Chapter 4- Overview of infectious diseases Flashcards
Who developed the germ theory of disease in the 19th century?
louis Pasteur and Robert Koch.
Dr. Koch established which 4 criteria, known as Koch’s postulates- used to determine if a disease is attributatble to a particular organism?
- same pathogen must be found in all diseased individuals with the same sxs
- pathogen must be isolated from the individual with the disease and grown in a culture
- same disease must be induced in an experimental animal by transfer of cultured pathogen
- after the disease develops the same pathogen must be isolated from the experimental animal.
What was the first primitive vaccine?
in 1976 used to prevent smallpox.
The habitat in which infective agents live and multiply is called a reservoir. There are 4 types, name them
- symptomatic individuals
- carriers
- animals
- water, food, soil, air, fomites
When does infection occur?
when there is entry and multiplication of a microorganism or parasite in the body of a host.
Define “vector”
an insect that injects a microbe through a bite, but can refer to any creature that transports the infective organism to the host.
Microbes must do what to the host in order for a disease to occur?
invade, infect and disrupt the cells of the host.
What methods are used to identify organisms causing infection?
- direct detection methods
- Culture and sensitivity
- immunodiagposis
- Nucleic acid probes
What are direct detection methods?
use the microscope to view microbe obtained in a tissue, orexcreta sample.
- stains used to see organisms. gram stain (bacteria) and acid-fast stain (mycobacterium)
What is culture and sensitivity detection?
cultivating viruses and microbes in order to obtain enough of the organism to identify it.
- uses medium of living cells cultivated by single layer of living mammalian cels.
- this method also used to test efficacy of specifed antibioics
What is immunodiagposis?
testing the presence of antibodies, the in serum, that are produced by the immune system in reaction to an infection.
- Hep testing, H pylori testing.
what is Nucleic acid probes ?
theory: every species has unique gene sequencing.
identify and direct detection of the infective organism in clinical specimens.
- monitory response to therapy in some diseases (Hep C/HIV)
- PCR used to amplify a single DNA molecule into many molecules.
Name 4 infectious disease-causing organism
bacteria
viruses
fungi
parasites
What is a bacteria?
single cell organisms. Good bacteria (form symbiotic relationships) and bad bacteria.
Classification of disease-causing bacteria is based on structural and physiological characteristics. Name them (4)
- Cocci: spherical
- bacilli: rod shape
- spirochetes: spiral
- vibrios: comma shaped
What are the prefixes used in grouped bacteria to describe their structural characteristics
- diplo (paired)
- strepto (chains)
- staphylo (clusters)
Bacteria can also be classified by their dye reaction to staining techniques. Explain.
gram stains form due to a reaction of the cell wall of the bacterium with the stain.
If the wall absorbs the stain well and is purple they’re called gram-possitive bacteria.
If not well absorbed and are pink coloured they are called gram negative.
- The resulting stain classification affects which abx will work better on the bacteria.
Bacteria can also be classified by their need for oxygen to survive. Define the 3 types.
anaerobic bacteria: cant survive in the presence of oxygen
Aerobic bacteria must have oxygen to survide.
facultative anaerobic: live with or without oxygen
What are antibiotics?
substances produced by microorganisms that kill other microorganisms.
- natural byproducts of cell metabolism.
What is penicillin?
First production and isolation occurred in 1940.
works against gram +ve bacteria
such as staphylococci and streptococci- two types of bacteria that large a large percentage of human infections.
What are common virus characteristics?
- non-living d/t no cellular structure
- fully developed virus has a protein coat surrounding a nucleic acid- this protects and facilitates host transfers.
- some have an envelope of lipids, proteins and carbs around their protein coats. They’re called enveloped viruses otherwise its considered a naked virus.
- require metabolic machinery of infected cell to reproduce. (uses host to copy itself)
- contain either DNA or RNA, but never both.
