Gram-positive merA gene in gram-negative oral and urine bacteria. - Related Documents




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585001.0000Gram-positive merA gene in gram-negative oral and urine bacteria. Clinical mercury resistant (Hg(r)) Gram-negative bacteria carrying Gram-positive mercury reductase (merA)-like genes were characterized using DNA-DNA hybridization, PCR and sequencing. A PCR assay was developed which discriminated between the merA genes related to Staphylococcus and those related to the Bacillus/Streptococcus merA genes by the difference in size of the PCR product. DNA sequence analysis correlated with the PCR assay. The merA genes from Acinetobacter junii, Enterobacter cloacae and Escherichia coli were sequenced and shared 98-99% identical nucleotide (nt) and 99.6-100% amino acid identity with the Staphylococcus aureus MerA protein. A fourth merA gene, from Pantoeae agglomerans, was partially sequenced (60%) and had 99% identical nt and 100% amino acid identity with the Streptococcus oralis MerA protein. All the Hg(r) Gram-negative bacteria transferred their Gram-positive merA genes to a Gram-positive Enterococcus faecalis recipient with the resulting transconjugants expressing mercury resistance. These Gram-positive merA genes join Gram-positive tetracycline resistance and Gram-positive macrolide resistance genes in their association with mobile elements which are able to transfer and express in Gram-negative bacteria.200415358427
585110.9998Arsenic resistance determinants from environmental bacteria. Arsenic resistance determinants from 42 environmental bacterial isolates (32 Gram negative) were analyzed by DNA: DNA hybridization using probes derived from Escherichia coli and Staphylococcus plasmid or chromosomal arsenic resistance (ars) genes. In colony hybridization assays, 11 and 1 Gram negative strains hybridized with the E. coli chromosome and plasmid probes, respectively. No hybridization was detected using a probe containing only the arsA (ATPase) gene from E. coli plasmid or with a Staphylococcus plasmid ars probe. From Southern hybridization tests of some of the positive strains it was concluded that homology to ars chromosomal genes occurred within chromosome regions, except in an E. coli isolate where hybridization occurred in both the chromosome and a 130-kb plasmid. Our results show that DNA sequences homologous to E. coli ars chromosomal genes are commonly present in the chromosomes of environmental arsenic-resistant Gram negative isolates.199810932734
585220.9998A novel transposon, Tn6009, composed of a Tn916 element linked with a Staphylococcus aureus mer operon. OBJECTIVES: The aim of this study was to characterize a novel conjugative transposon Tn6009 composed of a Tn916 linked to a Staphylococcus aureus mer operon in representative Gram-positive and Gram-negative bacteria isolated in Nigeria and Portugal. METHODS: Eighty-three Gram-positive and 34 Gram-negative bacteria were screened for the presence of the Tn6009 using DNA-DNA hybridization, PCR, hybridization of PCR products, sequencing and mating experiments by established procedures. RESULTS: Forty-three oral and 23 urine Gram-negative and Gram-positive isolates carried the Tn6009. Sequencing was performed to verify the direct linkage between the mer resistance genes and the tet(M) gene. A Nigerian Klebsiella pneumoniae, isolated from a urinary tract infection patient, and one commensal isolate from each of the other Tn6009-positive genera, Serratia liquefaciens, Pseudomonas sp., Enterococcus sp. and Streptococcus sp. isolated from the oral and urine samples of healthy Portuguese children, were able to act as donors and conjugally transfer the Tn6009 to the Enterococcus faecalis JH2-2 recipient, resulting in tetracycline- and mercury-resistant E. faecalis transconjugants. CONCLUSIONS: This study reports a novel non-composite conjugative transposon Tn6009 containing a Tn916 element linked to an S. aureus mer operon carrying genes coding for inorganic mercury resistance (merA), an organic mercury resistance (merB), a regulatory protein (merR) and a mercury transporter (merT). This transposon was identified in 66 isolates from two Gram-positive and three Gram-negative genera and is the first transposon in the Tn916 family to carry the Gram-positive mer genes directly linked to the tet(M) gene.200818583328
585430.9997Discovery of a gene conferring multiple-aminoglycoside resistance in Escherichia coli. Bovine-origin Escherichia coli isolates were tested for resistance phenotypes using a disk diffusion assay and for resistance genotypes using a DNA microarray. An isolate with gentamicin and amikacin resistance but with no corresponding genes detected yielded a 1,056-bp DNA sequence with the closest homologues for its inferred protein sequence among a family of 16S rRNA methyltransferase enzymes. These enzymes confer high-level aminoglycoside resistance and have only recently been described in Gram-negative bacteria.201020368404
