Microbiology - Lecture Exam #4 - MSSU

Name the 5 layers of the epidermis from outer to innermost

Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale

MNEMONIC: Come, Let’s Get Sun Burned

Which layer of the epidermis produces new skin cells?

Stratum basal

Which layer of the epidermis houses most of the immune cells?

Stratum spinosum

What is the role of keratin when it comes to skin protection?

How does sebum help protect the skin from microbes?

Sebum has a low pH which makes the skin inhospitable to most microorganisms

How do enzymes, like lysozyme, help protect the skin from microbes?

Breaks down peptidoglycan

Summarize the various aspects of skin anatomy and physiology that are naturally antimicrobial

High salt concentration, low pH, secretion of antimicrobial peptides

What are the two most common microbes found on human skin?

Staphylococcus epidermidis and Propionibacterium acnes

Where are microbes on human skin more likely to grow? Why?

Vast majority of microbes are in the uppermost layers of the epidermis, and 25% are localized in hair follicles

True or False: each person’s skin Microbiome is unique and relatively stable over time

True

Which layer of the epidermis is responsible for producing new skin cells?

a) Stratum corneum

b) Stratum granulosum
c) Stratum spinosum

d) Stratum basale

d) Stratum basale

Which of the following factors contribute to the skin’s natural antimicrobial properties? (Select all that apply)

a) High sugar content

b) High salt concentration

c) Low pH

d) Secretion of antimicrobial peptides

e) Thick outermost layer of live cells

b) High salt concentration

c) Low pH

d) Secretion of antimicrobial peptides

Which microbes are commonly found on human skin and associated with the normal skin microbiota? (Select all that apply)

a) Staphylococcus epidermidis

b) Escherichia coli

c) Propionibacterium acnes

d) Helicobacter pylori

e) Staphylococcus pneumoniae

a) Staphylococcus epidermidis

c) Propionibacterium acnes

What are the infectious diseases of the SKIN that we have discussed?

• MRSA

• Impetigo

• Cellulitis

• Staphylococcal Scaled Skin Syndrome (SSSS)

• Gas Gangrene

• Chickenpox

• Shingles

• HFMD

• Measles

What is/are the causative agent(s) of MRSA?

S. aureus

What are the signs/symptoms of MRSA?

Raised, red, and tender localized lesions

Often feel hot to the touch

Fever is common

What are the modes of transmission for MRSA?

Direct and indirect contact

• Common contaminant of daily surfaces that are not routinely sanitized

• Bacteria is introduced into breaks of skin

What are the virulence factors of MRSA?

• Withstands high salt, extremes in pH, and high temperatures

• Long viability (months)

• Coagulase (hemolytic abilities)

• Hyaluronidase (breaks down hyaluronic acid in skin, which holds cells together)

• DNase (digests DNA)

• Streptokinase (digests blood clots)

What are prevention practices for MRSA?

Hygiene practices

• Washing hands

• Keeping wounds clean and covered

• Avoid sharing PPE

Describe the epidemiology of MRSA

• Found across age groups

• Those with decreased immune response at higher risk

What is/are the causative agent(s) of Impetigo?

S. aureus and S. pyogenes

What are the signs/symptoms of Impetigo?

• Skin flaking/peeling off

• Crusts/flakes honey in color

• Usually present around the mouth, face, or extremities

What are the ways of transmission for Impetigo?

• Direct contact

• Through fomites and mechanical vectors

What are the virulence factors of Impetigo?

• Exfoliative enzymes

• Hyaluronidase

What are the preventative methods for Impetigo?

Hygiene practices

Describe the epidemiology of Impetigo

• Mostly affects preschool children (ages 4-7)

  • All ages can still acquire

What are the causative agents of Cellulitis?

S. aureus and S. pyogenes

What are the signs/symptoms of Cellulitis?

• Rapidly spreading redness (typically on lower legs)

• Pain

• Tenderness

• Swelling

• Warmth

What are the modes of transmission for Cellulitis?

Introduction of bacteria to the dermis through trauma

What are the virulence factors of Cellulitis?

• Hyaluronidase

• Streptokinase

What are preventative methods for Cellulitis?

• Proper wound care

• Moisturizing cracks in skin/feet

• Wearing protect clothing when risk of skin break is high

Describe the epidemiology of Cellulitis

• Affects all ages

• Elderly & immunocompromised most at risk

What is/are the causative agent(s) of Staphylococcal Scaled Skin Syndrome (SSSS)?

