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Biomedical subjects

S A Crawford

Publications and source records attributed to S A Crawford.

At least 19 recordsLinked to original sources
PubMed2006

Cellular and subcellular compartmentation of Ni in the Eurasian serpentine plants Alyssum bracteatum, Alyssum murale (Brassicaceae) and Cleome heratensis (Capparaceae).

This study investigated the cellular and subcellular compartmentation of Ni in the Eurasian serpentine species Alyssum murale, Alyssum bracteatum and Cleome heratensis and a non-serpentine population of A. murale (as a control) grown in hydroponic culture. Plant growth responses and Ni uptake clearly revealed the higher Ni tolerance of serpentine plants than the non-serpentine plants. Serpentine A. murale and A. bracteatum grew better at elevated (0.01 mM) Ni in the nutrient solution, supporting the view that the Ni hyperaccumulators have a higher requirement for Ni than normal plants. Low shoot Ni content of C. heratensis in response to the high Ni treatments indicated that this species employs an avoidance strategy for Ni tolerance. Energy-dispersive X-ray microanalysis showed that Ni was highly concentrated in the cell walls and cell lumen, most likely the vacuoles, of leaf epidermis of A. murale and A. bracteatum rather than in the mesophyll cells. EDX spectra from leaves of the non-serpentine A. murale suggested that Ni accumulated in both epidermal and mesophyll cells but not in the epidermal cell walls. Growth reduction and Ni toxicity in plants of the non-serpentine A. murale could be due to accumulation of Ni in the lumen of leaf mesophyll cells. Our data suggest that cellular and subcellular compartmentation are both possible mechanisms for Ni tolerance employed by the serpentine A. murale and A. bracteatum.

Brassicaceae↗
PubMed2005

Mutations in folP associated with elevated sulfonamide MICs for Neisseria meningitidis clinical isolates from five continents.

Sulfonamide resistance in meningococci is associated with mutations in the chromosomal gene folP, which encodes dihydropteroate synthase. Several mutations associated with resistance have been previously described, including amino acid substitutions at codons 31 and 194, a glycine-serine insertion at codons 195 and 196, and, recently, an additional mutation at nucleotide 682 (C682A). In this study, sulfisoxazole MICs were determined for 424 geographically diverse clinical isolates of Neisseria meningitidis, including all major subtypes. A subset of 134 isolates with MICs ranging from 0.5 to >64 microg/ml were assayed for the C682A mutation by real-time PCR, and 25 isolates were selected for folP gene sequencing. All isolates for which the sulfisoxazole MIC was >/=8 possessed the C682A mutation by real-time PCR or folP sequencing, and 34 of 35 isolates with a MIC of </=2 lacked this mutation. Of 16 sequenced isolates for which the sulfisoxazole MIC was >/=4, 15 possessed previously described mutations, including 10 at codon 31, 1 at codon 194, and 4 with the 2-amino-acid insertion codons 195 and 196; all 16 possessed the C682A mutation. The C682A mutation predicted elevated sulfonamides MICs for a large number of geographically diverse clinical isolates of meningococci. Detection of this mutation by real-time PCR or other methods may allow more wide-scale detection of meningococcal isolates with for which the sulfonamide MICs are elevated without resorting to multiple assays or folP gene sequencing, providing a simple, high-throughput screening method for use in public health and epidemiologic settings.

Anti-Bacterial Agents↗
PubMed2005

An investigation of the impact of the Force Sensing Array pressure mapping system on the clinical judgement of occupational therapists.

OBJECTIVES: To examine the impact of pressure mapping technology on the clinical decisions of occupational therapists and to examine the role of the Braden Scale in assisting with the selection of pressure-reducing cushions. DESIGN: Case studies. SETTING: Community. SUBJECTS: Forty clients. INTERVENTIONS: Clients were pressure mapped on their current seating surface and on four pre-selected cushions by the principal researcher. An occupational therapist completed the Braden Scale and a decision tree to assist in recommending a suitable pressure-reducing cushion. MAIN OUTCOME MEASURES: Interface pressure maps, Braden Scale, and the cushion recommended, using a decision tree to guide clinical judgement. RESULTS: Thirty per cent (12) of the 40 cushions recommended were changed when the pressure maps from the Force Sensing Array (FSA) system were viewed. In 70% (26) of cases, the maps supported the cushion recommended. In 25% (10) of the cases, the maps showed that the client's current seating surface was unsuitable. After viewing the pressure maps, a surface other than the client's current surface was recommended in 47% (19) of the cases. There was a lack of agreement between the risk level of the clients as identified by the Braden Scale score, and the risk level of the clients as identified by the occupational therapist using a decision tree and the FSA maps. CONCLUSION: Pressure mapping technology has a positive impact on clinical decisions regarding the provision of pressure-reducing cushions. Future research should examine the predictive validity of this technology. The Braden Scale may underpredict the risk level of the clients.

