ch 16 infectious diseases of the skin and eyes

microbio final exam studu guide

what is catalase test

• detects enzyme catalase (breakdown of hydrogen periozide, oxygen + water)

• postive results: bubbles form when H2O2 is added

• differentiates: Staphylococcus (+) from streptococcus (-)

what is a coagulase test

• detects enzyme coagulase (clots plasma)

• positive result: clotting/clumping

• produced by staphylococcus aureus (helps it evade host defenses)

what are the defenses of the skin

• keratinized layer (tough barrier)

• sloughing (shedding cells remove microbes)

• low pH (acidic environment)

• high salt (inhibit microbes)

• antimicrbial peptides

• sebum (oily secretion, antimicrobial

name the maculopapular rashes

• measles (rubeola)

• rubella

• fifth disease (erythema infectiosum):

• rosela

maculopapular rashes: what is the agent for measles (rubeola)

• Agent: Measles virus.

maculopapular rashes: what are the symptoms for measles (rubeola)

• Symptoms: Fever, cough, sore throat, conjunctivitis, Koplik’s spots, rash.

maculopapular rashes: what are the complications for measles (rubeola)

• Complication: Subacute sclerosing panencephalitis.

maculopapular rashes: what is the prevention for measles (rubeola)

• Prevention: MMR vaccine.

maculopapular rashes: what is the treatment for measles (rubeola)

• Treatment: Supportive care.

maculopapular rashes: what is rubella

• agent

• forms

• prevention

• treatment

• Agent: Rubella virus.

• Forms:

  • Postnatal: mild rash, joint pain (“3-day measles”).

  • Congenital: teratogenic → deafness, cardiac defects, retardation, miscarriage.

• Prevention: MMR vaccine.

• Treatment: Supportive.

maculopapular rashes: what is fifth disease

• Agent: Parvovirus B19.

• Symptoms: “Slapped-cheek” rash, mild fever, fatigue, runny nose.

• Prevention/Treatment: Supportive care.

maculopapular rashes: what is rosela

• Agent: HHV-6.

• Symptoms: High fever (may cause seizures), rash after 4 days

• Prevention/Treatment: Supportive.

what are the pustular rashes

• chicken pox (varicella)

• smallpox (variola)

pustular rashes: what is chickenpox

• Agent: Varicella-zoster virus.

• Symptoms: Fever, itchy vesicular rash (clear fluid).

• Prevention: Varicella vaccine.

• Treatment: Supportive; avoid aspirin (Reye’s syndrome risk).

• latent in ganglia

pustular rashes/chickenpox: what is shingles

• Agent: Reactivation of latent varicella-zoster virus.

• Symptoms: Painful, localized rash along nerve pathways.

• Prevention: Shingles vaccine.

• Treatment: Antivirals (acyclovir), pain management.

pustular rashes: what is smallpox

• Agent: Variola virus.

• Forms: Variola minor (mild), variola major (severe, high mortality).

• Symptoms: High fever, malaise, rash with “BB pellet-like” lesions.

• Prevention: Eradicated; vaccine exists for bioterrorism preparedness.

• Treatment: Supportive.

what are the fungal infections

• dermatophytes

  • trichophyton (skin hair nails)

  • microsporum (skin hair)

  • epidermophyton (skin nails)

• superficial mycoses (malassezia)

fungal infections: what is dermatophytes

• spreads:

  • fomites

  • soil

  • humans

  • animals

• locations: skin, hair, nails

fungal infections: what is superficial mycoses (malassezia)

• spread: human contact

• location: skin surface (dandruff, discoloration)

name all the skin conditions

• MRSA

• rubeola (measles)

• rubella

• fifth disease

• roseola

• chickenpox

• shingles

• smallpox

• impetigo

• cellulitis

• SSSS

• cutaneous anthrax

• superficial mycoses

MRSA: what is the agents

• Staphylococcus aureus (methicillin-resistant)

MRSA: what is the virulence:

• Virulence: Hyaluronidase, staphylokinase, nuclease, lipases.

MRSA: what are the symptoms

• Symptoms: Raised, red, pus-filled, tender lesions.

MRSA: what is the resistance

• Resistance: Resistant to β-lactam antibiotics (methicillin, penicillin).

MRSA: what is the prevention/treatment

• Prevention/Treatment: Good hygiene, incision/drainage, antibiotics (vancomycin if severe).

skin conditions: what is impetigo

• Agent: S. aureus or S. pyogenes.

• Virulence: Exfoliative toxin, streptokinase.

• Symptoms: Flaky, crusty lesions; highly contagious.

• Prevention/Treatment: Hygiene, topical/systemic antibiotics.

skin conditions: what is cellulitis

• Agent: S. aureus, S. pyogenes, or other bacteria.

• Symptoms: Redness, swelling, pain, lymphangitis.

• Treatment: Antibiotics.

• fast-spreading infection in the dermis and subcutaneous tissues

skin conditions: what is Staphylococcus scalded skin syndrome (SSSS)

• Agent: S. aureus.

• Virulence: Exfoliative toxins.

• Symptoms: Bullous lesions, skin peeling (newborns/babies).

• Treatment: Antibiotics, supportive care.

skin conditions: what is cutaneous anthrax

• Agent: Bacillus anthracis (endospores).

• Symptoms: Eschar (black lesion).

• Fatality: ~20% untreated.

• Prevention/Treatment: Antibiotics, vaccine for high-risk groups.

skin conditions: what is superficial mycoses

• Agent: Malassezia species.

• Symptoms: Cosmetic issues (dandruff, skin discoloration).

• Treatment: Antifungal shampoos/creams.

what are the eye infections

• conjunctivitis (pink eye)

• keratitis

eye infections: what is conjunctivitis

• Agents:

  • Neonates: N. gonorrhoeae, C. trachomatis.

  • Others: S. epidermidis, S. pyogenes, S. pneumoniae, H. influenzae.

• Symptoms: Watery exudate, eyelids “glued shut.”

• Prevention/Treatment: Hygiene, antibiotics if bacterial.

eye infections: what is keratinitis

• Agents: Bacterial (80%), viral (HSV-1/2), protozoan (Acanthamoeba).

• Symptoms: Eye pain, vision loss, corneal damage.

• Treatment: Antimicrobials depending on cause.