Microbiology - Chapter 19 (Skin/Wound Disease)

What is the Skin Microbiota?

Normally harmless microbes present on the skin, which can compete with potential pathogens for nutrients and space

What causes body odor?

Waste products of the skin's microbiota causes body odor

What makes up the skin microbiota?

Yeast and Bacteria, which may produce disease if it penetrates the epidermis or if the immune system is suppressed

What is the yeast on the skin microbiota?

Yeast: Malassezia

What is the bacteria on the skin microbiota?

Bacteria: Staphylococcus, micrococcus, and the diphtheroids

What are diptheroids shape-wise?

They are Pleomorphic (takes multiple shapes)

What can the skin microbiota do that is harmful?

It could produce disease if the epidermis is penetrated or immune system is suppressed

What is folliculitis?

Infection of a hair follicle, also known as a pimple. Spread of infection into other tissues can causes furuncles.

What are furuncles?

large, tender, swollen areas caused by a staphylococcal infection around hair follicles or sebaceous glands; boils

What is folliculitis at the eyelid base?

A sty

What is it when multiple furuncles grow together?

Carbuncles, which might lead to bacteria in the blood

What is bad about Carbuncles?

They are clusters of boils/furuncles that have access to the lower dermis/hypodermis (highly vascular)

This might cause diseases to become systemic

What is the common cause for pus in pimples?

Staph. aureus, which can cause disease

What is bacteremia?

Presence of bacteria in the blood stream

What are the pathogen/virulence factors of folliculitis?

It is most commonly caused by Staphylococcus (gram POS bct., cocci, clusters, salt tolerant)

What are two species of Staphylococcus that are commonly found on the skin?

Staphylococcus epidermidis
Staphylococcus aureus

What is the pathogenesis of folliculitis?

Staphylococcus that's transmitted through contact or fomites

What is bactermia?

Bacteria can spread into the blood and move to organs beyond the skin

an example could be folliculitis

What is the virulence factor of Coagulase for S. Aureus?

Positive

What is the virulence factor of Stahylokinase for S. Aureus?

Positive

What is the virulence factor of Lipase for S. Aureus?

Positive

What is the virulence factor of Beta-Lactamase for S. Aureus?

Present in 90% of strains

What is the virulence factor of Coagulase for S. Epidermidis?

Negative

What is the virulence factor of Staphylokinase for S. Epidermidis?

Negative

What is the virulence factor of Lipase for S. Epidermidis?

Positive

What is the virulence factor of Beta-Lactamase for S. Epidermidis?

Negative

What are factors that inhibit phagocytosis in S. Aureus?

1) Polysaccharide Slime Layer
2) Protein A on cell surface

Does a polysaccharide slime layer play a role in virulence for S. epidermidis?

Yes

Does a Protein A play a role in virulence for S. epidermidis?

No

What are the toxins for virulence in S. Aureus?

• Cytolytic toxins
• Leukocidin
• Epidermal cell differentiation inhibitor

What are the virulence factors that are present in some strains for S. aureus?

• Exfoliative Toxin
• Toxic shock syndrome toxin

What are the virulence factors regarding toxins in S. epidermidis?

nothing

What does coagulase do to bacteria?

Forms a clot around the bacteria, hiding it from the immune system

(when it appears, produces kinase to break down the clot)

What does Lipase do for virulence factors?

Breaks down lipids and fats

What does Beta-lactamase do for virulence factors?

S. aureus can produce beta-lactamase which is resistant to antibiotics

What do cytolytic toxins do?

Kills cells in general

What does leukocidin do?

Kills leukocytes specifically

What does the exfoliative toxin do?

It causes the whole external layer of a person's skin to peel right off, not painful, but can make you prone to secondary infection/super infection

What is Toxic Shock Syndrome Toxin?

It is a superantigen which can lead to a cytokine storm

What are signs and symptoms of Staphylococcal Scalded Skin Syndrome?

The skin becomes red and wrinkled and forms blisters, while

outer epidermis peels off in sheets.

What are the pathogen/virulence factors of Staphylococcal Scalded Skin Syndrome?

They only exist in some S. aureus strains, and only 1-2 different exfoliative toxins cause SSSS

What are signs and symptoms of SSSS?

No scarring, because the dermis is unaffected

What are signs and symptoms of Impetigo (Pyoderma)?

Impetigo causes red patches to form on face and limbs, crusting

What are Impetigo (Pyoderma) and Erysipelas caused by?

Mostly caused by S. aureus

Sometimes caused by Strept. pyogenes

What is bullous impetigo?

When there's blistering

What is non-bullous impetigo?

No blistering, just dry (little pain, non scaring)

What are signs and symptoms of Erysipelas?

Infection spreads to the lymph nodes, leading to inflammation, painful.

What is Streptococcus pyogenes?

Gram-positive coccus, arranged in chains, and virulence factors add to impetigo

What does a catalase test do to Strep Pyogenes?

Strep Pyogenes is negative for catalase

What does adding Hydrogen Peroxide do to Strep Pyogenes?

It will produce oxygen as it breaks down H2O2

What are the virulence factors of Impetigo?

• M protein
• Hyaluronic acid capsule
• Pyrogenic toxins

What does the M protein do?

Destabilizes complement and interferes with phagocytosis

What happens when the complement is destabilized?

It WON'T start a cascade and DOESN'T poke holes in a pathogen (perforin/granzyme maybe)

What happens when phagocytosis is interfered?

The macrophage will be ignored or will be let go

What does the Hyaluronic acid capsule do?

Hides bacteria

What does Pyrogenic toxins do?

