Daylight exposure modulates bacterial communities associated with household dust.

BACKGROUND: Microbial communities associated with indoor dust abound in the built environment. The transmission of sunlight through windows is a key building design consideration, but the effects of light exposure on dust communities remain unclear. We report results of an experiment and computational models designed to assess the effects of light exposure and wavelengths on the structure of the dust microbiome. Specifically, we placed household dust in replicate model "rooms" with windows that transmitted visible, ultraviolet, or no light and measured taxonomic compositions, absolute abundances, and viabilities of the resulting bacterial communities. RESULTS: Light exposure per se led to lower abundances of viable bacteria and communities that were compositionally distinct from dark rooms, suggesting preferential inactivation of some microbes over others under daylighting conditions. Differences between communities experiencing visible and ultraviolet light wavelengths were relatively minor, manifesting primarily in abundances of dead human-derived taxa. Daylighting was associated with the loss of a few numerically dominant groups of related microorganisms and apparent increases in the abundances of some rare groups, suggesting that a small number of microorganisms may have exhibited modest population growth under lighting conditions. Although biological processes like population growth on dust could have generated these patterns, we also present an alternate statistical explanation using sampling models from ecology; simulations indicate that artefactual, apparent increases in the abundances of very rare taxa may be a null expectation following the selective inactivation of dominant microorganisms in a community. CONCLUSIONS: Our experimental and simulation-based results indicate that dust contains living bacterial taxa that can be inactivated following changes in local abiotic conditions and suggest that the bactericidal potential of ordinary window-filtered sunlight may be similar to ultraviolet wavelengths across dosages that are relevant to real buildings.

Molecular Evidence for Metabolically Active Bacteria in the Atmosphere.

Bacterial metabolisms are responsible for critical chemical transformations in nearly all environments, including oceans, freshwater, and soil. Despite the ubiquity of bacteria in the atmosphere, little is known about the metabolic functioning of atmospheric bacterial communities. To gain a better understanding of the metabolism of bacterial communities in the atmosphere, we used a combined empirical and model-based approach to investigate the structure and composition of potentially active bacterial communities in air sampled at a high elevation research station. We found that the composition of the putatively active bacterial community (assayed via rRNA) differed significantly from the total bacterial community (assayed via rDNA). Rare taxa in the total (rDNA) community were disproportionately active relative to abundant taxa, and members of the order Rhodospirillales had the highest potential for activity. We developed theory to explore the effects of random sampling from the rRNA and rDNA communities on observed differences between the communities. We found that random sampling, particularly in cases where active taxa are rare in the rDNA community, will give rise to observed differences in community composition including the occurrence of "phantom taxa", taxa which are detected in the rRNA community but not the rDNA community. We show that the use of comparative rRNA/rDNA techniques can reveal the structure and composition of the metabolically active portion of bacterial communities. Our observations suggest that metabolically active bacteria exist in the atmosphere and that these communities may be involved in the cycling of organic compounds in the atmosphere.

Modification of the sinus tarsi approach for open reduction and plate fixation of intra-articular calcaneus fractures: the limits of proximal extension based upon the vascular anatomy of the lateral calcaneal artery.

The treatment of displaced calcaneal fractures remains controversial. Early surgical management to restore articular congruence and the structural function of the calcaneus is widely accepted as the best way to avoid the negative consequences of malunion. Concerns remain however regarding the best approach for reducing and maintaining reduction of these complex fractures, while minimizing the risk of surgical complications. The potential for serious wound complications is a major concern, particularly breakdown of the lateral calcaneal skin flap with the extensile lateral approach. Various approaches have been developed to try and balance the need for direct reduction of the articular surface while minimizing the potential for wound complications. Palmer originally described a laterally based approach through the sinus tarsi for direct visualization of the articular surface for reduction. He and others have found this approach to be useful and reasonably safe. At times, however, it may be necessary to extend the limits of a small incision over the sinus tarsi to treat adjacent fractures or to aid reduction in more complex fractures. In addition, a limited sinus tarsi incision without elevation of the lateral calcaneal skin flap does not allow for plate fixation, a notable advantage of the extensile lateral approach, particularly in gaining reduction of the body of the calcaneus. The authors have used an extended sinus tarsi approach to include placement of plate percutaneously beneath the lateral calcaneal skin flap through a sinus tarsi approach, and to treat adjacent fractures and soft tissue injuries. A clinical series of 13 patients (including 7 chronic smokers and 1 with diabetes and vascular disease) with closed displaced intra-articular calcaneal fractures (Sanders types II and III) were treated by open reduction and internal fixation via this approach. Adjacent fractures were treated through the same incision. Two patients developed wound complications. No wound complications occurred in smokers. The vascular anatomy of the lateral calcaneal artery related to this approach was also studied with 16 cadaver legs. The lateral calcaneal artery (LCA) passed within 2 mm of the superior border of floor of the Superior Peroneal Retinaculum (SPR) at the midline of the peroneal sheath. By avoiding dissection through the deep portion of the SPR, the lateral calcaneal artery can be protected, thus preserving the blood supply to the lateral calcaneal skin flap.