Activities of Daily Living↗
PubMed2004

Detection of resistance to gatifloxacin and moxifloxacin in Streptococcus pneumoniae with the VITEK 2 instrument.

A group of 72 pneumococcal isolates resistant or intermediate to levofloxacin and 124 pneumococcal isolates susceptible to fluoroquinolones were tested by the VITEK 2 instrument using investigational test cards and by a broth microdilution reference method. The VITEK 2 instrument performed well, detecting 52 of 60 (86.7%) gatifloxacin-resistant isolates and 22 of 23 moxifloxacin-resistant isolates, and did not falsely classify any susceptible isolates as resistant.

Anti-Infective Agents↗
PubMed2004

Detection of inducible clindamycin resistance of staphylococci in conjunction with performance of automated broth susceptibility testing.

This study has shown that inducible clindamycin resistance in staphylococci can be detected by disk testing on sheep blood agar inoculum purity plates used with the bioMerieux VITEK 2. Tests of 150 erythromycin-resistant isolates correlated with standard D-zone tests on Mueller-Hinton agar and with PCR for erm(A), erm(C), and msr(A).

Anti-Bacterial Agents↗
PubMed2003

Practical disk diffusion method for detection of inducible clindamycin resistance in Staphylococcus aureus and coagulase-negative staphylococci.

Resistance to macrolides in staphylococci may be due to active efflux (encoded by msrA) or ribosomal target modification (macrolide-lincosamide-streptogramin B [MLSB] resistance; usually encoded by ermA or ermC). MLSB resistance is either constitutive or inducible following exposure to a macrolide. Induction tests utilize closely approximated erythromycin and clindamycin disks; the flattening of the clindamycin zone adjacent to the erythromycin disk indicates inducible MLSB resistance. The present study reassessed the reliability of placing erythromycin and clindamycin disks in adjacent positions (26 to 28 mm apart) in a standard disk dispenser, compared to distances of 15 or 20 mm. A group of 130 clinical isolates of Staphylococcus aureus and 100 isolates of erythromycin-resistant coagulase-negative staphylococci (CNS) were examined by disk approximation; all CNS isolates and a subset of S. aureus isolates were examined by PCR for ermA, ermC, and msrA. Of 114 erythromycin-resistant S. aureus isolates, 39 demonstrated constitutive resistance to clindamycin, while 33 showed inducible resistance by disk approximation at all three distances. Only one isolate failed to clearly demonstrate induction at 26 mm. Of 82 erythromycin-resistant CNS isolates that contained ermA or ermC, 57 demonstrated constitutive clindamycin resistance, and 25 demonstrated inducible resistance, at 20 and 26 mm. None of the 42 S. aureus isolates or 18 CNS isolates containing only msrA and none of the erythromycin-susceptible isolates yielded positive disk approximation tests. Simple placement of erythromycin and clindamycin disks at a distance achieved with a standard disk dispenser allowed detection of 97% of S. aureus strains and 100% of CNS strains with inducible MLSB resistance in this study.

Anti-Bacterial Agents↗
PubMed2001

Identification of a 41 kDa protein embedded in the biosilica of scales and bristles isolated from Mallomonas splendens (Synurophyceae, Ochrophyta).

