infectious diseases- 26 Flashcards
saprophytes
microorganisms, especially certain bacteria, specialize in biodegrading dead animals or other organic material
indigenous flora
microorganisms, mostly bacteria, live on the skin and in the alimentary tract of humans and animals without producing ill effects and sometimes are helpful.
pathogens
microorganisms produce disease when they elaborate a toxin or gain entrance to a host tissue
virulence
the degree to which a pathogen elicits a response from the organism it is invading
infection
any disease directly caused by pathogens
vector
route of spread
another organism such as an insect that transports the pathogen to the host
carrier
host can carry and transfer the disease to another host without overt signs of infection
defense mechanisms between host and environment
Innate immune system:
- structural barriers
- inflammatory response
Acquired immune system:
- humoral system
- cellular immune system
1: mechanical barriers
2: inflammation
3: immune reactions
Innate immune system
1: structural barriers: skin and mucous membranes of the GI and lungs
2: inflammatory response:
- destroyed by phagocytes
Acquired immune system
previous or prolonged exposure to the offending agent and operates by enhancing the effectiveness of the inflammatory process.
humoral system
antibodies in the blood
cellular immune system
reaction is mediated by lymphocytes
immunization
primes the body to recognize particular foreign antigens and immediately produce antibodies to them
most frequent viral infections
respiratory illnesses (50%) other infections (10%) pneumonia-common cause of death
opportunistic infections
caused by fungi, bacteria, viruses, or parasites that do not normally cause infection in humans but that can colonize and infect immunocompromised people.
ex: cancer, AIDS
80% of infections
respiratory infections:
- upper resp infections
- influenze like infections
- pneumonia
- bronchitis
most common bacterial infections
- secondary infections: abscesses, pneumonia and wound infections
- STDs
predisposing factor for secondary infection
presence of dead tissue =growth medium for bacteria and lacks a blood supply to bring in phagocytes and antibodies
predisposing factor for secondary bacterial infection
=obstruction of a body passage
urinary tract, nasal, ears
(obstruction allows normal flora to proliferate to concentrations at which they become pathogenic
STDs
- gonorrhea- far more frequent
- syphilis-far more serious
- papilloma
- herpes
- chlamydia
viral infections
- viral gastroenteritis-less common, epidemics
- cold sores- common recurrent, 50% of population
- infectious mononucleosis
- viral hepatitis
- viral encephalitis
- HIV/AIDS-lethal
Rickettsial infections
rare but serious disseminated infections caused by bacteria that grow only within the cells of the host
- rocky mountain spotted fever
- typhus
- ehrlichiosis
fungal infections
athletes foot
ringworm
mucocutaneous candidiasis
P.jurovecii- fungus causing pneumonia
protozoal infections
- malaria-caused by small protozoan that invades and destroys RBC
- trichomonas vaginalis
- giardiasis=intestinal protozoan infection acquired by drinking contaminated water. results in watery diarrhea and wt loss
- cryptosporidium- similar to above
helminth infections
-schistosomiasis-produces chronic liver disease and urinary bladder cancer in endemic areas
many types infest the intestinal tract. more common in animals
common symptoms
- rapid onset of muscle aches
- fatigue
- fever
- rapid pulse
- feeling of tiredness and ill health
- malaise
physical exam of lesions may be sufficient for dx: measles, chickenpox, etc
*most exhibit cardinal signs of inflammation
diagnosis
- culture (bacterial and fungal)- from throat, urine, sputum, purulent lesions
- nucleic acid sequencing
- molecular testing
- microscopic exam- helminths & protozoa
septicemia
generalized infection involving the blood, and meningitis (spinal fluid)
coccal
round
bacillary
elongated
serologic tests
tests for antibodies in the pts serum
diagnosis of syphilis, systemic fungal disease, several bacterial diseases, viral, rickettsial and some parasitic diseases
fever
occurs with many bacterial, viral and rickettsial infections
exotoxins
proteinaceous poisons, virulent bacteria
- some kill cells directly
- others block nerve impulses or inhibit vital intracellular processes
pyogenic bacteria
elicit a neutrophilic inflammatory response with purulent exudate
