Identification of ID Processes Flashcards
(19 cards)
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.
Candidiasis
Etiology:
- Candida albicans, C. tropicalis, and c. glabrata
- Fungal infection
Source:
- Candida can be normal flora of skin and digestive
tract
Transmission:
- Overgrowth in the oral, esophageal, or vaginal tissue
- Risk factors include:
- Dentures
- Diabetes
- Cancer
- HIV/AIDs
- Antibiotics/Corticosteroids
- Medications that cause dry mouth or have medical
conditions that cause dry mouth
- Smoke
- Pregnancy
- Hormonal contraceptives (for example, birth control
pills)
- Hematogenous dissemination from GI or IV catheters
Incubation Period:
- 2 to 5 days
Symptoms:
- Oral and esophageal symptoms
- White patches on the inner cheeks, tongue, roof of
the mouth, and throat.
- Redness or soreness
- Cottony feeling in the mouth
- Loss of taste
- Pain while eating or swallowing
- Cracking and redness at the corners of the mouth
- Vaginal symptoms
- Vaginal itching or soreness
- Pain during sexual intercourse
- Pain or discomfort when urinating
- Abnormal vaginal discharge
- Systemic infections
- Fever or chills that don’t improve after antibiotic
treatment for suspected bacterial infection
- Lesions of kidney, spleen, lungs, liver, eye,
meninges, brain, and natural cardiac or prosthetic
cardiac valves
Diagnostic Testing:
- Microscopy on pseudohyphae and/or yeast
- Culture
Isolation Precautions:
- Standard Precautions
Treatment:
- Topical nystatin
- Miconazole
- Clotrimazole
- Ketoconazole
- Fluconazole
- Butoconazole
- Terconazole
- Amphotericin B
- 5-fluorocytosine
Prevention & Control:
- Maintain good oral health
- Rinse mouth or brush teeth after using inhaled
corticosteroids
- Chlorhexidine mouthwash may help to prevent oral
candidiasis in people undergoing cancer treatment
Case Fatality:
- No information
Bartonellosis (Cat Scratch Disease, Trench Fever, & Carrion’s Disease)
Etiology:
- Bartonella henselae (Cat Scratch Disease)
- Afipia felis may also play a minor role in CSD
- B. quintana in immunocompromised (Trench Fever)
- B. bacilliformis (Carrion’s Disease)
- Bacterial infection
Source:
- B. henselae
- Cats that harbor infected fleas
- Ticks may carry some Bartonella spp., but no
convincing evidence that ticks can transmit to
humans.
- B. quintana
- Infected human body louse
- B. bacilliformis
- Infected sand fly
Transmission:
- Mainly transmitted by carriers (vectors), including
fleas, lice, or sandflies
- Risk factors include:
- Playing rough with cats, especially strays or kittens
- Handling cats with fleas
- Avoid exposure to human body lice
- Avoid sand fly bites
Incubation Period:
- 3 to 14 days from inoculation to primary lesion and 5
to 50 days from inoculation to lymphadenopathy.
Symptoms:
- Initial symptoms
- Bartonella henselae (Cat Scratch Disease)
- Low-grade fever may be present
- Enlarged, tender lymph nodes that develop 1–3
weeks after exposure.
- A papule or pustule at the inoculation site
- B. quintana in immunocompromised (Trench Fever)
- Fever (may present as a single bout of fever or
bouts of recurrent fever)
- Headache
- Rash
- Bone pain, mainly in the shins, neck, and back
- B. bacilliformi
- 2 distinct disease phases:
- Oroya fever (phase 1):
- Fever
- Headache
- Muscle aches
- Abdominal pain
- Severe anemia
- Verruga peruana (phase 2):
- Lesions appear under the skin as nodular
growths, then emerge from the skin as red-to-
purple vascular lesions that are prone to
ulceration and bleeding.
Diagnostic Testing:
- Bartonella henselae (Cat Scratch Disease)
- May be diagnosed presumptively in patients with
typical signs and symptoms and a compatible
exposure history.
- DNA may be detected by PCR or culture of lymph
node aspirates or blood, though sensitivity of these
methods is not optimal for blood samples.
- Serologic titer of antibody to Bartonella is
considered positive at > 1:64 IFA assay.
- B. henselae is a fastidious, slow-growing bacterium,
cultures should be held for a minimum of 21 days.
