# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 3564 | 0 | 0.9179 | Conjugation-Mediated Transfer of Antibiotic-Resistance Plasmids Between Enterobacteriaceae in the Digestive Tract of Blaberus craniifer (Blattodea: Blaberidae). Cockroaches, insects of the order Blattodea, seem to play a crucial role in the possible conjugation-mediated genetic exchanges that occur among bacteria that harbor in the cockroach intestinal tract. The gut of these insects can be thought of as an effective in vivo model for the natural transfer of antimicrobial resistance plasmids among bacteria. In our study, we evaluated the conjugation-mediated horizontal transfer of resistance genes between Escherichia coli and other microorganisms of the same Enterobacteriaceae family within the intestinal tract of Blaberus craniifer Burmeister, 1838 (Blattodea: Blaberidae). Different in vivo mating experiments were performed using E. coli RP4 harboring the RP4 plasmid carrying ampicillin, kanamycin, and tetracycline resistance genes as the donor and E. coli K12 resistant to nalidixic acid or Salmonella enterica serovar Enteritidis IMM39 resistant to streptomycin as the recipients. The RP4 plasmid was successfully transferred to both recipients, producing E. coli K12-RP4 and S. Enteritidis IMM39-RP4 transconjugants. Conjugation frequencies in vivo were similar to those previously observed in vitro. The transfer of the RP4 plasmid in all transconjugants was confirmed by small-scale plasmid isolation and agar gel electrophoresis, suggesting that the intestinal tract of cockroaches is an effective in vivo model for natural gene transfer. Our results confirm that cockroaches allow for the exchange of antimicrobial resistance plasmids among bacteria and may represent a potential reservoir for the dissemination of antibiotic-resistant bacteria in different environments. These findings are particularly significant to human health in the context of health care settings such as hospitals. | 2016 | 26875189 |
| 9868 | 1 | 0.9095 | The mosaic architecture of Aeromonas salmonicida subsp. salmonicida pAsa4 plasmid and its consequences on antibiotic resistance. Aeromonas salmonicida subsp. salmonicida, the causative agent of furunculosis in salmonids, is an issue especially because many isolates of this bacterium display antibiotic resistances, which limit treatments against the disease. Recent results suggested the possible existence of alternative forms of pAsa4, a large plasmid found in A. salmonicida subsp. salmonicida and bearing multiple antibiotic resistance genes. The present study reveals the existence of two newly detected pAsa4 variants, pAsa4b and pAsa4c. We present the extensive characterization of the genomic architecture, the mobile genetic elements and the antimicrobial resistance genes of these plasmids in addition to the reference pAsa4 from the strain A449. The analysis showed differences between the three architectures with consequences on the content of resistance genes. The genomic plasticity of the three pAsa4 variants could be partially explained by the action of mobile genetic elements like insertion sequences. Eight additional isolates from Canada and Europe that bore similar antibiotic resistance patterns as pAsa4-bearing strains were genotyped and specific pAsa4 variants could be attributed to phenotypic profiles. pAsa4 and pAsa4c were found in Europe, while pAsa4b was found in Canada. In accordance with their content in conjugative transfer genes, only pAsa4b and pAsa4c can be transferred by conjugation in Escherichia coli. The plasticity of pAsa4 variants related to the acquisition of antibiotic resistance indicates that these plasmids may pose a threat in terms of the dissemination of antimicrobial-resistant A. salmonicida subsp. salmonicida bacteria. | 2016 | 27812409 |