How are viruses categorized?
by the type of nucleic acid they contain
- DNA ex: herpes, smallpox, and papovavirus
- RNA ex: HIV, hepatitis C, rabies.
Why are there fewer drugs available to treat viruses than bacteria?
- hard to find drug that affects virus without affecting the host cells. viruses use the biochemical pathways of the host to reproduce.
- delay/difficulty in diagnosis. Usually identified once the virus has reach latter phases of the disease.
- many viral illnesses are relatively benign and self-limited.
What is fungi?
yeast and molds
they’re aerobic and require organic nutrients to live.
100,000 types, and 100 are infectious to humans
What saprophytes?
fungi that live on decaying organic matter.
What fungi are quite difficult to treat? why?
systemic fungal infections.
anti-fungal drugs have serious AE.
Give an example of a fungi treatment?
Amphotercin B,
Axole compounds can be used in some situations and are less toxic.
What are parasites?
organism that cause disease in humans but are not bacteria, viruses or fungi. (everything else)
Need to invade a human body to complete their life cycle.
No great treatments
What are the two basic types of parasites causing disease?
- protozoa - single cell creatures that multiply within a host.
- helminths (worms) - multicellular creatures. 3 types: roundworms, tapeworms, and flukes or flatworms.
What is a vaccination?
How many kinds are there? What are they called?
IT is a preventative treatment.
Typically it is a killed or weakened part of a microbe (antigen) that causes a specific disease, and is introduced into the body by injection prior to being infected. The presence of the antigen stimulates an immune response in the body.
2 types:
live-attenuated - microbe is alive but weak
inactivated- microbe is killed.
True or False
most viral diseases require live-attenuated vaccines and vaste majority of bacterial illness are prevented with inactivated vaccines.
true.
What are the two kinds of combination vaccines?
- DTaP (or DPT)- diphtheria/tetanus/pertusis
2. MMR- measles/mumps/rubella
What are typical routine vaccinations for the general population?
- polio
- varicella
- hepatitis A and B.
- rotavirus,
- Hib (meningitis, epiglottis, skin disease)
- meningococcal and pneymococcal bacterial
what are the two large reasons for the decline in vaccinations in children?
concerns about safety of vaccines.
There is incomplete understanding about the seriousness of the disease they prevent.
Poor education
What is influenza?
acute respiratory viral infection.
sxs: fever, malaise, muscle and joint pain and headaches.
recovery 5-7 days. high risk in those >65 years old, and any with weakened immune systems.
tx: supportive. antiviral medications are available by px and will shorten duration of sxs by 50% if given within 48 hours.
virus is endemic (present in world at all times) and mutates easily.
RNA virus proteins (hemagglutinin and neuraminindase) protect its surgace.
3 types: A (humans and birds, pigs, cats, horses, seals), B, and C (humans)
Virus has the ability to mutate and jump species making it deadly.
What were the 3 pandermics in the 20th centery?
- H1N1 virus in 1918 killed 50-100 million
- 1957 Asian flu pandemic H2N2 virus, 2 million
- 1968 Hong kong flu pandemic H3N2 virus, 1 million.
What are the 2 avian flu viruses being monitored right now?
- H5N1 avian virus- killing fowl since 2003, only transfered from bird to human right now.
- H7N9- 2013, no evidence of person to person
What are nosocomial infections?
infections acquired during hospitalization.
most common: UTI followed by infections of surgical wounds, blood stream infection, and pneumonia.
Hospital microbes are more resistant to abx, and difficult to treat.
spread to patients by hospital workers with poor hygiene, indwelling medical devices, and surgical drains.
causative microbes often part of normal body flora, invades tissues where they do not normally exist.
What is Sepsis?
present of two of the follwing manifestations in the presence of an infection:
- fever
- tachycardia
- tachypnea
- elevated WBC
Major sepsis includes dysfunction of major organs.
Septic shock is severe sepsis with hypotension and perfusion abnormalities.
survivable with tx.
