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149200.9054Characterization of the tet(M)-bearing transposon Tn7125 of Escherichia coli strain A13 isolated from an intensive pig farm located in Henan province, China. BACKGROUND: Transposons carrying tet(M) in Gram-positive bacteria have been reported extensively, while there is a paucity of data on the transmission characteristics of tet(M) in Gram-negative bacteria. Therefore, the aim of this study was to investigate the genetic characteristics of the tet(M)-bearing transposon Tn7125, and to clarify the transmission mechanism of the plasmids pTA13-1 and pTA13-3 in Escherichia coli strain A13. METHODS: Plasmids from strain A13 and a corresponding transconjugant were determined by whole genome sequencing and analyzed using bioinformatics tools. The plasmids pTA13-1 and pTA13-3 of the transconjugant TA13 were characterized by S1-pulse-field gel electrophoresis, Southern hybridization, stability experiments, and direct competition assays. RESULTS: The conjugated IncF2:A6:B20 plasmid pTA13-1 co-transferred with the 41-kb plasmid pTA13-3, which carried no resistance genes; plasmid pTA13-2, which harbored the replication initiator PO111; and the IncX4 plasmid pTA13-4, which harbored the antibiotic resistance gene mcr-1. The novel IS26-bracked composite transposon Tn7125 was located on plasmid pTA13-1, which mainly consists of three resistance modules: IS26-ctp-lp-tet(M)-hp-IS406tnp, qac-aadA1-cmlA1-aadA2-DUF1010-dfrA12, and ∆ISVSa3-VirD-floR-LysR-ISVSa3. The plasmid pTA13-1 was highly stable in E. coli strain J53 with no fitness cost to the host or disadvantage in growth competition. CONCLUSION: Evolution of co-integrated transposons, such as Tn7125, may convey antibiotic resistance to a wide spectrum of hosts via the plasmids pTA13-1 and pTA13-3, which acts as an adaptable and mobile multidrug resistance reservoir to accelerate dissemination of other genes by co-selection, thereby posing a potentially serious barrier to clinical treatment regimens.202540639501
634910.9034High-level chromate resistance in Arthrobacter sp. strain FB24 requires previously uncharacterized accessory genes. BACKGROUND: The genome of Arthrobacter sp. strain FB24 contains a chromate resistance determinant (CRD), consisting of a cluster of 8 genes located on a 10.6 kb fragment of a 96 kb plasmid. The CRD includes chrA, which encodes a putative chromate efflux protein, and three genes with amino acid similarities to the amino and carboxy termini of ChrB, a putative regulatory protein. There are also three novel genes that have not been previously associated with chromate resistance in other bacteria; they encode an oxidoreductase (most similar to malate:quinone oxidoreductase), a functionally unknown protein with a WD40 repeat domain and a lipoprotein. To delineate the contribution of the CRD genes to the FB24 chromate [Cr(VI)] response, we evaluated the growth of mutant strains bearing regions of the CRD and transcript expression levels in response to Cr(VI) challenge. RESULTS: A chromate-sensitive mutant (strain D11) was generated by curing FB24 of its 96-kb plasmid. Elemental analysis indicated that chromate-exposed cells of strain D11 accumulated three times more chromium than strain FB24. Introduction of the CRD into strain D11 conferred chromate resistance comparable to wild-type levels, whereas deletion of specific regions of the CRD led to decreased resistance. Using real-time reverse transcriptase PCR, we show that expression of each gene within the CRD is specifically induced in response to chromate but not by lead, hydrogen peroxide or arsenate. Higher levels of chrA expression were achieved when the chrB orthologs and the WD40 repeat domain genes were present, suggesting their possible regulatory roles. CONCLUSION: Our findings indicate that chromate resistance in Arthrobacter sp. strain FB24 is due to chromate efflux through the ChrA transport protein. More importantly, new genes have been identified as having significant roles in chromate resistance. Collectively, the functional predictions of these additional genes suggest the involvement of a signal transduction system in the regulation of chromate efflux and warrants further study.200919758450
