ISAba825 controls the expression of the chromosomal bla(OXA-51-like) and the plasmid borne bla(OXA-58) gene in clinical isolates of Acinetobacter baumannii isolated from the USA

How Do Transposable Elements Activate Expression of Transcriptionally Silent Antibiotic Resistance Genes?

The rapidly emerging phenomenon of antibiotic resistance threatens to substantially reduce the efficacy of available antibacterial therapies. Dissemination of resistance, even between phylogenetically distant bacterial species, is mediated mainly by mobile genetic elements, considered to be natural vectors of horizontal gene transfer. Transposable elements (TEs) play a major role in this process-due to their highly recombinogenic nature they can mobilize adjacent genes and can introduce them into the pool of mobile DNA. Studies investigating this phenomenon usually focus on the genetic load of transposons and the molecular basis of their mobility. However, genes introduced into evolutionarily distant hosts are not necessarily expressed. As a result, bacterial genomes contain a reservoir of transcriptionally silent genetic information that can be activated by various transposon-related recombination events. The TEs themselves along with processes associated with their transposition can introduce promoters into random genomic locations. Thus, similarly to integrons, they have the potential to convert dormant genes into fully functional antibiotic resistance determinants. In this review, we describe the genetic basis of such events and by extension the mechanisms promoting the emergence of new drug-resistant bacterial strains.

Antibiotic induced biofilm formation of novel multidrug resistant Acinetobacter baumannii ST2121 clone

The aim of this study was to identify antimicrobial resistance and virulence factor genes exhibited by multidrug resistant (MDR) Acinetobacter baumannii, to analyze biofilm formation and to investigate clonal subtypes of isolate. Whole genome sequencing was done by Illumina NovaSeq 6,000 platform and multilocus sequence typing (MLST) was performed by Oxford and Pasteur typing schemes. Influence of imipenem and levofloxacin on biofilm formation was investigated in 96-well plates at 3 replicates. The strain was found to carry OXA-23, OXA-51-like, AmpC and TEM-1 beta-lactamases. The sequence of the blaOXA-51-like gene has been identified as a blaOXA-66. According to Pasteur MLST scheme the strain displayed ST2 allelic profile. However, based on Oxford MLST scheme this strain represents the new ST2121, as the gdhB gene has a single allelic mutation namely, the gdhB-227. It was determined that MDR isolate carried bap, basABCDFGHIJ, csuA/BABCDE, bauABCDEF, plcD, pgaABCD, entE, barAB, ompA, abaIR, piT2EAFTE/AUBl, fimADT, cvaC, bfmR, bfmS virulence genes. In our study imipenem induced the highest biofilm formation at a concentration of 32 µg/ml and levofloxacin at a concentration of 16 µg/ml. In conclusion, we detected a new MDR A. baumannii ST2121 clone harboring blaOXA-66 gene that has been reported for the first time in Turkey.

Antibiotic Resistance and Genotypes of Nosocomial Strains of Acinetobacter baumannii in Kazakhstan

The aim of this study was to determine the prevalence of A. baumannii antibiotic-resistant strains in Kazakhstan and to characterize genotypes related to epidemic “high-risk” clones. Two hundred and twenty four A. baumannii isolates from four cities of Kazakhstan in 2011–2019 were studied. Antibiotic susceptibility testing was performed by using broth microdilutions method according to EUCAST (v 11.0) recommendations. The presence of bla_OXA-23-like, bla_{OXA-24/40-like,}bla_OXA-58-like,bla_VIM,bla_IMP, and bla_NDM genes was determined by PCR. Genotyping was performed using high-throughput real-time PCR detection of 21 SNPs at 10 chromosomal loci used in existing MLST schemes. Resistance rates to imipenem, meropenem, amikacin, gentamicin, and ciprofloxacin were 81.3%, 78.6%, 79.9%, 65.2%, and 89.3%, respectively. No colistin resistant isolates were detected. The values of the MIC 50% and the MIC 90% of tigecycline were 0.125 mg/L, only four isolates (1.8%) had the ECOFF value >0.5 mg/L. The presence of acquired carbapenemase genes was found in 82.2% strains, including bla_OXA-23-like (78.6%) or bla_OXA-58-like (3.6%) genes. The spreading of carbapenem resistant A. baumannii strains in Kazakhstan was associated with epidemic “high-risk” clonal groups, predominantly, CG208(92)^OXF/CG2^PAS (80.8%) and less often CG231(109)^OXF/CG1^PAS (1.8%).

