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Biomedical subjects

R B Thomson

Publications and source records attributed to R B Thomson.

At least 37 records · Page 2Linked to original sources
PubMed1995

An outbreak of Pseudomonas aeruginosa ventilator-associated respiratory infections due to contaminated food coloring dye--further evidence of the significance of gastric colonization preceding nosocomial pneumonia.

An outbreak of ventilator-associated Pseudomonas aeruginosa respiratory infections in an intensive care unit of a teaching hospital was found to be associated with contaminated food coloring dye. Serotyping and bacteriocin typing indicated that the same strain of Pseudomonas was isolated from the food dye and from the respiratory cultures of the majority of patients. This observation lends credence to the importance of gastric colonization preceding pneumonia in ventilated patients.

Cross Infection↗
PubMed1995

Evaluation of BACTEC 9240 blood culture system by using high-volume aerobic resin media.

The BACTEC 9240 blood culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) is one of three automated, continuous-monitoring systems that is widely used in clinical laboratories. The BACTEC 9240 was compared with the BACTEC NR 660 for the detection of organisms and bacteremic episodes; time to detection of positive cultures; number of false-positive and false-negative cultures; and time needed to load, process, and perform quality control functions by using high-volume aerobic media. Blood specimens (5,282) were inoculated in equal volumes (5 to 10 ml per bottle) into BACTEC Plus Aerobic/F (9240 system) and BACTEC Plus NR26 (660 system) bottles. Clinically significant isolates were detected in 6.6% of cultures, representing 348 microorganisms and 216 bacteremic episodes. Two hundred forty-eight microorganisms were detected by both systems, 48 by the 9240 only and 52 by the 660 only (P = not significant). Of the bacteremic episodes, 158 were detected by both systems, 27 by the 9240 only and 31 by the 660 only (P = not significant). Analysis of data by month revealed equivalent recovery rates for both systems, with the exception of a 30-day period at one study site during which the 660 system detected significantly more microorganisms. Following a proprietary hardware design retrofit of the 9240 instrument, detection rates were again equivalent for the remaining three months at this study site. Positive cultures detected by both systems were detected an average of 4.3 h faster by the 9240 system (21 versus 25.3 h). The numbers of false-positive cultures for the 9240 and 660 systems were 40 (1.0%) and 9 ( < 1.0%), respectively. The numbers of false-negative cultures were five for the 9240 system and three for the 660 system. The 9240 system required 23 s less technologist time per bottle to operate during the 5-day protocol. In conclusion, the BACTEC 9240 used with high-volume Aerobic/F medium is equivalent to the BACTEC 660 used with high volume NR26 medium for the detection of microorganisms and bacteremic episodes. In addition, the 9240 system detects positive cultures more rapidly than the 660 system but requires further evaluation to ensure reliability of instrument components.

Automation↗
PubMed1994

Competition among hospitals in the United States.

The value added by acute-care hospitals is in the form of specific procedures (therapy, operations, testing) and the bed care necessary to make the procedures effective. When more than one hospital exists in a local area (defined in many studies as a radius of 15 mi/24 km) they compete for market share, since greater market share has a positive effect on economies of scale, utilization rates, learning curves and levels of quality. Competition is not only with other hospitals (and 75% of all hospitals do have a competitor within 24 km), but also with doctors who now perform some procedures in their offices, and with specialized clinics. The first strategy is to attract physician allegiance since they act as gate-keepers, directing patients to specific hospitals. This is done through personal amenities, professional amenities and enhancement to personal prestige and income. This competition for physician allegiance has a direct effect on utilization rates (doctors want spare capacity to suit their needs), on the range of services and facilities offered (doctors want more support), and on length of stay (doctors want longer stays). All of these increase the hospital's costs. The second strategy is to enter into contracts with third-party payers who will direct their clients to specific or preferred hospitals. The negative effect is that in competitive markets such payers may be able to bargain prices down. However, hospital differentiation makes it difficult for payers to make complete substitutions among them. As well, since the payers compete for clients, they often use hospital alliances as a selling point and therefore are often cooperative rather than confrontational in their negotiations. One tactic used by hospitals is to stress quality of service. But since quality in health care is hard to measure, patients are often unable to make direct assessments of alternatives. Hospitals therefore often 'signal' quality in various ways which may, and often do, increase hospital costs. (Some of these signals also attract physicians). Price is not a major element in competition. Most other strategies and tactics raise hospital costs and therefore price. Pressure from payers is turned back through differentiation (preventing substitution) and hospital-payer alliances for clients. Health care comes in too many packages to allow effective price competition. A final tactic is to increase the range of services or facilities offered. Enhanced services attract doctors by offering more support; attract some patients direct; and help to recapture market share lost to specialized clinics.(ABSTRACT TRUNCATED AT 400 WORDS)

Catchment Area, Health↗
PubMed1993

Emergence of antimicrobial resistance in gram-negative bacilli causing bacteremia during therapy.

