Micro: skin and eye infections

the skin protects underlying tissues from ____ ______

microbial colonization

epidermal layer of skin has

keratinocytes and dendritic (Langerhans) cells

where are keratinocytes produced

stratum basale

where do keratinocytes die

stratum corneum

the dermal layer of the skin has

sweat glands and sebaceous glands

the microbiota of sebaceous sites:

the lowest bacterial diversity (Staph and Cutibacterium)

the microbiota of moist sites on the skin:

Staphylococcus and Cornyeobacterium

the microbiota of dry sites on the skin:

the highest diversity - S. epidermidis and Gm- species

(Forearm, leg, hand)

what is the most common skin disease

acne

what causes acne

Cutibacterium acnes

what is the abx of choice for acne

tetracyclines

what is the pilosebaceous unit

hair follicle and sebaceous gland

Biofilm

any group of microorganisms in which cells stick together and adhere to a surface

____ and ____ climates can lead to endogenous skin infections

warm and humid

Staphylococci are

-gram positive spheres

-clustered arrangements

where are staphylococci found

skin, mouth, nose and throat

what species of Staphylococci cause disease?

S. aureus (MRSA and MSSA)

S. epidermidis

S. saprophyticus (UTIs)

what are some diseases that Staphylococci cause?

-skin infections

-pneumonia

-surgical site infections

-UTI

-bone and joint

-meningitis

S.aureus is catalase and coagulase what?

Catalase (+)

Coagulase (+)

the catalase test is used to distinguish between

staphylococci from streptococci and enterococci

the coagulase test distinguishes

s.aureus from other staphylococcus

Staphylococci produce catalase, which converts ___ ____ to water and oxygen

hydrogen peroxide (H2O2)

coagulase reacts with

prothrombin in the serum -> convert fibrinogen to fibrin -> clots -> evades phagocytosis by macrophages

what are the two lab tests for Staphylococci

catalase and coagulase

Staphylococcus aureus: MRSA

methicillin-resistant S. aureus (mecA+)

what makes MRSA methicillin resistant?

-mecA codes a new penicillin binding protein (PBP-2a)

-PBPs are the target of beta-lactam antibiotics

-mecA is what makes it methicillin-resistant

Staphylococcus aureus: MRSA is resistant to what

all beta-lactams/cephalosporins

-except ceftaroline and ceftobiprole

abx of choice MRSA

vancomycin

Staphylococcus aureus: MSSA

methicillin-susceptible S. aureus (mecA-)

abx of choice MSSA

nafcillin

healthcare associated MRSA happens how many hours following hospitalization?

48 hours

localized skin infections caused by Staphylococcus

-Abscess (confined pus-filled lesion on skin)

-Folliculitis (pus-filled pocket at base of hair follicle)

-Furuncle (boil) (infection further down hair follicle)

toxin generated diseases caused by Staphylococcus

Impetigo

Scalded skin syndrome

Toxic shock syndrome (TSS)

carbuncle

a cluster of connected furuncles (boils)

Streptococci

-gram-positive bacteria

-grow in chains

what are the two classification systems of Streptococci

Hemolytic groups (behavior on blood agar) and variants of cell wall carbohydrates

Hemolytic groups

Alpha-hemolytic (olive green)

Beta-hemolytic (clear zone)

Gamma-hemolytic (no change)

what is Group A streptococci (GAS) caused by

S. pyogenes

abx of choice for Group A streptococci

penicillin G or V

(Cephalosporin - 1st gen)

Group B streptococci is caused by

S. agalactiae

Abx of choice for Group B streptococci

penicillin G or V

(Cephalosporin - 1st gen)

Group A streptococci (S. pyogenes) causes

-streptococcal pharyngitis (strep throat)

-cellulitis (nonpurulent)

-erysipelas

-Streptococcal toxic shock syndrome

-necrotizing fasciitis

Cellulitis

nonpurulent - severe infection of dermis and subcutaneous tissue

-caused by S. pyogenes

Erysipelas

superficial form of cellulitis of dermis

-caused by S. pyogenes

Gas gangrene or myonecrosis is caused by:

Clostridium perfringens

-anaerobic, Gm+, spore forming rod

-foul odor, intense pain, swelling, black skin

tx: surgery and antibiotics

Cutaneous anthrax is caused by

B. anthracis

-facultative anaerobe, gram-positive rod

tx: antibiotics (ciprofloxacin)

wound cellulitis is caused by

P. aeruginosa, Gm-, aerobic

tx: debridement and antibiotics

abx combo of choice for gas gangrene

penicillin G/VK + clindamycin

Pasteurellosis is caused by

Pasteurella multocida

-Gm- dog or cat bites

treatment of Pasteurellosis

penicillin

Cat-Scratch disease is called by

Bartonella henselae

Cat-Scratch symptoms

-red-crusted blisters, headache, malaise, and low-grade fever, swollen lymph nodes (lymphadenitis - only in some patients)

