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D Law

Publications and source records attributed to D Law.

At least 37 records · Page 2Linked to original sources
PubMed1996

In vitro activity of BMS-181184 compared with those of fluconazole and amphotericin B against various candida spp.

We compared the in vitro activity of BMS-181184, the first compound of a new class of antifungal agents, the pradimicins, with those of fluconazole and amphotericin B against 64 clinical isolates of Candida species. MICs were determined by a microdilution method with high resolution medium for BMS-181184 and fluconazole and antibiotic medium no. 3 with 2% glucose for amphotericin B. MICs of BMS-181184 for all yeasts were in the range of 0.78 to 12.5 micrograms/ml. BMS-181184 was active against isolates resistant to other antifungal agents, consistent with a novel mode of action. Minimum fungicidal concentrations for 16 isolates showed that BMS-181184 was fungicidal. Clinical studies are now required to confirm its activity.

Amphotericin B↗
PubMed1996

Evidence of multiple extracellular phospholipase activities of Aspergillus fumigatus.

Extracellular phospholipase activity has been implicated in the pathogenesis of several bacterial infections. Recently, extracellular phospholipase activity has been proposed as a virulence factor in the opportunistic yeast Candida albicans. Aspergillus fumigatus is the most pathogenic member of its genus, responsible for > 90% of infections. Previously, no specific virulence factors have been determined. We investigated the ability of A. fumigatus to produce extracellular phospholipases at 37 degrees C. Fast atom bombardment was used to compare lipid-containing media before and at 5-h intervals during shaking culture of A. fumigatus. Lipids were extracted and analyzed. Many anions corresponding to phospholipid breakdown products were identified. Specific anion species identified indicated phospholipase A, B, C (PLC), and D activities. PLC activity was further investigated by using the synthetic substrate p-nitrophenylphosphorylcholine. PLC activity was initially observed after 30 h of growth and accumulated in broth cultures up to 50 h. At 55 h, there was a sharp increase in PLC activity which coincided with cultures reaching the stationary phase. Activity of the PLC was measured at different temperatures, with greater activity occurring at 37 degrees C than at lower temperatures. Phospholipases could represent a virulence determinant in A. fumigatus.

Aspergillus fumigatus↗
PubMed1995

In vitro activity of D0870 compared with those of other azoles against fluconazole-resistant Candida spp.

We compared the in vitro activity of a new triazole, D0870, with those of fluconazole, itraconazole, and ketoconazole against 41 clinical isolates of fluconazole-resistant Candida belonging to nine different species. The 50% inhibitory concentrations (IC50s) were determined by a microdilution method with morpholinopropanesulfonic acid (MOPS)-buffered RPMI medium and an inoculum of approximately 10(4) yeasts per ml. After incubation for 48 h at 37 degrees C the optical density at 550 nm was measured. The IC50 was the lowest drug concentration which reduced the optical density at 550 nm by > or = 50% compared with that for a drug-free control. D0870 had significant activity against many of the isolates. Its activity was comparable to that of ketoconazole, slightly superior to that of itraconazole, and markedly superior to that of fluconazole against Candida albicans. Against Candida glabrata, Candida krusei, and Candida inconspicua, it had activity similar to those of itraconazole and ketoconazole but had activity superior to that of fluconazole. D0870 IC50s for some isolates were increased. This may be due to cross-resistance mechanisms because the IC50s of both itraconazole and ketoconazole for these isolates were often high. When IC50s and IC80s were compared there was a marked organism and drug variation. With C. glabrata much higher endpoints for itraconazole were observed when an IC80 endpoint was used. For C. albicans there was also a significant shift upward in endpoints for itraconazole and ketoconazole. Values were changed little when IC50 and IC80 endpoints of D0870 were compared. For 35 of 41 isolates tested the D0870 IC50 was less than the 2.5-mg/liter breakpoint threshold proposed previously. Therefore, D0870 may be a useful agent for the therapy of infections caused by fluconazole-resistant Candida spp.

Antifungal Agents↗
PubMed1995

Use of heme and hemoglobin by Escherichia coli O157 and other Shiga-like-toxin-producing E. coli serogroups.

