partially depending on the population exchange relationship between the regions and the possible reservoirs of each carbapenemase. This review described the epidemiology of carbapenemases produced by enterobacteria and A. baumannii in this part of the world highlighting the worrisome situation and the need to screen and detect these enzymes to prevent and control their dissemination.

Acquired carbapenemases in Enterobactericeae in Singapore, 1996-2012

AIMS

To characterise carbapenemase-producing Enterobacteriaceae (CRE) isolated in Singapore.

METHODS

Carbapenemase genes and their flanking regions were amplified and sequenced by PCR. Isolates were typed by pulsed-field gel electrophoresis and multi-locus sequence typing. Plasmids bearing carbapenemase genes were sized by S1 nuclease digestion, Southern blotting, and DNA hybridisation with appropriate probes. Transfer of these plasmids was attempted by conjugation and transformation. Successfully transferred plasmids were characterised by polymerase chain reaction (PCR) replicon typing and restriction digestion.

RESULTS

Isolates of Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae and Citrobacter species carried a variety of carbapenemase genes including blaIMP-1, blaIMP-4, blaNDM-1, blaNDM-7, blaOXA-181, blaOXA-48 and blaKPC-2. Apart from K. pneumoniae with blaOXA-181, and some K. pneumoniae with blaNDM-1, the other isolates were not clonal. However there appears to be some spread of plasmids with blaIMP-1, blaNDM-1,blaKPC-2, and blaOXA-48.

CONCLUSIONS

The number of isolates of CRE has increased in Singapore, especially since 2010. There is a diversity of carbapenemase types that reflects the geographical proximity of other countries with CRE.

Rapid molecular characterization of Acinetobacter baumannii clones with rep-PCR and evaluation of carbapenemase genes by new multiplex PCR in Hospital District of Helsinki and Uusimaa

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an increasing problem worldwide. Prevalence of carbapenem resistance in Acinetobacter spp. due to acquired carbapenemase genes is not known in Finland. The purpose of this study was to examine prevalence and clonal spread of multiresistant A. baumannii group species, and their carbapenemase genes. A total of 55 Acinetobacter isolates were evaluated with repetitive PCR (DiversiLab) to analyse clonality of isolates, in conjunction with antimicrobial susceptibility profile for ampicillin/sulbactam, colistin, imipenem, meropenem, rifampicin and tigecycline. In addition, a new real-time PCR assay, detecting most clinically important carbapenemase genes just in two multiplex reactions, was developed. The assay detects genes for KPC, VIM, IMP, GES-1/-10, OXA-48, NDM, GIM-1, SPM-1, IMI/NMC-A, SME, CMY-10, SFC-1, SIM-1, OXA-23-like, OXA-24/40-like, OXA-58 and ISAbaI-OXA-51-like junction, and allows confident detection of isolates harbouring acquired carbapenemase genes. There was a time-dependent, clonal spread of multiresistant A. baumannii strongly correlating with carbapenamase gene profile, at least in this geographically restricted study material. The new carbapenemase screening assay was able to detect all the genes correctly suggesting it might be suitable for epidemiologic screening purposes in clinical laboratories.

β-Lactamase production in key gram-negative pathogen isolates from the Arabian Peninsula

SUMMARY Infections due to Gram-negative bacilli (GNB) are a leading cause of morbidity and mortality worldwide. The extent of antibiotic resistance in GNB in countries of the Gulf Cooperation Council (GCC), namely, Saudi Arabia, United Arab Emirates, Kuwait, Qatar, Oman, and Bahrain, has not been previously reviewed. These countries share a high prevalence of extended-spectrum-β-lactamase (ESBL)- and carbapenemase-producing GNB, most of which are associated with nosocomial infections. Well-known and widespread β-lactamases genes (such as those for CTX-M-15, OXA-48, and NDM-1) have found their way into isolates from the GCC states. However, less common and unique enzymes have also been identified. These include PER-7, GES-11, and PME-1. Several potential risk factors unique to the GCC states may have contributed to the emergence and spread of β-lactamases, including the unnecessary use of antibiotics and the large population of migrant workers, particularly from the Indian subcontinent. It is clear that active surveillance of antimicrobial resistance in the GCC states is urgently needed to address regional interventions that can contain the antimicrobial resistance issue.

Emergence of clinical Klebsiella pneumoniae producing OXA-232 carbapenemase in Singapore

We report the emergence of OXA-232, a newly described OXA-48-like carbapenemase variant, in Southeast Asia. Molecular characterization of eight Klebsiella pneumoniae obtained from local and foreign patients reveals clonality of the isolates. bla_OXA-232 was located on a non-conjugative plasmid of 6141 base pairs (GenBank accession number JX423831.1).

