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Biomedical subjects

A Featherstone

Publications and source records attributed to A Featherstone.

10 recordsLinked to original sources
PubMed2000

Investigation of the concentration of bacteria and their cell envelope components in indoor air in two elementary schools.

Bacterial cell envelope components are widely distributed in airborne dust, where they act as inflammatory agents causing respiratory symptoms. Measurements of these agents and other environmental factors are assessed in two elementary schools in a southeastern city in the United States. Muramic acid (MA) was used as a marker for bacterial peptidoglycan (PG), and 3-hydroxy fatty acids (3-OH FAs) were used as markers for Gram-negative bacterial lipopolysaccharide (LPS). Culturable bacteria were collected using an Andersen sampler with three different culture media. In addition, temperature (T), relative humidity (RH), and CO2 were continuously monitored. Concentrations of airborne MA and 3-OH FAs were correlated with total suspended particulate (TSP) levels. Outdoor MA (mean = 0.78-1.15 ng/m3) and 3-OH FA levels (mean = 2.19-2.18 ng/m3) were similar at the two schools. Indoor concentrations of airborne MA and 3-OH FAs differed significantly between schools (MA: 1.44 vs. 2.84 ng/m3; 3-OH FAs: 2.96 vs. 4.57 ng/m3). Although indoor MA levels were low, they were significantly related to teachers' perception of the severity of indoor air quality (IAQ) problems in their classrooms. Concentrations of CO2 correlated significantly with all bacteria measurements. Because CO2 levels were related to the number of occupants and the ventilation rates, these findings are consistent with the hypothesis that the children and teachers are sources of bacterial contamination. Many culturable bacteria present in indoor air are opportunistic organisms that can be infectious for compromised individuals, while both culturable and nonculturable bacterial remnants act as environmental toxins for both healthy and compromised individuals. Measuring the "total bacteria load" would be most accurate in assessing the biotoxicity of indoor air. Chemical analysis of MA and 3-OH FAs, when coupled with the conventional culture method, provides complementary information for assessing biocontamination of indoor air.

Air Microbiology↗
PubMed1995

A randomised comparison of meropenem with cefotaxime or ceftriaxone for the treatment of bacterial meningitis in adults. Meropenem Meningitis Study Group.

Third-generation cephalosporins are presently the agents of choice for the empirical antimicrobial therapy of bacterial meningitis. However, a number of factors associated with these agents, namely the development of resistance by pneumococci, limited activity against some Enterobacteriaceae and Pseudomonas spp., and the possible adverse effects of their bacteriolytic mode of action, indicate that newer classes of antimicrobial agents be evaluated for the treatment of bacterial meningitis. Meropenem is a carbapenem antibiotic which is highly active against the major bacterial pathogens causing meningitis, and penetrates well into the cerebrospinal fluid. Two prospective randomised studies in 56 adult bacterial meningitis patients have compared meropenem 40 mg/kg 8-hourly, up to a maximum of 6 g/day (n = 28) with cephalosporin treatment, i.e. cefotaxime (n = 17) or ceftriaxone (n = 11). Patients were assessed by neurological examination, Glasgow Coma Score and Herson-Todd score. Clinical cure was observed in all 23 evaluable patients treated with meropenem (100%) and with 17 of the 22 evaluable cephalosporin-treated patients (77%). All pre-treatment isolates were eradicated except one isolate of Staphylococcus aureus in a cefotaxime-treated patient. Neurological sequelae were noted in three meropenem and four cephalosporin-treated patients. No patients in either treatment group experienced seizures after the start of therapy. This was despite the fact that a patient in each group had experienced seizures before therapy, several had underlying CNS disorders, and that doses of 6 g/day of meropenem were given. Hearing impairment was recorded in 11 meropenem and nine cephalosporin treated patients. Three patients in the meropenem group and one in the cephalosporin group died during treatment for reasons unrelated to study therapy. Overall, the results of this study indicate that meropenem is an effective and well-tolerated antibiotic for the treatment of bacterial meningitis in adults.

Adult↗
PubMed1994

Presence of multiple genetic subtypes of human immunodeficiency virus type 1 proviruses in Uganda.

DNA sequences encoding the C2-V3 regions or the C2-V5 regions of the surface glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1) were amplified by the polymerase chain reaction (PCR) from peripheral blood mononuclear cells obtained in 1990/1992 from 20 infected Ugandans. The PCR-amplified DNA was cloned into a phagemid vector and between 1 and 12 clones from each provirus were sequenced. The Ugandan proviruses were aligned into four subtypes (A, B, C, and D) by phylogenetic analysis of consensus nucleotide sequences for the C2-V3 regions. Analysis of the deduced amino acid sequences of the C2-V3 regions by a maximum parsimony program gave a similar phylogenetic relationship. The data indicated that phylogenetic analysis of nucleotide and/or amino acid sequences from the C2-V3 regions is a reliable method of subtype determination. The consensus amino acid sequence of the subtype A and D proviruses were almost identical to those of the Albert et al. group B and group A proviruses, respectively. The deduced amino acid sequences of the C2-V5 regions of six of these proviruses showed considerable diversity both between patients and within patients. The region varied in length between 234 and 243 amino acids and included deletions and repetitions, particularly in the V4 region.

Adult↗
PubMed1993

Sequence analysis of the gp120 region of the env gene of Ugandan human immunodeficiency proviruses from a single individual.

