Gastrointestinal infections can be caused by bacteria, viruses and parasites and are among the most frequent infectious diseases. They manifest as gastritis, diarrhoea, vomiting or unspecific symptoms which occur within only few hours after uptake of the pathogen with some bacterial or viral infections and may, in rare cases, lead to chronic sequelae. Infections with parasitic pathogens, however, usually take a chronic course.
Viral infections are often self-limiting, which is why it is sufficient to treat the symptoms, and laboratory diagnostic tests are usually not performed. Bacteria such as Yersinia and Campylobacter, however, may cause immunologically mediated secondary diseases, e.g. reactive arthritis. Here, serological tests may support the diagnosis. Infections with Helicobacter pylori may cause chronic active gastritis and complications such as gastroduodenal ulcer disease, stomach carcinoma or lymphoma. Antibody detection is recommended in suspected cases of non-acute or chronic infection. Parasitic pathogens such as Schistosoma and Strongyloides stercoralis can also cause gastrointestinal symptoms with chronic courses. Direct and indirect methods are applied for diagnostics. In general, specific antibody detection is suitable to support the diagnosis in suspected cases of chronic courses or secondary diseases, but not for diagnostics in acute cases.
Infections of the respiratory tract are mainly caused by viruses (e.g. influenza viruses, adenoviruses, RSV), but also bacteria (e.g. Legionella, Bordetella pertussis, Mycoplasma pneumoniae, Chlamydia pneumoniae). Both the upper (e.g. nasal mucosa, paranasal sinuses) and the lower respiratory tracts (airways and bronchia) can be affected. The pathogens are mainly transmitted by droplet infection. Symptoms of respiratory infections include fever, cough, headaches and pain, pharyngitis, sinusitis, bronchitis or pneumonia.
Since many respiratory pathogens cause similar symptoms, the diseases cannot usually be diagnosed based on the clinical image alone. Consequently, laboratory diagnostics are particular valuable. Direct pathogen detection (e.g. PCR) is in most cases the method of choice for the detection of acute respiratory infections.
Since antibodies are only formed some days or weeks following infection and the prevalence increases with age, an infection can often only be diagnosed retrospectively by investigation of a serum pair and detection of an IgG titer increase. Serological tests can also contribute to epidemiological monitoring.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV) belongs to the family of coronaviruses and, like SARS-CoV, is classified in the genus Betacoronavirus. The new virus has its origin in China. At the end of 2019, it caused a first infection wave that has spread rapidly over the country and worldwide. Just a few days after the first report about patients with pneumonia of unclear origin, SARS-CoV-2 was identified as the causative pathogen.
SARS-CoV-2 is mainly transmitted via aerosols during coughing or sneezing or at close contact with an infected person. The incubation period is three to seven, maximum 14 days. In February 2020, the disease caused by SARS-CoV-2 was named COVID-19 by the WHO. The symptoms of SARS-CoV-19 infection are fever, coughing, breathing difficulties and fatigue. Some patients, especially older and chronically ill persons, develop a severe acute respiratory distress syndrome with sometimes fatal outcome.
Suitable methods for diagnosis of SARS-CoV-2 infections are direct detection of the virus by reverse transcriptase polymerase chain reaction (RT-PCR) primarily in sample material from the upper (nasopharyngeal or oropharyngeal swab) or lower (bronchoalveolar lavage fluid, tracheal secretion, sputum, etc.) respiratory tract and the detection of antibodies against SARS-CoV-2 in blood. The latter allows pathogen detection even in subclinical or asymptomatic cases within a few days after virus contact up to approx. 14 days after the onset of symptoms (Liu et al., 2020).
The detection of specific antibodies against SARS-CoV-2 in blood expands the diagnostic window beyond the first one to two weeks. Antibody detection helps to identify persons who present a persisting (no longer acute) or past infection with SARS-CoV-2. Moreover, serology plays an important role in outbreak monitoring and tracking of infection chains, as well as in answering clinical, epidemiological and virological questions related to SARS-CoV-2 and COVID-19.
EUROIMMUN offers a comprehensive portfolio of products for COVID-19 diagnostics, ranging from PCR for diagnostics of acute cases to ELISAs for detection of antibodies of different immunoglobulin classes and against different SARS-CoV-2 antigens.
Sexually transmitted infections (STIs) can be caused by bacteria (e.g. Treponema pallidum, Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma), viruses (e.g. HSV) or parasites (Trichomonas vaginalis), which are transmitted from person to person by vaginal, anal or oral sex. The course, symptoms and consequences of STIs can differ significantly depending on the causative pathogen. In many cases, the infection is asymptomatic, so that it remains undiscovered for a long time and is only diagnosed when it has become chronic. Infections with these pathogens often cause inflammation of the urogenital tract, which may ascend and lead to e.g. infertility.
In addition to the consequences for the patient, infections with most of the mentioned pathogens can also lead to intrauterine foetal loss, preterm birth or damage to the unborn child. Moreover, many pathogens can be transmitted to the newborn during birth, causing severe postnatal infections.
The commonly used detection methods for STI are direct methods, in which the pathogen is detected by PCR or culture, and indirect methods, i.e. detection of pathogen-specific antibodies. Since detection by culturing is especially time-consuming and difficult for Chlamydia, Mycoplasma, Ureaplasma and Treponema, other detection methods, e.g. PCR-based and/or serological procedures, are generally recommended or required for these pathogens.