OXA-181 Beta Lactamase is not a Major Mediator of Carbapenem Resistance in Enterobacteriaceae

BACKGROUND

Detection of carbapenem hydrolyzing class D beta lactamase OXA-181, (a variant of OXA-48) in Enterobacteriaceae, is important, to institute appropriate therapy and to initiate preventive measures. This study was done to determine the presence of OXA 48 and its derivative OXA-181 in Enterobacteriaceae of pathogenic significance.

MATERIAL AND METHODS

One hundred and eleven non-repetitive Enterobacteriaceae isolates which were resistant to any of the cephalosporin subclasses III and which exhibited reduced susceptibility to carbapenems were included in the study. Minimum inhibitory concentrations (MICs) to imipenem and meropenem was determined by broth microdilution. Production of carbapenamase was screened by Modified Hodge test (MHT). Polymerase Chain Reaction (PCR) was done to detect the presence of bla OXA-181 and bla OXA-48 .Coexistence of other carbapenemase encoding genes, namely, NDM-1, VIM, IMP and KPC were also looked for, by PCR.

RESULTS

Of all the isolates which were tested, only 2 (1.8%) revealed the presence of OXA-181 and OXA-48. These were Klebsiella pneumoniae and Citrobacter freundii. MICs of imipenem and meropenem for Klebsiella pneumoniae were 128mg/l and 64 mg/l and for Citrobacter freundii, they were 32mg/l and 16mg/l respectively. MHT was positive in both isolates.

CONCLUSION

Production of OXA-48 / OXA-181 is not a major mechanism of carbapenem resistance. PCR is the gold standard for its routine identification in clinical microbiology laboratory.

The emergence of OXA-48- and NDM-1-positive Klebsiella pneumoniae in Riyadh, Saudi Arabia

OBJECTIVES

To investigate the emergence of NDM-, OXA-48-, and VIM-producing Klebsiella pneumoniae in Saudi Arabia.

METHODS

From June to December 2011, we obtained K. pneumoniae isolates with reduced sensitivity to carbapenem identified in Riyadh, Saudi Arabia. Only non-duplicate clinical and surveillance isolates obtained from inpatients were included. PCR amplification was carried out for the detection of extended-spectrum beta-lactamase genes (blaCTX-M, blaTEM, blaSHV) and carbapenemase genes (blaKPC, blaVIM, blaIMP, blaNDM, and blaOXA-48). Susceptibility to imipenem, meropenem, amikacin, gentamicin, trimethoprim-sulfamethoxazole, and colistin was determined.

RESULTS

Of the 60K. pneumoniae isolates studied, 45 were from patients in the intensive care unit. Forty-seven isolates harbored blaOXA-48, 12 were positive for blaNDM, and one for blaVIM. No isolate harbored a combination of these resistance genes. No isolate harbored blaKPC or blaIMP. All 37 blaCTX-M-positive isolates belonged to CTX-M group 1, and 29 were positive for a combination of blaCTX-M and blaOXA-48. blaTEM and blaSHV genes were found in 17 and 39 isolates, respectively. All isolates were imipenem- and meropenem-resistant, with a high rate of co-resistance to the other antibiotics. Three blaOXA-48-positive isolates with colistin resistance were detected.

CONCLUSION

Multidrug-resistant K. pneumoniae isolates harboring blaOXA-48, blaNDM, and colistin resistance are emerging in Saudi Arabia.

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.

Emergence of Klebsiella pneumoniae co-producing NDM-type and OXA-181 carbapenemases

The emergence of carbapenemase-producing Enterobacteriaceae is a rapidly evolving threat worldwide. Here, we report the molecular characterization of two Klebsiella pneumoniae isolates carrying both bla(OXA -181) and bla(NDM -1) or bla(NDM -5) isolated from epidemiologically unrelated patients in Singapore. The bla(OXA -181) genes were found existing in different genetic environments.

Plasmids and the spread of resistance

Plasmids represent one of the most difficult challenge for counteracting the dissemination of antimicrobial resistance. They contribute to the spread of relevant resistance determinants, promoting horizontal gene transfer among unrelated bacteria. Undistinguishable plasmids were identified in unrelated bacterial strains isolated at huge geographically distant area, with no apparent epidemiological links. These plasmids belong to families that are largely prevalent in naturally occurring bacteria, usually carry multiple physically linked genetic determinants, conferring resistance to different classes of antibiotics simultaneously. Plasmids also harbour virulence factors and addiction systems, promoting their stability and maintenance in the bacterial host, in different environmental conditions. The characteristics of the most successful plasmids that were at the origin of the spread of carbapenemase, expanded-spectrum β-lactamase, and plasmid-mediated quinolone resistance genes are discussed in this review.