DNA sequences encoding the surface glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1) were amplified by the polymerase chain reaction (PCR) from peripheral blood mononuclear cells obtained from a Ugandan AIDS patient. The PCR-amplified DNA was cloned into a phagemid vector and nine clones sequenced. The gp120 sequences of the proviruses were similar to that of the Zairian isolate HIV-JY1 and unlike that of another Ugandan provirus, U455. Six of the clones were closely related to each other (maximum nucleotide sequence divergence 1.9%), and had a V3 amino acid sequence similar to that frequently seen in recent isolates from Uganda. Two others formed a second group that diverged from the first by an average of 6.0% at the nucleotide level, resulting in a 12.5% divergence of amino acid sequence. These divergent clones had extensive amino acid sequence changes not only in the V3 region, which was highly atypical, but also in V1 and V4, and to a lesser extent in V2 and V5. A further proviral clone had a sequence intermediate between those of the other two groups of clones.

Acquired Immunodeficiency Syndrome↗
PubMed1993

The disposition and metabolic fate of 14C-meropenem in man.

1. The metabolism and pharmacokinetics of 14C-meropenem were studied in five volunteers who received 0.5 g (40 microCi) of the radiolabelled drug by i.v. infusion. 2. The maximum concentration of drug in plasma was 27 +/- 2 micrograms/ml (70 microM) corresponding to 98% of plasma radioactivity at the end of a 30 min infusion. The elimination half-life for meropenem in plasma was 1 h and meropenem remained the major radioactive component up to 6 h, but represented a decreasing proportion of the plasma radioactivity with time. One metabolite (the ring-open lactam) accounted for most of the remaining plasma radioactivity. The maximum concentration of metabolite was 1 +/- 0.1 micrograms/ml and the concentration of total radioactivity decreased to 2% of the peak value by 8 h. 3. Over the 5 days of the study, urinary excretion of radioactivity accounted for 99 +/- 0.5% dose, most of which was recovered in the first 8 h. There was negligible excretion in faeces. 4. Structural confirmation of the drug-related components in urine was accomplished by h.p.l.c.-mass spectrometry. Meropenem accounted for 71 +/- 2% dose of 14C and the ring-open lactam metabolite for most of the remainder, no other metabolites were detected. 5. Meropenem was the major radioactive component in urine up to 8 h after dosing and is therefore remarkably stable to human renal dehydropeptidase (DHP-1) compared with other carbapenems in clinical use.

Adult↗
PubMed1989

The disposition and metabolism of meropenem in laboratory animals and man.

The disposition and metabolism of meropenem were studied in rats, dogs and cynomolgus monkeys following intravenous administration of [14C]-meropenem, and also in man following intravenous infusion of meropenem. Following intravenous administration to rats and dogs, radioactive material was very rapidly and widely distributed in the tissues, with highest levels detected in the kidney and other highly perfused organs. Concentrations in all tissues decreased rapidly with time. The plasma elimination half-life of meropenem was approximately 6 min in rats, 30 min in monkeys, 45 min in dogs and 1h in man. In all species 90-100% of the dose was excreted via the urine within 24 h. Analysis of the radioactive material in urine from animal studies showed that the major components were unchanged compound (36-43%) and a metabolite corresponding to a beta-lactam ring-opened form (34-51%). In man, approximately 65% of the dose was excreted in urine as unchanged meropenem and most of the remainder as the ring-opened metabolite. As part of the preclinical safety evaluation programme of meropenem, the distribution, metabolism and excretion of [14C]-meropenem were studied in the rat, dog and cynomolgus monkey after single intravenous administration at dose levels corresponding to the lower doses used in toxicity studies. In addition, the metabolism and pharmacokinetics of meropenem in human volunteers were studied.

Animals↗
PubMed1989

The pharmacokinetics of meropenem in volunteers.

Two human volunteer studies were performed with meropenem: a dose proportionality study of 0.25, 0.5 and 1.0 g and a probenecid interaction study. Six volunteers took part in each study. Meropenem was generally well tolerated: One volunteer was withdrawn from the dose proportionality study because of looseness of stool and abdominal pain after a dose of 1.0 g. The plasma concentrations of meropenem were linearly related to dose. The half-life of meropenem was approximately 1 h and the urinary recovery of unchanged drug was 79%. In the presence of probenecid the plasma half-life of meropenem was increased by 33% but the urinary recovery was unaffected.

Adult↗
PubMed1989

A microbiological study of early caries of approximal surfaces in schoolchildren.

A cross-sectional epidemiological study has been undertaken to relate the bacterial composition of approximal dental plaque with the earliest stages of caries development in schoolchildren. Small samples of plaque were removed from multiple sites around the contact areas of 42 premolars extracted for orthodontic reasons from 29 schoolchildren (mean age = 13.5 yr). Caries diagnosis was based on polarized light microscopy and contact microradiography of thin sections cut through the sample sites. Fifty-seven percent of sites (37/60) showed histological evidence of demineralization. Both the isolation frequency and the mean percentage viable count of mutans streptococci and Actinomyces viscosus were higher at sites with early caries, although mutans streptococci could not be detected at 37% of sites with early caries. At these latter sites, the proportions of Veillonella were markedly reduced. Lactobacilli were rarely isolated and were never recovered from caries-free surfaces. Analysis of the data shows that the relationship between plaque bacteria and enamel is neither merely passive nor indifferent, and that particular stages of lesion formation may be associated with different combinations of bacteria.

Adolescent↗