replication continues; host shows signs and symptoms
21
New cards
illness
signs and symptoms are most severe in host
22
New cards
decline
pathogen number starts to decrease; host's immune system is weak and vulnerable to secondary infection
23
New cards
convalescence
host starts to recover
24
New cards
acute disease
relatively short (hours, days, week)
25
New cards
chronic disease
longer time (months, years, lifetime)
26
New cards
latent disease
comes in episodes; pathogen replicates when disease is active
27
New cards
Koch's postulates
set of standards that must be met to demonstrate that X pathogen causes X disease
28
New cards
Koch's postulates
1) The suspected pathogen must be found in every case of disease and not be found in healthy individuals.
2) The suspected pathogen can be isolated and grown in pure culture.
3) A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1.
4) The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2.
29
New cards
Koch's assumptions (WRONG)
1) Pathogens are found only in diseased individuals.
2) All subjects are equally susceptible to infection.
3) All pathogens can be grown in culture.
30
New cards
Molecular Koch's postulates
identifies gene instead of pathogen; improved postulates that overcame some of Koch's limitations
31
New cards
Limitations of Molecular Koch's postulates
1. genetic manipulation of some organisms isn't possible with current techniques 2. some diseases do not have suitable animal models
32
New cards
pathogenicity
ability of a pathogen to cause disease
33
New cards
virulence
degree of pathogenicity ex: highly virulent - Bacillus anthracis induces severe signs and symptoms ex: low virulent - Rhinovirus induces low signs and symptoms
34
New cards
virulence curve
how virulence can be modeled in controlled experiments
35
New cards
median infectious dose (ID50)
number of pathogens required to infect 50% of those inoculated
36
New cards
median lethal dose (LD50)
number of pathogens required to kill 50% of those infected - LD50 is 10^4 pathogen cells or virions
37
New cards
primary pathogen
can cause disease in a host regardless of the host's resident microbiota or immune system ex: enterohemorrhagic E. coli (mainly due to Shiga toxin)
38
New cards
opportunistic pathogen
can only cause disease in situations that compromise the host's defenses (protective barriers, immune system, or normal microbiota) ex: Candida albicans with disrupted microbiota ex: UTI caused by E. coli
can occur in many ways: pathogens must be exposed to portals of entry to begin adhesion - some portals are worse than others (ex: mucosa)
42
New cards
TORCH infections
pathogens that can cross placental barrier as portal of entry
43
New cards
Torch
toxoplasmosis --\> Toxoplasma gondii (protozoan)
44
New cards
tOrch
syphilis --\> Treponema pallidum (bacterium) chickenpox --\> Varicella-zoster virus (human herpesvirus 3) hepatitis B --\> Hepatitis B virus (hepadnavirus) HIV --\> Retrovirus fifth disease (erythema infectiosum) --\> Parvovirus B19
45
New cards
toRch
rubella (german measles) --\> Togavirus
46
New cards
torCh
cytomegalovirus --\> Human herpesvirus 5
47
New cards
torcH
herpes --\> herpes simplex virus (HSV) 1 & 2
48
New cards
adhesion
pathogens' varying capability of colonization
49
New cards
adhesins
molecules/structures that bind to certain host receptors
50
New cards
biofilm
production of community glycocalyx
51
New cards
invasion
occurs when colonization is established; pathogens generally produce toxins to allow further colonization into body/tissue and protection from immune system - virulence plays a role in degree of invasion ex: Helicobacter pylori urease production
