A case of Mycobacterium goodii prosthetic valve endocarditis in a non-immunocompromised patient: use of 16S rDNA analysis for rapid diagnosis

Background: Mycobacterium goodii is a rare cause of significant infection. M. goodii has mainly been associated with lymphadenitis, cellulitis, osteomyelitis, and wound infection. Case presentation: A case of a 76-year-old Caucasian female is presented. The patient developed a prosthetic valve endocarditis caused by M. goodii. She had also suffered from severe neurological symptoms related to a septic emboli that could be demonstrated as an ischemic lesion found on CT of the brain. Transesophageal echocardiography verified a large vegetation attached to the prosthetic valve. Commonly used blood culture bottles showed growth of the bacteria after 3 days. Conclusions: Although M. goodii is rarely involved in these kinds of severe infections, rapidly growing mycobacteria should be recognized during conventional bacterial investigations and identified by molecular tools such as analysis of 16S rDNA. Species identification of nontuberculous mycobacteria is demanding and is preferably done in collaboration with a mycobacterial laboratory. An early diagnosis provides the opportunity for adequate treatment. In the present case, prolonged antimicrobial treatment and surgery with replacement of the prosthetic valve was successful

What Is Resistance? Impact of Phenotypic versus Molecular Drug Resistance Testing on Therapy for Multi- and Extensively Drug-Resistant Tuberculosis.

Rapid and accurate drug susceptibility testing (DST) is essential for the treatment of multi- and extensively drug-resistant tuberculosis (M/XDR-TB). We compared the utility of genotypic DST assays with phenotypic DST (pDST) using Bactec 960 MGIT or Löwenstein-Jensen to construct M/XDR-TB treatment regimens for a cohort of 25 consecutive M/XDR-TB patients and 15 possible anti-TB drugs. Genotypic DST results from Cepheid GeneXpert MTB/RIF (Xpert) and line probe assays (LPAs; Hain GenoType MTBDRplus 2.0 and MTBDRsl 2.0) and whole-genome sequencing (WGS) were translated into individual algorithm-derived treatment regimens for each patient. We further analyzed if discrepancies between the various methods were due to flaws in the genotypic or phenotypic test using MIC results. Compared with pDST, the average agreement in the number of drugs prescribed in genotypic regimens ranged from just 49% (95% confidence interval [CI], 39 to 59%) for Xpert and 63% (95% CI, 56 to 70%) for LPAs to 93% (95% CI, 88 to 98%) for WGS. Only the WGS regimens did not contain any drugs to which pDST showed resistance. Importantly, MIC testing revealed that pDST likely underestimated the true rate of resistance for key drugs (rifampin, levofloxacin, moxifloxacin, and kanamycin) because critical concentrations (CCs) were too high. WGS can be used to rule in resistance even in M/XDR strains with complex resistance patterns, but pDST for some drugs is still needed to confirm susceptibility and construct the final regimens. Some CCs for pDST need to be reexamined to avoid systematic false-susceptible results in low-level resistant isolates

Gastric and enteric Helicobacter species in animal models and in the human colon

The Gram-negative genus of Helicobacter consists of many bacterial species that colonize a wide range of animal hosts. The genus can be divided into gastric species that colonize the stomach, and enteric species that preferentially colonize the colon and biliary tree of various animal hosts. Helicobacter pylori cause gastritis, gastro-duodenal ulcer disease and gastric adenocarcinoma and lymphoma in infected individuals. Enteric Helicobacter species cause typhlocolitis, hepatitis and neoplasia of the colon and liver in various rodent models of disease. A novel guinea pig model of H. pylori infection was developed and the infection was found to cause severe inflammatory changes in the stomach and an H. pylori-specific antibody response in infected animals after 3 and 7 weeks of infection. Different strains of H. pylori, with regards to the cagA gene and VacA protein expression, could infect mice. The infection was found to cause an H. pylori specific antibody response in mice infected with strains expressing the VacA protein. Simultaneous co-infection of mice with seven different strains of H. pylori showed evidence of colonization with two different strains. Gastritis was not apparent in mice infected with H. pylori for up to 17 weeks. H. pylori infection was found to lead to substantially more gastritis and serologic antibody response in guinea pigs than in mice. In guinea pigs, the infection was found to cause an elevation of acute-phase protein C3 and cholesterol, which could constitute a possibility to study an H. pylori trigger of extra-alimentary diseases. Helicobacter ganmani was isolated from interleukin-10 deficient mice with typhlocolitis and hepatitis. Analysis of serum antibodies demonstrated an immune response against H. ganmani in animals with disease. This recently described species of Helicobacter was implicated as the possible source of the disease found among the animals but this link needs to be evaluated in a controlled, experimental set-up. The importance of using Helicobacter-free animals for a wide range of experiments, especially when using immune deficient animals, needs to be stressed. Human colon biopsies from 20 patients with inflammatory bowel disease and other ailments were investigated for Helicobacter colonization. DNA resembling H. pylori was detected in two, Helicobacter cholecystus in one and Helicobacter muridarum in one patient. The latter two species have previously not been described in human tissue. No apparent link was found between the detection of Helicobacter species and human inflammatory bowel disease. In summary, this thesis deals with development and optimization of two animal models for H. pylori infection and also explores the role of enteric Helicobacter species in human and animal disease

