epidemiology: Propionibacterium acnes; normal bacterial
microbiota; up to 85% of adolescents suffer from acne at some time
pathogenesis: hair follicle infection that spreads into surrounding
tissue, generating an abscess; complications - skin disfigurement
(scars)
treatment: tetracyclines, oral contraceptives, vitamin A derivatives
(Retin A cream ... can cause dry skin; Accutane,
an oral medication which is unfortunately also a teratogen (it causes birth
defects) so it should
not be used by pregnant women) ... accutane
may be linked to psychiatric problems; light therapy (intense blue
light followed by red light); during 1998, Americans spent $800 million
on prescription drugs to treat acne
prevention: decrease sebum accumulation by thorough personal
hygiene and depress bacterial growth with topical peroxide-containing
medications
Furuncle (boil)
epidemiology: Staphylococcus aureus; normal bacterial
microbiota in up to 30% of normal humans
pathogenesis: infected skin follicle leads to formation of
an abscess;
complications - multiple abscesses (carbuncles);
"blood poisoning" (toxemia) due to systemic distribution of toxin
or bacteria; osteomyelitis
treatment:
"lance" abscess; treat with bacitracin, vancomycin or other antimicrobial
agents that are resistant to bacterial enzymes that destroy penicillins
prevention: personal hygiene; avoid contact with boils on
other people; newly-developed vaccine StaphVAX
epidemiology: Candida albicans, this dimorphic fungus
is a member of the normal microbiota; likelihood of developing disease
is enhanced by chronic skin moisture, especially in immunosuppressed
individuals (AIDS, diabetes, etc.)
pathogenesis: as Candida grows on the skin, it induces a
bright red inflammation, blister-like superficial lesions or more
severe lesions all of which are perhaps related to hypersensitivity;
it sometimes occurs around the mouth (angular chelitis); complications
include systemic infection, which can lead to fulminating disease
and death
treatment: clotrimazole, miconazole or nystatin for skin
infections; oral ketoconazole for systemic infections
epidemiology: Herpes
Simplex Virus 1 (HSV-1) is transmitted by direct contact;
immunocompromised people are especially vulnerable
pathogenesis:
recurrent chronic lesions (blisters) on face, fingers, hands ...
becomes latent in local nerves and exhibits recurrence during periods
of stress (physical or psychological); herpes means "to creep"
treatment: acyclovir (zovirax) shortens episode, slows recurrence;
valtrex is a second generation version of zovirax ... works better
prevention: avoid contact with skin sores on other people
epidemiology: Clostridium tetani; endospores of
this bacterium enter body via animal bites, scratches, puncture wounds;
fewer than 10 cases per year in US
pathogenesis: toxin (tetanospasmin) causes CNS damage
(4-21 days); complications - respiratory failure causes death (70% of
patients die)
epidemiology: Bacillus
anthracis, an endospore-forming soil bacterium; this zoonotic
disease primarily affects grazing animals such as cattle, sheep and
goats, but can be transmitted to humans by contact with the endospores,
either via skin wounds or by inhalation; this disease is considered
to be a good candidate for biological warfare, and has been used in terrorist
activities ... view a set of online CDC
videos on bioterrorism
pathogenesis:
as endospores germinate, the vegetative bacterial cells begin to produce
a necrotizing toxin that causes development of pustular lesions
called eschars characterized by necrotic centers that will eventually
be filled with black fluid; complications include fulminating
septicemia that frequently leads to death, especially from the pulmonary
form of the disease
Man
with eschar on his neck
characterized by necrotic centers that will eventually be filled with
black fluid; complications include fulminating septicemia that
frequently leads to death, especially from the pulmonary form of the disease
treatment: penicillin ... cipro (ciprofloxacin) was approved
in 2000
prevention: vaccine; avoid contact with endospore-contaminated
articles such as unwashed or unsterilized wool, goat hair, cattle hides,
etc.
Borrelia burgdorferi (bacterium) is spread by
the nymph stage (poppy-seed sized) of deer (black-legged) ticks ...
it takes ~36 hours for the tick to infect you with enough bacteria
to cause disease
reservoirs are white-tailed deer and white-footed mice
15,000 cases reported in the US each year, mostly in children
2-15 and adults 30-55 years old who live in the Northeast and upper
Midwest (more
epidemiology)
most frequently diagnosed tick-borne disease in the US
pathogenesis: - 60-85% of patients develop an expanding, ring-shaped
("Bull's-eye") red rash (erythema
chronicum migrans or ECM) at the site of a tick-bite
... after 3 days to one month; accompanied by flu-like symptoms (malaise
and fatigue, headache, fever and chills, nausea, muscle and joint pain,
neck stiffness) and patients may develop secondary skin lesions, facial
paralysis, forgetfulness; chronic, untreated systemic infection leads
to arthritis, heart inflammation, neurological abnormalities (weeks
to months); nerve demyelination may lead to multiple sclerosis-like
symptoms (years after infection)
treatment: ceftin (cefuroxime axetil), penicillin or tetracycline
(after diagnosis with a newly-approved test kit, "PreVue B"); although
there is controversy, it appears that long-term intravenous antimicrobial
agent therapy may be required in chronic cases
pathogenesis:
mosquito "injects" virus into bloodstream; virus replicates in
the CNS, causing fever and headache, vomitting,stiff back and
neck, drowsiness, tremors, loss of coordination, convulsions,
seizures; complications - may lead to coma as a result of CNS
damage (can lead to retardation, paralysis) and death occurs in
1-60%, depending upon the virus responsible
treatment: TLC ... management of symptoms and
complications; FDA has recently approved alpha-interferon as a
possible treatment for West Nile Fever
Man
with eschar on his neck