Infectious Diseases (week6) Flashcards
MRSA (methicillin-resistant Staphylococcus aureus)
(methicillin—a beta-lactam antibiotic)
a) Staphylococcus aureus is a normal skin flora, and occasionally can cause infections such as boils and cellulitis in immunocompetent people
b) MRSA developed in 1960’s in hospitalized patients that had been on methicillin so long that one strain of the staph bacteria mutated and became resistant.
c) now rampant in some hospital settings, nursing homes, etc, and is still generally known as a nosocomial disease—spread by
(1) direct patient-to-hands-to-patient contact
(2) colonization of nares of healthcare workers
(3) occasionally fomites such as stethoscopes.
d) usually invades wounds but “likes” fomites such as urinary catheters, IV catheters, etc, which can take
it to a site to colonize, such as bladder, blood, etc.
e) recently a new strain, called community-acquired MRSA has developed—found in wounds of people who haven’t been in a hospital setting.
f) the drug vancomycin is now one of the few drugs that will destroy MRSA.
resistant Streptococcus Pneumoniae
a) most common microbe causing otitis media (inner ear infection)
b) used to be easily treated with penicillin until ear infections became overtreated or treated inappropriately (antibiotics don’t cure viral ear infections)
c) new strain of strep developed that makes beta lactamase & now many ear infections are much harder to get rid of.
VRE—vancomycin-resistant enterococcus
1) another hospital-associated infection
2) Enterococci faecalis is a normal bowel flora, but in hospitalized people (or residents of nursing homes, etc) will often migrate to urinary tract & other areas.
3) used to be easily dealt with using Vancomycin but then resistance developed due to a mutated gene that changed one small part of a protein on the enterococcus cell wall – now Vancomycin won’t bind to the microbe cell wall to destroy it.
4) as a result, only very heavy-duty alternative antibx are effective now.
cellulitis
infection of the dermis and subcutaneous tissue
a. pathogenesis:
1) most commonly, an organism such as Staphylococcus aureus
that normally dwells on TOP of the skin (ie, on epidermis layer), gains deeper entry after a laceration, puncture, etc
(sometimes the breach is microscopic).
2) or sometimes cellulitis follows a milder staph infection of the
skin such as impetigo, an eruption of blisters usually around
nose & mouth that are itchy, crusty, and contagious.
b. infected area is erythematous, swollen, painful
c. tx (treatment) for cellulitis—abx (antibiotics)
botulism
a. caused by the toxin of Clostridium botulinum, a bacillus that can invade the body via food or soil (dirt-to-wound).
b. toxin heads for neuromuscular nerve synapses & blocks
acetylcholine muscle receptor cells.
c. typical S&S is a descending, symmetric paralysis, including
respiratory
d. ex—“floppy baby syndrome”—seen in infants (<1 year) that eat
honey contaminated with C. botulinum.
e. considered one of top candidates for bioterrorism use.
f. tx—temporary mechanical ventilation, other supportive tx
tetanus
a. vaccination as part of DPT (diphtheria, pertussis, tetanus) but immunity weakens so must get boosters every 10 years.
b. pathogenesis of tetanus disease:
1) caused by Clostridium tetanii, a bacillus which can live in soil as a spore -> when deposited in a wound, will then germinate as it becomes active, will release exotoxin tetanospasmin ->
2)blocks inhibitory neurotransmitters & causes uninterrupted nerve impulses to muscle cells -> can cause jaw muscle tightening called trismus (lockjaw), or more severe tetany – condition characterized by muscle twitching, cramps, convulsions,
c. tx—antibx & TIG.
rabies
a. a virus transmitted in saliva of infected host, usually by bite to the skin (most common vector is a bat)
b. virus travels via peripheral nervous system (PNS) to the brain & spinal cord (central nervous system – CNS) and causes brain
inflammation -> leads to S&S of anxiety, agitation, confusion, convulsions
c. other S&S include production of large amount saliva, plus dysphagia = “foaming at the mouth” & “hydrophobia” (not really a fear of water, just can’t swallow).
d. tx:
1) treatment needs to begin within first 14 days with post-exposure prophylaxis (PEP) – one dose of rabies immunoglobulin and four doses of rabies vaccine.