| 359 | 2 | 0.9093 | Construction of shuttle cloning vectors for Bacteroides fragilis and use in assaying foreign tetracycline resistance gene expression. Shuttle vectors capable of replication in both Escherichia coli and Bacteroides fragilis have been developed. Conjugal transfer of these plasmids from E. coli to B. fragilis is facilitated by inclusion of the origin of transfer of the IncP plasmid RK2. The vectors pDK1 and pDK2 provide unique sites for cloning selectable markers in Bacteroides. pOA10 is a cosmid vector containing the replication region of pCP1 necessary for maintenance in Bacteroides. pDK3, pDK4.1, and pDK4.2 contain the Bacteroides clindamycin resistance gene allowing selection and maintenance in B. fragilis of plasmids containing inserted DNA fragments. pDK3 was used to test the expression in B. fragilis of five foreign tetracycline resistance (TcR) genes. The tetA, -B, and -C markers from facultative gram-negative bacteria, as well as a TcR determinant from Clostridium perfringens, did not express TcR in B. fragilis. The tetM gene, originally described in streptococci, encoded a small but reproducible increase of TcR in Bacteroides. These studies demonstrate the utility of shuttle vectors for introducing cloned genes into Bacteroides and underscore the differences in gene expression in these anaerobes. | 1988 | 3071818 |
| 536 | 3 | 0.9090 | Thymidylate synthase gene from Lactococcus lactis as a genetic marker: an alternative to antibiotic resistance genes. The potential of the thymidylate synthase thyA gene cloned from Lactococcus lactis subsp. lactis as a possible alternative selectable marker gene to antibiotic resistance markers has been examined. The thyA mutation is a recessive lethal one; thyA mutants cannot survive in environments containing low amounts of thymidine or thymine (such as Luria-Bertani medium) unless complemented by the thyA gene. The cloned thyA gene was strongly expressed in L. lactis subsp. lactis, Escherichia coli, Rhizobium meliloti, and a fluorescent Pseudomonas strain. In addition, when fused to a promoterless enteric lac operon, the thyA gene drove expression of the lac genes in a number of gram-negative bacteria. In transformation experiments with thyA mutants of E. coli and conjugation experiments with thyA mutants of R. meliloti, the lactococcal thyA gene permitted selection of transformants and transconjugants with the same efficiency as did genes for resistance to ampicillin, chloramphenicol, or tetracycline. Starting from the broad-host-range plasmid pGD500, a plasmid, designated pPR602, was constructed which is completely free of antibiotic resistance genes and has the lactococcal thyA gene fused to a promoterless lac operon. This plasmid will permit growth of thyA mutant strains in the absence of thymidine or thymine and has a number of unique restriction sites which can be used for cloning. | 1990 | 2117883 |
| 6363 | 4 | 0.9089 | The effect of tetronasin and monensin on fermentation, microbial numbers and the development of ionophore-resistant bacteria in the rumen. The Gram-negative rumen bacteria Fibrobacter succinogenes S85, Prevotella ruminicola M384 and Veillonella parvula L59 were grown in media containing successively increasing concentrations of the ionophores, monensin and tetronasin. All three species became more resistant to the ionophore with which they were grown. Increased resistance to one ionophore caused increased resistance to the other, and cross-resistance to another ionophore--lasalocid--and an antibiotic--avoparcin. Recovery of tetronasin-resistant bacteria from the rumen of monensin-fed sheep increased and vice versa, indicating that similar cross-resistance occurred in vivo. | 1993 | 8407673 |
| 415 | 5 | 0.9085 | Mobilization of plasmid-borne drug resistance determinants for transfer from Pseudomonas aeruginosa to Escherichia coli. RSU2, a plasmid transmissible between strains of P. aeruginosa but not to Escherichia coli can be mobilized by R751. Conjugatants receive a single plasmid composed of DNA from both R751 and RSU2 which has the compatibility properties of a member of group P (like R751). Study of this fusion plasmid suggests that the failure of RSU2 to transfer into enterobacteria is due to an inability to replicate in these bacteria. The fusion plasmid replicates using the genes of R751. | 1975 | 127114 |
