Negatively Regulated Aerobactin and Desferrioxamine E by Fur in Pantoea ananatis Are Required for Full Siderophore Production and Antibacterial Activity, but Not for Virulence.

Pantoea ananatis is an emerging plant pathogen that causes disease in economically important crops such as rice, corn, onion, melon, and pineapple, and it also infects humans and insects. In this study, we identified biosynthetic gene clusters of aerobactin and desferrioxamine E (DFO-E) siderophores by using the complete genome of P. ananatis PA13 isolated from rice sheath rot. P. ananatis PA13 exhibited the strongest antibacterial activity against Erwinia amylovora and Yersinia enterocolitica (Enterobacterales). Mutants of aerobactin or DFO-E maintained antibacterial activity against E. amylovora and Y. enterocolitica, as well as in a siderophore activity assay. However, double aerobactin and DFO-E gene deletion mutants completely lost siderophore and antibacterial activity. These results reveal that both siderophore biosynthetic gene clusters are essential for siderophore production and antibacterial activity in P. ananatis PA13. A ferric uptake regulator protein (Fur) mutant exhibited a significant increase in siderophore production, and a Fur-overexpressing strain completely lost antibacterial activity. Expression of the iucA, dfoJ, and foxA genes was significantly increased in the Δfur mutant background, and expression of these genes returned to wild-type levels after fur compensation. These results indicate that Fur negatively regulates aerobactin and DFO-E siderophores. However, siderophore production was not required for P. ananatis virulence in plants, but it appears to be involved in the microbial ecology surrounding the plant environment. This study is the first to report the regulation and functional characteristics of siderophore biosynthetic genes in P. ananatis. IMPORTANCE Pantoea ananatis is a bacterium that causes diseases in several economically important crops, as well as in insects and humans. This bacterium has been studied extensively as a potentially dangerous pathogen due to its saprophytic ability. Recently, the types, biosynthetic gene clusters, and origin of the siderophores in the Pantoea genus were determined by using genome comparative analyses. However, few genetic studies have investigated the characteristics and functions of siderophores in P. ananatis. The results of this study revealed that the production of aerobactin and desferrioxamine E in the rice pathogen P. ananatis PA13 is negatively regulated by Fur and that these siderophores are essential for antibacterial activity against Erwinia amylovora and Yersinia enterocolitica (Enterobacterales). However, siderophore production was not required for P. ananatis virulence in plants, but it appears to be involved in the microbial ecology surrounding the plant environment.

The Effect of Door-to-Diuretic Time on Clinical Outcomes in Patients With Acute Heart Failure.

OBJECTIVES: This study sought to examine the impact of door-to-diuretic (D2D) time on mortality in patients with acute heart failure (AHF) who were presenting to an emergency department (ED). BACKGROUND: Most patients with AHF present with congestion. Early decongestion with diuretic agents could improve their clinical outcomes. METHODS: The Korea Acute Heart Failure registry enrolled 5,625 consecutive patients hospitalized for AHF. For this analysis, the study included patients who received intravenous diuretic agents within 24 h after ED arrival. Early and delayed groups were defined as D2D time ≤60 min and D2D time >60 min, respectively. The primary outcomes were in-hospital death and post-discharge death at 1 month and 1 year on the basis of D2D time. RESULTS: A total of 2,761 patients met the inclusion criteria. The median D2D time was 128 min (interquartile range: 63 to 243 min), and 663 (24%) patients belonged to the early group. The baseline characteristics were similar between the groups. The rate of in-hospital death did not differ between the groups (5.0% vs. 5.1%; p > 0.999), nor did the post-discharge 1-month (4.0% vs. 3.0%; log-rank p = 0.246) and 1-year (20.6% vs. 19.3%; log-rank p = 0.458) mortality rates. Get With the Guidelines-Heart Failure risk score was calculated for each patient. In multivariate analyses with adjustment for Get With the Guidelines-Heart Failure risk score and other significant clinical covariates and propensity-matched analyses, D2D time was not associated with clinical outcomes. CONCLUSIONS: The D2D time was not associated with clinical outcomes in a large prospective cohort of patients with AHF who were presenting to an ED. (Registry [Prospective Cohort] for Heart Failure in Korea [KorAHF]; NCT01389843).

Clinical features of idiopathic restrictive cardiomyopathy: A retrospective multicenter cohort study over 2 decades.

Idiopathic restrictive cardiomyopathy (RCMP) has not been fully understood because this disease is difficult to diagnose. The present study aimed to assess the clinical profile and outcome of idiopathic RCMP from a multicenter cohort.This investigation is a retrospective study of consecutive patients with idiopathic RCMP at 10 centers in Korea between 1990 and 2010. We evaluated the clinical characteristics of the patients and prognostic factors associated with mortality using multivariate Cox proportional hazards regression analyses.The study included 53 patients (26 men, 49.1%). During a median follow-up of 1.7 years, 17 patients (32.1%) died and 5 patients (9.4%) received a heart transplant. The 5-year survival rate of the overall patients was 64.4% ±â€Š7.8%. In multivariable analyses, the predictors of mortality were tricuspid regurgitation (TR) ≥ moderate (hazard ratio [HR] 32.55, P < .001) and left ventricular end-diastolic diameter (LVEDD) (HR 0.85, P < .001).Idiopathic RCMP showed unfavorable prognosis. Advanced TR and lower LVEDD are independent adverse predictors of mortality in patients with idiopathic RCMP.

Airways are more reactive to histamine than to methacholine in patients with mild airway hyperresponsiveness, regardless of atopy.

BACKGROUND: The airway muscles from allergen-sensitized animals in vitro show a heightened response to histamine, but not to carbachol. This study investigated whether the airway responsiveness to histamine in vivo is comparable to that of methacholine in human subjects with varying degrees of atopy. METHODS: One-hundred-and-sixty-eight consecutive adult asthma patients or volunteers underwent bronchoprovocation tests to both histamine and methacholine after determining their blood eosinophil counts, serum total IgE levels and skin test reactivity to 10 common aeroallergens. RESULTS: The responsiveness to histamine was significantly related to that to methacholine (r=0.609, p<0.001), but many individuals with a negative methacholine test response showed a positive response to histamine. The histamine-bronchial reactivity index (BRindex) was significantly higher than the methacholine-BRindex in subjects with a positive response to none (n=69, p<0.01) or only one (n=42, p<0.001) of histamine and methacholine, while there was no significant difference in the subjects with positive responses to both of them (n=57). The histamine-BRindex was significantly higher than the methacholine-BRindex in the subjects with mild histamine hyperresponsiveness (n=58, 1.28+/-0.01 vs. 1.20+/-0.02, respectively, p<0.001). Both histamine and methacholine responsiveness was significantly related to the atopy markers. However, the histamine-BRindex/methacholine-BRindex ratio of the atopics was not significantly different from that of the non-atopics. CONCLUSIONS: The airway responsiveness to histamine is comparable to that of methacholine in the subjects with positive responses to both histamine and methacholine, but the airway responsiveness to histamine is greater than that to methacholine in those subjects with mild airway hyperresponsiveness, regardless of atopy.