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Biomedical subjects

W R Wilson

Publications and source records attributed to W R Wilson.

At least 271 records · Page 15Linked to original sources
PubMed1983

Cardiac valve replacement in patients with active infective endocarditis.

Since the introduction of effective antimicrobial therapy, the leading cause of death in patients with infective endocarditis is no longer sepsis but, rather, congestive heart failure. The mortality is higher in patients with severe heart failure due to infective endocarditis who are treated with medical therapy only than in those who additionally undergo cardiac valve replacement. The mortality is also higher in patients with severe heart failure due to aortic infective endocarditis (40 to 93%) than in those with heart failure due to mitral infective endocarditis (17 to 66%). In patients with and in those without infective endocarditis, surgical intervention can be carried out with comparable mortality not only for aortic valve replacement (9 vs 8.4%) but also overall for valve replacement (10 vs 12%). In patients with class IV heart failure, overall mortality of valve replacement was higher (17%) than in patients with class II (8%) or class III heart failure (7%) and, similarly, comparable with that of matched groups of patients without infective endocarditis. In patients with class IV disability, the mortality of valve replacement was higher in those with active infective endocarditis (19%) than in those with inactive infective endocarditis, possibly due to a higher incidence of sudden onset of severe aortic regurgitation and myocardial abscess. No patient with valve replacement for inactive infective endocarditis developed prosthetic valve endocarditis; a single case of prosthetic valve endocarditis occurred in a patient with active infective endocarditis. In general, early surgical intervention is preferable to procrastination in the management of patients with progressive or severe heart failure due to infective endocarditis. Although, in at least 70% of patients, blood cultures may be rendered sterile within one week of initiation of appropriate antimicrobial therapy, patients with infective endocarditis due to staphylococci, multiply-resistant gram-negative bacilli, fungi, Q-fever or those with myocardial abscess or multiple relapses may require surgical intervention. While the overall incidence of clinically apparent emboli has been reported to be as high as 30%, in a ten-year observation period at the Mayo Clinic, the rate was 5.6%. Patients with echocardiographic evidence of large or mobile vegetations and those with infective endocarditis cause by microorganisms associated with a high risk of embolization such as slow-growing fastidious gram-negative bacilli, fungi (especially Aspergillus) and nutritionally-variant viridans streptococci should be considered candidates for surgery irrespective of a history of emboli.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1983

Tetracyclines, chloramphenicol, erythromycin, and clindamycin.

The tetracyclines are active in vitro against many urinary tract pathogens such as Chlamydia, Mycoplasma pneumoniae, Brucella, rickettsiae, and Nocardia. Chloramphenicol is used primarily for anaerobic infections, Haemophilus influenzae meningitis, and infections due to Salmonella typhi. Erythromycin is active in vitro against M. pneumoniae, Legionella spp., Streptococcus pneumoniae, and group A beta-hemolytic streptococci; it may also be used as prophylactic therapy for subacute bacterial endocarditis and for recurrence of acute rheumatic fever in patients who are allergic to penicillin. Clindamycin should be used primarily for the treatment of anaerobic infections. The tetracyclines may cause gastrointestinal upset; phototoxic dermatitis; hepatitis, especially in pregnant women; discoloration of the teeth and bone dysplasia in the human fetus and in children; and superinfections, especially oral and anogenital candidiasis. The tetracyclines should be used with caution in patients with renal insufficiency. The most important toxic effect of chloramphenicol is bone marrow suppression, which is dose related or idiosyncratic. The incidence of undesirable side effects associated with the use of erythromycin is low; gastrointestinal irritation is the most common, and cholestatic hepatitis may occur with the use of erythromycin estolate. Pseudomembranous colitis is the most important toxic effect associated with the use of clindamycin.

Bacterial Infections↗
PubMed1983

Antimicrobial agents in patients with renal insufficiency.

