Med Micro 3 - 1st Line (skin)

Question 1

How have we evolved to deal with such a high level of diversity of microbes?

Answer 1

Very broad first line of defense (innate immunity); recognize lots of antigens specifically, ie certain proteins etc.

Question 2

What is innate resistance?

Answer 2

Resistance to most plant and animal pathogens. Born with it.

Question 3

Why are we resistant to most plant and animal pathogens?

Answer 3

Most of them cannot cross the species barrier, incompatible. (pH, temp, receptors)

Question 4

What is the first line of defense? Goal?

Answer 4

Skin, mucous membrane, chemicals. Goal is to prevent entry of pathogens. Nonspecific defense.

Question 5

What is the second line of defense?

Answer 5

Phagocytosis, complement, interferon, inflammation, fever

Question 6

What is the third line of defense?

Answer 6

Lymphocytes and antibodies

Question 7

How does the skin function to resist bacteria?

Answer 7

Layers, constant shedding. Langerhans (dendritic) cells in epidermis kill foreign by phagocytosis; found around keratinocytes who release cytokines; present antigens to stimulate adaptive immune response

Question 8

How does the dermis resist bacteria?

Answer 8

It has collagen, which gives strength so abrasions do not occur and microbes do not gain entry

Question 9

If infection occurs in skin, what do langerhans cells do?

Answer 9

Take up and process antigens then become fully-functional antigen presenting cells (more to come in other lines of defense)

Question 10

Perspiration

Answer 10

Salt, lysosome (target peptidoglycan), antimicrobial host defense peptides (aka defensins or AMPs): about 40 a.a. with antimicrobiial activity

Question 11

Why are some pathogens more sensitive or more resistant?

Answer 11

Some have enzymes to use (proteases); gram -ve; halophiles;

Question 12

Sebum function

Answer 12

Help keep skin clean and pliable, less likely to break; lowers pH to inhibit many bacteria; contains AMPs and antimicrobial fatty acids

Question 13

Why do we not want to shower every day?

Answer 13

Sebum and sweat mix, make the “acid mantle” which protects with pH 4-5.5

Question 14

Scalded skin syndrome

Answer 14

Caused by exfoliating toxin from S. aureus, common in young children. Breaks down desmoglin in desmosomes b/w skin cells, then infects underneath. Babies don’t have the harder skin needed.

Question 15

Impetigo

Answer 15

Skin infection caused by exfoliating toxin in adults. Caused when skin is damaged and bacteria gain access and start infection. Bacteria responsible is normally on the skin, opportunistic.

Question 16

Profusion

Answer 16

Procedure which uses vacuum to pull stratum corneum apart so creams can penetrate. But so can bacteria. Not healthy.

Question 17

Why should you shower regularly?

Answer 17

Remove bacteria that can cause skin infections. But it also removes the mantle created by sweat and sebum. Balance

Question 18

Who is most susceptible to skin infection and why?

Answer 18

Babies, no defense (skin not hardened), and often sport people who get their skin damaged.

Question 19

Are the skin diseases opportunistic infections?

Answer 19

Yes they are, they result from damage and grant access to bacteria that normally cannot.