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

Enterobacteriaceae isolates carrying the New Delhi metallo-β-lactamase gene in Yemen

Ten carbapenem-resistant Enterobacteriaceae (eight Klebsiella pneumoniae isolates and two Enterobacter cloacae) isolates from Yemen were investigated using in vitro antimicrobial susceptibility testing, phenotypic carbapenemase detection, multilocus sequence typing (MLST) and replicon typing. Carbapenemase, extended-spectrum β-lactamase (ESBL) and plasmid-mediated quinolone resistance determinant genes were identified using PCR and sequencing. All of the 10 carbapenem-resistant Enterobacteriaceae were resistant to β-lactams, tobramycin, ciprofloxacin and cotrimoxazole. Imipenem, doripenem and meropenem MICs ranged from 2 to >32 mg l(-1) and ertapenem MICs ranged from 6 to >32 mg l(-1). All of the K. pneumoniae isolates showed ESBL activity in phenotypic tests. Genes encoding blaNDM were detected in all strains. All K. pneumoniae strains produced CTX-M-15 ESBL and SHV β-lactamases. TEM-1 β-lactamase was detected in seven isolates. Nine isolates were qnr positive including QnrB1, QnrA1 and QnrS1, and six isolates produced AAC-6'-Ib-cr. MLST identified five different sequence types (STs): ST1399, ST147, ST29, ST405 and ST340. Replicon typing showed the presence of IncFII1K plasmids in four transformants. To the best of our knowledge, this is the first report of NDM-1-producing Enterobacteriaceae isolates in Yemen.

Cluster of Escherichia coli isolates producing a plasmid-mediated OXA-48 β-lactamase in a Spanish hospital in 2012

Three unrelated sequence type 131 (ST131), ST58, and ST83 Escherichia coli isolates with low-level resistance to imipenem and resistance to ertapenem were recovered in a Spanish hospital from July to October 2012. They were positive for blaOXA-48 carried by an IncL/M conjugative plasmid, which may have been acquired from Klebsiella pneumoniae.

IS1R-mediated plasticity of IncL/M plasmids leads to the insertion of bla OXA-48 into the Escherichia coli Chromosome

The OXA-48 carbapenemase is mainly encoded by ∼ 62-kb IncL/M plasmids. However, chromosome-mediated genes have been observed in Escherichia coli isolates. In this work, we investigated the genetic environment of OXA-48 in members of the family Enterobacteriaceae (n = 22) to understand how the OXA-48-encoding gene is transferred into the E. coli chromosome. The OXA-48-encoding gene was located within intact Tn1999.2 transposons in the ∼ 62-kb plasmids or within a truncated variant of Tn1999.2 for the OXA-48-encoding genes located in the chromosomes of E. coli bacteria. The analysis of the Tn1999.2 genetic environment revealed an inverted orientation of the transposon in five ∼ 62-kb plasmids (5/14 [35%]) and in all chromosome inserts (n = 8). The sequencing of pRA35 plasmid showed that this orientation of Tn1999.2 and the acquisition of an IS1R insertion sequence generated a 21.9-kb IS1R-based composite transposon encoding OXA-48 and designated Tn6237. The sequencing of a chromosomal insert encoding OXA-48 also revealed this new transposon in the E. coli chromosome. PCR mapping showed the presence of this element in all strains harboring an OXA-48-encoding chromosomal insert. However, different insertion sites of this transposon were observed in the E. coli chromosome. Overall, these findings indicate a plasticity of the OXA-48 genetic environment mediated by IS1R insertion sequences. The insertion sequences can induce the transfer of the OXA-encoding gene into E. coli chromosomes and thereby promote its persistence and expression at low levels.

First report of OXA-48-producing Klebsiella pneumoniae strains in Iran

Carbapenem-resistant Enterobacteriaceae are increasingly reported worldwide and cause therapeutic problem in health care facilities. In this study 28 imipenem-resistant K. pneumoniae were examined for expression of carbapenemases by phenotypic and genotypic methods. Modified Hodge Test (MHT), CarbaNP test were used for phenotypic detection, and PCR using specific primers for the detection of bla_OXA-48-, bla_KPC-, bla_NDM- and bla_VIM-type carbapenemases with specific primers were performed. MHT and CarbaNP tests were positive for all of imipenem-resistant K. pneumoniae. The bla_OXA-48 gene was detected in 27/28 isolates. One isolate was positive for the presence of the bla_VIM-4 gene. According to our results NP test and MHT have high sensitivity and specificity for detection of those carbapenemases. This study reports the first cases of OXA-48-producing K. pneumoniae in Iran.

