Biomedical subjects

M L Wilson

Publications and source records attributed to M L Wilson.

At least 109 records · Page 6Linked to original sources

PubMed1993

Diagnostic utility of postmortem blood cultures.

The autopsy is receiving renewed emphasis as a tool for quality assurance in clinical medicine. Postmortem blood cultures frequently are taken during the autopsy but are costly and of unclear diagnostic utility. To assess whether postmortem blood cultures contribute any useful information not already known from antemortem blood cultures, we compared positive postmortem blood cultures taken in 111 autopsies with the results of antemortem blood cultures. Of these, 60 (54%) of 111 had positive postmortem blood cultures despite a cause of death not related to an infectious cause. Of the 111 patients, 54 (49%) had antemortem blood cultures drawn in the 7 days before death, of which 34 (63%) of 54 were negative and 20 (37%) of 54 were positive. Of the 20 patients with true antemortem bacteremia/fungemia, seven (35%) had postmortem blood cultures that yielded the same organism, 10 (50%) yielded multiple organisms that were considered to be contaminants, and three (15%) yielded different organisms. These latter three cultures yielded microorganisms that were related to the patients' illness but did not provide additional information not already known from antemortem blood cultures or the patients' clinical or autopsy findings. Of the 91 patients who had no, negative, or contaminated antemortem blood cultures, 69 (76%) had postmortem blood cultures that yielded contaminants and 22 (24%) yielded microorganisms that were indeterminate as a cause of sepsis and, therefore, did not yield new or useful information. In summary, results of postmortem blood cultures rarely, if ever, provide information that is not already known, can be interpreted, provide new insights into pathophysiology, or detect errors in therapy.

Autopsy↗

PubMed1992

Vegetation structure influences the burden of immature Ixodes dammini on its main host, Peromyscus leucopus.

To determine whether the relative abundance of immature Ixodes dammini (the vector of Lyme disease and human babesiosis) is related to habitat structure, we examined tick burdens on their main host, the white-footed mouse (Peromyscus leucopus), in 4 structurally diverse sites on Great Island, Massachusetts, USA. Vegetation structure at each site was quantified with respect to 25 habitat variables. Principal components analysis was used to reduce this set of habitat variables to seven new and orthogonal variables. Immature tick abundance varied widely among grids. Regression analysis of tick burdens on the habitat principal components showed that larval burdens were related strongly to the density of woody vegetation and negatively to herbaceous vegetation. Nymphal burdens were related negatively to herbaceous vegetation, but the relationship was not as strong as in the case of larvae. An experimental reduction in the abundance of white-tailed deer (Odocoileus virginianus), the main host of adult ticks, substantially reduced tick burdens and altered their relationships to habitat structure. Nymphal burdens were unrelated to habitat structure following deer removal. Manipulating habitat structure may have utility as a control strategy against this important vector.

Animals↗

PubMed1992

Trans-beta-farnesene as a feeding stimulant for the sand fly Lutzomyia longipalpis (Diptera: Psychodidae).

The aphid alarm pheromone, trans-beta-farnesene (TBF), was found to stimulate feeding in both male and female Lutzomyia longipalpis Lutz & Neiva. Four other structurally related compounds (farnesol; 808 farnesene; trans, trans-farnesyl acetate; farnesyl methyl ether) were slightly less stimulating to these insects. The effect of TBF varied with sand fly age and the concentration of the chemical used. In contrast, TBF did not stimulate feeding in either sex of four other sand fly species (L. shannoni Dyar, Phlebotomus papatasi (Scopoli), P. argentipes Annandale & Brunetti, P. perniciosus Newstead). TBF might be useful in enhancing L. longipalpis field collections or in developing a poison bait for the control of this species.

Animals↗

PubMed1992

Controlled evaluation of BACTEC PLUS 27 and Roche Septi-Chek anaerobic blood culture bottles.