494420.9033Genomic characterization of Escherichia coli LCT-EC001, an extremely multidrug-resistant strain with an amazing number of resistance genes. BACKGROUND: Multidrug resistance is a growing global public health threat with far more serious consequences than generally anticipated. In this study, we investigated the antibiotic resistance and genomic traits of a clinical strain of Escherichia coli LCT-EC001. RESULTS: LCT-EC001 was resistant to 16 kinds of widely used antibiotics, including fourth-generation cephalosporins and carbapenems. In total, up to 68 determinants associated with antibiotic resistance were identified, including 8 beta-lactamase genes (notably producing ESBLs and KPCs), 31 multidrug efflux system genes, 6 outer membrane transport system genes, 4 aminoglycoside-modifying enzyme genes, 10 two-component regulatory system genes, and 9 other enzyme or transcriptional regulator genes, covering nearly all known drug-resistance mechanisms in E. coli. More than half of the resistance genes were located close to mobile genetic elements, such as plasmids, transposons, genomics islands, and insertion sequences. Phylogenetic analysis revealed that this strain may have evolved from E. coli K-12 but is a completely new MLST type. CONCLUSIONS: Antibiotic resistance was extremely severe in E. coli LCT-EC001, mainly due to mobile genetic elements that allowed the gain of a large quantity of resistance genes. The antibiotic resistance genes of E. coli LCT-EC001 can probably be transferred to other bacteria. To the best of our knowledge, this is the first report of a strain of E. coli which has such a large amount of antibiotic resistance genes. Apart from providing an E. coli reference genome with an extremely high multidrug-resistant background for future analyses, this work also offers a strategy for investigating the complement and characteristics of genes contributing to drug resistance at the whole-genome level.201931139265
300830.9031Sequence of conjugative plasmid pIP1206 mediating resistance to aminoglycosides by 16S rRNA methylation and to hydrophilic fluoroquinolones by efflux. Self-transferable IncFI plasmid pIP1206, isolated from an Escherichia coli clinical isolate, carries two new resistance determinants: qepA, which confers resistance to hydrophylic fluoroquinolones by efflux, and rmtB, which specifies a 16S rRNA methylase conferring high-level aminoglycoside resistance. Analysis of the 168,113-bp sequence (51% G+C) revealed that pIP1206 was composed of several subregions separated by copies of insertion sequences. Of 151 open reading frames, 56 (37%) were also present in pRSB107, isolated from a bacterium in a sewage treatment plant. pIP1206 contained four replication regions (RepFIA, RepFIB, and two partial RepFII regions) and a transfer region 91% identical with that of pAPEC-O1-ColBM, a plasmid isolated from an avian pathogenic E. coli. A putative oriT region was found upstream from the transfer region. The antibiotic resistance genes tet(A), catA1, bla(TEM-1), rmtB, and qepA were clustered in a 33.5-kb fragment delineated by two IS26 elements that also carried a class 1 integron, including the sulI, qacEDelta1, aad4, and dfrA17 genes and Tn10, Tn21, and Tn3-like transposons. The plasmid also possessed a raffinose operon, an arginine deiminase pathway, a putative iron acquisition gene cluster, an S-methylmethionine metabolism operon, two virulence-associated genes, and a type I DNA restriction-modification (R-M) system. Three toxin/antitoxin systems and the R-M system ensured stabilization of the plasmid in the host bacteria. These data suggest that the mosaic structure of pIP1206 could have resulted from recombination between pRSB107 and a pAPEC-O1-ColBM-like plasmid, combined with structural rearrangements associated with acquisition of additional DNA by recombination and of mobile genetic elements by transposition.200818458128
