Micro 4: Diseases

what are the layers of the skin from superficial to deep?

epidermis, dermis, subcutaneous layer

what are the points of entry in the skin?

wounds

pores

circulation

what are the three skin defenses?

physical blockage

unfavorable environment for microbes

antimicrobial substances

what are the different physical blockages of the skin?

keratin

desquamation (cell sloughing)

how does the skin’s environment discourage microbial growth?

high salt concentration and oils like sebum

what does the skin’s microbiome do?

protects against pathogens by competing for nutrients and space

what microorganisms make up our normal flora?

Staphylococcus epidermis

Corynebacterium diphtheria

Propionibacterium acne

Candida sp. (fungus)

Staphylococcus aureus

what is a lesion?

changes to skin caused by infection

what is a diagnostic indicator?

specific signs a disease may have

what is a macule lesion?

flat and discolored

what is a papule lesion

raised and solid

what is a vesicle lesion?

filled with clear fluid

what is a pustle lesion?

filled the pus = purulent

what is pus?

dead WBC, bacterial, fungal cells

when fluid contains pus, we describe it as purulent

what is an abscess?

deep tissue pustule with decreased blood flow

must be drained to improve blood flow and allow antibiotics to reach the infection site

antibiotics do not penetrate well

why do antibiotics not work well on abscesses?

decreased blood flow prevents antibiotics from reaching the infected area effectively

What are common diagnostic lab tests for bacterial skin infections?

Culturing on media, Gram staining, and virulence factor testing

What culture medias are commonly used for bacterial skin specimens?

TSA (Tryptic Soy Agar), MacConkey Agar, and Blood Agar

what organism causes acne?

propionibacterium acnes

how is acne treated?

antibiotics

who is mostly affected by acne?

adolescents and adults

what organism causes dermatitis?

pseudomonas aeruginosa

how is pseudomonas dermatitis trasmitted?

contact with contaminated water or soil

what are pseudomonas dermatitis culture/diagnosis features?

non-lactose fermenting, oxidase positive, fruity scent, green pigment

how is pseudomonas dermatitis treated?

antibiotics, though is resistant to many of them so it must be chosen carefully

what organism causes staphylococcal impetigo?

Staphylococcus aureus

how is s. aureus transmitted?

direct or indirect contact

what are the virulence factors of s. aureus?

coagulase, capsule, protein A, exfoliative toxin, TSST-1

how is s. aureus treated?

antibiotics

how is s. aureus diagnosed?

golden colonies, beta-hemolysis, catalase +, coagulase +

how is MRSA transmitted?

direct or indirect contact

what organisms causes MRSA?

methicillin-resistant staphylococcus aureus 

what are the virulence factors of MRSA?

capsule, coagulase, hemolysins

how can MRSA be prevented?

hygeine practices, vaccine

how is MRSA treated?

hospital associated = vancomycin

community associated = other antibiotics 

who is typically infected by MRSA?

hospital associated: nursing homes and inpatients

community associated: children and young adults

what is the difference between HA and CA MRSA strains?

both have macA gene (methicillin resistance)

HA = resistant to all but vancomycin

CA = sensitive to many antibiotics; contains PVL gene as an extra
virulence factor

what is a toxemia?

toxin enters blood stream but bacteria are not at the symptom site or in the blood

what causes scalded skin syndrome?

s. aureus toxin

who is most affected by scaled skin syndrome?

newborns and young children

what is scalded skin syndrome/what are symptoms?

bacteria colonized in intestine of newborns/children

toxin enters bloodstream and causes skin to peel off in sheets

what causes staphylococcal toxic shock syndrome (TSS)?

s. aureus toxin: TSST-1

what are symptoms of TSS?

fever, rash, skin shedding

what organism causes streptococcal impetigo?

streptococcus pyogenes (group A streptococcus - GAS)

how is s. pyogenes identified?

catalase negative

beta-hemolysis

group A typing

how is s. pyogenes transmitted?

direct or indirect contact

how is s. pyogenes treated?

antibiotics

what are s. pyogenes virulence factors?

capsule

M protein

SPE A and SLO toxins (causes toxemias)

what severe diseases can GAS cause?

necrotizing faciitis

GAS toxic shock syndrome

how is GAS TSS treated? 

antibiotics are a must because there is a potential for infection complications like rheumatic fever 

what organism causes cutaneous anthrax?

bacillus anthracis

how is cutaneous anthrax transmitted?

direct contact with endopores

how might cutaneous anthrax be prevented?

vaccine

how is cutaneous anthrax treated?

antibiotics

what is an exanthem?

widespread rash caused by a viral infection, usually in children

what are key features of exanthems?

caused by respiratory viruses 

vaccines are live attenuated 

what causes measles (rubeola)?

measles virus

what are symptoms of measles?

macular rash, fever, cough, koplik spots

what are koplik spots?

red patches with white centers

(diagnostic indicator for measles)

what might measles cause?

pneumonia, immune amnesia, subacute sclerosing panencephaltitis (SSPE)

how is measles transmitted?

respiratory

what are virulence factors of measles?

immune amnesia, very highly contagious

how is measles prevented?

MMR vaccine (live attenuated)

what causes rubella (german measles)?

rubella virus

what are signs of rubella?

macular rash

how is rubella transmitted?

repiratory

how can we prevent rubella?

MMR vaccine

what is congenital rubella syndrome?

mother in infected in first trimester of pregnancy and virus is transferred to fetus

this may cause miscarriage, still birth, or birth defects

what causes roseola?

human herpesvirus 6 (HHV 6)

how is roseola transmitted?

respiratory

how can we prevent roseola?

there is no prevention

what causes chickenpox (varicella)?

varicella-zoster virus

what causes shingles (zoster)?

varicella-zoster virus

what are signs of chickenpox?

rash with vesicles

how is chickenpox prevented?

live attenuated vaccine

how might chickenpox lead to shingles?

virus going latent in nerve cells and is reactivated and travels to skin

what are signs of shingles?

vesicles erupt 

who typically is affected by shingles?

adults over 50

how is shingles prevented?

shingles-specific, subunit vaccine

what causes fifth disease?

parvovirus B19

what are signs of fifth disease?

“slapped cheek” rash and respiratory symptoms

how is chickenpox transmitted?

respiratory

how is fifth disease transmitted?

respiratory 

what are the different exanthem diseases?

measles, rubella, roseola, chickenpox/shingles, and fifth disease

what causes cold sores and cutaneous herpes?

herpes simple virus 1 (HSV-1)

what are signs of cold sores and cutaneous herpes?

vesicular rash

how is herpes virus transmitted? 

direct contact

what is a virulence factor of herpesvirus?

virus goes latent in nerve ganglion

how is cutaneous herpes prevented?

avoid contact, there is no vaccine

what causes hand, foot, and mouth disease (HFMD)?

coxsackievirus 16

how is HFMD transmitted?

direct contact

what is a sign of HFMD?

vesicular rash

what does enterovirus do?

infects the gut

coxsackievirus 16 is an enterovirus that causes HFMD

what causes warts?

HPV

how are warts transmitted?

direct contact 

what is a sign of warts?

rough papules

what are mycoses?

another name for fungal diseases

what causes ringworm?

dermatophytes

how is ringworm transmitted?

direct contact

what is a sign of ringworm?

itchy and round maculopapular rash