Antibiotic Resistance Mechanisms and Their Transmission in Acinetobacter baumannii

The discovery of penicillin over 90 years ago and its subsequent uptake by healthcare systems around the world revolutionised global health. It marked the beginning of a golden age in antibiotic discovery with new antibiotics readily discovered from natural sources and refined into therapies that saved millions of lives. Towards the end of the last century, the rate of discovery slowed to a near standstill. The lack of discovery is compounded by the rapid emergence and spread of bacterial pathogens that exhibit resistance to multiple antibiotic therapies and threaten the sustainability of global healthcare systems. Acinetobacter baumannii is an opportunistic pathogen whose prevalence and impact has grown significantly over the last 20 years. It is recognised as a barometer of the antibiotic resistance crisis due to the diverse array of mechanisms by which it can become resistant.

CsrA Supports both Environmental Persistence and Host-Associated Growth of Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic and frequently multidrug-resistant Gram-negative bacterial pathogen that primarily infects critically ill individuals. Indirect transmission from patient to patient in hospitals can drive infections, supported by this organism's abilities to persist on dry surfaces and rapidly colonize susceptible individuals. To investigate how A. baumannii survives on surfaces, we cultured A. baumannii in liquid media for several days and then analyzed isolates that lost the ability to survive drying. One of these isolates carried a mutation that affected the gene encoding the carbon storage regulator CsrA. As we began to examine the role of CsrA in A. baumannii, we observed that the growth of ΔcsrA mutant strains was inhibited in the presence of amino acids. The ΔcsrA mutant strains had a reduced ability to survive drying and to form biofilms but an improved ability to tolerate increased osmolarity compared with the wild type. We also examined the importance of CsrA for A. baumannii virulence. The ΔcsrA mutant strains had a greatly reduced ability to kill Galleria mellonella larvae, could not replicate in G. mellonella hemolymph, and also had a growth defect in human serum. Together, these results show that CsrA is essential for the growth of A. baumannii on host-derived substrates and is involved in desiccation tolerance, implying that CsrA controls key functions involved in the transmission of A. baumannii in hospitals.

IS982 and kin: new insights into an old IS family

Insertion sequences (IS) are ubiquitous transposable elements with a very simple organization: two inverted repeats flanking a transposase coding gene. IS982 is one of 26 insertion sequence families known so far. With 70 registered members in the ISFinder database, this family remains somewhat unexplored, despite the association of many of its members with important features such as antibiotic resistance. IS982 has a fairly simple organization with a mean length of ca. 1 Kb, two inverted repeats with conserved 5' AC 3' ends flanking a transposase coding gene and direct repeats of variable lengths. Its transposase has a RNAse-H like chemistry with an atypical DDE motif. In this study, we first highlight the current knowledge on the IS982 family by dissecting its registered members and their characteristics. Secondly, we bring new insights into this old, yet uncharted IS family, by exploring its registered elements, as well as the genomic and proteomic databases of bacterial and archaeal strains. This probing showed that the presence and distribution of this family goes far beyond the clear-cut registry of ISFinder database.

Characterization of Extremely Drug-Resistant and Hypervirulent Acinetobacter baumannii AB030

Acinetobacter baumannii is an important nosocomial bacterial pathogen. Multidrug-resistant isolates of A. baumannii are reported worldwide. Some A. baumannii isolates display resistance to nearly all antibiotics, making treatment of infections very challenging. As the need for new and effective antibiotics against A. baumannii becomes increasingly urgent, there is a need to understand the mechanisms of antibiotic resistance and virulence in this organism. In this work, comparative genomics was used to understand the mechanisms of antibiotic resistance and virulence in AB030, an extremely drug-resistant and hypervirulent strain of A. baumannii that is a representative of a recently emerged lineage of A. baumannii International Clone V. In order to characterize AB030, we carried out a genomic and phenotypic comparison with LAC-4, a previously described hyper-resistant and hypervirulent isolate. AB030 contains a number of antibiotic resistance- and virulence-associated genes that are not present in LAC-4. A number of these genes are present on mobile elements. This work shows the importance of characterizing the members of new lineages of A. baumannii in order to determine the development of antibiotic resistance and virulence in this organism.

