Screening and treatment of tuberculosis among pregnant women in Stockholm, Sweden, 2016-2017.

Swedish National tuberculosis (TB) guidelines recommend screening of active and latent TB (LTBI) among pregnant women (PW) from high-endemic countries or with previous exposure to possibly improve early detection and treatment.We evaluated cascade of care of a newly introduced TB screening programme of pregnant women in Stockholm county in 2016-2017. The algorithm included clinical data and Quantiferon (QFT) at the Maternal Health Care clinics and referral for specialist care upon positive test or TB symptoms.About 29 000 HIV-negative pregnant women were registered yearly, of whom 11% originated from high-endemic countries. In 2016, 72% of these were screened with QFT, of which 22% were QFT positive and 85% were referred for specialist care. In 2017, corresponding figures were 64%, 19% and 96%, respectively. The LTBI treatment rate among all QFT-positive pregnant women increased from 24% to 37% over time. Treatment completion with mainly rifampicin post-partum was 94%. Of the 69 registered HIV-positive pregnant women, 78% originated from high-endemic countries. Of these, 72% where screened with QFT and 15% were positive, but none was treated for LTBI. 9 HIV-negative active pulmonary TB cases were detected (incidence: 215/100 000). None had been screened for TB prior to pregnancy and only one had sought care due to symptoms.Systematic TB screening of pregnant women in Stockholm was feasible with a high yield of unknown LTBI and mostly asymptomatic active TB. Optimised routines improved referrals to specialist care. Treatment completion of LTBI was very high. Our findings justify TB screening of this risk group for early detection and treatment.

Quality of life of patients on treatment for latent tuberculosis infection: a mixed-method study in Stockholm, Sweden.

BACKGROUND: Unlike active tuberculosis, latent tuberculosis infection (LTBI) is asymptomatic and often considered not to affect the health-related quality of life (HRQoL) of patients. However, being diagnosed with and treated for LTBI can be associated with adverse clinical evens such side effects of treatment as well as psychosocial challenges. Therefore, the aims of this study were to qualitatively explore patients' experiences during diagnosis and treatment of LTBI in Stockholm measure their HRQoL, and contrast and merge the results to better understand how the HRQoL of these patients is affected. METHODS: LTBI patients who were treated in Stockholm during September 2017 and June 2018and who fulfilled the inclusion criteria were invited to fill a survey that included a HRQoL instrument, EQ-5D-3 L, and a mental health screening instrument, RHS-15. After filling the survey, a subset of these patients was asked to participate in an interview with open-ended questions that focused on their experiences during the diagnosis and treatment. RESULTS: In total 108 participants filled that survey and interviews were conducted with 20 patients. Patients scored relatively high on EQ-5D: the scores of utility and VAS scale are similar to those reported by the general population of Stockholm. Very few patients reported problems on the physical health domains of EQ-5D which was supported by the quantitative data that showed no effect on physical health and usual activity. Thirty-eight percent screened positive for RHS-15 and 27.8% reported problems with anxiety/depression domain of EQ-5D which could be related to many stressing factors mentioned in the interviews such as: fear and distress related to lack of clarity about LTBI diagnosis, perceived risk of infecting others and uncertainties about the future. CONCLUSION: The quantified HRQoL of LTBI patients in Stockholm is similar to the general population and there is thus no HRQoL decrements that is detectable with EQ-5D. However, the study reinforces the importance of tackling anxiety and fear and ensuring good health information for persons diagnosed with and treated for LTBI.

Crystal structures exploring the origins of the broader specificity of escherichia coli heat-labile enterotoxin compared to cholera toxin.

Cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) are structurally and functionally related and share the same primary receptor, the GM1 ganglioside. Despite their extensive similarities, these two toxins exhibit distinct ligand specificities, with LT being more promiscuous than CT. Here, we have attempted to rationalize the broader binding specificity of LT and the subtle differences between the binding characteristics of LTs from human and porcine origins (mediated by their B subunit pentamers, hLTB and pLTB, respectively). The analysis is based on two crystal structures of pLTB in complexes with the pentasaccharide of its primary ligand, GM1, and with neolactotetraose, the carbohydrate determinant of a typical secondary ligand of LTs, respectively. Important molecular determinants underlying the different binding specificities of LTB and CTB are found to be contributed by Ser95, Tyr18 and Thr4 (or Ser4 of hLTB), which together prestabilize the binding site by positioning Lys91, Glu51 and the adjacent loop region (50-61) containing Ile58 for ligand binding. Glu7 and Ala1 may also play an important role. Many of these residues are closely connected with a recently identified second binding site, and there appears to be cross-talk between the two sites. Binding to N-acetyllactosamine-terminated receptors is further augmented by Arg13 (present in pLT and some hLT variants), as previously predicted.

Campylobacter jejuni colonization in wild birds: results from an infection experiment.

Campylobacter jejuni is a common cause of bacterial gastroenteritis in most parts of the world. The bacterium has a broad host range and has been isolated from many animals and environments. To investigate shedding patterns and putative effects on an avian host, we developed a colonization model in which a wild bird species, the European Robin Erithacus rubecula, was inoculated orally with C. jejuni from either a human patient or from another wild bird species, the Song Thrush Turdus philomelos. These two isolates were genetically distinct from each other and provoked very different host responses. The Song Thrush isolate colonized all challenged birds and colonization lasted 6.8 days on average. Birds infected with this isolate also showed a transient but significant decrease in body mass. The human isolate did not colonize the birds and could be detected only in the feces of the birds shortly after inoculation. European Robins infected with the wild bird isolate generated a specific antibody response to C. jejuni membrane proteins from the avian isolate, which also was cross-reactive to membrane proteins of the human isolate. In contrast, European Robins infected with the human isolate did not mount a significant response to bacterial membrane proteins from either of the two isolates. The difference in colonization ability could indicate host adaptations.

Carbohydrate binding specificities and crystal structure of the cholera toxin-like B-subunit from Citrobacter freundii.

Enterotoxigenic Escherichia coli and Vibrio cholerae are well known causative agents of severe diarrheal diseases. Both pathogens produce AB(5) toxins, with one enzymatically active A-subunit and a pentamer of receptor-binding B-subunits. The primary receptor for both B-subunits is the GM1 ganglioside (Galbeta3GalNAcbeta4(NeuAcalpha3)Galbeta4GlcbetaCer), but the B-subunits from porcine isolates of E. coli also bind neolacto-(Galbeta4GlcNAcbeta-)terminated glycoconjugates and the B-subunits from human isolates of E. coli (hLTB) have affinity for blood group A type 2-(GalNAcalpha3(Fucalpha2)Galbeta4GlcNAcbeta-)terminated glycoconjugates. A B-subunit with 73% sequence identity to the B-subunits of cholera toxin and the heat-labile toxin of E. coli is produced by certain strains of enteropathogenic E. coli and by Citrobacter freundii. This C. freundii B-subunit (CFXB) has now been expressed in V. cholerae, and isolated in high yields. Glycosphingolipid binding studies show that CFXB binds to the GM1 ganglioside with high affinity. In addition, CFXB has high affinity for both neolacto-terminated and blood group A type 2-terminated glycoconjugates. The crystal structure of the pentameric arrangement of C. freundii B-subunits display high structural similarity with related proteins from E. coli and V. cholerae and oligosaccharide binding sites can be identified on the protein surface. Small changes in the 88-95 loop connecting the GM1 and blood group A binding sites explains the minor changes in affinity seen for these two ligands. However, the enhanced affinity of CFXB for neolacto-terminated structures can be sought in the Lys34Tyr substitution affording additional hydrogen bond interactions between the tyrosyl side chain and the GlcNAcbeta3Galb4Glcbeta1 segment of neolactotetraosylceramide via bridging water molecules.

No direct binding of the heat-labile enterotoxin of Escherichia coli to E. coli lipopolysaccharides.

