Simulations of Proposed Mechanisms of FtsZ-Driven Cell Constriction.

To divide, bacteria must constrict their membranes against significant force from turgor pressure. A tubulin homolog, FtsZ, is thought to drive constriction, but how FtsZ filaments might generate constrictive force in the absence of motor proteins is not well understood. There are two predominant models in the field. In one, FtsZ filaments overlap to form complete rings around the circumference of the cell, and attractive forces cause filaments to slide past each other to maximize lateral contact. In the other, filaments exert force on the membrane by a GTP-hydrolysis-induced switch in conformation from straight to bent. Here, we developed software, ZCONSTRICT, for quantitative three-dimensional (3D) simulations of Gram-negative bacterial cell division to test these two models and identify critical conditions required for them to work. We find that the avidity of any kind of lateral interactions quickly halts the sliding of filaments, so a mechanism such as depolymerization or treadmilling is required to sustain constriction by filament sliding. For filament bending, we find that a mechanism such as the presence of a rigid linker is required to constrain bending to within the division plane and maintain the distance observed in vivo between the filaments and the membrane. Of these two models, only the filament bending model is consistent with our lab's recent observation of constriction associated with a single, short FtsZ filament.IMPORTANCE FtsZ is thought to generate constrictive force to divide the cell, possibly via one of two predominant models in the field. In one, FtsZ filaments overlap to form complete rings which constrict as filaments slide past each other to maximize lateral contact. In the other, filaments exert force on the membrane by switching conformation from straight to bent. Here, we developed software, ZCONSTRICT, for three-dimensional (3D) simulations to test these two models. We find that a mechanism such as depolymerization or treadmilling are required to sustain constriction by filament sliding. For filament bending, we find that a mechanism that constrains bending to within the division plane is required to maintain the distance observed in vivo between the filaments and the membrane.

Structure of the fission yeast actomyosin ring during constriction.

Cell division in many eukaryotes is driven by a ring containing actin and myosin. While much is known about the main proteins involved, the precise arrangement of actin filaments within the contractile machinery, and how force is transmitted to the membrane, remains unclear. Here we use cryosectioning and cryofocused ion beam milling to gain access to cryopreserved actomyosin rings in Schizosaccharomyces pombe for direct 3D imaging by electron cryotomography. Our results show that straight, overlapping actin filaments, running nearly parallel to each other and to the membrane, form a loose bundle of ∼150 nm in diameter that "saddles" the inward-bending membrane at the leading edge of the division septum. The filaments do not make direct contact with the membrane. Our analysis of the actin filaments reveals the variability in filament number, nearest-neighbor distances between filaments within the bundle, their distance from the membrane, and angular distribution with respect to the membrane.

Therapeutic Strategies to Reduce the Toxicity of Misfolded Protein Oligomers.

The aberrant aggregation of proteins is implicated in the onset and pathogenesis of a wide range of neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. Mounting evidence indicates that misfolded protein oligomers produced as intermediates in the aggregation process are potent neurotoxic agents in these diseases. Because of the transient and heterogeneous nature of these elusive aggregates, however, it has proven challenging to develop therapeutics that can effectively target them. Here, we review approaches aimed at reducing oligomer toxicity, including (1) modulating the oligomer populations (e.g., by altering the kinetics of aggregation by inhibiting, enhancing, or redirecting the process), (2) modulating the oligomer properties (e.g., through the size-hydrophobicity-toxicity relationship), (3) modulating the oligomer interactions (e.g., by protecting cell membranes by displacing oligomers), and (4) reducing oligomer toxicity by potentiating the protein homeostasis system. We analyze examples of these complementary approaches, which may lead to the development of compounds capable of preventing or treating neurodegenerative disorders associated with protein aggregation.

Coarse-grained simulations of bacterial cell wall growth reveal that local coordination alone can be sufficient to maintain rod shape.

Bacteria are surrounded by a peptidoglycan (PG) cell wall that must be remodeled to allow cell growth. While many structural details and properties of PG and the individual enzymes involved are known, how the process is coordinated to maintain cell integrity and rod shape is not understood. We have developed a coarse-grained method to simulate how individual transglycosylases, transpeptidases, and endopeptidases could introduce new material into an existing unilayer PG network. We find that a simple model with no enzyme coordination fails to maintain cell wall integrity and rod shape. We then iteratively analyze failure modes and explore different mechanistic hypotheses about how each problem might be overcome by the macromolecules involved. In contrast to a current theory, which posits that long MreB filaments are needed to coordinate PG insertion sites, we find that local coordination of enzyme activities in individual complexes can be sufficient to maintain cell integrity and rod shape. We also present possible molecular explanations for the existence of monofunctional transpeptidases and glycosidases (glycoside hydrolases), trimeric peptide crosslinks, cell twisting during growth, and synthesis of new strands in pairs.

