Management of newborns and healthcare workers exposed to isoniazid-resistant congenital tuberculosis in the neonatal intensive care unit

BACKGROUND

Management of newborns and healthcare workers (HCWs) exposed to congenital tuberculosis (TB) in the neonatal intensive care unit (NICU) has been reported rarely.

AIM

To outline a contact investigation process for individuals exposed to congenital TB in the NICU and investigate nosocomial transmission. Additionally, to assess the efficacy and safety of window prophylaxis in exposed newborns.

METHODS

A baby, born at a gestational age of 28 + 1 weeks, was diagnosed with isoniazid-resistant congenital TB on the 39th day of admission to the level IV NICU. Newborns and HCWs exposed cumulatively for ≥8 h underwent contact investigation and follow-up for a year.

FINDINGS

Eighty-two newborns underwent contact investigation. All newborns displayed normal chest X-rays, and 42 hospitalized newborns tested negative for acid-fast bacilli stain and Xpert® MTB/RIF assay in their endotracheal sputum or gastric juices. Eighty received window prophylaxis: six of 75 on rifampin experienced mild adverse events, and none of the five on levofloxacin. After 12 weeks, five (6.1%) had a positive tuberculin skin test, all of whom had already received the Bacillus Calmette-Guérin vaccine and tested negative on TB interferon-gamma releasing assay. Of 119 exposed HCWs, three (2.5%) were diagnosed with latent TB infection and completed a four-month rifampin therapy. There was no active TB disease among exposed newborns and HCWs during a one-year follow-up.

CONCLUSION

Timely diagnosis of congenital TB is crucial for minimizing transmission among exposed neonates and HCWs in the NICU setting. In cases of isoniazid-resistant index patients, even premature newborns may consider the use of rifampin or levofloxacin for window prophylaxis.

Association between body mass index, bone bending strength, and BMD in young sedentary women

The rationale was to determine whether body mass index (BMI) is a predictor of bone bending strength and bone mineral density (BMD) in young sedentary women. Results show that BMI is not a predictor of bone bending strength and that young women with low BMI also have low BMD.

INTRODUCTION

The purpose of this study was to determine whether body mass index (BMI) is a predictor of tibial or ulnar bending strength and bone mineral density (BMD) in sedentary women.

METHODS

Sedentary women (n = 34), age 19-27 years, with low BMI (LBMI < 18.5 kg/m², n = 16), and normal or high BMI (NHBMI between 18.5 and 29.9 kg/m², n = 18) participated as study subjects. Study outcomes included tibial and ulnar bending strength (EI in Nm²) using a non-invasive mechanical response tissue analyzer (MRTA); BMD and bone mineral content (BMC) of the whole body (WB), femoral neck (FN), total hip (TH), lumbar spine 1-4 (LS1-4), and ulna; and bone turnover biomarkers.

RESULTS

The LBMI group have lower (p < 0.01) body weight [group difference (Δ) = 32.0%], lean mass (LM) (Δ = 23.1%), fat mass (FM) (Δ = 77.2%), and tibial bending strength (Δ = 22.0%), compared to the NHBMI. The LBMI group also have lower (all p < 0.025) BMC in WB (Δ = 19.9%), FN (Δ = 20.1%) and TH (Δ = 19.0%), compared to the NHMBI, not in BMD results. Multivariate regression analysis shows that significant predictors of tibial bending strength are tibia length (adjusted R² = .341), age (adjusted R² = .489), ulna BMD (adjusted R² = .536), and LM (adjusted R² = .580). BMI was positively correlated with tibial EI (p < 0.05), height, weight, FM, LM, body fat% (all p < 0.01), and BMD of WB, FN, TH, and LS 1-4 (p < 0.05 or < 0.01).

CONCLUSIONS

Our results show that BMI is not a significant predictor of tibial or ulnar bending strength in young sedentary women.

