Distribution of different genes responsible for invasive characteristics, detection of point mutations in capsular gene wchA and biofilm production among the invasive and non-invasive isolates of Streptococcus pneumoniae

BACKGROUND

Streptococcus pneumoniae continues to cause morbidity and mortality across the globe, with developing countries bearing the brunt of the disease. It is mainly responsible for meningitis, pneumonia and septicaemia primarily in children, elderly and immunocompromised persons. Colonisation and persistence in the human nasopharynx occur during early childhood, and it appears to be prerequisite for invasive pneumococcal disease (IPD). Factors that help in persistent colonisation and subsequent invasion are ill understood. Several virulence factors have been incriminated for nasopharyngeal carriage (NC) as well as for the manifestation of the pathogenesis of IPD.

MATERIALS AND METHODS

This study attempts to characterise the S. pneumoniae isolates through analysing the distribution of different virulence markers such as lytA, ply, pbpA, eno, psaA, amiA, ciaR and wchA among the isolates obtained from disease and NC. A total of 37 isolates which include 14 invasive and 23 non-invasive isolates were investigated by polymerase chain reaction to detect the genes. Eight representative isolates were investigated for mutations in wchA by DNA sequencing that may responsible for capsular variation.

RESULTS

Ply, pbpA, amiA and eno were observed in a greater percentage of invasive isolates than non-invasive isolates though these differences are not statistically significant. Other two genes ciaH and psaA did not show any significant difference between two groups of isolates. Biofilm production was significantly higher in than non-invasive isolates when compared to invasive isolates. Sequence analysis of wchA revealed three significant point mutations or single-nucleotide polymorphisms (SNPs) among the isolates of one particular cluster (cluster III). These SNPs are responsible for a non-synonymous mutation in wchA bringing in an amino acid change in WchA protein, which is a part of the capsule of S. pneumoniae. Notably, all the three isolates present in cluster III had these SNPs and all of them were isolated from ocular infections.

CONCLUSION

The results of our study implies a possible capsular variations among the isolates and this may have an impact on capsular typing.

Quasifree (p, 2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R^{3}B/LAND setup with incident beam energies in the range of 300-450  MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type ^{A}O(p,2p)^{A-1}N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.

Improving the Diagnosis of Scrub Typhus by Combining groEL Based Polymerase Chain Reaction and IgM ELISA

INTRODUCTION

Scrub typhus, an acute febrile illness, caused by Orientia tsutsugamushi, is an important cause of pyrexia of unknown origin in regions of endemicity. This disease is mostly underdiagnosed or misdiagnosed, the reasons for this being a combination of factors which include clinical manifestations that can mimic other infections, lack of easy and reliable diagnostic methods and variation among strains in endemic areas. Hence, easy and reliable methods of diagnosis will contribute to rapid identification and treatment of the infection.

AIM

The aim of the study was to compare four different methods of detection of scrub typhus and to identify one single test or a combination of tests detecting maximum number of cases.

MATERIALS AND METHODS

One hundred and forty-five suspected scrub typhus cases were included in this study. Duration of fever and presence of eschar in each patient was noted down. Enzyme-Linked Immunosorbent Assay (ELISA) to detect Immunoglobulin M (IgM) antibodies and Polymerase Chain Reaction (PCR) to detect three genes of Orientia, namely, 56 kDa, 16S rRNA, and groEL were done on these samples. The results of each test were analyzed to identify the test picking up maximum number of positive samples. Statistical analysis was performed using Chi-square test. The level of significance was set at p<0.05.

RESULTS

These tests showed that IgM ELISA (93%) and PCR (68%) picked up maximum number of positives. Statistical analysis performed using Chi-square test between the diagnostic assays showed that the p - value <0.001 was significant for IgM ELISA. Among the molecular markers, p-value was significant (<0.001) for groEL PCR. Further analysis of eschar positivity and duration of fever also showed that groEL PCR could detect DNA of the bacterium even in cases with 10 days of fever and this PCR was the best among the molecular markers used to detect the infection.

