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A Vivian

Publications and source records attributed to A Vivian.

31 records · Page 2Linked to original sources
PubMed1980

Naturally occurring plasmids in Acinetobacter calcoaceticus: a P class R factor of restricted host range.

A naturally occurring transmissible plasmid, designated pAV1, has been isolated in Acinetobacter calcoaceticus. It specifies resistance to sulphonamides and is capable of mobilizing two non-transmissible resistance determinants for tetracycline and neomycin, respectively, within strains of A. calcoaceticus. It is incompatible with the P class R factors RP4 and R751 in A. calcoaceticus. On this basis we conclude that pAV1 is a member of the P incompatibility group. However, unlike most other P group R factors, pAV1 is not transmissible to strains of Escherichia coli, Pseudomonas aeruginosa, Klebsiella or Proteus mirabilis.

Acinetobacter↗
PubMed1980

Gene transfer in Acinetobacter calcoaceticus: fertility variants of the sex factor pAV1.

The naturally occurring transmissible plasmid pAV1 mediates chromosome transfer and can exhibit two distinct levels of transmissibility in Acinetobacter calcoaceticus strain EBF65/65. The two states of pAV1 have been arbitrarily designated pAV1a (low frequency variant) and pAV1b (high frequency variant). Both variants have the same incompatibility and host range properties and each mobilizes two non-transmissible resistance determinants for tetracycline and neomycin. Sex factor activity has been shown to be stable: however, pAV1b fertility variants can be derived from pAV1a donors following conjugal transfer of pAV1 into new recipient strains of EBF65/65.

Acinetobacter↗
PubMed1980

Naturally occurring plasmids in Acinetobacter calcoaceticus: pAV2, a plasmid which influences the fertility of the sex factor pAV1.

Acinetobacter calcoaceticus strain EBF65/65 harbours a cryptic plasmid, pAV2, which has been shown by electrophoretic separation on agarose gels to have a molecular mass of approximately 13.5 megadaltons (Md). Transfer of the previously described sex factor pAV1 (Hinchliffe & Vivian, 1980 a,b) from the hospital strainJC17 into strains possessing pAV2 occurs only at a low frequency, whereas transfer to similar strains lacking pAV2 occurs at a much higher frequency. In EBF65/65, pAV1 may be present in strains possessing or lacking pAV2; pAV1 strains lacking pAV2 correspond to strains previously described as pAV1a (Hinchliffe & Vivian, 1980b) whereas pAV1 strains which also possess pAV2 correspond to pAB1b strains. The genetic evidence presented here is consistent with the hypothesis that pAV2 specifies a host restriction and modification system that is active against pAV1. Physical evidence from agarose gel electrophoresis indicates that pAV1 corresponds to a band of approximately 85 Md in strain JC17. The corresponding band in strains of EBF65/65 is difficult to distinguish because of the presence of a further cryptic plasmid band of approximately 88 Md, designated pAV3. A small cryptic plasmid of approximately 6 Md, designated pAV4, is reported for EBF65/65.

Acinetobacter↗
PubMed1980

Restriction mediated by pAV2 affects the transfer of plasmids in Acinetobacter calcoaceticus.

The naturally occurring plasmid pAV2 restricts the entry of the P class plasmid RP4 and the W class plasmids R388 and S-a into Acinetobacter calcoaceticus strain EBF65/65 from Escherichia coli. The W class plasmids only transfer from E. coli into pAV2-strains. Plasmid RP4 is modified in the presence of pAV2 such that it is no longer restricted on entry into pAV2 recipients of strain EBF65/65.

Acinetobacter↗
PubMed1976

RP4-mediated conjugation in Acinetobacter calcoaceticus.

The P class R factor RP4 was transferred from Escherichia coli K12 to Acinetobacter calcoaceticus. RP4 conferred similar levels of antibiotic resistance in A. calcoaceticus to those in the E. coli K12 donor. Only slight instability of RP4 in A. calcoaceticus was detected. Transfer of RP4 between strains of A. calcoaceticus was by conjugation and was accompanied by transfer of chromosomal genes. Possible polarity of marker transfer was observed and linkage between a number of chromosomal markers was demonstrated.

Acinetobacter↗
PubMedDate not supplied

Molecular characterization of the Pseudomonas syringae pv. pisi plasmid-borne avirulence gene avrPpiB which matches the R3 resistance locus in pea.

An avirulence gene (designated avrPpiB) from race 3 of Pseudomonas syringae pv. pisi was cloned and sequenced. The gene corresponded to a single open reading frame of 831 nt identified by transposon mutagenesis and subcloning. This ORF encodes a predicted hydrophilic protein of 276 amino acids (MW 31,300). It effects the expression of a resistance mechanism governed by a single genetic locus in pea. Cosegregation of resistance at the R3 locus of pea was observed towards race 3 and a transconjugant carrying the cloned avrPpiB gene according to the predicted 3:1 ratio of resistant:susceptible F2 progeny from a cross between Jade (R3 R3) and Kelvedon Wonder (rr) cultivars. DNA hybridization studies showed avrPpiB to be plasmid-borne in race 3 and suggested the presence of other alleles on one of the endogenous plasmids of races 1 and 7. Disruption of the avrPpiB allele of race 1 and its complementation confirmed its behavior towards pea cultivars expressing the R3 locus. Homologs of avrPpiB were detected in P. syringae pv. phaseolicola, P. syringae pv. maculicola, and P. syringae pv. tomato. The presence of avrPpiB homologs in P. syringae pv. phaseolicola does not match any gene-for-gene pattern of interaction with bean cultivars.

Amino Acid Sequence↗
PubMedDate not supplied

[Histologic microbiopsy with 14 G needle in the diagnosis of breast lesions. Experience with 1000 cases].

PURPOSE: We report our experience with large core biopsy (LCB: 14-Gauge needles) of questionable or suspicious breast lesions detected at mammography and/or US. All biopsies were performed under instrumental guidance. We also report on technique, costs, time, advantages and disadvantages of the method and, finally, give precise indications on when and why large core biopsy is needed. MATERIAL AND METHODS: From january 1996 to may 2000 we performed 1000 microhistologic biopsies on breast lesions at the Unità Integrata di Senologia, Azienda Ospedaliera Careggi, Florence; 650 (65%) were non palpable lesions. Large core needles were used (14-Gauge caliber). In the majority of cases (70%) we used US guidance, in the others a stereotactic guidance was employed. RESULTS: Microhistologic biopsy allowed accurate characterization in most cases. Inadequate samples were obtained in 15 cases. The false negative rate was 6%. Surgery was needed to characterize the lesion unquestionably in 13 cases only. CONCLUSION: In agreement with literature reports, our results confirm large core biopsy as an adequate alternative to surgical biopsy and, to some extent, to FNAC, thanks to its moderate invasiveness, low costs, short execution time, little patient discomfort and high sensitivity (93.98%) and specificity (99.7%).

Biopsy, Needle↗