Treatment of serious infections caused by gram-negative bacilli with beta-lactam antimicrobial agents can induce Class I beta-lactamase production. This phenomenon can result in resistant microorganisms, and has been postulated to be a cause of therapeutic failure. The charts of patients bacteremic with Pseudomonas aeruginosa, Serratia marcescens, Enterobacter cloacae, Citrobacter freundii, Proteus vulgaris, and Providencia species (n = 120) during a 3-year period were reviewed to determine how common the emergence of resistance was, and to determine if in vitro susceptibility testing was a reliable therapeutic guide. Emergence of resistance was believed to occur when a subsequent bacteremic isolate showed at least a fourfold increase in minimum inhibitory concentration accompanied by a change of interpretive susceptibility category. In the group of patients who survived at least 48 hours that received beta-lactam therapy (n = 76), one case of emergence of resistance was identified (1.3%). Emergence of resistance to beta-lactam antimicrobial agents did not commonly cause therapeutic failure at our institution, and susceptibility testing of gram-negative bacilli by usual methods was a reliable guide to antimicrobial therapy.

Anti-Bacterial Agents↗
PubMed1992

Adverse outcome in pregnancy following amniotic fluid isolation of Ureaplasma urealyticum.

Infections in pregnancy with Ureaplasma urealyticum have been associated with a wide range of adverse outcomes, such as early abortion, stillbirth, prematurity, and neonatal morbidity and mortality. Causality has been difficult to demonstrate secondary to the high prevalence of asymptomatic lower genital tract (LGT) colonization and culture data from inaccessible or potentially contaminated sites. Between 1985 and 1989, 2461 second-trimester genetic amniocenteses were evaluated at the cytogenetics section of the Children's Hospital Medical Center of Akron. All were cultured for the genital mycoplasmas: Mycoplasma hominis and Ureaplasma urealyticum. A total of nine patients were positive, all for Ureaplasma urealyticum, with one patient excluded because of subsequent therapeutic abortion. In addition, complete follow-up data, such as indication for amniocentesis, serum alpha-fetoprotein levels, gestational age at parturition, and outcome of pregnancy, were available on 86 Ureaplasma-negative (U-) patients during an approximate 2-year span within the time-frame of the study. This was in part due to physician response to a questionnaire sent after amniocentesis. Of the eight positive cultures, 100 per cent were associated with an adverse outcome, defined as fetal loss or premature delivery. This was significant compared with the U- group (p less than 0.001) with a more than eight times greater risk of adverse outcome. Six (75 per cent) resulted in spontaneous miscarriage within 4 weeks of amniocentesis and at less than 21 weeks' gestation. Two (25 per cent) delivered prematurely, with one (12.5 per cent) neonatal death at 24+ weeks. Histological examination of all eight placentae and the seven fetuses revealed a 100 per cent incidence of chorioamnionitis and pneumonia, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗
PubMed1992

Electrogenic proton secretion in the hindgut of the desert locust, Schistocerca gregaria.

The cellular mechanisms responsible for rectal acidification in the desert locust, Schistocerca gregaria, were investigated in isolated recta mounted as flat sheets in modified Ussing chambers. Previous studies conducted in the nominal absence of exogenous CO2 and HCO3- suggested that the acidification was due to a proton-secretory rather than bicarbonate-reabsorptive mechanism (Thomson, R.B., Speight, J.D., Phillips, J.E. 1988. J. Insect Physiol. 34:829-837). This conclusion was confirmed in the present study by demonstrating that metabolic CO2 could not contribute sufficient HCO3- to the lumen to account for the rates of rectal acidification observed under the nominally CO2/HCO3(-)-free conditions used in these investigations. Rates of luminal acidification (JH+) were completely unaffected by changes in contraluminal pH, but could be progressively reduced (and eventually abolished) by imposition of either transepithelial pH gradients (lumen acid) or transepithelial electrical gradients (lumen positive). Under short-circuit current conditions, the bulk of JH+ was not dependent on Na+, K+, Cl-, Mg2+, or Ca2+ and was due to a primary electrogenic proton translocating mechanism located on the apical membrane. A small component (10-16%) of JH+ measured under these conditions could be attributed to an apical amiloride-inhibitable Na+/H+ exchange mechanism.