585340.9996Identification of the tet(B) resistance gene in Streptococcus suis. The tetracycline resistance gene, tet(B), has been described previously in gram negative bacteria. In this study tet(B) was detected in plasmid extracts from 17/111 (15%) Streptococcus suis isolates from diseased pigs, representing the first report of this resistance gene in gram positive bacteria.201120696603
584950.9996Characterisation and molecular cloning of the novel macrolide-streptogramin B resistance determinant from Staphylococcus epidermidis. A total of 110 staphylococcal isolates from human skin were found to express a novel type of erythromycin resistance. The bacteria were resistant to 14-membered ring macrolides (MIC 32-128 mg/l) but were sensitive to 16-membered ring macrolides and lincosamides. Resistance to type B streptogramins was inducible by erythromycin. A similar phenotype, designated MS resistance, was previously described in clinical isolates of coagulase-negative staphylococci from the USA. In the UK, MS resistance is widely distributed in coagulase-negative staphylococci but was not detected in 100 erythromycin resistant clinical isolates of Staphylococcus aureus. Tests for susceptibility to a further 16 antibiotics failed to reveal any other selectable marker associated with the MS phenotype. Plasmid pattern analysis of 48 MS isolates showed considerable variability between strains and no common locus for the resistance determinant. In one strain of S. epidermidis co-resistance to tetracycline, penicillin and erythromycin (MS) was associated with a 31.5 kb plasmid, pUL5050 which replicated and expressed all three resistances when transformed into S. aureus RN4220. The MS resistance determinant was localised to a 1.9 kb fragment which was cloned on to the high-copy-number vector, pSK265. A constitutive mutant of S. aureus RN4220 containing the 1.9 kb fragment remained sensitive to clindamycin. This observation, together with the concentration-dependent induction (optimum 5 mg/l of erythromycin) of virginiamycin S resistance suggests that the MS phenotype is not due to altered expression of MLS resistance determinants (erm genes) but probably occurs via a different mechanism.19892559912
597060.9996DNA microarray for detection of macrolide resistance genes. A DNA microarray was developed to detect bacterial genes conferring resistance to macrolides and related antibiotics. A database containing 65 nonredundant genes selected from publicly available DNA sequences was constructed and used to design 100 oligonucleotide probes that could specifically detect and discriminate all 65 genes. Probes were spotted on a glass slide, and the array was reacted with DNA templates extracted from 20 reference strains of eight different bacterial species (Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Staphylococcus haemolyticus, Escherichia coli, and Bacteroides fragilis) known to harbor 29 different macrolide resistance genes. Hybridization results showed that probes reacted with, and only with, the expected DNA templates and allowed discovery of three unexpected genes, including msr(SA) in B. fragilis, an efflux gene that has not yet been described for gram-negative bacteria.200616723563
586170.9996Distribution of genes conferring combined resistance to tetracycline and minocycline among group B streptococcal isolates from humans and various animals. Forty-nine tetracycline and minocycline resistant streptococci of serological group B isolated from humans, cattle, pigs and nutrias were investigated for the presence of genes conferring this combined resistance. Southern blot hybridization of EcoRI-digested chromosomal DNA of the bacteria revealed for 39 of the cultures a hybridization signal with tet(M), for four of the cultures a hybridization signal with tet(O) and for none of the cultures a hybridization signal with the tet(Q) gene probe. The restriction endonuclease digested and blotted DNA of six tetracycline and minocycline resistant group B streptococci did not hybridize with any of the available gene probes. The tet(M) gene probes recognized complementary sequences of EcoRI fragments of approximately 10.5 kb and 21.5 kb, the tet(O) gene probe hybridized with fragments of approximately 19 kb. The hybridization of the tet(M) gene probe in two different patterns appeared to be related to the origin of the cultures.19947727901