600640.9030Missense Mutations in the CrrB Protein Mediate Odilorhabdin Derivative Resistance in Klebsiella pneumoniae. NOSO-502 is a preclinical antibiotic candidate of the Odilorhabdin class. This compound exhibits activity against Enterobacteriaceae pathogens, including carbapenemase-producing bacteria and most of the Colistin (CST)-resistant strains. Among a collection of CST-resistant Klebsiella pneumoniae strains harboring mutations on genes pmrAB, mgrB, phoPQ, and crrB, only those bearing mutations in gene crrB were found to be resistant to NOSO-502.CrrB is a histidine kinase which acts with the response regulator CrrA to modulate the PmrAB system, which finally induces the restructuring of the lipopolysaccharide present on the outer membrane and thus leading to CST resistance. Moreover, crrB mutations also enhance the transcription of neighboring genes such as H239_3063, an ABC transporter transmembrane region; H239_3064, a putative efflux pump also known as KexD; and H239_3065, a N-acetyltransferase.To elucidate the mechanism of resistance to NOSO-502 induced by CrrB missense mutations in K. pneumoniae, mutants of NCTC 13442 and ATCC BAA-2146 strains resistant to NOSO-502 and CST with single amino acid substitutions in CrrB (S8N, F33Y, Y34N, W140R, N141I, P151A, P151L, P151S, P151T, F303Y) were selected. Full susceptibility to NOSO-502 was restored in crrA or crrB deleted K. pneumoniae NCTC 13442 CrrB(P151L) mutants, confirming the role of CrrAB in controlling this resistance pathway. Deletion of kexD (but no other neighboring genes) in the same mutant also restored NOSO-502-susceptibility. Upregulation of the kexD gene expression was observed for all CrrB mutants. Finally, plasmid expression of kexD in a K. pneumoniae strain missing the locus crrABC and kexD significantly increased resistance to NOSO-502.202333685902
300250.9022An IS26 variant with enhanced activity. The insertion sequence IS26 plays a major role in the mobilization, expression and dissemination of antibiotic resistance genes in Gram-negative bacteria. Though IS26 is abundant in sequenced genomes and in plasmids that harbour antibiotic resistance genes, only a few minor variations in the IS26 sequence have been recorded. The most common variant, IS26* (also known as IS15Δ1), encodes a Tnp26 transposase with a single amino acid substitution, G184N in the catalytic domain. Using computational modelling, this substitution was predicted to increase the length of the helix that includes the E173 residue of the catalytic DDE triad, and its effect on activity was tested. An IS26 mutant generated in vitro producing Tnp26-G184N formed cointegrates in a standard untargeted reaction at 5-fold higher frequency than IS26 producing Tnp26. When the target included a single copy of IS26, the G184N substitution increased the cointegration frequency 10-fold and the reaction was targeted and conservative. Hence, the substitution increased Tnp26 activity. The longer helix may stabilise the position of the E173 of the DDE for the catalysis reaction and the specific G184N substitution may also enhance activity by increasing binding to the terminal inverted repeats.201930753435
244860.9022Emerging coexistence of three PMQR genes on a multiple resistance plasmid with a new surrounding genetic structure of qnrS2 in E. coli in China. BACKGROUND: Quinolones are commonly used for treatment of infections by bacteria of the Enterobacteriaceae family. However, the rising resistance to quinolones worldwide poses a major clinical and public health risk. This study aimed to characterise a novel multiple resistance plasmid carrying three plasmid-mediated quinolone resistance genes in Escherichia coli clinical stain RJ749. METHODS: MICs of ceftriaxone, cefepime, ceftazidime, ciprofloxacin, and levofloxacin for RJ749 and transconjugant c749 were determined by the Etest method. Conjugation was performed using sodium azide-resistant E. coli J53 strain as a recipient. The quinolone resistance-determining regions of gyrA, gyrB, parC, and parE were PCR-amplified. RESULTS: RJ749 was highly resistant to quinolones, while c749 showed low-level resistance. S1-nuclease pulsed-field gel electrophoresis revealed that RJ749 and c749 both harboured a plasmid. PCR presented chromosomal mutation sites of the quinolone resistance-determining region, which mediated quinolone resistance. The c749 genome comprised a single plasmid, pRJ749, with a multiple resistance region, including three plasmid-mediated quinolone resistance (PMQR) genes (aac (6')-Ib-cr, qnrS2, and oqxAB) and ten acquired resistance genes. One of the genes, qnrS2, was shown for the first time to be flanked by two IS26s. Three IS26-mediated circular molecules carrying the PMQR genes were detected. CONCLUSIONS: We revealed the coexistence of three PMQR genes on a multiple resistance plasmid and a new surrounding genetic structure of qnrS2 flanked by IS26 elements. IS26 plays an important role in horizontal spread of quinolone resistance.202032293532