Animals↗
PubMed1992

Difficulty in predicting bacteremia in elderly emergency patients.

STUDY OBJECTIVES: To characterize the clinical presentation and identify factors predictive of bacteremia in elderly patients. DESIGN: Retrospective review of emergency department charts, hospital records, and microbiology reports. SETTING: Community teaching hospital with annual ED census of 65,000 adults. PARTICIPANTS: Seven hundred fifty elderly patients (aged 65 to 99 years) who were evaluated by the emergency physician, had blood cultures obtained in the ED, and were hospitalized with a suspected infectious process during a 12-month period. MEASUREMENTS: Records were analyzed for demographic information, underlying diseases, clinical presentation, laboratory findings, sources of infection, and causative organisms. Using contingency tables, 79 patients with positive blood cultures were compared with a random sample of 136 patients with sterile blood cultures to identify clinical variables significantly (P less than .05) associated with bacteremia. Logistic regression analysis was performed with significant factors to develop a model to predict bacteremia. Sensitivity, specificity, and predictive values were calculated for the model. MAIN RESULTS: The prevalence of bacteremia was 10.6%. Escherichia coli was the most commonly isolated pathogen (29% of cases), and the urinary tract was the most common source of infection (44.3% of cases). Logistic regression analysis showed that altered mental status (odds ratio, 2.88; 95% confidence interval [Cl], 1.52 to 5.50), vomiting (odds ratio, 2.63; 95% Cl, 1.16 to 6.15), and WBC band forms of more than 6% (0.06) (odds ratio, 3.50; 95% Cl, 1.58 to 5.27) were independent predictors of bacteremia. The presence of at least one of these three factors had a sensitivity of 0.85 (95% Cl, 0.75 to 0.92) and a specificity of 0.46 (95% Cl, 0.38 to 0.55) for predicting bacteremia in the study group. The positive predictive value was 0.16 (95% Cl, 0.12 to 0.19) and the negative predictive value was 0.96 (95% Cl, 0.94 to 0.98) for the ED patient group that met inclusion criteria. CONCLUSION: Elderly patients fail to manifest identifiable clinical features indicative of bloodstream infection. The sensitivity and specificity of the best statistical model for identifying bacteremic elderly patients suggest that clinical indicators alone are unreliable predictors of bacteremia in the geriatric ED population studied.

Aged↗
PubMed1991

Ambulatory management of lower respiratory tract infections.

Clinical manifestations and radiographic findings are unreliable guides to the selection of antimicrobial therapy for lower respiratory infections. Laboratory evaluation is necessary to identify the etiologic agent. Multiple oral antibiotics are available for outpatient treatment of bronchitis or pneumonia suspected to be of bacterial origin.

Anti-Bacterial Agents↗
PubMed1990

Infections due to Corynebacterium group D2. Report of a case.

Corynebacterium group D2 is a gram-positive bacillus easily identified in clinical microbiology laboratories. However, this organism is often disregarded as a skin and mucous contaminant. The Spanish literature has recently described Corynebacterium group D2 as a urinary pathogen in a specific patient population. We report a case of Corynebacterium group D2 infection to illustrate the potential pathogenicity and clinical presentation of infection due to this organism in the United States.

Aged↗
PubMed1989

Repeat antimicrobial susceptibility testing of identical isolates.

Duplicate antimicrobial susceptibility test results were reviewed over a 1-year period to determine whether repeat testing of sequential isolates with the same identification from the same patient and specimen site was necessary. In our institution, repeat testing is always needed for coagulase-negative staphylococci and Pseudomonas aeruginosa and is needed after 3 days for members of the family Enterobacteriaceae, but it is not routinely necessary for Staphylococcus aureus.

Drug Resistance, Microbial↗
PubMed1988

NH4+ transport in acid-secreting insect epithelium.