Becton Dickinson Diagnostic Instrument Systems (Sparks, Md.) recently introduced BACTEC high-volume aerobic and anaerobic bottles that accept up to 10 ml of blood for use on their nonradiometric blood culture instruments. Both bottles contain 25 ml of tryptic soy broth, 0.05% sodium polyanetholesulfonate, and mixed resins. We compared the anaerobic bottle, designated BACTEC PLUS 27 (BP27), with the Roche Septi-Chek (RSC) Columbia broth anaerobic bottle in a collaborative evaluation at three university hospitals. A total of 5,152 adequately filled blood cultures were obtained from adult patients with suspected bacteremia or fungemia. Staphylococcus aureus was recovered significantly more often (P less than 0.03) from BP27 bottles alone; there were no other significant differences in yield. When microorganisms were recovered from both anaerobic bottles, growth was detected earlier in BP27 than it was in RSC (P less than 0.001), especially for S. aureus (P less than 0.001) and Staphylococcus epidermidis (P less than 0.02). We conclude that the yield from BP27 bottles is equivalent to or better (S. aureus) than that from RSC anaerobic bottles with Columbia broth and that speed of detection is superior with BP27 bottles.

Adult↗

PubMed1992

Application of rejection criteria for stool ovum and parasite examinations.

We retrospectively determined the yield of 2,015 stool ovum and parasite (O&P) examinations performed over an 11-month period. Two aspects were evaluated: the yield of positive results from multiple specimens per patient versus the result of a single examination, and the yield of positive results from stools submitted after 3 days of hospitalization. There were 131 (6.7%) positive O&P examinations from 75 patients: for 35 patients the single examination was positive; for 18, two of two examinations were positive; and for 15, three of three examinations were positive. The remaining seven patients had at least one negative examination in a series, but pathogenic intestinal parasites were detected in only three of these patients. Seventeen patients with positive O&P examinations were inpatients: seven of nine patients examined for O&P within 3 days of admission had stool specimens that contained recognized pathogens, in contrast to only two of eight patients examined after 3 days of hospitalization. After reviewing the data and informing hospital clinics, wards, and physicians, we instituted the following policy for screening stool specimens submitted for O&P examination. Only one O&P examination was performed for each outpatient visit and for inpatients hospitalized for 3 days or less, and examinations were not performed on stools submitted after 3 days of hospitalization unless the clinician arranged for the examination on the basis of clinical need. Over the 6-month follow-up period, 29.9% of O&P requests were rejected, 22% for patients in hospital for longer than 3 days and 7.9% for multiple O&P requests. Of 265 initially rejected specimens, 22 (8.3%) were examined after the referring physician contacted the laboratory. None of these specimens was positive. We conclude that eliminating O&P examinations of patients hospitalized for more than 3 days and initially performing only one examination per patient significantly reduces the number of examinations performed and reduces laboratory charges without adversely affecting patient care.

Adult↗

PubMed1992

Controlled comparison of the BacT/Alert and BACTEC 660/730 nonradiometric blood culture systems.

