Cognitive constraints influence an understanding of life-cycle change.

We investigated children's (n = 120; 3- to 11-year-olds) and adults' (n = 18) reasoning about life-cycle changes in biological organisms by examining their endorsements of four different patterns of life-span changes. Participants were presented with two separate tasks: (a) judging possible adult versions of a juvenile animal and (b) judging possible juvenile versions of an adult animal. The stimuli enabled us to examine the endorsement of four different patterns of change: identical growth, natural growth, dramatic change, and speciation. The results suggest that endorsement of the different patterns is influenced by age and familiarity. Young children and individuals confronted with unfamiliar organisms often endorsed an identical growth that emphasizes the stability of features over the life span and between parents and offspring. The results are interpreted as supporting the idea that cognitive constraints influence individuals' reasoning about biological change and that the influence of these constraints is most notable when individuals are young or are presented with unfamiliar biological organisms.

Bacteraemic urinary tract infection: management and outcomes in young infants.

OBJECTIVES: To determine predictors of parenteral antibiotic duration and the association between parenteral treatment duration and relapses in infants <3 months with bacteraemic urinary tract infection (UTI). DESIGN: Multicentre retrospective cohort study. SETTING: Eleven healthcare institutions across the USA. PATIENTS: Infants <3 months of age with bacteraemic UTI, defined as the same pathogenic organism isolated from blood and urine. MAIN OUTCOME MEASURES: Duration of parenteral antibiotic therapy, relapsed UTI within 30 days. RESULTS: The mean (±SD) duration of parenteral antibiotics for the 251 included infants was 7.8 days (±4 days), with considerable variability between institutions (mean range 5.5-12 days). Independent predictors of the duration of parenteral antibiotic therapy included (coefficient, 95% CI): age (-0.2 days, -0.3 days to -0.08 days, for each week older), year treated (-0.2 days, -0.4 to -0.03 days for each subsequent calendar year), male gender (0.9 days, 0.01 to 1.8 days), a positive repeat blood culture during acute treatment (3.5 days, 1.2-5.9 days) and a non-Escherichia coli organism (2.2 days, 0.8-3.6 days). No infants had a relapsed bacteraemic UTI. Six infants (2.4%) had a relapsed UTI (without bacteraemia). The duration of parenteral antibiotics did not differ between infants with and without a relapse (8.2 vs 7.8 days, p=0.81). CONCLUSIONS: Parenteral antibiotic treatment duration in young infants with bacteraemic UTI was variable and only minimally explained by measurable patient factors. Relapses were rare and were not associated with treatment duration. Shorter parenteral courses may be appropriate in some infants.

Blood culture time to positivity in febrile infants with bacteremia.

IMPORTANCE: Blood cultures are often obtained as part of the evaluation of infants with fever and these infants are typically observed until their cultures are determined to have no growth. However, the time to positivity of blood culture results in this population is not known. OBJECTIVE: To determine the time to positivity of blood culture results in febrile infants admitted to a general inpatient unit. DESIGN, SETTING, AND PARTICIPANTS: Multicenter, retrospective, cross-sectional evaluation of blood culture time to positivity. Data were collected by community and academic hospital systems associated with the Pediatric Research in Inpatient Settings Network. The study included febrile infants 90 days of age or younger with bacteremia and without surgical histories outside of an intensive care unit. EXPOSURES: Blood culture growing pathogenic bacteria. MAIN OUTCOMES AND MEASURES: Time to positivity and proportion of positive blood culture results that become positive more than 24 hours after placement in the analyzer. RESULTS: A total of 392 pathogenic blood cultures were included from 17 hospital systems across the United States. The mean (SD) time to positivity was 15.41 (8.30) hours. By 24 hours, 91% (95% CI, 88-93) had turned positive. By 36 and 48 hours, 96% (95% CI, 95-98) and 99% (95% CI, 97-100) had become positive, respectively. CONCLUSIONS AND RELEVANCE: Most pathogens in febrile, bacteremic infants 90 days of age or younger hospitalized on a general inpatient unit will be identified within 24 hours of collection. These data suggest that inpatient observation of febrile infants for more than 24 hours may be unnecessary in most infants.

Genetic analysis of a novel Xylella fastidiosa subspecies found in the southwestern United States.

Xylella fastidiosa, the causal agent of several scorch diseases, is associated with leaf scorch symptoms in Chitalpa tashkentensis, a common ornamental landscape plant used throughout the southwestern United States. For a number of years, many chitalpa trees in southern New Mexico and Arizona exhibited leaf scorch symptoms, and the results from a regional survey show that chitalpa trees from New Mexico, Arizona, and California are frequently infected with X. fastidiosa. Phylogenetic analysis of multiple loci was used to compare the X. fastidiosa infecting chitalpa strains from New Mexico, Arizona, and trees imported into New Mexico nurseries with previously reported X. fastidiosa strains. Loci analyzed included the 16S ribosome, 16S-23S ribosomal intergenic spacer region, gyrase-B, simple sequence repeat sequences, X. fastidiosa-specific sequences, and the virulence-associated protein (VapD). This analysis indicates that the X. fastidiosa isolates associated with infected chitalpa trees in the Southwest are a highly related group that is distinct from the four previously defined taxons X. fastidiosa subsp. fastidiosa (piercei), X. fastidiosa subsp. multiplex, X. fastidiosa subsp. sandyi, and X. fastidiosa subsp. pauca. Therefore, the classification proposed for this new subspecies is X. fastidiosa subsp. tashke.