Travel-related carbapenemase-producing Gram-negative bacteria in Alberta, Canada: the first 3 years

We describe here the characteristics of Alberta, Canada, patients with infections or colonizations with carbapenemase-producing Gram-negative bacteria during 2010 to 2013 that were linked to recent travel outside Canada. Antimicrobial susceptibility was determined by broth microdilution, and isolates were characterized using PCR, sequencing, and multilocus sequencing typing. A broth mating study was used to assess the transferability of resistance plasmids, which were subsequently characterized. All the patients (n=12) included in our study had contact with a health care system while abroad. Most of the patients presented with urinary tract infections (UTIs) and were admitted to hospitals within weeks after their return to Alberta. Secondary spread occurred in 1 case, resulting in the death of another patient. The carbapenemase-producing bacteria (n=17) consisted of Escherichia coli (sequence type 101 [ST101], ST365, ST405, and ST410) with NDM-1, Klebsiella pneumoniae (ST15, ST16, ST147, ST258, ST340, ST512, and ST972) with NDM-1, OXA-181, KPC-2, and KPC-3, Acinetobacter baumannii with OXA-23, Providencia rettgeri with NDM-1, Enterobacter cloacae with KPC-2, and Citrobacter freundii with NDM-1. The blaNDM-1 gene was associated with various narrow- (i.e., IncF) and broad- (i.e., IncA/C and IncL/M) host-range plasmids with different addiction factors. Our results show that NDM-producing K. pneumoniae, belonging to a variety of sequence types with different plasmid scaffolds, are regularly imported from India into Alberta. Clinical microbiology laboratories should remain vigilant in detecting bacteria with carbapenemases.

Emergence of OXA-162-producing Klebsiella pneumoniae in Hungary

In August 2012, 2 carbapenem-resistant Klebsiella pneumoniae isolates from the University of Szeged were submitted to the National Reference Laboratory at the National Centre for Epidemiology to confirm the carbapenem resistance mechanism. PCR assays and sequencing revealed that the isolates harboured the blaOXA-162 carbapenemase gene, a very recently described variant of OXA-48, and the blaCTX-M-15 extended-spectrum β-lactamase gene. The isolates had indistinguishable PFGE patterns and belonged to sequence type ST15. To the best of our knowledge, this is the first description of OXA-48-like carbapenemase-producing bacteria in Hungary and of an OXA-162-type carbapenemase gene in the K. pneumoniae ST15 clone.

Molecular analysis of OXA-48-carrying conjugative IncL/M-like plasmids in clinical isolates of Klebsiella pneumoniae in Ireland

This study characterized an IncL/M-like plasmid containing a bla(OXA-48)-encoding gene from a clinical isolate of Klebsiella pneumoniae, denoted as E71T. Investigation of this plasmid sequence identified unique regions of interest along with conserved regions detected in eight other clinical carbapenem-resistant isolates. A 63-kb plasmid (pE71T) from K. pneumoniae E71T was sequenced and found to be highly similar to the recently published K. pneumoniae pOXA-48a (JN626286). Two copies of the insertion sequence element IS1R were identified, one of which was located adjacent to the bla(OXA-48)-encoding gene forming part of a composite transposon Tn1999.2 and the second located 16-kb downstream. Plasmid profiling and PCR assays confirmed that the pE71T backbone was conserved among the eight other clinical bla(OXA-48)-positive isolates, and in all cases, the OXA-48 genes were part of the Tn1999.2 composite transposon. This is the first report of a bla(OXA-48) and IS1R arrangement-containing plasmid in Ireland.

OXA-48 carbapenemase-producing Salmonella enterica serovar Kentucky isolate of sequence type 198 in a patient transferred from Libya to Switzerland

Here, we report a case of OXA-48-producing Salmonella enterica serovar Kentucky of sequence type 198 (ST198) from perianal screening cultures of a patient transferred from Libya to Switzerland. The blaOXA-48 gene was carried by Tn1999.2 and located on an ∼60-kb IncL/M plasmid. This Salmonella strain also possessed the blaVEB-8, aac(6)-Ib, tet(A), sul1, and mphA resistance genes and substitutions in GyrA (Ser83Phe and Asp87Asn) and ParC (Ser80Ile). This finding emphasizes that prompt screening strategies are essential to prevent the dissemination of carbapenemase producers imported from countries where they are endemic.

