Capsular Strain Research Articles

Quantification and comparison of virulence and characteristics of different variants of carbapenemase-producing Klebsiella pneumoniae clinical isolates from Taiwan and the United States.

The emergence of Klebsiella pneumoniae carbapenemase (KPC)-producing strains is a challenge for clinicians. The characteristics and virulence of variants of KPC-producing K. pneumoniae isolates were evaluated. Five clinical isolates-three KPC subtypes from Taiwan (KPC2-TW, KPC3-TW, and KPC17-TW) and two clinical strains from the United States (US; KPC2-US, KPC3-US)-were included. Virulent traits and capsular serotypes were analyzed by Polymerase Chain Reaction (PCR). Serum killing, neutrophil phagocytosis, and mice lethargy studies were performed to evaluate virulence. Multilocus sequence typing (MLST) demonstrated that KPC2-TW and KPC17-TW belonged to sequence type (ST)11, and KPC2-US, KPC3-US, and KPC3-TW to ST258. KPC3-TW expressed capsular serotype K1, whereas the others were non-K1/K2/K5 isolates. MLST analysis indicated that ST11 strains were serum resistant, whereas ST258 isolates were serum sensitive. ST11 isolates exhibited significantly higher 15-minute phagocytic rates than ST258 isolates (70.28±16.68% vs. 34.88±10.52%, p<0.001). The capsular serotype K1 strain was more resistant to neutrophil phagocytosis than non-K1/K2/K5 isolates (27.1±10.23% vs. 54.46±20.94%, p=0.050). All KPC-producing strain variants from Taiwan and the US demonstrated less virulence in a mouse lethality study, where the LD50 ranged from approximately 10(6) colony-forming units (CFU) to >10(7)CFU. Immunological responses were not significantly correlated with KPC subtype; however, responses were associated with MLST and capsular serotype. Production of KPC itself was not associated with increased virulence despite different variants of KPC. The ST11 KPC-producing strain was resistant to serum killing, whereas capsular ss K1 was associated with resistance to neutrophil phagocytosis.

Klebsiella pneumoniae subsp. pneumoniae-bacteriophage combination from the caecal effluent of a healthy woman.

A sample of caecal effluent was obtained from a female patient who had undergone a routine colonoscopic examination. Bacteria were isolated anaerobically from the sample, and screened against the remaining filtered caecal effluent in an attempt to isolate bacteriophages (phages). A lytic phage, named KLPN1, was isolated on a strain identified as Klebsiella pneumoniae subsp. pneumoniae (capsular type K2, rmpA+). This Siphoviridae phage presents a rosette-like tail tip and exhibits depolymerase activity, as demonstrated by the formation of plaque-surrounding haloes that increased in size over the course of incubation. When screened against a panel of clinical isolates of K. pneumoniae subsp. pneumoniae, phage KLPN1 was shown to infect and lyse capsular type K2 strains, though it did not exhibit depolymerase activity on such hosts. The genome of KLPN1 was determined to be 49,037 bp (50.53 %GC) in length, encompassing 73 predicted ORFs, of which 23 represented genes associated with structure, host recognition, packaging, DNA replication and cell lysis. On the basis of sequence analyses, phages KLPN1 (GenBank: KR262148) and 1513 (a member of the family Siphoviridae, GenBank: KP658157) were found to be two new members of the genus “Kp36likevirus.”

Development of a conjugate vaccine against invasive pneumococcal disease based on capsular polysaccharides coupled with PspA/family 1 protein of Streptococcus pneumoniae

The efforts were focused on exploring alternative pneumococcal vaccine strategies, aimed at addressing the shortcomings of existing formulations, without compromising efficacy. Our strategy involved the use of the carrier protein, pneumococcal surface protein A (PspA), conjugated with capsular polysaccharides (CPS), to provide effective and non-serotype-dependent protection. In this study, we generated a stable Escherichia coli construct expressing functional PspA from a capsular serotype 6B strain and confirmed it belonging to family 1, which was conjugated with CPS. The distribution of anti-CPS antibody response was almost completely of IgG2a subclass followed by IgG3 and low level of IgG1 subclass, but that of anti-PspA IgG subclass antibodies was almost equal IgG1 and IgG2a subclasses. Though PspA was less conspicuous on the surface of pneumococci than the capsule, the antibodies induced with CPS-rPspA conjugate possessed more accessibility to the surface of Streptococcus pneumoniae serotype 6B and 19F (the same family 1 PspA). By survival experiment, the result suggested that the level of cross-protection after immunized with the conjugate was more measurable within the same family 1. The CPS-rPspA conjugate not only induced CPS-specific protection but also provided PspA specific cross-protection.