The virulence properties of Escherichia coli O157 isolates were compared with those of Shiga-like-toxin-producing E. coli of non-O157 serogroups. The growth of all E. coli O157 isolates was stimulated by both heme and hemoglobin, and all produced enterohemolysin. The incidence of these properties was significantly lower in the non-O157 isolates. This may contribute to the greater virulence and higher incidence of human infection caused by E. coli O157.

Bacterial Toxins↗
PubMed1994

High prevalence of antifungal resistance in Candida spp. from patients with AIDS.

Three hundred and forty-eight isolates of Candida spp. from patients treated at a regional infectious diseases unit for AIDS, immunocompromised patients admitted to the Hope Hospital and isolates referred from around the North West of England were tested for their in-vitro susceptibility to amphotericin B, fluconazole and flucytosine using standardized methods. Candida albicans comprised 73% of isolates, Candida glabrata 10% and Candida parapsilosis 7%. Ninety-six percent of isolates were susceptible to amphotericin B and resistance to > or = 12.5 mg/L fluconazole was found in 61 (17.5%) of the 348 isolates tested. Among isolates from patients with AIDS the incidence of fluconazole resistance was 33% whereas in other patients the incidence was only 11%. Flucytosine resistance was seen in only 12 (3.4%) isolates, 11 of which were C. albicans and in 6.5% of isolates from patients with AIDS. Resistance to fluconazole and flucytosine is now sufficiently prevalent among Candida spp. isolated from patients with AIDS to warrant routine susceptibility testing of yeast isolates.

AIDS-Related Opportunistic Infections↗
PubMed1994

Diagnosis of infections with Shiga-like toxin-producing Escherichia coli by use of enzyme-linked immunosorbent assays for Shiga-like toxins on cultured stool samples.

Shiga-like toxin-producing (SLT) Escherichia coli, particularly those belonging to serogroup O157, are responsible for haemorrhagic colitis, haemolytic uraemic syndrome and some cases of gastro-enteritis. The rapid and reliable diagnosis of all these infections is necessary for correct patient management and for epidemiological reasons, but is rarely possible with present methods. We compared the efficacy of two methods, (i) the culture of faeces in broth that contained mitomycin C followed by enzyme-linked immunosorbent assay (ELISA) for SLTs, and (ii) the culture of faeces on sorbitol MacConkey agar (SMA), in the detection of infections caused by SLT-producing E. coli. SLT-producing E. coli O157 strains were isolated on SMA from 42 of 475 faecal samples, but SLTs were detected by ELISA in culture supernates or lysates of 54 of 475 samples. SLT-producing E. coli strains were isolated subsequently from 11 of 12 ELISA-positive, SMA culture-negative samples by a colony blot technique. In four cases, SLT-producing E. coli of serogroups other than O157 were isolated and in seven cases E. coli O157 was isolated in small numbers. The ELISA is a rapid and sensitive technique for the diagnosis of SLT-producing E. coli infection, especially where low numbers of the organism are present in faeces and when the infection is caused by a serogroup other than O157.

Bacterial Toxins↗
PubMed1994

Bioassay for serum itraconazole concentrations using hydroxyitraconazole standards.

Low concentrations of itraconazole in serum have been associated with therapeutic failure. Variable interpatient bioavailability and detrimental drug interactions with p450 enzyme-inducing agents are well documented. Thus, routine monitoring of serum itraconazole concentrations in patients with life-threatening mycoses is essential for patient care. Present high-performance liquid chromatography (HPLC) methods measure only concentrations of itraconazole and not its active metabolite hydroxyitraconazole. Bioassay methods using itraconazole standards overestimate concentrations in serum as measured by HPLC. We have developed a bioassay for total serum itraconazole and hydroxyitraconazole concentrations using hydroxyitraconazole standards. Itraconazole and hydroxyitraconazole concentrations in 40 clinical samples were assayed by HPLC. Total drug concentrations were measured in the same samples by bioassay with itraconazole or hydroxyitraconazole standards. The correlation of concentrations measured by the last bioassay method with HPLC determinations of both compounds was excellent (r = 0.98, slope = 0.5), with acceptable reproducibility. Small errors were seen at extremes of concentrations. The ratio of hydroxyitraconazole to itraconazole in serum varied from 0.76 to 3.2. The use of hydroxyitraconazole standards rather than itraconazole standards for determination of total itraconazole and hydroxyitraconazole concentrations in serum by bioassay gives accurate and reproducible results that correlate well with total itraconazole and hydroxyitraconazole concentrations as measured by HPLC. Our data show that although hydroxyitraconazole gives larger inhibition zones than itraconazole in bioassay standards, this is not true of patient samples, in which the two compounds make equivalent contributions.

