High temporal variability in airborne bacterial diversity and abundance inside single-family residences

Our homes are microbial habitats, and although the amounts and types of bacteria in indoor air have been shown to vary substantially across residences, temporal variability within homes has rarely been characterized. Here, we sought to quantify the temporal variability in the amounts and types of airborne bacteria in homes, and what factors drive this variability. We collected filter samples of indoor and outdoor air in 15 homes over 1 year (approximately eight time points per home, two per season), and we used culture-independent DNA sequencing approaches to characterize bacterial community composition. Significant differences in indoor air community composition were observed both between homes and within each home over time. Indoor and outdoor air community compositions were not significantly correlated, suggesting that indoor and outdoor air communities are decoupled. Indoor air communities from the same home were often just as different at adjacent time points as they were across larger temporal distances, and temporal variation correlated with changes in environmental conditions, including temperature and relative humidity. Although all homes had highly variable indoor air communities, homes with the most temporally variable communities had more stable, lower average microbial loads than homes with less variable communities.

The effect of irregular breathing patterns on internal target volumes in four-dimensional CT and cone-beam CT images in the context of stereotactic lung radiotherapy

PURPOSE

Stereotactic lung radiotherapy is complicated by tumor motion from patient respiration. Four-dimensional CT (4DCT) imaging is a motion compensation method used in treatment planning to generate a maximum intensity projection (MIP) internal target volume (ITV). Image guided radiotherapy during treatment may involve acquiring a volumetric cone-beam CT (CBCT) image and visually aligning the tumor to the planning 4DCT MIP ITV contour. Moving targets imaged with CBCT can appear blurred and currently there are no studies reporting on the effect that irregular breathing patterns have on CBCT volumes and their alignment to 4DCT MIP ITV contours. The objective of this work was therefore to image a phantom moving with irregular breathing patterns to determine whether any configurations resulted in errors in volume contouring or alignment.

METHODS

A Perspex thorax phantom was used to simulate a patient. Three wooden "lung" inserts with embedded Perspex "lesions" were moved up to 4 cm with computer-generated motion patterns, and up to 1 cm with patient-specific breathing patterns. The phantom was imaged on 4DCT and CBCT with the same acquisition settings used for stereotactic lung patients in the clinic and the volumes on all phantom images were contoured. This project assessed the volumes for qualitative and quantitative changes including volume, length of the volume, and errors in alignment between CBCT volumes and 4DCT MIP ITV contours.

RESULTS

When motion was introduced 4DCT and CBCT volumes were reduced by up to 20% and 30% and shortened by up to 7 and 11 mm, respectively, indicating that volume was being under-represented at the extremes of motion. Banding artifacts were present in 4DCT MIP images, while CBCT volumes were largely reduced in contrast. When variable amplitudes from patient traces were used and CBCT ITVs were compared to 4DCT MIP ITVs there was a distinct trend in reduced ITV with increasing amplitude that was not seen when compared to true ITVs. Breathing patterns with a rest period following expiration resulted in well-defined superior edges and were better aligned using an edge-to-edge alignment technique. In most cases, sinusoidal motion patterns resulted in the closest agreements to true values and the smallest misalignments.

CONCLUSIONS

Strategies are needed to compensate for volume losses at the extremes of motion for both 4DCT MIP and CBCT images for larger and varied amplitudes, and for patterns with rest periods following expiration. Lesions moving greater than 2 cm would warrant larger treatment margins added to the 4DCT MIP ITV to account for the volume being under-represented at the extremes of motion. Lesions moving with a rest period following expiration would be better aligned using an edge-to-edge alignment technique. Sinusoidal patterns represented the ideal clinical scenario, reinforcing the importance of investigating clinically relevant motions and their effects on 4DCT MIP and CBCT volumes. Since most patients do not breathe sinusoidally this may lead to misinterpretation of previous studies using only sinusoidal motion.

Disability management in a sample of Australian self-insured companies

PURPOSE

Disability management (DM) is a term developed in North America and refers to the prevention and management of injury and illness in the workplace. The purpose of this paper is to report findings of an Australian study that examined whether self-insured employers in that country have implemented integrated DM programmes. Key principles underpinning such programmes are explored to identify the extent to which Australian employers have adopted them.

METHOD

Data was collected from 29 self-insured Australian companies in three Australian States using a structured interview format with additional open-ended questions.

RESULTS

It was found that companies have in place, to varying degrees, some of the key elements of disability management programmes. However, these elements were often not well integrated in a comprehensive disability management approach. The focus on workplace-based, early intervention in the area of return to work for injured employees was particularly strong, but there was little evidence of formal labour-management committee structures responsible for implementing DM programmes.

CONCLUSIONS

If the concept of DM is relevant to the Australian environment then this study would suggest that self-insured companies need to undertake further work to develop integrated approaches to preventing and managing disability in the workplace. Several limitations of this study are highlighted and it is concluded that further work in this area is needed.

Detection of K-ras gene mutations in non-neoplastic lung tissue and lung cancers

Oncogene and tumor suppressor gene mutations are candidate biomarkers for cancer risk assessment and lesion detection. The K-ras oncogene has previously been associated with non-small cell lung cancer (NSCLC), particularly adenocarcinomas in which reported rates of mutation have approached 30-40%. We have analyzed non-malignant lung tissue from patients with lung cancer and primary lung cancers for K-ras gene mutations. Mutations were detected in 32% cancers and 29% non-malignant lung tissue from patients with cancer. The majority of tumors testing positive were adenocarcinoma of the lung. Normal DNA controls, including peripheral blood lymphocytes and normal lung from non-smokers, were negative. The ability to detect genetic alterations in non-malignant lung tissues is consistent with the concept that genetic alterations are involved in field cancerization of the aerodigestive tract.

Lack of an association between the presence of tumor necrosis factor or interleukin-1 alpha in the blood and weight loss among elderly patients

To determine the association between blood cytokine levels and body weight loss in elderly patients, serum levels of cachectin/tumor necrosis factor alpha (TNF) and interleukin-1 alpha (IL-1) were measured with specific and sensitive ELISA systems. Of the 19 healthy young subjects, two (10.5%) had detectable levels of serum TNF and one (5.3%) was positive for IL-1. In the healthy elderly group, two of the 12 subjects (16.7%) had measurable TNF levels and four (33.3%) had elevated IL-1 levels. Of the 61 ambulatory elderly patients, 31.1% had serum that contained TNF and 22.9% had IL-1. Similar proportions were found in 127 nursing home patients. None of the common diseases examined in this study nor any commonly used medications were associated with increased serum cytokine levels. Patients with weight loss of more than 5 lbs were less likely to have elevated serum TNF and IL-1 levels compared to the rest of the group. It is concluded that although elevated levels of TNF or IL-1 may occur more frequently in older groups, there is no evidence for a causal relationship between these circulating cytokines and clinically significant weight loss in the elderly.