The incidence of primary antibiotic resistance of Helicobacter pylori in Vietnam.

GOALS: To determine the susceptibility of Helicobacter pylori strains isolated from a Vietnamese population to 5 antibiotics. BACKGROUND: The incidence of antibiotic resistance in H. pylori infection is increasing worldwide and has become a leading cause for failure of treatment. Antibiotic susceptibility testing is very important to provide optimal regimens in a clinical setting. STUDY: We isolated 103 H. pylori strains from the gastric mucosa of H. pylori-infected patients from 2 areas in Vietnam (Ho Chi Minh and Hanoi) in 2008. Epsilometer test was used to determine the minimum inhibitory concentrations of amoxicillin, clarithromycin (CLR), metronidazole (MNZ), levofloxacin, and tetracycline. RESULTS: Among the 103 strains, the resistance rates were 0% (amoxicillin), 33% (CLR), 69.9% (MNZ), 18.4% (levofloxacin), and 5.8% (tetracycline). The resistant strains showed a high-level of resistance (≥ 256 µg/mL) to CLR, 23.5% (8/34), and MNZ, 29.1% (21/72). The resistance rate for CLR was significantly higher in Ho Chi Minh than in Hanoi (49% vs. 18.5%, P=0.001). Resistance to both CLR and MNZ was most commonly observed (24.3%). Two strains (1.9%) were resistant to 4 of the 5 antibiotics. No significant association was observed between antibiotic resistance rates and age, sex, or clinical outcomes of the patients. CONCLUSIONS: High incidence of resistance to CLR and MNZ suggests that standard triple therapies may not be useful as first-line treatment in Vietnam. Alternative strategies such as bismuth-based quadruple therapies or sequential therapy may be more effective in Vietnam.

A Brain-Permeable Aminosterol Regulates Cell Membranes to Mitigate the Toxicity of Diverse Pore-Forming Agents.

The molecular composition of the plasma membrane plays a key role in mediating the susceptibility of cells to perturbations induced by toxic molecules. The pharmacological regulation of the properties of the cell membrane has therefore the potential to enhance cellular resilience to a wide variety of chemical and biological compounds. In this study, we investigate the ability of claramine, a blood-brain barrier permeable small molecule in the aminosterol class, to neutralize the toxicity of acute biological threat agents, including melittin from honeybee venom and α-hemolysin from Staphylococcus aureus. Our results show that claramine neutralizes the toxicity of these pore-forming agents by preventing their interactions with cell membranes without perturbing their structures in a detectable manner. We thus demonstrate that the exogenous administration of an aminosterol can tune the properties of lipid membranes and protect cells from diverse biotoxins, including not just misfolded protein oligomers as previously shown but also biological protein-based toxins. Our results indicate that the investigation of regulators of the physicochemical properties of cell membranes offers novel opportunities to develop countermeasures against an extensive set of cytotoxic effects associated with cell membrane disruption.

Prevalence and antibiotic resistance of Salmonella isolated from poultry and its environment in the Mekong Delta, Vietnam.

BACKGROUND AND AIM: Salmonella is one of the leading causes of zoonotic and foodborne infectious outbreaks in humans and poultry and its associated environment is a potential reservoir of Salmonella. In recent years, the antibiotic resistance of bacteria, including Salmonella, has been increasing. This study aimed to investigate the prevalence and antibiotic resistance of Salmonella isolated from poultry, its environment, and the pest animals found at poultry farms and households of the Mekong Delta, Vietnam. MATERIALS AND METHODS: A total of 3,055 samples were collected from the broiler farms and households of the Mekong Delta from 2017 to 2020. Salmonella was isolated using conventional methods (culturing on selective agar - BPLS and biochemical test) and the isolates were examined for antibiotic resistance against 14 antibiotics using the disk diffusion method. RESULTS: Salmonella was isolated from 181 samples (5.92%), which included chicken feces (7.67%), pest animals (5.98%), and environmental samples (4.33%). The environmental samples comprised bedding (5.88%), feed (5.48%), and drinking water (0.70%). The prevalence of Salmonella was the highest in rats (15.63%) and geckos (12.25%) followed by ants (2.83%) and cockroaches (2.44%); however, Salmonella was not isolated from any fly species. Most of the isolates exhibited resistance to 1-9 antibiotics. The isolates were relatively resistant to chloramphenicol (62.98%), tetracycline (55.80%), ampicillin (54.14%), and sulfamethoxazole/trimethoprim (53.04%). Sixty-two multiple resistance patterns were found in the isolates, with ampicillin-cefuroxime-chloramphenicol-tetracycline- sulfamethoxazole/trimethoprim being the most frequent (7.18%). CONCLUSION: The chickens, husbandry environment, and pest animals at poultry farms and households were found to be important Salmonella sources in the Mekong Delta. Salmonella isolates from these sources also exhibited a wide-ranging resistance to antibiotics as well as several resistance patterns. Hence, biosecurity should be addressed in poultry farms and households to prevent cross-contamination and reduce the spread of Salmonella infections.

