Medical Microbiology Lecture 1

Human Microbiome in Health and Disease

• Microbial flora is dynamic, reflecting ongoing changes in nutrition, hormonal levels, and health conditions.
• The human microbiome comprises a unique set of microorganisms for each individual, with the gut microbiome being the most significant.
• The Human Microbiome Project: a 5-year study analyzing microbial populations in healthy adults via samples from various body sites (nose, mouth, skin, gut, vagina).

Microbial Identification

• Microbe identification leveraged sequencing of the 16S ribosomal RNA gene, a genetic marker unique to each species, composed of RNA and proteins.
• The 18S gene is used for identifying eukaryotes.
• Operational Taxonomic Unit (OTU) classifies closely related microbial groups.

Core Microbiome and Taxonomy

• Core microbiome: consists of species present in 95% or more of individuals at specific body sites, with high taxonomic diversity yet consistent functional properties.
• Functional redundancy: multiple species can fill similar ecological roles, ensuring ecosystem resilience.
• The microbiome offers metabolic functions, enhances innate immunity, and protects against harmful pathogens.

Normal Flora and Its Influences

• Normal flora consists of core and secondary microbiota formed through symbiosis and interspecies competition.
• Composition is affected by hygiene, diet, water source, medication (notably antibiotics), and environmental toxins.

Nutritional Impact on Microbiome

• Nutrition significantly influences the interplay between humans and their microbiome.
• Gut bacteria metabolize complex carbohydrates into short-chain fatty acids, which are crucial for cellular energy and inhibiting harmful bacteria.
• Specific bacteria (Bacteroidetes and Firmicutes) efficiently break down complex and host-derived carbohydrates.
• Increased ratios of these bacteria may enhance metabolic efficiency and impact health outcomes, including malnutrition and obesity.

Microbiome's Role in Disease

• Emerging research suggests that a community of organisms, rather than just individual species, contributes to disease, affecting conditions such as inflammatory bowel disease, obesity, type 2 diabetes, and celiac disease.
• The concept of infectious diseases is being redefined by the understanding of microbiome interactions.

Dysbiosis and Clinical Implications

• Dysbiosis indicates a disruption in normal microbial communities, leading to disease by either depleting beneficial organisms or promoting harmful ones.
• Recognizing dysbiosis can lead to advanced diagnostics and innovative therapies, exemplified by Clostridium difficile infections resulting from normal flora depletion due to antibiotics.
• The consequences of microbiome alterations contribute to various diseases, emphasizing the importance of maintaining microbial balance for health.