tissue damage is then caused more by the pt’s own inflammatory and immune responses than by the direct action of the bacteria
pyogenic bacterial infections
- staphylococcal infection
- group A streptococcal infections
- group B
- viridans streptococcus infection
- streptococcus pneumoniae (pneumococcus)
- meningococcal meningitis
- haemophilus influenae infection
- legionellosis
- nonfastidious gram-negative rods
staphylococcal infections
most virulent=staphylococcus aureus
-can enter body by any route and infect any organ, causes abscesses (under the skin=furuncles; collection=carbuncle)
-many strains develop resistance to penicillin, and other antibiotics causing pneumonia and septicemia
toxic shock syndrome
strain of S aureus that produced a powerful exotoxin that was absorbed through the vaginal wall resulting in shock
group A streptococcal infections
most virulent bc they possess enzymes that allow them to spread rapidly through tissues via lymphatic vessels
most common- acute pharyngitis (Strep through)
- scarlet fever-blood vessels produce scarlet rash
- impetigo-superficial skin infection
- cellulitis-infection of soft tissue
- necrotizing fasciitis-infection of subcut. tissue/facia around muscles that causes rapid tissue destruction
-antibiotic tx and early surgical debridement
group B streptococcal infections
part of the indigenous flora of the rectum and vagina and less commonly the throat
- can infect the fetus in utero or birth
- cause pneumonia, sepsis or meningitis in the baby
- prevention: women are screened for rectal and vaginal colonization in 3rd trimester
- if positive: treated with antibiotics when labor begins
can also cause skin infections and sepsis-older adults
viridans streptococcus infection
part of indigenous flora of the mouth- most common cause of dental caries
- gets in bloodstream- can infect damaged heart valves and slowly destroy them- CHF
- can also cause necrotizing fasciitis
streptococcus pneumoniae (pneumococcus)
member of the indigenous nasopharyngeal flora- most common cause of pneumonia, otitis media, meningitis and rarely other local infections
- highly susceptible to penicillin and related antibiotics
- marked increase in infections of antibiotic-resistant strains
meningococcal meningitis
neisseria meningitidis- small gram-negative intracellular diplococcus, causes endemic and epidemic meningitis, esp in children and young adults
- transmitted via oral route
- disease usually starts with pharyngitis, fever and stiff neck
haemophilus inflenzae infection
used to be the major cause of bacterial meningitis and pneumonia in children but has become rare since vaccine got better.
-common cause of otitis media and sinusitis
legionellosis
gram-negative bacterium that lives in water reservoirs and cooling units but requires special media for culture.
- lesions mainly confined to the lung when large numbers of organisms are inhaled.
- most common in summer
- tx w/ antibiotics
nonfastidious gram-negative rods
enteric bacteria- indigenous inhabitants of the intestinal tract of humans
- typically cause abscesses
- pts often lapse into severe shock elicited by endotoxin in the bacterial cell wall. endotoxic shock (gram negative shock)=30-50% mortality rate
anaerobic bacterial infections
=bacteria grows in environments in which there is no to little oxygen
-distinctive by foul odor but otherwise seem similar to bacterial infections
sexually transmitted bacterial infections
gonorrhea
chlamydia
syphilis
gonorrhea
“the clap” “the drip”
outnumbers syphillis 30 to 1
men: dysuria, purulent urethral discharge (3-5 days after),
women: less symptomatic; dysuria, irregular menstruation, off cycle menstrual bleeding or bleeding with sex, continuation of purulent infection with abscess formation
dx: gram-stained smear-males; culture, nucleic acid amplification
pelvic inflammatory disease
purulent gonococcal infection of upper female genital tract
also caused by chlamydial and mixed anaerobic bacteria
disseminated gonococcal infection
septicemia, arthritis and endocarditis
women more than men
chlamydia
predominant cause of nongonococcal urethritis in females
- can result in sterility or ectopic pregnancy
- may infect infant during birth causing conjunctivitis or pneumonitis
syphilis
“great pox”
- produces chronic sequelae in the form of slow or unrelenting destruction of many organ systems- heart, aorta, soft tissue,, bones and nervous system.