CONCLUSION

This study suggests that IgM detection by ELISA and conventional groEL PCR, either in combination or alone, depending on the duration of fever, would enhance the diagnosis of scrub typhus.

Nuclear Force Imprints Revealed on the Elastic Scattering of Protons with ^{10}C

How does nature hold together protons and neutrons to form the wide variety of complex nuclei in the Universe? Describing many-nucleon systems from the fundamental theory of quantum chromodynamics has been the greatest challenge in answering this question. The chiral effective field theory description of the nuclear force now makes this possible but requires certain parameters that are not uniquely determined. Defining the nuclear force needs identification of observables sensitive to the different parametrizations. From a measurement of proton elastic scattering on ^{10}C at TRIUMF and ab initio nuclear reaction calculations, we show that the shape and magnitude of the measured differential cross section is strongly sensitive to the nuclear force prescription.

Investigation of the ^{10}Li shell inversion by neutron continuum transfer reaction

This Letter reports a study of the highly debated ^{10}Li structure through the d(^{9}Li,p)^{10}Li one-neutron transfer reaction at 100 MeV. The ^{10}Li energy spectrum is measured up to 4.6 MeV and angular distributions corresponding to different excitation energy regions are reported for the first time. The comparison between data and theoretical predictions, including pairing correlation effects, shows the existence of a p_{1/2} resonance at 0.45±0.03  MeV excitation energy, while no evidence for a significant s-wave contribution close to the threshold energy is observed. Moreover, two high-lying structures are populated at 1.5 and 2.9 MeV. The corresponding angular distributions suggest a significant s_{1/2} partial-wave contribution for the 1.5 MeV structure and a mixing of configurations at higher energy, with the d_{5/2} partial-wave contributing the most to the cross section.

Measurement of Excitation Spectra in the ^{12}C(p,d) Reaction near the η^{'} Emission Threshold

Excitation spectra of ^{11}C are measured in the ^{12}C(p,d) reaction near the η^{'} emission threshold. A proton beam extracted from the synchrotron SIS-18 at GSI with an incident energy of 2.5 GeV impinges on a carbon target. The momenta of deuterons emitted at 0° are precisely measured with the fragment separator (FRS) operated as a spectrometer. In contrast to theoretical predictions on the possible existence of deeply bound η^{'}-mesic states in carbon nuclei, no distinct structures are observed associated with the formation of bound states. The spectra are analyzed to set stringent constraints on the formation cross section and on the hitherto barely known η^{'}-nucleus interaction.

Proton Distribution Radii of ^{12-19}C Illuminate Features of Neutron Halos

Proton radii of ^{12-19}C densities derived from first accurate charge changing cross section measurements at 900A  MeV with a carbon target are reported. A thick neutron surface evolves from ∼0.5  fm in ^{15}C to ∼1  fm in ^{19}C. The halo radius in ^{19}C is found to be 6.4±0.7  fm as large as ^{11}Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

Dengue virus infection: Need for appropriate laboratory tests for diagnosis and management of the condition in children during an outbreak

BACKGROUND

Outbreaks of dengue infection occur in several parts of India with clockwork precision closely related to changing seasons. Most recent outbreak in Puducherry occurred between October 2012 and January 2013, affected a sizable pediatric population. A prospective study was done to characterize the demographic, diagnostic and clinical profile of pediatric patients in a tertiary care center in Puducherry.

MATERIALS AND METHODS

Data of patients serologically positive for either dengue NS1 antigen or anti-dengue IgM antibodies were analyzed. Duration of fever, platelet count, complications, risk factors, morbidity and mortality were analyzed.