A novel carbohydrate binding site recognizing blood group A and B determinants in a hybrid of cholera toxin and Escherichia coli heat-labile enterotoxin B-subunits (termed LCTBK) has previously been described, and also the native heat-labile enterotoxin bind to some extent to blood group A/B terminated glycoconjugates. The blood group antigen binding site is located at the interface of the B-subunits. Interestingly, the same area of the B-subunits has been proposed to be involved in binding of the heat-labile enterotoxin to lipopolysaccharides on the bacterial cell surface. Binding of the toxin to lipopolysaccharides does not affect the GM1 binding capacity. The present study aimed at characterizing the relationship between the blood group A/B antigen binding site and the lipopolysaccharide binding site. However, no binding of the B-subunits to E. coli lipopolysaccharides in microtiter wells or on thin-layer chromatograms was obtained. Incubation with lipopolysaccharides did not affect the binding of the B-subunits of heat-labile enterotoxin of human isolates to blood group A-carrying glycosphingolipids, indicating that the blood group antigen site is not involved in LPS binding. However, the saccharide competition experiments showed that GM1 binding reduced the affinity for blood group A determinants and vice versa, suggesting that a concurrent occupancy of the two binding sites does not occur. The latter finding is related to a connection between the blood group antigen binding site and the GM1 binding site through residues interacting with both ligands.

Sulfatide recognition by colonization factor antigen CS6 from enterotoxigenic Escherichia coli.

The first step in the pathogenesis of enterotoxigenic Escherichia coli (ETEC) infections is adhesion of the bacterium to the small intestinal epithelium. Adhesion of ETEC is mediated by a number of antigenically distinct colonization factors, and among these, one of the most commonly detected is the non-fimbrial adhesin coli surface antigen 6 (CS6). The potential carbohydrate recognition by CS6 was investigated by binding of recombinant CS6-expressing E. coli and purified CS6 protein to a large number of variant glycosphingolipids separated on thin-layer chromatograms. Thereby, a highly specific binding of the CS6-expressing E. coli, and the purified CS6 protein, to sulfatide (SO(3)-3Galbeta1Cer) was obtained. The binding of the CS6 protein and CS6-expressing bacteria to sulfatide was inhibited by dextran sulfate, but not by dextran, heparin, galactose 4-sulfate or galactose 6-sulfate. When using recombinantly expressed and purified CssA and CssB subunits of the CS6 complex, sulfatide binding was obtained with the CssB subunit, demonstrating that the glycosphingolipid binding capacity of CS6 resides within this subunit. CS6-binding sulfatide was present in the small intestine of species susceptible to CS6-mediated infection, e.g. humans and rabbits, but lacking in species not affected by CS6 ETEC, e.g. mice. The ability of CS6-expressing ETEC to adhere to sulfatide in target small intestinal epithelium may thus contribute to virulence.

The major subunit, CfaB, of colonization factor antigen i from enterotoxigenic Escherichia coli is a glycosphingolipid binding protein.

Bacterial adherence to mucosal surfaces is an important virulence trait of pathogenic bacteria. Adhesion of enterotoxigenic Escherichia coli (ETEC) to the intestine is mediated by a number of antigenically distinct colonization factors (CFs). One of the most common CFs is CFA/I. This has a fimbrial structure composed of a major repeating subunit, CfaB, and a single tip subunit, CfaE. The potential carbohydrate recognition by CFA/I was investigated by binding CFA/I-fimbriated bacteria and purified CFA/I fimbriae to a large number of variant glycosphingolipids separated on thin-layer chromatograms. For both fimbriated bacteria and purified fimbriae, specific interactions could be identified with a number of nonacid glycosphingolipids. These included glucosylceramide, lactosylceramide with phytosphingosine and/or hydroxy fatty acids, neolactotetraosylceramide, gangliotriaosylceramide, gangliotetraosylceramide, the H5 type 2 pentaglycosylceramide, the Lea-5 glycosphingolipid, the Lex-5 glycosphingolipid, and the Ley-6 glycosphingolipid. These glycosphingolipids were also recognized by recombinant E. coli expressing CFA/I in the absence of tip protein CfaE, as well as by purified fimbriae from the same strain. This demonstrates that the glycosphingolipid-binding capacity of CFA/I resides in the major CfaB subunit.