Strain dropouts reveal interactions that govern the metabolic output of the gut microbiome

The gut microbiome is complex, raising questions about the role of individual strains in the community. Here, we address this question by constructing variants of a complex defined community in which we eliminate strains that occupy the bile acid 7α-dehydroxylation niche. Omitting Clostridium scindens (Cs) and Clostridium hylemonae (Ch) eliminates secondary bile acid production and reshapes the community in a highly specific manner: eight strains change in relative abundance by >100-fold. In single-strain dropout communities, Cs and Ch reach the same relative abundance and dehydroxylate bile acids to a similar extent. However, Clostridium sporogenes increases >1,000-fold in the ΔCs but not ΔCh dropout, reshaping the pool of microbiome-derived phenylalanine metabolites. Thus, strains that are functionally redundant within a niche can have widely varying impacts outside the niche, and a strain swap can ripple through the community in an unpredictable manner, resulting in a large impact on an unrelated community-level phenotype.

Design, construction, and in vivo augmentation of a complex gut microbiome

Efforts to model the human gut microbiome in mice have led to important insights into the mechanisms of host-microbe interactions. However, the model communities studied to date have been defined or complex, but not both, limiting their utility. Here, we construct and characterize in vitro a defined community of 104 bacterial species composed of the most common taxa from the human gut microbiota (hCom1). We then used an iterative experimental process to fill open niches: germ-free mice were colonized with hCom1 and then challenged with a human fecal sample. We identified new species that engrafted following fecal challenge and added them to hCom1, yielding hCom2. In gnotobiotic mice, hCom2 exhibited increased stability to fecal challenge and robust colonization resistance against pathogenic Escherichia coli. Mice colonized by either hCom2 or a human fecal community are phenotypically similar, suggesting that this consortium will enable a mechanistic interrogation of species and genes on microbiome-associated phenotypes.

Scoliosis by acquired rib fusion after thoracotomy in infancy

This is a report of a 6-year-old boy who was operated upon twice for congenital esophageal atresia immediately after birth, via a right posteriolateral thoracotomy without rib excision, and at the age of 5 years developed a high left-convex thoracic scoliosis with Cobb angle of 15 degrees due to an unilateral acquired fusion between the dorsal ends of the fourth, fifth, and sixth ribs. The scoliosis had progressed by 5 degrees 1 year later. Although congenital scoliosis associated with rib fusion is a well known entity, to the authors' knowledge this is the first report of an acquired rib fusion producing progressive scoliosis.

Expandable nailing system for tibial shaft fractures

OBJECTIVE

To evaluate and present our current clinical experience in the treatment of closed and open tibial shaft fractures using the expandable intramedullary nailing system.

DESIGN

Prospective study.

SETTING

One level-1 trauma centre.

PARTICIPANTS

Twenty-six patients with acute tibial shaft fractures with at least 10 cm of intact cortex on both sides of the fracture.

INTERVENTION

Internal fixation using the Fixion expandable intramedullary nail (Disc-O-Tech Medical Technologies Ltd., Herzliya, Israel).

MAIN OUTCOME MEASUREMENTS

Operative and fluoroscopy time, healing time and perioperative complications were recorded.

RESULTS

Twenty-six tibial fractures were treated (OTA classification: 3 type A1, 8 A2, 8 A3, 3 B1, 3 B2, and 1 B3), six of which were open. All fractures healed by week 18.5 with an mean of 12.8+/-3.8 weeks. The operating time ranged from 20 to 50 min with an mean of 40+/-12.17 min. The fluoroscopy time ranged from 6 to 22s with a mean of 10+/-5s. In one case the nail failed to expand, as detected by X-ray control, and had to be exchanged intraoperatively. Two patients reported anterior knee pain during the follow up, but did not wish any further treatment. In a low demanding patient rotational malalignment was noted and no further action needed.