What is penumonia?
inflammation of the lungs caused by a microbe.
caused by variety of organisms (Bacteria is the majority cause, steptococcus most common in community, and E coli in nosocomial penumonies).
tx: abx until causative organism is identified via culture or serologic confirmation of abx.
sxs: fever, cough, shaking chills, dyspnea, cough. weight loss, fatigue, and night sweats.
What are the factors that can predispose an individual to contract penumonia?
- pre-existinc respiratory tract infection
- SM
- heart failure
- alcoholism
- COPD
- debility
- immunosuppressive disorders.
What is encephalitis?
infection of brain tissue, involving cortext of the brain and sometimes meninges.
- caused by all organism but usually viral (hepes simplex virus causes most common type of sporadiuc encephalitis)
- tx depends on cause- serial spinal taps used to identify the agent. mosquito-born forms can be fatal no matter what
residuals: Permanent neurological complications, coma, seizures, ^ intracraneal pressure, herniation of brain,
What is meningitis?
infection of the meninges (membrane surrounding the brain) without involvement of underlying brain tissues.
viral are more common and lower mortality than bacterial (resulting brain herniation and swelling).
abx are the usual tx for all types.
viral tends to me mild and referred to as Aseptic - can progress to coma. Sequelae of viral meningitis rate.
residuals: headaches, dizziness, hearing loss.
tx: supportive, 1 antiviral drugs (zovirax)
What is Mononucleosis?
viral infection caused by EBV and characterized by fever, soar throat, lymphadenopathy, and atypical lymphocytosis. Can be caused by CMV, and Toxoplasma gondii.
Spread: Saliva, 95% of population infected by age 40.
sxs: pharyngitis, exudate, high fever, cervical lymphadenopathy, and splenomegaly.
resolves in 3-6 weeks, fatigue for months.
tx: supportive.
complications: anemia, thrombocytopenia, encephalitis, pericarditis, splenic rupture.
What is Kawasaki Disease?
febrile acute syndrome that affects infants and young children.
infections agent has not been identified.
sxs: vasculitis- causes heart disease in 1/4 untx’ed children, can cause aneurysm, and arterial narrowing- which can reverse in adulthood.
self-limiting, and full recovery (usually).
complications in those with residual cardiac involvement: impaired LVF, mitral regurg, stiffening of arteries.
tx: high-dose intravenous gamma globulin and high-dose aspirin.
What is the one of the most deadliest pandemics in human history?
HIV
transmitted: sex, blood, fluids.
affects CD4 T-lymphocytes, replicate in lymph nodes and enter blood stream. immune system cannot clear virus and it becomes a chronic infection.
median period before sxs is 10 years.
What were the early findings/sxs in HIV disease?
acute HIV syndrome- 3-6 weeks after infection with sxs resembling mononucleosis
Generalized lymphadenopathy- earliest sxs after acute HIC syndromes
AIDS is the final stage of the HIV disease. its defined as HIV disease plus one of what two caracteristics?
- a CD4 count under 200 cells/uL (normal is 800)
2. presence of one of about 23 specific conditions (opportunistic infections, cancers, other conditions)
Bacterial infections are the leading cause of death in AIDS. What are the more common opportunistic infections?
- pneumocystis carinni pneumonia (PCP) - most common
- Toxoplasmosis - mass lesions + seizures
- mycobacterium avium complex
- tuberculosis
- streptococcus pneumonia and haemophilus influence infections
- candidiasis- seen in almost everyone with AIDS
- CMV infections
- Herpes simplex.
Which neoplasm often occur with AIDS?
Kaposi’s sarcoma
Lymphomas
How long does it take for antibodies to HIV to start appearing in the blood stream?
2 weeks- 6months
all individuals infected will test positive by month 6, but some may test -ve until this time.
What is the standard initial HIV serology test?
ELISA
inexpensive, few false -ve’s.