151770.9020Co-occurrence of blaNDM-1, rmtC, and mcr-9 in multidrug-resistant Enterobacter kobei strain isolated from an infant with urinary tract infection. OBJECTIVES: The co-emergence of mcr and carbapenem resistance genes in Gram-negative bacteria is a serious problem. This study aims to clarify the genetic characteristic of one novel multidrug-resistant Enterobacter kobei EC1382 with mcr-9 causing urinary tract inflammation in an infant. METHODS: Antimicrobial drug susceptibility testing was performed for this isolate using the broth microdilution method. Whole-genome sequencing was performed using the Illumina PacBio RS II platform and HiSeq platform, and the antimicrobial resistance genes, mobile elements, and plasmid replicon types were identified. Conjugation analysis was performed using Escherichia coli C600 as recipients. RESULTS: Enterobacter kobei EC1382 was resistant to carbapenem, aminoglycoside, and cephalosporin. Twenty-five antimicrobial resistance genes were identified, including genes conferring resistance to carbapenem (blaNDM-1), colistin (mcr-9), and aminoglycosides (rmtC). The blaNDM-1 gene, accompanied by bleMBL and rmtC located downstream of an ISCR14 element, was detected in the IncFII(Yp) type plasmid pEC1382-2. Interestingly, although E. kobei EC1382 was susceptible to colistin, it had three identical mcr-9 genes (two in the chromosome and one in the IncHI2-type plasmid pEC1382-1). The backbone (∼12.2-kb genetic fragment) of these mcr-9 (flanked by IS903B and IS481-IS26) regions were conserved in this strain, and they were found to be present in various bacteria as three types, implying a silent distribution. CONCLUSIONS: To the best of our knowledge, this is the first study to demonstrate the coexistence of blaNDM-1, rmtC, and mcr-9 in E. kobei. The silent prevalence of mcr-9 in bacteria may be a threat to public health.202337062506
301280.9017Characterization of the IncA/C plasmid pSCEC2 from Escherichia coli of swine origin that harbours the multiresistance gene cfr. OBJECTIVES: To determine the complete nucleotide sequence of the multidrug resistance plasmid pSCEC2, isolated from a porcine Escherichia coli strain, and to analyse it with particular reference to the cfr gene region. METHODS: Plasmid pSCEC2 was purified from its E. coli J53 transconjugant and then sequenced using the 454 GS-FLX System. After draft assembly, predicted gaps were closed by PCR with subsequent sequencing of the amplicons. RESULTS: Plasmid pSCEC2 is 135 615 bp in size and contains 200 open reading frames for proteins of ≥100 amino acids. Analysis of the sequence of pSCEC2 revealed two resistance gene segments. The 4.4 kb cfr-containing segment is flanked by two IS256 elements in the same orientation, which are believed to be involved in the dissemination of the rRNA methylase gene cfr. The other segment harbours the resistance genes floR, tet(A)-tetR, strA/strB and sul2, which have previously been found on other IncA/C plasmids. Except for these two resistance gene regions, the pSCEC2 backbone displayed >99% nucleotide sequence identity to that of other IncA/C family plasmids isolated in France, Chile and the USA. CONCLUSIONS: The cfr gene was identified on an IncA/C plasmid, which is well known for its broad host range and transfer and maintenance properties. The location on such a plasmid will further accelerate the dissemination of cfr and co-located resistance genes among different Gram-negative bacteria. The genetic context of cfr on plasmid pSCEC2 underlines the complexity of cfr transfer events and confirms the role that insertion sequences play in the spread of cfr.201424013193
200590.9017Chromosomal 16S Ribosomal RNA Methyltransferase RmtE1 in Escherichia coli Sequence Type 448. We identified rmtE1, an uncommon 16S ribosomal methyltransferase gene, in an aminoglycoside- and cephalosporin-resistant Escherichia coli sequence type 448 clinical strain co-harboring bla(CMY-2). Long-read sequencing revealed insertion of a 101,257-bp fragment carrying both resistance genes to the chromosome. Our findings underscore E. coli sequence type 448 as a potential high-risk multidrug-resistant clone.201728418308
