The initial soil microbiota impacts the potential for lignocellulose degradation during soil solarization

AIMS

Soil biosolarization (SBS) is a pest control technology that includes the incorporation of organic matter into soil prior to solarization. The objective of this study was to measure the impact of the initial soil microbiome on the temporal evolution of genes encoding lignocellulose-degrading enzymes during SBS.

METHODS AND RESULTS

Soil biosolarization field experiments were completed using green waste (GW) as a soil amendment and in the presence and absence of compost activating inoculum. Samples were collected over time and at two different soil depths for measurement of the microbial community and the predicted lignocellulosic-degrading microbiome. Compost inoculum had a significant positive effect on several predicted genes encoding enzymes involved in cellulose, hemicellulose and lignin degradation. These included beta-glucosidase, endo-1,3(4)-beta-glucanase, alpha-galactosidase and laccase.

CONCLUSION

Amendment of micro-organisms found in compost to soil prior to SBS enhanced the degradation potential of cellulose, hemicellulose and lignin found in GW.

SIGNIFICANCE AND IMPACT OF THE STUDY

The type of organic matter amended and its biotransformation by soil micro-organisms impact the efficacy of SBS. The results suggest that co-amending highly recalcitrant biomass with micro-organisms found in compost improves biomass conversion during SBS.

Effect of inoculum source on the enrichment of microbial communities on two lignocellulosic bioenergy crops under thermophilic and high-solids conditions

AIMS

Culturing compost-derived microbial communities on biofuel feedstocks under industrial conditions is a technique to enrich for organisms and lignocellulolytic enzymes for bioenergy feedstock deconstruction. In this study, microbial communities from green waste compost (GWC) and grape pomace compost (GPC) were cultured on switchgrass and eucalyptus to observe the impact of inoculation on feedstock decomposition and microbial community structure.

METHODS AND RESULTS

Respiration was monitored as a measure of microbial activity, and 16S ribosomal RNA gene sequencing was used to characterize microbial community structure. The enriched community structure and respiration were influenced by the choice of feedstock, compost type, and application of thermophilic, high-solids conditions. However, the effect of compost source was significantly less than the effects of the other culture variables.

CONCLUSIONS

Although there are subtle differences in potentially lignocellulolytic taxa between GPC- and GWC-derived communities, these differences do not affect the decomposition rates for these communities on switchgrass or eucalyptus.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results are useful for designing future experiments to discover lignocellulolytic micro-organisms from compost. They suggest that such work may be better served by deemphasizing screening of compost sources and instead focusing on how compost-derived communities adapt to the feedstocks and process conditions relevant to biofuel production.

Desensitization in patients with beta-lactam drug allergy

BACKGROUND

Patients with a history of beta-lactam antibiotic allergy are often admitted to the hospital with severe or life-threatening infections requiring beta-lactam antibiotics. Strict avoidance of beta lactams to such patients may prevent them from getting adequate coverage and can lead to an increase in the use of alternative antibiotics, which can predispose to antibiotic resistance. Past studies revealed a lower incidence of pen allergy then patients' histories suggest. Fortunately today, there are three options for patients presenting with a history of beta-lactam allergy. Penicillin skin testing, beta-lactam challenge or beta-lactam desensitization. Recently Pre Pen has been FDA re-approved and when combined with Pen G is a valid way to determine if patients are able to tolerate beta-lactam antibiotic. When these agents are not available one must decide about desensitization or challenge. When a patient has a positive penicillin skin test, desensitization or beta-lactam avoidance are the only options. This paper reviews the safety of beta-lactam desensitization.

OBJECTIVE

To perform a chart review on patients desensitised with beta lactam to determine if desensitizations can be performed safely without minimal complications.

METHODS

A retrospective chart review was performed on allergy and immunology inpatient consultations for beta-lactam desensitization between September 2003 and August 2006 at the Cedars-Sinai Medical Centre in Los Angeles. Patient data and outcomes of desensitization were analysed.