In a collaborative study at three university hospitals, the recovery of microorganisms and the speed of detection of microbial growth by the BacT/Alert (Organon Teknika Corporation, Durham, N.C.) and BACTEC 660/730 (Becton-Dickinson Diagnostic Instrument Systems, Sparks, Md.) nonradiometric blood culture systems were compared. A total of 5,918 comparisons were made between BacT/Alert aerobic and BACTEC NR 6A bottles and 5,992 comparisons were made between BacT/Alert anaerobic and BACTEC NR 7A bottles. Each bottle was inoculated with 5 ml of blood. The overall recoveries of microorganisms from the two aerobic bottles were comparable; members of the family Enterobacteriaceae were recovered more often from BacT/Alert aerobic bottles alone (P less than 0.001). The overall recoveries of microorganisms from the anaerobic bottles were not significantly different. Growth of Staphylococcus aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.01), streptococci (P less than 0.001), Escherichia coli (P less than 0.01), other members of the family Enterobacteriaceae (P less than 0.02), and Pseudomonas aeruginosa (P less than 0.05) was detected earlier in BacT/Alert aerobic bottles. Growth of S. aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.05), enterococci (P less than 0.01), Streptococcus pneumoniae (P less than 0.02), viridans group streptococci (P less than 0.05), E. coli (P less than 0.001), Klebsiella pneumoniae (P less than 0.01), and other members of the family Enterobacteriaceae (P less than 0.001) was detected earlier in BacT/Alert anaerobic bottles. In a system-versus-system comparison, more gram-positive cocci were recovered from the BACTEC system alone (P < 0.05), and more members or the family Enterobacteriaceae were recovered from the BacT/Alert system alone (P < 0.001). As a system, the BacT/Alert system detected growth of S. aureus (P < 0.001), coagulase-negative staphylococci (P < 0.01), streptococci (P < 0.001), E. coli (P < 0.001), other members of the familyEnterobacteriaceae (P < 0.001), and P. aeruginosa (P < 0.05) earlier than the BACTEC system did. Significantly fewer (40 versus 1,183) false-positive results occurred with the BacT/Alert system. We conclude that the BacT/Alert and BACTEC 660/730 nonradiometric systems are comparable for recovering clinically significant microorganisms form adult patients with bacteremia or fungemia, but that the BacT/Alert system detects microbial growth earlier than the BACTEC system does, with significantly fewer false-positive results.

Adult↗

PubMed1991

Issues in cerebrospinal fluid management. CSF Venereal Disease Research Laboratory testing.

Three policies for decreasing unnecessary cerebrospinal fluid (CSF) management Venereal Disease Research Laboratory (VDRL) tests were compared. The first policy attempted to educate physicians about the use of serologic tests for diagnosing neurosyphilis but allowed the CSF VDRL to be performed either as a screening test or as a retrospective test. The second policy required that the CSF VDRL be performed as a retrospective test without regard to the patient's serologic status. The third policy required that a patient be seropositive by either rapid plasma reagin (RPR) or fluorescent treponemal antibody absorbance (FTA-ABS) before a CSF VDRL could be performed. Before these policies were instituted, VDRL testing was performed on 18.2% of all CSF samples. The optional and required retrospective policies decreased the CSF VDRL rate to 13.0% and 8.5%, respectively, but the percentages of seropositive patients for whom these procedures were performed were only 7.3% and 12.9%. The third policy decreased the CSF VDRL test rate to 1.8% (P less than 0.001) with seropositivity improving to 90%. To assure serologic tests are obtained in the evaluation of neurosyphilis, requirement for seropositivity must be implemented with the use of retrospective CSF VDRL testing.

Antibodies, Bacterial↗

PubMed1991

Risk factors for Crimean-Congo hemorrhagic fever in rural northern Senegal.

The extent of infection among 722 residents of an enzootic focus of Crimean-Congo hemorrhagic fever (CCHF) virus in rural northern Senegal and putative modes of transmission were studied by a cross-sectional seroprevalence survey done from February through May 1989. Anti-CCHF virus IgG was found in 13.1% of 283 persons who completed a standard questionnaire and provided blood samples. Seropositivity rates were similar between sexes and increased significantly with age among nomadic persons. Behavior patterns providing exposure to multifactorial risk factors were gender-based. Male risk factors, primarily associated with herding activities, included sleeping outside during seasonal migrations (also a risk factor for nomadic women), bite by a tick (adult male Hyalomma truncatum), tick bite during the cool dry season, and contact with sick animals. Human infection of CCHF occurred more frequently or with less mortality in the region studied than has been found elsewhere in Africa; however, the rate of seroconversion-associated illness is undetermined. Hyalomma ticks appear to be the primary transmission mode.

Adolescent↗

PubMed1991

Controlled evaluation of BACTEC Plus 26 and Roche Septi-Chek aerobic blood culture bottles.