The dosage or the time interval of administration (or both) of many antimicrobial agents must be adjusted in anephric patients or those with compromised renal function. Antimicrobial agents that must be adjusted include most but not all of the penicillins, the cephalosporins, the aminoglycosides, vancomycin, and trimethoprim-sulfamethoxazole. The maximal doses of these agents should be decreased in proportion to the reduction of renal function. The dosage of chloramphenicol, clindamycin, rifampin, oxacillin, and nafcillin probably need not be adjusted if hepatic function is essentially normal. The suggested doses are relatively crude guidelines to initial antimicrobial therapy. Administration of the initial dose should be followed by serum antimicrobial assays for accurate adjustment of the dosage. The efficacy of therapy and the possible occurrence of toxicity should be carefully monitored in all patients but particularly in those with renal insufficiency.

Adult↗
PubMed1982

The relationship of idiopathic sudden hearing loss to diabetes mellitus.

A diabetic subgroup identified from a base population who have experienced idiopathic sudden hearing loss (ISHL) has been studied. In order to assess the relationship between diabetes and ISHL, two non-diabetic control groups were formed, and a comparison of the audiological data between the diabetic and non-diabetic ISHL patient was made. Mean degree of hearing loss and recovery, as well as the mean hearing level of the contralateral ear were analyzed. No statistically significant differences were noted in the audiological pattern of ISHL in diabetics and controls. A similar incidence of recovery was noted for the two groups throughout the mid frequencies; however, diabetic ISHL patients fail to recover as well as in the high frequencies. Preliminary data, while not statistically significant, suggest an increased hearing loss in both the affected and unaffected ear of the older diabetic patient.

Adult↗
PubMed1982

Visual backward masking of selected visemes.

Five adult subjects with normal hearing and vision viewed tachistoscopically projected photographs of a talker uttering six phonemes. Experiment 1 determined discrimination of the visemes as a function of exposure duration (12-44 msec) and demonstrated that recognition of certain lip postures was a direct function of duration whereas for other postures duration appeared to interact with other variables. In Experiment 2, fixed duration stimuli (17 msec) were followed immediately by a variable duration masking stimulus (12-45 msec), and in Experiment 3 the test stimuli varied (22-52 msec) and the masking stimulus was fixed (45 msec). Results showed that under both conditions test stimuli were masked when the masker was at least as long as the test stimuli. In Experiment 4, the test stimuli and masking stimulus were held constant (15 msec and 45 msec, respectively) while a variable (7-37 msec) ISI was interposed. Delaying the masker did not improve recognition scores. Conclusions were (a) lip postures are subject to backward recognition masking and the effect varies in degree; (b) the processing of lip postures begins with a short-term storage of the posture; and (c) the initial stage of perceptual processing requires more than 37 msec. To the extent that this task parallels the speechreading process, the results would not support training procedures based at the level of single visemes.

Adolescent↗
PubMed1982

The antimicrobial removal device. A microbiological and clinical evaluation.

A parallel study of blood cultured conventionally and following processing in an Antimicrobial Removal Device (ARD) was conducted with patients suspected of being clinically bacteremic. Cultures yielded 205 isolates from 87 clinically bacteremic patients, of whom 28 were receiving antibiotics at the time their cultures were performed. Overall, ARD processing neither increased the isolation rate nor decreased the time interval required for detection of organisms compared with conventional processing. ARD processing was the only means of isolation of organisms from only seven of the 87 patients and three of the 28 receiving antibiotics, whereas conventional processing accounted for the only means of isolation of organisms from 17 of the 87 patients and nine of the 28 receiving antibiotics. ARD processing demonstrated no advantages over conventional processing of blood cultures.

Anti-Bacterial Agents↗
PubMed1982

Lack of in vivo and in vitro bactericidal activity of N-formimidoyl thienamycin against enterococci.