Comparative charge analysis of one- and two-level lumbar total disc arthroplasty versus circumferential lumbar fusion.

STUDY DESIGN: This is a retrospective, independent study comparing 2 groups of patients treated surgically for discogenic low back pain associated with degenerative disc disease (DDD) in the lumbosacral spine. OBJECTIVE: To compare the surgical and hospitalization charges associated with 1- and 2-level lumbar total disc replacement and circumferential lumbar fusion. SUMMARY OF BACKGROUND DATA: Reported series of lumbar total disc replacement have been favorable. However, economic aspects of lumbar total disc replacement (TDR) have not been published or studied. This information is important considering the recent widespread utilization of new technologies. Recent studies have demonstrated comparable short-term clinical results between TDR and lumbar fusion recipients. Relative charges may be another important indicator of the most appropriate procedure. We report a hospital charge-analysis comparing ProDisc lumbar disc replacement with circumferential fusion for discogenic low back pain. METHODS: In a cohort of 53 prospectively selected patients with severe, disabling back pain and lumbar disc degeneration, 36 received Synthes ProDisc TDR and 17 underwent circumferential fusion for 1- and 2-level degenerative disc disease between L3 and S1. Randomization was performed using a 2-to-1 ratio of ProDisc recipients to control spinal fusion recipients. Charge comparisons, including operating room charges, inpatient hospital charges, and implant charges, were made from hospital records using inflation-corrected 2006 U.S. dollars. Operating room times, estimated blood loss, and length of stay were obtained from hospital records as well. Surgeon and anesthesiologist fees were, for the purposes of comparison, based on Medicare reimbursement rates. Statistical analysis was performed using a 2-tailed Student t test. RESULTS: For patients with 1-level disease, significant differences were noted between the TDR and fusion control group. The mean total charge for the TDR group was $35,592 versus $46,280 for the fusion group (P = 0.0018). Operating room charges were $12,000 and $18,950, respectively, for the TDR and fusion groups (P < 0.05). Implant charges averaged $13,990 for the fusion group, which is slightly higher than the $13,800 for the ProDisc (P = 0.9). Estimated blood loss averaged 794 mL in the fusion group versus 412 mL in the TDR group (P = 0.0058). Mean OR minutes averaged 344 minutes for the fusion group and 185 minutes for the TDR (P < 0.05) Mean length of stay was 4.78 days for fusion versus 4.32 days for TDR (P = 0.394). For patients with 2-level disease, charges were similar between the TDR and fusion groups. The mean total charge for the 2-level TDR group was $55,524 versus $56,823 for the fusion group (P = 0.55). Operating room charges were $15,340 and $20,560, respectively, for the TDR and fusion groups (P = 0.0003). Surgeon fees and anesthesiologist charges based on Medicare reimbursement rates were $5857 and $525 for the fusion group, respectively, versus $2826 and $331 for the TDR group (P < 0.05 for each). Implant charges were significantly lower for the fusion group (mean, $18,460) than those for 2-level Synthes ProDisc ($27,600) (P < 0.05). Operative time averaged 387 minutes for fusion versus 242 minutes for TDR (P < 0.0001). EBL and length of stay were similar. CONCLUSION: Patients undergoing 1- and 2-level ProDisc total disc replacement spent significantly less time in the OR and had less EBL than controls. Charges were significantly lower for TDR compared with circumferential fusions in the 1-level patient group, while charges were similar in the 2-level group.

Aneurysmal bone cyst of the second cervical vertebrae causing multilevel upper cervical instability.

OBJECTIVE: Aneurysmal bone cyst (ABC) is a rare expansile osteolytic lesion of bone comprising proliferating vascular tissue lining blood-filled cystic cavities. ABCs occur most frequently in patients under age 20 and are uncommon after 30 years of age. Three to 20% of cases occur in the spine, and upper cervical involvement is rare. Lesions may grow rapidly and attain considerable size. When involving the spine, ABCs may result in instability and neurologic compromise, making prompt diagnosis and treatment imperative. We present a report of a 6-year-old child with an ABC of the second cervical vertebrae causing atlantoaxial and C2-C3 instability, treated successfully with curettage, decompression, and anterior and posterior arthrodesis with posterior instrumentation. METHODS: The patient underwent a staged procedure consisting of posterior instrumentation from occiput to C4 and curettage of the lesion followed by anterior cervical discectomy and fusion of C2-C4. The diagnosis, surgical treatment, and outcome of the case are described and relevant literature reviewed. RESULTS: The patient sustained no lasting neurologic deficits and was disease-free at 3 years of follow-up. CONCLUSIONS: ABC is a rare but potentially devastating cause of upper cervical spine instability. Prompt detection and treatment with curettage, decompression, and fusion can produce a satisfactory result and prevent spinal cord injury.