| 3565 | 6 | 0.9085 | Conjugative RP4 Plasmid-Mediated Transfer of Antibiotic Resistance Genes to Commensal and Multidrug-Resistant Enteric Bacteria In Vitro. Many antibiotic-resistant bacteria carry resistance genes on conjugative plasmids that are transferable to commensals and pathogens. We determined the ability of multiple enteric bacteria to acquire and retransfer a broad-host-range plasmid RP4. We used human-derived commensal Escherichia coli LM715-1 carrying a chromosomal red fluorescent protein gene and green fluorescent protein (GFP)-labeled broad-host-range RP4 plasmid with ampR, tetR, and kanR in in vitro matings to rifampicin-resistant recipients, including Escherichia coli MG1655, Dec5α, Vibrio cholerae, Pseudomonas putida, Pseudomonas aeruginosa, Klebsiella pneumoniae, Citrobacter rodentium, and Salmonella Typhimurium. Transconjugants were quantified on selective media and confirmed using fluorescence microscopy and PCR for the GFP gene. The plasmid was transferred from E. coli LM715-1 to all tested recipients except P. aeruginosa. Transfer frequencies differed between specific donor-recipient pairings (10(-2) to 10(-8)). Secondary retransfer of plasmid from transconjugants to E. coli LM715-1 occurred at frequencies from 10(-2) to 10(-7). A serial passage plasmid persistence assay showed plasmid loss over time in the absence of antibiotics, indicating that the plasmid imposed a fitness cost to its host, although some plasmid-bearing cells persisted for at least ten transfers. Thus, the RP4 plasmid can transfer to multiple clinically relevant bacterial species without antibiotic selection pressure. | 2023 | 36677486 |
| 355 | 7 | 0.9083 | Evolution of multiple-antibiotic-resistance plasmids mediated by transposable plasmid deoxyribonucleic acid sequences. Two plasmid deoxyribonucleic acid sequences mediating multiple antibiotic resistance transposed in vivo between coexisting plasmids in clinical isolates of Serratia marcescens. This event resulted in the evolution of a transferable multiresistance plasmid. Both sequences, designated in Tn1699 and Tn1700, were flanked by inverted deoxyribonucleic acid repetitions and could transpose between replicons independently of the Excherichia coli recA gene function. Tn1699 and Tn1700 mediated ampicillin, carbenicillin, kanamycin, and gentamicin resistance but differed in the type of gentamicin-acetyltransferase enzymes that they encoded. The structural genes for these enzymes share a great deal of polynucleotide sequence similarity despite their phenotypic differences. The transposition of Tn1699 and Tn1700 to coresident transferable plasmids has contributed to the dissemination of antibiotic resistance among other gram-negative bacteria. These organisms have recently caused nosocomial infections in epidemic proportions. | 1979 | 387747 |
| 3566 | 8 | 0.9079 | Transfer of antibiotic multiresistant plasmid RP4 from escherichia coli to activated sludge bacteria. In situ transfer of a self-transmissible, antibiotic-multiresistant plasmid RP4 from a laboratory Escherichia coli strain C600 to indigenous activated sludge bacteria was investigated using filter mating. The transfer frequency of RP4 from the donor E. coli to the bacteria that was sampled from two wastewater treatment plants was 5.1x10(-2) to 7.5x10(-1) and 4.6x10(-3) to 1.3x10(-2)/potential recipient. The isolated transconjugants showed resistance to Ap, Km, and Tc and the presence of a plasmid with a similar size to RP4. The traG gene on RP4 was also detected from all transconjugants. Reverse-transfer experiments from the transconjugants to E. coli HB101 indicated that RP4 maintained self-transmissibility in the transconjugants. The transconjugant strains were dominant bacteria in activated sludge including Pseudomonas fluorescens, P. putida, and Ochrobactrum anthropi and minor populations of enteric bacterial strains including Citrobacter freundii, E. coli, Enterobacter cloacae, E. asburiae, and Klebsiella pneumoniae ssp. pneumoniae. The transconjugant strains K. pneumoniae ssp. pneumonia, E. cloacae, and E. asburiae had several naturally occurring plasmids. These results suggest that in situ transfer of plasmids and the exchange of antibiotic-resistant genes can occur between released and indigenous bacteria in activated sludge. | 2008 | 18930008 |