Comparative study of Helicobacter pylori infection in guinea pigs and mice - elevation of acute-phase protein C3 in infected guinea pigs

Eighteen Dunkin-Hartley guinea pigs and 50 NMRI mice were inoculated with Helicobacter pylori and the infection followed by culture, histopathology, antibody response, and plasma levels of the acute-phase proteins albumin, C3, and transferrin for up to 7 weeks. The immune response to H. pylori surface proteins was studied by an enzyme immunoassay (EIA) and Western immunoblot and the plasma levels of albumin, C3, and transferrin were analyzed by single radial immunodiffusion. Guinea pigs had a more severe gastritis and a higher EIA immune response than NMRI mice. Serum C3 levels were elevated in infected guinea pigs after 3 and 7 weeks indicating a systemic inflammatory response and a possible link between H. pylori infection and extragastric manifestations such as vasculitis associated with atherosclerosis. Serum cholesterol levels were analyzed in guinea pigs at 7 weeks and indicated a higher level in H. pylori-infected than in control animals, but this difference was not statistically significant

High intake of selenium, beta-carotene, and vitamins A, C, and E reduces growth of Helicobacter pylori in the guinea pig

PURPOSE: Helicobacter pylori is a human gastroduodenal pathogen associated with type-B gastritis and gastric cancer. Low gastric tissue antioxidant levels are believed to increase the risk of developing gastric cancer. We investigated whether dietary antioxidant levels protect against infection and type-B gastritis in H. pylori-infected guinea pigs. METHODS: Dunkin-Hartley guinea pigs infected for 6 weeks with H. pylori were fed diets with various antioxidant levels. Stomach specimens were cultured, and gastritis was graded from 0 to 3. RESULTS: Supplementation with vitamins A, C, and E and with selenium yielded H. pylori recovery from 17% of challenged animals, compared with 43% of those fed a control diet. Gastritis was scored at 0.33 and 0.93, respectively. Supplementation with only vitamin C or astaxanthin had less effect on gastritis and recovery rate. In a second experiment, gastritis score in a group given vitamins A, C, E, and selenium and beta-carotene was 2.25 and in a control group, it was 2.57. The H. pylori recovery rate was 75 and 100%, respectively, with fewer colonies from animals given antioxidant supplementation (P < 0.05). CONCLUSIONS: A combination of antioxidants can protect against H. pylori infection in guinea pigs. In animal studies, antioxidant intake should be low to optimize development of H. pylori-associated disease. Furthermore we established that H. pylori causes severe gastritis in guinea pigs

Lectin histochemistry of the gastric mucosa in normal and Helicobacter pylori infected guinea-pigs