Phenotypic and genotypic characterization of carbapenem-resistant Acinetobacter baumannii isolates from Egypt

Background

Antibiotic use is largely under-regulated in Egypt leading to the emergence of resistant isolates. Carbapenems are last resort agents to treat Acinetobacter baumannii infections resistant to other classes of antibiotics. However, carbapenem-resistant isolates are emerging at an alarming rate. This study aimed at phenotypically and molecularly characterizing seventy four carbapenem-unsusceptible A. baumannii isolates from Egypt to detect the different enzymes responsible for carbapenem resistance.

Methods

Carbapenemase production was assessed by a number of phenotypic methods: modified Hodge test (MHT), carbapenem inactivation method (CIM), combined disc test (CDT), CarbAcineto NP test and boronic acid disc test. Polymerase chain reaction (PCR) was used to screen the isolates for the presence of some genes responsible for resistance to carbapenems, as well as some insertion sequences.

Results

PCR amplification of class D carbapenemases revealed the prevalence of bla_OXA-51 and bla_OXA-23 in 100% of the isolates and of bla_OXA-58 in only one isolate (1.4%). bla_VIM and bla_NDM-1 belonging to class B metallo-β-lactamases were present in 100 and 12.1% of the isolates, respectively. The prevalence of ISAba1, ISAba2 and ISAba3 was 100, 2.7 and 4.1%, respectively. None of the tested isolates carried bla_OXA-40, bla_IMP, bla_SIM, bla_SPM, bla_GIM or the class A bla_KPC. Taking PCR as the gold standard method for the detection of different carbapenemases, the sensitivities of the MHT, CIM, CDT, CarbAcineto NP test and boronic acid disc/imipenem or meropenem test for this particular collection of isolates were 78.4, 68.9, 79.7, 95.9, and 56.8% or 70.3%, respectively.

Conclusions

The widespread detection of carbapenem-resistant A. baumannii (CR-AB) has become a real threat to the efficacy of treatment regimens. Among the studied cohort of CR-AB clinical isolates, bla_OXA-51, bla_OXA-23 and bla_VIM were the most prevalent, followed by bla_NDM-1 and bla_OXA-58. The genotypic detection of carbapenemases among CR-AB clinical isolates using PCR was most conclusive, followed closely by the phenotypic testing using CarbAcineto NP test.

Genetic Characterization of Plasmid-Borne bla OXA-58 in Distinct Acinetobacter Species

Although the bla_OXA-58 gene has been infrequently described in Brazil, contrasting with other bordering South American countries, we verified the maintenance of this resistance determinant over time among carbapenem-resistant Acinetobacter species isolates, not only in nosocomial settings but also in the environment. In addition, to the best of our knowledge, this is the first study to have used WPS analysis to evaluate the genetic surroundings of bla_OXA-58 in Brazil. Moreover, the A. seifertii and A. baumannii clinical strains evaluated in this study were recovered 17 years apart in hospitals located in distinct Brazilian geographic regions.

We characterize by whole-plasmid-sequence (WPS) two-plasmid-borne bla_OXA-58 obtained from Acinetobacter seifertii (Asp-1069) and A. baumannii (Acb-45063) clinical strains recovered 17 years apart from distinct Brazilian regions. Multilocus sequence type (MLST) analysis showed that the Asp-1069 and Acb-45063 strains belong to ST551 and ST15/CC15, respectively. WPS analysis demonstrated that bla_OXA-58 was located in two distinct plasmids named pAs1069_a (24,672 bp/44 open reading frames [ORFs]) and pAb45063_b (19,808 bp/24 ORFs), which belong to the GR8/GR23 (repAci23) and GR4 (repAci4) incompatibility groups, respectively. The genetic environments surrounding bla_OXA-58 revealed that it was flanked by two intact ISAba3 copies on pAb45063_b, which differed from pAs1069_a. In the latter, the upstream ISAba3 copy was truncated by insertion of ISAba825 element. Although Re27-specific recombination sites were found adjacent to ISAba3-bla_OXA-58-ISAba3 arrangement on pAb45063_b, such structures were absent on pAs1069_a. The conserved ISAba125-araC1-lysE arrangement was disrupted by TnaphA6 harboring the aminoglycosides resistance gene aphA6 on pAs1069_a, while an IS26-bla_TEM-1-aac(3)-IIa-IS26 genetic structure was found upstream from ISAba3-bla_OXA-58-ISAba3 on pAb45063_b. Other two plasmids, pAb45063_a (183,767 bp/209 ORFs) and pAs1069_b (13,129 bp/14 ORFs), were also found in the OXA-58-producing Acinetobacter species strains, harboring the strA and strB genes and the sul2 gene, which confer resistance to streptomycin and sulfonamides, respectively. The plasmid-mediated virulence factors corresponding to genes tonB, spl, glmM, ppa, sulP, and map were found in both strains, as well distinct toxin-antitoxin system-encoding genes stbD and relE (pAs1069_a), brnT and brnA (pAb45063_b), and xreE (pAb45063_a). Although infrequently reported in Brazil, plasmid-borne bla_OXA-58 showed a complex and diverse genetic backbone that confers stability in different Acinetobacter species that have been isolated from nosocomial settings over time.