Soft-tissue balance in short and straight stem total hip arthroplasty.

The growing numbers of short stem hip implants have redefined total hip arthroplasty with new stem geometries and possible functional differences. Several systematic reviews have reported good clinical results with this new class of stems, although kinematic alterations are still unclear in many aspects. The good clinical results obtained at the authors' institution led to the current study. The authors hypothesized that the geometric alignment of the prosthetic components may be closer to the anatomy of the healthy hip joint, thus leading to better function and clinical satisfaction. An examination via finite element analysis was chosen to model the hip joint and virtually implant a short and a standard straight stem. Findings indicated that anchoring of the short stem allowed favorable positioning in the proximal femur, with the femoral head already in the center of the cup. This positioning was not possible for the straight stem, which required further reduction of the femur by a significant translation into the cup, leading to abnormal soft-tissue balancing. The results from the simulation showed an absolute average deviation of ligamentous fiber strains of 6% for the short stem in 30° of flexion and extension versus 29% and 36% for the standard straight stem in 30° of flexion and extension, respectively. A femoral neck guided orientation of the short stem implant seems to allow a more anatomical reconstruction and thus a more balanced hip in terms of the modeled soft tissues. In contrast, the straight stem alters the head position and induces nonphysiological capsular strains.

Capsular polysaccharides from Cryptococcus neoformans modulate production of neutrophil extracellular traps (NETs) by human neutrophils.

In the present study, we characterized the in vitro modulation of NETs (neutrophil extracellular traps) induced in human neutrophils by the opportunistic fungus Cryptococcus neoformans, evaluating the participation of capsular polysaccharides glucuronoxylomanan (GXM) and glucuronoxylomannogalactan (GXMGal) in this phenomenon. The mutant acapsular strain CAP67 and the capsular polysaccharide GXMGal induced NET production. In contrast, the wild-type strain and the major polysaccharide GXM did not induce NET release. In addition, C. neoformans and the capsular polysaccharide GXM inhibited PMA-induced NET release. Additionally, we observed that the NET-enriched supernatants induced through CAP67 yeasts showed fungicidal activity on the capsular strain, and neutrophil elastase, myeloperoxidase, collagenase and histones were the key components for the induction of NET fungicidal activity. The signaling pathways associated with NET induction through the CAP67 strain were dependent on reactive oxygen species (ROS) and peptidylarginine deiminase-4 (PAD-4). Neither polysaccharide induced ROS production however both molecules blocked the production of ROS through PMA-activated neutrophils. Taken together, the results demonstrate that C. neoformans and the capsular component GXM inhibit the production of NETs in human neutrophils. This mechanism indicates a potentially new and important modulation factor for this fungal pathogen.

Mechanism of lens capsular rupture following blunt trauma: a finite element study

Blunt impact on the eye could results in lens capsular rupture that allows foreign substances to enter into the lens and leads to cataract formation. This paper aimed to investigate the mechanism of lens capsular rupture using finite element (FE) method. A FE model of the human eye was developed to simulate dynamic response of the lens capsule to a BB (a standard 4.5-mm-diameter pellet) impact. Sensitivity studies were conducted to evaluate the effect of the parameters on capsular rupture, including the impact velocity, the elastic modulus of the lens, the thickness and the elastic modulus of the lens capsule. The results indicated that the lens was subjected to anterior compression and posterior intension when the eye was stricken by a BB pellet. The strain on the posterior capsule (0.392) was almost twice as much as that on the anterior capsule (0.207) at an impact velocity of 20 m/s. The strain on the capsule was proportional to the impact velocity, while the capsular strain showed no significant change when the lens modulus elastic varied with age. The findings confirmed that blunt traumatic capsular rupture is the result of shockwave propagation throughout the eye. The posterior capsule is subjected to greater tension in blunt trauma, which is the main cause that ruptures are more commonly found on the posterior capsule than the anterior capsule. Also, thinner thickness and lower elastic modulus would contribute to the posterior capsular rupture.

