Microbiology Chapter 16

What forms the boundary between the human body and the environment?

The integument, which includes skin, hair, nails, and glands.

What is the outermost layer of the skin called?

Epidermis.

What is the stratum corneum?

The outermost layer of the epidermis, composed of dead cells that slough off daily.

How often is the entire epidermis replaced?

Every 25 to 45 days.

What is the role of keratin in the skin?

It gives cells the ability to withstand damage, abrasion, and water penetration.

What is the dermis composed of?

Connective tissue, including fibroblast cells, collagen, macrophages, and mast cells.

What results from damage deep enough to penetrate the dermis?

Broken blood vessels and possible blister formation.

What is sebum and its role in skin defense?

An oily substance with low pH that inhibits microorganisms and serves as nutrients for microbiota.

What is the function of lysozyme?

An enzyme that breaks down peptidoglycan in bacterial cell walls, found in sweat, tears, and saliva.

What are antimicrobial peptides?

Positively charged chemicals that disrupt bacterial membranes, keeping microbial counts low on the skin.

What is MRSA?

Methicillin-resistant Staphylococcus aureus, a common cause of skin lesions that is resistant to multiple antibiotics.

What are the signs and symptoms of MRSA skin infections?

Raised, red, tender lesions that may have pus and feel hot, often occurring in breaks in the skin.

How is MRSA transmitted?

Through contaminated surfaces and direct contact; individuals with active infections should keep lesions covered.

What diagnostic test is characteristic for MRSA?

The coagulase test.

What is the recommended treatment for MRSA infections?

Incision and drainage of lesions, along with antimicrobial treatment, typically using multiple antibiotics.

What are maculopapular rash diseases?

Skin eruptions caused by various microbes, characterized by flat to slightly raised colored bumps.

What is a significant complication of measles?

Subacute sclerosing panencephalitis (SSPE), a progressive neurological degeneration.

What are Koplik spots?

Small white lesions with a red ring on the oral mucosa, a prodromal sign of measles.

How is measles transmitted?

By respiratory droplets; it is highly contagious.

What vaccine is used to prevent measles?

The MMR vaccine, which contains live, attenuated measles virus.

What is rubella also known as?

German measles.

What serious risk does rubella pose to pregnant women?

It can cause serious damage to the fetus in utero.

What is the typical presentation of measles?

Sore throat, dry cough, headache, conjunctivitis, fever, and a widespread rash.

What is the incubation period for measles before symptoms appear?

The person is infectious during the incubation and prodrome phases, before the rash appears.

What is the primary method for diagnosing measles?

Clinical presentation and ELISA testing for IgM to measles antigen.

What are the common signs of a maculopapular rash?

Flat to slightly raised colored bumps on the skin.

What is the role of good hygiene in preventing MRSA infections?

It is essential for prevention, as MRSA can be transmitted through contact with contaminated surfaces.

What must women of childbearing years ensure before planning to conceive?

They must be vaccinated against rubella.

What is the appearance of postnatal rubella rash?

A rash of pink macules and papules that appears first on the face and progresses down the trunk.

How long does the postnatal rubella rash take to resolve?

It advances and resolves in about 3 days.

What characterizes adult rubella?

Joint inflammation and pain rather than a rash.

What is congenital rubella and its effect on the fetus?

It is teratogenic and can cause harm to the fetus, including miscarriage or permanent defects.

What is the most common defect caused by congenital rubella?

Deafness.

What is the causative agent of rubella?

Rubivirus.

When was rubella declared eliminated from the U.S.?

In 2004.

What vaccine is given to prevent rubella?

The attenuated rubella vaccine is given in the MMR at 12-15 months and a booster at 4-6 years.

What is Fifth Disease also known as?

Erythema infectiosum.

What is a characteristic symptom of Fifth Disease?

A 'slapped cheek' appearance that begins on the face.

What is the causative agent of Fifth Disease?

Parvovirus B19.

What is the common disease in young children known as 'sixth disease'?

Roseola.

What are the signs and symptoms of roseola?