IMPORTANCE Although the bla_OXA-58 gene has been infrequently described in Brazil, contrasting with other bordering South American countries, we verified the maintenance of this resistance determinant over time among carbapenem-resistant Acinetobacter species isolates, not only in nosocomial settings but also in the environment. In addition, to the best of our knowledge, this is the first study to have used WPS analysis to evaluate the genetic surroundings of bla_OXA-58 in Brazil. Moreover, the A. seifertii and A. baumannii clinical strains evaluated in this study were recovered 17 years apart in hospitals located in distinct Brazilian geographic regions.

NDM-1 carbapenemase in Acinetobacter baumannii sequence type 32 in Ecuador

Objectives

To describe a clinical case of Acinetobacter baumannii sequence type (ST) 32 harbouring a New Delhi metallo-β-lactamase (NDM) in Ecuador.

Methods

We used multilocus sequence typing (MLST) to confirm the bacterial species and the sequence type of an A. baumannii isolate. We used synergy with the imipenem–EDTA disc method and the carbapenem inactivation method (CIM) to determine carbapenemase production; the presence of a carbapenemase gene was confirmed by PCR amplification and amplicon sequencing.

Results

Molecular characterization revealed the presence of A. baumannii ST32 harbouring the bla_NDM-1 gene in Ecuador. The bla_NDM-1 gene was isolated through PCR and amplified from a purified plasmid.

Conclusions

To the best of our knowledge, this is the first report of A. baumannii ST32 harbouring the bla_NDM-1 gene.

Co-occurrence of mcr-1 in the chromosome and on an IncHI2 plasmid: persistence of colistin resistance in Escherichia coli

Two colistin-resistant Escherichia coli strains (FS13Z2S and FS3Z6C) possessing chromosomally encoded mcr-1 isolated from swine were characterised. Whole-genome sequencing revealed that in strain FS13Z2S mcr-1 occurred in triplicate in the chromosome with another copy encoded on a pHNSHP45-2-like IncHI2 plasmid, whereas in strain FS3Z6C only one copy mcr-1 was inserted in the chromosome. It seems likely that the triplication of chromosomal copies of mcr-1 in FS13Z2S is due to intramolecular transposition events via a composite transposon containing an mcr-1 cassette bracketed by two copies of insertion sequence ISApl1, and the pap2 gene at the insertion site was truncated by an IS1294-like element. In plasmid pFS13Z2S and the chromosome of strain FS3Z6C, only a single copy of ISApl1 was present upstream of the mcr-1 cassette. The two strains exhibited similar colistin minimum inhibitory concentrations (MICs) and featured phosphoethanolamine addition to lipid A, without regard to the copy number of mcr-1. The mcr-1-harbouring plasmid was unstable in wild-type strain FS13Z2S and was quickly lost after 7 days of passage on colistin-free Luria-Bertani broth containing 0.5% SDS, but the mcr-1 copies on the chromosome persisted. These results reveal that the single copy of mcr-1 could result in modification of lipopolysaccharide (LPS) and cause colistin resistance in E. coli. Acquisition of multiple copies of mcr-1, especially on the chromosome, would facilitate stable persistence of colistin resistance in the host strain.