Cryptococcus neoformans is internalized by receptor-mediated or 'triggered' phagocytosis, dependent on actin recruitment.

Cryptococcosis by the encapsulated yeast Cryptococcus neoformans affects mostly immunocompromised individuals and is a frequent neurological complication in AIDS patients. Recent studies support the idea that intracellular survival of Cryptococcus yeast cells is important for the pathogenesis of cryptococcosis. However, the initial steps of Cryptococcus internalization by host cells remain poorly understood. Here, we investigate the mechanism of Cryptococcus neoformans phagocytosis by peritoneal macrophages using confocal and electron microscopy techniques, as well as flow cytometry quantification, evaluating the importance of fungal capsule production and of host cell cytoskeletal elements for fungal phagocytosis. Electron microscopy analyses revealed that capsular and acapsular strains of C. neoformans are internalized by macrophages via both ‘zipper’ (receptor-mediated) and ‘trigger’ (membrane ruffle-dependent) phagocytosis mechanisms. Actin filaments surrounded phagosomes of capsular and acapsular yeasts, and the actin depolymerizing drugs cytochalasin D and latrunculin B inhibited yeast internalization and actin recruitment to the phagosome area. In contrast, nocodazole and paclitaxel, inhibitors of microtubule dynamics decreased internalization but did not prevent actin recruitment to the site of phagocytosis. Our results show that different uptake mechanisms, dependent on both actin and tubulin dynamics occur during yeast internalization by macrophages, and that capsule production does not affect the mode of Cryptococcus uptake by host cells.

Biomechanical effects of cervical arthroplasty with U-shaped disc implant on segmental range of motion and loading of surrounding soft tissue

Various design concepts have been adopted in cervical disc prostheses, including sliding articulation and standalone configuration. This study aimed to evaluate the biomechanical effects of the standalone U-shaped configuration on the cervical spine. Based on an intact finite element model of C3-C7, a standalone U-shaped implant (DCI) was installed at C5-C6 and compared with a sliding articulation design (Prodisc-C) and an anterior fusion system. The range of motion (ROM), adjacent intradiscal pressure (IDP) and capsular ligament strain were calculated under different spinal motions. Compared to the intact configuration, the ROM at C5-C6 was reduced by 90% after fusion, but increased by 70% in the Prodisc-C model, while the maximum percentage change in the DCI model was 30% decrease. At the adjacent segments, up to 32% increase in ROM happened after fusion, while up to 34% decrease occurred in Prodisc-C model and 17% decrease in DCI model. The IDP increased by 11.6% after fusion, but decreased by 5.6 and 6.3% in the DCI and Prodisc-C model, respectively. The capsular ligament strain increased by 147% in Prodisc-C and by 13% in the DCI model. The DCI implant exhibited a high stress distribution. Spinal fusion resulted in compensatory increase of ROM at the adjacent sites, thereby elevating the IDP. Prodisc-C resulted in hyper-mobility at the operative site that led to an increase of ligament force and strain. The U-shaped implant could maintain the spinal kinematics and impose minimum influence on the adjacent soft tissues, despite the standalone configuration encountering the disadvantages of high stress distribution.

Novel Aspects of the Z and R3 Antigens of Streptococcus agalactiae Revealed by Immunological Testing

