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B J Mee

Publications and source records attributed to B J Mee.

34 records · Page 2Linked to original sources
PubMed1989

Distribution of plasmid maintenance regions among IncFIV plasmids.

The distribution of the IncFI basic replicons among IncFIV plasmids was assessed by DNA hybridization. In addition these and 20 other plasmids from 16 incompatibility groups were screened for the presence of IncIV, an incompatibility determinant recently found on the IncFIV plasmid R124. The IncIV determinant was found commonly but not universally among the IncFIV plasmids. It was also detected on the IncFI reference plasmid R386 and plasmids from IncB, IncI alpha and IncI gamma. The frequency and distribution of IncFI replicons among the IncFIV plasmids is similar to that observed in other F groups. The similarity of the IncFIV plasmids to plasmids of the other IncF groups and the failure to find replicons unique to IncFIV plasmids indicates that their division into a separate incompatibility group is not justified.

DNA Probes↗
PubMed1988

The epidemiology of Neisseria gonorrhoeae isolates from Western Australia based on antibiotic resistance and plasmid profiles.

Two collections of 90 distinct isolates of Neisseria gonorrhoeae were examined with respect to their plasmid profiles, auxotypes and antibiotic sensitivities to penicillin, erythromycin, streptomycin, spectinomycin, sulphamethoxazole, tetracycline and trimethoprim. The two series, collected from 1976-1981 and from 1985-1986 possessed similar sensitivity patterns except for erythromycin and trimethoprim. The earlier collection of penicillinase producing N. gonorrhoeae (PPNG) was found to be significantly more resistant to both these antibiotics. Within each series the PPNG isolates were more resistant to penicillin and streptomycin than the non-PPNG. All PPNG isolates had the 4.4 X 10(6) dalton penicillinase plasmid and frequently exhibited an auxotype which included a requirement for proline. The frequency of the 24.5 X 10(6) dalton transfer plasmid in the non-PPNG was found to have increased threefold from the early collection to the later one while amongst the PPNG the frequency of the transfer plasmid was seen to decrease. Auxotyping results indicated that the transfer plasmid played a significant role in the spread of the penicillinase plasmid in the early collection. In the later collection a transfer-plasmid-free strain, which required only proline, comprised almost half of the penicillinase producers and this PPNG strain now appears to be adapted to our environment.

Gonorrhea↗
PubMed1987

Characterization of the maintenance functions of IncFIV plasmid R124.

The genetic arrangement of the regions involved in R124 replication and incompatibility have been located and their homology to the IncFI basic replicons has been assessed. We show that R124 has homology with all three basic replicons, RepFIA, RepFIB, and RepFIC, and that these regions, FIVA, RepFIVB, and RepFIVC, are widely separated on the R124 genome. Cloning of autonomously replicating fragments has shown that RepFIVB and RepFIVC are functional in R124 and express incompatibility. The FIVA region was unable to form a functional replicon and when cloned into pUC8 lacked incompatibility activity. A fourth region of R124 was identified, which although not essential for replication stabilized mini-R124 plasmid replication and exhibited incompatibility with R124. This region, designated IncIV, showed no homology to RepFIA, RepFIB, or RepFIC. Incompatibility expression of IncIV required only the EcoRI fragment E13 but the strength of the reaction was modified in the presence of other fragments. The replication and incompatibility properties of an R124 deletion derivative indicated that R124 can switch its replication to either RepFIVB or RepFIVC when in the presence of an incompatible plasmid. The ambiguous incompatibility reactions reported for R124 is a result of the expression of the two functional replicons, RepFIVB and RepFIVC, and that expressed by IncIV.

Chromosome Mapping↗
PubMed1987

Mapping of trimethoprim resistance genes from epidemiologically related plasmids.

Trimethoprim resistance dihydrofolate reductase genes from plasmids known to be exchanging between human and animal populations were mapped. The dihydrofolate reductase gene has been highly conserved in all plasmids, but differences in the flanking regions provide evidence that the most recent exchange of plasmids between the two ecosystems has been from animals to humans.

