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Bacteria
Transmission, disease, classification
| Term | Definition |
|---|---|
| What are Koch's postulates? | Bacterium is present in every case of disease, bacterium can be isolated from disease and grown in pure culture, specific disease must be reproduceable from pure culture in healthy susceptible host, bacterium must be recovereable again |
| What is the purpose of Koch's postulates? | Demonstrates criteria for causal relationship btwn microbe and disease |
| What types of bacterial diseases are there? | Acute (days) -> pneumonia, gastroenteritis, chronic (years) -> syphilis, TB, may involve carriers |
| What modes of transmission for bacterial diseases are there? | Direct human contact -> horizontal, vertical, indirect human contact -> inanimate objects, food, water, animals, soil |
| What is horizontal transmission? | Direct human contact -> sexual (syphilis, gonorrhea), respiratory tract (air-borne droplet) -> upper (pharyngitis, diphtheria), lower (whooping cough, TB, pneumonia), self-flora contamination (UTI from GI tract), skin/eyes (fasciitis, conjunctivitis) |
| What is vertical transmission? | Direct human contact from mother to child -> transplacental (syphilis), parturition (gonorrhea) |
| What are nosocomial infections? | Indirect human contact w/ inanimate objects -> UTI following catheterisation, surgical wounds, burn infections |
| What are opportunistic infections? | Drug resistant pathogens -> Staph aureus, Pseudomonas aeruginosa, weakened immune system -> HIV/AIDS, missing gut flora -> Clostridium difficile after Abx exposure |
| What bacteria transmit via food? | Intoxication -> staphylococcal food poisoning, botulism, infection -> salmonella (chicken, eggs), E.coli (beef) |
| What bacteria transmit via water? | Orofaecal -> cholera, dysentry, typhoid, air-con/respiratory -> Legionnaire's disease |
| What bacterial infections are zoonotic? | Animals have disease/are reservoirs -> food-borne diseases from livestock (E.coli, bovine TB), wild animals (Lyme disease from ticks) |
| What bacteria transmit via soil? | Spores enter wound -> tetanus, gas gangrene |
| What are endemic diseases? | Disease occuring regularly at low/moderate frequency in particular region -> dental caries (decay/cavity), malaria in certain countries |
| What are epidemic diseases? | Sudden appearance of disease/disease increased above endemic level in particular region -> diphtheria, bubonic plague |
| What are pandemic diseases? | Global epidemic -> cholera, MRSA |
| What types of bacterial infection outbreaks are there? | Point source, continuous source, propagated outbreaks |
| What are point source outbreaks? | Arise from single origin -> aided by bacterial survival/replication outside host -> Legionnaire's disease -> pneumoni disease from aircon units |
| What are continuous source outbreaks? | Point source not eradicated -> typhoid (carrier), nosocomial Staphylococci, MRSA (one healthcare worker carrying disease) |
| What are propagated outbreaks? | Host-to-host transmission -> increases infection # -> whooping cough, TB, gonorrhoea, dysentry, cholera |
| What kind of transmission is the plague? | Bubonic plague via Yersinia pestis -> rodents were point source -> continuous source -> spread to humans (disease becomes pneumonic) -> becomes a propagated outbreak via exhaled infected droplets |
| How are bacteria classifies? | Prokaryotes -> living cells maintaining structural integrity during replication -> make ATP/proteins so not intracellular parasites (self-biosynthesis xcp Chlamydia) |
| How do bacteria differ from mammalian cells? | Smaller -> large SA:V to sense environment, have peptidoglycan cell wall, no nucleus -> free cytoplasmic DNA w/ coupled transcription/translation, motility mechanisms via flagellum from cell envelope (eukaryotic flagellum from cell cytoskeleton) |
| What is the structure of bacterial cytoskeleton? | Tubulin homologue -> FtsZ -> involved in cell division by binary fission via polymerisation, actin homologue -> MreB -> spiral structure to control/maintain cell shape |
| What is the bacterial genome like? | Small (<9000 genomes) obligate intracellular parasites/large evolve metabolic diversity, haploid cells w/out meiosis (horizontal gene transfer via plasmids/phages), single/circular chr, polycistronic mRNA (unstable, regulate transcription initiation) |
| Which bacteria produce endospores? | Gram +ve -> Clostridium tetani/perfringens/difficile/botulinum, bacillus anthracis |
| How are endospores synthesised? | Bacterial cell differentiates (sporulation) forming daughter cell inside maternal cell -> favourable environmental conditions -> gene transcription switched on -> daughter cell germinates as spore and separates from maternal cell? |
| What are the characteristics of endospores? | Highly resistant to harsh conditions -> thick cell wall, compact DNA, low metabolism, survive desiccation/radiation/heat/starvation/disinfectants -> difficult to eradicate |
Created by:
vykleung
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