The Early Prediction of Response to Neoadjuvant Chemotherapy Using MRI

Purpose: Neoadjuvant chemotherapy is an effective method for down-staging the primary tumor before surgery. However, some of patients do not respond. In these patients, neoadjuvant chemotherapy is just an ineffective, toxic and expensive procedure. Therefore, it is very important to find the reliable method to differentiate the responder from non-responder as early as possible. In order to evaluate the role of magnetic resonance imaging (MRI) for the assessment of tumor response, we examined the correlation between the early MRI changes after the 1st cycle of neoadjuvant chemotherapy and later pathologic response after the 3rd cycle of neoadjuvant chemotherapy.Patients and method: 31 breast cancer patients who underwent neoadjuvant chemotherapy prior to surgery were analyzed. The baseline MRI was taken before neoadjuvant chemotherapy. Anthracycline plus taxane were administered to all patients. Post-chemotherapy MRI assessment was done just before the 2nd cycle of neoadjuvant chemotherapy. If the primary tumor was reduced more than 20% in the product of the longest and perpendicular diameter, those cases were classified as responders. Surgery was performed after the 3rd cycle of neoadjuvant chemotherapy. The pathologic response was assessed by measuring pathologic tumor size of viable tumor cells. Sensitivity, specificity, positive predictive value, and negative predictive value of MRI findings were calculated on the basis of histopathological examination.Results: Total 31 patients were examined. Of these patients, 2 patients had bilateral breast cancer. Therefore, a total of 33 lesions were evaluated. The median tumor size on baseline MRI was 4.5cm (range:2.1-10.0cm). 27 cases were classified as responders on early MRI findings. Of these cases, pathologic response was confirmed in 26 cases after surgery. Six cases were classified as non-responder on MRI. In this group, 3 cases showed pathologic response and 3 cases did not. Sensitivity, specificity, positive predictive value and negative predictive value of early MRI findings for the prediction of pathologic response were 89.7%, 75.0%, 96.3% and 50.0%, respectively.Conclusion: Post-chemotherapy MRI after the 1st cycle of neoadjuvant chemotherapy could differentiate responders from non-responders with high accuracy. It would be helpful to determine whether the chemotherapy regimen should be continued or not in the early phase of neoadjuvant therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6057.

Effect of magainin, class L, and class A amphipathic peptides on fatty acid spin labels in lipid bilayers

Magainins and other antimicrobial peptides increase ion flux across the membrane. They may do this by forming some type of pore or by perturbing lipid organization due to peptide lying on the bilayer surface. In order to determine if magainins perturb the lipid sufficiently to permeabilize the bilayer, their effect on the motion of fatty acid and lipid spin labels in phosphatidylcholine/phosphatidylglycerol (PC/PG) lipid vesicles was determined. Their effect was compared to two synthetic peptides, 18L and Ac-18A-NH(2), designed to mimic the naturally occurring classes of lytic (class L) and apolipoprotein (class A) amphipathic helices, respectively. We show that although magainins and 18L both had significant effects on lipid chain order, much greater than Ac-18A-NH(2), there was no correlation between these effects and the relative ability of these three peptide classes to permeabilize PC/PG vesicles in the order magainins=Ac-18A-NH(2) >> 18L. This suggests that the perturbing effects of magainins on lipid chain order at permeabilizing concentrations are not directly responsible for the increased leakage of vesicle contents. The greater ability of the magainins to permeabilize PC/PG vesicles relative to 18L is thus more likely due to formation of some type of pore by magainins. The greater ability of Ac-18A-NH(2) relative to 18L to permeabilize PC/PG vesicles despite its lack of disordering effect must be due to its ability to cause membrane fragmentation. Effects of these peptides on other lipids indicated that the mechanism by which they permeabilize lipid bilayers depends both on the peptide and on the lipid composition of the vesicles.

alpha-Synuclein membrane interactions and lipid specificity

With the discovery of missense mutations (A53T and A30P) in alpha-synuclein (alpha-Syn) in several families with early onset familial Parkinson's disease, alpha-Syn aggregation and fibril formation have been thought to play a role in the pathogenesis of alpha-synucleinopathies, such as Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. As previous reports have suggested that alpha-Syn plays a role in lipid transport and synaptic membrane biogenesis, we investigated whether alpha-Syn binds to a specific lipid ligand using thin layer chromatography overlay and examined the changes in its secondary structure using circular dichroism spectroscopy. alpha-Syn was found to bind to acidic phospholipid vesicles and this binding was significantly augmented by the presence of phosphatidylethanolamine, a neutral phospholipid. We further examined the interaction of alpha-Syn with lipids by in situ atomic force microscopy. The association of soluble wild-type alpha-Syn with planar lipid bilayers resulted in extensive bilayer disruption and the formation of amorphous aggregates and small fibrils. The A53T mutant alpha-Syn disrupted the lipid bilayers in a similar fashion but at a slower rate. These results suggest that alpha-Syn membrane interactions are physiologically important and the lipid composition of the cellular membranes may affect these interactions in vivo.