- lower incidence, more serious
- transmitted only during first 2 stages of disease (1 year)
- incubation -3 weeks - allows therapy to be initiated before the pt can spread it
- can be spread to baby even after not contagious sexually
stages of syphilis
Primary syphilis: ulcerated lesion= chancre appears where spirochete entered the body. usually develops on or about the genitalia but not limited to. painless, shallow ulcer-mistaken for herpes.
Secondary: painless, prominent rash. serologic tests at their highest. lesions are less infective. if not treated, organisms withdraw into the body for the last time, selecting sites within the host to remain in a dormant state.
- primary and secondary may be mild or unrecognized
tertiary: “the great mimicker” can involve any organ system. cardiovascular disease and aortic aneurysm more common. CNS disease. lesions are a vasculitis. may be 3-25 years after primary.
clostridia
produce exotoxins
found in soil , anaerobic
can grow silently in necrotic tissue in deep wounds
stimulate nerve-muscle junctions causing painful contractions of muscles=tetanus
prevention by debridement
whooping cough
attacks ciliated epithelial cells lining the respiratory passages
-characteristic inspiratory “whoop”
mycoplasma disease
bacteria that do not possess rigid cell walls
primary atypical pneumona- may smolder for many months with low grade symptoms (cough, SOB, fatigue)
“walking pneumonia”
lyme disease
caused by infection with a spirochete by a variety of small deer tick adults or larvae.
site of tick bite may look like “bull’s eye”
accompanied by fever and lymphadenopathy
second stage- spreads throughout body. skin lesions, ms pain, arthritis, lymphadenopathy, cardiac arrhythmias, meningitis and severe lethargy
stage 3: 2-3 yrs after. severe arthritis and milked to severe encephalitis
chronic fatigue syndrome
plague
endemic in wild animals
rare in US
organism i capable of rapidly spreading throughout the body, causing extensive necrosis and hemorrhage
tularemia
uncommon. wild animal reservoir
can cause pneumonia
brucellosis
chronic systemic disease
“undulant fever” -waxing and waning of febrile episodes in the pt
bacteria harbored in farm animals. acquired by ingestion of infected meat, unpasteurized dairy product or by contact iwth animal.
leprosy (hansen disease)
tuberculosis-like organism
invades skin and peripheral nerves causing palpable lumps of granulomatous inflammation over the nerves
chlamydial infections
obligate intracellular parasites- lack ability to survive in the absence of a host #1 STD
viral infections
particles of genetic material (DNA or RNA) coated in protein, that can only replicate inside host cells- intracellular parasites
- can’t reproduce themselves but induce the host’s cells to produce the RNA and protein necessary for replication.
- known to cause certain neoplasms
-don’t respond to antibiotic therapy. need rest, hydration and alleviation of fever
commensals
live a long time in host cells without doing harm
interferon
protein produced by the body’s cells to prevent viral replication
childhood viral diseases
measures, rubella, varicella, mumps
affect children who haven’t been immunized and adults who have never had them
once infected, antibodies usually confer lifetime immunity.
dx: clinical picture, serologic tests
measles (rubeola)
small RNA virus transmitted by droplet infection through mouth and nose. highly infectious
10 day incubation
begins with conjunctivitis and photophobia (light sensitivity)
rash- small red dots over face ears-spreads to trunk and extremities.
-accompanied by cough and fever and maybe severe pneumonia
rubella
small RNA virus transmitted via respiratory route and causes very mild light rash, low grade fever and lymphadenopathy
*teratogenic and can cause congenital heart defects when acquired by mother in first trimester
varicella (chickenpox) and zoster (shingles)
DNA virus through respiratory tract.
incubation of 3 weeks.
chickenpox starts with malaise and fever followed by rash composed of large red bumps that develop blisters and later form a crust.
tx: rest and prevention of secondary bacterial infections.
after attack virus remains dormant in nerve ganglia. can become activated in adults poducing zoster or shingle.- spreads across spinal nerve causing painful eruption in the area of skin supplied by that nerve.
in immunocompromised pts-severe generalized infection
mumps
RNA virus acquired by respiratory route infects salivary glands and sometimes ovaries, testes and pancreas.