Westernblot serology is the confirmation test after a +ve or indetermined ELISA test.
How is the severity of the disease measured?
via: RNA level which is the number of copies in the blood.
^^^ RNA level = poor prognosis
What is the treatment for AIDS?
right now Antiretroviral drug therapy (ART). 6 classes exist- to treat disabling proteins to interfere with the ability of the virus to enter the CD4 cell.
Tx: is a minimum of 3 drugs from at least 2 out of 6 classes. > these reduce viral load. and by suppressing HIV replication they allow CD4 cell count to rise.
What is lyme disease?
recurrent multi-system disorder caused by trick-transmitted spirochete borrelia burgdorferi.
3 stages if not tx’ed:
1. infection at the site of the bite. Bulls eye appearance and disappears in 2 weeks.
2. infection spread, joint and muscle pain, skin lesions, cardiac abnormalities, and neurological abnormalities
3. 2-3 months later, chronic arthritis, encephalopathy, neurological complications.
tx: with abx, early tx = better prognosis, recovery in majority of cases.
What is the West Nile virus?
1937, seen in North America in 1999.
spread: by mosquitoes and wild bird populations.
80% show no sxs, 20% have mild sxs (fever, headaches, rash) less than 1% develop CNS sxs.
serious form residuals: neurological sequelae.
no tx.
What is Severe Acute Respiratory Syndrome? (SARS)
First new infectious disease of 21st century, caused by new strain of coronavirus via bats.
Spread via: saliva/cough
causes pneumonia in most cases and develops to respiratory failure.
no tx, and care is primarily supportive. Mortality is 10-15%, most deaths occurring in impaired pts.
No cases since 2003.
What is the Middle Eastern Respiratory Syndrome? (MERS)
cause: novel coronavirus via camels. 2012
sxs: severe acute respiratory illness, fever, SOB, cough.
tx: supportive, no antiviral drugs.
death rate 50%- worse in impaired pt and old people
Where: Arabian peninsula.
spread: close contact
What is Histoplasmosis?
infection caused by fungus histoplasma capsulatum- moist soil with bird and bat droppings.
causes: granulomas reaction, CXR looks like tuberculosis.
residuals: Round, calcified mass of scar tissue (histoplasmoma)
acute disease more common- and mild.
progressive disease- fatale, most common in smokers and young/immunocompromised pts.
dx: culturing fungi from blood or sputum.
tx: mild=none, severe/ anti-fungeal medication
What is Poliomyelitis?
1840 viral infection of the CNS possibly causing paralysis.
spread: Fecal-oral route, from intestine to lymph then blood, and sometimes CNS.
Vaccine in 1950 decreased incidence.
sxs: Asxs (majority) - to sxs that mimic meningitis, paralytic form that causes respiratory paralysis, pulmonary failure and death
residuals: weakness, fatigue pain 20-40 years (thought to be caused by nerve damage at time of infection).
What is tuberculosis?
acute or chronic infection caused by Mycobacterium tuberculosis.
- lungs (most common), other organs
- transmitted via cough/sneeze.
- immune response contains bacteria in granulomatous lesions (tubercles). this response is reflected by a +ve PPD test. If the bacteria reactivates it results in post-primary TB which is the most common form.
- Active TB dx when AFB are found then confirmed via culture. - can take 8 weeks. usually pts’ are tx’ed right away.
Define pros-primary TB
can develop in any organ or structure of the body.
tiny lesions resembling millet seeds occur- this called military TB
- TB is major opportunistic infection for those with AIDS
What is the TB test
common test PPD- skin test used to screen body’s immune response to TB infections.
usually its positive in both TB infection and disease.
How is TB treated?
- most cases are curable with anti-tuberculosis drugs. many drugs for 6 months, or more.. Pts are monitored. 5 first line drugs: 1. INH 2. rinfampin 3. pyraxinamide 4. ethambutol 5. steptomycin second line drugs used when organism is resistant, or there are AE.
