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- Stark, Lisa
(författare)
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Staphylococcus aureus : aspects of pathogenesis and molecular epidemiology
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Staphylococcus aureus is a human commensal colonizing about 30 per cent of the population. Besides, it is a frequent cause of infections such as skin, wound and deep tissue infections and also more life-threatening conditions such as pneumonia, endocarditis and septicaemia. S. aureus may also cause different toxicoses. Moreover, this bacterium is one of the most common causes of nosocomial infections worldwide and an increase in antibiotic resistance, especially against methicillin, is seen. This underlines the importance to prevent and control outbreaks of S. aureus. The aims of this thesis were to increase the knowledge of S. aureus virulence and pathogenesis as well as to understand pattern of colonization and transmission.Various virulence factors operate together in the pathogenic process of S. aureus. The virulence of S. aureus was studied by the interaction with human umbilical vein endothelial cells (HUVEC) as a model. In paper I, we found that one bacterial isolate survived intracellularly and that 156 genes were differentially regulated in microarray analysis of HUVEC. The major part of these genes coded for proteins involved in innate immunity. In paper II, we wanted to explore possible differences in global gene expression patterns in HUVEC induced by invasive compared to colonizing isolates of S. aureus. We also used microarray to investigate possible differences in the presence of virulence genes between the two groups. The main finding was that virulent and commensal S. aureus did not differ in interaction with HUVEC and in the presence of virulence genes. All isolates survived intracellularly for days.Since no obvious differences in virulence between the two groups of isolates were found, we focused on epidemiology and transmission patterns. Colonization with S. aureus is an important risk factor for subsequent S. aureus infection. In paper III, we investigated S. aureus colonization and transmission among nursing home residents in three regions in the south of Sweden and used staphylococcal protein A (spa) typing as an epidemiological tool. A diverse distribution of different spa types was found and a majority of types were unique to one individual. Interestingly, we found a local accumulation of one spa type in one nursing home. Also common spa types were equally distributed in the different regions. We also noted that some individuals were colonized with two different spa types of S. aureus and in five of these cases there was one resistant and one non-resistant strain.The issue of multiclonal colonization and infection is highly important and clinical diagnostic laboratories do not routinely address this problem. Therefore, in paper IV a novel method to assess multiclonality of S. aureus was developed. It was based on denaturing gradient gel electrophoresis with the amplification of the spa gene. The method simultaneously separated eight different spa types. It also detected two spa types in an outbreak.In conclusion, we found no differences in virulence genes and in the interaction with HUVEC between commensal and invasive isolates. This indicates that any isolate of S. aureus might have a pathogenic potential. We also confirmed that some spa types are more successful colonizers with a potential to nosocomial spread. The method for detection of multiclonality of S. aureus is of importance in future epidemiological and clinical studies.
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- Jurstrand, Margaretha, 1947-
(författare)
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Detection of Chlamydia trachomatis and Mycoplasma genitalium by genetic and serological methods
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chlamydia trachomatis infections are associated with a spectrum of clinical diseases including urethritis, prostatitis and epididymitis among men and cervicitis and pelvic inflammatory disease (PID), with an increased risk of infertility and ectopic pregnancy (EP), among women. In the search for other pathogens causing urethritis, Mycoplasma genitalium was isolated from urethral specimens from two men with acute urethritis (1980). Mycoplasma bacteria are extremely difficult to isolate by culture, and clinical studies have been possible only after the advent of the first PCR-based detection method. M. genitalium has been found to be associated with lower genital tract infections in both men and women. Finding evidence for a connection between M. genitalium and upper genital tract infections in women is still of major importance. The aim in papers I and II was to develop a PCR method for genetic characterization of clinical C. trachomatis isolates by sequence analysis of the omp1 gene, and to study the distribution of genotypes within sexual networks and determine if genotyping would improve partner notification. The method was used to determine the genotypes of