2997100.9017Genomic Characterization of Multidrug-Resistant Escherichia coli BH100 Sub-strains. The rapid emergence of multidrug-resistant (MDR) bacteria is a global health problem. Mobile genetic elements like conjugative plasmids, transposons, and integrons are the major players in spreading resistance genes in uropathogenic Escherichia coli (UPEC) pathotype. The E. coli BH100 strain was isolated from the urinary tract of a Brazilian woman in 1974. This strain presents two plasmids carrying MDR cassettes, pBH100, and pAp, with conjugative and mobilization properties, respectively. However, its transposable elements have not been characterized. In this study, we attempted to unravel the factors involved in the mobilization of virulence and drug-resistance genes by assessing genomic rearrangements in four BH100 sub-strains (BH100 MG2014, BH100 MG2017, BH100L MG2017, and BH100N MG2017). Therefore, the complete genomes of the BH100 sub-strains were achieved through Next Generation Sequencing and submitted to comparative genomic analyses. Our data shows recombination events between the two plasmids in the sub-strain BH100 MG2017 and between pBH100 and the chromosome in BH100L MG2017. In both cases, IS3 and IS21 elements were detected upstream of Tn21 family transposons associated with MDR genes at the recombined region. These results integrated with Genomic island analysis suggest pBH100 might be involved in the spreading of drug resistance through the formation of resistance islands. Regarding pathogenicity, our results reveal that BH100 strain is closely related to UPEC strains and contains many IS3 and IS21-transposase-enriched genomic islands associated with virulence. This study concludes that those IS elements are vital for the evolution and adaptation of BH100 strain.202033584554
1535110.9016Complete Genome Sequencing of Acinetobacter baumannii AC1633 and Acinetobacter nosocomialis AC1530 Unveils a Large Multidrug-Resistant Plasmid Encoding the NDM-1 and OXA-58 Carbapenemases. Carbapenem-resistant Acinetobacter spp. are considered priority drug-resistant human-pathogenic bacteria. The genomes of two carbapenem-resistant Acinetobacter spp. clinical isolates obtained from the same tertiary hospital in Terengganu, Malaysia, namely, A. baumannii AC1633 and A. nosocomialis AC1530, were sequenced. Both isolates were found to harbor the carbapenemase genes bla(NDM-1) and bla(OXA-58) in a large (ca. 170 kb) plasmid designated pAC1633-1 and pAC1530, respectively, that also encodes genes that confer resistance to aminoglycosides, sulfonamides, and macrolides. The two plasmids were almost identical except for the insertion of ISAba11 and an IS4 family element in pAC1633-1, and ISAba11 along with relBE toxin-antitoxin genes flanked by inversely orientated pdif (XerC/XerD) recombination sites in pAC1530. The bla(NDM-1) gene was encoded in a Tn125 composite transposon structure flanked by ISAba125, whereas bla(OXA-58) was flanked by ISAba11 and ISAba3 downstream and a partial ISAba3 element upstream within a pdif module. The presence of conjugative genes in plasmids pAC1633-1/pAC1530 and their discovery in two distinct species of Acinetobacter from the same hospital are suggestive of conjugative transfer, but mating experiments failed to demonstrate transmissibility under standard laboratory conditions. Comparative sequence analysis strongly inferred that pAC1633-1/pAC1530 was derived from two separate plasmids in an IS1006-mediated recombination or transposition event. A. baumannii AC1633 also harbored three other plasmids designated pAC1633-2, pAC1633-3, and pAC1633-4. Both pAC1633-3 and pAC1633-4 are cryptic plasmids, whereas pAC1633-2 is a 12,651-bp plasmid of the GR8/GR23 Rep3-superfamily group that encodes the tetA(39) tetracycline resistance determinant in a pdif module.IMPORTANCE Bacteria of the genus Acinetobacter are important hospital-acquired pathogens, with carbapenem-resistant A. baumannii listed by the World Health Organization as the one of the top priority pathogens. Whole-genome sequencing of carbapenem-resistant A. baumannii AC1633 and A. nosocomialis AC1530, which were isolated from the main tertiary hospital in Terengganu, Malaysia, led to the discovery of a large, ca. 170-kb plasmid that harbored genes encoding the New Delhi metallo-β-lactamase-1 (NDM-1) and OXA-58 carbapenemases alongside genes that conferred resistance to aminoglycosides, macrolides, and sulfonamides. The plasmid was a patchwork of multiple mobile genetic elements and comparative sequence analysis indicated that it may have been derived from two separate plasmids through an IS1006-mediated recombination or transposition event. The presence of such a potentially transmissible plasmid encoding resistance to multiple antimicrobials warrants vigilance, as its spread to susceptible strains would lead to increasing incidences of antimicrobial resistance.202133504662