Group B streptococci (GBS) are important human and bovine pathogens which can be classified by a variety of phenotype- and gene-based techniques. The capsular polysaccharide and strain-variable, surface-anchored proteins are particularly important phenotypic markers. In an earlier study, a previously unrecognized protein antigen called Z was described. It was expressed by 27.2% of GBS strains from Zimbabwe, usually in combination with R3 protein expression. In this study, a putative Z-specific antiserum actually contained antibodies against two different antigens named Z1 and Z2; Z1 was >250 kDa in molecular mass. Z1, Z2, and R3 generated multiple stained bands on Western blots and showed similar chromatographic characteristics with respect to molecular mass, aggregate formation, and charge. Of 28 reference and prototype GBS strains examined, 8/28 (28.5%) isolates expressed one, two, or all three of the Z1, Z2, and R3 antigens; 4/28 expressed all three antigens; 2/28 expressed Z2 and R3; 1/28 expressed Z1 only; and 1/28 expressed R3 only. Twenty (71.5%) of the 28 isolates expressed none of the three antigens. Expression of one or more of these antigens was shown by isolates of the capsular polysaccharide types Ia, Ib, V, and IX and NT strains and occurred in combination with expression of various other strain-variable and surface-localized protein antigens. When used as serosubtype markers, Z1, Z2, and R3 affected existing GBS serotype designations for some of the isolates. For instance, the R3 reference strain Prague 10/84 (ATCC 49447) changed serotype markers from V/R3 to V/R3, Z1, and Z2. Other isolates may change correspondingly, implying consequences for GBS serotyping and research.

Finite element modeling of potential cervical spine pain sources in neutral position low speed rear impact

The rate of soft tissue sprain/strain injuries to the cervical spine and associated cost continue to be significant; however, the physiological nature of this injury makes experimental tests challenging while aspects such as occupant position and musculature may contribute to significant variability in the current epidemiological data. Several theories have been proposed to identify the source of pain associated with whiplash. The goal of this study was to investigate three proposed sources of pain generation using a detailed numerical model in rear impact scenarios: distraction of the capsular ligaments; transverse nerve root compression through decrease of the intervertebral foramen space; and potential for damage to the disc based on the extent of rotation and annulus fibre strain. There was significant variability associated with experimental measures, where the range of motion data overlapped ultimate failure data. Average data values were used to evaluate the model, which was justified by the use of average mechanical properties within the model and previous studies demonstrating predicted response and failure of the tissues was comparable to average response values. The model predicted changes in dimension of the intervertebral foramen were independent of loading conditions, and were within measured physiological ranges for the impact severities considered. Disc response, measured using relative rotation between intervertebral bodies, was below values associated with catastrophic failure or avulsion but exceeded the average range of motion values. Annulus fibre strains exceeded a proposed threshold value at three levels for 10g impacts. Capsular ligament strain increased with increasing impact severity and the model predicted the potential for injury at impact severities from 4g to 15.4g, when the range of proposed distraction corresponding to sub-catastrophic failure was exceeded, in agreement with the typically reported values of 9–15g. This study used an enhanced neck finite element model with active musculature to investigate three potential sources of neck pain resulting from rear impact scenarios and identified capsular ligament strain and deformation of the disc as potential sources of neck pain in rear impact scenarios.

Fluid movement and joint capsule strains due to flexion in rabbit knees

Diarthrodial joints are freely moveable joints containing synovial fluid (SF) within a connective tissue joint capsule that allows for low-friction and low-wear articulation of the cartilaginous ends of long bones. Biomechanical cues from joint articulation regulate synoviocyte and cartilage biology via joint capsule strain, in turn altering the composition of SF. Joint flexion is clinically associated with pain in knees with arthritis and effusion, with the nociception possibly originating from joint capsule strain. The hypothesis of this study was that knee fluid volume distribution and joint capsule strain are altered with passive flexion in the rabbit model. The aims were to (a) determine the volume distribution of fluid in the joint at different total volumes and with flexion of rabbit knees ex vivo, (b) correlate the volume distribution for the ex vivo model to in vivo data, and (c) determine the strains at different locations in the joint capsule with flexion. During knee flexion, ∼20% of anteriorly located joint fluid moved posteriorly, correlating well with the fluid motion observed in in vivo joints. Planar joint capsule principal strains were ∼100% (tension) in the proximal–distal direction and ∼−40% (shortening) in the circumferential direction, relative to the femur axis and 30° strain state. The joint capsule strains with flexion are consistent with the mechanics of the tendons and ligaments from which the capsule tissue is derived. The movement and mixing of SF volume with flexion determine the mechanical and biological fluid environment within the knee joint. Joint fluid movement and capsular strains affect synovial cell biology and likely modulate trans-synovial transport.