The relationship between ammonia secretion (JAmm), hydrogen ion secretion (JH), and intracellular pH (pHi) was investigated in isolated locust (Schistocerca gregaria) rectal epithelia mounted as flat sheets in specially designed Ussing chambers. In the absence of exogenous CO2 and ammonia, the rectum is capable of net acid and ammonia secretion into the lumen against pH gradients of up to 1.8 U. JAmm was dependent on the presence of luminal amino acids and Na+ and it was relatively unaffected by K+ removal or changes in membrane potential. JAmm and pHi remained fairly constant over a luminal pH range of 7-5, whereas JH decreased linearly to zero over the same pH range. Mucosal addition of 1 mM amiloride reduced JAmm by 60%. This study demonstrates that the locust rectum secretes significant quantities of endogenously produced ammonia preferentially into the lumen as NH+4 rather than NH3. Moreover, the results suggest that the ammonia crosses the apical membrane via an amiloride-inhibitable Na+-NH+4 exchange mechanism.

Amiloride↗
PubMed1987

Evaluation of a commercially available cytomegalovirus-specific IgM test for the diagnosis of cytomegalovirus infection in the symptomatic newborn.

A commercially available (Electro-Nucleonics, Inc.) indirect fluorescent antibody test was evaluated for the detection of cytomegalovirus-specific IgM antibody in serum of newborn infants. The serum IgM fraction from 13 symptomatic newborns with cytomegalovirus infection and 30 control infants was tested. Seven of 13 infected infants and none of 30 control infants had a positive IgM test. This cytomegalovirus-specific IgM test is rapid and specific but lacks sensitivity.

Antibodies, Viral↗
PubMed1987

Yield, clinical significance, and cost of a combination BACTEC plus Septi-Chek blood culture system.

A blood culture was performed by adding a vented Septi-Chek bottle (Roche Diagnostics, Div. Hoffmann-LaRoche Inc., Nutley, N.J.) to a standard BACTEC system (Johnston Laboratories, Inc., Towson, Md.) blood culture. The yield of bacteremic patients, the clinical significance of organisms detected, and the cost of the combination system were compared with those of the standard BACTEC system alone. Each culture included 20 ml of blood divided among a BACTEC 6B aerobic bottle (5 ml), a BACTEC 7D anaerobic bottle (5 ml), and a Septi-Chek bottle equipped with a slide subculture attachment (10 ml). Significant isolates grew in 9.6% of the 2,269 cultures evaluated. The combination BACTEC plus Septi-Chek system detected 25% more bacteremic patients than the BACTEC system alone, 129 patients versus 103. The 26 bacteremic patients detected by only the added Septi-Chek bottle included 7 whose organism was isolated from blood alone and 19 whose organism was in mixed or pure culture from a second source. Detection of the organism resulted in alteration of antimicrobial therapy in 17 of these 26 patients. The combination system, which cultured a 20-ml blood volume, cost $11,000 more during the study period than the BACTEC system alone, which cultured a 10-ml volume. Reimbursement under the diagnosis-related group system was increased by $23,000 as a result of documentation of sepsis in these 26 patients. Blood volume and, possibly, the use of multiple blood culture systems are important factors when selecting a blood culture procedure for routine use.

Bacteriological Techniques↗
PubMed1986

In vitro susceptibility of the Bacteroides fragilis group in community hospitals.

The antimicrobial susceptibility of clinical isolates of the Bacteroides fragilis group was determined at six community hospitals (one large, greater than 600 beds; and five smaller, 96-325 beds). Imipenem was the most active beta-lactam with 100% of isolates being sensitive at 4 micrograms/ml. The percentage of isolates inhibited at 16 micrograms/ml (and 32 micrograms/ml) for the 7-alpha-methoxy antibiotics was: cefoxitin 66 (90); moxalactam 73 (85); cefotetan 68 (72); cefmetazole 40 (61). Metronidazole, chloramphenicol, and clindamycin were active against 100%, 100%, and 89% at breakpoints of 8 micrograms/ml, 8 micrograms/ml, and 4 micrograms/ml, respectively. The activity of several beta-lactams in our report differed slightly from that reported from university teaching hospitals. There were differences at many of the breakpoints for activity of some of the beta-lactam antibiotics for isolates from the large community hospital as compared with the combined isolates from the smaller community hospitals. Interestingly, the pattern was one of more resistance at the smaller community hospitals.

Anti-Bacterial Agents↗