CONCLUSION

According to the results of this study, the use of the Fixion nailing system, where indicated, is associated with minimal complications and very good functional outcomes in fractures OTA types A and B. The advantages of the expandable nail include the decrease in the operating and fluoroscopy time and the simplicity of its application.

[Should a main coronary artery be dilated when the controlateral vessel is occluded?]

Angioplasty of the dominant left anterior descending or right coronary arteries when the controlateral artery is occluded may lead to major left ventricular dysfunction or cardiogenic shock. The authors assessed the results of angioplasty of a right coronary (n = 52) or left anterior descending (n = 141) artery stenosis when the controlateral artery was occluded and the left circumflex had no significant stenosis in 193 patients. The immediate and late (33 +/- 18 months) results were compared in 3 groups: the study group, a reference surgical group in which patients with comparable coronary lesions underwent double coronary artery bypass and a reference angioplasty group (n = 194) in which patients were treated by angioplasty of the right coronary and left anterior descending arteries. The left ventricular function of the study group was normal or midly abnormal in 72% of cases and moderately to severely abnormal in 28% of cases. During the hospital period, for the study group, there were 5.7% emergency coronary bypass procedures and 2.6% non-emergency bypass procedures, 1.6% of myocardial infarction and 0.5% deaths. After hospital discharge, the study group had 13.1% of coronary bypass procedures, 3.7% of myocardial infarcts and 4.7% deaths. The death and infarction rates were comparable in the 3 groups. The study group had a higher incidence of coronary bypass surgery in and after the hospital period than the control surgical group (p = 0.0.002). The authors conclude that dilatation of a main coronary artery when the controlateral artery is occluded is as safe as double coronary artery bypass surgery and angioplasty of the two vessels. Incomplete revascularisation in the study group did not affect survival rate without myocardial infarction compared with the angioplasty and surgical reference groups.

Adult idiopathic lumbar scoliosis. A formula for prediction of progression and review of the literature

STUDY DESIGN

A retrospective study was conducted of patients with untreated adult-type idiopathic lumbar scoliosis.

OBJECTIVES

To construct a mathematical formula that provides accurate progression of an idiopathic adult lumbar scoliosis using initial roentgenographic parameters.

SUMMARY OF BACKGROUND DATA

Osteoporosis, lateral spondylolisthesis of L2-L4, and degeneration of disc and joint may contribute to a poor prognosis for lumbar adult-type scoliosis.

METHODS

Seven roentgenographic parameters taken from the standing roentgenograms of 91 patients with a scoliosis of more than 10 degrees Cobb angle and who were included in a follow-up for more than 2 years, were put into a multiple regression analysis to observe the relative weight of each in the progression of the scoliosis.

RESULTS AND CONCLUSIONS

Only lateral spondylolisthesis of the apical vertebra, Harrington factor, and disc index were related to progression of the scoliosis. Using the mathematical formula, the real progression of lumbar scoliosis can be predicted within an average of 0.85 degrees +/- 3.76 degrees.

Complete fracture-dislocation of the thoracic spine without neurologic deficit: case report

A case is presented of a motorcyclist who crashed and suffered a fracture-dislocation of the mid-thoracic spine without any neurologic deficit. The injury was discovered 6 weeks after the crash. The patient underwent surgical stabilization and correction of the kyphotic deformity with Luque rods and sublaminar wires and had an uneventful recovery.

Refractory cardiogenic shock and complete heart block after unsuspected verapamil-SR and atenolol overdose

A 57-year-old female presented with complete heart block and then developed refractory hypotension despite temporary pacing. Moderate left ventricular dysfunction with focal wall motion abnormalities, as well as severe hypoxemia, were demonstrated. However, neither significant coronary disease nor evidence for pulmonary embolus or other lung disease could be determined. Hemodynamic stabilization was achieved with the use of an intra-aortic balloon pump and multiple high-dose pressor agents. A retrospective diagnosis of toxic verapamil-SR and atenolol ingestion was confirmed, and the patient gradually recovered. The relevant literature is reviewed and various treatment approaches are discussed.