Blood culture bottles that accept up to 10 ml of blood have recently been introduced for the BACTEC nonradiometric blood culture system. The new formulation, designated BACTEC Plus, contains 25 ml of tryptic soy broth, 0.05% sodium polyanetholesulfonate, and mixed resins. In a collaborative study conducted at three university hospitals, we evaluated the BACTEC Plus 26 (BP26) aerobic bottle and the Roche Septi-Chek aerobic bottle with its agar slide paddle in 5,293 paired blood cultures. Significantly more microorganisms (P less than 0.001), especially Staphylococcus aureus (P less than 0.001), Staphylococcus epidermidis (P less than 0.01), enterococci (P less than 0.005), and members of the family Enterobacteriaceae (P less than 0.005), were detected by the BP26 bottle. When both bottles detected growth, BP26 did so earlier (P less than 0.001). In particular, S. epidermidis (P less than 0.001), streptococci (P less than 0.005), enterococci (P less than 0.05), and members of the family Enterobacteriaceae (P less than 0.001) were detected earlier by the BP26 bottle. We conclude that the BP26 bottle provides a yield and speed of detection of microorganisms superior to those of the Roche Septi-Chek aerobic blood culture bottle.

Adult↗

PubMed1991

Gastrointestinal cryptococcosis.

Cryptococcal infection of the gastrointestinal (GI) tract is rarely reported, either in disseminated disease or as an isolated finding. We report a case of gastric cryptococcal infection diagnosed by endoscopic biopsy as the initial presentation of the acquired immunodeficiency syndrome (AIDS), and an additional seven cases found by reviewing 23 other autopsy cases of disseminated or pulmonary cryptococcal infection. The patient with gastric cryptococcosis was a 38-year-old man who presented with symptoms of gastroesophageal reflux including odynophagia. Upper GI endoscopy showed Candida esophagitis and gastric nodules. Biopsy of the nodules revealed cryptococcal infection and granulomatous inflammation of the fundic mucosa and submucosa. The patient died 3 weeks later despite anti-fungal therapy. Autopsy revealed widespread cryptococcal infection involving the cecum but not the stomach, suggesting that the gastric lesions resolved with therapy. The sites of infection in the seven other cases were esophagus (three), stomach (one), terminal ileum (one), colon (three), gallbladder (one), and in a focus of Kaposi's sarcoma in the wall of the small bowel (one). Esophageal candidiasis was also present in two of the cases of esophageal cryptococcal infection. Predisposing factors were AIDS (3), hematologic malignancy (3), and corticosteroid therapy (1). In summary, we report a case of gastric cryptococcosis and conclude that cryptococcal infection involves the GI tract more commonly than has been previously reported, with 8/24 (33%) cases positive in our autopsy series. Of clinical significance is the observation that GI cryptococcal infection may be the initial presentation of disseminated disease in the immunocompromised patient, and cryptococcal infection of the esophagus may be found in the setting of esophageal candidiasis.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Determination of prostate gland volume by transrectal ultrasound: correlation with radical prostatectomy specimens.

Seventy six patients underwent transrectal ultrasound examination of the prostate prior to radical prostatectomy. All radical specimens were weighed and measured when freshly excised. Corresponding measurements calculated using transrectal ultrasound dimensions were retrospectively compared with those of the freshly excised glands. Estimation of gland volume by ultrasound measurement, utilizing the prolate ellipse formula [Width x Height x Length) x 0.70 was applied to a control group of 19 patients, and a close correlation (r = 0.77) between ultrasound estimated volume and actual weight was shown. A modified prolate ellipse formula, using the factor of 0.70, appears to be a more reliable means of estimating gland volume with transrectal ultrasound than the original formula [Width x Height x Length) x 0.523).

Aged↗

PubMed1990

Host-dependent differences in feeding and reproduction of Ixodes dammini (Acari: Ixodidae).