Animals↗
PubMed1986

Evolution and spread of IncFIV plasmids conferring resistance to trimethoprim.

Twenty-one IncFIV-group plasmids conferring trimethoprim resistance in Escherichia coli isolates from humans and pigs were examined. Three evolutionary lines of plasmids were identified on the basis of restriction enzyme analysis. One was found exclusively in human isolates and another was found in pig isolates, while the third line consisted of plasmids from both sources. All R plasmids readily transferred to laboratory strains, and evidence was found for transfer to other biotypes of E. coli in the environment. The Tpr genes from representatives of the plasmid lines were cloned and compared by restriction analysis and by hybridization with two characterized Tpr dihydrofolate reductase genes. The sequences flanking the Tpr genes were different for each line, but all showed homology with the type 2 dihydrofolate reductase gene, irrespective of whether they were of human or animal origin. There was no hybridization to the type 1 gene. The remarkable degree of similarity among plasmids of the third line provided clear evidence of the exchange of plasmid-bearing E. coli between humans and pigs.

Animals↗
PubMed1985

A restriction map of IncFIV plasmid R124.

A physical and genetic map of the 125.7-kb IncFIV plasmid R124 was constructed using the restriction enzymes Sal1 and EcoR1. Two discrete regions involved in plasmid replication were identified on the plasmid genome. One region was located on a 4.66-kb segment of an EcoR1 fragment at map coordinates 73.87 to 78.53 kb. Another was located within an 8.05-kb segment of an EcoR1 fragment at map coordinates 113.40 to 121.45. This region was very unstable but, when ligated to the 3.21-kb EcoR1 fragment E13 located at map coordinates 18.83 to 22.06 kb, replication was stable. Thus, at least three regions of R124 widely separated around the genome are associated with plasmid replication and stable maintenance. Each of these three regions expressed incompatibility with R124. The Tc resistance gene of R124 was located on the contiguous EcoR1 fragments E8 and E12 located at map coordinates 100.49 to 113.40.

Base Sequence↗
PubMed1985

A comparative study of three bacteriocins of Bacteroides fragilis.

Three different bacteriocins produced by strains of Bacteroides fragilis were compared in terms of their production kinetics, physico-chemical nature, and action on macromolecular synthesis in a common indicator strain. Bacteriocin 78/438 was produced during the logarithmic growth phase, was thermolabile and stable between pH 5 and 9. It was susceptible to trypsin and pepsin, and affected DNA, RNA and protein syntheses in susceptible cells. Bacteriocin A49 was produced during the stationary growth phase, was thermolabile and stable between pH 7 and 9. This bacteriocin was also susceptible to trypsin and pepsin, but only RNA synthesis was affected in the indicator strain. Bacteriocin A55 differed markedly from both 78/438 and A49, and was found to be predominantly cell-bound, resistant to inactivation by high temperatures and stable over a wide pH range of 2 to 12. It was susceptible to trypsin but resistant to pepsin. A55 had a delayed effect on macromolecular synthesis with DNA synthesis being inhibited after 60 min. With all three bacteriocins, killing of the indicator strain followed single hit kinetics with the interaction of bacteriocin and target cell occurring in two stages. Killing by bacteriocin A55 was much slower than the other two and this may be related to its effect on macromolecular synthesis. The killing action of all three bacteriocins was dependent on the growth phase of the susceptible cells.

2,4-Dinitrophenol↗
PubMed1984

Physiological properties and plasmid content of Bacteroides spp.