The minimal bactericidal concentrations of N-formimidoyl thienamycin (N-f-thienamycin) against 21 strains of enterococci isolated from patients with infective endocarditis were determined by macro- and microdilution methods. By a macrodilution technique with the minimal bactericidal concentration defined as greater than or equal to 99.9% killing of an initial inoculum, all 21 strains of enterococci were found to have minimal bactericidal concentration/minimal inhibitory concentration ratios of greater than or equal to 32. The mean minimal inhibitory concentration was 1.5 micrograms/ml (range, 0.5 to 4 micrograms/ml), and the minimal bactericidal concentration was greater than or equal to 128 micrograms/ml. The disparity between the results of our study and those published elsewhere, which reported that N-f-thienamycin is bactericidal in vitro against enterococci, may represent the relative insensitivity of the microdilution method in determining greater than or equal to 99.9% killing. The lack of in vitro bactericidal activity of N-f-thienamycin against enterococci was confirmed in vivo in the rabbit model of experimental endocarditis. N-f-Thienamycin was no more effective than penicillin alone in the treatment of experimental enterococcal endocarditis and was less effective than the combination of penicillin and gentamicin. The results indicate that N-f-thienamycin should not be used alone in the treatment of enterococcal endocarditis.

Animals↗
PubMed1982

Influence of gentamicin dose size on the efficacies of combinations of gentamicin and penicillin in experimental streptomycin-resistant enterococcal endocarditis.

We have evaluated the benefits of low versus high doses of gentamicin combined with procaine penicillin (1.2 X 10(6) U three times daily) in the treatment of streptomycin-resistant experimental enterococcal endocarditis in rabbits. The mean peak serum gentamicin concentration in animals treated with low-dose gentamicin (0.75 mg/kg three times daily) was 3.06 micrograms/ml (range, 2.1 to 4.2 micrograms/ml), and it was 8.05 micrograms/ml (range, 4.5 to 16.1 micrograms/ml) in animals treated with high-dose gentamicin (2 mg/kg three times daily). The mean log10 colony-forming units of enterococci per gram of cardiac valve vegetation in animals treated with procaine penicillin combined with low- or high-dose gentamicin were 2.4 +/- 1.2 and 1.4 +/- 1.3, respectively (P = not significant) after 3 days of treatment and 1.7 +/- 1.2 and 1.7 +/- 1.5, respectively (P = not significant), after 5 days of therapy. The median peak serum bactericidal titer was 1:8 in animals treated with low- or high-dose gentamicin. We detected no significant difference between low- or high-dose gentamicin combined with procaine penicillin in the efficacy of treatment of streptomycin-resistant experimental enterococcal endocarditis.

Animals↗
PubMed1982

Comparison of two methods used to prepare smears of mouse lung tissue for detection of Pneumocystis carinii.

The laboratory diagnosis of Pneumocystis carinii pneumonia in humans includes the identification of cysts in stained lung tissue impression smears. By using a mouse model, we compared the number of cysts in lung tissue impression smears with those contained in a concentrate of homogenized lung tissue. Eleven C3H/HEN mice developed P. carinii infection after corticosteroid injections, a low protein (8%) diet, and tetracycline administered in drinking water. Impression smears were prepared with freshly bisected lung tissue. Smears of concentrates were prepared with sediment from centrifuged lung tissue homogenates. All smears were made in duplicate, stained with toluidine blue O or methenamine silver, coded, randomized, and examined. The concentrate preparations contained more cysts per microscopic field than the impression preparations (P less than 0.01). Concentrates prepared by grinding with a mortar and pestle contained more cysts than concentrates prepared by blending with a Stomacher (P less than 0.05). Cysts were detected equally well with either the toluidine blue O or silver stain (not significant). Lung tissue concentrates were superior to lung tissue impressions for detecting P. carinii cysts in mice. Use of lung tissue concentrates should be considered for the diagnosis of human P. carinii infection.

Animals↗
PubMed1982

Management of complications of infective endocarditis.

