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- Ringdahl, Ulrika
(författare)
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Streptococcus pyogenes and its interactions with the human host
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We have found that a set of group A streptococcal strains, primarily associated with skin infections, express surface-associated M proteins that bind plasminogen and plasmin with high affinity. The binding is mediated by a common 13 amino acid internal repeated sequence located in the NH2-terminal surface-exposed portion of these M proteins. It could be demonstrated that plasminogen, absorbed by the bacteria when grown in plasma, could be activated by exogenous and endogenous streptokinase, a potent plasminogen activating protein that is secreted by group A streptococci, thereby providing the bacteria with a surface-associated enzyme that could act on fibrin films or other tissue barriers in the infected host. While only a subset of these bacteria bind plasminogen, almost all group A streptococcal strains bind fibrinogen. It is known that this property is coupled to members of the M protein family. We first identified the fibrinogen-binding region in the type M1 and M5 proteins and then generated an isogenic strain expressing an M5 protein lacking the fibrinogen-binding region. This strain had lost the ability to resist phagocytosis in human blood, a feature that is characteristic for group A streptococci. Furthermore, streptococcal mutants expressing versions of the fibrinogen non-binding M4 protein grafted with the fibrinogen-binding regions from M1 or M5 were generated. The manipulation converted these strains from phagocytosis sensitive to phagocytosis resistant, demonstrating the importance of the fibrinogen-binding capacity for bacterial survival. The ability to bind fibrinogen also gives the bacteria the ability to interact with platelets. Fibrinogen serves as a link between the bacteria and the platelet and the subsequent binding of antibodies directed against the bacteria to the FcgRIIa receptor can induce platelet activation and aggregation, a property that may contribute to acute complications in severe group A streptococcal infection.
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| 2. |
- Tegern, Matthias, 1982-
(författare)
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Musculoskeletal disorders in Swedish military aircrew : screening and clinical examination of the cervico-thoracic region
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Musculoskeletal disorders (MSD) are a common and growing occupational problem in military aircrew. Intervention studies attempting to reduce such issues have only showed limited preventive effects. Furthermore, in-depth knowledge of the clinical presentation of aircrew members with painful episodes is lacking. This thesis was conducted to add evidence to the ongoing work of the Swedish Armed Forces (SAF) for the prevention of MSD. The overall aim of this thesis was to estimate the occurrence of MSD in general and specifically cervico-thoracic pain and its associated factors among SAF aircrew and to evaluate clinically relevant tests, prior to the adaptation of a musculoskeletal screening protocol (MSP) for use in the SAF medical health care system. All participants included in the four studies of this thesis were employed in the SAF. Two cross-sectional studies (Study I; n=351, Study III; n=73) aimed to establish the occurrence of MSD in aircrew compared with army deployed soldiers (Study I) and between fighter pilots, helicopter pilots and rear crew (Study I), as well as identify associated factors of cervical, thoracic and shoulder region pain (Study I) and cervico-thoracic pain (Study III). Study II had a test-retest design and aimed to examine inter-rater (n=37) and test-retest (n=45) reliability of movement control tests. In study III, test performance was compared between fighter pilots, helicopter pilots and rear crew. Study IV had a cross-sectional (n=18) and a prospective observational cohort (n=47) design and aimed to explore physical symptoms and functional limitations in aircrew with cervico-thoracic pain, establish 12-month cumulative incidence and to identify risk factors for cervico-thoracic pain.The main findings of this thesis were that when compared to deployed soldiers, military aircrew reported higher prevalence of MSD in the cervical, thoracic, shoulder, and lumbar regions (80% reported at least one painful area during the previous year). Working as aircrew, and a lower rating of one’s physical health, were significantly associated with pain in the cervical, thoracic and shoulder regions (Study I). Two physical therapists could reliably rate movement patterns for the majority of movement control tests in the affected areas. Lower reliability was however seen for test-retest conditions (Study II). Movement control and measures of cervical range of motion (ROM), but not cervical strength and endurance, were associated with cervico-thoracic pain among military aircrew. Specifically, less control of both neck and lumbar flexion movements, and lesser cervical flexion ROM were associated with cervico-thoracic pain. Differences were found between fighter pilots, helicopter pilots and rear crew for lumbar flexion movement control and cervical lateral flexion ROM (Study III). Physical symptoms and functional impairments of aircrew with high (pain) intensity, flight-elicited and work-affecting cervico-thoracic pain showed an individual presentation. Previous pain episodes, lesser cervical flexion ROM, and lesser cervical flexor muscle endurance were identified as risk factors for future cervico-thoracic pain, which had a 12-month cumulative incidence of 23% (Study IV).Findings from this thesis strongly indicate that MSD in SAF aircrew is an occupational problem that need to be solved. The cervico-thoracic region was especially common in SAF aircrew. Movement control can reliably be assessed, but with less stability for repeated measures. While pain history and physical performance can to some degree be used to identify aircrew at risk for further cervico-thoracic pain, the clinical presentation of their physical symptoms showed individual presentation. The effects of implementing the MSP in the SAF as a primary and secondary preventive intervention, as well as rehabilitative strategies, need be systematically evaluated.
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