First Detection of GES-5 Carbapenemase-Producing Acinetobacter baumannii Isolate

This study was conducted to investigate the molecular epidemiology of resistance in Acinetobacter baumannii isolates collected at a hospital in Riyadh, Saudi Arabia, from January through December 2010. Twenty-seven A. baumannii were highly resistant (MIC₉₀ > 256 μg/ml) to ceftazidime, cefepime, and aztreonam. Imipenem resistance was seen in 24 isolates, of which 18 had an minimum inhibitory concentration (MIC) >32 μg/mL. Ciprofloxacin, gentamicin, and amikacin resistance was found in 93%, 52%, and 37% of all the isolates, respectively. Moreover, 8 (30%) isolates showed colistin resistance, and 15 (56%) were found to have MICs ≥4 μg/mL for tigecycline. The frequency of ADC, GES-1, GES-11, and GES-5 were 96.3% (n = 26), 18.5% (n = 5), 11% (n = 3), and 3.7% (n = 1), respectively. OXA-23 was found in 63% (n = 17) of the isolates; ISAba1 was found upstream of OXA-23 in 16. OXA-24/40 was detected in only one strain. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis revealed that the 27 strains were distributed in 8 sequence types (STs) and 16 clonal pulsotypes (A-P). Five singleton STs were identified, including ST15 and ST113-ST116. The emergence of multidrug-resistant A. baumannii is becoming a major concern in Saudi Arabia. Metallo-β-lactamases have no role in carbapenem resistance in this collection. The spread of OXA-23 in our strains occurred across different STs and pulsotypes, unlike what has been observed in many other countries. PFGE typing was more discriminatory than MLST. The high frequency of colistin and tigecycline resistance found in the isolates calls for continuous monitoring. This study describes the first identification of GES-5 conferring carbapenem resistance in A. baumannii.

Detection of blaOXA-23-like and blaNDM-1 in Acinetobacter baumannii from the Eastern Region, Saudi Arabia

Acinetobacter baumannii is currently considered as one of the most common successful pathogens in the healthcare system due to its ability to quickly develop resistance. Ten carbapenem-resistant A. calcoaceticus-baumannii complex were isolated from the eastern region, Saudi Arabia in 2014. All isolates were resistant to ciprofloxacin, however, 8 of 10 isolates were tigecycline resistant. Susceptibility test was also carried out for three aminoglycosides, resistance to gentamicin was 80%, amikacin was 90%, and tobramycin was 50%. Colistin susceptibility was seen in all isolates. The 10 isolates harbored bla_OXA-23-like and ISAba1 and 9 of them also carried bla_ADC. Three isolates of 10 harbored bla_NDM-1 coding for NDM metallo-β-lactamase (MBL) with coexistence of bla_ADC together with either bla_GES or bla_TEM or both. Those three isolates exhibited negative Etest MBL screening test. Pulsed-field gel electrophoresis revealed the high clonal variability of the isolates, although two isolates were indistinguishable. The risk of dissemination of carbapenem resistance through presence of ISAba1 upstream of OXA-23-like in all isolates raises the concern about emergence of higher carbapenem prevalence rates in the future in our region. This study also demonstrated the importance of molecular surveillance to provide accurate and reliable data about the resistance rates of A. baumannii. Finally, the high incidence of NDM-1 among our isolates requires a routine surveillance to monitor the future prevalence of this enzyme in the region.

OXA β-lactamases

The OXA β-lactamases were among the earliest β-lactamases detected; however, these molecular class D β-lactamases were originally relatively rare and always plasmid mediated. They had a substrate profile limited to the penicillins, but some became able to confer resistance to cephalosporins. From the 1980s onwards, isolates of Acinetobacter baumannii that were resistant to the carbapenems emerged, manifested by plasmid-encoded β-lactamases (OXA-23, OXA-40, and OXA-58) categorized as OXA enzymes because of their sequence similarity to earlier OXA β-lactamases. It was soon found that every A. baumannii strain possessed a chromosomally encoded OXA β-lactamase (OXA-51-like), some of which could confer resistance to carbapenems when the genetic environment around the gene promoted its expression. Similarly, Acinetobacter species closely related to A. baumannii also possessed their own chromosomally encoded OXA β-lactamases; some could be transferred to A. baumannii, and they formed the basis of transferable carbapenem resistance in this species. In some cases, the carbapenem-resistant OXA β-lactamases (OXA-48) have migrated into the Enterobacteriaceae and are becoming a significant cause of carbapenem resistance. The emergence of OXA enzymes that can confer resistance to carbapenems, particularly in A. baumannii, has transformed these β-lactamases from a minor hindrance into a major problem set to demote the clinical efficacy of the carbapenems.

