Identification of ID Processes Flashcards
Name the Links of the Chain of Infection
- Causative agent
- Reservoir
- Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
Name components of pathogenicty
- Virulence
a. Ability to survive in the environment during transit
between hosts
b. Effective mechanism for transmission to new host
c. Ability to attach to the structure it will infect
d. Mechanism for proliferation
e. Invasion and dissemination - Bacterial toxins
a. Exotoxins
b. Endotoxins
What are Exotoxins?
Enterotoxins are secreted by bacteria and proteins:
- commonly secreted by gram positive bacteria
- more susceptible to heat inactivation, but variable
- neutralized by specific antibody
- may possess enzymatic activity
Clinical Examples
- MRSA
- C. difficile
What are Endotoxins?
Endotoxins are complexes of bacterial proteins, lipids, and polysaccharides:
- surface component of gram negative bacteria
- not destroyed by boiling or autoclaving
- partially neutralized antibodies
- produce physiologic changes by interacting with
host systems to set off cascades of responses
- fever
- swelling
- vascular leaking
- pain
- shock
Clinical Examples
- Cholera
T-Lymphocytes
- Major players in cell-mediated immunity
- Produced in thymus
- Mature T cells stored in secondary lymphoid organs
- lymph nodes
- spleen
- tonsils
- appendix
- Peyer patches in small intestine
- Circulate in the bloodstream and lymphatic system
- After 1st encounter with infected or abnormal
cells, T cells are activated and go search for those
particular cells
What do Cytotoxic T cells do?
Destroy virally infected cells and tumor cells
- also known as CD8+T cells
What do Memory T cells do?
Subset of antigen specific T cells that persist long term after an infection is resolved.
- provide immune system with “memory” against past
infections
- also known as CD4+ or CD8+
What do Natural Killer T cells do?
Produce cytokines releasing cytolytic/cell killing molecules.
Able to recognize and eliminate some tumor cells and cells infected with herpes viruses.
** Different from NTK cells of the innate immune system
What do Regulatory T cells do?
Made up of 2 classes CD4+Tneg cells
- Naturally occurring Tneg cells
- Adaptive Tneg cells
Produce substances that help end the immune response
- shut down T cell-mediated immunity
- suppress auto-reactive T cells that escape the
process of negative selection in the thymus
What do Helper T cells do?
Assist other WBCs in immunologic processes, including:
- maturation of B cells into plasma cells and memory B
cells
- activation of cytotoxic T cells and macrophages
- activated Th cells divide rapidly and release
cytokines that regulate or assist in the active immune
response
- can differentiate into one of several subtypes
- also known as CD4+ T cells
Anthrax
Etiology:
- Bacillus anthracis
- Spore-forming gram positive rod
Source:
- Anthrax naturally occur in soil and commonly affect
domestic and wild animals around the world.
- Domestic and wild animals such as cattle, sheep,
goats, antelope, and deer can become infected when
they breathe in or ingest spores in contaminated soil,
plants, or water. In areas where domestic animals
have had anthrax in the past, routine vaccination can
help prevent outbreaks.
- Most commonly found in agricultural regions of
Central and South America, sub-Saharan Africa,
central and southwestern Asia, southern and eastern
Europe, and the Caribbean.
Transmission:
- Not contagious from person to person
- Occupational skin contact with infected animals or
animal products; more rarely through inhalation or
ingestion
- Inhalation of spores results from risky industrial
processes, such as processing wool, bones, or
tanning of hides where spores are present.
- Considered likely biological warfare agent
Incubation Period
- a couple of hours to 7 days, mostly within 48 hours
Symptoms:
- Cutaneous anthrax
- Group of small blisters or bumps that may itch
- Swelling can occur around the sore
- A painless skin sore (ulcer) with a black center that
appears after the small blisters or bumps
- Most often the sore will be on the face, neck,
arms, or hands
- Inhalation anthrax
- Fever and chills
- Chest Discomfort
- Shortness of breath
- Confusion or dizziness
- Cough
- Nausea, vomiting, or stomach pains
- Headache
- Sweats (often drenching)
- Extreme tiredness
- Body aches
- Gastrointestinal antrhax
- Fever and chills
- Swelling of neck or neck glands
- Sore throat
- Painful swallowing
- Hoarseness
- Nausea and vomiting, especially bloody vomiting
- Diarrhea or bloody diarrhea
- Headache
- Fainting
- Flushing (red face) and red eyes
- Stomach pain
- Swelling of abdomen (stomach)
Diagnostic Testing:
- Measure antibodies or toxin in blood
- Test directly by smear or culture for Bacillus anthracis
in a sample of:
- blood
- skin lesion swab
- spinal fluid
- respiratory secretions
- Smears stained with polychrome methylene blue
- Samples must be taken before the patient begins
taking antibiotics for treatment.
