The Biogeographic Histories of Pinus Edulis and Pinus Monophylla Over the Last 50,000 Years

Well-preserved pine needles found in fossil packrat middens document the biogeographic responses of pinyon pines to changing climates over the last 50,000 years. During the full glacial Wisconsinan (MIS2), Pinus monophylla (single-needle pinyon), Pinus edulis (Colorado pinyon), and P.edulis var. fallax (Arizona singleleaf pinyon) all grew along the southern portions of their current ranges. P. monophylla extended from the southern Sierra Nevada across the Mojave Desert to northwestern Arizona. P. edulis grew from northwestern Arizona across central Arizona to New Mexico and south to westernmost Texas. P. edulis var. fallax grew throughout what is now the Sonoran Desert of southern Arizona. Application of the modern climate requirements for these species suggest that winter precipitation at this time was at least 150% of modern, but also that summer precipitation may have been somewhat greater than today, at least at the northernmost end of the Gulf of California. During the Bølling and Allerød intervals P.edulis and P.edulis var. fallax quickly expanded northward over the Mogollon Rim of central Arizona into the Little Colorado River basin and northwestern Arizona. This northerly expansion of the fallax variety during the Allerød interval suggests that temperatures were warmer than most of the latest Wisconsinan and that summer precipitation was at least 120% of modern. After the rapid warming at the start of the Holocene (11.7ka), P.monophylla and P.edulis populations were reduced in extent as their retreating southerly stands were not immediately replaced by expansion into cooler regions. These populations slowly expanded 300-500km northward at rates between 20 and 60my-1, reaching some of their current northern limits only within the last millennium. Increases in temperature expected over the next several hundred years will result in a similar reduction in populations unless this warming is ameliorated by favorable increases in precipitation. The consistent needle anatomy and distributions of the three types relative to each other suggest that there has been little evolutionary change discernible from these needles over at least the last 25,000 years

1992. Initial Procalcitonin Level and Antibiotic Practice Patterns Among Patients with Acute Respiratory Infections

Abstract Background The utility of procalcitonin (PCT)-guided algorithms to decrease antibiotic use has been extensively studied in clinical trials. The guidance that PCT provides as it translates into real-world practice is unclear. This study aims to describe real-world antibiotic prescribing practices in relation to PCT in patients admitted to our US-based health system with acute respiratory infections. Methods Retrospective cohort study of 1,606 adults admitted within our US health system from January 1, 2016 to December 31, 2018 with a primary diagnosis of acute upper or lower respiratory infection with at least one PCT measurement. Antibiotic practice patterns were evaluated using pharmacy analytic information and antibiotic status to note antibiotics given prior to and 36 hours after PCT result. Analysis of discordance with initial PCT level was defined as continuing or starting antibiotics after a low PCT level (PCT ≤0.25 μg/L) and withholding or discontinuing antibiotics after a high PCT level (PCT &gt; 0.25 μg/L). Results Antibiotic prescription patterns after the result of initial PCT level are summarized in Table 1. Only 242 patients (15%) had more than one PCT-level checked. Overall, antibiotic discordance with initial PCT result was 45%; mostly attributed to continuing or starting antibiotics despite a low PCT level (77%). (Figure 1) There were 496 patients who were initially started and continued on antibiotics despite a low PCT result. Of this subgroup, only one patient had a serial PCT measured, and 12 were admitted for Chronic Obstructive Pulmonary Disease (COPD) exacerbation and continued on azithromycin/doxycycline after result of the low PCT. Conclusion Utilization of antibiotics went against well-studied PCT cutoffs 45% of the time, primarily driven by antibiotic use at low PCT levels. Only a small number were continued on azithromycin/doxycycline for anti-inflammatory effect in COPD exacerbations, indicating that most patients received antibiotics for presumed bacterial infection despite the high negative predictive value of PCT. This study illustrates PCT use in real-world practice did not significantly alter prescribing practices, potentially from lack of confidence or knowledge in interpreting PCT results and lack of serial measurements to aid in decision-making. Disclosures All authors: No reported disclosures. </jats:sec