Park-Infectious Disease Flashcards
Commensalism
-the colonizing bacteria acquire nutrition and the host gets neither benefit nor harm
-commensal bacteria in a human body (normal flora) are 10x more than human cells
Mutualism
-both the microorganism and the host derive benefits from the interaction
Infectious disease
the host sustains injury or pathologic damage
infectious agents
prions, viruses, bacteria, fungi, and parasites
Viruses
obligate intracellular pathogens
What are the components of. a virus
capsid (protein coats) and genome (RNA or DNA)
How does a virus develop an envelope?
they become enclosed in a envelope that is derived from the cytoplasmic membrane of the host cell
What can viruses cause
Lysis and death of the host cell during replication
Can a virus remain in the cell without causing disease?
Yes, a virus can remain in a latent, non replicating stage, for long periods without causing disease
-ex: varicella zoster virus (chicken pox at first and shingles later)
Can viruses cause cancer?
yes, an example is human papilomavirus (HPV) which can cause cervical cancer
Bacteria are___
prokaryotic
What are shapes of bacteria?
-spherical (diplococci, staphylococci, streptococci)
-elongated (bacilli)
-helical (sprilla [spirochetes])
Spirochetes
-anaerobic (bacteria)
-borrelia burgdorferi (Lyme disease)
-treponema pallidum (syphilis)
Mycoplasma
-bacteria that is much smaller than other bacteria
-have no cell wall which makes them resistant to cell-wall inhibiting antibiotics (such as penicillins)
-mycoplasma pneumoniae (pneumonia)
Rickettsiaceae
-obligate intracellular pathogen (bacteria)
-transmitted via arthropod vectors (mites, fleas, ticks, lice)
-rickettsia rickettsii (rocky mountain spotted fever)
chlamydiaceae
-obligate intracellular pathogen (bacteria)
-transmitted via person-to-person contact
-chlamydia trachomatous (sexually transmitted and can cause conjunctivitis in newborns)
Superficial mycoses (dermatophytosis)
-fungi
-ringworm, athletes foot (tinea pedia), and jock itch (tinea cruris)
-caused by dermatophytes whose infection is limited to the cooler cutaneous surfaces
Systemic mycoses
-serious fungal infections of deep tissue (rare)
-candidiasis (yeast infection)..opportunistic infection of candida albican, which is commensal flora in the skin, mucous membranes, and gastrointestinal tract
-aspergillosis…a lethal form of pneumonia caused by aspergillus, a common mold in people with lung diseases or immunocompromised patients
What helps protect the body from systemic mycoses
-intact immune mechanisms and competition for nutrients provided by the bacterial floral normally keep colonizing fungi in check
what can lead to opportunistic infections?
a disease or an antibiotic therapy can upset the balance and allow opportunistic infections to arise
Protozoa
-unicellular animals (parasite)
-plasmodium (malaria)…vector born (mosquito)
-entamoeba histolytica (amebic dysentery, or amoebiasis)…contaminated water and food
-giardia duodenalis (giardiasis)…contaminated water and food
Helminths
-wormlike parasites
-roundworms, tapeworms, flukes
-mainly in GI
-transmission primarily occurs through the ingestion of fertilized eggs (ova) or the penetration of infectious larval stages through the skin
Parasitic arthropods
-ectoparasites…mites (scabies), chiggers, lice (head, body, pubic), and fleas
-these may serve as vectors of other infectious diseases such as the bubonic plague which was spread by fleas
prions
-misfolded protein found in infectious material
-creutzfeld-jakob disease (associated with other neurodegenerative conditions) is human version of mad cow disease
epidemiology
the study of the patterns and determinants of health with the goal of controlling disease and health problems
incidence
the number of new cases of an infectious disease that occur within a defined population (such as per 100,000 people) over an established period of time (such as monthly, yearly, etc)
disease prevelence
the number of active cases at any given time in a population
endemic
relatively stable incidence and prevalence in a particular geographic region
epidemic
an abrupt and unexpected increase in the incidence of disease over endemic rates
pandemic
the spread of disease beyond continental boundaries
penetration
-any disruption may allow the invasion of pathogens, which normally cannot penetrate intact skin or mucous membranes
-ex. abrasions, burns, needles, insect and animal bites
sexually transmitted infection
-transmitted by the exposure of the intact skin or membrane to pathogens
-ex. gonorrhea, syphilis, chlamydia, and genital herpes
congenital infection
-infection of a child during gestation or birth from mother (vertical transmission)
-ex. toxoplasmosis, other (syphilis, varicella zoster, parvovirus B19), rubella, cytomegalovirus infection, and herpes simplex virus (TORCH infection) and HIV
what are examples of direct contact transmission
-sexually transmitted infection
congenital infection
TORCH infection
-Toxoplasmosis
-Others (syphilis, varicella zoster, parvovirus B19)
-Rubella
-Cytomegalovirus infection
-Herpes simplex virus
Ingestion
-cholera, typhoid fever, amoebic dysentery, food poisoning, etc
-the low pH of the gastric acid acts as a barrier for many pathogens but some are resistant to low pH
-the normal bacterial flora of the bowel often compete with the pathogens
What pathogens are resistant to low gastric pH?