High fever followed by a maculopapular rash that appears after the fever subsides.

What is the causative agent of roseola?

Human herpesvirus 6.

What is impetigo?

A superficial bacterial infection that causes the skin to flake or peel.

What are the common causative agents of impetigo?

Staphylococcus aureus and Streptococcus pyogenes.

What are the signs and symptoms of cellulitis?

Fever, swelling of lymph nodes, and red lines leading away from the area.

What are the common causative agents of cellulitis in healthy individuals?

Staphylococcus aureus or Streptococcus pyogenes.

What is Staphylococcal Scalded Skin Syndrome (SSSS)?

A dermolytic condition caused by Staphylococcus aureus, affecting mostly newborns.

What are the signs and symptoms of SSSS?

Bullous lesions and widespread desquamation of the skin.

What is the causative agent of SSSS?

A strain of Staphylococcus aureus that produces exfoliative toxins.

What are the two viral diseases that present as generalized rashes?

Chickenpox and smallpox.

What virus causes chickenpox?

HHV 3 varicella-zoster virus.

What is the incubation period for chickenpox?

10 to 20 days.

What is a key characteristic of the chickenpox rash?

Lesions progress from macules and papules to itchy vesicles filled with clear fluid.

What happens during the reactivation of the chickenpox virus?

It causes shingles (herpes zoster) with characteristic asymmetrical distribution on the skin.

What virus causes shingles?

Herpes Zoster (Human herpesvirus 3, HHV-3)

What are the signs and symptoms of shingles?

Tender, persistent vesicles and postherpetic neuralgia.

What is postherpetic neuralgia?

Inflammation of the ganglia and nerve pathways causing pain and tenderness.

What vaccine was licensed in 2006 to prevent shingles?

Zostavax

What is the causative agent of chickenpox?

Human herpesvirus 3 (HHV-3)

How does HHV-3 spread in the body?

Enters respiratory tract, invades bloodstream, and disseminates to the skin.

What are the signs and symptoms of smallpox?

Fever, malaise, and a rash that begins in the pharynx and spreads to the face.

What is a characteristic feature of the smallpox rash?

It progresses from macular to papular, vesicular, pustular, and then crusts over.

What is cutaneous anthrax?

An infection caused by Bacillus anthracis, characterized by a necrotic papule that forms a black eschar.

How can cutaneous anthrax be transmitted?

Through cuts or abrasions, or contact with infected animal hides.

What is the primary treatment for cutaneous anthrax?

Antibiotics; untreated cases can be fatal in 20% of instances.

What are dermatophytes?

A group of fungi that cause skin conditions, confined to nonliving epidermal tissues.

What is the primary function of the conjunctiva?

To lubricate and protect the eye surface.

What is the role of tears in eye defense?

They prevent attachment of microorganisms and contain lysozyme and lactoferrin.

What is immune privilege in the eye?

Reduced innate immunity to prevent inflammation that could hinder vision.

What is conjunctivitis commonly known as?

Pinkeye

What are the common signs of bacterial conjunctivitis?

Milky discharge and eyes glued shut by secretions.

What are the causative agents of neonatal conjunctivitis?

Neisseria gonorrhoeae and Chlamydia trachomatis.

What is keratitis?

Invasion of deeper eye tissues that can lead to blindness.

What are the common causes of keratitis?

Herpes simplex virus and Acanthamoeba.

What is the treatment for viral keratitis?

Trifluridine or acyclovir.

What is the primary method of diagnosing keratitis?

Clinical diagnosis or viral culture/PCR if needed.

What is the main characteristic of the eye's natural defenses?

The eye has a robust microbiome and several protective mechanisms.

What can cause conjunctivitis aside from infections?

Allergic responses and eye injuries.

What is the significance of lysozyme in tears?

It helps to break down bacterial cell walls, providing antimicrobial defense.

What is the role of the cornea in the eye?

It acts as the 'windshield' of the eye, protecting internal structures.

What happens to the eye's immune response during inflammation?

Inflammation does not occur as readily to protect vision.