Derepressed transfer properties leading to the efficient spread of the plasmid encoding carbapenemase OXA-48

The current emergence of the carbapenemase OXA-48 among Enterobacteriaceae is related to the spread of a single IncL/M-type plasmid, pOXA-48a. This plasmid harbors the blaOXA-48 gene within a composite transposon, Tn1999, which is inserted into the tir gene, encoding a transfer inhibition protein. We showed that the insertion of Tn1999 into the tir gene was involved in a higher transfer frequency of plasmid pOXA-48a. This may likely be the key factor for the successful dissemination of this plasmid.

High rate of faecal carriage of extended-spectrum β-lactamase and OXA-48 carbapenemase-producing Enterobacteriaceae at a university hospital in Morocco

Carbapenemase-producing Enterobacteriaceae isolates are being increasingly reported, particularly from countries surrounding the Mediterranean area. We aimed to quantify the prevalence of carbapenemase- and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in rectal swabs from hospitalized patients in a University hospital in Morocco, and to compare the performance of three screening media: ChromID ESBL (bioMérieux), Brilliance CRE (OXOID, Thermofisher) and SUPERCARBA (home made). Genetic detection and plasmid analysis were performed by PCR and sequencing. Strain comparison was performed by multi-locus sequence typing and the Diversilab technique (bioMérieux). The prevalence of multidrug-resistant Enterobacteriaceae was high, with 33 ESBL producers (42.85%, mainly CTX-M-15) and 10 OXA-48 producers (13%), corresponding to two major clones of K. pneumoniae (70%) and a clone of Enterobacter cloacae (30%). The three screening media showed the same sensitivity for detection of carbapenemase-producing Enterobacteriaceae, whereas the SUPERCARBA medium was more specific than the two other media. The average faecal carriage of ESBL or carbapenemase-producing Enterobacteriaceae varied from 1 × 10(2) to >1 × 10(8) CFU/g of stools. This study shows a high prevalence of multidrug-resistant Enterobacteriaceae, and particularly of OXA-48 producers. The new carbapenem-containing medium, SUPERCARBA, was as sensitive as Brilliance CRE and ChromID ESBL, and more specific for the detection of Enterobacteriaceae expressing those carbapenemases.

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.

OXA-48 carbapenemase-producing Klebsiella pneumoniae isolated from Libyan patients

Six multidrug-resistant Klebsiella pneumoniae isolates were recovered from injured Libyan combatants. Production of carbapenemase was screened by using commercial combination tablets from Rosco combined with a temocillin disk. Polymerase chain reaction (PCR) and sequencing were used to detect several carbapenemase genes and to characterize their genetic environment. Genetic support was studied by mating-out assays. Plasmid size was identified by the KADO method. PCR and sequencing allowed characterization of plasmid scaffold. Genotyping was performed by pulse-field gel electrophoresis (PFGE) and multilocus sequence typing. PCR was used to check for the presence of nine genes linked to virulence in K. pneumoniae. No carbapenemase was identified by Rosco disks, but all isolates showed high-level temocillin resistance. All of them harbored blaOXA-48 in the transposon Tn1999.2, on a self-conjugative plasmid of about 60 kb, similar to pOXA-48. PFGE revealed three clusters in which isolates were genetically related: The first comprised FM9 and FM10, and the second comprised FM1, FM4, and FM5. FM2 formed a third distinct clone. Sequence types ST101, ST11, and ST147 were identified in keeping with PFGE results. The entB, ycfM, ybtS, and mrkD genes were detected in all isolates, and kfu gene was present in the three ST101 strains. This work confirms the current and successful spread of blaOXA-48 by horizontal dissemination of a single IncL/M plasmid through different genetic backbones with strong epidemic potential. It also highlights the need for rapid and reliable phenotypic detection methods. Attempts to link virulence factors and the production of this carbapenemase deserve further studies.