The frequencies with which adult Ixodes dammini Spielman, Clifford, Piesman and Corwin feed upon white-tailed deer (Odocoileus virginianus), raccoons (Procyon lotor), opossums (Didelphis virginiana), and domestic cats were compared in a wooded site in northeastern United States. By combining estimates of the quantity of ticks feeding on each host species with host densities, we derived the relative contribution made by each kind of host to the feeding of the tick population. To compare engorgement success and reproductive efficacy, we weighed ticks found on these hosts and compared tick weights with the quantity of eggs produced. Deer harbored the most female ticks per individual and, although deer were less abundant than raccoons, they harbored 94.6% of the feeding tick population. Raccoons, cats, and opossums, respectively, provided blood meals to 3.6, 1.6, and 0.2% of feeding adult ticks. Ticks engorged more successfully on cats and raccoons than on deer, and egg production correlated linearly with weight of female ticks collected from both cats and deer. Although these ticks engorged better on other hosts, the vast majority of eggs resulted from ticks that had fed on deer. We conclude that, in this site, the abundance of deer largely determines the abundance of I. dammini, the vector of the agent of Lyme disease.

Animals↗

PubMed1990

Microgeographic distribution of immature Ixodes dammini ticks correlated with that of deer.

In order to determine whether the small-scale distribution of immature Ixodes dammini Spielman et al. corresponds closely to the activity patterns of white-tailed deer, Odocoileus virginianus (Zimmerman), these relationships were examined in a site on Long Island, New York, U.S.A. We first determined the extent and temporal pattern of adult ticks feeding on deer by examining twenty-three resident deer tranquilized during September-December 1985. I. dammini adults infested deer throughout this fall period, most abundantly during October and November. With radio-telemetry collars attached to deer we determined the relative frequency that they occupied 0.25 ha quadrats of the study site. During the following summer, we examined white-footed mice, Peromyscus leucopus (Rafinesque), that inhabited these quadrats and removed immature ticks from each. 8975 larval and 163 nymphal I. dammini were removed from 208 mice trapped in forty-three such quadrats. The frequency of deer using these quadrats was positively correlated with both the number of larval and of nymphal ticks per mouse. These results suggest that risk of I. damminiborne zoonotic disease may be decreased by locally reducing deer density in sites that experience intense human activity.

Animals↗

PubMed1990

Co-overproduction and localization of the Escherichia coli motility proteins motA and motB.

The motility genes motA and motB of Escherichia coli were placed under control of the Serratia marcescens trp promoter. After induction with beta-indoleacrylic acid, the levels of MotA and MotB rose over about a 3-h period, reaching plateau levels approximately 50-fold higher than wild-type levels. Both overproduced proteins inserted into the cytoplasmic membrane. Growth and motility were essentially normal, suggesting that although the motor is a proton-conducting device, MotA and MotB together do not constitute a major proton leak. Derivative plasmids which maintained an intact version of motB but had the motA coding region deleted in various ways were constructed. With these, the levels of MotB were much lower, reaching a peak within 30 min after induction and declining thereafter; pulse-chase measurements indicated that a contributing factor was MotB degradation. The low levels of MotB occurred even with an in-frame internal deletion of motA, whose translational initiation and termination sites were intact, suggesting that it is the MotA protein, rather than the process of MotA synthesis, that is important for MotB stability. Termination at the usual site of overlap with the start of motB (ATGA) was not an absolute requirement for MotB synthesis but did result in higher rates of synthesis than when translation of motA information terminated prematurely. Even in the total absence of MotA, the MotB that was synthesized was found exclusively in the cytoplasmic membrane fraction. In wild-type cells, MotA was estimated by immunoprecipitation to be in about fourfold excess over MotB; a previous estimate of 600 +/- 250 copies of MotA per cell then yielded an estimate of 150 +/- 70 copies of MotB per cell.

Bacterial Proteins↗

PubMed1990

BacT/Alert: an automated colorimetric microbial detection system.