6350120.9016Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1. BACKGROUND: Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate [Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by Bacillus cereus SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence. RESULTS: Bacillus cereus SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, chrIA1, and two additional chrA genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene azoR and four nitroreductase genes nitR possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes chrA1 and chrI was induced in response to Cr(VI) but expression of the other two chromate transporter genes chrA2 and chrA3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of chrIA1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of chrIA1 in B. cereus SJ1 implied the possibility of recent horizontal gene transfer. CONCLUSION: Our results indicate that expression of the chromate transporter gene chrA1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the chrIA1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of B. cereus SJ1.201020723231
3018130.9015The large Bacillus plasmid pTB19 contains two integrated rolling-circle plasmids carrying mobilization functions. Plasmid pTB19 is a 27-kb plasmid originating from a thermophilic Bacillus species. It was shown previously that pTB19 contains an integrated copy of the rolling-circle type plasmid pTB913. Here we describe the analysis of a 4324-bp region of pTB19 conferring resistance to tetracycline. The nucleotide sequence of this region revealed all the characteristics of a second plasmid replicating via the rolling-circle mechanism. This sequence contained (i) the tetracycline resistance marker of pTB19, which is highly similar to other tetL-genes of gram-positive bacteria; (ii) a hybrid mob gene, which bears relatedness to both the mob-genes of pUB110 and pTB913; (iii) a palU type minus origin identical to those of pUB110 and pTB913; and (iv) a plus origin of replication similar to that of pTB913. A repB-type replication initiation gene sequence identical to that of pTB913 was present, which lacked the middle part (492 bp), thus preventing autonomous replication of this region. The hybrid mob gene was functional in conjugative mobilization of plasmids between strains of Bacillus subtilis.19911946749
1754140.9014Transposons Carrying the aacC2e Aminoglycoside and bla(TEM) Beta-Lactam Resistance Genes in Acinetobacter. This study examines the genetic contexts and evolutionary steps responsible for the formation of the widely spread transposon Tn6925 carrying bla(TEM) and aacC2e, which confers resistance to beta-lactam and aminoglycoside antibiotics in Gram-negative bacteria. The bla(TEM-1) and aacC2e genes were found in several transposons. They were first observed within an IS26 bounded 3.7 kb transposon (Tn6925) on several Acinetobacter baumannii plasmids located within a 4.7 kb dif module. Truncated and expanded variations of Tn6925 were found across other A. baumannii plasmids, as well as in other Gram-negative bacteria (including Vibrio cholerae). Moreover, bla(TEM-1) and aacC2e were in much larger resistance-heavy transposons including the ISAba1-bounded 24.6 kb (here called Tn6927), found in an A. baumannii chromosome. A novel ISKpn12-bounded transposon was also observed to contain bla(TEM) and aacC2e which was found interrupting Tn5393 along with an IS26 pseudo-compound transposon to form a 24.9 kb resistance island in an Acinetobacter pittii plasmid. Multiple mobile genetic elements are involved in the formation of transposon structures that circulate bla(TEM) and aacC2e. Among these, IS26 and ISAba1 appear to have played a major role in the formation and spread of these elements in the Acinetobacter species.202438593463
