Detection and Diagnosis of Infectious Diseases

Posted by beauty33 on May 27th, 2019

Introduction

The development of an infectious disease in an individual involves complex interactions between the microbe and the host. The key events during infection include entry of the microbe, invasion and colonization of host tissues, evasion of host immunity, and tissue injury or functional impairment. Microbes produce disease by directly killing the host cells they infect, or by liberating toxins that can cause tissue damage and functional derangements in neighboring or distant cells and tissues that are not infected.

The interaction of the immune system with infectious organisms is a dynamic interplay of host mechanisms aimed at eliminating infections and microbial strategies designed to permit survival in the face of powerful defenses. Different types of infectious agents stimulate distinct types of immune responses and have evolved unique mechanisms for evading immunity. In some infections, the immune response is the cause of tissue injury and disease.

Here we will consider the main features of immunity to four major categories of pathogenic microorganisms: extracellular and intracellular bacteria, fungi, viruses, and protozoan as well as multicellular parasites.

Detection and diagnosis

Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi. Some infectious diseases can be passed from person to person. Some are transmitted by bites of insects or animals. And others are acquired by ingesting contaminated food or water or being exposed to organisms in the environment. Infectious diseases resulted in about 9 million deaths every year. The symptoms of infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue, loss of appetite, weight loss, fevers, night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes, coughing, or a runny nose. Source organism diagnosis and detection of infectious disease is the key to its prevention and treatment.

Diagnosis of infectious disease sometimes involves identifying an infectious agent either directly or indirectly. Microscopy and microbial culture is probably the most direct method and the golden standard to identify the cause organism of an infectious disease, but it usually needs days or weeks before the results available. Furthermore, not all pathogens can be cultured, that make indirectly method very useful in diagnostic and detection of infectious disease.

Both nucleic acid and proteins as well as small molecular chemicals can be used to detect pathogens. Nucleic acid as genetic material is ubiquity within all kinds of pathogens that make it an ideal marker of pathogen detection and identification. Proteins as the structure and functional material of microbial is also important for diagnostic and detection. Cell wall and pili of bacterial, capsid of the virus, spores of the fungus, surface antigen of parasites and even the metabolic product of these pathogen are all biomarkers for diagnosis and detection of infectious disease (Figure 1).

Figure 1. Pathogenic factors of infectious diseases.

Divers biotechnology or immunoassay such as PCR (detect nucleic acid), ELISA (detect pathogenic antigen or antibody) are widely applied in this area. Many of them are commercialized products. Creative diagnostic offers a wide variety of enzyme-linked immunosorbent assay (ELISA) kits, Rapid diagnostic kits as well as the related antigens and antibodies for the diagnostic and detection of infectious disease.

Article source: https://www.creative-diagnostics.com/Infection-Immunity.htm

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