Squalamine and Its Derivatives Modulate the Aggregation of Amyloid-ß and α-Synuclein and Suppress the Toxicity of Their Oligomers.

The aberrant aggregation of proteins is a key molecular event in the development and progression of a wide range of neurodegenerative disorders. We have shown previously that squalamine and trodusquemine, two natural products in the aminosterol class, can modulate the aggregation of the amyloid-ß peptide (Aß) and of α-synuclein (αS), which are associated with Alzheimer's and Parkinson's diseases. In this work, we expand our previous analyses to two squalamine derivatives, des-squalamine and α-squalamine, obtaining further insights into the mechanism by which aminosterols modulate Aß and αS aggregation. We then characterize the ability of these small molecules to alter the physicochemical properties of stabilized oligomeric species in vitro and to suppress the toxicity of these aggregates to varying degrees toward human neuroblastoma cells. We found that, despite the fact that these aminosterols exert opposing effects on Aß and αS aggregation under the conditions that we tested, the modifications that they induced to the toxicity of oligomers were similar. Our results indicate that the suppression of toxicity is mediated by the displacement of toxic oligomeric species from cellular membranes by the aminosterols. This study, thus, provides evidence that aminosterols could be rationally optimized in drug discovery programs to target oligomer toxicity in Alzheimer's and Parkinson's diseases.

Correlation of ELISA method with three other automated serological tests for the detection of anti-SARS-CoV-2 antibodies.

Public health emergency of SARS-CoV-2 has facilitated diagnostic testing as a related medical countermeasure against COVID-19 outbreak. Numerous serologic antibody tests have become available through an expedited federal emergency use only process. This paper highlights the analytical characteristic of an ELISA based assay by AnshLabs and three random access immunoassay (RAIA) by DiaSorin, Roche, and Abbott that have been approved for emergency use authorization (EUA), at a tertiary academic center in a low disease-prevalence area. The AnshLabs gave higher estimates of sero-prevalence, over the three RAIA methods. For positive results, AnshLabs had 93.3% and 100% agreement with DiaSorin or Abbott and Roche respectively. For negative results, AnshLabs had 74.3% and 78.3% agreement with DiaSorin and Roche or Abbott respectively. All discrepant samples that were positive by AnshLabs and negative by RAIA tested positive by all-in-one step SARS-CoV-2 Total (COV2T) assay performed on the automated Siemens Advia Centaur XPT analyzer. None of these methods, however, are useful in early diagnosis of SARS-CoV-2.

Solution synchrotron x-ray diffraction reveals structural details of lipid domains in ternary mixtures.

The influence of cholesterol on lipid bilayer structure is significant and the effect of cholesterol on lipid sorting and phase separation in lipid-raft-forming model membrane systems has been well investigated by microscopy methods on giant vesicles. An important consideration however is the influence of fluorescence illumination on the phase state of these lipids and this effect must be carefully minimized. In this paper, we show that synchrotron x-ray scattering on solution lipid mixtures is an effective alternative technique for the identification and characterization of the l_{o} (liquid ordered) and l_{d} (liquid disordered) phases. The high intensity of synchrotron x rays allows the observation of up to 5 orders of diffraction from the l_{o} phase, whereas only two are clearly visible when the l_{d} phase alone is present. This data can be collected in approximately 1 min/sample , allowing rapid generation of phase data. In this paper, we measure the lamellar spacing in both the liquid-ordered and liquid-disordered phases simultaneously, as a function of cholesterol concentration in two different ternary mixtures. We also observe evidence of a third gel-phaselike population at 10-12 mol % cholesterol and determine the thickness of the bilayer for this phase. Importantly we are able to look at phase coexistence in the membrane independent of photoeffects.