826150.9013Sequence identity with type VIII and association with IS176 of type IIIc dihydrofolate reductase from Shigella sonnei. An uncommon dihydrofolate reductase (DHFR), type IIIc, was coded for by Shigella sonnei that harbors plasmid pBH700 and that was isolated in North Carolina. The trimethoprim resistance gene carried on pBH700 was subcloned and sequenced. The nucleotide sequence of the gene encoding type IIIc DHFR was identical to the gene encoding type VIII DHFR. The type IIIc amino acid sequence was approximately 50% similar to those of DHFRs commonly found in enteric bacteria. Furthermore, this gene was flanked by IS176 (IS26), an insertion sequence usually associated with those of aminoglycoside resistance genes. The gene for type IIIc DHFR was located by hybridization within a 1,993-bp PstI fragment in each of eight conjugative plasmids from geographically diverse strains of S. sonnei. Each plasmid also conferred resistance to ampicillin, streptomycin, and sulfamethoxazole and belonged to incompatibility group M. Plasmids carrying this new trimethoprim resistance gene, which is uniquely associated with IS176, have disseminated throughout the United States.19957695291
5032160.9011Hijacking a small plasmid to confer high-level resistance to aztreonam-avibactam and ceftazidime-avibactam. Acquired β-lactamase-encoding genes are typically carried by large plasmids in Gram-negative bacteria, which also commonly carry multi-copy small plasmids. This study found that mobile genetic elements carrying antimicrobial resistance genes are capable of hijacking small plasmids. This study focused on aztreonam-avibactam (ATM-AVI) as this combination can be used to effectively counter almost all β-lactamases produced by bacteria, and has been recommended against carbapenem-resistant Enterobacterales. A clinical strain (085003) of carbapenem-resistant Escherichia coli was investigated, and mutants (085003R32 and 085003R512) able to grow under 32/4 and 512/4 mg/L of ATM-AVI were obtained as representatives of low- and high-level resistance, respectively, by induction. Comparative genomics showed that 085003R32 and 085003R512 had a single nucleotide mutation of β-lactamase gene bla(CMY-2), encoding a novel CMY with a Thr319Ile substitution, assigned 'CMY-2R'. Cloning and enzyme kinetics were used to verify that CMY-2R conferred ATM-AVI resistance by compromising binding of AVI and subsequent protection of ATM. Mechanisms for the discrepant resistance between 085003R32 and 085003R512 were investigated. Three tandem copies of bla(CMY-2R) were identified on a self-transmissible IncP1 plasmid of 085003R32 due to IS1294 misrecognizing its end terIS and rolling-circle replication. 085003R512 had only a single copy of bla(CMY-2R) on the IncP1 plasmid, but possessed anther bla(CMY-2R) on an already present 4-kb small plasmid. IS1294-mediated mobilization on to this multi-copy small plasmid increased the copy number of bla(CMY-2R) significantly, rendering higher resistance. This study shows that bacteria can employ multiple approaches to accommodate selection pressures imposed by exposure to varied concentrations of antimicrobial agents.202337769749
517170.9011Adaptation to metal(loid)s in strain Mucilaginibacter rubeus P2 involves novel arsenic resistance genes and mechanisms. Arsenic is a ubiquitous environmental toxi substance that affects human health. Compared to inorganic arsenicals, reduced organoarsenicals are more toxic, and some of them are recognized as antibiotics, such as methylarsenite [MAs(III)] and arsinothricin (2-amino-4-(hydroxymethylarsinoyl)butanoate, or AST). To date, organoarsenicals such as MAs(V) and roxarsone [Rox(V)] are still used in agriculture and animal husbandry. How bacteria deal with both inorganic and organoarsenic species is unclear. Recently, we identified an environmental isolate Mucilaginibacter rubeus P2 that has adapted to high arsenic and antinomy levels by triplicating an arsR-mrarsU(Bact)-arsN-arsC-(arsRhp)-hp-acr3-mrme1(Bact)-mrme2(Bact)gene cluster. Heterologous expression of mrarsM(Bact), mrarsU(Bact), mrme1(Bact) and mrme2(Bact), encoding putative arsenic resistance determinants, in the arsenic hypersensitive strain Escherichia coli AW3110 conferred resistance to As(III), As(V), MAs(III) or Rox(III). Our data suggest that metalloid exposure promotes plasticity in arsenic resistance systems, enhancing host organism adaptation to metalloid stress.202437865075