S. aureus

What are the signs/symptoms of SSSS?

Bullous lesions (wrinkled tissue paper)

What are the modes of transmission for SSSS?

• Direct contact

• Hematogenous spread from local infection

What are the virulence factors of SSSS?

Exfoliative toxins A & B

What are preventative methods for SSSS?

• Limiting carrier contact with neonates

• Using precautions when handling neonates

  • Hand washing, proper wound care, etc.

Describe the epidemiology of SSSS

Predominately in neonates and young children

What is/are the causative agent(s) of Gas Gangrene?

C. perfringens

What are the signs/symptoms of Gas Gangrene?

• Death of tissues

• Initial symptoms:

  • Suddenly, intense pain

  • Blood and foul smelling exudate

  • necrosis filled with bubbles of gas

What are the modes of transmission for Gas Gangrene?

• Contamination of wounds with Clostridium endospores from soil/feces

• Moves to anaerobic parts of the body

What are the virulence factors of Gas Gangrene?

Produces several exotoxins

• Hyaluronidase

• DNase

• Alpha toxin

What are preventative methods for Gas Gangrene?

Preventing wounds/getting wounds thoroughly cleaned

Describe the epidemiology of Gas Gangrene

• Rare in the U.S.

• Mortality is 25-30% with quick treatment

• Mortality is 100% with delayed treatment

What is/are the causative agent(s) of Chickenpox?

Human Herpes Virus 3 (AKA Varicella-zoster virus)

What are the signs/symptoms of Chickenpox?

• Fever

• Abundant itchy rash

• Rash progresses from papule to vesicle

• Begins on face and trunk and spreads to limbs

What are the modes of transmission for Chickenpox?

Viruses travel to root ganglia, where it goes latent and avoids immune clearance

What are prevention methods for Chickenpox?

Varicella Vaccine

Describe the epidemiology of Chickenpox

• Very contagious

• Mostly affects children as exposure happens earlier in life

• 20% mortality in immunocompromised

What is/are the causative agent(s) of Shingles?

Human Herpes Virus 3

What are the sign/symptoms of Shingles?

Asymmetrical lesions on the trunk or head

• Asymmetrical because they are in a dermatome

What are the modes of transmission for Shingles?

Shingles is a REACTIVATION of Chickenpox

• IS NOT transmissable

What are the virulence factors of Shingles?

The virus moves from root ganglion to dermatomes (reactivation of Varicella Virus)

What are the preventative methods for Shingles?

Zoster Vaccine

Describe the epidemiology of Shingles

• Develops after psychological stress

• More common in advanced age

What is/are the causative agent(s) of HFMD?

Viruses in the Enterovirus group

• Coxsackie Virus A16 most well known

What are the signs/symptoms of HFMD?

Starts with:

• Fever

• Sore throat

• Painful blisters on hands, feet, and mouth

What are the modes of transmission for HFMD?

Spread by droplet or direct contract, but also via fecal-oral route

No Virulence Factors for HFMD

What are the preventative methods for HFMD?

• Hand hygiene

• Removing infected children from public settings while rash persists (isolation)

Describe the epidemiology of HFMD

Most common in children under 5

• Outbreaks generally identified in childcare centers

What is/are the causative agents for Measles?

Measles Virus

What are the signs/symptoms of Measles?

• Sore throat, dry cough, conjunctivitis, and high fever

• Koplik’s spots lesions appear later

• Acute encephalitis:

  • Disorientation, seizures, deafness, or intellectual disability

• Subacute Sclerosing

• Panencephalitis:

  • Killing neurons and myelin producing cells

• Severe pneumonia or encephalitis

What are the modes of transmission for Measles?

Respiratory droplets or aerosols

What are the virulence factors of Measles?

• Immunosuppression

• Immune amnesia

• Fusion protein

• Lives up to 2 hours in airspace

What are the preventative methods for Measles?

