Introduction to Medical Microbiology

Introduction to Medical Microbiology

• Microbiology is the study of microbes, including viruses, bacteria, fungi, and parasites
• Anton van Leeuwenhoek's development of microscopes led to the discovery of "animalcules."
• Otto Müller and Linnaeus classified these microbes
• Henle proposed criteria for proving microbes cause disease
• Koch and Pasteur confirmed microbes are responsible for specific diseases.
• Ehrlich, Fleming, and Waksman discovered first antibacterial agents.
• Enders cultivated viruses in cell cultures, enabling widespread vaccine production.
• Microbiology is undergoing transformation due to advances in genome analysis, especially the Human Genome Project.

Viruses

• Viruses are the smallest infectious agents, ranging from 18-600 nanometers
• They contain either DNA or RNA, but not both.
• Viruses require host cells for replication.
• Infection can result in rapid cell destruction or a long-term, latent state.
• Viruses cause a wide range of diseases from the common cold to severe conditions like AIDS and Ebola.
• Over 650 types of viruses that affect humans and animals have been identified.

Bacteria

• Bacteria are prokaryotic, unicellular organisms.
• They lack a nuclear membrane, mitochondria, and other organelles.
• Distinguished by cell wall structure: Gram-positive (thick peptidoglycan) and Gram-negative (thin peptidoglycan).
• Bacteria found in the human body, air, water, and food, some potentially causing disease.
• Diseases arise from toxin production or invasion of tissues.
• Many types of bacteria can cause disease, as well as a variety of manifestations of disease symptoms

Fungi

• Fungi are eukaryotic organisms.
• They have a well-defined nucleus, mitochondria, Golgi bodies, and an endoplasmic reticulum.
• Fungi exist in unicellular (yeast) or filamentous (mold) forms.
• Some fungi are dimorphic (changing forms)

Parasites

• Parasites are complex eukaryotic organisms, unicellular or multicellular.
• Their size ranges from tiny protozoa to larger organisms like tapeworms.
• Parasites can have complex life cycles, involving multiple hosts.
• They cause a wide range of diseases and health complications.

Microbial Disease

• Microbes are important for understanding diseases.
• Certain microorganisms are associated with very specific diseases, such as tetanus caused by Clostridium tetani.
• Many organisms cause multiple diseases or several organisms cause the same disease.
• Infections are classified as exogenous or endogenous.
• Infectious disease outcome depends on the microbe's virulence, the site of exposure, and host response.

Immunology

• The human immune system protects from infection.
• It responds to microbes and their invaders.
• Both innate and adaptive immunity are important in protecting against disease.
• The balance between the host and invader determine the outcome.

Diagnostic Microbiology

• Laboratory tests are crucial for diagnosis and management of infections.
• Collected samples should be representative for accurate testing.
• Contamination during collection can produce inaccurate results
• Antimicrobial susceptibility testing is important but needs careful selection, and results are influenced by factors outside the lab.

Summary

• Microbiology is a dynamic field, with constant discoveries about microbes and their role in health and disease.

Human Microbiome in Health and Disease

• The human body is colonized by a complex community of microbes (microbiome) from birth.
• The microbiome plays a role in metabolic and immunologic functions in the body.
• The Human Microbiome Project helped reveal the complexity.
• The "core microbiome" is shared across many individuals.
• Alterations in microbiome, termed dysbiosis, can cause diseases.
• Microbiome shifts in the body's different areas can indicate disease risks.
• Probiotics are mixtures of bacteria that are believed to provide benefits to the host.