viral and bacterial infections Flashcards
what causes infectious diseases?
what is it the product of?
- microorganisms cause disorders which damage tissue or cause dysfunction
- product of interaction btwn agent and host
infectious disease is dependent upon… (5)
- intrinsic characteristics of agent
- mode of transmission
- unique characteristic of host
- host-agent relationship
- host responses to infection
characteristics of the agent (3)
interaction btwn agents and host…
what is disease a result of?
- interaction btwn agents and humans is cooperative and development of disease is the exception
- disease is the result of agent interference w/ function and integrity of host.
2 ways parasites can act and an example of each disease
certain parasites will produce disease (eg- myobacteria tuberculosis), others are facultative pathogens which can colonize, invade or both (eg candida albicans)
what is virulence? what is another name for virulence?
extent of interference of agent. a.k.a. pathogenicity
modes of transmission
horizontal (2)
vertical (2)
zoonotic (1)
- horiontal:
direct spread- exposure from sick individuals is characteristic of contagious disease (eg small and chicken pox, TBC.
indirect spread- exposure to contamindated water, food or soil (mycosis, histoplasmosis) - vertical:
prenatal (rubella)
perinatal (hep B) - zoontic transmission - animal to host (rabies, malaria)
characteristics of the host
-3 barriers to infection
- intact skin and mucosal surface and secretions
- phagocytotic cells at the site of entry
- immune system
when are host barriers effective? what happens when they are defective?
barriers or defense mechanisms are only effective when they are intact, if they are defective infectious agents will produce disease
just exposure to infectious agents is not necessarily sufficient, spread is determined by: (2)
- virulence of infectious agent
2. extent of host resistance
definitions of two host-agent relationships :
high virulence
low virulence
- high virulence- implies capability of agent to cause disease in normally resistant individuals
- low virulence- an agent which is only effective in host with low resistance (opportunistic infection)
pathogenicity factors-
dependent on 3 host-agents relationships…
2 characteristics of the agent
1 characteristics of the host
- ability to produce an infection and propagate w/i the host by overcoming host defenses
- agents ability to generate products that will result in tissue damage (ie toxins, lytic enzymes, etc)
- induction of host-cellular responses to the infectious agents can lead to tissue damage as well (hypersensitivity I- IV)
host responses to infection
(4 types of inflammation)
- exudative inflammation
- necrotizing inflammation
- chronic inflammation
- granulomatosis inflammation
viral infections characteristics (2)
capsid
latency definition
protein shell around virus
to propagate, each virus must do what?
- 4 stages of virus cycle
- attach to cell
- penetrate it
- un-coat
- replicate: DNA in nucleus and RNA in cytoplasm
how do viruses travel?
definition of viremia
- except for some respiratory viruses, virues probably travel via blood
- viremia- presence of virus in bloodstream
how do viruses cause disease?
how do viruses produce disease?
- viruses cause disease by killing the infected cells but in some cases disease can be produced w/o killing infected cells
- viruses produce disease by promoting the release of difference chemical mediators
viral infections- influenza
def
characterized by…
two distinct viruses that cause it…
- acute self-limited viral respiratory disease which is distributed worldwide and often occurs in widespread epidemics.
- characterized by fever, headache, myalgia, and prostration w/ bronchitis and bacterial pneumonia as common complications
- two distinct viruses cause the disease: influenza virus A and B- periodically undergo changes in antigenic composition making world population become newly susceptible to disease
viral infections- measles (rubeola) def incubation period -> first symptoms clinical signs immunity
- highly contagious disease caused by RNA measles virus occurring in young children
- incubation period of 10-21 days precedes prodrome with fever, cough, conjunctivitis and malaise
- clinical signs- blue-gray spots with red areola appear on buccal membranes and erithematosus macloapular rash spreading downwarrd from head -> face -> trunk and limbs lasting about 5 days
- recovery confers immunity and live vaccine is available (from Merck!!) :)
viral infections- rubella def clinical signs immunity congenital rubella
- mildly contagious viral (RNA) disease that usually affects children 5-15 yo
- clinical signs- mild- characterized by lymphadenopathy, maculopapular rash of duration 3-5d and conjunctivtis
- infection infers immunity
- congenital rubella is when fetus is infected during first trimester of gestation can be disastrous disease, causing fetal death, premature delivery and number of sever congenital defects
medical terminology:
macula
papular
pustule
macula- usually red rash, same level as skin
papular- red rash, popped up from skin
pustule- blister, papula with fluid in it
viral infections: Mumps def clinical signs complications is it epidemic?
- acute generalized infections with an RNA virus which occurs most frequently in school age children
- characterized by fever, malaise, and parotitis (swollen salivary glands and interstitium is infiltrated w/ lymphocytes)
- complications include meningitis, pancreatitis and in post-pubertal patients- orchitis (testis inflammation)
- epidemic disease, especially in closed communities, vaccine is available (from Merck!)
viral infections: rotavirus infection
def
signs
- RNA virus that spreads from person to person by oral-fecal route and usually infect young children (why we have to wash our hands!)
