Question

Medical Microbiology Tutorial: Introduction to Infectious Bacteria

Answer 1

\({\bf{Features:}}\)
- capsule: structure outside the cell envelope, usu. composed of polysaccharides, that help bacteria avoid phagocytosis (apparently the exact mechanism isn't completely clear but it's possible that the physical surface of a capsule is harder to bind to?)
- flagellae: whiplike structure used for movement. acts as adhesin and antigen in infection
- fimbriae/pilli: short protein extensions used to adhere to hosts
- toxins: secreted compounds that damage host in some way
- enzymes: proteins that catalyze certain processes such as damaging host tissue or breaking down antibiotics

\({\bf{Gram-Positive~vs.~Gram-Negative:}}\) covered this a lot more in my other micro-bio tutorials but going over the very basics here



Gram Positive
- stains purple
- thick peptidoglycan layer
- peptidoglycan layer is made of NAG and NAM saccharides, + some protein

Gram Negative
- stains pink
- thin peptidoglycan layer
- outer membrane outside of peptidoglycan layer, made of LPS (lipid A + polysaccharides)

Answer 2

\({\bf{Transmission:}}\) passage of a pathogen from one host to another (or on a larger scale, from one group to another)

Methods of transmission:
- airborne
- vectors
- iatrogenic (medical treatment)
- fecal/oral
- physical contact, typically (skin-to-skin)
- sexual
- vertical (mother-to-offspring)

Strategies to increase transmission:
- mostly covered in the features section
- antigen mimicry: the production of bacterial antigens similar to target antigens to bypass or deliberately activate host immune response
- quorum sensing: production and response to autoinducers (chemical signals) to direct bacterial behavior and gene transcription en masse
- biofilms: matrix structure produced by bacterial colony to increase adhesion and protect against host defenses or external treatments

Answer 3

... ok I split the introductory material into 2 parts but didn't realize the bacterial section was this short, oh well

Sources:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4009794/
- https://www.ncbi.nlm.nih.gov/pubmed/11544353
- https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/fimbriae
- https://www.sciencedirect.com/topics/medicine-and-dentistry/molecular-mimicry
- http://sitn.hms.harvard.edu/flash/special-edition-on-infectious-disease/2014/an-introduction-to-infectious-disease/
- lecture notes