Epidemiological and microbiological characteristics of an outbreak caused by OXA-48-producing Enterobacteriaceae in a neonatal intensive care unit in Jerusalem, Israel

This study describes the course of an OXA-48-producing Enterobacteriaceae (OPE) outbreak that started in March 2012 in a neonatal intensive care unit (NICU) in Jerusalem, Israel. During the peak of the outbreak (January to August 2012), there were 49 patients who had proven or suspected acquisition of OPE in the NICU, including 16 with invasive infections, out of a total of 156 patients who were hospitalized during that period. Three children hospitalized in the pediatric ICU were identified as carriers of OPE. Three patients with a previous stay in the affected NICU were identified as OPE carriers upon admission to another hospital. The Ministry of Health was notified and then intervened in July 2012. Intervention included cohorting colonized patients, conducting frequent rectal-culture surveillance, and improving the implementation of infection control practices. As a result, the incidence of OPE acquisition declined to 5 cases in the first 4 months, followed by no new cases in the next 3 months. Thirty-one patient-unique isolates were available for analysis: 29 Klebsiella pneumoniae isolates, all belonging to a single clone (sequence type 39 [ST39]), and 2 isolates from Enterobacter cloacae. All isolates possessed the blaOXA-48 and blaCTX-M-14 genes, which are located on the same plasmid. This plasmid, similar to the global blaOXA-48-harboring vector, has now acquired blaCTX-M-14, leading to resistance to all β-lactam agents.

Characterization of a new blaOXA-48-carrying plasmid in Enterobacteriaceae

In this work, we characterized a new, 160-kb, blaOXA-48-harboring IncL/M-type plasmid isolated from a Klebsiella pneumoniae strain from France. Moreover, we report the transfer of a 60-kb OXA-48-encoding plasmid from Klebsiella pneumoniae to other Enterobacteriaceae in two patients.

Extraintestinal pathogenic Escherichia coli: an update on antimicrobial resistance, laboratory diagnosis and treatment

Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections and systemic infections in humans. Extraintestinal pathogenic E. coli (ExPEC) had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly, among ExPEC is the increasing recognition of isolates producing 'newer β-lactamases' that consist of plasmid-mediated AmpC β-lactamases (e.g., CMY), extended-spectrum β-lactamases (e.g., CTX-M) and carbapenemases (e.g., New Delhi metallo-β-lactamase, Klebsiella pneumonaie carbapenemase and OXA-48). This review will highlight recent aspects on antimicrobial resistance in ExPEC, including the laboratory detection of these isolates, and describe some treatment options for infections due to antimicrobial-resistant isolates.

Whole genome sequence analysis of the first Australian OXA-48-producing outbreak-associated Klebsiella pneumoniae isolates: the resistome and in vivo evolution

Whole genome sequencing was used to characterize the resistome of intensive care unit (ICU) outbreak-associated carbapenem-resistant K. pneumoniae isolates. Importantly, and of particular concern, the carbapenem-hydrolyzing β-lactamase gene bla_OXA-48 and the extended-spectrum β-lactamase gene bla_CTX-M-14, were identified on a single broad host-range conjugative plasmid. This represents the first report of bla_OXA-48 in Australia and highlights the importance of resistance gene surveillance, as such plasmids can silently spread amongst enterobacterial populations and have the potential to drastically limit treatment options. Furthermore, the in vivo evolution of these isolates was also examined after 18 months of intra-abdominal carriage in a patient that transited through the ICU during the outbreak period. Reflecting the clonality of K. pneumoniae, only 11 single nucleotide polymorphisms (SNPs) were accumulated during this time-period and many of these were associated with genes involved in tolerance/resistance to antibiotics, metals or organic solvents, and transcriptional regulation. Collectively, these SNPs are likely to be associated with changes in virulence (at least to some extent) that have refined the in vivo colonization capacity of the original outbreak isolate.

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.