OXA-181-producing Klebsiella pneumoniae establishing in Singapore

Background

Carbapenemase producing Enterobacteriaceae are becoming a major public health concern globally, however, relatively little is known about the molecular and clinical epidemiology of these organisms in many parts of the world.

Methods

As part of a laboratory surveillance programme, 96 carbapenem non-susceptible Enterobacteriaceae isolates from clinical samples from patients in seven hospitals were referred for investigation for carbapenemases. Using polymerase chain reaction (PCR) to screen for a collection of genes encoding carbapenemases, 33 of 96 (34.5%) isolates were confirmed as carbapenemase producers. NDM-1 producers were the most prevalent at 64% (21/33) whilst OXA-181 was the second most common carbapenemase constituting 24.5% (8/33) of the carbapenemase producing isolates. Seven of these eight OXA-181 positive isolates underwent further characterisation with screening for other transmissible antimicrobial resistance determinants using PCR. Clonal relatedness was explored using Multilocus sequence typing (MLST) and Pulsed Field Gel Electrophoresis (PFGE). Plasmid characterisation was performed including restriction analysis and transfer by conjugation or transformation.

Results

In addition to the OXA-181 gene, all contained other transmissible resistance determinants including extended spectrum β-lactamases, oxacillinases or 16S rRNA methylase genes, but none contained metallo-β-lactamases or serine carbapenemases. All isolates had a multidrug resistant phenotype with two isolates being resistant to every antibiotic tested including colistin. Multilocus sequence typing confirmed five isolates belonged to ST17 and two to ST14, with those belonging to the same sequence type having identical PFGE profiles. The OXA-181 gene was typically carried on large plasmids which were mostly non-conjugative.

Conclusions

OXA-181 carbapenemase appears to be an important and probably under-recognised cause of carbapenem resistance in Enterobacteriaceae in Singapore. Further coordinated research into clinical and molecular epidemiology of carbapenemases is urgently required in Singapore and throughout Asia.

Complete sequence of the IncT-type plasmid pT-OXA-181 carrying the blaOXA-181 carbapenemase gene from Citrobacter freundii

The gene encoding the carbapenemase OXA-181 (an OXA-48 variant) was identified from a Citrobacter freundii isolate coproducing NDM-1. The whole sequence of plasmid pT-OXA-181 bearing the blaOXA-181 gene was determined and revealed a 84-kb mobilizable but non-self-conjugative IncT-type plasmid. It totally differs from the 7.6-kb ColE-type and blaOXA-181-bearing plasmid recently identified in a Klebsiella pneumoniae isolate. However, in both plasmids, insertion sequence ISEcp1 might have played a role in acquisition of the blaOXA-181 gene.

Carbapenemases in Klebsiella pneumoniae and other Enterobacteriaceae: an evolving crisis of global dimensions

SUMMARY

The spread of Enterobacteriaceae, primarily Klebsiella pneumoniae, producing KPC, VIM, IMP, and NDM carbapenemases, is causing an unprecedented public health crisis. Carbapenemase-producing enterobacteria (CPE) infect mainly hospitalized patients but also have been spreading in long-term care facilities. Given their multidrug resistance, therapeutic options are limited and, as discussed here, should be reevaluated and optimized. Based on susceptibility data, colistin and tigecycline are commonly used to treat CPE infections. Nevertheless, a review of the literature revealed high failure rates in cases of monotherapy with these drugs, whilst monotherapy with either a carbapenem or an aminoglycoside appeared to be more effective. Combination therapies not including carbapenems were comparable to aminoglycoside and carbapenem monotherapies. Higher success rates have been achieved with carbapenem-containing combinations. Pharmacodynamic simulations and experimental infections indicate that modification of the current patterns of carbapenem use against CPE warrants further attention. Epidemiological data, though fragmentary in many countries, indicate CPE foci and transmission routes, to some extent, whilst also underlining the lack of international collaborative systems that could react promptly and effectively. Fortunately, there are sound studies showing successful containment of CPE by bundles of measures, among which the most important are active surveillance cultures, separation of carriers, and assignment of dedicated nursing staff.