Presenilin mutations associated with Alzheimer disease cause defective intracellular trafficking of beta-catenin, a component of the presenilin protein complex

The presenilin proteins are components of high-molecular-weight protein complexes in the endoplasmic reticulum and Golgi apparatus that also contain beta-catenin. We report here that presenilin mutations associated with familial Alzheimer disease (but not the non-pathogenic Glu318Gly polymorphism) alter the intracellular trafficking of beta-catenin after activation of the Wnt/beta-catenin signal transduction pathway. As with their effect on betaAPP processing, the effect of PS1 mutations on trafficking of beta-catenin arises from a dominant 'gain of aberrant function' activity. These results indicate that mistrafficking of selected presenilin ligands is a candidate mechanism for the genesis of Alzheimer disease associated with presenilin mutations, and that dysfunction in the presenilin-beta-catenin protein complexes is central to this process.

Insertion of magainin into the lipid bilayer detected using lipid photolabels

We investigated the interaction of the antimicrobial peptides Ala19-magainin 2 amide and magainin 2 amide with lipid using two lipid photolabels, azidobenzoyl galactosylceramide (GalCer-PL) and azidobenzoylamido capryloyl galactosylceramide (GalCer-C8-PL), which position their photosensitive groups near the apolar-polar interface and near the center of the bilayer, respectively. Magainins have been postulated to permeabilize membranes either by inserting in a transmembrane fashion into the bilayer and forming a channel or by binding to the surface of the bilayer and disturbing lipid packing. Evidence for channel formation has been difficult to obtain, possibly because only a fraction of the peptide may form a channel at any one time and because the channels may have a short lifetime. Both photolabels significantly labeled the peptides when bound to acidic phospholipid vesicles. The extent of labeling by GalCer-C8-PL was at least 70% of that by GalCer-PL, indicating that some of the peptide was inserted deeply into the bilayer at least transiently. The extent of labeling of Ala19-magainin 2 amide increased significantly with an increase in the peptide to lipid mole ratio, indicating cooperativity and supporting the channel model. The extent of labeling of this peptide was maximal by 30 s and did not change over 30 min, indicating that peptide insertion is rapid and either that the peptide remains inserted for at least 30 min or that equilibrium between inserted and noninserted peptide is achieved by 30 s. The latter is supported by other studies in the literature. Use of this hydrophobic photolabeling technique has permitted detection of peptide monomers which inserted into the bilayer and/or formed a channel at some time during the labeling procedure.

Effect of posttranslational modifications to myelin basic protein on its ability to aggregate acidic lipid vesicles

When isolated from central nervous system myelin, myelin basic protein (MBP) exhibits charge microheterogeneity due to posttranslational deamidation, phosphorylation, and deimination of arginine to citrulline. These modifications are known to decrease the ability of MBP to aggregate acidic lipid vesicles and thus could regulate the ability of MBP to mediate adhesion between the intracellular surfaces of myelin. The effects of salt (KCl) concentration and the protein to lipid ratio on the ability of charge isomers of MBP to aggregate large unilamellar vesicles (LUVs) were investigated. Increased salt concentration from 10 to 100 mM caused increasing aggregation of LUVs by low concentrations of all charge isomers but did not eliminate the differences in their abilities to aggregate. All isomers were bound equally up to about 100 mM K+ but were dissociated at higher K+ concentrations. The degree of dissociation increased with increasing net negative charge of the isomer. At high concentrations all charge isomers except the form in which six arginine residues are converted to citrulline (C8) aggregated LUVs of phosphatidylcholine/phosphatidylserine (PC/PS) 8:2 (mol/mol) similarly and salt increased the aggregation to the same degree for all. There was less difference in the ability of the charge isomers, including C8, to aggregate LUVs with a lipid composition resembling that of the cytoplasmic leaflet of myelin (Cyt-LUVs) than for PC/PS LUVs. Furthermore, high salt concentrations (400 mM) did not dissociate any of the charge isomers from the Cyt-LUVs. These results suggest that the reason for inhibition of aggregating ability by charge modification is not increased charge repulsion of the protein but rather its reduced multivalency of net positive charge. They indicate further that the lipid composition of the cytoplasmic leaflet is ideally suited to permit MBP-mediated adhesion and that charge modifications of MBP would probably not affect adhesion of the intracellular surfaces of compact myelin where MBP concentration is high. However, charge modifications might affect adhesion in cytoplasm-containing regions of myelin such as the paranodal loops, where MBP concentration is low and where K+ concentration may vary in the range of 60-75 mM.