1998180.9011Characterization of a blaNDM‑1‑harboring plasmid from a Salmonella enterica clinical isolate in China. The plasmid-mediated transmission of antibiotic resistance genes has been reported to be involved in the development of antibiotic resistance in bacteria, and poses a serious threat for the success of bacterial infection treatment and human health worldwide. The present study used a 454 GS‑FLX pyrosequencing system to determine the ~140 kb nucleotide sequence of plasmid pHS36‑NDM, which was identified in a Salmonella Stanley isolate from the stool sample of an 11‑month‑old girl at Lishui Central Hospital, China, and which contains a New Delhi metallo‑β‑lactamase‑1 (NDM‑1) carbapenem resistance gene (blaNDM‑1). The 181 open reading frames encode proteins with functions including replication, stable inheritance, antibiotic resistance and mobile genetic elements. Both horizontal transfer and passage stability‑related genes were identified in pHS36‑NDM, including a conserved type 4 secretion system and stbA (stable plasmid inheritance protein A). Two multidrug resistance gene islands were identified: The ISEcp1‑blaCMY transposition unit which contains a CMY‑6 β‑lactamase gene (blaCMY‑6) and a quaternary ammonium compound resistance gene (sugE); and the intI1‑ISCR27 accessory region, which contained a trimethoprim resistance gene (dfrA12), two aminoglycoside resistance genes (aadA2 and rmtC), a truncated quaternary ammonium compound resistance gene (qacE∆1), a sulfonamide resistance gene (sul1), the blaNDM‑1 carbapenemase and a bleomycin resistance gene (bleMBL). pHS36‑NDM shared high homology with other blaNDM‑1‑containing plasmids reported in Sweden, Italy and Japan. However, no previous international travel history was documented for the patient and her family, even to neighboring cities. Furthermore, pHS36‑NDM is of a different incompatibility group to other published blaNDM‑1‑carrying plasmids reported in China, with low homology in the surrounding structure of blaNDM‑1. The present study will facilitate the understanding of the underlying resistance and dispersal mechanism of pHS36‑NDM, and will deepen our recognition of the ongoing spread of the blaNDM‑1‑containing plasmids.201728627648
5199190.9011Whole genome sequencing uncovers a novel IND-16 metallo-β-lactamase from an extensively drug-resistant Chryseobacterium indologenes strain J31. BACKGROUND: Chryseobacterium indologenes is an emerging opportunistic pathogen in hospital-acquired infection, which is intrinsically resistant to most antimicrobial agents against gram-negative bacteria. In the purpose of extending our understanding of the resistance mechanism of C. indologenes, we sequenced and analyzed the genome of an extensively antibiotic resistant C. indologenes strain, isolated from a Chinese prostate cancer patient. We also investigated the presence of antibiotic resistance genes, particularly metallo-β-lactamase (MBL) genes, and performed a comparative genomic analysis with other Chryseobacterium species. RESULTS: 16s rRNA sequencing indicated the isolate belongs to C. indologenes. We assembled a total of 1095M bp clean-filtered reads into 171 contigs by de novo assembly. The draft genome of C. indologenes J31 consisted of 5,830,795 bp with a GC content of 36.9 %. RAST analysis revealed the genome contained 5196 coding sequences (CDSs), 28 rRNAs, 81 tRNAs and 114 pseudogenes. We detected 90 antibiotic resistance genes from different drug classes in the whole genome. Notably, a novel bla(IND) allele bla(IND-16) was identified, which shared 99 % identity with bla(IND-8) and bla(IND-10). By comparing strain J31 genome to the closely four related neighbors in the genus Chryseobacterium, we identified 2634 conserved genes, and 1449 unique genes. CONCLUSIONS: In this study, we described the whole genome sequence of C. indologenes strain J31. Numerous resistance determinants were detected in the genome and might be responsible for the extensively antibiotic resistance of this strain. Comparative genomic analysis revealed the presence of considerable strain-specific genes which would contribute to the distinctive characteristics of strain J31. Our study provides the insight of the multidrug resistance mechanism in genus Chryseobacterium.201627785154