| 537 | 9 | 0.9079 | Omegon-Km: a transposable element designed for in vivo insertional mutagenesis and cloning of genes in gram-negative bacteria. To combine the features of the omega interposons with the advantages of in vivo transposition mutagenesis, we have constructed an artificial transposon, called Omegon-Km. The Omegon-Km transposon is carried on the plasmid pJFF350 which can be conjugally mobilized into a broad range of Gram-negative bacteria. Omegon-Km is flanked, in inverted orientation, by synthetic 28-bp repeats derived from the ends of IS1. In addition, each end of Omegon-Km has the very efficient transcription and translation terminators of the omega interposon. Internally, Omegon-Km carries the selectable kanamycin (Km)-neomycin resistance gene (alph A) which is expressed well in many Gram-negative bacteria. The IS1 transposition functions are located on the donor plasmid but external to Omegon-Km. Thus, insertions of Omegon-Km are very stable because they lack the capacity for further transposition. Omegon-Km mutagenesis is performed by conjugal transfer of pJFF350 from Escherichia coli into any Gram-negative recipient strain in which this plasmid is unable to replicate. Those cells which have had a transposition event are selected by their resistance to Km. Very high frequencies of Omegon-Km transposition were observed in Pseudomonas putida. Preliminary experiments with other Gram-negative soil and water bacteria (Rhizobium leguminosarum, Paracoccus denitrificans) yielded mutants at reasonable levels. The presence of an E. coli-specific origin of replication (ori) within Omegon-Km allows the rapid and easy cloning, in E. coli, of the nucleotide sequences flanking the site of the transposition event. | 1989 | 2546859 |
| 6788 | 10 | 0.9079 | Release and Constancy of an Antibiotic Resistance Gene in Seawater under Grazing Stress by Ciliates and Heterotrophic Nanoflagellates. Extracellular DNA (exDNA) is released from bacterial cells through various processes. The antibiotic resistance genes (ARGs) coded on exDNA may be horizontally transferred among bacterial communities by natural transformation. We quantitated the released/leaked tetracycline resistance gene, tet(M) over time under grazing stress by ciliates and heterotrophic nanoflagellates (HNFs), and found that extracellular tet(M) (ex-tetM) increased with bacterial grazing. Separate microcosms containing tet(M)-possessing bacteria with ciliates or HNFs were prepared. The copy number of ex-tetM in seawater in the ciliate microcosm rapidly increased until 3 d after the incubation, whereas that in the HNF microcosm showed a slower increase until 20 d. The copy number of ex-tetM was stable in both cases throughout the incubation period, suggesting that extracellular ARGs are preserved in the environment, even in the presence of grazers. Additionally, ARGs in bacterial cells were constant in the presence of grazers. These results suggest that ARGs are not rapidly extinguished in a marine environment under grazing stress. | 2017 | 28592722 |
| 394 | 11 | 0.9078 | Introduction of bacteriophage Mu into bacteria of various genera and intergeneric gene transfer by RP4::Mu. The host range of coliphage Mu was greatly expanded to various genera of gram-negative bacteria by using the hybrid plasmic RP4::Mu cts, which is temperature sensitive and which confers resistance to ampicillin, kanamycin, and tetracycline. These drug resistance genes were transferred from Escherichia coli to members of the general Klebsiella, Enterobacter, Citrobacter, Salmonella, Proteus, Erwinia, Serratia, Alcaligenes, Agrobacterium, Rhizobium, Pseudomonas, Acetobacter, and Bacillus. Mu phage was produced by thermal induction from the lysogens of all these drug-resistant bacteria except Bacillus. Mu phage and RP4 or the RP4::Mu plasmid were used to create intergeneric recombinant strains by transfer of some genes, including the arylsulfatase gene, between Klebsiella aerogenes and E. coli. Thus, genetic analysis and intergeneric gene transfer are possible in these RP4::Mu-sensitive bacteria. | 1981 | 6450749 |