- produces vomiting, fever, abdominal pain and profuse watery diarrhea (5-8 days) that can lead to dehydration and death if untreated
viral infections: varicella (chicken pox)
def
characterized by-
what happens if its reactivated
what is the incubation period?
it is more serious in adults or children?
- contagious (respiratory route) viral disease caused by varicella-zoster virus (herpes)
- characterized by lesions beginning as macules, developing into vesicles, after which virus becomes latent
- reactivation in ganglion cells => herpes zoster (shingles)
- incubation period is 17-21 days followed by fever, malaise and rash
- relative benign in children but may be serious in adults
viral infections: herpes simplex caused by... characterized by... parts of body that can be affected mode of spread/ recurrence
- disease caused by infection with herpes simplex types I and II
- characterized by painful ulcerating vesicles 3-6mm in diameter developing around the lips (type I) and genitals (type II)
- infections may also involved eye, brain, or meninges
- principle mode of spread is direct contact, may be recurrent and outbreaks brought on by illness or emotional stress
viral infections: infectious mononucleosis def/ caused by characterized by (8 symptoms)
- acute infectious disease caused by the Epstein-Barr virus that most often affecting adolescents and young adults
- charcterized by fever, sore throat, malaise, fatigue, weakness, lymphadenopathy, hepatosplenomegaly, and mononuclear leukocytosis (lymphocytes, monocytes and its immature forms)
bacteria description
1.bacteria are unicellular microorganisms that lack nucleus and ER but contain both DNA and RNA and synthesize proteins
bacteria tinctorial (Gram stain) properties
gram negative
gram positive
- Gram negative= bacteria with single layered cell wall
2. Gram positive- bacteria with multilayered cell wall
when bacteria are stained with chemical dyes, they can vary in size and shape…
these shapes are divided into these 3 groups…
- cocci- rounded
- bacilli- rod shaped
- spirochetes (spirilla)- spiral shape
Gram (+) infections (2)
pyogenicity
shapes (2)
- some Gram bacterial are pyogenic because their reaction produces pus
- can be cocci and bacilli
Gram (+) bacterial infection: staphylococcus aureaus
what?
where? (3)
leading cause of…
the most common cause of suppuration and abscess formation involving: skin (pimples, boils, carbuncles), joints (arthritis), and bones (osteomyelitis)
3. leading cause of ineffective endocarditis
Gram (+) bacterial infection: streptoccus pyogens
is one of the most frequent bacterial pathogens of humans. It causes many diseases ranging from harmless infections of pharynx (‘strep throat’) and skin (impetigo), to serious infections like rheumatic fever
Gram + bacterial infection: streptococcus pneumoniae
is normal nasopharynx inhabitant and bacterial pathogen causing pneumonia, otitis media and meningitis that are preceded by common viral infections
Gram (+) bacterial infection:
corynebacterium diphtheriae
what it is
what a bad infection may cause
- an acute membranous (white-gray collection of necrotic tissue, fibrin and bacteria) infection of upper respiratory tract that may produce asphyxia.
- The gravity of infection is related to the production of a diffusing exotoxin that may cause myocarditis.
Gram (+) bacterial infection:
clostridium perfringens
what it causes
what happens if it infects wounds
- anaerobe spore forming bacilli causing common bacterial food poisoning ( no proper food refrigeration) and benign diarrheal disease or some time serious necrotizing enteritis.
- When C. perfringens contaminate wounds after incubation period of 2-4 days after injury it may cause gas gangrene (fatal, gas-forming necrotizing infection)
Gram (+) bacterial infection: clostridium tetani def how it works vaccination?
- cause of a severe infectious disease called Tetanus which may develop when the bacillus gains access from the soil to the wound that provide anaerobic conditions for bacterial growth.
- It produces exotoxin that passes along the nerves from the wound to the spinal cord (1-3 weeks) where it stimulates motor neurons causing tonic muscle spasm -‘lockjaw’, opisthotonus (increased muscle tone on backof body) , triasmus, glottal spasm and convulsions that may cause death
- An effective vaccine is available
gram (-) bacterial infection: bordetella pertussis def incubation time progression of disease vaccination available?
- cause pertussis (whooping cough), an acute, contagious disease commonly seen in children under 5 years of age.
- incubation of 7-14 days
- the disease begins as a infection that progresses and it is characterized by paroxysms of coughing (lasts 4-5 weeks) which end in whooping inspiration.
- Tdap vaccine is given in infancy.
gram (-) bacterial infection: haemophilus influenze what its not the cause of... where its found what it causes
- is small Gram-negative coccobacil that was once considered, mistakenly, the cause of pandemic influenza.