RESULTS

A total of 13 intravenous desensitizations were performed on 12 patients. The patients consisted of eight females and four males with an average age of 65 years. Age range was 36-92 years old. All 13 intravenous desensitizations were completed without complications. No patient required a slower rate of desensitization or discontinuance of the desensitization. Patients were able to tolerate the initial therapeutic dose of their beta-lactam antibiotic and were then able to complete full therapeutic courses of their antibiotic.

CONCLUSION

Beta-lactam antibiotic sensitivity continues to present a challenging problem for physicians. Patients with drug resistant infections who are unable to obtain skin testing or who test positive to skin tests may need either a challenge or desensitization. Desensitization, saved for those with a convincing beta-lactam hypersensitivity history is often the choice of last resort given the associated cost and risk of anaphylaxis. However, once desensitization is complete, patients are usually able to tolerate full doses of antibiotics for full treatment length with minimal side effects.

The effects of limb elevation and dependency on local arteriovenous gradients in normal human limbs with particular reference to limbs with increased tissue pressure

Although clinically useful for the control of extremity swelling, the combination of compression and elevation may significantly reduce the local arteriovenous gradient.

Association of dialyzer reuse and hospitalization rates among hemodialysis patients in the US

OBJECTIVES

To determine if reuse of hemodialyzers is associated with higher rates of hospitalization and their resulting costs among end-stage renal disease (ESRD) patients.

METHODS

Noncurrent cohort study of hospitalization rates among 27,264 ESRD patients beginning hemodialysis in the United States in 1986 and 1987.

RESULTS

Dialysis in free-standing facilities reprocessing dialyzers was associated with a greater rate of hospitalization than in facilities not reprocessing (relative rate (RR) = 1.08, 95% confidence interval (CI), 1.02-1.14). This higher rate of hospitalization was observed with dialyzer reuse using peracetic/acetic acids (RR = 1.11, CI 1. 04-1.18) and formaldehyde (RR = 1.07, CI 1.00-1.14), but not glutaraldehyde (p = 0.97). There was no difference among hospitalization rates in hospital-based facilities reprocessing dialyzers with any sterilant and those not reprocessing. Hospitalization for causes other than vascular access morbidity in free-standing facilities reusing dialyzers with formaldehyde was not different from hospitalization in facilities not reusing. However, reuse with peracetic/acetic acids was associated with higher rates of hospitalization than formaldehyde (RR = 1.08, CI 1.03-1.15).

CONCLUSIONS

Dialysis in free-standing facilities reprocessing dialyzers with peracetic/acetic acids or formaldehyde was associated with greater hospitalization than dialysis without dialyzer reprocessing. This greater hospitalization accounts for a large increment in inpatient stays in the USA. These findings raise important concerns about potentially avoidable morbidity among hemodialysis patients.

Association of dialyzer reuse with hospitalization and survival rates among U.S. hemodialysis patients: do comorbidities matter?

The objective of this study was to determine whether the associations between reuse of hemodialyzers and higher rates of death and hospitalization persist after adjustment for comorbidity. This was a nonconcurrent cohort study of survival and hospitalization rates among 1491 U.S. chronic hemodialysis patients beginning treatment in 1986 and 1987. The impact of dialyzer reuse was compared across three survival models: an unadjusted model, a "base" model adjusted only for demographics and renal diagnosis, and an "augmented" model additionally adjusted for comorbidities. We found that reuse of dialyzers was associated with a similarly higher rate of death in analyses unadjusted for confounders (relative risk [RR] 1.25, 95% confidence interval [CI] 0.97-1.61), adjusted for demographics and renal diagnosis (RR 1.16, 95% CI 0.96-1.41), and analyses additionally adjusted for comorbidities (RR = 1.25, CI, 1.03, 1.52). Reusing dialyzers was also associated with a greater rate of hospitalization that was stable regardless of adjustment procedures. We conclude that higher rates of death and hospitalization associated with dialyzer reuse persist regardless of adjustment for demographic characteristics or baseline comorbidities. These findings amplify concerns that there exists elevated morbidity among hemodialysis patients treated in facilities that reuse hemodialyzers. Although the association we observed was not confounded by comorbidity, a cause-and-effect relationship between dialyzer reuse and morbidity could not be proved because of the inability to control for aspects of care other than dialyzer reuse.