RESULTS

Among pediatric cases with fever who were screened for NS1/IgM antibody during the recent outbreak, 161 (37.5%) tested positive. NS1 was detected in 85% while 5.5% tested positive for IgM and 3% for IgG. Few (4.9%) tested positive for both NS1 and IgM and 1.2% were positive for both NS1 and IgG. The mean age was 6 years of which 9% were <1-year, the youngest being 1-month old infant. Mean duration of fever was 4 days. Vomiting was associated in 42% of cases. Thrombocytopenia (51%) and hepatomegaly (41%) were two major observations. Among the NS1 positive cases, 49% had thrombocytopenia. IgM alone and NS1 with IgM were associated with thrombocytopenia in 67% and 78% respectively. 14 children had complications of dengue shock syndrome, and four had dengue hemorrhagic fever. Totally, 22 of the children had platelet transfusion. There was no mortality reported among any of these children.

CONCLUSION

Combination of clinical findings and rapid NS1, IgM detection helped in confirming the diagnosis for appropriate management of dengue in children.

Predebridement wound culture in open fractures does not predict postoperative wound infection: A pilot study

BACKGROUND

There is confusion in the current literature regarding the value of obtaining predebridement wound cultures in the management of open fractures with several studies reporting contrasting results. We undertook a pilot study to determine the initial bacterial flora of open fractures in our environment and determine the correlation between subsequent wound infection if any, and the initial bacterial flora.

MATERIALS AND METHODS

Initial/predebridement wound swabs were obtained for 32 patients with open fractures. Patients underwent a debridement of the open wound and preliminary stabilization of fracture in the operating room within 24 h. Postdebridement wound cultures were obtained at 48 h and repeated subsequently, if indicated, during the follow-up period. The antibiotic therapy was modified based on the culture reports.

RESULTS

Initial wound swab culture showed bacterial contamination in 18 patients (56%); 14 patients (44%) developed an infection in the immediate postoperative period or during follow-up. Age, gender, co-morbid medical condition, delay in presentation, and grade of open fracture were not found to be predictors of postoperative infection. No patient had an infection with the same organism, which was present in the initial culture.

CONCLUSION

The findings of this study suggest that the initial flora are not the infecting organisms in the open fracture wounds, and predebridement wound cultures have no value in predicting postdebridement wound infection.

Simultaneous gut colonisation and infection by ESBL-producing Escherichia coli in hospitalised patients

BACKGROUND

Extended spectrum betalactamase (ESBL)-producing organisms are a major cause of hospital-acquired infections. ESBL-producing Escherichia coli (E. coli) have been recovered from the hospital environment. These drug-resistant organisms have also been found to be present in humans as commensals. The present investigation intended to isolate ESBL-producing E. coli from the gut of already infected patients; to date, only a few studies have shown evidence of the gut microflora as a major source of infection.

AIMS

This study aimed to detect the presence of ESBL genes in E.coli that are isolated from the gut of patients who have already been infected with the same organism.

METHODS

A total of 70 non-repetitive faecal samples were collected from in-patients of our hospital. These in-patients were clinically diagnosed and were culture-positive for ESBL-producing E. coli either from blood, urine, or pus. Standard microbiological methods were used to detect ESBL from clinical and gut isolates. Genes coding for major betalactamase enzymes such as bla CTX-M , bla TEM, and bla SHV were investigated by polymerase chain reaction (PCR).

RESULTS

ESBL-producing E. coli was isolated from 15 (21 per cent) faecal samples of the 70 samples that were cultured. PCR revealed that out of these 15 isolates, the bla CTX-M gene was found in 13 (86.6 per cent) isolates, the bla TEM was present in 11 (73.3 per cent) isolates, and bla SHV only in eight (53.3 per cent) isolates. All 15 clinical and gut isolates had similar phenotypic characters and eight of the 15 patients had similar pattern of genes (bla TEM, bla CTX-M, and bla SHV) in their clinical and gut isolates.

CONCLUSION

Strains with multiple betalactamase genes that colonise the gut of hospitalised patients are a potential threat and it may be a potential source of infection.

Evidence of soft dipole resonance in ^{11}li with isoscalar character

The first conclusive evidence of a dipole resonance in ^{11}Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03±0.03 MeV with a width of 0.51±0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in ^{11}Li. The first ab initio calculations in the coupled cluster framework are also presented.