Genetic and biochemical characterisation of OXA-232, a carbapenem-hydrolysing class D β-lactamase from Enterobacteriaceae

Three enterobacterial isolates (two Klebsiella pneumoniae and one Escherichia coli) were recovered from three patients transferred from India to France in 2011. All three isolates were resistant or of intermediate susceptibility to all β-lactams and of decreased susceptibility to carbapenems. These three isolates expressed a novel carbapenem-hydrolysing β-lactamase, OXA-232, differing from OXA-181 and OXA-48 by one and five amino acid substitutions, respectively. Compared with OXA-181, OXA-232 had a lower ability to hydrolyse carbapenems but conversely possessed higher hydrolytic activities against penicillins. The bla(OXA-232) gene was located on a 6.1-kb ColE-type non-conjugative plasmid.

First clinical cases of OXA-48-producing carbapenem-resistant Klebsiella pneumoniae in the United States: the "menace" arrives in the new world

OXA-48 has emerged as a major carbapenemase associated with the Enterobacteriaceae in Europe, North Africa, and Asia. We report the first two clinical cases of OXA-48-type carbapenemase-producing Enterobacteriaceae in the United States from patients recently hospitalized in Saudi Arabia and India. Each is more carbapenem resistant than nearly all previously reported OXA-48-type-producing Enterobacteriaceae.

Characterization of OXA-204, a carbapenem-hydrolyzing class D β-lactamase from Klebsiella pneumoniae

A Klebsiella pneumoniae clinical isolate recovered in Tunisia showed resistance to all β-lactams and decreased susceptibility to carbapenems. K. pneumoniae 204 expressed the carbapenem-hydrolyzing β-lactamase OXA-204, differing from OXA-48 by two amino acid substitutions (Gln98His and Thr99Arg) (class D β-lactamase [DBL] numbering). OXA-48 and OXA-204 shared similar resistance profiles, hydrolyzing carbapenems but sparing broad-spectrum cephalosporins. The bla(OXA-204) gene was located on a ca. 150-kb IncA/C-type plasmid, which also carried the bla(CMY-4) gene. The bla(OXA-204) gene was associated with an ISEcp1 element, whereas the bla(OXA-48) genes are usually associated with IS1999.

Rapid evolution and spread of carbapenemases among Enterobacteriaceae in Europe

Plasmid-acquired carbapenemases in Enterobacteriaceae, which were first discovered in Europe in the 1990s, are now increasingly being identified at an alarming rate. Although their hydrolysis spectrum may vary, they hydrolyse most β-lactams, including carbapenems. They are mostly of the KPC, VIM, NDM and OXA-48 types. Their prevalence in Europe as reported in 2011 varies significantly from high (Greece and Italy) to low (Nordic countries). The types of carbapenemase vary among countries, partially depending on the cultural/population exchange relationship between the European countries and the possible reservoirs of each carbapenemase. Carbapenemase producers are mainly identified among Klebsiella pneumoniae and Escherichia coli, and still mostly in hospital settings and rarely in the community. Although important nosocomial outbreaks with carbapenemase-producing Enterobacteriaceae have been extensively reported, many new cases are still related to importation from a foreign country. Rapid identification of colonized or infected patients and screening of carriers is possible, and will probably be effective for prevention of a scenario of endemicity, as now reported for extended-spectrum β-lactamase (mainly CTX-M) producers in all European countries.

Identification and screening of carbapenemase-producing Enterobacteriaceae

Carbapenem-hydrolysing β-lactamases are the most powerful β-lactamases, being able to hydrolyse almost all β-lactams. They are mostly of the KPC, VIM, IMP, NDM and OXA-48 types. Their current extensive spread worldwide in Enterobacteriaceae is an important source of concern, as these carbapenemase producers are multidrug-resistant. Detection of infected patients and of carriers are the two main approaches for prevention of their spread. Phenotypic and molecular-based techniques are able to identify these carbapenemase producers, although with variable efficiencies. The detection of carriers still relies mostly on the use of screening culture media.

OXA-48-like carbapenemases: the phantom menace

OXA-48-type carbapenem-hydrolysing class D β-lactamases are increasingly reported in enterobacterial species. To date, six OXA-48-like variants have been identified, with OXA-48 being the most widespread. They differ by a few amino acid substitutions or deletions (one to five amino acids). The enzymes hydrolyse penicillins at a high level and carbapenems at a low level, sparing broad-spectrum cephalosporins, and are not susceptible to β-lactamase inhibitors. When combining permeability defects, OXA-48-like producers may exhibit a high level of resistance to carbapenems. OXA-163 is an exception, hydrolysing broad-spectrum cephalosporins but carbapenems at a very low level, and being susceptible to β-lactamase inhibitors. The bla(OXA-48)-type genes are always plasmid-borne and have been identified in association with insertion sequences involved in their acquisition and expression. The current spread of the bla(OXA-48) gene is mostly linked to the dissemination of a single IncL/M-type self-transferable plasmid of 62 kb that does not carry any additional resistance gene. OXA-48-type carbapenemases have been identified mainly from North African countries, the Middle East, Turkey and India, those areas constituting the most important reservoirs; however, occurrence of OXA-48 producers in European countries is now well documented, with some reported hospital outbreaks. Since many OXA-48-like producers do not exhibit resistance to broad-spectrum cephalosporins, or only decreased susceptibility to carbapenems, their recognition and detection can be challenging. Adequate screening and detection methods are therefore required to prevent and control their dissemination.

