Microbiome in Health and Disease Flashcards
Microbiome
-a community of microorganisms inhabiting a particular niche
Dysbiosis: abnormal composition of a microbiome
gnotobiotic
-growth in a germ-free environment
commensalism
-an interaction between two species in which one benefits, one is unaffected
mutualism
an interaction between two species in which both species benefit
parasitism
-an interaction between two species in which one benefits, one is harmed
immune homeostasis
- balance between a hyper-reactive and unresponsive immune system
- Loss of homeostasis may lead to chronic hyper-responsiveness to microbes and microbial antigens, such as in Crohn’s disease
Pathogen exclusion
- commensals compete with pathogens, thus limiting infectivity
- nutrient/receptor competition
Ex: Disruption of gut microbiome by antibiotics increases risk of C. diff infection
Structural functions of commensals
- barrier fortification (epithelial tight junctions)
- immune system development (IgA induction)
Metabolic function of GI microbiome
- provides 10% of our calories
- synthesize vitamins (B3, B5, B6, B12, K, Biotin, Folate)
- sequester metals
- ferment non-digestible polysaccharides and mucus
-On the other hand: possibility that higher number of Firmicutes (G+) may lead to obesity
Name/describe the three “Domains” (three primary lines of descent)
- Bacteria: unicellular organisms
- Eucarya: nucleated cells of unicellular and multicellular organisms (includes plants, animals, and microbes)
- Archaea: unicellular organisms unrelated to bacteria. Includes extremophiles capable of life at high temperature (over 100 deg C) and high salinity
List two common pathogens in the phyla: Actinobacteria
- M. tuberculosis
- Corynebacterium diphteriae
List two common pathogens in the phyla: Firmicutes
(also known as low G+C gram positives)
- Faecalibacterium prasunitzii (beneficial)
- C. difficile
- Staph aureus
- Strep pneumo
- the human small and large intestine are dominated by obligate anaerobes of the phyla Firmicutes and Bacteroidetes
List two common pathogens in the phyla: Proteobacteria
- E. coli
- Shigella
- Salmonella
- Yersinia pestis
- Vibrio cholerae
- H. influenza
- L. pneumophila
- N. gonorrhoeae
- N. menigitidis
- B pertussis
- Rickettsia sp.
Development of microbiome in infants
- infants are born sterile
- colonized by trillions of bacteria in days
- in weeks: levels of an adult
- development of immune system occurs in parallel.
What environmental factors influence the patterns of colonization in infants?
- Mode of delivery (Cesarean vs Vaginal)
2. Feeding (breast milk vs. formula)
Dysbiosis
- imbalances in microbiome composition
- IBD
- Antibiotic assoc diarrhea (C. diff)
- obesity
- bacterial vaginosis (characterized by a LOSS of protective species)
- “non-bacterial” prostatitis
- pouchitis
- Type 1 diabetes
- Mother to child HIV transmission
- MRSA colonization and infection
Crohn’s disease: what is diminished?
Diminished levels of beneficial Clostridium and Bacterioides species
What is one of the major challenges in studying the human microbiome and disease?
It is hard to distinguish whether dysbiosis is an etiological factor in a disease or simply and inconsequential secondary effect of disease.