Complications of infective endocarditis may be considered as those that involve the heart and adjacent structures or those that are extracardiac. Congestive heart failure is the most common serious complication of infective endocarditis and is the leading cause of death among patients with this infection. In patients with severe heart failure unresponsive to medical therapy after 24 to 48 hours, prompt cardiac valve replacement should be considered, irrespective of the duration of preoperative antimicrobial therapy. We believe that all patients with bacterial infective endocarditis who are stable hemodynamically and who have not had multiple large emboli should receive at least one course of antimicrobial therapy in an attempt to sterilize the infected valve before cardiac valve replacement is considered. Most patients with multiple major embolic events should undergo cardiac valve replacement or debridement of the infected valve. The technical limitations and the experience with two-dimensional echocardiography in patients with infective endocarditis who have valve vegetations demonstrated by echocardiography are not yet sufficient to justify cardiac valve replacement solely on the basis of echocardiographic findings. The highest frequency of major embolic events occurs in association with infections that produce large mobile valve vegetations, such as those caused by Haemophilus parainfluenzae and other slow-growing fastidious gram-negative bacilli, fungi (especially Aspergillus), and nutritionally variant viridans streptococci.

Aneurysm, Infected↗
PubMed1982

Experimental animal endocarditis.

The results of studies performed with animal models of experimental infective endocarditis have provided valuable information about the pathophysiology, natural history, and treatment of this infection. The Freedman rabbit model of experimental infective endocarditis is relatively simple to perform, is reproducible, and with minor modifications has become the standard model for the study of experimental endocarditis. The following are the major advantages of the Freedman model: (1) its relatively low cost and simplicity permit the study of large numbers of animals required for statistical analysis of results; (2) the model enables accurate control of the timing of the onset of infection, the administration of antimicrobial agents, and the duration of infection and treatment before the animal is killed; and (3) the experimental infection in rabbits histologically resembles the pathologic changes that occur in this infection in humans. This model has some disadvantages: (1) the artificially induced trauma to rabbit cardiac valves is different pathophysiologically from the conditions that predispose humans to infective endocarditis; (2) a larger inoculum of bacteria is required to produce infections in rabbits than that which causes human endocarditis; and (3) the rabbit model is a more severe, acute form of infection than human infective endocarditis, and survival of untreated animals for longer than 2 weeks is unusual. One should exercise considerable caution in extrapolating the results obtained from animal experimental infective endocarditis to human infection.

Animals↗
PubMed1982

Treatment of penicillin-sensitive streptococcal infective endocarditis.

Patients with infective endocarditis caused by penicillin-sensitive streptococci (minimal inhibitory concentration less than or equal to 0.1 microgram/ml of penicillin) may be treated successfully with one of the following three regimens: (1) aqueous penicillin G administered intravenously for 4 weeks, (2) aqueous penicillin G administered intravenously for 4 weeks in combination with streptomycin for the first 2 weeks of therapy, or (3) parenterally administered penicillin plus streptomycin for 2 weeks. No substantial difference in the relapse rate exists among the three regimens, and a cure rate of at least 98% may be anticipated with each of the three forms of therapy. The major advantage of the 2-week regimen is that it is more cost-effective than 4 weeks of hospitalization and therapy. The major disadvantage of the 2-week regimen and the 4-week regimen that uses streptomycin is the relatively low risk of streptomycin-associated vestibular toxicity. Patients unable to tolerate penicillin may be treated with vancomycin or a cephalosporin administered parenterally for 4 weeks.

Adult↗
PubMed1982

Symposium on infective endocarditis. III. Endocarditis due to gram-negative bacteria. Report of 56 cases.