Facet Joint and Disc Kinematics During Simulated Rear Crashes With Active Injury Prevention Systems

Experimental and computational biomechanical analyses of simulated rear crashes. The objectives were to determine cervical facet joint and disc kinematics and ligament strains during simulated rear crashes with the Whiplash Protection System (WHIPS) and active head restraint (AHR) and to compare these data with those obtained with no head restraint (NHR). Previous biomechanical studies document abnormal cervical facet kinematics and potentially injurious ligament strains during simulated rear crashes with no injury prevention system. A human model of the neck, consisting of a neck specimen mounted to the torso of BioRID II and carrying a surrogate head and stabilized with muscle force replication, was subjected to simulated rear crashes in a WHIPS seat (n = 6, 12.0 g, ΔV 11.4 km/h) or AHR seat and subsequently with NHR (n = 6: 11.0 g, ΔV 10.2 km/h with AHR; 11.5 g, ΔV 10.7 km/h with NHR). Lower cervical spine facet and disc motions and ligament strains during the crashes were computed and average peak values statistically compared (P < 0.05) between WHIPS, AHR, and NHR. Average peak facet and disc translations and ligament strains could not be statistically differentiated between WHIPS and AHR or between AHR and NHR. WHIPS significantly reduced peak capsular ligament strain and peak disc separation at C6/C7 as compared with NHR. Facet compression at C6/C7 reached 2.9 mm with WHIPS, 1.9 mm with AHR, and 3.2 mm with NHR. WHIPS and AHR generally reduced peak disc separation and anterior longitudinal ligament strain as compared with NHR. WHIPS and AHR limited capsular strain below the subfailure threshold but did not protect against potential facet joint compression injuries, which may occur during or after contact of the head with the head restraint.

Axial head rotation increases facet joint capsular ligament strains in automotive rear impact

Axial head rotation prior to low speed automotive rear impacts has been clinically identified to increase morbidity and symptom duration. The present study was conducted to determine the effect of axial head rotation on facet joint capsule strains during simulated rear impacts. The study was conducted using a validated intact head to first thoracic vertebra (T1) computational model. Parametric analysis was used to assess effects of increasing axial head rotation between 0 and 60° and increasing impact severity between 8 and 24 km/h on facet joint capsule strains. Rear impacts were simulated by horizontally accelerating the T1 vertebra. Characteristics of the acceleration pulse were based on the horizontal T1 acceleration pulse from a series of simulated rear impact experiments using full-body post mortem human subjects. Joint capsule strain magnitudes were greatest in ipsilateral facet joints for all simulations incorporating axial head rotation (i.e., head rotation to the left caused higher ligament strain at the left facet joint capsule). Strain magnitudes increased by 47-196% in simulations with 60° head rotation compared to forward facing simulations. These findings indicate that axial head rotation prior to rear impact increases the risk of facet joint injury.

Production of Exopolysaccharides by Strains of Streptococcus thermophilus

Two strains of Streptococcus thermophilus producing capsular and capsular-ropy exopolysaccharides (EPS) were examined for their growth and EPS production in M17 medium supplemented with glucose, galactose or lactose and incubated at 30, 37 or 42&deg;C for 24 hours. Growth parameters (viable cells, OD, lactate production, pH) and EPS production were determined. Flow behavior of the EPS dispersions was assessed as a function of concentration and temperature. Culture growth during incubation was affected by types of sugar, temperature and time. Growth was enhanced by glucose, lactose and higher incubation temperature. EPS concentration in the medium was greater in the presence of glucose and galactose. Despite the restricted growth conditions, the capsular strain produced comparable levels of EPS to the capsular-ropy strain even under sub-optimal incubation temperature

Testing the efficiency of different treatments of subclinical Staphylococcus aureus mastitis in cows during the dry period

