12 Mar Unraveling Human Pathogens: The Precision Tool for Detection
Have you ever pondered how invisible microbes can trigger illnesses around us? Did you know millions fall ill, even fatally, due to human pathogens each year? These unseen threats are ever – present, silently invading our bodies and causing diseases ranging from mild colds to severe ones like AIDS and tuberculosis. Accurate detection of these pathogens is crucial for our health protection.
What are Human Pathogens?
Human pathogens are disease – causing microbes and parasites. An infection occurs when pathogens invade tissues, multiply, and trigger a reaction from the host’s tissues to the pathogens and their toxins. Mammalian hosts initially respond to infections with an innate response, often involving inflammation, followed by an adaptive response. These organisms colonize host tissues, prompting the host immune system to produce specific antibodies against them.
Detailed Classification of Human Infectious Disease Pathogens
- Subcellular Infectious Entities
Prions (proteinaceous infectious particles). The evidence indicates that prions are protein molecules that cause degenerative central nervous system (CNS) diseases such as Creutzfeldt-Jakob disease, kuru, scrapie in sheep, and bovine spongiform encephalopathy (BSE).
Viruses. Ultramicroscopic, obligate intracellular parasites that:
— contain only one type of nucleic acid, either DNA or RNA,
— possess no enzymatic energy-producing system and no protein-synthesizing apparatus
— force infected host cells to synthesize virus particles.
- Bacteria
Classic bacteria. These organisms reproduce asexually by binary transverse fission. They do not possess the nucleus typical of eucarya. The cell walls of these organisms are rigid (with some exceptions, e.g., the mycoplasma).
Chlamydiae. These organisms are obligate intracellular parasites that are able to reproduce in certain human cells only and are found in two stages: the infectious, nonreproductive particles called elementary bodies (0.3μm) and the noninfectious, intracytoplasmic, reproductive forms known as initial (or reticulate) bodies (1μm).
Rickettsiae. These organisms are obligate intracellular parasites, rod-shaped to coccoid, that reproduce by binary transverse fission. The diameter of the individual cell is from 0.3-1μm.
Mycoplasmas. Mycoplasmas are bacteria without rigid cell walls. They are found in a wide variety of forms, the most common being the coccoid cell (0.3-0.8 lm). Threadlike forms also occur in various lengths.
- Fungi and Protozoa
Fungi. Fungi (Mycophyta) are nonmotile eukaryotes with rigid cell walls and a classic cell nucleus. They contain no photosynthetic pigments and are carbon heterotrophic, that is, they utilize various organic nutrient substrates (in contrast to carbon autotrophic plants). Of more than 50 000 fungal species, only about 300 are known to be human pathogens. Most fungal infections occur as a result of weakened host immune defenses.
Protozoa. Protozoa are microorganisms in various sizes and forms that may be free-living or parasitic. They possess a nucleus containing chromosomes and organelles such as mitochondria (lacking in some cases), an endoplasmic reticulum, pseudopods, flagella, cilia, kinetoplasts, etc. Many parasitic protozoa are transmitted by arthropods, whereby multiplication and transformation into the infectious stage take place in the vector.
- Animals
Helminths. Parasitic worms belong to the animal kingdom. These are metazoan organisms with highly differentiated structures. Medically significant groups include the trematodes (flukes or flatworms), cestodes (tapeworms), and nematodes (roundworms).
Arthropods. These animals are characterized by an external chitin skeleton, segmented bodies, jointed legs, special mouthparts, and other specific features. Their role as direct causative agents of diseases is a minor one (mites, for instance, cause scabies) as compared to their role as vectors transmitting viruses, bacteria, protozoa, and helminths.
Now we’ve unveiled the true face of human pathogens, ranging from viruses and bacteria to fungi and parasites. They are omnipresent, threatening our health. So, how can we swiftly and accurately detect them? Picture yourself as a detective. Against these invisible foes, you need a sharp “microscope” to identify specific pathogens in complex samples.
Detection of Human Pathogens: ELISA
ELISA (Enzyme – Linked Immunosorbent Assay) is a widely used detection tool in biomedical research and clinical diagnosis for various human pathogens. It can provide clear answers within hours: whether the target pathogen exists and its quantity. This is a lifeline for doctors and scientists.
ELISA combines the specificity of antigen – antibody reactions with the high efficiency of enzyme catalysis. Enzymes are covalently linked to antibodies or anti – antibodies without altering their immunological properties or enzymatic activity. The enzyme – labeled antibodies specifically bind to antigens or antibodies on a solid – phase carrier (like a 96 – well plate). After adding the substrate solution, it undergoes a colorimetric reaction catalyzed by the enzyme, with the color intensity proportional to the amount of the target antibody or antigen in the sample. The absorbance (OD value) is measured using a microplate reader for qualitative or quantitative analysis of the target substance.
ELISA types, based on different principles and procedures, include:
- Direct ELISA: Antigens are directly coated on the microplate, followed by the addition of enzyme – labeled antibodies for binding. After washing, the substrate is added for a colorimetric reaction to detect antigen presence. It’s simple but less sensitive.
- Indirect ELISA: Antigens are coated on the microplate, then unmarked primary antibodies (specific to the antigen) are added. After washing, enzyme – labeled secondary antibodies (against the primary antibodies) are added. Finally, the substrate is used for a colorimetric reaction to detect the antigen. It offers high sensitivity but more steps.
- Sandwich ELISA: Suitable for large – molecule antigens, specific antibodies are fixed on the microplate. The test antigen is added, followed by enzyme – labeled antibodies to form a “sandwich”. After adding the enzyme substrate, the antigen content is measured. It provides high specificity and sensitivity.
- Competitive ELISA: Used for small – molecule antigen detection. Known antigens or antibodies are coated on the microplate, and the test sample along with enzyme – labeled antigens or antibodies are added, competing to bind with the coated material. The colorimetric reaction intensity infers the antigen or antibody amount in the sample.
Creative Diagnostics offers a broad range of infectious disease ELISA kits for the detection of human IgG, IgA and IgM antibodies to bacterial, viral, and parasite antigens. These ELISA kits provide high sensitivity and specificity, simple and robust methods, ready-to-use reagents, and reasonable assay time. Besides the controls in the test kit, ready – to – use positive controls are provided separately to check test validity, determine laboratory internal error limits, and document method batch – to – batch consistency.
Conclusion
Human pathogens, from microscopic viruses and bacteria to macroscopic fungi and parasites, are a diverse group of organisms that can cause a wide range of diseases. They invade our bodies, evade our immune systems, and establish infections that can be difficult to treat. In the realm of pathogens, ELISA detection technology is undeniably our superhero. It is not only precise and efficient but also user-friendly, providing an essential diagnostic tool for doctors and scientists.
More information:
The information on MedicalResearch.com is provided for educational purposes only, and is in no way intended to diagnose, cure, or treat any medical or other condition.
Some links are sponsored. Products and services are not endorsed.
Always seek the advice of your physician or other qualified health and ask your doctor any questions you may have regarding a medical condition. In addition to all other limitations and disclaimers in this agreement, service provider and its third party providers disclaim any liability or loss in connection with the content provided on this website.
Last Updated on March 12, 2025 by Marie Benz MD FAAD