Antifungal Agents↗
PubMed1994

Adhesion and its role in the virulence of enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) organisms are an important cause of diarrheal disease in young children. The virulence of EPEC is a multifactorial process and involves a number of distinct stages. Initial adherence to intestinal mucosa is mediated by fimbriae which bring about a distinct form of adhesion, localized adhesion. Intimate adhesion of the bacterium to the eukaryotic membrane occurs, resulting in the activation of signal transduction pathways. Microvilli are disrupted and effaced from the apical membrane which then cups around the organism to form pedestal structures, the attaching and effacing lesion. Diarrhea may be produced by alteration of the permeability of the apical membrane and also through a malabsorption mechanism. The pathways involved in the production of the attaching and effacing lesion are described. EPEC organisms were originally thought to belong to a number of distinct serogroups; it is now apparent that many isolates belonging to these serogroups are not pathogenic or belong to other pathogenic groups of E. coli. In addition, isolates falling outside of these serogroups are considered to be true EPEC. The definition of EPEC based on serotyping is inaccurate and should be replaced by methods that specifically detect the virulence properties of EPEC.

Bacterial Adhesion↗
PubMed1993

In-vitro activity of the new triazole D0870 compared with amphotericin B and itraconazole against Aspergillus spp.

The in-vitro activity of D0870, a new triazole, was compared with amphotericin B (AMP B) and itraconazole (ITZ) against 40 Aspergillus isolates, which included 25 isolates of Aspergillus fumigatus, using a broth macro-dilution method at 37 degrees C. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) (killing of > or = 98%) were measured. For 40 isolates, geometric mean (GM) MIC values and ranges were D0870 10.55 and 2-32, ITZ 2.26 and 0.5-64, AMP B 2.42 and 1-64 mg/L. Differences in susceptibilities between species were apparent with Aspergillus flavus (n = 5) being the most susceptible to D0870 (GM 2.64, range 2-8 mg/L). MFC values were within one dilution of the MIC value for 90% of isolates (D0870 and ITZ) and 95% of isolates (AMP B). In reproducibility studies, seven, eight and four of eight isolates retested gave MIC results within one dilution for D0870, AMP B, and ITZ, respectively. Therefore, in-vitro mould testing with D0870 is feasible and reproducible with clear MIC and MFC end-points. D0870 is active against most Aspergillus spp., but at higher concentrations than either ITZ or AMP B.

Amphotericin B↗
PubMed1993

Patients with haemolytic uraemic syndrome caused by Escherichia coli O157: absence of antibodies to Vero cytotoxin 1 (VT1) or VT2.

Serum samples from 30 patients with haemolytic uraemic syndrome (HUS), caused by Escherichia coli O157, and 30 apparently healthy volunteers, were used to examine the immune response of patients to Vero cytotoxins (VT) 1 and VT2. Patients' sera could not be differentiated from control sera using ELISA; and using immunoblotting, none of the sera had antibodies reactive with either the A or B subunits of VT1 or VT2. Examination of sera for antibodies to VT1 and VT2 seems to be of little value in the serodiagnosis of HUS caused by Vero cytotoxin-producing E coli O157.

Antibodies, Bacterial↗
PubMed1992

The influence of salt concentration on the detection of methicillin resistance in coagulase-negative staphylococci.