A collection of 50 clinical isolates of Bacteroides was examined for plasmid deoxyribonucleic acid content. An attempt was then made to correlate the presence of plasmids with a specific phenotypic property. Of the 20 Bacteroides which contained plasmids, 18 were found to harbour plasmids of less than or equal to 9.8 megadaltons. The most common plasmid had a molecular weight of 4.8 megadaltons and was found in 9 strains. Most strains had multiple plasmid bands. All strains were examined for resistance to penicillin, cefoxitin, erythromycin, tetracycline, sulphamethoxazole, clindamycin, chloramphenicol, arsenate, silver, cadmium, mercury, chromium, lead, nickel and cobalt, and for the production of beta-lactamase, heparinase, deoxyribonuclease, haemolysins and bacteriocins. Using a Chi-squared analysis, there was no statistically significant correlation between any of these phenotypic traits and the presence of plasmids, except bacteriocin production. A total of 15 out of 20 (75%) of plasmid-containing strains produced bacteriocins while only 10 out of 30 (33%) of plasmid-free strains were capable of bacteriocin production (chi 2, p less than 0.005). Attempts to transfer or cure resistance to antibiotics and heavy metals or bacteriocin production were not successful.

Bacteriocins↗
PubMed1983

Plasmids encoding trimethoprim resistance in bacterial isolates from man and pigs.

Trimethoprim (Tp) resistant Gram negative bacteria were isolated from humans and pigs. The bacterial hosts were characterized by their resistance pattern and biotype. The presence of transferable Tp plasmids was demonstrated in 86% of 59 porcine isolates and 37% of 49 human isolates. The Tp R-plasmids carried a diversity of resistance determinants such as Tc, Cm, Sp, Sm and Su. Incompatibility tests distinguished two major groups, Inc FIV and Inc N. Thirty of 99 Tp R-plasmids isolated from humans were grouped as Inc FIV and eight as Inc N. The results of molecular weight determination of Tp R-plasmids performed by agarose gel electrophoresis were consistent with the existence of two groups--larger R-plasmids (76 to 104 Md) belonging to Inc FIV and lower molecular weight R-plasmids (25 to 35 Md) belonging to Inc N. Results from this study indicate that the Tp R-plasmids isolated in Perth have evolved independently from those described in Europe and the United Kingdom. There is also evidence for their local spread between Escherichia, Klebsiella, Enterobacter, Citrobacter and Acinetobacter from man and animals.

Animals↗
PubMed1982

A bacteriocin typing scheme for Bacteroides.

Epidemiological studies of Bacteroides spp. have been hindered because a suitable typing method is not available. In preliminary studies, 50 strains of Bacteroides were screened against each other for bacteriocin production and sensitivity; 54% of them produced bacteriocin(s) and more than 90% were sensitive to at least one bacteriocin. After calculation of similarity values for these 50 isolates, a typing set of six bacteriocinogenic strains was selected for a typing method based on bacteriocin sensitivity. With this typing set c. 90% of strains could be typed and tests of reproducibility suggested that acceptable accuracy and discrimination could be obtained without applying any one-reaction or two-reaction difference rules. Isolates from four hospitals gave a similar spectrum of typing patterns with 18 bacteriocin types being demonstrated. There was not correlation between bacteriocin type and species of Bacteroides.

Bacteriocins↗
PubMed1982

Susceptibility of Bacteroides spp. to heavy metals.

The susceptibility of 105 strains of Bacteroides to arsenate, silver, nickel, cobalt, lead, cadmium, chromium, and mercuric ions was tested by using an agar dilution technique. All strains of Bacteroides were multiply resistant. Bacteroides fragilis was significantly more resistant to silver ions than other Bacteroides species and slightly more resistant to several other ions. Arsenate was the most active ion tested, with 75% of strains being susceptible. All 25 strains of B. fragilis tested against silver sulfadiazine were susceptible.

Bacteroides↗
PubMed1982

Survival of Salmonella adelaide and fecal coliforms in coarse sands of the swan costal plain, Western Australia.

The survival of Salmonella adelaide and fecal coliforms in two coarse sands influenced by two sources of septic tank effluent was studied. The experiments were conducted in conditions that reflected the soil environment beneath functioning septic tank systems. Significant differences in survival were found with different effluent sources. In one experiment the survival of S. adelaide was similar to that of fecal coliforms; in the other it was not. The nonuniform, multiphasic nature of survival curves was variability observed in these experiments suggests that the application of such survival data for establishing management criteria for septic tank systems--by, for example, the use of soil moisture characteristic curves to give estimates of movement in the soil--is inappropriate.

Analysis of Variance↗