BacT/Alert (Organon Teknika Corp., Durham, N.C.) is an automated microbial detection system based on the colorimetric detection of CO2 produced by growing microorganisms. Results of an evaluation of the media, sensor, detection system, and detection algorithm indicate that the system reliably grows and detects a wide variety of bacteria and fungi. Results of a limited pilot clinical trial with a prototype research instrument indicate that the system is comparable to the radiometric BACTEC 460 system in its ability to grow and detect microorganisms in blood. On the basis of these initial findings, large-scale clinical trials comparing BacT/Alert with other commercial microbial detection systems appear warranted.

Bacteria↗

PubMed1990

Increased abundance, size, and longevity of food-deprived mosquito populations exposed to a fungal larvicide.

To determine whether the quantity of food available to mosquitoes in their aquatic environment limits the effectiveness of microbial pathogens as biological control agents, experimentally well-nourished and malnourished larval Aedes aegypti (Linn.) were exposed to graded inocula of the entomopathogenic fungus, Metarhizium anisopliae. First instar larvae were provided access either to 3 or to 5 mg of food, and lots from each food regimen were inoculated with 20, 40, 60, or 80 micrograms of fungal spores/ml water. Application of the fungus to well-nourished larvae reduced the proportion developing to the adult stage, and increased the size of those adults that developed; their survival was not affected. In the case of malnourished larvae, such applications appeared not to effect the proportion of larvae that matured, and, paradoxically, increased the size and longevity of these resulting adults. By destroying a portion of the larvae, the pathogen apparently reduced competition among malnourished larvae, thereby enhancing their survival, as well as the size of the resulting adults. Thus, biocontrol agents may fail when used as larvicides against such nutrient-deprived mosquitoes as frequently occur in nature.

Aedes↗

PubMed1990

Distribution of Crimean-Congo hemorrhagic fever viral antibody in Senegal: environmental and vectorial correlates.

The spatial pattern in Senegal of Crimean-Congo hemorrhagic fever (CCHF) virus IgG antibody prevalence in human and sheep was determined as was the relative abundance of potential tick vectors. A systematic, country-wide serological survey of sheep demonstrated that 10.4% of sheep exhibited IgG to CCHF virus. Sexes were infected equally. Antibody prevalence increased with age from 2.1% during the first year to 18.2% among sheep greater than or equal to 3 years of age. IgG prevalence was highest in the northern, arid Sahelian zone, averaging 75.7% seropositivity, and decreased to zero in the southern, moister Sudano-Guinean and Guinean zones. Human IgG prevalence ranged from 21% to less than 1% among the 8 sites that were sampled throughout the country, being greatest in the arid north and least in the south. Hyalomma ssp. ticks predominated in those biotopes where antibody prevalence was highest. The abundance of Hyalomma ticks may be the proximal determinant of endemic transmission.

Adult↗

PubMed1990

A multidisciplinary approach to information and critical appraisal instruction.

The formulation of clinical decisions based on evidence requires the ability to locate information and evaluate it critically. A ten-week critical appraisal course for third-year medical students, taught cooperatively by library and Department of Medicine faculty, integrates education in the selection, evaluation, and application of information to patient care. The course is distinctive in that information management skills are taught by a multidisciplinary team in a problem-based format as part of the compulsory medical curriculum. Medical faculty provided instruction in reading and evaluating research methodology, as well as statistical analyses in published reports, using clinical scenarios and related journal articles at weekly sessions. Library faculty provided instruction in locating pertinent research on a sample clinical problem using standard printed and computerized indexes and local library resources, and presented criteria for selecting the most useful and significant works from those retrieved. Library faculty also met individually with students to provide instruction in online literature searching. Based on formal evaluation and informal feedback, the course was well received; it effectively presents the literature search as an integral part of critical appraisal of the medical literature and of the clinical decision-making process.

Clinical Clerkship↗