The detection of methicillin resistance by the breakpoint method was examined using three different media containing varying quantities of added salt and 4 mg/L methicillin or 1 mg/L oxacillin. Three hundred clinical isolates of eight species of coagulase-negative staphylococci were tested. In 68 strains methicillin resistance was expressed only at certain salt concentrations and four distinct susceptibility phenotypes were observed. A correlation between the susceptibility phenotype and the species of the isolate was found. Testing on Columbia agar (CA) containing 4 mg/L methicillin with 0% and 4% added salt was required to detect resistance in all 68 strains. Resistance was detected less frequently using Balanced Sensitivity Test (BST) agar or Diagnostic Sensitivity Test (DST) agar containing methicillin or CA, BST or DST agar containing oxacillin. Increased production of beta-lactamase was shown to be an unlikely cause of MR in these strains. Disc sensitivity tests were performed on the 68 strains using five different media. Columbia agar gave optimum results as the other media gave enhanced zones of inhibition for some isolates. Further tests were performed on CA containing varying salt concentrations using both oxacillin and methicillin discs. A close relationship between the staphylococcal species, and the influence of increasing salt concentration on zone size was found. Discrepancies were noted between results obtained by breakpoint and the results obtained with methicillin discs particularly with Staphylococcus simulans and some Staphylococcus epidermidis strains. Results obtained with oxacillin discs more closely correlated with those obtained by breakpoint, but only when disc tests were performed on media with low and high salt content. To identify methicillin resistance in strains of CNS by disc tests, the use of Columbia agar with 0% and 5% added salt and oxacillin discs is recommended.

Coagulase↗
PubMed1992

Detection by ELISA of low numbers of Shiga-like toxin-producing Escherichia coli in mixed cultures after growth in the presence of mitomycin C.

Techniques currently available to detect Shiga-like toxin (SLT)-producing Escherichia coli lack sensitivity or require specialised equipment and facilities, and in some cases detect only strains belonging to serotype O157. We have used an ELISA technique, capable of detecting both SLTI and SLTII with crude P1 glycoprotein from hydatid cysts, in combination with enhancement of toxin production by culture with mitomycin C. Supernates of Tryptone Soya Broth cultures containing mitomycin C 200 ng/ml were tested for SLTII. For SLTI, cell lysates pre-treated with polymyxin B were tested. In tests with E. coli O157:H7 in mixed culture with E. coli strain C600 alone, or with E. coli C600, Proteus mirabilis and Enterococcus faecalis, SLTI could be detected when the proportion of toxigenic organisms represented 1% of the mixture, and SLTII when the proportion was 0.025%. When faecal samples with added E. coli O157:H7 were examined in this system, SLTII-producing strains were detected when they comprised less than 0.1% of the coliform population. This technique is a sensitive and specific assay for detecting low numbers of SLT-producing organisms in mixed culture such as occurs in cases of haemolytic uraemic syndrome and haemorrhagic colitis.

Bacterial Toxins↗
PubMed1992

The iron uptake mechanisms of enteropathogenic Escherichia coli: the use of haem and haemoglobin during growth in an iron-limited environment.

The iron uptake mechanisms of enteropathogenic Escherichia coli (EPEC) were examined and compared with those of control E. coli strains. The incidence of aerobactin production was similar (39% and 37% respectively) in the two groups. The quantities of enterochelin produced by aerobactin-negative EPEC and control strains were similar, as were the quantities of enterochelin produced by aerobactin-positive EPEC and control strains. The ability to use haem or haemoglobin as an iron source in an iron-restricted environment was found in 80.4% and 60.8% of EPEC strains respectively, and in 76.6% and 56.6% of control E. coli strains. The ability of E. coli strains to use these compounds was not related to the production of enterochelin or aerobactin or to the production of haemolysins, and may be an important characteristic of bowel organisms. When growing in an iron-limited environment, the iron contained in haemoglobin was used in preference to ovotransferrin-bound iron. During periods of haemoglobin-stimulated growth, the enterochelin uptake system was shown to be fully expressed and may be involved in transport of haemoglobin-derived iron into the cell. Uptake of ovotransferrin-bound iron took place immediately upon exhaustion of haemoglobin-derived iron. The ability to use iron derived from haem compounds represents an alternative iron uptake mechanism for organisms growing in an iron-limited environment and allows greater flexibility during growth in vivo.