585580.9996Plasmid-encoded resistance to arsenic compounds in Gram-negative bacteria isolated from a hospital environment in Venezuela. Resistance to arsenic compounds was examined among amikacin resistant Gram-negative bacteria isolate from a hospital environment. Arsenite resistance (Ars(r)) was found in a high proportion of isolates ( >60%) being frequently associated with resistance to tellurite (40%), and to other antimicrobial agents. Ars determinants (27%) were found to be transferable to E. coli K12 strains from which large plasmid DNA molecules were isolated and characterized by agarose gel electrophoresis. Plasmids were identified by both classical incompatibility tests, and by replicon typing using DNA specific probes. Most of the amikacin-arsenite (Ak-Ars) conjugative plasmids belong to the H incompatibility group. These results suggest that Ak-Ars resistance linked to IncH plasmids is wide spread in Gram-negative bacteria.199718611788
305290.9996Expression of antibiotic resistance genes from Escherichia coli in Bacillus subtilis. Bifunctional recombinant plasmids were constructed, comprised of the E. coli vectors pBR322, pBR325 and pACYC184 and different plasmids from Gram-positive bacteria, e.g. pBSU161-1 of B. subtilis and pUB110 and pC221 of S. aureus. The beta-lactamase (bla) gene and the chloramphenicol acetyltransferase (cat) gene from the E. coli plasmids were not transcribed and therefore not expressed in B. subtilis. However, tetracycline resistance from the E. coli plasmids was expressed in B. subtilis. Transcription of the tetracycline resistance gene(s) started in B. subtilis at or near the original E. coli promoter, the sequence of which is almost identical with the sequence recognized by sigma 55 of B. subtilis RNA polymerase.19836410152
2081100.9996Distribution of the antiseptic-resistance gene qacE delta 1 in gram-positive bacteria. The distribution of the antiseptic-resistance genes qacE and qacE delta 1, originally isolated from Gram-negative bacteria, was studied in a large number of Gram-positive bacteria by a method that included the polymerase chain reaction. A total of 151 strains of Staphylococcus and Enterococcus, isolated from clinical sources and obtained from the Japanese Collection of Microorganisms, was used in this analysis. We found the qacE delta 1 gene in 36 of 103 strains of Staphylococcus and in nine of 48 strains of Enterococcus. All of the strains in which we detected the qacE delta 1 gene were clinical isolates. The qacE gene was not detected in any of the strains examined in this study. The nucleotide sequences of the qacE delta 1 genes from the strains of Staphylococcus and Enterococcus were identical to that of the gene located on integron InC in Pseudomonas aeruginosa. These results indicate that the antiseptic-resistance gene qacE delta 1 is present in Gram-positive, as well as Gram-negative, bacteria.19989742702
5848110.9996Plasmid and chromosomal basis of tolerance to cadmium and resistance to antibiotics in normal bovine duodenal bacterial flora. Cadmium (Cd) tolerance and antibiotic resistance was studied in duodenal flora of 20 normal bovine samples. Twelve bacterial isolates (5 Staphylococcus spp, 4 Enterococcus faecalis, 2 Bacillus spp, and a Pseudomonas sp) were grown in Luria broth containing 0.05 to 0.8 mM of cadmium chloride (CdCl). All isolates displayed multiple antibiotic resistance, with 2 Enterococcus strains and Pseudomonas pickettii demonstrating resistance to 12/17 antibiotics tested. With the exception of Staphylococcus sp, all contained plasmid DNA. Curing to remove plasmid DNA determined if Cd tolerance and/or antibiotic resistance was plasmid or chromosomally mediated. None of the bacteria became sensitive to CdCl after curing, suggesting that tolerance was not plasmid-mediated. Six bacteria became sensitive to antibiotics after curing indicating that antibiotic2 resistance was plasmid mediated. Two of these bacteria became sensitive to multiple antibiotics; a Staphylococcus sp became sensitive to ampicillin, ceftiofur and cephalothin, and a Enterococcus strain became sensitive to neomycin, oxacillin, and tiamulin. All of the isolates were probed for the presence of known Cd-resistance genes (cadA, cadC, and cadD). DNA-DNA hybridization revealed cadA- and cadC-related sequences in chromosomal DNA of a Staphylococcus sp, an Enterococcus strain, and in plasmid DNA of another Staphylococcus sp. No cadD-related sequences were detected in any of the 12 isolates even under reduced stringency of hybridization.200111383651
