Antibiotic U-20,661 was shown to inhibit predominantly deoxyribonucleic acid (DNA)-directed ribonucleic acid (RNA) synthesis by binding to the double-stranded DNA template. Specific binding to DNA was verified by difference spectroscopy, reversal of the RNA polymerase inhibitory effect by increasing concentrations of DNA template, and by moderately increasing the melting temperature of double-stranded DNA in the presence of the antibiotic. The RNA polymerase reaction primed with synthetic poly dAT was inhibited considerably, but not completely even with high concentrations of antibiotic. Thus, the agent might bind to adenine or thymidine or both bases in the double-stranded DNA helix.

ExtractWe have studied cardiac function and dynamics in 29 apparently normal children under 20 years of age. Table I lists the values obtained for intracardiac and great vessel pressures. There was no correlation of these pressures with either age or increasing body size. Except for the possibility that our data is inadequate for patients under one week of age, these pressures as well as the ratio between pulmonary artery mean to systemic artery mean (fig. l ) , appear to be constant throughout the pediatric age range. Arterio-venous differences ranged from 28 to 78 ml of 0,/1 of blood. The mean was 44.3 ml/l with a S.D. of 15.0.Left ventricular cavity diameters are shown for 11 normal children from our series and 9 patients from the literature (fig.4). The two measurements recorded in the youngest subjects are elevated, probably as a result of our inability to distinguish that area of left ventricular 'wall' occupied by the thymus. The ratio of the left ventricular cavity diameter to wall thickness was 7.0 ( fig. 5).Calculated systemic, total pulmonary and pulmonary arteriolar resistances appeared to be inversely related to age, height, and weight. Therefore, it seemed that non-linear regression formulae employing the inverse of age, height and weight would be more suitable (table 111). Height alone gave the best correlation with all cardiac functions except output.Calculated resistances for both systemic and pulmonary circulations fall with increasing age at approximately the same rate (figs. 6-8). As systemic blood flow increases to accommodate the needs of increasing body size, the denominator of the DC resistance term increases and 'resistance' decreases.Since in the absence ofshunts, pulmonary blood flow must parallel the increase in systemic blood flow, pulmonary 'resistance' decreases pari passu. SpeculationHigh speed digital computers now make the development of regression equations increasingly simple. These equations will be increasingly employed by clinical investigators in place of 'surface area'.I t is also obvious that calculated 'resistances' tell us far less about the vascular bed than was formerly believed. Input impedance calculation will be employed in the future, particularly as better methods for measuring instantaneous flow become available.

Objectives: To evaluate the prevalence of resistance of the various urinary tract infection (UTI) pathogens obtained from patients in an urban pediatric emergency department (PED), and to identify risk factors for infection with resistant strains. Methods: The data were collected retrospectively in an urban, academic PED in northeastern Florida. The microbiology-computerized database was used to identify all positive urine cultures from October 1999 through June 2000. All patients aged 17 years or less, whose urine specimen was collected in the ED and grew cultures with greater than 10,000 colony forming units (CFU) per milliliter of a single organism on Maconkey or blood agar, were included. The medical records of the patients were reviewed and selective demographic and clinical data were collected. Patients were excluded if their charts were unavailable for review or if the pathogen that grew in culture was a suspected contaminant. All patients lacking clinical symptoms of UTI (frequency, dysuria, abdominal pain, fever, or urgency) and whose urine was collected by clean-catch were excluded if their culture grew between 10,000 and 100,000 CFU. Resistance to trimethoprim-sulfamethoxazole (T-S) was estimated for the subset of gram-negative pathogens. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to compare rates of resistance among patients with and without the following risk factors: age greater than 4 years; current or recent antibiotic use; day care attendance; and previous UTI. Results: A total of 126 urine cultures were identified for inclusion. Of these, 45 patients were excluded, leaving 81 who met the study criteria. The majority of isolated organisms were Escherichia coli, accounting for 89% of the patients (n ¼ 72). Other organisms identified were Klebsiella 3.7%, Proteus 1.2%, Citrobacter 1.2%, Staphylococcus 1.2%, and Enterococcus 3.7% (all in children \ 4 years old). The resistance to T-S was 6.5% (95% CI ¼ 0.9% to 12.1%) for gram-negative pathogens. Overall, 48% of gram-negative isolates were resistant to one or more antibiotics, any resistance (95% CI ¼ 36.5% to 59.5%). T-S resistance was nominally higher for older children and for those with a history of antibiotic use, although not to a significant degree. Children less than age 4 were more likely to have any resistance (OR 2.6; 95% CI ¼ 1.0 to 6.7). Conclusions: The resistance to T-S in this study was 6.7% for gram-negative pathogens. These rates are lower than rates reported in adult populations, international pediatric studies, and the authors' hospital antibiograms, demonstrating the importance of local, population-specific data in selecting antibiotics. This study did not identify any statistically significant risk factors for resistance to T-S, but suggests that those with a recent history of antibiotic use may be at highest risk. While children less than 4 years old with gram-negative pathogens have nominally lower rates of T-S resistance, they are at higher risk for resistance to one or more antibiotics ...

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Objectives: To evaluate the prevalence of resistance of the various urinary tract infection (UTI) pathogens obtained from patients in an urban pediatric emergency department (PED), and to identify risk factors for infection with resistant strains. Methods: The data were collected retrospectively in an urban, academic PED in northeastern Florida. The microbiology-computerized database was used to identify all positive urine cultures from October 1999 through June 2000. All patients aged 17 years or less, whose urine specimen was collected in the ED and grew cultures with greater than 10,000 colony forming units (CFU) per milliliter of a single organism on Maconkey or blood agar, were included. The medical records of the patients were reviewed and selective demographic and clinical data were collected. Patients were excluded if their charts were unavailable for review or if the pathogen that grew in culture was a suspected contaminant. All patients lacking clinical symptoms of UTI (frequency, dysuria, abdominal pain, fever, or urgency) and whose urine was collected by clean-catch were excluded if their culture grew between 10,000 and 100,000 CFU. Resistance to trimethoprim-sulfamethoxazole (T-S) was estimated for the subset of gram-negative pathogens. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to compare rates of resistance among patients with and without the following risk factors: age greater than 4 years; current or recent antibiotic use; day care attendance; and previous UTI. Results: A total of 126 urine cultures were identified for inclusion. Of these, 45 patients were excluded, leaving 81 who met the study criteria. The majority of isolated organisms were Escherichia coli, accounting for 89% of the patients (n ¼ 72). Other organisms identified were Klebsiella 3.7%, Proteus 1.2%, Citrobacter 1.2%, Staphylococcus 1.2%, and Enterococcus 3.7% (all in children \ 4 years old). The resistance to T-S was 6.5% (95% CI ¼ 0.9% to 12.1%) for gram-negative pathogens. Overall, 48% of gram-negative isolates were resistant to one or more antibiotics, any resistance (95% CI ¼ 36.5% to 59.5%). T-S resistance was nominally higher for older children and for those with a history of antibiotic use, although not to a significant degree. Children less than age 4 were more likely to have any resistance (OR 2.6; 95% CI ¼ 1.0 to 6.7). Conclusions: The resistance to T-S in this study was 6.7% for gram-negative pathogens. These rates are lower than rates reported in adult populations, international pediatric studies, and the authors' hospital antibiograms, demonstrating the importance of local, population-specific data in selecting antibiotics. This study did not identify any statistically significant risk factors for resistance to T-S, but suggests that those with a recent history of antibiotic use may be at highest risk. While children less than 4 years old with gram-negative pathogens have nominally lower rates of T-S resistance, they are at higher risk for resistance to one or more antibiotics ...