Pathogenicity of microorganisms

Microbe-Macroorganism Interactions

The nature of the impact of microorganisms on the human body can be strictly negative as well as positive. Biology distinguishes several basic forms of such coexistence:

• Parasitism. This is a form of interaction in which the microbe exists exclusively at the expense of the host macroorganism's resources, causing direct biological and functional damage.
• Symbiosis and commensalism. Forms of coexistence that are either beneficial to both participants in the process or benefit one of them while causing no harm at all to the other.

Classification by Degree of Pathogenicity

Based on the types of relationships between the microbe and the human, all microorganisms are traditionally divided into three major groups:

1. Pathogenic microbes (the term originates from the Greek word patos — disease). These are true disease-causing agents capable of predictably causing specific infectious diseases.
2. Opportunistic microorganisms. This group is capable of causing disease only in the presence of strictly defined conditions (most often triggered by a marked decrease in host immunity).
3. Saprophytes (from the Greek roots sapros — rotten and phyton — plant). These are entirely non-pathogenic (non-disease-causing) microbes that do not cause diseases in humans in principle.

Epidemiological Significance of Infections

Despite the grandiose progress of modern medicine, infectious diseases confidently continue to rank first in prevalence. Statistics show that about 70% of all registered patients are infectious disease patients (effectively every two out of three seeking medical care).

Consequently, physicians face the following crucial tasks:

• The ability to conduct competent differential diagnosis (especially when dealing with the risk of particularly dangerous infections).
• Combating nosocomial (hospital-acquired) infections. Even in non-infectious departments, doctors constantly encounter opportunistic microbes. This dictates the necessity of solid knowledge regarding aseptic rules, antiseptic standards, and therapy principles.

Impact on Homeostasis and Immunity

Iatrogenic factors (surgical interventions, medication intake) and somatic diseases inevitably disrupt the balance of the human normal flora. Any disturbance in the microbiota composition immediately entails a change in the patient's general immune status. The physician must be able to thoroughly analyze these conditions and correct them during the treatment of the underlying disease.

Additionally, there is a colossal surge in various immunopathologies among the population. These include:

• Allergic diseases.
• Autoimmune processes.
• Immunodeficiency states.

All of this requires clinicians and occupational health specialists to possess deep competencies in the field of clinical immunology.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of formation and maintenance of normal human microbiota (normal flora)
• Principles of differential diagnosis of particularly dangerous infectious diseases
• Rules of asepsis and antisepsis for the prevention of nosocomial (hospital-acquired) infections
• The role of immune status in the development of opportunistic infections
• Pathogenesis of autoimmune and allergic processes against the background of microflora imbalance

Other topics in the section "Introduction to microbiology and immunology"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.