- H.influenze is normally found in the human nasopharinx
- most common cause of meningitis in children. It also causes sinusitis, otitis media, pneumonia, arthritis, epiglottitis
gram (-) bacterial infection- neisseria meningitidis what it causes how its spread different types (3) main characteristics
- causes pyogenic meningitis in children younger than 5 years of age
- It is spread from one person to another primarily by respiratory droplets and as an epidemic disease occurs in crowded quarters.
- 3 types- type A is a main cause of epidemic and B and C cause sporadic cases.
- Main characteristics are fever, headache and stiff neck and treatment require high doses of antibiotics.
gram (-) bacterial infection
neisseria gonorrhoeae
what it causes
incubation period
characterized by…
what happens if not treated
- gonorrhea, usually the main cause of genitourinary organ infections.
- incubation period- 3-5days after sexual contact with an infected partner
- characterized by a purulent urethral discharge in man. Symptoms are less prominent in women.
- If the antibiotic (penicillin) treatment is not started promptly, urethral stricture in man and fallopian tubes infection ( salpingitis) in women is a common complication.
gram (-) bacterial infection-
escherichia coli
2 types of bacterial infections more common
what it causes
what some strains can cause
- 2 types of bacterial infections more common : Salmonella typhi (typhoid fever caused by contaminated water and food- dairy products and shellfish)
Salmonella dysenteriae (causes dysentery - necrotizing infection of distal small intestine and colon),
- causes enteropathogenic bacterial infections
- normally present in human colon, but aggressive when present in urinary tract, or meninges. Some strains release the endotoxins and cause serious intestinal disease.
gram (-) bacterial infection
spirochetal bacterial infections:
treponema pallidum
what it causes
3 types
- penicillin sensitive spirochete that causes sexually transmitted syphilis
3 types: - primary syphilis: chancre lesion at the site of bacterial inoculation and inguinal lymphoadenopathy
- secondary syphilis: systemic bacterial chronic inflammation with lesions in skin, meninges, liver …
- tertiary syphilis: is an asymptomatic period complicated with tissue necrosis (gumma lesions): result of obstructive vascular lesions of small arteries
chlamydia, rickettsia, mycoplasma
generalities
Chalamidia, rikettsia and mycoplasma are grouped together because they are similar to bacteria (divide by binary fusion, susceptible to antibiotics) but lack certain structures or metabolic capabilities (Chlamidia cannot synthesize ATP).
chalamidia trachomatis
what it needs to live
what it causes (2)
- obligate intracellular parasites
- leading infectious cause of female sterility (scarring and narrowing of fallopian tubes)
- blinds by trachoma (chronic inflammation of conjuctiva that eventually scars the cornea and makes it opaque)
rickettsia
how its transmitted
what they cause
when is this prevalent?
- group of small pathogens mostly transmitted btwn mammals by arthropodes (insects).
- they are obligated intracellular parasites that cause epidemic typhus, spotted fever, etc. b y injuring the endothelial cells
- cause a heoorrhagic vasculitis that is often visible as a skin rash but they may also cause pneumonia, hepatitis or injure CNS and cause death.
- common in wars, or unsanitary conditions
mycoplasmas
superlative
how it spreads and what it causes
how its treated
- tiniest free-living orgamisms known
- spread from person to person in aerosols, bind to the surface of epithelial cells in airways and cause atypica pneumonia (“walking pneumonia”) characterized by peribronchiolar infiltrates of lymphocytes and plasma cells.
- infection is treated by antibiotics
fungi
what they are
cellular structure
2 locations they are found in and examples
- are the most plant-like of human pathogens.
- have thick cell wall and may have more than one form and grow by extension and branching of filamentous structures.
infections can be:
- in superficial tissues- harmless, restricted to epidermis (tinea cutis= athletes foot)
- deep organs and tissues: can cause life threatening infections (candiada albicans- opportunistic infection in AIDS, after chemotherapy)
protozoan parasites
superlative
3 types and what they cause
- parasitic protozoa- motile, single celled pathogen that are among the foremost causes of disease in developing countries
- simplest protozoa is trichomonas- which is sexually transmitted, and colonizes vagina and male urethra.
- intestinal protozoa (entamoeba histolytica) are infectious when eaten
- plasmodia- protozoa that reside in blood cells are transmitted by insects (anopheles mosquito)
helmints reproduction (2)
- multicellular worms that have strict specificites for the definitive host in which sexual reproduction takes place, or for the intermediate host (vector) in which reproduction is asexual.
- helmints do not multiply w/i the host but make eggs that cause inflammatory response
3 classes of helmints
- nematodes- round hook amid pin worms that remain in the intestinal lumen
- cestodes- flat worms in pork and beef
- trematodes- water
what are obligate intracellular parasites?
parasites- require living cells in which to replicate w/ or w/o interfering w/ cell functions