5963120.9996Expression of the mphB gene for macrolide 2'-phosphotransferase II from Escherichia coli in Staphylococcus aureus. The genes mphA and mphB encode macrolide 2'-phosphotransferases I and II, respectively, and they confer resistance to macrolide antibiotics in Escherichia coli. To study the expression of these genes in Gram-positive bacteria, we constructed recombinant plasmids that consisted of an mph gene and the pUB110 vector in Bacillus subtilis. When these plasmids were introduced into Staphylococcus aureus, the mphB gene was active and macrolide 2'-phosphotransferase II was produced. The gene endowed S. aureus with high-level resistance to spiramycin, a macrolide antibiotic with a 16-membered ring. Moreover, transcription of the mphB gene in S. aureus began at the promoter that was active in E. coli.19989503630
3043130.9996The role of insertions, deletions, and substitutions in the evolution of R6 related plasmids encoding aminoglycoside transferase ANT-(2"). In 7% of gram-negative bacteria resistance to gentamicin is mainly mediated by plasmid-encoded aminoglycoside transferase ANT-(2"). The genome organization of 15 aadB plasmids (42-110 kb) was analyzed by restriction and hybridization techniques. They appeared to be IncFII-like replicons but were distinct from R6 by virtue of small substitutions in the transfer region. Aminoglycoside resistance genes aadB and aadA were located on Tn21 related elements. Only one of them was able to transpose its resistance genes mer sul aadA and aadB ( Tn4000 ), the other elements were naturally occurring defective transposons. In some of these structures deletions were identified at the termini, at sul, aadA , mer or transposition function--insertions adjacent to aadA or mer. The mode of these rearrangements and their site-specificity were considered with respect to the evolution of the Tn21 transposon family.19846328217
5953140.9996CAT III chloramphenicol resistance in Pasteurella haemolytica and Pasteurella multocida isolated from calves. Chloramphenicol, which had been used extensively for antimicrobial veterinary therapy, was prohibited in Europe in 1994. Soon after it became available, resistance to this drug was detected, generally conferred by plasmids encoding inactivating enzymes, the chloramphenicol acetyltransferases (CAT), in Gram-negative as well as in Gram-positive bacteria. In the last few years, resistance to antibiotics emerged in Pasteurella strains from breeding herds and this evolution was followed by a national surveillance network. Chloramphenicol-resistance was more recently detected in multiresistant strains. We studied 25 strains of Pasteurella, selected for their resistance to chloramphenicol. Production of a CAT was demonstrated in all these strains. PCR amplification indicated that the CAT produced was of type III for 23 of them. In these strains, chloramphenicol-resistance was mediated by plasmids of about 5.1 kb. Southern blots on restriction fragments suggested a high degree of homology between these 5.1 kb plasmids. In the two other strains, production of a CAT type I was demonstrated, and the corresponding genes were either shown on a plasmid of 17 or 5.5 kb.19968877534
2010150.9996Epidemiological survey of genes encoding aminoglycoside phosphotransferases APH (3') I and APH (3') II using DNA probes. The epidemiological survey of APH (3') I and APH (3') II genes, at a time when the specific antibiotic pressure was very low, was carried out by DNA-DNA hybridization. The sample included 334 aminoglycoside resistant Gram-negative bacteria collected from patients of a General Hospital. Of these, 251 hybridized with the APH (3') I-probe and 19 with the APH (3') II-probe but only 190 strains showed high resistance levels (CIM greater than 64 micrograms/ml) for kanamycin, neomycin and paromomycin. These strains were isolated both from inpatients and outpatients with different infectious diseases. The APH (3') I-gene was dispersed among all the bacterial species and clinical specimens tested but the APH (3') II-gene was not found in Pseudomonas spp, Escherichia coli, Citrobacter freundii and Enterobacter cloacae, nor in infected catheters. Several plasmids of different sizes carrying APH (3') genes were detected among different bacteria. Plasmids along with transposable elements (the probes used in this work were developed from Tn906 and Tn5) and the high consumption of other antibiotics whose resistance is carried by these bacteria might be playing an important role in the maintenance and dispersion of APH (3') genes.19921328557
