BMV202.Lecture 1_.students_ (4).pptx

BMV202 Medical Microbiology Dr S. Govender (Term 3) Moodle Enrolment key: BMV202.2024 Attendance Register Practical Manual Select Practical Groups (Moodle) Tutorial Quiz after every lecture (Moodle) 2  Chapter 33 The Microbe- Chapter 33...

BMV202 Medical Microbiology Dr S. Govender (Term 3) Moodle Enrolment key: BMV202.2024 Attendance Register Practical Manual Select Practical Groups (Moodle) Tutorial Quiz after every lecture (Moodle) 2  Chapter 33 The Microbe- Chapter 33 Human The Microbe-Human Ecosystem Ecosystem Prescott’s Microbiology Twelfth edition Joanne Willey, Kathleen Sandman, Dorothy Wood © 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC. 4  MICROBE – HUMAN ECOSYSTEM  Humans: important ecosystem for microorganisms  Average adult somatic cells = microbial cells on the body  Microbiome, an organ?  Normal microbial flora/ microbiota: microbes normally associated with the human body 6  Microbiome = refers to all the microorganisms and microbial genomes that constitute a host’s normal microbiota  Holobionts: hosts and microbes live together and evolve together, form a single functional unit  Metabolome: all the small molecules produced by a cell (cytoplasmic & secreted molecules)  Metagenomic & immunology studies: most human- microbiota interactions are mutualistic, commensalistic  Microbial niche variations: age, gender, diet, nutrition and developmental stage of the human host  Microbiota: symbionts, part of host’s first line of defense against harmful infectious agents  Ectosymbiotic & endosymbiotic interactions between host & microbiota Development of a Stable Microbiome Microbiota community is not static. Begins developing at birth and changes as we age. A stable community of microbes adopted by age 3. It is important to develop a diverse microbiome. Access the text alternative for slide images. 8 Many factors contribute to the development of a stable microbiome (FIG 33.1) Diverse microbial community is linked to better health Complex interaction of many factors that determine microbial diversity (photo) Michel74100/iStock/Getty Images. (Text) Source: Man, Wing Ho, Piters, Wouter A. A. de Steenhuijsen and Bogaert, Debby. “The microbiota of the respiratory tract: gatekeeper to respiratory health,” Nature Reviews, March 20, 2017. 9 Early Colonization Newborn colonization important. Vaginal birth provides exposure to microbes from the mother’s birth canal Cesarean delivery: microbe exposure from initial caretakers 10  Bifidobacteria: > 90% of total intestinal bacteria in breast-fed infants, Enterobacteriaceae & Enterococci (smaller proportions)  Human milk: selective medium for non- pathogenic bacteria  Use novel strategies for sugar import  Transport polymeric sugars found in human breast milk directly across their plasma membrane.  Fermentation of these sugars provides the infant with calories and lowers the gut pH, limiting growth of pathogens. 1 2  Enzymes for catabolism of starch, pullulan, & amylopectin  Starting cow’s milk or solid food (mostly polysaccharide): loss of Bifidobacteria predominance & Enterobacteriaceae, enterococci, bacteriodes, lactobacilli & clostridia increase in number. Adult Human Microbiota Relatively stable over time. Only change due to physical or lifestyle changes. Variable from person to person and at different sites within a person. Bacteria common to human skin, the intestinal tract, and the other mucosal surfaces include six major phyla: Actinobacteriota Bacteroidota Firmicutes Fusobacteriota Proteobacteria Verrucomicrobiota Some archaea, fungi, and viruses are also present. 13 Innate & Environmental factors that impact microbial diversity & human immunity (Table 33.1) 14  Microbiota Vary by Body Site Internal organs and tissues (that is, brain, blood, cerebrospinal fluid, muscles) are normally free of microorganisms. Surface tissues (i.e, skin and mucous membranes) are constantly in contact with the environment and are colonized by various microbes. 15  Skin  Commensal microorganisms living on/ in the skin: resident or transient  Skin is a mechanically strong barrier to microbial invasion.  Few microbes can penetrate the skin because its outer layer consists of thick, closely packed cells = keratinocytes.  Continuous shedding of the outer epithelial cells: removal of many of the microbes that adhere to the skin surface. 16 Skin Environment: Slightly acidic pH. High concentration of NaCl. Some areas lack moisture. Some bathed in oily lubricant sebum and antimicrobial peptides. Three environmental niches:  Dry areas (forearm, buttocks, hands): greatest bacterial diversity Actinobacteria, Bacteriodetes, Firmicutes, Proteobacteria  Moist areas (umbilicus, underarm, inguinal & gluteal creases, inside elbow, less diversity – Actinobacteria (Staphylococcus & Corynebacterium spp.), Firmicutes  Oily sebaceous sites (forehead, behind the ear & back): Actinobacteria (Cutibacterium spp.), lowest bacterial diversity. 17 Staphylococcus epidermidis  Colonize the skin and generally non-pathogenic.  Key component of healthy skin.  Modulate keratinocyte gene expression stimulating antimicrobial peptide release, proteases.  Secreting products of fermentation: short chain fatty acids.  Binding to the pattern recognition receptor TLR-2.  Bacterial interference–inhibits growth of pathogens. Staphylococcus epidermidis Is an Essential Component of Healthy Skin 18  Skin bacteria: superficial cells, colonizing dead cells, or closely associated with the oil & sweat glands  Secretions from sweat glands provide water, amino acids, urea, electrolytes & specific fatty acids: nutrients for microorganisms  Staphylococcus epidermidis, Corynebacteria (5% of skin microbiota)  Yeasts: Pitysporum ovale & P. orbiculare, scalp  Acne: hormonal activity stimulates overproduction of sebum from oil glands  Cutibacterium acnes: hydrolyses sebum to free fatty acids, promote inflammation, comedones, blackheads, pimples  Tetracycline, Retin A & Accutane  Oil glands secrete lipids: G+ve bacteria, form unsaturated fatty acids by partial degradation  Unsaturated fatty acids: antimicrobial against G–ve bacteria & some fungi  Some fatty acids: volatile, odour, deodrants contain antimicrobials that act against G+ve bacteria