Ch 19 - Microbial Diseases of the Skin and Wounds

What factors make the skin inhospitable to most microbes?

• Salt

• Sweat

• Sebum

• Keratin

Toxic Shock Syndrome

• Cause Exotoxin-producing strains of Staphylococcus aureus (Gram-positive coccus).

• Virulence factors Exotoxins, enterotoxins.

• Portal of entry Staphylococcus either grows in the vagina or enters the body through a wound, grows, and produces toxin that enters the bloodstream.

• Signs and symptoms Sudden onset of high fever, vomiting, rash, extremely low blood pressure, and sore throat.

• Treatment Supportive therapy is extremely important; administration of vancomycin and antistaphylococcal immunoglobulin.

• Prevention Avoid vaginal insertions such as highly absorbent tampons, vaginal sponges, or diaphragms, or use them intermittently and for shorter periods.

Acne is mainly caused by which species?

• Propionibacterium acnes, which causes acne in 85% of afflicted adolescents and young adults.

Staphylococcus aureus may also cause acne

True or False? S. aureus and S. epidermidis evade the body’s defenses by synthesizing loosely organized polysaccharide slime layers, or capsules, that inhibit chemotaxis of and phagocytosis by leukocytes.

True

Which enzymes do S. aureus produce that contribute to their pathogenicity and survival?

• Coagulase

• Hyaluronidase

• Staphylokinase

• Lipase

• Beta-Lactamase

Focculitis, stys, furuncles, and carbuncles are caused by which species?

Staphylococcus aureus

What is the role of dendritic cells in the epidermis?

Dendritic cells phagocytize microbes and deliver microbial antigens to lymphocytes

What are the normal microbiota of skin?

• Lipophilic Yeast

  • Malassezia - Digests sebum

• Gram positive bacteria

  • Staphylococcus e.g., S. epidermidis

  • Micrococcus

  • Diphtheroids e.g., Propionibacterium acnes

What is Buruli ulcer?

Ulcer that is formed by insect bites. It starts as a small painless nodule, then swelling, then increased sudden pain. The finger ruptures with a foul smelling liquid coming out.

What is the bacteria that causes Buruli ulcers?

Mycobacterium ulcerans

What toxin is responsible for the destructive process of Buruli ulcers?

Mycolactone toxin from Mycobacterium ulcerans

Which Staphylococcus species produces exfoliative toxin and toxic shock syndrome toxin?

S. aureus

What two virulence factors do S. epidermidis have?

Lipase and a polysaccharide slime layer

What is the toxin that destroys fat and muscle cells below the skin?

Mycolactone toxin

This causes Buruli ulcers

What is treatment of Buruli ulcers?

• Surgeries

• Skin grafts

• Months of hospitalization

• Antibiotics

  - Rifampicin

  - Streptomycin

In what ways can necrotizing fasciitis gain entry?

Insect bites, direct contact, surgery, abortion, needlestick, etc.

It cannot however gain entry through aerosol droplets

What are the types of staphylococcal hair follicle infections or folliculitis?

• Sty - A pimple that occurs at the eyelid base

• Furuncle or Boil - Spread of infection to nearby tissues

• Carbuncle - Formed when multiple furuncles grow together

  These skin infections are usually caused by S. aureus.

How is folliculitis transmitted?

Direct contact or fomites

What are the 2 common species of staphylococci on skin?

• Staphylococcus epidermidis

• Staphylococcus aureus

What are the differences in virulence factors between both S. aureus and S. epidermidis?

In staphylococcus aureus, exfoliative toxins and toxin shock syndrome toxins are responsible for scalded skin syndrome and toxic show syndrome, respectively. Other virulence factors include coagulase enzymes that clots blood, which is not present in S. epidermidis.

Both strains of Staphylococcus have a polysaccharide capsule that can help attach its biofilms to catheters.

Table 19.1 slide 10

What is SSSS?

Staphylococcal Scalded Skin Syndrome

Skin becomes red and wrinkled and forms blisters

What is the causative agent and toxin responsible for SSSS?

Some Staphylococcus aureus strains that produce exfoliative toxins

What is the pathogenesis of SSSS?

There is no scarring because the dermis is unaffected. Death is rare. The occurrence of death may be due to secondary infections by Candida albicans or Pseudomonas aeruginosa

What is the diagnosis of SSSS?

• Diagnosed by characteristic sloughing of the skin

  • Outer epidermis peels off in sheets typically starting near the mouth spreading over the entire body

How is Staphylococcal Scalded Skin Syndrome transmitted?

Person-to-person spread of bacteria into cuts and abrasians.

What is impetigo (pyoderma)?