- B. quintana in immunocompromised (Trench Fever)
- Isolation from blood cultured on blood or chocolate
agar under 5% CO2.
- Microcolonies can be seen after 21 days of
incubation at 37°C
- Can also be diagnosed by serology
- B. bacilliformis
- Diagnosed via blood culture or direct observation of
the bacilli in peripheral blood smears during the
acute phase of infection (Oroya fever).
Isolation Precautions:
- Standard precautions
Treatment:
- Bartonella henselae (Cat Scratch Disease)
- Many cases resolve without treatment
- Azithromycin has been shown to decrease lymph
node volume more rapidly compared to no
treatment.
- A number of other antibiotics are effective against
Bartonella infections, including penicillins,
tetracyclines, cephalosporins, and aminoglycosides.
- Since aminoglycosides are bactericidal, they are
typically used as first-line treatment for Bartonella
infections other than CSD.
- Trench fever, Carrión’s disease, and endocarditis due
to Bartonella spp. are serious infections that require
antibiotic treatment. Health care providers should
consult with an expert in infectious diseases
regarding treatment options.
Prevention & Control:
- Wash hands carefully after handling cats
Case Fatality:
- No information
Chicken pox
Herpes Zoster-Varicella
Shingles
Etiology:
- Human herpesvirus 3 (Varicella-Zoster [VZ] virus)
- Viral Infection
Source:
- Infected individuals
- A person with varicella is contagious beginning 1 to
2 days before rash onset until all the chickenpox
lesions have crusted.
- Vaccinated people may develop lesions that do not
crust. These people are considered contagious until
no new lesions have appeared for 24 hours.
- People with breakthrough varicella (e.g. infection
with wild-type varicella-zoster virus (VZV) occurring
in a vaccinated person more than 42 days after
varicella vaccination) are also contagious.
Transmission:
- Virus can be spread from person to person by direct
contact, inhalation of aerosols from vesicular fluid of
skin lesions of acute varicella or zoster, and possibly
through infected respiratory secretions that also may
be aerosolized.
- Up to 90% of susceptible close contacts (e.g.
unvaccinated with no history of varciella infection)
are most likely to become infected after exposure to
varicella (chickepox).
- Risk for VZV transmission from herpes zoster
(shingles) was approximately 20% of the risk for
transmission from varicella.
Incubation Period:
- 10 to 21 days after exposure to the virus; average is 13-17 days.
Symptoms:
- Initial symptoms
- A mild prodrome of fever and malaise may occur 1 to
2 days before generalized, pruritic rash onset,
particularly in adults.
- In children, the pruritic rash is often the first sign of
disease.
- Rash usually appears first on the chest, back, and
face, then spreads over the entire body.
- Lesions progress rapidly from macular to papular
followed by vesicular for 3-4 days, then granular
scab
- Vesicles are monolocular and collapse on puncture (whereas smallpox lesions are multilocular and non-collapsing vesicles).
- Lesions may appear on scalp, axilla, mucous membranes of mouth and upper respiratory tract, and conjunctiva.
- May occur in areas of irritation, which may be unnoticed due to being less in number.
- The infection may be mild or severe.
-
- Ongoing and persistent symptoms
- May go on to develop shingles later in life.
Diagnostic Testing:
- Test for serum antibodies
- Viral DNA by PCR
- Examination by electron microscope
Isolation Precautions:
- Airborne and Contact
- Standard precautions for Zoster, unless disseminated, then Airborne and Contact.
- Maintain isolation for at least 5 days after eruption first appears, or until vesicles become dry.
- Personnel who have not had chicken pox should avoid contact.
Treatment:
- Susceptible contacts may be given VZIG within 96 hours of exposure.
- Vidarabine and acyclovir are effective in treating VZ infections.
- Acyclovir and famciclovir shorten the duration and symptoms of zoster.
Prevention & Control:
- Vaccination
- Chickenpox Airborne Precautions + Contact Precautions
Case Fatality:
- OVerall 2/100,000, but in adults 30/100,000.
- Cause of death in infants is sepsis or encephalitis. In adults, it is primary viral pneumonia.
Template
Etiology:
Source:
-
Transmission: - - Incubation Period: -
Symptoms:
- Initial symptoms
- Ongoing and persistent symptoms
Diagnostic Testing:
-
Isolation Precautions:
-
Treatment:
Prevention & Control:
Case Fatality:
-