"Stormy waters ahead": global emergence of carbapenemases

Carbapenems, once considered the last line of defense against of serious infections with Enterobacteriaceae, are threatened with extinction. The increasing isolation of carbapenem-resistant Gram-negative pathogens is forcing practitioners to rely on uncertain alternatives. As little as 5 years ago, reports of carbapenem resistance in Enterobacteriaceae, common causes of both community and healthcare-associated infections, were sporadic and primarily limited to case reports, tertiary care centers, intensive care units, and outbreak settings. Carbapenem resistance mediated by β-lactamases, or carbapenemases, has become widespread and with the paucity of reliable antimicrobials available or in development, international focus has shifted to early detection and infection control. However, as reports of Klebsiella pneumoniae carbapenemases, New Delhi metallo-β-lactamase-1, and more recently OXA-48 (oxacillinase-48) become more common and with the conveniences of travel, the assumption that infections with highly resistant Gram-negative pathogens are limited to the infirmed and the heavily antibiotic and healthcare exposed are quickly being dispelled. Herein, we provide a status report describing the increasing challenges clinicians are facing and forecast the “stormy waters” ahead.

Chromosome-mediated OXA-48 carbapenemase in highly virulent Escherichia coli

OBJECTIVES

Bacteria multiresistant to antibiotics are widely supposed to be weakly virulent. However, the virulence traits of carbapenem-resistant Enterobacteriaceae have not been investigated. In this work, we investigated the virulence and resistance mechanism of an extraintestinal pathogenic Escherichia coli (ExPEC) strain (LEB15) that exhibited decreased susceptibility to carbapenems.

METHODS

The MICs were determined by a microdilution method. The β-lactamase-encoding gene was identified by PCR and sequencing, and the genetic environment was analysed by PFGE and PCR mapping. The genetic background was investigated by multilocus sequence typing (MLST). Virulence-factor-encoding genes and pathogenic islands (PAIs) were detected by multiplex PCR. Virulence was assessed in a mouse sepsis model.

RESULTS

Strain LEB15 produced a chromosomal OXA-48 carbapenemase. The complete bla(OXA-48)-encoding Tn1999.2 transposon was inserted in the LEB15 chromosome. The strain belonged to an MLST cluster of emerging ExPEC strains (ST-127/ST-22). It had a high pathogenic score and eight PAIs (I536, II536, III536, IV536, VI536, I(CFT073), II(CFT073) and II(J96)) and induced an unusually high lethality in the mouse sepsis model.

CONCLUSIONS

Strain LEB15 combines both an atypical broad accumulation of virulence factors, which confers a strong killer phenotype, and a decrease in susceptibility to carbapenems following the chromosomal acquisition of bla(OXA-48). This association of virulence and carbapenemase in E. coli strains might pose major problems in the future for E. coli infection management.

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.

pEl1573 Carrying blaIMP-4, from Sydney, Australia, is closely related to other IncL/M plasmids

Complete sequencing of pEl1573, a representative IncL/M plasmid carrying bla(IMP-4) from Sydney, Australia, revealed an ∼60-kb backbone almost identical to those of IncL/M plasmids pCTX-M3, from Poland, and pCTX-M360, from China, and less closely related to pNDM-HK, pOXA-48a, and pEL60, suggesting different lineages. The ∼28-kb Tn2-derived multiresistance region in pEl1573 is inserted in the same location as those in pCTX-M3 and pNDM-HK and shares some of the same components but has undergone rearrangements.

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.

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.

OXA-163-producing Klebsiella pneumoniae in Cairo, Egypt, in 2009 and 2010

Two genetically unrelated OXA-163-carrying Klebsiella pneumoniae strains were identified from two infection cases in June 2009 and May 2010 in Cairo, Egypt. OXA-163-producing Enterobacteriaceae had been previously reported in Argentina only. Both patients had no history of travel abroad. The emergence of this newly recognized OXA-48-related β-lactamase able to hydrolyze cephalosporins and carbapenems is especially worrying in a geographic area where OXA-48 is endemic and effective surveillance for antibiotic resistance is largely unaffordable.

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.

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.

Emergence of OXA-48-type carbapenemase-producing Enterobacteriaceae in German hospitals

Nine carbapenem-resistant Enterobacteriaceae isolates collected from eight patients in five German hospitals were investigated. Six isolates produced the OXA-48 carbapenemase, and three isolates produced OXA-162, which is a point mutant form of OXA-48. Both carbapenemase genes were located on IncL/M-type conjugative plasmids. Insertion sequence IS1999 (truncated or not by IS1R) was located upstream of the bla(OXA-48) and bla(OXA-162) genes in all of the isolates. Pulsed-field gel electrophoresis typing indicated the clonal transmission of an OXA-48-producing Klebsiella pneumoniae strain in two hospitals.