Aggregation of acidic lipid vesicles by myelin basic protein: dependence on potassium concentration

In the compacted multilayered myelin sheath of the central nervous system, myelin basic protein (MBP) is thought to be responsible for adhesion of the intracellular surfaces by electrostatic interactions with acidic lipids. Noncompacted regions of myelin containing cytosol exist and can take up potassium released into the extracellular fluid after the axonal action potential. Therefore, the effect of K+ concentration on the ability of MBP to aggregate large unilamellar vesicles (LUVs) containing phosphatidylcholine (PC) and 10-20% acidic lipid was investigated. At MBP to lipid ratios where there was an excess of acidic lipid, physiological increases in K+ concentration up to about 100 mM greatly increased MBP-mediated aggregation of the LUVs by shielding the negative charge on the vesicle surface. Thus, changes in K+ concentration during the axonal action potential could regulate MBP-mediated adhesion of the intracellular myelin surfaces of noncompacted regions of myelin such as the paranodal loops. It could thus regulate the volume of these cytosolic regions, allowing MBP to have a dynamic function in myelin. Concentrations of K+ above 150 mM caused dissociation of MBP from LUVs containing PC and a single acidic lipid. LUVs containing the lipid composition estimated to be characteristic of the cytoplasmic leaflet of myelin (Cyt.-LUVs) were found to interact uniquely with MBP, resulting in greater aggregation, greater sensitivity to K+ concentration, and resistance to dissociation at high K+ concentrations. The latter suggested that electrostatic interactions were not the only force involved in binding of MBP to the Cyt.-LUVs. Hydrogen bonding of the protein to the lipid head groups and hydrophobic interactions due to penetration of hydrophobic amino acid side chains into the bilayer could also occur. The greater involvement of hydrophobic interactions of MBP with Cyt.-LUVs compared to PC/acidic lipid LUVs was confirmed from greater labeling of MBP bound to Cyt.-LUVs by the hydrophobic photolabeled TID. Cholesterol and phosphatidylethanolamine together were found to be responsible for the greater MBP-mediated aggregation of Cyt.-LUVs and the greater TID labeling of MBP bound to Cyt.-LUVs compared to PC/acidic lipid LUVs. Thus, the lipid composition of the intracellular surface of myelin is well suited to allow MBP to mediate adhesion of apposing intracellular membranes and to respond in a dynamic way in some regions of myelin, such as the paranodal loops, to changes in K+ concentration resulting from nerve conduction.

A transmembrane potential does not affect the vertical location of charged lipid spin labels with respect to the surface of a phosphatidylcholine bilayer

The effect of a transmembrane potential on the vertical location of a charged lipid in a neutral phosphatidylcholine (PC) lipid bilayer has been investigated using negatively and positively charged spin-labeled lipids. A transmembrane potential was generated across extruded large unilamellar vesicles either by using a K+/Na+ ion gradient and a K+ ionophore or by using a pH gradient. Since a transmembrane potential could have opposing effects on lipids in the inner and outer monolayer, some of the acidic spin labels were asymmetrically located in the inner monolayer as a result of a pH gradient. No significant effect on their order parameters was observed upon applying a transmembrane potential. The internal dipole potential of the bilayer was modified by using dialkyl-PC or by incorporating 10 mol% phloretin, or 6-ketocholestanol in the PC, but a transmembrane potential still had no detectable effect on the spin labeled lipids. Therefore, it is concluded that the electrochemical potential across membranes probably does not cause a significant change in the vertical location of charged lipids with respect to the surface of a PC bilayer. This suggests that polar interactions and/or van der Waals interactions between the spin probe and the surrounding lipids stabilize the overall structure of the membranes and these interactions are not disrupted by a selective effect of the transmembrane potential on the charged lipids.