| 430 | 12 | 0.9078 | Cloning and characterization of EcoRI and HindIII restriction endonuclease-generated fragments of antibiotic resistance plasmids R6-5 and R6. DNA fragments generated by the EcoRI of HindIII endonucleases from the low copy number antibiotic resistance plasmids R6 and R6-5 were separately cloned using the high copy number ColE1 or pML21 plasmid vectors and the insertional inactivation procedure. The hybrid plasmids that were obtained were used to determine the location of the EcoRI and HindIII cleavage sites on the parent plasmid genomes by means of electron microscope heteroduplex analysis and agarose gel electrophoresis. Ultracentrifugation of the cloned fragments in caesium chloride gradients localized the high buoyant density regions of R6-5 to fragments that carry the genes for resistance to streptomycin-spectinomycin, sulfonamide, and mercury and a low buoyant density region to fragments that carry the tetracycline resistance determinant. Functional analysis of hybrid plasmids localized a number of plasmid properties such as resistances to antibiotics and mercury and several replication functions to specific regions of the R6-5 genome. Precise localisation of the genes for resistance to chloramphenicol, kanamycin, fusidic acid and tetracycline was possible due to the presence of identified restriction endonuclease cleavage sites within these determinants. Only one region competent for autonomous replication was identified on the R6-5 plasmid genome and this was localized to EcoRI fragment 2 and HindIII fragment 1. However, two additional regions of replication activity designated RepB and RepC, themselves incapable of autonomous replication but capable supporting replication of a linked ColE1 plasmid in polA- bacteria, were also identified. | 1978 | 672900 |
| 429 | 13 | 0.9077 | An integrative vector exploiting the transposition properties of Tn1545 for insertional mutagenesis and cloning of genes from gram-positive bacteria. We have constructed and used an integrative vector, pAT112, that takes advantage of the transposition properties (integration and excision) of transposon Tn1545. This 4.9-kb plasmid is composed of: (i) the replication origin of pACYC184; (ii) the attachment site (att) of Tn1545; (iii) erythromycin-and kanamycin-resistance-encoding genes for selection in Gram- and Gram+ bacteria; and (iv) the transfer origin of IncP plasmid RK2, which allows mobilization of the vector from Escherichia coli to various Gram+ recipients. Integration of pAT112 requires the presence of the transposon-encoded integrase, Int-Tn, in the new host. This vector retains the insertion specificity of the parental element Tn1545 and utilises it to carry out insertional mutagenesis, as evaluated in Enterococcus faecalis. Since pAT112 contains the pACYC184 replicon and lacks most of the restriction sites that are commonly used for molecular cloning, a gene from a Gram+ bacterium disrupted with this vector can be recovered in E. coli by cleavage of genomic DNA, intramolecular ligation and transformation. Regeneration of the gene, by excision of pAT112, can be obtained in an E. coli strain expressing the excisionase and integrase of Tn1545. The functionality of this system was illustrated by characterization of an IS30-like structure in the chromosome of En. faecalis. Derivatives pAT113 and pAT114 contain ten unique cloning sites that allow screening of recombinants having DNA inserts by alpha-complementation in E. coli carrying the delta M15 deletion of lacZ alpha. These vectors are useful to clone and introduce foreign genes into the genomes of Gram+ bacteria. | 1991 | 1657722 |
