How Bacteria cause Disease

Terms:

Viralence

 Viralence factors

Viralence: pathogen strength

Viralence factors:characteristics that help pathogen cause disease

Adherance:

• Capsule/Philli
• Ability to invade tissues-->destruction of epithelial tissue
  

Invasion/Colonization

Pt. 2

• Entry into host cell
• Use host as a hide out
• or as a vehicle to bury deeper into body
• "espinonage"

• Bacteria have to evade host defenses through phagocytosis
• avoid with capsule-->slippery coating, hard to catch
• ex. steptococcus phemonia
• rough vs. smooth (smooth is hard to catch bc has capsule)

After bacteria is captured

Ability to live in phagocytic cell

ex. Mycobacterium tuberculosis (TB)

Has a waxy cell wall

• digestive enzyme can't get through that (lysosome)
• Staphyloccus aeureus (Merca)
• lives and reproduces in lungs-->kill phagocytic cells
• disenegrates lung tissue
• G +

Factors that Damage the Host

A. Secreted Toxins

Exotoxins:

• poison direct host, direct physical damage
• kills macrophages
• inhibit normal cell function--> can't work
• ex. Tetanus
• G+
• through wound infection
• needs aneorobic conditions
• secretes exotoxins
• targets nerves, interferes with nerve relaxation

• coating outside cell wall
• fxns: protection
• adhesian to surfaces
• ex. streptococcus mutans
• G+, adheres to teeth

• Rod shaped-->bacillias/bacili
• Sphere-->caccus/cocci
• Spirals--> spirachete and spirillam/spirilli

Projections and Flagella

• Bacteria: flagella stiff and rigid: propellor like mov't
• eukaryotic: whip like motion: sperm
• pilli/pilus: hair like projections
• purpose: adhesion-->attach to other bacteria, transfer plasmids
• bacteria mating: transfers bacteria, not species related
• attach to surfaces

• plasmid, cell membrane, cell wall, bacterial chromosome
• a lot smaller than a eukaryotic cell, similar in size to a mitochondria
• rod: bacillias/bacilli
• sphere: caccus/cocci
• spirals: spirachete and spirillam/spirilli

• function: protection
• adhesian to surfaces
• ex. streptocococus mutans-->gram + sphere, adheres to teeth

• bacteria: flagella stiff and rigid-->propeller like, mov't
• eukaryotic-->whip like motion
• pilli/pilus: hair like projections
• purpose: adhesion/attachment
• attach to other bacteria and transfer plasmids/bacteria, not species related

• active vaccination-->inacctivated toxin
• booster shot
• Treatment: clean wound, dont' want bacteria to have a place to live w/out 0₂   
  
• never had the shot? passive vacine, antibodies against the toxin, anti-toxin

• as a molecule, not a toxin
• structural componant: G- outer membrane
• Does not cause direct damage-->triggers inflamation
• Host over reacts, causing damage ("friendly fire")
• sing that G- bacteria has infected body

1. Normal response to damage or infection: localized inflammation
2. Abnormal response: systemic inflammation

• when bacteria or cell wall fragments enter the blood stream-->massive inflammatory response-->septic shock
• sepsis: microbes in blood
• shock: severe drop in blood pressure
• not enough blood in circulation: symptoms:
• fever
• leaky blood vessels throughout body: too much fluid leaves circulation

• small clots form around body-->deplete clotting factors: hemoraging (uncontrolled bleeding)--> constantly breaking
• Result: lowered blood flows in organs: o₂ starvation
• Treatment: fluid
• vassopressor: constricts blood vessel

structure: contain genetic materials:

DNA:herpes, papilloma

RNA: Influenza, eblola

contains protein shell: capsid

shapes: helical, icosahedron, complex

• viral envelope-->stolen from host cell's membrane
• some viruses carry own enzymes inside

• can't live w/out host cell
• Attachment: protein on virus surface-->binds protein on host cell surface (viral receptor)
• ex.: HIV binds T_h
• specific binding of virus w/viral recptr. determines host range

viral replication-->proteins replication and genetic material, through: transcription/translation

to synthesize viral proteins

• viral which has a membrane, steals viral envelope from host cell
• 1) cell lysis-->virus bursts out, cell is killed in process
• 2) Budding: viral genetic material, pkg. capsid, membrane proteins insert into host membrane
• becomes envelope, virus kills host cell

• general info: 10-20,000 ppl. die a yr. (young/old)
• death rate: .22
• Transmission: Ingestion of airborne droplets
• hosts: birds/mammals
• incubbation: 2-3 days

• capsid: helical
• genetic material: RNA in 8 segments--each segment has own mini capsid, w/envelope

• H protein: hemogglutinim: attaches to host
• N-neurominadase: facillitates exit stage
• H protein function: attachment, virus needs to retain function of H protein-->part of H protein unchanged
• Other parts of H protein vary, on surface strain designations
• H1N1, H3N2, common human virus
• H5N1-avain flu

• viral receptor-->h protein attaches to host receptor
• Entry: uncoating
• Reproduce viral RNA/protein-->for capsid/envelope
• assembly-->adding H+N proteins to membrane
• Budding Exit
• need to get all 8 segments into offspring

What viral componants would serve as the best antigens?

H+N-->immune system (B cells) recognize H+N proteins (b/c on surface) generate different viral strains

• Antigenic drift(minor differences):
• Viral RNA mutation (more freg. than DNA)
• changes in H+N proteins
• Antigenic Shift (major differences):
• mixing of viral gene segments from influenza, normally infects of different species
• an indvidual cell needs to be infected w/both strains-->pigs, intermediary

Tissue range: birds

mild: replication is limited to digestive tract

virulent: infects all tissue

in humans: upper respiratory

severe: lungs

antigenic shift: mixing of influenza viruses

ex.: human+avian

prevention: vaccine, antiviral drug

Fighting infections w/chemicals

Strageties for designing antimicrobials

• goals: inihibit/kill pathogen w/out harming host, need target, unique to pathogen
• Antimicrobials:
• antibiotic: bacteria fighting, internal
• antibacterial: "", external
• antivirals
• antifungals
• antiprotozal

Potential Drug targets

• Pathogen: Bacteira
• Target: cell wall
• Ex. penicillin, methicillin
• Viruses
• Target: ribosomes
• ex. tetracycline, erythromycin
• Target: Unique protein/enzyme
• ex. Tamiflu, N protein, flu has a viral envelope

kill normal flora as well as pathogen-->if viral infection

• if wiped out bacteria has more opps. to settle