VL2: Infectious organisms: Bacteria Flashcards
Why are infectious diseases important? Who is affected?
- After cardio most important cause of death
- 19% of total deaths (WHO)
- < 45 years
- poor, developed countries
Which type of infectious diseases are most important? most infected, highest mortality(examples?)
Most infected people: H. pylori 50% (risk of gastric cancer), M. tuberculosis 30%
Mortality:
- Respiratory diseases (M.tuberculosis)
- Diarrheal diseases (E.coi, Vibrio cholerae, Shigella)
Definitions of symbiotic, commensal and parasite
Symbiotic: benefit host and B
Commensal: one partner benefits, the other is unaffected
Parasite: one benefits, the other is harmed
Why is Symbiotic Commensal Parasite classification sometimes flawed?
mutual benefit can be difficult to observe
Many significant pathogens are commensal!
It depends on location, number and host immune status
When did microbes and animals appear?
Microbes: 3.5 billion years ago
Animals: <1 billion years ago
4 important evolutionary innovations through symbiosis
- Eukaryotic cell (mitochondria)
- Photosynthesis (plastids)
- Colonization of land by plants (mycorrhizae fungus)
- Nitrogen fixation by plants (rhizobia in roots)
How many B cells are in the human body compared to own cells?
10 times more
How many species live in the intestine? What features have they in common?
- 500-1000 different species (1.5kg per person)
- mostly anaerobic
3 steps in the development of intestinal microflora
- at birth: sterile
- colonization of newborns (oral-anal direction)
- microflora is well established after 1 month and changes little afterwars
How/why does the microbiome change over time?
Birth-Adulthood: aerobes ->anaerobes (at weaning)
can change after antibiotic treatment
otherwise stays mostly the same
How are commensals tolerated by the immunse system? Is this always the case?
Carbohydrate surface structures are presented to immature immune system anti-inflammatory mechanisms that result in tolerance to commensals some diseases (e.g. inflammatory bowel disease) may be immune response to a normal commensal B
1 Example skin flora, what is it for?
Gram positive cocci: Staphylococcus aureus
Gram positive rods: Corynebacterium
Gram-negative rods: Propionobacterium (acne)
skin flora protects skin against colonization
relatively low numbers of B
1 Example oral cavity/ nasopharyngeal flora
Streptococci, Staphylococci, Propionibacterium Haemophilus Neisseria Corynebacterium Mycoplasma
Urogenital flora (1 example)
Sterile except for vagina and distal 1 cm of urethra
Lactobacilli
Staphylococci
4 examples of how B are essential for health (brief explanations)
- Development
induction of blood capillaries in intestine - Nutrition
Absorption and processing of food - Defense
Protection against other infecious and dangerous microbes
4 Immunity
Protection against allergies and cancers?
which 4 criteria can be used to classify B?
- morphology, biochemistry, staining
- lifestyle
- molecular phylogeny (rRNA, other molecules)
- relevance to human disease
3 Identification methods?
morphological characteristics differential staining (gram, acid-fast stainign) Biochemical tests (determines presence of B enzymes) Morphological methods do not reflect phylogeny!!!
6 eubacterial lifestyles?
- Extracellular*
- Facultatively intracellular*
- Extremophillic (mostly archea)
- Epicellular bacteria*
- Obligate intrracellular and symbiotic
- Obligate intracellular and parasitic*
- human pathogens
3 Examples of groups (based on morphology)
Spirochetes (Genus Borrelia, Leptospira)
Gram positive Cocci (Streptococcus, Staphylococcus)
Endospore forming Gram-positive rods and cocci (Genus bacillus, clostridium)
How is phylogeny determined?
some obtained from fossil record
for microbes mostly ased on rRNA and protein sequences
What is a cladogram?
shows phylogenetic reltionships among organisms
nodes represent % simlarity between species
3 branches of (new) tree of life
bacteria
archaea
eucarya
Name 3 differences between the 3 domains of life
ABE
cell type: prokaryotic, prokaryotic, eukaryotic
membrane lipids: branched carbon chains, straight C, straight C
ab sensitivity: no yes no
rRNA loop: -+-
common arm of tRNA -++
Where are most B pathogens phylogenetically?
mostly
Firmicutes (Gram positive)
Proteobacteria
(Spirochetes)
Examples for classification based on type of human disease
- respirator tract+ ear nose throat infections (s.pneumoniae, h. influenzae, s-aureus, m.tuberculosis)
- Urinary tract infections (e.g. E.coli, enterococcus, s. epidermidis, s-aureus, p. aeruginose)
- Gastrointestinal (Salmonella, shigella, vibrio)
- wound infections
- cardiovascular infections