-hepatosplenic, neurological, or ocular involvement is possible

abx of choice for cat-scratch disease

azithromycin

-if only have lymphadenitis

-antibiotics for 2-4 months

HSV-1

cold sore

-transmitted via contact with lesion or saliva

after primary infection, the HSV-1 become latent in ____ _____

sensory ganglia

trmt of choice for HSV-1

acyclovir

varicella-zoster virus produces

chickenpox and can return to cause shingles

-latent infection in sensory nerve ganglia

chickenpox morphology

red, itchy rash that spreads across the entire body -> turns into fluid-filled vesicles that will break open and yield highly infectious fluid

what is the common complication with chickenpox and some less common complications

bacterial infection of the skin

-Pneumonia, encephalitis, or Reye syndrome can occur

what don't you give kids with a fever?

aspirin

how is chickenpox transmitted?

skin contact and respiratory droplets

(highly communicable disease)

what is the chickenpox vaccine called

Varivax

trmt of choice for VZV

acyclovir

after primary infection, the VZV become latent in ____ _____

nerve cells

Shingles - reactivated

can remain in nerve cells for many years

-if they are reactivated, they can travel to the body trunk and cause blisters and red patches

-can cause facial paralysis and severe "ice-pick" pains

Postherpetic neuralgia

the persistence of shingles pain for years after the blisters have disappeared

-occurs in dermatomes

Dermatomes

areas of skin innervated by single spinal nerve

trmt of choice for shingles

acyclovir

Human Herpes virus 6 causes

-roseola infantum, marked with high fever and red rash

-in infants

-many bones marrow transplant recipients suffer an HHV-6B viremia after transplantation

researchers believe that HHV-6 lies dormant for years and may be associated with _____ _____ later in life

multiple sclerosis

HHV-6 is spread through ___

respiratory secretions or saliva

what herpes viruses are oncogenic?

HHV4 and HHV8

Epstein-Barr virus (EBV)

causes mono - HHV4 "kissing disease"

EBV symptoms

fever, sore throat, enlarged lymph. nodes

EBV infection in immunocompromised patients....

tumor formation formed from continued proliferation of infected B cells

-Burkitt lymphoma

Mono is spread via __

saliva

Kaposi sarcoma-associated herpes virus

angiogenic tumor of the blood vessel walls

-caused by HHV-8, forming dark or purple skin lesions

Kaposi sarcoma is most commonly seen in ____ and transmission is unclear but most likely ___

immunocompromised individuals; sexual

Measles (rubeola)

-highly contagious

-caused by a member of the paramyxoviridae family

-red rash begins as maculopapules - starts on face spreads to the trunk/extremities

-transmission through respiratory droplets

-Koplik spots: red patches with white grain-like center that appear on gum line

Measles complications

-bacterial disease in the respiratory tissue

-encephalitis

tx for measles

supportive - fluids, antipyretics, antibiotics if secondary infection

Rubella

(German measles)

-like measles, its transmitted through respiratory droplets

-caused by member of the Togaciridae family

-acute, mildly infectious disease

Rubella symptoms

occasional fever and pale-pink maculopapular rash

tx for Rubella

- supportive - fluids, antipyretics, topical steroids, oral antihistamines

- recovery is usually prompt, but relapses can occur

Congenital rubella

occurs when the fetus is infected through the placenta

-children can be born with eye, ear, and heart problems

Fifth Disease (Erythema Infectiosum)

-caused by parvovirus B19

-Erythroparovirus targets red blood cells

-transmission occurs through respiratory droplets

-fiery rash on cheek, ears, and trunk ("Slap Cheek")

-adults can experience symptoms similar to those of rheumatoid arthritis - due to immune complexes

HPV infections cause

warts

-benign skin growths

- transmitted by contact with affected person or contaminated object

Smallpox is caused by the _______ virus.

variola

Smallpox morphology

-pink-red macules on face & trunk -> become papules and fluid-filled vesicles -> become pustules that break open, emit pus, and leave pitted scars

Smallpox is a focal infection of

skin, intestines, lungs, kidneys and brain

what is one of the most dangerous weapons of bioterrorism?

smallpox

Skin Diseases caused by fungi and parasites

dermatophytosis, sporotrichosis, and leishmania

what is dermatophytosis

an infection of the skin, hair, and nails

-causes cutaneous mycoses

Dermatophytosis clinical presentation

classic appearance surrounded by red, scaly elevated borders

Tinea capitis

ringworm of scalp - infection of skin, hair follicles

-dermatophyte fungus

Tinea corporis

infection of the skin on the trunks or extremities

-dermatophyte fungus

Tinea cruris

infection of proximal thigh/buttocks

"jock itch"

-dermatophyte fungus

Tinea pedis

athlete's foot

-dermatophyte fungus

Tinea unguium

infection of the nail (onychomycosis)

-dermatophyte fungus

Leishmania

cause cutaneous infections

-caused by protozoan

-found in the sand