The use of randomization tests to assess the degree of similarity in PFGE patterns of E. coli O157 isolates from known outbreaks and statistical space-time clusters

Using isolates from reported cases of Escherichia coli O157 from Alberta, Canada in 2002, we applied randomization tests to determine if cases associated with an outbreak or statistical space-time cluster had more similar pulsed-field gel electrophoresis patterns, based on Dice coefficients, than expected by chance alone. Within each outbreak and space-time cluster, we assessed the mean, median, 25th percentile, 75th percentile, standard deviation, coefficient of variation, and interquartile range of the Dice coefficients of each pairwise comparison among the isolates. To assess the statistical significance of measures of location (e.g. mean) and variation (e.g. standard deviation) we created randomization distributions using all isolates or only isolates from sporadic cases. We determined that randomization tests are an appropriate tool for evaluating the similarity among isolates from cases that have been linked epidemiologically or statistically. We found little difference between using all cases or only sporadic cases when creating our randomization distributions.     

Studies on levamisole--induced agranulocytosis

Widespread clinical trials of leavo-tetramisole (levamisole) as an immunopotentiating agent in rheumatoid arthritis, metastatic carcinoma, and immunodeficiency states have been complicated by agranulocytosis (AGC) in 2.5%-13% of patients. Other than a relationship with prolonged high dosage, very little is known regarding the pathogenesis of levamisole-induced AGC. Whereas leukoagglutination was negative, fluorochromatic microgranulocytotoxicity (GCY) tests were positive with serum from 10 of 10 acutely neutropenic patients. The antibody was IgM, reacted with 100% of unrelated granulocytes, but not with T or B lymphocytes. Some sera also reacted with monocytes and the myeloid cell line, K-562. Tests for antigen-antibody complexes or cold autoantibodies were negative. Although clinical evidence strongly suggests a haptene (drug) mechanism, in vitro mixing experiments were also negative. An alternative choice parallels the model of aldomet- induced Coombs'-positive hemolytic anemia. Finally, GCY first became positive 2-3 mo prior to the onset of AGC on two patients, suggesting the possibility of identifying those at risk well before the onset of neutropenia.     

Abnormal surfactant composition and activity in severe bronchiolitis

A prospective study of infants under 1 y of age, ventilated for severe viral bronchiolitis, was carried out in four paediatric intensive care units in order to study surfactant activity and composition in this condition. Lung lavage fluid from 24 infants with bronchiolitis, 19 with bronchiolitis and sepsis or cardiac failure and 12 controls were analysed by the “click test” for surfactant activity and for phospholipids. Surfactant activity was present in all controls, but in only 2 of the 24 infants with bronchiolitis alone. The presence of phosphatidylglycerol correlated perfectly with the click test, suggesting that reduced activity is due to changes in surfactant lipid composition. In those with bronchiolitis plus coexisting disease, surfactant activity and phosphatidylglycerol were absent in only half. Surfactant activity and phosphatidylglycerol re-appeared by extubation. Severe viral bronchiolitis is associated with an absence of surfactant activity and PG, which resolves by clinical recovery. Infants with coexisting conditions are not always surfactant deficient. Surfactant administration is likely to be beneficial, but requires a selective approach.     

Changing mortality and causes of death in infants 23–27 weeks' gestational age

OBJECTIVE: To contrast the mortality rates and changes in the causes of death of very preterm infants (23-27 weeks), before and after the introduction of exogenous surfactant in 1991, and to identify any preventable causes of death remaining in the 1990s. METHODOLOGY: This was a cohort study on consecutive preterm infants of 23-27 weeks' gestational age born in the Royal Women's Hospital, Melbourne, a level III perinatal centre. The infants were livebirths free of lethal anomalies from two distinct eras, 1983-90, and 1992-96, inclusive. The main outcome measures were mortality during the primary hospitalization and the causes of death before and after the introduction of exogenous surfactant in 1991. RESULTS: In 1983-90, 261 of 508 livebirths (51.4%) of 23-27 weeks' gestational age died, a significantly higher proportion than the 109 of 384 (28.4%) livebirths who died in the period 1992-96. The mortality rate fell significantly with increasing gestational age and was lower at each week of gestational age in 1992-96. More infants who died in 1992-96 were treated intensively in the neonatal intensive care unit (NICU). Of the group of infants who died or who were treated intensively in NICU, respiratory causes of death predominated. However, the causes of death changed over time. In 1992-96 proportionally fewer infants died from respiratory causes (1983-90, 82.5%; 1992-96, 60.0%; odds ratio (OR) 0.31, 95%; confidence interval (CI) 0.16-0.57), but more from septic causes (1983-90, 14.3%; 1992-96, 43.8%; OR 4.9, 95%; CI 2.6-9.2). CONCLUSIONS: As the mortality rate has fallen over time, respiratory causes of death have diminished, but septic causes of death have increased. Further advances in the use of exogenous surfactant and respiratory support may reduce respiratory deaths. Effective strategies to reduce nosocomial infections are urgently required.     

Host-parasite relationships in acute pyelonephritis

During a 1-year prospective study, a total of 15 patients (seven children and eight adults) were observed with acute nonobstructive pyelonephritis. P-fimbriated Escherichia coli was the causative pathogen in all 15 patients. The same serotype of E coli that was P-fimbriated was isolated from the vaginal introitus of 60% and from the fecal flora of 86% of these patients. The only host abnormality was moderate vesicoureteral reflux in 20% of the patients. Uroepithelial cells were isolated from the first morning-voided urine from patients, who had recovered from pyelonephritis, and from age-matched controls. Using fluorescein-labelled type 1 and P-fimbriated reference strains of E coli and fluorescence-activated cell sorting (FACS) analysis, we evaluated their ability to adhere to these uroepithelial cells. P-fimbriated E coli was more adherent than type 1 fimbriated E coli, and more P-fimbriated E coli adhered to the patients' cells. Our data show that both colonization with P-fimbriated strains of E coli and receptor availability are important in the pathogenesis of pyelonephritis.     

A new transtrochanteric approach to the hip

Summary This transtrochanteric approach to the hip maintains continuity between the greater trochanter and the vastus lateralis muscle, thereby preventing the gross displacement of the greater trochanter and preserving the branches of the lateral circumflex vessles to it. The procedure offers the advantages of easy exposure and a high rate of bony union between trochanter and femur. We have used the procedure in 189 consecutive operations; in only four cases did union between the bones not occur. The trochanter was never cranially displaced more than three cm, and even in the cases of non-union abductor power was good. Although we do not recommend trochanteric osteotomy for every case of total hip replacement, we suggest that the approach be used for cases where technical problems are anticipated.

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Résumé Cette voie d'abord trans-trochantérienne respecte la continuité entre grand trochanter et muscle vaste externe, permettant ainsi de prévenir les déplacements importants du grand trochanter et de respecter les branches des vaisseaux circonflexes qui lui sont destinées. Cette technique assure à la fois une bonne exposition et un risque minimum de non-consolidation: sur nos 189 patients, seuls 4 n'ont pas consolidé. Ces 4 patients, malgré leur pseudarthrose, ont une force d'abduction satisfaisante. Le déplacement du grand trochanter vers l'avant n'a jamais excédé trois cm. Bien que nous ne conseillions pas cette voie d'abord dans tous les cas, nous la préconisons chaque fois que des difficultés techniques paraissent à redouter.