| 3716 | 14 | 0.9076 | Transfer of antibiotic resistance genes between Enterococcus faecalis strains in filter feeding zooplankton Daphnia magna and Daphnia pulex. Antibiotic resistant bacteria from faecal pollution sources are pervasive in aquatic environments. A facilitating role for the emergence of waterborne, multi-drug resistant bacterial pathogens has been attributed to biofiltration but had not yet been substantiated. This study investigated the effect of filtration and gut passage in Daphnia spp. on conjugal transfer of resistance genes in Enterococcus faecalis. In vivo conjugation experiments involved a vancomycin-resistant donor strain bearing a plasmid-borne vanA resistance gene, and two vancomycin-susceptible and rifampicin-resistant recipient strains in the presence of Daphnia magna or Daphnia pulex. Results showed successful transfer of the vanA resistance gene from donor to recipient; gene identity was confirmed by PCR and DNA sequencing. There was no significant difference in the number of transconjugants recovered from D. magna and D. pulex. However, transconjugant numbers differed by one order of magnitude between recipient strains. Transconjugant numbers from D. magna were also significantly different between treatments with ingestion of individual phytoplankton species before filtration of bacteria. The highest transfer efficiency calculated from excreted transconjugants was 2.5 × 10(-6). This proof of concept for facilitation of horizontal gene transfer by a filter feeding organism provides evidence that Daphnia can disseminate antibiotic resistant transconjugants in the environment. | 2019 | 31096330 |
| 3652 | 15 | 0.9076 | Distribution of Transferable Antibiotic Resistance Genes in Laboratory-Reared Edible Mealworms (Tenebrio molitor L.). In the present study, the distribution of antibiotic resistance genes in laboratory-reared fresh mealworm larvae (Tenebrio molitor L.), their feeding substrates (carrots and wheatmeal), and frass was assessed. Microbial counts on selective media added with antibiotics highlighted the presence of lactic acid bacteria resistant to ampicillin and vancomycin and, more specifically, enterococci resistant to the latter antibiotic. Moreover, staphylococci resistant to gentamicin, erythromycin, tetracycline, and vancomycin were detected. Enterobacteriaceae resistant to ampicillin and gentamicin were also found, together with Pseudomonadaceae resistant to gentamicin. Some of the genes coding for resistance to macrolide-lincosamide-streptogramin B (MLS(B)) [erm(A), erm(C)], vancomycin [vanA, vanB], tetracycline [tet(O)], and β-lactams [mecA and blaZ] were absent in all of the samples. For the feeding substrates, organic wheatmeal was positive for tet(S) and tet(K), whereas no AR genes were detected in organic carrots. The genes tet(M), tet(K), and tet(S) were detected in both mealworms and frass, whereas gene aac-aph, coding for resistance to amynoglicosides was exclusively detected in frass. No residues for any of the 64 antibiotics belonging to 10 different drug classes were found in either the organic wheatmeal or carrots. Based on the overall results, the contribution of feed to the occurrence of antibiotic resistance (AR) genes and/or antibiotic-resistant microorganisms in mealworm larvae was hypothesized together with vertical transmission via insect egg smearing. | 2018 | 30510544 |
| 361 | 16 | 0.9076 | Plasmid transfer from Escherichia coli to Bacteroides fragilis: differential expression of antibiotic resistance phenotypes. A unique shuttle plasmid, pDP1, has been constructed to mediate gene transfer between Escherichia coli and the Gram-negative anaerobe Bacteroides fragilis. pDP1 contains the pBR322 replicon and the Bacteroides clindamycin resistance plasmid pCP1 linked to the transfer origin of the broad host range plasmid RK2. pDP1 can be transferred from E. coli to B. fragilis by the RK2 conjugation system even though RK2 itself is not maintained in the Bacteroides recipients. The antibiotic resistance and replication functions of pDP1 have been mapped by deletion analysis, and a 5-kilobase portion of the plasmid has been identified as the essential region for maintenance in Bacteroides. Comparison of the resistance conferred by pDP1 on E. coli and B. fragilis shows that antibiotic resistance genes are expressed differently in aerobic and anaerobic bacteria. These results document the feasibility of gene transfer from E. coli to B. fragilis and demonstrate the usefulness of this conjugation system to study genetic structure and expression in Bacteroides. | 1984 | 6095273 |