2-3 incubation period
malaise and fever followed by painful swelling of parotid glands.
smallpox (variola)
considered to be eliminated from the world
epidemics once devastated populations
rash that when heals leaves deep, pitted scars- focal necrotizing lesions in organs (lungs and intestinal tract-death in 10-20%)
postviral encephalitis
production of T lymphocytes or antibodies against the virus that cross react with brain antigens
influenza (flu)
human viral pathogen causes respiratory disease in epidemics during winter months.
symptoms: head cold with malaise to high fever with severe muscular aches and pains and pneumonia.
yearly vaccination
infectious mononucleosis
“mono”
epstein-barr virus-human herpes virus
affects teens and young adults
starts with sore throat and extreme tiredness
-some get significant hepatitis
-some get over it in a few weeks, others are ill for many months with fatigue and physical exertion exacerbates symptoms
-the older the pt the more devastating the disease
-cause of chronic fatigue syndrome
herpes simplex infections
DNA virus
type 1 causes mostly oral and skin lesions and transmitted by direct contact
type 2 causes mostly genital lesions and transmitted by sex.
after initial infection, virus lies dormant in nerves until episode of stress
tx: acyclovir
human papillomavirus infection
proliferative lesions of squamous epithelium including common skin warts, plantar warts, venereal warts, laryngeal polyps, premalignant dysplasias and carcinomas of the cervix, vulva and larynx
human immunodeficiency virus infection
HIV. cause of AIDS= recurrent opportunistic infections
HIV must be present for weeks before diagnosed
2-8 years before AIDS manifests
generalized lymphadenopathy, fever, weight loss, diarrhea, decreased CD4+ T lymphocytes
deficiency of the immune system particularly the cellular immune system. cells attach to CD4 receptor- gradual destruction of T lymphocytes over the years.
dx: Western blot
CD4 helper T cell count (400 abnormal)
no tx but prolong latent period: HIV protease inhibitors and reverse transcriptase inhibitors
rickettsial infections
small bacteria, obligate intracellular organisms
-preferably attack endothelial cells of blood vessels
typhus=rickettsia transmitted to human by the body louse
rocky mountain spotted fever- organism transmitted by tick.
most cause skin rash- result of small blood vessel involvement in skin and ensue hemorrhages
fungal infections
some fungi prefer to invade tissues in the yeast (bud)phase, others proliferate as hyphae (stems) in the body
classified by systemic and cutaneous forms
mycosis or mycotic infection
infection by a fungus
histoplasmosis
systemic fungal infection from bird droppings
coccidioidomycosis
systemic fungal infection harbored in soil
blastomycosis
systemic fungal infection causes destructive lung disease with chronic skin ulcers
cryptococcosis
systemic fungal infection in pigeon poop
causes chronic meningitis
opportunistic systemic fungal infections
elicit acute inflammatory response rather than a granulomatous one
cutaneous fungal infections
produce bothersome skin lesions that are not a serious threat to the pt.
-tineas- cause athletes foot, ringworm
protozoal diseases
unicellular organisms contain complex intracelluar structures
-alternate between proliferative (trophzoites) and dormant (cysts) forms
malaria
malaria
4 types: all transmitted by mosquitoes
infected bite releases SPOROQOITES into the blood which rapidly invades haptic cells and multiply.
dx: blood smears
heminthic infections
primitive roundworms and flatworms proliferate in the GI tract.
pinworm infestation-anal itching
trichinosis-ingestion of uncooked meat-severe ms pain, fever, eosinophilia in blood, sometimes death
tapeworm disease: ingestion of poorly cooked meat or fish. abdominal pain and diarrhea