- Chest XRAY or CT, if inhalation anthrax suspected
- confirm if the patient has mediastinal widening or
pleural effusion, which are X-ray findings typically
seen in patients with inhalation anthrax.
Isolation Precautions:
- Standard precautions, for patients with cutaneous
anthrax, unless uncontained drainage, then Contact
precautions
Treatment:
- Post-exposure prophylaxis
- Penicillin
- ciprofloxacin
- tetracycline
- erythromycin
- chloramphenicol
Prevention & Control:
- Vaccine available, but only indicated for certain
groups of at-risk adults
- Vaccinate animals annually in the US in areas where
animals have had anthrax in the past.
Case Fatality:
- 5-20% of anthrax cases are fatal
Arthropod-Borne Arborviral Diseases
Etiology:
- Togaviridae
- Eastern equine encephalomyelitis
- Mucambo
- Venezuelan equine encephalomyelitis
- Western equine encephalomyelitis
- Flavivridae
- Dengue
- St. Louis encephalitis
- West Nile
- Yellow fever
- Bunyaviridae
- Anopheles group A and C
- Bunyamwera group
- Bwamba group
- California group [California encephalitis]
- Guama group,
- Mapputta group
- Simbu gorup
- Phlebovirus [sand fly fever group]
- Nairovirus
- Reoviridae
- Changuinola group
- Kemerovo group
- Colorado tick fever
- Rhabdoviridae
- Vesicular stomatitis goup
- LeDantec group
- Orthomyxoviridae
- Dhori
- Thogoto
Source:
- Viruses are maintained in zoonotic cycles
- Humans usually an unimportant host in maintaining
cycle
- Only in a few cases do humans serve as the principle
source of virus amplification and vector infection
- Dengue fever
- Yellow fever
Transmission:
- Human infection is ususally incidental to blood
feeding by an infected arthropod vector
- Most viruses transmitted by mosquitoes, the rest by
ticks, sand flies, or biting midges
Incubation Period:
- 3 to 15 days, depends on specific virus
Symptoms:
- Fever
- Rash
- Encephalitis
- Arthritis
- In rare cases, hemorrhagic fever, whether internal or
external as evidenced by
- Capillary leakage [plasma leak syndrome]
- Shock
- Liver damage [most severe in Yellow fever]
- High case-fatality rates
Diagnostic Testing:
- Preliminary diagnosis is often based on the patient’s
clinical features, places and dates of travel (if patient
is from a non-endemic country or area), activities, and
epidemiologic history of the location where infection
occurred.
- Testing of serum or cerebrospinal fluid (CSF) for
serological titers for IgM and IgG, complement
fixation (CF) haemaglutination inhibition (HI), and
fluorescent antibody (FA) or ELISA
Isolation Precautions:
- Contact precautions, except for Dengue or Yellow
fever
- Special care for all blood and body fluids for
hemorrhagic fevers
- Avoid splashes or aerosol spray of contaminated
fluids
Treatment:
- Supportive treatment
- IV ribavirin and convalescent plasma have been used
for viral hemorrhagic fevers
- Fresh plasma, fibrinogen, and platelet concentration
is used to treat severe hemorrhage
- INF approved for treatment of West Nile
Prevention & Control:
- Vector control measures [e.g., mosquitoes] for
Dengue and Yellow fever
- Avoid mosquito bites
- Use netting or mosquito screens
- Use insecticides
- Reduce standing water where females can lay eggs
- Human vaccine available for Yellow Fever
- Animal vaccines for other arboviruses
Case Fatality:
- 40 to 50% of Dengue hemorrhagic fever or shock syndrome cases are fatal if untreated or mistreated
- 20 to 50% of Yellow fever cases are fatal
- Overall fatality rate is below 5%
- In other arboviral diseases, the fatality rate ranges
from 0.3 to 60%, with Japanese encephalitis, Murray
Valley fever, and Eastern equine encephalomyelitis
among the highest
Aspergillosis
Etiology:
- Aspergillus fumigatus, A. flavus, and A. niger
- Fungal infection
Source:
- Common fungus (mold) that lives indoors
and outdoors
Transmission:
- Inhalation of mold spores
Incubation Period:
- A few days to some weeks
Symptoms:
- The symptoms of allergic bronchopulmonary
aspergillosis (ABPA) are similar to asthma symptoms,
including:
- Wheezing
- Shortness of breath
- Cough
- Fever (in rare cases)
- Symptoms of allergic Aspergillus sinusitis include:
- Stuffiness
- Runny nose
- Headache
- Reduced ability to smell
- Symptoms of an aspergilloma (“fungus ball”) include:
- Cough
- Hemoptysis
- Shortness of breath
- Symptoms of chronic pulmonary aspergillosis include:
- Weight loss
- Cough
- Hemoptysis
- Fatigue
- Shortness of breath
Diagnostic Testing:
- Intradermal or scratch tests, which results in
wheal/flare responses
- Eosinophilia
- Serum precipitating antibodies against Aspergillus
- Elevated serum concentrations of IgE
- Endobronchial culture
- Sputum culture
- Culture of expectorated plugs of hyphae
- Serum precipitins to antigens of Aspergillus spp.