C. trachomatis in 237 positive urogenital and/or urine specimens from men and women attending the STDClinic in Örebro during one year. Sequence analysis of the omp1 gene revealed that the most prevalent genotypes corresponded to C. trachomatis serovar E (47%), followed by F (17%), and K (9%). There were 161 networks found and specimens were sequenced from at least two patients in 47 networks. In seven of these 47 networks there were discrepant genotypes. In the largest network comprising 26 individuals two different C. trachomatis genotypes were found, and one partner had urethritis due to a Mycoplasma genitalium infection but was C. trachomatis negative. The need for a new method for M. genitalium DNA detection was one reason for study III. An existing conventional PCR protocol for detection of M. genitalium DNA was further developed into a real-time PCR (RT-PCR) with hybridisation probes. In order to evaluate the RT-PCR assay with clinical material, specimens from 398 men and 301 women attending the STD Clinic in Örebro were analysed, using the RT-PCR assay, and also by the well established conventional PCR in Copenhagen. Using the conventional PCR method as “gold standard”, the sensitivity for the RT-PCR assay was 72.2% and 68.2% and the specificity was 99.7% and 98.6%, respectively, in urogenital specimens from men and women. The aim in paper IV was to adapt a Triton X-114 extracted Lipid-Associated Membrane Protein (LAMP) Enzyme Immuno Assays (EIA) method to detect antibodies against M. genitalium and to evaluate the association between M. genitalium and PID and EP, using sera sampled in Örebro during the 1980s, and also to compare the number of sera having M. genitalium antibodies against those having C. trachomatis antibodies, using a commercial anti- Chlamydia trachomatis EIA assay. No statistical significant association could be demonstrated between M. genitalium antibodies and PID or EP in our serum material. However, a slight trend toward association was found when focusing on younger individuals. Antibodies against C. trachomatis were found to be significantly associated with PID and EP.
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- Kälvegren, Hanna, 1978-
(författare)
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The Role of Chlamydia pneumoniae-induced Platelet Activation in Cardiovascular Disease : In vitro and In vivo studies
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The common risk factors for atherosclerosis, such as obesity, high cholesterol levels, sedentary lifestyle, diabetes and high alcohol intake, only explain approximately 50% of cardiovascular disease events. It is thereby important to identify new mechanisms that can stimulate the process of atherosclerosis. During the past decades, a wide range of investigations have demonstrated connections between infections by the respiratory bacterium Chlamydia pneumoniae and atherosclerosis. Earlier studies have focused on the interaction between C. pneumoniae and monocytes/macrophages, T-lymphocytes, smooth muscle cells and endothelial cells, which are present in the atherosclerotic plaque. However, another important player in atherosclerosis and which is also present in the plaques is the platelet. Activation of platelets can stimulate both initiation and progression of atherosclerosis and thrombosis, which is the ultimate endpoint of the disease. The aim of the present thesis was to investigate the capacity of C. pneumoniae to activate platelets and its role in atherosclerosis.The results show that C. pneumoniae at low concentrations binds to platelets and stimulates platelet aggregation, secretion, reactive oxygen species (ROS) production and oxidation of low-density lipoproteins (LDL), and that these effects are mediated by lipopolysaccharide (LPS). Activation of protein kinase C, nitric oxide synthase and 12-lipoxygenase (12-LOX) was required for platelet ROS production, whereas platelet aggregation was dependent on activation of GpIIb/IIIa. Pharmacological studies showed that the C. pneumoniae-induced platelet activation is prevented by inhibitors against 12-LOX, platelet activating factor (PAF) and the purinergic P2Y1 and P2Y12 receptors, but not against cyclooxygenase (COX). These findings were completely opposite to the effects of these inhibitors on collagen-stimulated platelets. We also present data from a clinical study indicating that percutaneous coronary intervention (PCI or balloon dilatation) leads to release of C. pneumoniae into the circulation, which causes platelet activation and LDL oxidation.In conclusion, these data support a role for C. pneumoniae-induced platelet activation in the process of atherosclerosis. Stimulation of platelets by C. pneumoniae leads to release of growth factors and cytokines, oxidation of LDL and platelet aggregation, which are processes that can stimulate both atherosclerosis and thrombosis. Development of novel drugs that prevent C. pneumoniae-platelet interaction by inhibiting 12-LOX and/or PAF, may be important in the future treatment of cardiovascular disease.
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