Data evidencing slow anaerobic digestion in emergency treatment and disposal of infectious animal carcasses.

Burial of infectious and potentially infectious livestock and poultry animals is the most common response to an emergency situation. The data set summarizes 22-week-long experiment that simulates the environment found within conventional burial trenches for emergency disposal of animal carcasses, worldwide, sometimes with a topical application of quicklime as it is required in the Republic of Korea. This data set shows the rarely presented evidence of the extremely slow decay of animal carcasses. Besides visual evidence of no visible breakdown of carcass material, i.e., carcass (or carcass quarters and coarse cuts) still resembled the initial material at the end of the study, we present data characterizing the process. Specifically, temporal variations of digestate quality (pH, ammonia, volatile fatty acids), biogas production, and the persistence of odorous volatile organic compounds are summarized. The data provide important evidence of undesirable, slow progression of the digestion process. The evidence of failure to achieve practical endpoints with the anaerobic digestion provides the impetus for seeking alternative, improved methods of disposal that will be feasible in emergency context, such as aerated burial concept (Koziel et al., 2018 [1]).

Simulations suggest a constrictive force is required for Gram-negative bacterial cell division.

To divide, Gram-negative bacterial cells must remodel cell wall at the division site. It remains debated, however, whether this cell wall remodeling alone can drive membrane constriction, or if a constrictive force from the tubulin homolog FtsZ is required. Previously, we constructed software (REMODELER 1) to simulate cell wall remodeling during growth. Here, we expanded this software to explore cell wall division (REMODELER 2). We found that simply organizing cell wall synthesis complexes at the midcell is not sufficient to cause invagination, even with the implementation of a make-before-break mechanism, in which new hoops of cell wall are made inside the existing hoops before bonds are cleaved. Division can occur, however, when a constrictive force brings the midcell into a compressed state before new hoops of relaxed cell wall are incorporated between existing hoops. Adding a make-before-break mechanism drives division with a smaller constrictive force sufficient to bring the midcell into a relaxed, but not necessarily compressed, state.

Coarse-grained simulations of actomyosin rings point to a nodeless model involving both unipolar and bipolar myosins.

Cytokinesis in many eukaryotic cells is orchestrated by a contractile actomyosin ring. While many of the proteins involved are known, the mechanism of constriction remains unclear. Informed by the existing literature and new three-dimensional (3D) molecular details from electron cryotomography, here we develop 3D coarse-grained models of actin filaments, unipolar and bipolar myosins, actin cross-linkers, and membranes and simulate their interactions. Assuming that local force on the membrane results in inward growth of the cell wall, we explored a matrix of possible actomyosin configurations and found that node-based architectures like those presently described for ring assembly result in membrane puckers not seen in electron microscope images of real cells. Instead, the model that best matches data from fluorescence microscopy, electron cryotomography, and biochemical experiments is one in which actin filaments transmit force to the membrane through evenly distributed, membrane-attached, unipolar myosins, with bipolar myosins in the ring driving contraction. While at this point this model is only favored (not proven), the work highlights the power of coarse-grained biophysical simulations to compare complex mechanistic hypotheses.

Impact of maternal nutritional supplementation in conjunction with a breastfeeding support program on breastfeeding performance, birth, and growth outcomes in a Vietnamese population.

PURPOSE: This study aimed to evaluate the effects of maternal nutritional supplementation (MNS) in conjunction with a breastfeeding support program on birth outcomes and breastfeeding performance. METHODS: A total of 228 singleton Vietnamese mothers aged 20-35 years at 26-29 weeks of gestation with pre-pregnancy body mass index (BMI) < 25.0 kg/m2 were randomized to the intervention (n = 114), receiving MNS (252 kcal/day) daily up to 12 weeks postpartum and four breastfeeding education and support sessions or to the control (n = 114), receiving standards of care. RESULTS: The intervention was 2.09 times more likely to exclusively breastfeed over the 12 weeks than the control (95%CI: 1.05-4.13, p = .0358), after controlling for potential confounders. Infant's breast milk intake was significantly higher in the intervention than the control among mothers with baseline mid-upper arm circumference (MUAC) < 50th (p = .0251). Infants in the intervention had significantly higher birth weight (p = .0312), birth weight-for-age (p = .0141) and birth head circumference-for-age (p = .0487), and higher head circumference-for-age z-score (p = .0183) development over the postnatal period, compared with the control. CONCLUSIONS: Use of MNS and breastfeeding support improve birth outcomes and exclusive breastfeeding (EBF) rate in Vietnamese mothers. Additionally, it promotes breast milk production among mothers with lower baseline MUAC.