Mastitis is still the most common disorder which is present in diary cows. Changes in genetics, nutrition and milking equipment affect the incidence of subclinical and clinical forms of mastitis. Staphylococcus aureus is the causative agent of subclinical and clinical forms of mastitis. In the acute form it can cause malignant mastitis in the form of granulomatous and necrotic changes. Chronic forms of staphylococcal mastitis often develop as subclinical changes. Halting the entrance, the colonization and replication of the pathogen into the udder impose the constant need for regular milk controls and preventive and therapeutic measures in order to decrease the incidence of mastitis. A modern approach in the eradication and control of mastitis is immunoprophilaxis, aimed towards the innovation of new vaccines against the most common causes of mastitis. In this study we have applied the vaccine prepared with S. aureus isolated from milk taken from the experimental farm and the referent capsular strain. The vaccine was applied twice two months before calving in a dose of 5mL. The vaccine contained inactivated S. aureus JR3 bacterial cells in a quantity of 1 x 1010 cfu/mL and 5 mg SM capsule S. aureus 2286 strain. After vaccination of cows in late pregnancy, subclinical mastitis appears at a smaller frequency compared to the three experimental groups. To the first group of cows the antibiotic was applied intramammary, to the second group antibiotics were applied parenterally and intramammary and the third group served as the untreated control.

The Nonserotypeable Pneumococcus: Phenotypic Dynamics in the Era of Anticapsular Vaccines

Nonserotypeable pneumococci (NSP) are commonly carried by Australian Indigenous children in remote communities. The purpose of this study was to characterize carriage isolates of NSP from Indigenous children vaccinated with the seven-valent pneumococcal conjugate vaccine (PCV7) and to use these data to guide decisions on reporting of NSP. A total of 182 NSP were characterized by BOX typing, antibiogram analysis, and multilocus sequence typing (MLST) of common BOX types. NSP positive for the wzg capsule gene were analyzed by a multiplex PCR-based reverse line blot hybridization assay (mPCR/RLB-H) targeting capsule genes to determine the serotype. Among 182 NSP, 49 BOX types were identified. MLST of 10 representative isolates found 7 STs, including ST448 (which accounted for 11% of NSP). Non-penicillin susceptibility was evident in 51% of the isolates. Pneumococcal wzg sequences were detected in only 23 (13%) NSP, including 10 that contained an approximately 1.2-kb insert in the region. mPCR/RLB-H identified serotype 14 wzy sequences in all 10 NSP, and 1 also contained a serotype 3-specific wze sequence. Among the remaining 13 wzg-positive NSP, few belonged to the serotypes represented in PCV7. It appears that most NSP identified in Australian Indigenous children are from a true nonencapsulated lineage. Few NSP represented serotypes in PCV7 that suppress capsular expression. High rates of carriage and penicillin resistance and the occasional presence of capsule genes suggest a role for NSP in the maintenance and survival of capsulated pneumococci. To avoid the inflation of pneumococcal carriage and antibiotic resistance rates, in clinical trials, we recommend separate reporting of rates of capsular strains and NSP and the exclusion of data for NSP from primary analyses.

Evaluation of capsular and acapsular strains of S. aureus in an experimental brain abscess model

Brain abscesses are mainly caused by either direct or indirect inoculation of gram positive bacteria including Stapylococcus aureus ( S. aureus) or Streptococcus species into the central nervous system. In the present study, we aimed to compare potential changes in brain abscess pathogenesis induced by two different strains of S. aureus, namely the laboratory strain RN6390 and the clinical isolate Reynolds. Although the Reynolds strain was expected to be more resistant to eradication by the host, due to the existence of a polysaccharide capsule, and subsequently to be more virulent, instead we found parenchymal damage and mortality rates to be more prominent following RN6390 infection. In contrast, the Reynolds strain proliferated faster and induced early expression of the chemokine CXCL2, matrix metalloproteinase-9 (MMP-9), and complement 3a and C5. Furthermore, there were early and more abundant infiltration of PMNs, T cells and erythrocyte extravasation in brain abscesses induced by the Reynolds strain. However, several immune parameters were not different between the two strains during the later stages of the disease. These results suggest that capsular S. aureus can modulate innate immunity and complement system activation differently than the acapsular strain RN6390, and the early changes induced by Reynolds strain may have an important impact on survival.