The effect of exercise upon cutaneous oxygen delivery in the extremities of patients with claudication and in a human laboratory model of claudication

Transcutaneous PO2 measurements have been shown previously to reflect local cutaneous oxygen delivery in patients with severe peripheral arterial insufficiency. In the present studies, transcutaneous PO2 measurements indicated that exercise of the involved extremity lowered cutaneous oxygen delivery in patients with moderate peripheral arterial insufficiency (claudication). These exercise-related changes in transcutaneous PO2 were reproduced in a human laboratory model of claudication. The pattern of change in transcutaneous PO2 observed in this model during and after exercise correlated closely with the pattern of change in mean systemic blood pressure during the same time period.

Transcutaneous oxygen tension measurements on limbs of diabetic and nondiabetic patients with peripheral vascular disease

We measured transcutaneous oxygen tension (TcPo2) at a skin temperature of 44 degrees C on 319 limbs in an approximately equal number of nondiabetic and diabetic patients with peripheral vascular disease. Measurements were made above the knee, below the knee (BK), and on the dorsum of the foot. Nondiabetic limbs with leg/foot (the lesser of BK or foot) TcPo2 values below 20 mm Hg were significantly more likely to have ulcers, to have rest pain, or to require an amputation on the limb as compared with limbs with leg/foot TcPo2 values above 20 mm Hg. Patients with more severe symptoms had significantly reduced limb TcPo2 values, and these values were lower at more distal measurement sites. Generally, these results were similar in diabetic and nondiabetic patients without limb ulceration; however, the diabetic patients were more likely to have ulcers in the presence of high limb TcPo2. This observation suggests that ulceration in a substantial proportion of the diabetic patients may have resulted from factors other than insufficient cutaneous tissue oxygen delivery.

Segmental transcutaneous measurements of PO2 in patients requiring below-the-knee amputation for peripheral vascular insufficiency

An accurate method is needed to quantitate the healing potentials of the possible sites of amputation in dysvascular limbs. We evaluated the segmental transcutaneous measurements of PO2 in thirty-seven patients who required below-the-knee amputation because of peripheral vascular insufficiency. The fifteen patients with below-the-knee transcutaneous PO2 values of forty millimeters of mercury or more had no delay in healing of the below-the-knee amputation. Seventeen of nineteen patients with values of more than zero but less than forty millimeters of mercury had healing at the below-the-knee level, in two after local revision. The three patients who had below-the-knee values of zero required re-amputation above the knee.

The effects of compression and elevation on the circulation to the skin of the hand as reflected by transcutaneous PO2

Transcutaneous PO2 has been used in a group of four normal subjects to noninvasively indicate the effects of compression and limb elevation on the circulation to the skin of the hand. Both compression and elevation of the hand reduced the local transcutaneous PO2. A combination of compression and elevation had a significantly greater effect than either of these modalities applied singly. The observations in this study suggest that the effect of hand elevation compression are mediated through a reduction in the local arteriovenous gradient. Although hand elevation and compression are clinically useful in the control of hand swelling, the hand surgeon should be aware of their potential deleterious effects on local circulation, particularly when they are used in combination.