What is Hemorrhagic fevers?
group of diseases caused by RNA viruses.
classified as zoonoses (animals to humans).
cause severe fetal infections to humans by affecting their vascular sxs, increased permeability of vessels leads to leakage of plasma into tissues.»_space; hypotension and shock.
- DIC can occur
What is Disseminated Intravascular Coagulation?
DIC can also occur in some of the hemorrhagic fevers, when blood clotting mechanism is activated in the body instead of at the site of injury.
This usually forms clots and hemorrhages
What is Hantaviurus pulmonary syndrome?
1993– virus infecting deer mice and passed to humans via their droppings.
onset looks like influenza, but pulmonary edema rapidly develops and then respiratory failur.
no tx drug therefore only supportive, and O2 supply.
mortality 40%
What is Ebola and Marburg Virus diseases
RNA viruses arising from an animal source
lethal disease in humans, spread via blood and body fluids. Affects all organs, severe involvement leads to vascular failure, haemorrhages into the skin, mucous membranes, viscera and GI tract lining.
Mortality 90%
recent outbreak in 2014- in West Africa.
tx: supportive. efforts for a vaccine are ongoing.
What is Dengue?
acute viral infection that is endemic to the tropics.
spread: mosquitoes
sxs: Asxs but when are present fall into 3 patterns. Less serious flu-like illness where recovery is rule, and Dengue hemorrgic fever is most severe, and leads to shock - morality 5%. common in children <10 yo. sxs start with fever, headaches, abdo pain and vomiting followed by GI bleed and skin bleed. sxs associated with thrombocytopenia and hepatomagley.
tx: is symptomatic: bedrest, acetaminophen and codeine. may include fluid replacement and plasma/blood/plately transfusions.
What Schistosomiasis
parasite infection caused by blood flukes that live in fresh water.
3 species: Schistosoma mansoni, S. Japonicum cause hepatic granulomas and fibrosis. and S. Haematobium affect the bladder.
Flukes penetrate skin, migrate to veins in the intestine and bladder causing chronic disease. mortality is low, but morbidity high.
after initial infection, pts can develop acute form called kataya fever.
chronic form causes granulomas reactions and fibrosis in various organs.
dx: microscopic exam of stool or urine.
tx: praxiquantel or oxamniquine.
What is Trypanosomiasis (sleeping sickness)
infection caused by the protozoan parasite trypanosoma brucei, transmitted by the tstse fly. If untx’ed leads to progressive neurological impairment and death.
dx: by finding the parasite in the chancre, lymph nodes, blood or spinal fluid.
tx: with suramin, eflornithine, pentamidine, and organic arsenicals, are effective but often have sig AE.
What Zika?
isolated from monkeys and mosquitoes in Zika forest.
spreading d/t lack of any immunity to Zika and the fact that the mosquitoes spreading the virus. (Yellow fever’s cousin)
its transmitted through sexual contact with infected individuals.
dx: travel history, sxs and test results: Urine or blood.
sxs: mild, fever, headache, rash and conjunctivitis.
tx: aimed at relieving the sxs and usually anti-pyretics and analgesics. 80% infected are not symptomatic.
usually mild, but danger to pregnant females.
What 3 trends related to resurgent infectious diseases that have surfaced in recent years?
- many microbes developed resistance to abx
- deadly new disease have appeared in the last few decades
- new infection agent have been discovered. Folded bits or protein called prions now are thought to cause the spongiform encephalopathies.
- bioterrorism
What are the 3 possible outcomes of an infection?
- infection overwhelms the individual and death results
- immune system with or without the help of tx, eradicates the infection.
- infectious agent reaches a state of equilibrium with the host and a chronic or latent infection results.
Most infection diseases do not impact UW since once recovery has occurred there is no negative impact on mortality or morbidity. Need to review Tx, and recovery. chronic? acute? residuals? Travel?