Bacterial Outer Membrane Proteins↗
PubMed1992

Citrate transport in proximal cell line.

Citrate uptake into kidney proximal tubules occurs via an apical dicarboxylate transporter and a poorly characterized process in the basolateral membrane. We used OK cells, a cell line derived from opossum kidney, to study citrate transport in proximal tubule-like cells. Citrate uptake into cell monolayers was studied using [14C]citrate with [3H]mannitol as a volume marker. Citrate uptake into these cells was sodium dependent and saturable with increasing concentrations of citrate. In contrast to previous models, citrate transport was altered minimally by changes in pH from 6.2 to 7.0 and increased at pH 7.4 to 7.8. A variety of di- and tricarboxylates were tested for interaction with citrate transport. The dicarboxylates succinate, malate, and oxaloacetate at 1 mM concentration inhibited citrate uptake minimally (uptake at least 80% of control); one dicarboxylate, alpha-ketoglutarate, did inhibit citrate uptake significantly. In contrast, the tricarboxylates isocitrate and tricarballylate inhibited citrate uptake significantly, indicating probable competitive inhibition with the transport process. These characteristics are distinctly different from those of the apical membrane dicarboxylate transporter. 1,2,3-Benzenetricarboxylic acid, an inhibitor of the mitochondrial tricarboxylate transporter, did not alter citrate uptake. In conclusion, the OK proximal cell line exhibits a novel citrate transport process compared with the apical transport of citrate described in most proximal systems. This transport process probably involves the trivalent species of citrate in contrast to the usual predominant transport of divalent citrate. This transport process may represent a process similar to that in the basolateral membrane of the proximal tubule.

Animals↗
PubMed1992

How much do junior staff influence patient throughput in a surgical unit?

A study was undertaken of inpatient throughput in a surgical department on a 'split site' District General Hospital. The study compared the individual contribution of equally qualified and experienced surgical registrars working at both sites. The results show that one registrar was associated with a statistically significant higher patient throughput, which appeared to be the result of a more expeditious approach to patient management. There was no evidence of an accompanying reduction in the quality of care delivered. The additional throughput amounted to approximately 300 extra patients in two years, and made a substantial contribution to the surgical workload in the District.

Bed Occupancy↗
PubMed1992

Escherichia coli: rapid identification by chromogenic tests.

A system has been assessed for the identification of Esch. coli using a rapid triple chromogenic test which relies on the ability of the organism to produce a beta-galactosidase, a beta-glucuronidase, and indole. Coliforms which had been fully identified were tested by this system. Of 512 non-Esch. coli strains there were no false positives, whereas of 514 Esch. coli strains 486 (94.5%) were found to give positive results. Two hundred and twenty-one coliforms that had been isolated from blood cultures were also tested using the colistrip in advance of, or without knowledge of the API 20E result. The test was found to be 100% specific and 94% sensitive for the 105 Esch. coli strains. The test was rapid, simple to perform and economical.

Chromogenic Compounds↗
PubMed1991

Characterization and application of a murine monoclonal antibody that reacts specifically with the serogroup D1 Salmonella.

A murine hybridoma cell line that produces monoclonal antibody (mAb) against the serogroup D1 Salmonella lipopolysaccharide (LPS) antigen was established. The trisaccharide tyvelose alpha 1----3 mannose alpha 1----4 rhamnose was shown to be involved in the reactive epitope of the mAb since this mAb reacted strongly with strains of serogroup D1 Salmonella but not with Salmonella strains from the O serogroups of A, B, and D2, and sodium meta-periodate was found to destroy the reactivity of the serogroup D1 O-antigen with the mAb. As such this mAb was found to be a useful serotyping reagent for the identification of serogroup D1 Salmonella, and for the differentiation of strains of serogroups D1 and D2 Salmonella which have identical flagellar H antigens.

Animals↗