Cells of the photosynthetic protist Mallomonas splendens (Synurophyceae, Ochrophyta) are encased within a highly patterned wall or scale case that consists of silicified scales and bristles. In an effort to understand the mechanisms that unicellular protists utilize to produce elaborate, mineralized structures of great complexity and hierarchical structure, we identified and characterized a 41 kDa protein from purified scales/bristles isolated from M. splendens (SP41 for Scale Protein of 41 kDa). A cDNA encoding this protein was isolated and sequence analysis indicated that it is a novel protein. Polyclonal antibodies were generated against bacterially expressed SP41 and used to localize the protein throughout scale and bristle morphogenesis. Immunoelectron microscopy confirmed the biochemical data that SP41 is a component of mature scales and bristles, the protein localizing to silicified components of the purified extracellular matrix. During scale and bristle biogenesis within the cell, SP41 is deposited into a specialized Silica Deposition Vesicle (SDV) concomitant with silica deposition, a highly regulated event during scale and bristle formation. These results argue for SP41 playing a role in morphogenesis and/or silicification within the SDV during scale and bristle biogenesis.

Amino Acid Sequence↗
PubMed2000

The application of atomic force microscopy to topographical studies and force measurements on the secreted adhesive of the green alga Enteromorpha.

Atomic force microscopy (AFM) enables the topographical structure of cells and biological materials to be resolved under natural (physiological) conditions, without fixation and dehydration artefacts associated with imaging methods in vacuo. It also provides a means of measuring interaction forces and the mechanical properties of biomaterials. In the present study, AFM has been applied for the first time to the study of the mechanical properties of a natural adhesive produced by a green plant cell. Swimming spores of the green alga Enteromorpha linza (L.) J. Ag. (7-10 microm) secrete an adhesive glycoprotein which provides firm anchorage to the substratum. Imaging of the adhesive in its hydrated state revealed a swollen gel-like pad, approximately 1 microm thick, surrounding the spore body. Force measurements revealed that freshly released adhesive has an adhesion strength of 173 +/- 1.7 mN m(-1) (mean +/- SE; n=90) with a maximum value for a single adhesion force curve of 458 mN m(-1). The adhesive had a compressibility (equivalent to Young's modulus) of 0.54 x 10(6) +/- 0.05 x 10(6) N m-2 (mean +/- SE; n=30). Within minutes of release the adhesive underwent a progressive 'curing' process with a 65% reduction in mean adhesive strength within an hour of settlement, which was also reflected in a reduction in the average length of the adhesive polymer strands (polymer extension) and a 10-fold increase in Young's modulus. Measurements on the spore surface itself revealed considerably lower adhesion-strength values but higher polymer-extension values than the adhesive pad, which may reflect the deposition of different polymers on this surface as a new cell wall is formed. The study demonstrates the value of AFM to the imaging of plant cells in the absence of fixation and dehydration artefacts and to the characterisation of the mechanical properties of plant glycoproteins that have potential utility as adhesives.

Cell Adhesion↗
PubMed2000

Rapid automated antimicrobial susceptibility testing of Streptococcus pneumoniae by use of the bioMerieux VITEK 2.

The VITEK 2 is a new automated instrument for rapid organism identification and susceptibility testing. It has the capability of performing rapid susceptibility testing of Streptococcus pneumoniae with specially configured cards that contain enriched growth medium and antimicrobial agents relevant for this organism. The present study compared the results of testing of a group of 53 challenge strains of pneumococci with known resistance properties and a collection of clinical isolates examined in two study phases with a total of 402 and 416 isolates, respectively, with a prototype of the VITEK 2. Testing was conducted in three geographically separate laboratories; the challenge collection was tested by all three laboratories, and the unique clinical isolates were tested separately by the individual laboratories. The VITEK 2 results of tests with 10 antimicrobial agents were compared to the results generated by the National Committee for Clinical Laboratory Standards reference broth microdilution MIC test method. Excellent interlaboratory agreement was observed with the challenge strains. The overall agreement within a single twofold dilution of MICs defined by the VITEK 2 and reference method with the clinical isolates was 96.3%, although there were a number of off-scale MICs that could not be compared. The best agreement with the clinical isolates was achieved with ofloxacin and chloramphenicol (100%), and the lowest level of agreement among those drugs with sufficient on-scale MICs occurred with trimethoprim-sulfamethoxazole (89.7%). Overall there were 1.3% very major, 6.6% minor, and no major interpretive category errors encountered with the clinical isolates, although >80% of the minor interpretive errors involved only a single log(2) dilution difference. The mean time for generation of susceptibility results with the clinical isolates was 8.1 h. The VITEK 2 provided rapid, reliable susceptibility category determinations with both the challenge and clinical isolates examined in this study.

Anti-Bacterial Agents↗
PubMed2000

Revision of failed total hip arthroplasty with a proximal femoral modular cemented stem.