2) if not treated within this time, the rabies virus will continue its “trip” all the way up to the CNS—once CNS infected, there is no cure.
3) without tx, almost always fatal.
malaria
a. responsible for 2 million deaths in the world yearly.
b. caused by protozoa that is transmitted via mosquito vector.
c. protozoa reproduces in liver cells (hepatocytes) and then is released
into blood, where it infects RBCs & causes them to rupture (hemolysis) as the RBCs rupture, they trigger a flooding of acute phase
reactants into blood -> causes S&S
d. S&S – high fever, chills, arthralgia, anemia, splenomegaly, cerebral ischemia, heart failure
e. tx—Prevention with malaria vaccination in children, or with quinine-based drugs, mosquito nets, use of insect repellant that
contains DEET. Antiparasitic or IV antimalarial drugs once diagnosed.
zika virus
a. Zika is caused by the Zika virus, which is spread to people primarily through the bite of an infected mosquito.
b. Signs and symptoms may be mild and are similar to the S&S seen with the flu. People usually don’t get sick enough to go to the
hospital, and they rarely die of Zika. However, Zika infection during pregnancy can cause birth defects such as microcephaly (brain and
head smaller than normal).
c. Transmission (spread) occurs from mosquito bites or –person-to-mosquito-to-person; from a pregnant woman to her fetus; or by sexual transmission.
d. Prevent Zika by using insect repellants that contain DEET, use of light-colored clothing when outdoors, use of window/door screens
and mosquito nets, removal of standing water where mosquitos reproduce. Sexual abstinence or condom use should be considered
for 8 weeks to 6 months. Pregnant women or those wishing to become pregnant should avoid areas where a Zika outbreak is
known.
e. Diagnosis: blood or urine test can confirm a diagnosis.
f. Treatment: supportive care = fluids, rest, acetaminophen.
strep throat
a. caused by Streptococcus pyogenes -> invades via coughing, sneezing
b. S&S – red, sore throat, often white patches on tonsils
c. with certain strains of strep, can get scarlet fever (AKA “scarlatina”) along with above S&S—a fever and rash that can cover whole body.
d. VERY important for infected person to get antibx early on: getting an early and thorough treatment of antibx will lessen chance of
autoimmune disease like rheumatic fever or rheumatic valve/heart
disease
diphtheria
a. very contagious upper respiratory infection (URI) caused by bacterium transmitted by cough, sneeze, etc
b. S&S – sore throat, fever, pseudomembrane across tonsils & throat
pertussis
a. a highly contagious disease that is one of the leading causes of vaccine- preventable deaths in underdeveloped countries
b. also known as whooping cough, since one of S&S are horrible violent coughing fits that can be so bad that the person cannot eat & becomes malnourished (vaccine for diphtheria & pertussis given with tetanus as DPT)
mumps
a. virus that invades parotid glands—swelling, fever
b. main complication is infertility in males.
c. rarely seen in developed countries because of vaccine (MMR)
measles (2 weeks)
a. rubeola (nickname– “two-week measles” or just “the measles”)
1) virus passed by coughing, sneezing, etc
2) S&S – dense red maculopapular rash starting on head & going down to body; also fever, cough, runny nose, conjunctivitis.
3) can have serious complications such as encephalitis (literally=inflammation of brain but usually refers to inflammation from microorganism)
4) rarely seen in developed countries except in
immunocompromised or
those not vaccinated with MMR, but still endemic in certain
underdeveloped areas.
measles (3 day)
rubella (nickname—“three-day measles” or “German measles”)
1) milder virus & mild S&S—fever, rash, swollen glands.
2) main concern is if a woman contracts the disease in early
pregnancy:
a) can cause baby to be born with problems like mental retardation, eye problems, hearing problems, and others
b) child-bearing age women should always have a rubella titer done, and if low, need to be vaccinated.
3) vaccine (MMR) has eradicated it in US & certain other