Activates immune system cells, leading to inflammation

What are the pathogen/virulence factors of Necrotizing Fasciitis?

Mostly caused by S. pyogenes

• exotoxin A and streptolysin S damages cells and tissues

-Hyaluronidase, streptokinase, DNAase, and M protein

What does Hyaluronidase do for Necrotizing Fasciitis?

It breaks down the junction in between cells

What does Streptokinase do for Necrotizing Fasciitis?

It breaks down clots

What does DNAase do for Necrotizing Fasciitis?

digests DNA

What level of skin does impetigo affect?

Epidermis

What level of skin does Erysipelas affect?

Superficial Dermis (Papillary Dermis)

What level of skin does Cellulitis affect?

Deep Dermis (Reticular Dermis)

What is cellulitis?

A serious condition needing IV and antibiotics, which is vascularized,

allowing it to become systemic

What is the order of skin infections?

It starts with impetigo, could develop into erysipelas, then into cellulitis, until it becomes necrotizing fasciitis

What is Necrotizing Fasciitis?

Flesh Eating disease leading to tissue death

What is the pathogenesis and epidemiology of Necrotizing Fasciitis?

S. pyogenes enters through breaks in the skin

What is the diagnosis, treatment, and prevention of Necrotizing Fasciitis?

Treat it with clindamycin and penicillin, and in worse cases

surgery to remove infected tissueH

How do you tell if you need to treat Necrotizing Fasciitis?

If you draw a border and it goes beyond the line it needs to be treated ASAP

What is a bacteria that can cause Necrotizing Fasciitis?

Vibrio Vulfinicus

What is Acne?

A pathogen caused by either Propionibacterium (85%) or

Can be caused by S. aureus

What is propionibacterium?

Gram-positive, rod-shaped diphtheroid, which are commonly found in the skin

What is the epidemiology of acne?

Acne increases during puberty due to it metabolizing/growing Won sebum, and

Propionibacterium are normal microbiota

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

Treated with antimicrobials, UV light (destroying bacteria), or accutane in severe situations

When is accutane used for and how?

It can be used to treat severe acne, as it inhibits sebum production

What are the negative effects of accutane?

Accutane can cause severe birth defects in pregnant women.

What is the first step in the development of acne?

Normal skin, which oily sebum produced by the glands reaches the hair follicle and the pore discharges it onto the skin surface

What is the second step in the development of acne?

White head, which inflamed skin swells over the pore when bacteria infects the follicle, causing bacteria and sebum to colonize and accumulate.

What is the third step in the development of acne?

Blackhead, where dead/dying bacteria and sebum can form a blockage of the pore

What is the fourth step in the development of acne?

Pustule formation, where severe inflammation of the follicle can cause pus to form and rupture, causing cystic acne.

What is cystic acne?

Pus filled lumps under the skin. Cysts can be painful. These cysts can leave scarring.

What are the signs and symptoms of a Psuedomonas infection?

• Fever, chills, and shock caused by a blood infection
• A blue-green pigment may arise known as (pyocyanin)

(may cause NF)W

What does the Blue-green pigment, pyocyanin give off?

It smells like hyacinths, or a flower

What is the causative agent of a Pseudomonas Infection?

Psuedomonas aeruginosa is the causative agent

Why can Pseudomonas Aeruginosa survive in multiple scenarios?

It has a lot of antibiotic resistance due to gram-negative rods, efflux pumps, and how it can survive in soap

Where are the worst places Pseudomonas Aeruginosa be found?

In nosocomial settings (i.e. hospital settings) or isolated patients (i.e. burn patients)

What is Pseudomonas aeruginosa?

Gram-negative bacillus, found from soil, decaying matter, and moist environments

What are the virulence factors of a Pseudomonas infection?

• Fimbriae and Adhesins (biofilm)
• Capsule (attachment and biofilm formation)
• Elastase (breaks down elastic fibers and immunoglobulins)
• Exotoxin A and exoenzyme S (halts protein synthesis)

What is bad about Fimbriae and Adhesins?

Allows the pathogen to adhere to a biofilm, which are known to be antibiotic resistant

What is bad about Capsules?

Protects the bacteria from phagocytosis

What is bad about Elastase?

Breaks down elastic fibers and immunoglobulins

What is bad about Exotoxin A and exoenzyme S?

Stops protein synthesis, causing a shutdown in metabolism, leading to tissue death

What is the pathogenesis of a pseudomonas infection?

• Infection can occur in burns, as bct. grow under burn surface
  -The bacteria kills cells, destroys tissue, and triggers shock

Why is Pseudomonas Aeruginosa dangerous to burn victims?

Bacteria grows under the burn surface, killing cells/destroys tissue/triggers shock

What is the treatment for a Pseudomonas infection regarding burn victims?

Exfoliating/Debridement of burn tissue is required for topical antimicrobials to be effective (combination antimicrobials)

Why is it hard to treat Pseudomonas infection?

Pseudomonas aeruginosa has a multi-drug resistance, requiring multiple to be effective

What is Spotted Fever Rickettsiosis?

Its arthropod-borne rickettsias,

but rocky mountain spotted fever is most severe

What are the signs and symptoms of Spotted Fever Rickettsiosis?

• Non-itchy spotted rash on trunk and appendages
• Organ failure can occur in severe cases

What are the pathogen/virulence factors of Spotted Fever Rickettsiosis?

It's caused by Rickettsia rickettsii (gram-neg, intracellular parasite)

which the pathogen avoids digestion by hiding in the phagosome.

What is the pathogenesis of Rocky Mountain Spotted Fever?

R. rickettsii does not secrete any toxins