Dependence of transcutaneous oxygen tension on local arteriovenous pressure gradient in normal subjects

1. We studied the relationship between transcutaneous oxygen tension at the foot and local arteriovenous pressure difference in 15 normal men and women; arteriovenous pressure difference was varied by changing the height of the foot with respect to the heart and by applying external pressure to the foot. 2. Control transcutaneous oxygen tension was 67 +/- 9 SD mmHg (8.9 +/- 1.2 kPa) at a control arteriovenous pressure difference of 80 +/- 6 SD mmHg (10.6 +/- 0.8 kPa). 3. In every subject transcutaneous oxygen tension fell non-linearly with a decrease in arteriovenous pressure difference; transcutaneous oxygen tension was relatively insensitive to changes in arteriovenous pressure difference when arteriovenous pressure difference was high, but always fell sharply to zero at some positive arteriovenous pressure difference [range 13-34 mmHg (1.7-4.5 kPa)]. 4. An analysis of the data indicated that transcutaneous oxygen tension varied with arteriovenous pressure difference approximately as the oxygen tension of cutaneous venous blood under the sensor varied (in the absence of changes in cutaneous vascular resistance and oxygen consumption). 5. This analysis was supported by studies in three subjects in whom the oxygen tension of superficial venous drainage from a warmed hand or foot was measured along with transcutaneous oxygen tension while arteriovenous pressure difference was varied.

Factors affecting the tolerance of muscle circulation and function for increased tissue pressure

The tolerance of neuromuscular tissue for increased tissue pressure has been observed clinically to vary among individuals. In experimental operations on rabbits, various factors may affect tissue pressure tolerance. Arterial hypoxia, halothane anesthesia, local arterial occlusion, and acute hemorrhage each reduced the amount of pressure necessary to produce circulatory and functional deficits. Extrapolation of these observations suggest that patients with hemorrhage, arterial hypoxia, and peripheral vascular disease may be at greater risk from a given tissue pressure than patients without these conditions.

Transcutaneous PO2: a potential monitor the status of replanted limb parts

In animal and human investigations, transcutaneous PO2 proved to be a sensitive and rapid indicator of the patency of the artery and veins supplying a limb part. Furthermore, transcutaneous PO2 indicated the presence or absence of collateral circulation. Commercially available transcutaneous PO2 probes were easily applied to human fingers and dramatically reflected the compromise of finger circulation by the inflation of a blood-pressure cuff around the arm. Probe temperatures from 42 to 44 degrees C appeared to provide satisfactory sensitivity and safety. On the basis of these studies, we conclude that transcutaneous PO2 monitoring holds sufficient potential for the evaluation of replanted limb parts to deserve a clinical trial.

Effect of acute hemorrhage on transcutaneous, subcutaneous, intramuscular, and arterial oxygen tensions

Although transcutaneous PO2 is a close approximation of arterial PO2 in most neonates, infants in shock often show lower transcutaneous than arterial PO2 values. For a better understanding of this discrepancy, we investigated the effect of acute hemorrhage on transcutaneous, tissue, and arterial PO2 in rabbits. With progressive hemorrhage, transcutaneous and tissue PO2 values declined steeply while arterial PO2 values did not. We speculate that the progressive decrement in transcutaneous and tissue PO2 value with hemorrhage is produced by diminished peripheral blood flow. Rather than representing a failure of the transcutaneous PO2 monitoring method, we speculate that transcutaneous hypoxia with shock may be a clinically valuable danger signal.

Transcutaneous oxygen tension measurement in peripheral vascular disease

To date, results of laboratory and clinical investigations suggest that transcutaneous pO2 measurements hold considerable promise as a technique for evaluating the adequacy of cutaneous circulation. The advantages of this technique are that it is simple to use, noninvasive and does not require the use of radioactive isotopes. Since the available data are, as yet, insufficient to confirm the reliability of this technique, a prospective study of segmental transcutaneous pO2 values in patients with peripheral vascular disease is being continued. These values are then being correlated with the subsequent clinical course.

Factitious (self-inflicted) skin wounds

We represent 4 of our recent cases of factitious skin wounds. The general aspects of these wounds--including etiology, diagnosis, detection, and treatment--are discussed.