Red patches form on the face and limbs with oozing pus filled vesicles, thick honey-colored sticky crusts, intense itching. This is usually seen in children.

What are the causes of impetigo?

• Staphylococcus aureus

• Streptococcus pyogenes

What is erysipelas?

Impetigo infection that spreads to the lymph nodes with characteristic reddening of skin in the face, arms, or legs. Local lymph nodes are swollen and painful. The infection can be fatal if left untreated.

What are the causes of erysipelas?

Streptococcus pyogenes

What are the virulence factors of Strep pyogenes?

• M protein destabilizes complement, interferes with phagocytosis and lysis of bacterium

• Hyaluronic acid capsule hides bacteria from phagocytes

• Pyrogenic toxins Erythrogenic toxins that stimulate macrophages & helper T cells to release cytokines. This stimulates fever, rash, shock

What is pyrogenic toxin?

Toxin produced by S. pyogenes

Proteins that stimulate macrophages and helper T lymphocytes to release cytokines that in turn stimulate fever, a widespread rash, and shock.

What is pyrogenic toxin’s other name?

Erythrogenic Toxin

Pyrogenic toxin is secreted by which bacteria?

S. pyogenes

What is necrotizing fasciitis?

”Flesh eating” bacteria

What are the causes of necrotizing fasciitis?

• Mainly caused by Group A Streptococcus, such as S. pyogenes

• Staphylococcus aureus

What is the pathogenesis of necrotizing fasciitis?

• Streptokinase: dissolves blood clot

• Hyaluronidase: breaks down hyaluronic acid

• Deoxyribonuclease: breaks down host DNA

• M protein: helps bacteria survive phagocytosis Streptolysin: kills neutrophils and RBCs

• Exotoxin A: triggers immune responses to damage the healthy tissue

How is necrotizing fasciitis spread?

Person to person contact through broken skin

What are the virulence factors of necrotizing fasciitis?

Strains of S. pyogenes that cause the condition have enzymes, such as deoxyribonucleases, hyaluronidase, and streptokinases that allow the bacterium to invade body tissues. Streptococcal M protein allows the bacterium to attach to nasopharyngeal cells and to resist phagocytosis. The toxins streptolysin S and exotoxin A damage cells and tissue.

How is necrotizing fasciitis diagnosed?

Extreme pain that seems out of proportion

What is the treatment of necrotizing fasciitis?

• Debridement

• Affected tissue must be removed to prevent spread

• Treated with intravenous clindamycin and penicillin

What is the causative agent of acne?

Propionibacterium acnes

Commonly found on the skin Gram-positive, rod-shaped diphtheroids

What is the treatment of acne?

Specific wavelength of UV light. Retinoic acid and vitamin A derivative inhibits sebum formation

What are the steps in the development of pox lesions in the correct order?

Macule, papule, vesicle, pustule, crust, scar

What is the causative agent of cat scratch disease?

Bartonella henselae Gram-negative Intracellular bacillus of the skin

What are the signs and symptoms of cat scratch disease?

Swelling of a scratch leading to fever, malaise, swollen lymph nodes

What are the virulence factors of Cat scratch disease?

Endotoxin

What are all the important features of Pseudomonas?

• Commonly seen in burn victims

• Blood infection causes fever, chills, shock

What is Pseudomonas’s pigment?

Pyocyanin

Blue-green color

What are the virulence factors of Pseudomonas?

• Fimbriae & adhesins: Attach to host cells, form biofilms

• Capsule: shields bacteria from phagocytosis, helps in biofilm formation and attachment

• Neuraminidase: modifies host cell receptors to make bacterial attachment better

• Elastase: breaks down elastic fibers, cleaves IgG & IgA

• Endotoxin (lipid A): fever, blood clotting, inflammation, shock

• Exotoxin & exoenzyme S: inhibit translation in host

• Pyocyanin: form superoxides that damage host cells

What is the causative agent of Pseudomonas infections?

Pseudomonas aeruginosa

What are the diseases of Pseudomonas?

• Otitis externa (Swimmers ear)

• Nail infections

• Burn infections

Is Pseudomonas multi-drug resistant?

Yes

What are the reasons that Pseudomonas is multidrug resistance?

• Ability to metabolize many drugs

• Antiports that pump many drugs out of bacterium

• Ability to form biofilms

What drugs or things is Pseudomonas resistant to?

Resistant to antimicrobials, quats, soaps etc., lives in disinfectants

What is Rocky Spotted Mountain Fever?

Non-itchy petechial rash starting on hands & feet and then spreads to the torso area Organ failure can occur in severe cases Fever, nausea, vomiting, muscle pain, chills, delirium, convulsions, coma, death

What is RMSF’s causative agent?