52
New cards
intracellular pathogens
invade via endocytosis and evasion of host immune defenses
53
New cards
invasion mechanisms
1. Effector proteins are secreted to trigger entry - membrane ruffling (ex: Salmonella and Shigella spp.)
2. Surface proteins allow for binding to host cell (trojan horse approach)
can lead to secondary infections of different pathogen ex: HIV lowers immune system and opens door for yeast and others; rhinoviruses can lead to bacterial pneumonia
59
New cards
transmission
persistence passes on pathogen onto a new host through a portal of exit
60
New cards
virulence factors
pathogen product that assists in ability to cause infection and disease - dictate how severe and extensive a disease is; some have more than one ex: adhesion factors, exoenzymes, toxins, immune evasion
61
New cards
adhesins
proteins that aid in attachment to host cell receptors - found in ALL microbial types (viral, fungal, bacterial, etc.) - commonly found on fimbriae or pili - can initiate biofilm formation in some species
62
New cards
-emia
presence of pathogen in blood
63
New cards
bacteremia
bacteria in blood
64
New cards
viremia
viruses in blood
65
New cards
toxemia
toxins in blood
66
New cards
septicemia
bacteria present and multiplying in blood - patients with septicemia (septic) can lead to shock (life threatening disease in BP)
67
New cards
exoenzymes
extracellular enzymes used to invade host tissues - glycohydrolases, nucleases, phospholipases, proteases ex: collagenase produced by C. perfringens causing necrosis and gas gangrene
68
New cards
toxins
biological poisons that assist in ability to invade and cause tissue damage (toxigenicity)
69
New cards
endotoxins
lipopolysaccharides that triggers host inflammatory responses; can cause severe fever and shock
70
New cards
exotoxins
proteins mostly produced by Gram (+) - targets receptors in specific cells
blood cells of the horseshoe crab mixed with patient's serum; observed chromogenically or by coagulation
73
New cards
ELISA
uses antibodies to detect endotoxins
74
New cards
intracellular targeting
a division of exotoxins with A & B regions for activity and binding ex: diptheria and botulinum toxin
75
New cards
membrane disrupting
division of exotoxins aka phospholipases that degrade bilayer membrane ex: Bacillus anthracis and Rickettsia spp.
76
New cards
hemolysins and leukocidins
membrane disruptors that can target RBC, WBC, and other cells
77
New cards
superantigen
division of exotoxins that trigger excessive production of cytokines by immune cells ex: Staphylococcus aureus and Toxic Shock Syndrome
78
New cards
host evasion
mechanisms to evade phagocytosis ex: capsules that enlarge bacterial cell so phagocytes cannot engulf pathogens ex: proteases digest host antibody molecules
79
New cards
antigenic variation
alteration of cell surface proteins to hide from immune cell recognition (example of host evasion mechanism)
80
New cards
antigenic drift
result of point mutations causing slight changes in spike proteins (H & N)
81
New cards
antigenic shift
major change in spike proteins due to gen reassortment
82
New cards
virulence in fungi
Many properties similar to bacteria; adhesins, proteases, and toxins ex: Capsule (+) Cryptococcus spp. can cause pneumoniae and meningitis
83
New cards
mycotoxins
fungal toxins produced by Claviceps purpurea and Aspergillus spp. that contaminate grains and other staple crops
84
New cards
virulence in protozoans
have unique features for attachment ex: Giargia lamblia uses adhesive disk of microtubules to attach to intestines ex: Plasmodium falciparum quickly changes adhesive protein for RBCs to avoid immune recognition; causes chronicity in malaria patients
85
New cards
virulence in helminths
tissue penetration commonly achieved with proteases (worms that burrow into skin) ex: roundworms produce cuticle to last longer against host defense assaults ex: Schistosoma mansoni degrades host antibodies to halt immune defense
86
New cards
"Glycan gimmickry"
mimic host cells to evade immune system
87
New cards
epidemiology
field that studies distribution and timing of diseases (infectious and non-infectious) Determines: 1) Etiology 2) Transmission 3) Susceptible populations
88
New cards
morbidity
number of individuals with disease rate calculation: \#/population
89
New cards
mortality
number of deaths from disease rate calculation: \#/population
90
New cards
prevalence
number of individuals at certain time
91
New cards
incidence
number of new cases
92
New cards
4 patterns of incidence
1. Sporadic 2. Endemic 3. Epidemic 4. Pandemic
93
New cards
sporadic
occurs occasionally without regional concentration ex: tetanus, rabies, plague
94
New cards
endemic
constantly present in certain region ex: malaria, ebola, chickenpox
95
New cards
epidemic
larger than normal amount of cases ex: influenza, west nile
96
New cards
pandemic
epidemic that is cross continental ex: virulent influenza, ebola, etc.
97
New cards
etiology
determining the causative (etiological) agent of infectious disease; epidemiology helps provide clues and the standard procedure is Koch's postulates
98
New cards
CDC (Center for Disease Control)
protects public from disease/injury by providing physicians and health-care workers with updates on public health issues & latest data on notifiable diseases ex: publication of the MMWR (Morbidity and Mortality Weekly Report)
system where all cases must be reported by physicians; these studies track notifiable diseases to determine risks ex: west nile, HIV, measles, etc.
100
New cards
John Snow
British physician and father of epidemiology; his study led to the discovery of the contaminated water pump that was responsible for the 1854 cholera London epidemic