-shigella
-giardia
-have differences (lower) infectious dose
Inhalation
-bacterial pneumonia, meningitis, and tuberculosis
-viral infections such as measles, mumps, chickenpox, influenza, the common cold, and COVID
-the respiratory tract is equipped with multiple-tiered defense system (mucous membrane, coughing, antibodies and enzymes, phagocytosis, etc)
What can weaken the defense system of the respiratory tract?
-smoking and diseases such as cystic fibrosis can impair the defense system
Endogenous
opportunistic infection acquired from the hosts own microbial flora
Exogenous
environment (water, food, soil, air)
Person
direct contact
Fomites
-inanimate objects contaminated with infected body fluids
-rhinovirus through shared toys
-HIV and HepB virus through shared syringes
Animal (zoonoses)
-infectious diseases passed from other animal species to humans
-HIV, rabies. plague, influenza, SARS, MERS
-70% of emerging viral infections are zoonoses
Vector
-biting arthropod
-Lyme disease by deer tick
-west nile virus by mosquitos
nosocomial infection
healthcare associated infection (occurs in health care setting)
What are types of places an infection can be acquired
-nosocomial
-community
What are the stages of a disease?
-incubation period
-prodromal
-acute
-convalescent
-resolution
what happens during the incubation period?
-active replication of a pathogen without recognizable symptoms
What happens during the prodromal stage?
-initial appearance of symptoms
-mild fever, myalgia, headache, and fatigue (somewhat nonspecific)
what happens during the acute stage?
-maximum impact of the infectious process
-inflammation and issue damage (more specific)
What happens during the convalescent stage?
progressive elimination of the pathogen
What happens during the resolution stage?
total elimination of a pathogen
virulence factors
substances or products generated by infectious agents that enhance their ability to cause disease
What are virulence factors?
-exotoxins
-endotoxins
-adhesion factor (adhesins)
-evasive factors
-invasive factors
exotoxins
-proteins released by pathogenic bacteria
-inactive key cellular constituents (diphtheria toxin inhibits protein synthesis)
-many are superantigens inducing excessive and nonspecific inflammatory responses
What can superantigens cause?
-induce excessive and nonspecific inflammatory responses
-bind to the (major histocompatibility complex) MHC of antigen-presenting cells and T cell receptors
-T cells are activated regardless of the antigen presented on MHC
endotoxins
-lipids and polysaccharides that are not released (lipopolysaccharides)
-can induce clotting, bleeding, inflammation, hypotension, and fever (endotoxic shock)
what are signs and symptoms of endotoxic shock?
-clotting
-bleeding
-inflammation
-hypotension
-fever
Adhesion factors (adhesins)
-bind to macromolecules on the surface of host cells
-adhesion is critical for the colonization of the pathogens
-some pathogens form a mucous layer (slime)
evasive factors
-inactivate the hosts immune system
-leukocidins form pores in the cell membrane of neutrophils and macrophages
-some pathogens survive and reproduce within phagocytes after phagocytosis by neutralizing lysosomal contents with evasive factors
invasive factors
-facilitate the penetration of anatomic barriers
-pseudomonas aeruginosa collagenase breaks skin
Anthelminthics are drugs to treat infections by___
A. viruses
B. bacteria
C. fungi
D. protozoa
E. wormlike parasites
E. wormlike parasites
Which of the following pathogens is a protozoon (unicellular animal) For your information, the name of the disease caused by each pathogen is shown in parentheses.
A. Candida albican (candidiasis)
B. rickettsia rickettsia (rocky mountain spotted fever)
C. mycoplasma peumoniae (pneumonia)
D. plasmodium falciparum (malaria)
E. borrelia burgdorferi (Lyme disease)
D. plasmodium falciparum (malaria)
Tetanus toxin induces paralysis in the host cell by blocking neurotransmitter release. What type of virulence factor is tetanus toxin?
A. endotoxin
B. exotoxin
C. evasion factor
D. adhesion factor
E. invasion factor
B. exotoxin
Which of the following infections is not a classical example of congenital infections (Hint: These infections are frequently called TORCH infections)
A. toxoplasmosis
B. rubella
C. cytomegalovirus infection
D. herpes simplex virus infection
E. shigella
E. shigella
Which of the following is an example of infection through fomites?
A. a student has contracted COVID after talking to an infected friend
B. a man contracted syphilis after a sexual contact
C. a hotel guest contracted the flu after touching a contaminated button in an elevator
D. a woman has contracted lyme disease after a tick bite
E. a hiker has contracted amoebic dysentery after drinking water from a lake
C. a hotel guest contracted the flu after touching a contaminated button in an elevator