- Fungus balls in the lungs see on CXR or CCT
Isolation Precautions:
- Standard
Treatment:
- Coritcosteroid suppression therapy
- Surgical resection
- Amphotericin B (Fungizone)
- Itraconazole (for slowly progressing cases)
- Discontinuation/reduction in immunosuppressive
therapy
Prevention & Control:
-
Case Fatality:
-
Botulism
Etiology:
- Clostridium botulinum
- Bacterial spore infection
- produces toxins that attack the nervous system
Source:
- C. botulinum Spores found widely in nature. Under
certain conditions spores can grow and produce
toxins:
- Low-oxygen or no oxygen (anaerobic) environment
- Low acid
- Low sugar
- Low salt
- A certain temperature range
- A certain amount of water
Transmission:
- 3 types
- Foodborne - Ingesting food contaminated by toxin
- Wounds - contamination by organism in anaerobic
conditions
- Infant - most common type - ingestion of organism
and subsequent toxin production in the gut -
generally affects infants less than 1 year of age.
Incubation Period:
- 12 to 36 hours up to several days
Symptoms:
- Adult Symptoms
- Double vision
- Blurred vision
- Drooping eyelids
- Slurred speech
- Difficulty swallowing
- Difficulty breathing
- A thick-feeling tongue
- Dry mouth
- Muscle weakness
- Acute bilateral cranial nerve impairment
- Descending weakness
- Paralysis
- Infant Symptoms
- Lethargy
- Listlessness
- Poor feeding
- Ptosis
- Difficulty in swallowing
- Loss of head control
- Hypotonia
- Floppy baby
- Respiratory insufficiency
- Arrest
Diagnostic Testing:
- Presence of botulinum toxin in stool, serum and/or
gastric secretions or wound culture
Isolation Precautions:
- Standard
Treatment:
- IV administration of trivalent botulinum antitoxin
- Respiratory support
- Wound debridement
- Appropriate antibiotics (e.g. penicillin)
- Infant treatment
- Antitoxin not used due to risk for anaphylaxis
- Antibiotics do not improve disease course, and
aminoglycosides contra indicated as they may have
synergistic neuromuscular blockade effect
- Respiratory support
Prevention & Control:
- Do not feed infants less than 1 year of age honey
Case Fatality:
- Foodborne 5-10%
- Infant < 1%
- Infant botulism may account for 5% of SIDS cases
Brucellosis
Etiology:
- Brucella abortus, B. melitensis, B. Suis, and B. canis
- Bacterial infection
Source:
- Brucella can be found worldwide in infected domestic
and wild animal populations.
Transmission:
- 3 types
- Foodborne - Ingesting food contaminated by
brucella, such as unpasturized/raw dairy products.
- Inhalation of bacteria - usually in a laboratory setting.
- Wounds - contamination by organism through
contact with infected animals.
Incubation Period:
- 5 to 60 days; most common being 1 to 2 months.
Symptoms:
- Initial symptoms
- Fever
- Malaise
- Sweats
- Anorexia
- Headache
- Pain in muscles, joints, and/or back
- Fatigue
- Ongoing and persistent symptoms
- Recurrent fevers
- Arthritis
- Osteoarticular (joint) complications (20-60% of
cases)
- Swelling of testicles and scrotum
- Orchitis and epididymitis (2-20% of cases)
- Swelling of the heart (endocarditis)
- Neurologic symptoms (in 50% of cases)
- Chronic fatigue
- Depression
- Swelling of liver and/or spleen
Diagnostic Testing:
- Presence of bacteria in blood, bone marrow, or other
body fluids. Blood test to detect antibodies also
available.
Isolation Precautions:
- Contact with drainage and secretions
Treatment:
- Combination antibiotic therapy with rifampin or
streptomycin and doxycycline for 6 weeks
- Tetracycline (avoid in children) and bactrim effective,
but relapse common, ~ 30% of cases.
- Relapses occur in 5% of cases and should be
retreated with original regimen.
Prevention & Control:
- Avoid undercooked meat
- Avoid raw/unpasturized dairy products
- Wear PPE when handling raw meat tissues
Case Fatality:
- death in < 2% of cases, but may occur from
endocarditis secondary to B. melitensis infection.
