Pathogenic Nocardia cyriacigeorgica and Nocardia nova Evolve To Resist Trimethoprim-Sulfamethoxazole by both Expected and Unexpected Pathways.

Nocardia spp. are Gram-positive opportunistic pathogens that affect largely immunocompromised patients, leading to serious pulmonary or systemic infections. Combination therapy using the folate biosynthesis pathway inhibitors trimethoprim (TMP) and sulfamethoxazole (SMX) is commonly used as an antimicrobial therapy. Not surprisingly, as antibiotic therapies for nocardiosis can extend for many months, resistance to TMP-SMX has emerged. Using experimental evolution, we surveyed the genetic basis of adaptation to TMP-SMX across 8 strains of Nocardia nova and 2 strains of Nocardia cyriacigeorgica By employing both continuous experimental evolution to provide longitudinal information on the order of changes and characterization of resistant endpoint isolates, we observe changes that are consistent with modifications of two enzymes of the folate biosynthesis pathway: dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) (FolP), with the mutations often being clustered near the active site of the enzymes. While changes to DHFR and DHPS might be expected, we also noted that mutations in a previously undescribed homolog of DHPS (DHPS2 or FolP2) that was annotated as being "nonfunctional" were also sufficient to generate TMP-SMX resistance, which serves as a cautionary tale for the use of automated annotation by investigators and for the future discovery of drugs against this genus. Additionally, folP2 overlapped glucosyl-3-phosphoglycerate synthase. Remarkably, an adaptive frameshift mutation within the overlapping region resulted in a new in-frame fusion to the downstream gene to produce a potentially new bifunctional enzyme. How a single potentially bifunctional DHPS2 enzyme might confer resistance is unclear. However, it highlights the unexpected ways in which adaptive evolution finds novel solutions for selection.

Body Temperature Modulates Infarction Growth following Endovascular Reperfusion.

BACKGROUND AND PURPOSE: The neuronal substrate is highly sensitive to temperature elevation; however, its impact on the fate of the ischemic penumbra has not been established. We analyzed interactions between temperature and penumbral expansion among successfully reperfused patients with acute ischemic stroke, hypothesizing infarction growth and worse outcomes among patients with fever who achieve full reperfusion. MATERIALS AND METHODS: Data from 129 successfully reperfused (modified TICI 2b/3) patients (mean age, 65 ± 15 years) presenting within 12 hours of onset were examined from a prospectively collected acute ischemic stroke registry. CT perfusion was analyzed to produce infarct core, hypoperfusion, and penumbral mismatch volumes. Final DWI infarction volumes were measured, and relative infarction growth was computed. Systemic temperatures were recorded throughout hospitalization. Correlational and logistic regression analyses assessed the associations between fever (>37.5°C) and both relative infarction growth and favorable clinical outcome (90-day mRS of ≤2), corrected for NIHSS score, reperfusion times, and age. An optimized model for outcome prediction was computed by using the Akaike Information Criterion. RESULTS: The median presentation NIHSS score was 18 (interquartile range, 14-22). Median (interquartile range) CTP-derived volumes were: core = 9.6 mL (1.5-25.3 mL); hypoperfusion = 133 mL (84.2-204 mL); and final infarct volume = 9.6 mL (8.3-45.2 mL). Highly significant correlations were observed between temperature of >37.5°C and relative infarction growth (Kendall τ correlation coefficient = 0.24, P = .002). Odds ratios for favorable clinical outcome suggested a trend toward significance for fever in predicting a 90-day mRS of ≤2 (OR = 0.31, P = .05). The optimized predictive model for favorable outcomes included age, NIHSS score, procedure time to reperfusion, and fever. Likelihood ratios confirmed the superiority of fever inclusion (P < .05). Baseline temperature, range, and maximum temperature did not meet statistical significance. CONCLUSIONS: These findings suggest that imaging and clinical outcomes may be affected by systemic temperature elevations, promoting infarction growth despite reperfusion.

Global health imaging curriculum in radiology residency programs: the fundamentals.

Recent advances in imaging technology have created new opportunities for medical imaging to improve health care in resource-restricted countries around the world. Radiology residents are increasingly interested in global health and imaging outreach, yet infrastructure and opportunities for international outreach are limited. With the recent change in the ABR exam schedule, residents now have more flexibility in the fourth year of training to pursue elective interests, including participation in global health projects. Creating a formalized global health imaging curriculum will improve the quality, quantity, and overall impact of initiatives undertaken by residents and their training programs. A curriculum is proposed that provides content, opportunities for global health project development, and established metrics for effective evaluation and assessment. Four components considered integral to a global health imaging curriculum are described: (1) global and public health education; (2) targeted travel medicine education; (3) basic imaging proficiency; and (4) practice attitudes and accountability. Methods are presented of differentiating curricula to increase applicability across the spectrum of training programs that vary in available resources. A blueprint is presented for formalizing a global health curriculum or elective rotation within a program, as well as a resource for residents, radiologists, and organizations to make a meaningful impact on global health.

Relationship between untreated and insulin-treated diabetes and vascular relaxation.

The effects of untreated and insulin-treated streptozotocin-induced diabetes on the ability of the rat aorta maximally contracted with either 10(-4) M phenylephrine (PE) or 70 mM KCl to relax in response to 10(-5) to 10(-2) M theophylline (Theo) were examined. No significant differences between Theo-induced relaxation of the PE-contracture in control, untreated diabetic and insulin-treated diabetic aortas were observed until 12 weeks after the induction of diabetes. Twelve weeks after the induction of diabetes, the untreated diabetic aortas exhibited less relaxation in response to Theo than did the controls. This diabetes-induced decrease in relaxation of the PE-contracture was not reversed by insulin-treatment. Diabetes increased the ability of the K-contracted aortas to relax in response to Theo 4 weeks after the induction of diabetes. This diabetes-induced increase in the Theo-induced relaxation of the K-contracture was reversed by insulin-treatment. Even though there was no difference in the sensitivity of the PE-contracted tissues to Theo, the K-stimulated tissues from the untreated diabetic animals were more susceptible to the relaxing effects of Theo than either the control or insulin-treated aortas. These results indicate that diabetes affects the ability of the vascular smooth muscle to relax in response to theophylline, depending on the length of time in the diabetic state, the type of stimulus (PE or KCl) and whether or not insulin-treatment is applied.