We have designed a modular cemented femoral component for revision of failed total hip arthroplasty in which deficiency of the proximal femur is such as to require a variable extrafemoral portion of the stem. We present the results of the first 74 operations in 72 patients; 56 of the patients had grade-3 or grade-4 femoral deficiency as defined by Gustilo and Pasternak and 24 had fractures of the proximal femur, of which 22 were periprosthetic. There was or had been infection in 19 hips. At a mean follow-up of 5 years 9 months (1 to 12 years) nine stems were radiologically loose of which three had been revised. There were no failures in 45 cases in which there was fixation of the distal stem of 10 cm or more. Dislocation occurred in nine patients and there were four cases of infection in the 19 which were, or had been, infected previously. There were no neurovascular complications and no intraoperative femoral fractures. The femoral bone stock improved radiologically in 45 hips of which 29 showed considerable reformation of the proximal femur; 27 remained unchanged and two showed increasing osteoporosis.

Adult↗
PubMed1998

Evaluation of the Dade MicroScan MICroSTREP antimicrobial susceptibility testing panel with selected Streptococcus pneumoniae challenge strains and recent clinical isolates.

The MicroScan MICroSTREP panel is a recently marketed frozen broth microdilution panel for susceptibility testing of various streptococci, including Streptococcus pneumoniae. The panel contains 10 antimicrobial agents in cation-adjusted Mueller-Hinton broth supplemented with 3% lysed horse blood, similar in concept to the National Committee for Clinical Laboratory Standards (NCCLS) reference broth microdilution method for testing streptococci. A group of 210 isolates of S. pneumoniae were selected to include isolates with previously documented resistance to agents incorporated in the MICroSTREP panel, as well as recent invasive clinical isolates. All isolates were tested simultaneously with the MICroSTREP panel and an NCCLS reference panel whose drug concentrations were prepared to coincide with those of the MICroSTREP panel. Of the 210 isolates, 5 failed to grow in the MICroSTREP panel; 3 of those also did not grow in the reference panel. Essential agreement of MICs determined by the two methods (test MIC +/- one dilution of the reference MIC) was 99.6% overall and ranged from 98.0% with chloramphenicol to 100% with penicillin, ceftriaxone, erythromycin, tetracycline, and vancomycin. There were no very major or major interpretive category errors resulting from the MICroSTREP panel tests. Minor interpretive category errors ranged from 12.2% with cefotaxime and 9.8% with ceftriaxone (due mainly to clustering of MICs for the selected strains near the breakpoints) to 0% with chloramphenicol and vancomycin. These results indicate that the MicroScan MICroSTREP frozen panels provide susceptibility results with pneumococci that are essentially equivalent to results derived by the NCCLS reference broth microdilution procedure.

Anti-Bacterial Agents↗
PubMed1992

Health survey methods with minority populations: some lessons from recent experience.

Until recently, minority populations have been inadequately or inaccurately represented in health research. Researchers are now recognizing the need to improve the validity and reliability of data on the health status and health-related behaviors of minorities. This paper discusses important methodological issues in conducting health survey research in minority communities: construction of an appropriate sampling frame, response rates, attrition from panel studies, and response patterns. These themes are illustrated with data from three field studies at the New England Research Institute. Two of these studies focus on inner-city Puerto Rican youth, a group rapidly increasing in size. The extent and multiplicity of problems experienced by this group affect the complexity of survey protocols. The third study is a random-digit-dial telephone survey on health care utilization for coronary heart disease by black and white adults from three inner-city neighborhoods in Boston. The conclusions drawn from the Institute's experience are corroborated by other scientific studies. First, the sociocultural characteristics of the community or group selected for study must be considered in planning and implementing any survey research on minority populations. Second, ensuring the quality of field work with minority groups may be expensive because of high residential mobility and lack of preexisting sampling frames. Third, there is no reason to expect any diminution of data quality with minority groups, provided the resources for data collection are adequate. The quality of data is undoubtedly proportional to the field efforts expended, but the costs of high-quality survey work are often not appreciated. The paper questions the utility of the term "minority research," for it disregards the considerable variation between and within minority groups and subcultures.

Black or African American↗
PubMed1988

Rimantadine prophylaxis in children: a follow-up study.