Helicobacter pylori attaches via lectins, carbohydrate binding proteins, to the carbohydrate residues of gastric mucins. Guinea-pigs are a suitable model for a H. pylori infection and thus the carbohydrate composition of normal and H. pylori infected gastric mucosa was investigated by lectin histochemistry. The stomach of all infected animals showed signs of an active chronic gastritis in their mucosa, whereas no inflammation was present in the control animals. The corpus-fundus regions of the controls showed heterogeneous WGA, SNA-I, UEA-I and HPA binding in almost all parts of the gastric glands. While these lectins labelled the superficial mucous cells and chief cells heterogeneously, the staining of the parietal cells was limited to WGA and PHA-L. Mucous neck cells reacted heterogeneously with UEA-I, HPA, WGA and PHA-L. In the antrum, the superficial mucous cells and glands were stained by WGA, UEA-I, HPA, SNA-I or PHA-L. WGA, UEA-I, SNA-I and HPA labelled the surface lining cells strongly. The mucoid glands reacted heterogeneously with WGA, UEA-I, HPA, SNA-I and PHA-L. In both regions, the H. pylori infected animals showed similar lectin binding pattern as the controls. No significant differences in the lectin binding pattern and thus in the carbohydrate composition between normal and H. pylori infected mucosa could be detected, hence H. pylori does not induce any changes in the glycosylation of the mucosa of the guinea-pig. This unaltered glycosylation is of particular relevance for the sialic acid binding lectin SNA-I as H. pylori uses sialic acid binding adhesin for its attachment to the mucosa. As sialic acid binding sites are already expressed in the normal mucosa H. pylori can immediately attach via its sialic acid binding adhesin to the mucosa making the guinea-pig particularly useful as a model organism

ESX-1 exploits type I IFN-signalling to promote a regulatory macrophage phenotype refractory to IFNγ-mediated autophagy and growth restriction of intracellular mycobacteria

Summary: The ability of macrophages to eradicate intracellular pathogens is normally greatly enhanced by IFNγ, a cytokine produced mainly after onset of adaptive immunity. However, adaptive immunity is unable to provide sterilizing immunity against mycobacteria, suggesting that mycobacteria have evolved virulence strategies to inhibit the bactericidal effect of IFNγ-signalling in macrophages. Still, the host-pathogen interactions and cellular mechanisms responsible for this feature have remained elusive. We demonstrate that the ESX-1 type VII secretion systems of Mycobacterium tuberculosis and Mycobacteriummarinum exploit type I IFN-signalling to promote an IL-12low/IL-10high regulatory macrophage phenotype characterized by secretion of IL-10, IL-27 and IL-6. This mechanism had no impact on intracellular growth in the absence of IFNγ but suppressed IFNγ-mediated autophagy and growth restriction, indicating that the regulatory phenotype extends to function. The IFNγ-refractory phenotype was partly mediated by IL-27-signalling, establishing functional relevance for this downstream cytokine. These findings identify a novel macrophage-modulating function for the ESX-1 secretion system that may contribute to suppress the efficacy of adaptive immunity and provide mechanistic insight into the antagonistic cross talk between type I IFNs and IFNγ in mycobacterial infection

Long-term Outcome of Antiretroviral Treatment in Patients With and Without Concomitant Tuberculosis Receiving Health Center-Based Care-Results From a Prospective Cohort Study

Background: In order to increase treatment coverage, antiretroviral treatment (ART) is provided through primary health care in low-income high-burden countries, where tuberculosis (TB) co-infection is common. We investigated the long-term outcome of health center-based ART, with regard to concomitant TB.Methods: ART-naïve adults were included in a prospective cohort at Ethiopian health centers and followed for up to 4 years after starting ART. All participants were investigated for active TB at inclusion. The primary study outcomes were the impact of concomitant TB on all-cause mortality, loss to follow-up (LTFU), and lack of virological suppression (VS). Kaplan-Meier survival estimates and Cox proportional hazards models with multivariate adjustments were used.Results: In total, 141/729 (19%) subjects had concomitant TB, 85% with bacteriological confirmation (median CD4 count TB, 169 cells/mm3; IQR, 99-265; non-TB, 194 cells/mm3; IQR, 122-275). During follow-up (median, 2.5 years), 60 (8%) died and 58 (8%) were LTFU. After ≥6 months of ART, 131/630 (21%) had lack of VS. Concomitant TB did not influence the rates of death, LTFU, or VS. Male gender and malnutrition were associated with higher risk of adverse outcomes. Regardless of TB co-infection status, even after 3 years of ART, two-thirds of participants had CD4 counts below 500 cells/mm3.Conclusions: Concomitant TB did not impact treatment outcomes in adults investigated for active TB before starting ART at Ethiopian health centers. However, one-third of patients had unsatisfactory long-term treatment outcomes and immunologic recovery was slow, illustrating the need for new interventions to optimize ART programs