Lab-scale evaluation of aerated burial concept for treatment and emergency disposal of infectious animal carcasses.

Nearly 55,000 outbreaks of animal disease were reported to the World Animal Health Information Database between 2005 and 2016. To suppress the spread of disease, large numbers of animal mortalities often must be disposed of quickly and are frequently buried on the farm where they were raised. While this method of emergency disposal is fast and relatively inexpensive, it also can have undesirable and lasting impacts (slow decay, concerns about groundwater contamination, pathogens re-emergence, and odor). Following the 2010 foot-and-mouth disease outbreak, the Republic of Korea's National Institute of Animal Science funded research on selected burial alternatives or modifications believed to have potential to reduce undesirable impacts of burial. One such modification involves the injection of air into the liquid degradation products from the 60-70% water from decomposing carcasses in lined burial trenches. Prior to prototype development in the field, a laboratory-scale study of aerated decomposition (AeD) of poultry carcasses was conducted to quantify improvements in time of carcass decomposition, reduction of potential groundwater pollutants in the liquid products of decomposition (since trench liners may ultimately leak), and reduction of odorous VOCs emitted during decomposition. Headspace gases also were monitored to determine the potential for using gaseous biomarkers in the aerated burial trench exhaust stream to monitor completion of the decomposition. Results of the lab-scale experiments show that the mass of chicken carcasses was reduced by 95.0 ±â€¯0.9% within 3 months at mesophilic temperatures (vs. negligible reduction via mesophilic anaerobic digestion typical of trench burial) with concomitant reduction of biochemical oxygen demand (BOD; 99%), volatile suspended solids (VSS; 99%), total suspended solids (TSS; 99%), and total ammonia nitrogen (TAN; 98%) in the liquid digestate. At week #7 BOD and TSS in digestate met the U.S. EPA standards for treated wastewater discharge to surface water. Salmonella and Staphylococcus were inactivated by the AeD process after week #1 and #3, respectively. Five gaseous biomarkers: pyrimidine; p-cresol; phenol; dimethyl disulfide; and dimethyl trisulfide; were identified and correlated with digestate quality. Phenol was the best predictor of TAN (R = 0.96), BOD (R = 0.92), and dissolved oxygen (DO) (R = -0.91). Phenol was also the best predictor populations of Salmonella (R = 0.95) and aerobes (R = 0.88). P-cresol was the best predictor for anaerobes (R = 0.88). The off-gas from AeD will require biofiltration or other odor control measures for a much shorter time than anaerobic decomposition. The lab-scale studies indicate that AeD burial has the potential to make burial a faster, safer, and more environmentally friendly method for emergency disposal and treatment of infectious animal carcasses and that this method should be further developed via prototype-scale field studies.

Impact of maternal nutritional supplementation in conjunction with a breastfeeding support program during the last trimester to 12 weeks postpartum on breastfeeding practices and child development at 30 months old.

BACKGROUND: Maternal nutrition during pregnancy and breastfeeding is important for the healthy growth and development of the fetus and infant. PURPOSE: This study aimed to evaluate the long-term effects of a maternal milk supplementation (MMS) in conjunction with a breastfeeding support program on breastfeeding practices including duration of any breastfeeding and exclusive breastfeeding and child neurodevelopment outcomes at 30 months old. METHODS: We followed up the offspring of 204 Vietnamese women who completed a randomized controlled trial where the intervention group received MMS with a breastfeeding support program from the last trimester to 12 weeks postpartum while the control group received standard care. At 30 months postpartum, information on child feeding practices was collected and child neurodevelopment was assessed by the Bayley Scales of Infant and Toddler Development (Bayley-III). RESULTS: There was no significant difference in the duration of any breastfeeding (ABF) from birth between the groups. However, the intervention group had longer exclusive breastfeeding (EBF) duration (p = 0.0172), higher EBF rate at 6 months (p = 0.0093) and lower risk of discontinuing EBF (p = 0.0071) than the control. Children in the intervention group had significantly higher Bayley-III composite scores in the domains of cognitive (p = 0.0498) and motor (p = 0.0422) functions, as well as a tendency toward better social-emotional behavior (p = 0.0513) than children in the control group. The association between maternal intervention and child development was attenuated after further adjustment for birth weight but not EBF duration, suggesting that improvements in child development may be partially attributed to the benefits of prenatal nutrition supplementation on birth outcomes. CONCLUSIONS: MMS with breastfeeding support during late pregnancy and early postpartum significantly improved EBF practices. The intervention was also associated with improvements in neurodevelopment in children at 30 months old.