5846160.9995Distribution of tetracycline resistance genes and transposons among phylloplane bacteria in Michigan apple orchards. The extent and nature of tetracycline resistance in bacterial populations of two apple orchards with no or a limited history of oxytetracycline usage were assessed. Tetracycline-resistant (Tc(r)) bacteria were mostly gram negative and represented from 0 to 47% of the total bacterial population on blossoms and leaves (versus 26 to 84% for streptomycin-resistant bacteria). A total of 87 isolates were screened for the presence of specific Tc(r) determinants. Tc(r) was determined to be due to the presence of Tet B in Pantoea agglomerans and other members of the family Enterobacteriacae and Tet A, Tet C, or Tet G in most Pseudomonas isolates. The cause of Tc(r) was not identified in 16% of the isolates studied. The Tc(r) genes were almost always found on large plasmids which also carried the streptomycin resistance transposon Tn5393. Transposable elements with Tc(r) determinants were detected by entrapment following introduction into Escherichia coli. Tet B was found within Tn10. Two of eighteen Tet B-containing isolates had an insertion sequence within Tn10; one had IS911 located within IS10-R and one had Tn1000 located upstream of Tet B. Tet A was found within a novel variant of Tn1721, named Tn1720, which lacks the left-end orfI of Tn1721. Tet C was located within a 19-kb transposon, Tn1404, with transposition genes similar to those of Tn501, streptomycin (aadA2) and sulfonamide (sulI) resistance genes within an integron, Tet C flanked by direct repeats of IS26, and four open reading frames, one of which may encode a sulfate permease. Two variants of Tet G with 92% sequence identity were detected.199910543801
5951170.9995A novel plasmid from Aerococcus urinaeequi of porcine origin co-harboring the tetracycline resistance genes tet(58) and tet(61). Tetracyclines are the broad-spectrum agents used in veterinary medicine and food animal production. Known mechanisms of tetracycline resistance include ribosome protection, active efflux and enzymatic inactivation. However, the presence of two different tet genes conferring different resistance mechanisms on the same plasmid has rarely been reported. In this study, we identified the tandem tetracycline resistance genes tet(61)-tet(58) on the novel plasmid pT4303. These tet genes were identified for the first time in Aerococcus urinaeequi. Reduced susceptibility to doxycycline was observed in S. aureus RN4220 harboring tet(61) when an extra tet(58) was expressed. Plasmid pT4303 was electrotransformed into S. aureus RN4220, E. faecalis JH2-2, S. suis BAA and E. coli DH5α and conferred tetracycline resistance (MIC ≥ 16) in both Gram-positive and Gram-negative bacteria, assuming that it might serve as a vehicle for the dissemination of the tetracycline resistance genes tet(61) and tet(58).202133866063
2082180.9995Rapid screening technique for class 1 integrons in Enterobacteriaceae and nonfermenting gram-negative bacteria and its use in molecular epidemiology. A screening technique for integrons in members of the family Enterobacteriaceae and nonfermenting gram-negative bacteria by real-time PCR is reported. A total of 226 isolates of gram-negative bacteria obtained from a variety of clinical specimens were screened for class 1 integrons by real-time PCR performed on a LightCycler instrument. This technique used a primer pair specific for a 300-bp conserved region at the 5' ends of class 1 integrons. The screening assay was evaluated by comparison with results obtained by the conventional, thermal-block PCR (long PCR) by using established conditions and primers for the detection of class 1 integrons, and the real-time PCR technique was thus shown to be both sensitive and specific. DNA from 50 of 226 (22%) isolates screened was identified as containing an integron by the screening PCR, and sequence data were obtained across the integron for 34 of 50 (68%) of these isolates. In an attempt to study the molecular epidemiology of antimicrobial resistance genes carried within integrons, a comparison of the types of gene cassettes carried by isolates from different patients was made. Adenyltransferase genes conferring resistance to streptomycin and spectinomycin were the predominant gene cassettes amplified in the study. Resistance to trimethoprim was also frequently found to be encoded within integrons. Furthermore, multiple bacterial isolates obtained from one patient over a 5-month period were all shown to carry an integron containing the same single adenyltransferase gene cassette, suggesting that these elements were relatively stable in this case.200111257011
2080190.9995Distribution of the antiseptic-resistance genes qacE and qacE delta 1 in gram-negative bacteria. The distribution of the antiseptic-resistance genes qacE and qacE delta 1 was studied in a large number of Gram-negative bacteria by a method that included the polymerase chain reaction (PCR). A total of 117 strains of Gram-negative bacteria, isolated from clinical or environmental sources, was used in this analysis. We demonstrated the presence of these genes in 48 of 78 strains of Pseudomonas, in 20 of 26 strains of Vibrio, and in four of 13 strains of other species. These results indicate that the antiseptic-resistance genes are present in a broad range of species of Gram-negative bacteria.19989503610