In a randomized, double-blind placebo-controlled clinical trial, we evaluated the prophylactic effectiveness of rimantadine in children (ages 1 to 18 years) against infection with influenza A (H3N2) and associated illness and the prevention of transmission of infection to adult members of the child's family. One hundred ten volunteers from 29 families completed this study during a naturally occurring outbreak of influenza A (H3N2). Influenza infections, defined as a positive viral throat culture or a 4-fold increase in antibody titer, occurred in 31.0% of children in the placebo group and 7.4% in the rimantadine group (P = 0.026). Clinical illness with laboratory evidence of influenza infection occurred in 24.1% of children in the placebo group and none in the rimantadine group (P = 0.007). Rimantadine was well-tolerated by the children, with no significant difference in reported adverse effects between the placebo and rimantadine groups. A combined analysis by families of these data and those of our similarly designed 1984 study, revealed that families in whom the children were given rimantadine had a significantly lower rate of influenza A infection and influenza-like illness compared with the families in whom the children were given placebo (68.8% vs. 18.8%, P less than 0.001) and (56.3% vs. 12.5%, P less than 0.001), respectively. We conclude that rimantadine prophylaxis of children appears to be an effective method to prevent influenza A (either H1N1 or H3N2) infection and illness in children.

Adamantane↗
PubMed1986

Effectiveness of rimantadine prophylaxis of children within families.

With recent studies suggesting that children are the main introducers of influenza infections into families, we conducted a placebo-controlled, double-blind, randomized trial to study the prophylactic effectiveness of rimantadine hydrochloride in children on the transmission of influenza A infections within families. One hundred forty-five volunteers from 35 families completed this study during a naturally occurring outbreak of influenza A (H1N1) infection. Influenza infections, defined as a positive viral throat culture or a fourfold increase in antibody titer, occurred in 31.7% of children in the placebo group and 2.9% of children in the rimantadine group. Clinical illness with laboratory evidence of influenza infection occurred in 17.0% of children in the placebo group and 0% of children in the rimantadine group. Rimantadine was well tolerated by the children, with no significant difference in reported side effects between the placebo and rimantadine groups. Influenza A infection occurred in 19.0% of adults whose children were receiving a placebo and 8.8% of adults whose children were receiving rimantadine. On the basis of our study, rimantadine prophylaxis of children appears to be an effective method to prevent influenza A infection in children. Additional studies are needed to demonstrate the effects of rimantadine prophylaxis of children on the incidence of influenza A infection in their parents.

Adamantane↗
PubMed1984

Collaborative evaluation of the Abbott Avantage system for identification of frequently isolated nonfermentative or oxidase-positive gram-negative bacilli.

The capability of the Abbott Avantage system to identify 10 species of commonly isolated glucose nonfermentative or oxidase-positive gram-negative bacilli in a 5-h test period was evaluated in a collaborative study. The Avantage nonenteric data base uses 20 biochemical test reactions performed in an expanded Abbott bacterial identification cartridge plus the results of a manual oxidase test. The species included in the Avantage data base are Acinetobacter anitratus, Acinetobacter Iwoffi, Aeromonas hydrophila, Flavobacterium meningosepticum-IIb group, Pseudomonas aeruginosa, Pseudomonas cepacia, Pseudomonas fluorescens-putida group, Pseudomonas maltophilia, Pasteurella multocida, and Plesiomonas shigelloides. The collaborative study included the testing of 200 coded challenge strains in all three laboratories and the subsequent testing of an additional group of 100 to 200 clinical isolates recovered independently by each laboratory. Reference identifications for all isolates were determined by conventional biochemical test reactions. The overall accuracy of identification of the coded challenge strains for the three laboratories was 97%, whereas 95% of 437 clinical isolates and selected stock cultures of clinical derivation were identified correctly.

Bacteria↗
PubMed1983

Ceftazidime levels in human breast milk.

Ceftazidime in the breast milk of 11 puerperal women were determined by bioassay. Each patient received 2 g of ceftazidime intravenously every 8 h for 5 days. The mean (+/- standard deviation) ceftazidime concentrations in the milk were: 3.8 +/- 2.0 (before the next dose), 5.2 +/- 3.0 (1 h after), and 4.5 +/- 1.7 micrograms/ml (3 h after). Ceftazidime was excreted in breast milk at relatively constant levels between days 2 and 4 of therapy.

Anti-Bacterial Agents↗