Efficacy of NH3 as a secondary barrier treatment for inactivation of Salmonella Typhimurium and methicillin-resistant Staphylococcus aureus in digestate of animal carcasses: Proof-of-concept.

Managing the disposal of infectious animal carcasses from routine and catastrophic disease outbreaks is a global concern. Recent research suggests that burial in lined and aerated trenches provides the rapid pathogen containment provided by burial, while reducing air and water pollution potential and the length of time that land is taken out of agricultural production. Survival of pathogens in the digestate remains a concern, however. A potential answer is a 'dual'-barrier approach in which ammonia is used as a secondary barrier treatment to reduce the risk of pathogen contamination when trench liners ultimately leak. Results of this study showed that the minimum inhibitory concentration (MIC) of NH3 is 0.1 M (~1,468 NH3-N mg/L), and 0.5 M NH3 (~7,340 NH3-N mg/L) for ST4232 & MRSA43300, respectively at 24 h and pH = 9±0.1 and inactivation was increased by increasing NH3 concentration and/or treatment time. Results for digestate treated with NH3 were consistent with the MICs, and both pathogens were completely inactivated within 24 h.

Method for sampling and analysis of volatile biomarkers in process gas from aerobic digestion of poultry carcasses using time-weighted average SPME and GC-MS.

A passive sampling method, using retracted solid-phase microextraction (SPME) - gas chromatography-mass spectrometry and time-weighted averaging, was developed and validated for tracking marker volatile organic compounds (VOCs) emitted during aerobic digestion of biohazardous animal tissue. The retracted SPME configuration protects the fragile fiber from buffeting by the process gas stream, and it requires less equipment and is potentially more biosecure than conventional active sampling methods. VOC concentrations predicted via a model based on Fick's first law of diffusion were within 6.6-12.3% of experimentally controlled values after accounting for VOC adsorption to the SPME fiber housing. Method detection limits for five marker VOCs ranged from 0.70 to 8.44ppbv and were statistically equivalent (p>0.05) to those for active sorbent-tube-based sampling. The sampling time of 30min and fiber retraction of 5mm were found to be optimal for the tissue digestion process.

Coarse-Grained Molecular Dynamics Simulations of the Bacterial Cell Wall.

Understanding mechanisms of bacterial sacculus growth is challenging due to the time and length scales involved. Enzymes three orders of magnitude smaller than the sacculus somehow coordinate and regulate their processes to double the length of the sacculus while preserving its shape and integrity, all over a period of tens of minutes to hours. Decades of effort using techniques ranging from biochemical analysis to microscopy have produced vast amounts of data on the structural and chemical properties of the cell wall, remodeling enzymes and regulatory proteins. The overall mechanism of cell wall synthesis, however, remains elusive. To approach this problem differently, we have developed a coarse-grained simulation method in which, for the first time to our knowledge, the activities of individual enzymes involved are modeled explicitly. We have already used this method to explore many potential molecular mechanisms governing cell wall synthesis, and anticipate applying the same method to other, related questions of bacterial morphogenesis. In this chapter, we present the details of our method, from coarse-graining the cell wall and modeling enzymatic activities to characterizing shape and visualizing sacculus growth.

One year experience using mycobacterial blood cultures to diagnose tuberculosis in patients with prolonged fever in Vietnam.

INTRODUCTION: To evaluate the use of mycobacterial blood cultures (MBC) in diagnosing tuberculosis (TB) in patients with prolonged fever admitted to a Vietnamese referral hospital. RESULTS: MBCs from 94 patients (66% male; median age 33 years; 75% HIV positive) were evaluated: 14 were mycobacterium positive (all HIV positive), and MBC was the only positive specimen in 9 cases (41%). Three positive cases were identified as Mycobacterium avium and the remaining M. tuberculosis (one case could not be identified). CONCLUSION: MBC can be a valuable additional method to diagnose TB, particularly in immunosuppressed HIV patients when sputum cannot be collected.