Rickettsia rickettsii

What is RMSF’s vector and resevoir?

• Vector – Ticks

• Reservoir - Rodents

What is RMSF’s pathogenesis?

• Dormant in salivary gland of tick vectors

• Only when the ticks feed for several hours is the bacterium infective

• Bacteria reaches blood, damages blood vessels

• R. rickettsii does not secrete any toxins

What is the diagnosis, treatment, and prevention of RMSF?

• Diagnosed with serological testing

• Treated with antibiotics-doxycycline

• Prevented with the use of tick repellents and avoidance of tick-infested areas

What is the cause of cutaneous anthrax?

Bacillus anthracis

B. anthracis is an endospore forming rod.

What is an eschar of cutaneous anthrax?

Black, painless, crusty, and swollen ulcer These are characteristic of anthrax

True or false? Gas gangrene causes a crusty black ulcer called an eschar.

False

Cutaneous anthrax is characterized by the presence of crusty black ulcers on the skin called an eschar.

What is gas gangrene?

• Death of muscle and connective tissue

• Spreading black necrosis

• Gas bubbles/froth

• Swelling and pain

What is the cause of gas gangrene?

Clostridium species

What are the virulence factors of gas gangrene?

• Endospores

• Vegetative cell secretion of 11 toxins that lyse erythrocytes and leukocytes, increase vascular permeability, reduce blood pressure, and kill cells, resulting in irreversible damage.

• Rapid growth and reproduction

What is the disease progress of smallpox?

1. Macule (Flat and red)

2. Papule (Raised sore)

3. Vesicle (Clear fluid)

4. Pustule (Lesion filled with pus)

5. Crust (Lesion ruptures and dries)

6. Scar (Lesion penetrates dermis)

Variola virus causes what disease?

Smallpox

Poxviruses are enveloped ________ viruses.

dsDNA

What are the virulence factors of poxvirus?

• Proteins inhibit interferons

• Complement

• Inflammation

What is the portal of entry for smallpox?

Close contact is necessary for infection with smallpox viruses. This occurs primarily through inhalation of viruses in droplets or dried crusts.

What is the treatment for smallpox?

Immediate immunization of people exposed to smallpox virus prevents the disease from developing. No treatment exists once smallpox develops.

What is herpes whitlow?

Inflamed blister when a herpesvirus enters a cut or break in the skin of a finger.

What does the herpes infection cause?

Human herpesviruses 1&2

Lesions and warts are caused by what virus?

Papillomaviruses

What are the types of warts?

Plantar - Foot

Flat - Facial

Seed - Entremities, such as fingers

Genital - Genitalia

“Teardrops on rose petals” rash refers to what disease?

Chickenpox caused by the Varicella zoster virus

What occurs when there is a reactivation of the varicella zoster virus?

Shingles

Koplik’s spots are characteristic of what disease?

Measles (Rubeola)

The measles virus are fatal in children and humans are the only host.

German measles or 3-day measles is another term for what disease?

Rubella

True or false? Rubella can cause congenital defects or death of a fetus.

True

Mycoses is another term for what infection?

Fungal infections

What is dermatophytoses?

Cutaneous fungal disease caused by dermatophytes

Which three diseases are caused by cutaneous mycoses?

1. Ringworm - Various sites on the body

2. Athlete’s foot - Foot

3. “Jock itch” - Genitalia

Wha ttype of organism is responsible for Leishmania

Protozoa

What is the vector for Leishmania?

Female sandfly

What are the three manifestations of Leishmania?

• Cutaneous: large, painless skin lesions

• Mucocutaneous: Skin lesions enlarge to encompass mucous membranes

• Visceral: Parasite is spread by macrophages throughout body  Infected macrophages stimulate inflammatory responses  FATAL

Leishmania is the causative agent

What is the causative agent for Leishmaniasis?

Leishmania

What is kala azar?

Visceral leishmaniasis

Typically fatal in 100% of untreated cases. In this disease, macrophages spread the parasite to the liver, spleen, bone marrow, and lymph nodes. Inflammation, fever, weight loss, and anemia increase in severity as the disease progresses. Visceral leishmaniasis is becoming increasingly problematic as an opportunistic infection among AIDS patients.

Rubeola is another term for which disease?

Measles

High fever, cough, runny nose, conjunctivitis, Koplik spots

Which would cause birth defects? Rubella or Rubeola?

Rubella

What are two terms for the arachnid that causes scabies?

1. Sarcoptes scabiei

2. Itch mite

What happens when female mites lay eggs?

Itching of skin, causing blisters

What is the diagnosis of mites?

Observing mites, eggs, or mainly fecal matter in skin samples.