Activity of tannins from Stryphnodendron adstringens on Cryptococcus neoformans: effects on growth, capsule size and pigmentation

BackgroundStryphnodendron adstringens (Mart.) Coville, Leguminosae, also known in Brazil as barbatimão, is rich in tannins and many flavan-3-ols and proanthocyanidins such as prodelphinidins and prorobinetinidins. Previous studies have demonstrated several pharmacological properties of tannins from barbatimão, including anti-candidal activity.MethodsThe antifungal activity of proanthocyanidin polymeric tannins from Stryphnodendron adstringens (subfraction F2.4) was evaluated against three strains of Cryptococcus neoformans with different capsule expressions, using the broth microdilution technique, light microscopy and transmission electron microscopy. The effect of subfraction F2.4 on C. neoformans and melanoma mammalian cells pigmentation was also evaluated.ResultsAlthough susceptibility assays revealed MIC values quite similar (between 2.5 and 5.0 μg/ml), analyses of MFC values revealing that the acapsular mutant Cap 67 was more susceptible to be killed by the subfraction F2.4 (MFC = 20 μg/ml) than the two tested capsular strains (T1-444 and ATCC 28957) (MFC > 160 μg/ml). Optical and electron microscopy experiments revealed relevant alterations in cell shape and size in all strains treated with 1 and 2.5 μg/ml of subfraction F2.4. Capsule size of the capsular strains decreased drastically after subfraction F2.4 treatment. In addition, ultrastructural alterations such as cell wall disruption, cytoplasm extraction, mitochondria swelling, increase in the number of cytoplasmic vacuoles and formation of membranous structures in the cytoplasm were also observed in treated yeasts. Incubation with subfraction F2.4 also decreased C. neoformans pigmentation, however, did not interfere in melanization of B16F10 mammalian cells.ConclusionOur data indicate that tannins extracted from S. adstringens interfered with growth, capsule size and pigmentation, all important virulence factors of C. neoformans, and may be considered as a putative candidate for the development of new antifungal agents.

Immunogenicity and protective efficacy of GroEL (hsp60) ofStreptococcus pneumoniaeagainst lethal infection in mice

The present study was carried out to evaluate the immunogenicity and protective efficacy of GroEL (hsp60) of Streptococcus pneumoniae, by expressing full length GroEL in heterologous host Escherichia coli BL21(DE3). PCR-amplified groEL was ligated in pQE 30 expression vector and subsequently transformed in E. coli DH5alpha strains. Cloning of groEL was confirmed by double digestion, followed by DNA sequencing. The His-tag containing recombinant GroEL was purified by Ni-NTA affinity chromatography. To determine the immunogenicity of GroEL, the mice were immunized by injecting 40 microg GroEL protein per mouse intraperitoneally. The results showed a significant increase in antibody titre and lymphocyte proliferation in animals immunized with GroEL as compared with control. Further, there was an appreciable increase in interleukin-2 (IL-2) and IL-4 production in lymphocytes isolated from immunized mice as compared with control. To determine the efficacy of GroEL in eliciting protection, the mice were challenged with the lethal dose of S. pneumoniae A66 type 3 capsular strain intranasally after the seventh day of the last immunization. In the GroEL-immunized mice the onset of death was insignificantly delayed and all the mice died by the seventh day postinfection.

A numerical study of the effect of axial acceleration on the responses of the cervical spine during low-speed rear-end impact

A detailed, three-dimensional, head-neck (vertebral segments CO to C7) finite element model - developed and validated previously on the basis of the actual geometry of a cadaveric specimen - was used to evaluate the effect of cranial acceleration on the response of the cervical spine during low-speed, rear-end impact. Analyses were carried out to compare the predicted overall and segmental rotations, peak disc stresses, and capsular ligament strains of each motion segment during whiplash with or without cranial acceleration applied on the C7 inferior surface. The results show that, in the first 150 ms, the variation curves of predicted segmental rotational angles, disc stresses, and capsular strains for each motion segment overlapped well under the two conditions. However, after 150 ms, the capsular strains of C2 to C6 without cranial acceleration applied on C7 were all obviously lower than those with cranial acceleration applied, but the segmental rotational angles and disc stresses remain unaffected. It was implied that, although without cranial acceleration applied on C7, the relatively simple head-neck model could be used to reflect effectively the biomechanical response of the cervical spine during the initial stage (i.e. 150 ms) under low-speed, rear-end impact as well as the whole-human-body dummy model.