At the Mayo Clinic, 56 patients with infective endocarditis caused by gram-negative bacteria were seen from 1958 through 1979, 35 of whom were seen from 1970 through 1979. The patients were categorized into two divisions: those with medical, naturally acquired valve infections (40 [71%]) and those with infective endocarditis after cardiac operation (16 [29%]). The overall cure rate was 82% (46 of 56 patients); 35 of 40 patients (88%) were cured in the medical group, and 11 of 16 patients (69%) were cured in the surgical group. The patients were further classified on the basis of organism: group 1 (33 patients)--infections caused by Haemophilus (18), Actinobacillus actinomycetemcomitans (4), Cardiobacterium hominis (6), Eikenella corrodens (2), Kingella kingii (2), and Bordetella bronchiseptica (1); 32 of these 33 patients (97%) were cured, and 6 of these infections were on prosthetic valves; group 2 (21 patients)--infections caused by enteric aerobic bacilli; 13 of the 21 patients (62%) were cured; group 3 (1 patient)--infection caused by anaerobes (Bacteroides fragilis); this patient died; and group 4 (1 patient)--infection caused by Neisseria gonorrhoeae; this patient was cured. The gram-negative bacteria in the survivors and nonsurvivors and the curative antibiotic regimens were tabulated. Among the 35 survivors in the medical group, a combined antibiotic regimen cured 21 patients (60%) and a single antibiotic agent cured 14 (40%). Among the 11 survivors in the surgical group, combined therapy was given to 8 (73%), a single drug was used once, and operation alone achieved a cure in 2 patients. Compared with past data, the current study indicates an increasing incidence of gram-negative bacterial endocarditis (approximately 10%) and an improving cure rate 82%).

Anti-Bacterial Agents↗
PubMed1982

Prosthetic valve endocarditis.

Prosthetic valve endocarditis is an infrequent but serious complication of cardiac valve replacement. The overall frequency of prosthetic valve endocarditis is approximately 2%. The frequency of early-onset and late-onset infections is 0.78% and 1.1%, respectively. Staphylococci are the most common isolate from patients with early-onset infection, accounting for 47.5% of the total number of isolates. Staphylococcus epidermidis causes 27% of these staphylococcal infections. Among patients with late-onset infection, streptococci are the predominant microorganism, constituting 42% of the total number of isolates from patients in this group. The overall mortality among patients with prosthetic valve endocarditis is high--59%; the mortality among patients with early- or late-onset infections is 77% and 46%, respectively. Most patients with staphylococcal prosthetic valve endocarditis should undergo cardiac valve replacement in addition to antimicrobial therapy. Closely monitored anticoagulant therapy should be cautiously continued in patients with prosthetic valve endocarditis.

Anti-Bacterial Agents↗
PubMed1981

An immunological assessment of patients with anorexia nervosa.

Patients with most forms of protein-calorie malnutrition are typically more susceptible to infection. We studied the immunological consequences of a subgroup of malnourished subjects--nine patients with anorexia nervosa, who typically have a lower incidence of infection. The profiles of the patients with anorexia nervosa deviated from the reported typical profile of significantly depressed cell-mediated immunity in subjects with more common forms of protein-calorie malnutrition, demonstrating normal T-lymphocyte populations and unimpaired proliferative lymphocyte responsiveness to mitogenic stimulation with phytohemagglutinin and concanavalin A. In fact, mitogen responsiveness was significantly elevated above that of controls, and with nutritional repletion, this enhanced responsiveness regressed toward control values. Since impaired cell-mediated immunity has been consistently documented in other malnourished populations, and presumably contributes to their increased propensity toward infection, the maintenance of a relatively intact cell-mediated immune system may be an important factor separating the malnourished anorexia nervosa patient from other protein-calorie malnourished patients.

Adolescent↗
PubMed1981

Rhinoscleroma with exophthalmos: a case report.

This is a report of a 20-year-old Nigerian man with a 15-year history of exophthalmos and nasal blockage caused by rhinoscleromatous. The diagnosis was made by histopathological examination of a biopsy specimen taken from the nasal passages. Despite protracted antibiotic therapy the patient experienced recurrent exophthalmos. Computerised axial tomography and sinus films showed the lesion to have invaded through the sinus passage into the orbit. Further histopathological examination of tissue removed at the time of surgical decompression also revealed rhinoscleroma. This appears to be the third report of rhinoscleromatous spread to the orbit.

Adult↗
PubMed1981

Management of nasal septal abscess.

Nasal septal abscesses are uncommon. Sixteen cases from the Massachusetts Eye and Ear Infirmary were reviewed retrospectively and are presented. The diagnosis, bacteriology, and pathophysiology are discussed. Immediate therapy is indicated to avoid cosmetic deformity or intracranial infection. Treatment is based on diagnostic needle aspiration, antibiotic coverage and surgical drainage.

Abscess↗