Spectrophotometry-based detection of carbapenemase producers among Enterobacteriaceae

Carbapenem-hydrolyzing ß-lactamases are the most powerful ß-lactamases being able to hydrolyse almost all ß-lactams. They are mostly of the KPC, VIM, IMP, NDM, and OXA-48 type. A spectrophotometry technique based on analysis of the imipenem hydrolysis has been developed that differentiated carbapenemase- from noncarbapenemase producers. This inexpensive technique adapted to screening of carbapenemase producers may be implemented in any reference laboratory worldwide.

Carbapenem resistance in Enterobacteriaceae: here is the storm!

The current worldwide emergence of resistance to the powerful antibiotic carbapenem in Enterobacteriaceae constitutes an important growing public health threat. Sporadic outbreaks or endemic situations with enterobacterial isolates not susceptible to carbapenems are now reported not only in hospital settings but also in the community. Acquired class A (KPC), class B (IMP, VIM, NDM), or class D (OXA-48, OXA-181) carbapenemases, are the most important determinants sustaining resistance to carbapenems. The corresponding genes are mostly plasmid-located and associated with various mobile genetic structures (insertion sequences, integrons, transposons), further enhancing their spread. This review summarizes the current knowledge on carbapenem resistance in Enterobacteriaceae, including activity, distribution, clinical impact, and possible novel antibiotic pathways.

Detection of carbapenemase producers in Enterobacteriaceae by use of a novel screening medium

A Drigalski agar-based culture medium containing an ertapenem, cloxacillin, and zinc sulfate (Supercarba medium) was tested for screening carbapenemase-producing members of the family Enterobacteriaceae. OXA-48 (n = 44), NDM (n = 25), VIM or IMP (n = 27), and KPC producers (n = 18) were detected with a low detection limit. Its overall sensitivity (95.6%) was higher than those of the currently available ChromID ESBL (bioMérieux) and CHROMagar KPC (CHROMagar) screening media. The Supercarba medium provides a significant improvement for detection of the most common types of carbapenemase producers.

Broad-spectrum β-lactam antibiotics for treating experimental peritonitis in mice due to Klebsiella pneumoniae producing the carbapenemase OXA-48

A lethal peritonitis model was induced in mice with a Klebsiella pneumoniae isolate producing the carbapenemase OXA-48. Administration of a single dose (up to 100 mg/kg) of the antibiotic piperacillin-tazobactam, imipenem-cilastatin, ertapenem, or cefotaxime had little or no impact on lethality. Ceftazidime had the highest efficacy in vivo, which mirrored its in vitro activity; this was not the case for carbapenems. Therefore, ceftazidime may be recommended for the treatment of infections due to OXA-48 producers if they do not coproduce an extended-spectrum β-lactamase or a plasmid-mediated AmpC cephalosporinase.

NDM-2 carbapenemase-producing Acinetobacter baumannii in the United Arab Emirates

Screening 155 carbapenem non-susceptible Acinetobacter baumannii strains recovered in Abu Dhabi hospitals identified two metallo-ß-lactamase bla(NDM) gene-carrying isolates. They were isolated 4 months apart from the urine of a cancer patient previously treated in Egypt, Lebanon and in the United Arab Emirates. They were clonally related and carried the bla(NDM-2) gene recently identified in A. baumannii in Egypt and Israel. Sequences surrounding the bla(NDM-2) gene showed significant similarities with those associated with bla(NDM-1) in Enterobacteriaceae and A. baumannii. Repeated isolation of bla(NDM-2)-positive A. baumannii in the Middle East raises the possibility of the local emergence and spread of a unique clone.

Genetic features of the widespread plasmid coding for the carbapenemase OXA-48

Complete sequencing of plasmid pOXA-48a carrying the bla(OXA-48) gene from a Klebsiella pneumoniae isolate was performed. Its backbone corresponded to that of an IncL/M-type plasmid, in which the bla(OXA-48) gene had been integrated through the acquisition of the Tn1999 composite transposon without any other antibiotic resistance gene. Molecular epidemiology using a collection of international OXA-48 producers revealed the wide diffusion of pOXA-48a or closely related plasmids.