CH. 26 Microbial Diseases Flashcards
What is herd immunity? What type of infection is herd immunity most effective against? Least effective against? Provide an example of each.
Herd immunity is immune individuals acting as barriers to the spread of infection
Herd immunity is most effective against communicable diseases (person-to-person spread) and is NOT applicable to non-communicable diseases (ex. tetanus)
Describe Staphylococcus aureus
-Gram-positive
-Cocci
-Enter the body by breaking through the skin or hair follicles and cause boils, impetigo, and scalded skin syndrome (skin/soft tissue infection)
-Spread by direct contact if skin has been breached
-Opportunistic pathogens
Virulence factors:
-Toxins: anti-phagocyte; enterotoxin
-Resists opsonization, lysozyme, and antibiotics
-Coagulase; hyaluronidase
Describe Streptococcus pyogenes
-Gram-positive
-Cocci
-Cause sore throats and rheumatic fever. It also causes erysipelas (toxin causes tissue destruction) and necrotizing fasciitis (“flesh-eating” disease)
-Spreads by airborne droplets
-Primary pathogens
Virulence Factors:
-M protein: prevents complement activation; facilitates adherence
-Hyaluronic acid capsule: non-antigenic
-Produces streptokinase, hyaluronidase, etc.
Describe Streptococcus pneumonia (including primary and secondary)
-Gram-positive
-Cocci
-A secondary infection proliferating in alveolar spaces and bronchi in the lungs (fluid buildups occur) affecting the respiratory system
-Causes pneumonia & meningitis
-Spreads by airborne droplets
-Primary pathogens
Virulence Factor:
-Capsule that prevents phagocytosis
Describe Corynebacterium diphtheriae
-Gram-positive
-Golf-club shaped
-Forms gray membrane in the throat causing sore throat and fever (diphtheria)
-Spreads by airborne droplet transmission
-Primary pathogens
Virulence Factors:
-Produces toxin that interferes with protein synthesis and enters the bloodstream
Describe Bordetella pertussis
-Gram-negative
-Coccobacillus
-Inhibits the mucociliary by binding to lung ciliated cells in the trachea to later destroy them (whooping cough)
-Spread by airborne
-Primary pathogens
Virulence Factors:
-Capsule
-Toxins
-Tracheal cytotoxin
-Pertussis toxin
Describe Legionella pneumophila
-Gram-negative
-Rod-like
-Inhalation of aerosols due to being/invading in macrophages and replicating inside of them
-Affects the lung in the form of atypical pneumonia
-Spread by airborne droplets
-Opportunistic pathogens
Virulence Factors:
-Capsule toxins
-Tracheal toxins damage ciliated cells
Describe Shigella & enteroinvasive E. coli
-Gram-negative
-Rod-like
-Causes an epithelial invasion of the large bowl leading to inflammation and invasion of the epithelial mucosa (bacillary dysentery)
-Foodborne
-Primary pathogens
Virulence Factors:
-Enterotoxin producer (Shigella)
-Shiga toxin via phage (Enteroinvasive)
Describe enterohemorrhagic E. coli
-Gram-negative
-Rod-like
-Produces Shiga toxin to damage the lining of the intestinal wall (infection in the GI tract)
-Foodborne
-Primary pathogen
Virulence Factors:
-Shiga toxin
Describe Giardia lamblia
-Protozoan
-Enters the host as a cyst, gets dissolved by pH, and trophozoite attaches to the intestinal wall and cause diarrhea (infection in GI tract)
-Spread by contaminated water or direct contact
-Opportunistic pathogens
Virulence Factors:
-Cysteine proteases
Describe Entamoeba histolytica
-Protozoan
-Causes amoebic dysentery which invasion into the colon wall (infection in the GI tract)
-Foodborne
Describe Treponema pallidum
-Gram-negative
-Spirochete
-Human STD bacterium spreads in the body
-Requires direct contact for the spread
-Primary pathogen
Virulence Factors:
-Burrows in tissues
What are the stages of syphilis? What is congenital syphilis?
Stages:
-Primary Syphilis: chancres at reservoir; full of spirochetes (if untreated, it enters the primary latent stage)
-Secondary Syphilis: generalized rash
-Tertiary Syphilis: after several years, effects on heart and CNS
Congenital Syphilis: pregnant mother affects the fetus with congenital defects (transfer of infection)
Describe Neisseria meningitides
-Gram-negative
-Diplococci
-Causes a throat infection, and rash leading to bacteremia (crosses blood-brain barrier into the cerebrospinal fluid)
-Spread by airborne droplets (human)
-Opportunistic pathogen
Virulence Factors:
-Opa protein (entry into cell)
-Endotoxin; capsule; pili
-Phase variation
Describe Clostridium botulinum
-Gram-positive
-Endospore
-Causes flaccid paralysis due to the toxin interfering with neural transmission by blocking the release of acetylcholine (infection at CNS)
-Foodborne
-Primary pathogens
Virulence Factors:
-Toxin spores
Describe Clostridium tetani
-Gram-positive
-Rod-like
-Causes tetanus by causing nerve impulses to go unchecked (spastic paralysis) due to the toxin blocking the release of GABA inhibitory transmitter (infection at CNS)
-Spread by soil
-Primary pathogens
Virulence Factors:
-Toxin
Describe Listeria monocytogenes
-Gram-positive
-Rod-like
-Causes listeriosis by producing invasins allowing penetrating of the host cells to induce phagocytosis
-Also causes polymerization of host “actin rockets” to propel cells affecting the GI tract
-Foodborne illness
-Opportunistic pathogens
Virulence Factors:
-Invasins
-Propel cells
-Grows at low temperature
Describe Rabies virus (include the two types and negri bodies)
A virus (ssRNA) caused by an animal bite leads to fatal encephalitis by the virus multiplying in skeletal muscles and then brain cells (CNS infection). There are two forms of the disease:
-Furious rabies: animals are restless then highly excitable
-Paralytic rabies: animals seem unaware of their surroundings (delayed neuroinvasion then symptoms appear causing the disease to be fatal)
Negri bodies: viral inclusions present in affected nerve cells
What is septicemia? What is bacteremia?
Septicemia is an infection caused by the multiplication of bacteria in the bloodstream (produces toxins)
Bacteremia is the simple presence of bacteria in the bloodstream
What is the difference between primary and secondary pathogens?
Primary pathogens can cause disease in a host regardless of the host’s immune system
Secondary pathogens are also known as opportunistic pathogens where it can only cause disease in situations that compromise the host’s immune system
What are most gastrointestinal tract infections caused by? What are some features of general gastrointestinal infections?
Most gastroenteritis is caused by rotaviruses (norovirus)
Inflammation of GI tract is due to viral/bacteria; growth, toxin production, or results in loss of water and electrolytes