MMR vaccine

Describe the epidemiology of Measles

• Primarily in unvaccinated children

• Highly contagious

A 6-year-old presents with honey-colored crusted lesions around their mouth and mild itching. What is the most likely causative agent?

a) Clostridium perfringens

b) Streptococcus pyogenes

c) Human herpesvirus 3

d) Measles virus

b) Streptococcus pyogenes

This disease is impetigo, which the causative agents are S. aureus & S. pyogenes

Which disease is known for its extremely high R-naught value (12-18), aerosol-based transmission, and potential to cause immune amnesia?

a) Chickenpox

b) HFMD

c) Measles

d) Shingles

c) Measles

Which features help distinguish Shingles from Chickenpox? (Select all that apply)

a) It causes a centripetal rash.

b) It is a reactivation of latent virus in root ganglia

c) It typically affects both sides of the body symmetrically

d) It is often associated with burning, painful lesions

e) It is caused by a different virus than chickenpox

b) It is a reactivation of latent virus in root ganglia

d) It is often associated with burning, painful lesions

What is the role of the conjunctiva?

Secretes an oil and mucus containing fluid that lubricates and protects the surface of the eye

What is the role of the cornea?

• Acts as the eye’s primary lens, responsible for focusing

• Protects as a shield against dirt, germs, etc.

  • Regenerates quickly if damaged

What is the role of ciliary body?

Produces aqueous humor and helps alter the shape of the lens to focus on near or far objects

What is the source of aqueous humor?

Ciliary body

What is the function of aqueous humor?

• Provides nutrients to cells of the internal eye anatomy

• Maintains intraocular pressure

• Contains antibodies to protect the eye

What is the drainage pathway of aqueous humor?

When there is too much aqueous humor, most of it drains out through the pupil, into Schlemm’s canal and gets reabsorbed by Episcleral veins

What protective enzymes are in tears?

Contains salt and the antimicrobial lysozyme and lactoferrin

What is the function of lysozyme?

Breaks down bacterial peptidoglycan

What is the function of lactoferrin?

Stabilizes tear film, promotes corneal wound healing, and binds to iron which inhibits bacterial growth

What are the layers of the tear film?

• Oil/lipid layer from meibomian glands

• Water/aqueous layer from lacrimal glands

• Mucus/mucin layer from conjunctival goblet cells

What is the role of meibum?

Creates the outer lipid layer in the tear film

• Prevents eye dryness

Define “immune privilege”

The restriction or reduction of immune response to certain areas of the body that reduces the potential damage to tissues that a normal inflammatory response would cause

How does immune privilege affect immune response in the eye?

In the eye, immune privilege would prevent the anterior chamber from being cut off from blood supply and allow lymphocytes to be less active than elsewhere in the body

What is a key genus found in the eye microbiome?

Corynebacterium

Which part of the eye is primarily responsible for producing aqueous humor?

a) Ciliary body

b) Conjunctiva

c) Cornea

d) Lacrimal gland

a) Ciliary body

What does the concept of “immune privilege” in the eye primarily refer to?

a) Enhanced antibody secretion in the anterior chamber

b) Suppressed immune responses to reduce inflammation

c) Rapid infiltration of phagocytes in response to microbes

d) Lack of blood supply to all eye tissues

b) Suppressed immune responses to reduce inflammation

What is the causative agent of bacterial Conjunctivitis?

S. aureus

What is the causative agent of viral Conjunctivitis?

Adenoviruses

What is the causative agent of neonatal Conjunctivitis?

N. gonorrhoeae or C. trachomatis

What are the signs/symptoms of bacterial Conjunctivitis?

Mucopurulent discharge

What are the signs/symptoms of viral Conjunctivitis?

Serous (clear) discharge

What are the overall signs/symptoms of Conjunctivitis?

• Redness

• Eyelid swelling & itching

What are the modes of transmission for bacterial Conjunctivitis?

Direct & indirect contact

• Direct contact via contaminated hands or objects

What are the modes of transmission for viral Conjunctivitis?

Respiratory droplets

What are the modes of transmission for neonatal Conjunctivitis?

Vertical transmission during childbirth

No virulence factors of Conjunctivitis in this unit

What are the prevention practices for Conjunctivitis?

• Hygiene practices like handwashing

• Screening maternal parents

• Provide antibiotics before delivery

• Providing antibiotic eye drops to newborns after birth

Describe the epidemiology of Conjunctivitis

• Bacterial more common in children

• Viral more common in adults

What is/are the causative agent(s) of Trachoma?

C. trachomatis

What are the signs/symptoms of Trachoma?

• Leads to chronic inflammatory damage and scarring

• Can lead to corneal opacity

• Calcified deposits in the eyelid

• First signs:

  • Mild conjunctival discharge

  • Slight inflammation of the conjunctiva