| 3061 | 17 | 0.9075 | Tetracycline-resistance encoding plasmids from Paenibacillus larvae, the causal agent of American foulbrood disease, isolated from commercial honeys. Paenibacillus larvae, the causal agent of American foulbrood disease in honeybees, acquires tetracycline-resistance via native plasmids carrying known tetracycline-resistance determinants. From three P. larvae tetracycline-resistant strains isolated from honeys, 5-kb-circular plasmids with almost identical sequences, designated pPL373 in strain PL373, pPL374 in strain PL374, and pPL395 in strain PL395, were isolated. These plasmids were highly similar (99%) to small tetracycline-encoding plasmids (pMA67, pBHS24, pBSDMV46A, pDMV2, pSU1, pAST4, and pLS55) that replicate by the rolling circle mechanism. Nucleotide sequences comparisons showed that pPL373, pPL374, and pPL395 mainly differed from the previously reported P. larvae plasmid pMA67 in the oriT region and mob genes. These differences suggest alternative mobilization and/or conjugation capacities. Plasmids pPL373, pPL374, and pPL395 were individually transferred by electroporation and stably maintained in tetracycline-susceptible P. larvae NRRL B-14154, in which they autonomously replicated. The presence of nearly identical plasmids in five different genera of gram-positive bacteria, i.e., Bhargavaea, Bacillus, Lactobacillus, Paenibacillus, and Sporosarcina, inhabiting diverse ecological niches provides further evidence of the genetic transfer of tetracycline resistance among environmental bacteria from soils, food, and marine habitats and from pathogenic bacteria such as P. larvae. | 2014 | 25296446 |
| 5991 | 18 | 0.9075 | Transferable plasmid-mediated antibiotic resistance in Listeria monocytogenes. A strain of Listeria monocytogenes, isolated from a patient with meningoencephalitis, was resistant to chloramphenicol, erythromycin, streptomycin, and tetracycline. The genes conferring resistance to these antibiotics were carried by a 37-kb plasmid, pIP811, that was self-transferable to other L monocytogenes cells, to enterococci-streptococci, and to Staphylococcus aureus. The efficacy of transfer and the stability of pIP811 were higher in enterococci-streptococci than in the other gram-positive bacteria. As indicated by nucleic acid hybridisation, the genes in pIP811 conferring resistance to chloramphenicol, erythromycin, and streptomycin were closely related to plasmid-borne determinants that are common in enterococci-streptococci. Plasmid pIP811 shared extensive sequence homology with pAM beta 1, the prototype broad host range resistance plasmid in these two groups of gram-positive cocci. These results suggest that emergence of multiple antibiotic resistance in Listeria spp is due to acquisition of a replicon originating in enterococci-streptococci. The dissemination of resistance to other strains of L monocytogenes is likely. | 1990 | 1972210 |
| 3055 | 19 | 0.9075 | Tn1545: a conjugative shuttle transposon. Tn1545, from Streptococcus pneumoniae BM4200, confers resistance to kanamycin (aphA-3), erythromycin (ermAM) and tetracycline (tetM). The 25.3 kb element is self-transferable to various Gram-positive bacterial genera where it transposes. Tn1545 was cloned in its entirety in the recombination deficient Escherichia coli HB101 where it was unstable. The three resistance genes aphA-3, ermAM and tetM were expressed but were not transferable to other E. coli cells. Tn1545 transposed from the hybrid plasmid to multiple sites of the chromosome of its new host. The element re-transposed, at a frequency of 5 X 10(-9), from the chromosome to various sites of a conjugative plasmid where it could be lost by apparently clean excision. The element transformed and transposed to the chromosome of Bacillus subtilis. The properties of the conjugative shuttle transposon Tn1545 may account for the recent emergence of genes from Gram-positive bacteria in Gram-negative organisms. | 1987 | 3035335 |