The transferability of blaOXA-23 gene in multidrug-resistant Acinetobacter baumannii isolates from Saudi Arabia and Egypt

Carbapenem-resistant Acinetobacter spp. have been increasingly reported worldwide including Saudi Arabia and Egypt. We examined 64, non-repetitive, Acinetobacter baumannii isolates collected in 2013 and 2014 from four different medical centres (two from Saudi Arabia and two from Egypt). All the isolates were resistant to ceftazidime and ciprofloxacin. The intI1 harbouring blaGES-11 and aac-6'-1b was detected in 19% (n=12) of the isolates. ISAba1 over-expression of blaADC gene was observed in 65% (n=42) of isolates. Of all the isolates 19% (n=12) had ISAba1 upstream of the blaOXA-51-like gene, 69% (n=44) carried the blaOXA-23 gene within the Tn2006 structure, 8% (n=5) had blaOXA-24-like gene and 9% (n=6) harboured either blaVIM-2 or blaNDM-1 gene. Eighty nine percent (n=57) of isolates were resistant to imipenem and had an MIC of ≥8mg/L. Pulsed-field gel electrophoresis (PFGE) typing revealed the presence of 23 different PFGE. Three PFGE types were very widespread, ST236 (CC104) (PFGE type 1, n=15), ST208 (CC92) (PFGE type 2, n=10), ST884 (CC unassigned) (PFGE type 3, n=7) in and across all four medical centres. The blaOXA-23 gene was found to be present on a 60kb transferable plasmid in both PFGE type 1 and 2 but was absent in PFGE type 3. This is the first study to report on the emergence of ST236 in Saudi Arabia and Egypt, and spread of distinct carbapenem resistant A. baumannii clones belonging to ST884, ST945 and ST1096 in Saudi Arabia.

Variations in IS6 promoters alter the expression of carbapenem resistance in related strains of Acinetobacter baumannii

The aim of this work was to investigate the role of the IS6 family of insertion sequences present upstream of bla_OXA-58 in two clonally related carbapenem-resistant Acinetobacter baumannii isolates obtained from paediatric cancer patients in Egypt. To determine their relatedness, the isolates were typed by pulsed-field gel electrophoresis (PFGE), and the intrinsic bla_OXA-51-like gene was amplified and sequenced. Minimum inhibitory concentrations (MICs) to imipenem and meropenem was determined according to British Society of Antimicrobial Chemotherapy (BSAC) guidelines. PCR and sequencing of bla_OXA-58 and the upstream and downstream regions was performed to determine the genetic environment. The two isolates were positive for the intrinsic bla_OXA-64 gene, and the MICs for isolates AB-14298 and AB-P67 were 8mg/L and 64mg/L for imipenem and 2mg/L and 16mg/L for meropenem, respectively. The bla_OXA-58 gene in AB-14298 was flanked by ISAba3 interrupted with IS1006, whereas AB-P67 had ISAba3 interrupted by IS1008, both belonging to the IS6 family of insertion sequences. In conclusion, both IS1006 and IS1008 provided suitable promoter sequences for expression of the downstream bla_OXA-58 gene.

Diversity in Acinetobacter baumannii isolates from paediatric cancer patients in Egypt

Acinetobacter baumannii is an important nosocomial pathogen, commonly causing infections in immunocompromised patients. It is increasingly reported as a multidrug-resistant organism, which is alarming because of its capability to resist all available classes of antibiotics including carbapenems. The aim of this study was to examine the genetic and epidemiological diversity of A. baumannii isolates from paediatric cancer patients in Egypt, by sequencing the intrinsic blaOXA -51-like gene, genotyping by pulsed-field gel electrophoresis and multi-locus sequence typing in addition to identifying the carbapenem-resistance mechanism. Results showed a large diversity within the isolates, with eight different blaOXA -51-like genes, seven novel sequence types and only 28% similarity by pulsed-field gel electrophoresis. All three acquired class-D carbapenemases (OXA-23, OXA-40 and OXA-58) were also identified among these strains correlating with resistance to carbapenems. In addition, we report the first identification of ISAba2 upstream of blaOXA -51-like contributing to high-level carbapenem resistance. This indicates the presence of several clones of A. baumannii in the hospitals and illustrates the large genetic and epidemiological diversity found in Egyptian strains.