MICP

Types of skin lesions

Macule
Papules
Plaques
Nodules
Urticaria (wheals or hives)
Vesicles
Bullae
Pustules
Purpura
Petechiae
Ecchymosis
Ulcer
Eschar

Macule

- Flat lesions
- change in color of affected skin

Papules

- Raised lesion
- solid
- less than 5mm in diameter

Plaques

- flat with elevated surface (plateau like)
- more than 5 mm diameter

Nodules

- rounded raised lesions
- more than 5 mm in diameter

Urticaria (wheals or hives)

- annular or ring like papules or plaques
- with pinkish color

Vesicle

- circumscribed fluid filled lesions
- less than 5 mm in diameter

Bullae

- circumscribed fluid filled lesions
- more than 5 mm in diameter

Pustules

- circumscribed
- exudate filled lesions

Purpura

skin lesions due to bleeding into the skin

Petechiae

- type of purpura
- less than 3mm in diameter

Ecchymosis

- type of purpura
- more than 3mm in diameter

Ulcer

- craterlike lesion that may involve the deeper layers of the epidermis and dermis

Eschar

- necrotic ulcer covered with a blackened scab or crus

Bacterial SKIN infections

Staphylococcus aureus
Staphylococcus epidermis
Streptococcus pyogenes
Pseudomonas aeruginosa
Clostridium perfringens
Bacillus anthracis

Staphylococcus aureus

- common pathogen in humans
- gram positive cocci
- arranged individually, pairs, short chains, clusters
- FOUND in the SKIN and NASOPHARYNX
- produce gray or golden yellow colonies
- coagulase positive
- catalase positive
- produces enzymes and toxins responsible for invasiveness and pathogenicity
- most dangerous among all common staphylococcus

Mode of transmission of Staphylococcus aureus

- Direct contact
- person having purulent lesions
- hands of healthcare of hospital workers
- fomites

Clinical findings of Staphylococcus aureus

Folliculitis
Furuncle
Carbuncle
Sty or Hordeolum
Impetigo
Staphylococcus scalded skin syndrome (Ritter's disease)

Folliculitis

pyogenic (pus producing)
- involves the hair follicle
- localized pain inflammation
- heals rapidly after draining the pus

Furuncle (boil)

- extension of folliculitis
- larger and painful nodules
- underlying collection of dead and necrotic tissue

Carbuncle

- coalescence of furuncles
- extends to subcutaneous tissue with multiple sinus tracts

Sty or Hordeolum

- folliculitis occurring at the base of the eyelids

Impetigo

- common in young children
- INVOLVES the FACE and LIMBS
- starts as flat red spot (macules) later becomes pus-filled vesicle \= ruptures form crust
- can be caused by S. AUREUS and S. PYOGENES

Stapylococcal scalded skin syndrome (Ritter's disease)

- found in newborns and young children
- sudden onset of perioral (surrounding the mouth) erythema, covers body in 2 days
- slight pressure applied \= skin displacements \= postivie NIKOLSKY SIGN
- bullae and cutaneous blister will follow later under go desquamation (peeling of the skin)
- antibodies are produce after 7 to 10 days
- only outer layer of epidermis is affected, no scarring.

Exfoliative toxin

- toxin responsible for manifestation in staphylococcal scalded skin syndrome.

Laboratory Diagnosis of Staphylococcus Aureus

LABORATORY IDENTIFICATION
- microscopic examination of gram stained specimen (gram - positive cocci)
- culture (gray and golden yellow (20- 25 C)

Catalase POSITIVE Quality of Staphylococcus Aureus

Differentiate it from Streptococci

Coagulase POSITIVE Quality of Staphylococcus Aureus

Differentiate it from other forms of Staphylococcus

Treatment and Prevention

- treatment of choice is BETA-LACTAM ANTIBIOTICS like PENICILLIN
- S. Aureus develop resistance to penicillin and other penicillin derivatives (methicillin and nafcillin)
- OXACILLIN only penicillin derived antibiotic ACTIVE against S. aureus
- incision and drainage of skin is necessary

Staphylococcus Epidermidis

- part of the normal flora of the skin
- commonly associated with "stitch abscess", UTI, and endocarditis
- causes infections in individual with PROTETICS

Streptococcus pyogenes

- gram positive cocci
- arrange in pairs or in chains
- belongs to group A streptococci
- beta hemolytic (cause rupture of blood)
- produces enzymes and toxins to protect from phagocytosis
- associated with sever systemic infection

Major virulence factor of Streptococcus pyogenes

M protein (anti-phagocytic)

Mode of transmission of Streptococcus pyogenes

- Direct contact
- infected person
- fomites

Clinical Findings

- Pyoderma (Impetigo)
- Erysipelas (St. Anthony's Fire)
- Cellulitis
- Necrotizing Fasciitis (flesh eating or streptococcal gangrene)

Pyoderma (Impetigo)

- purulent skin infection
- localized common involves FACE, UPPER and LOWER EXTREMITIES
- vesicle \> pustules \> rupture \= honey-colored crust
- may have enlargement of lymph node
- NO SIGN F SYSTEMIC INFECTION

Erysipelas (St. Anthony's Fire)

- follows respiratory tract or skin infection caused by s. pyogenes
- DISTINCT FROM NORMAL SKIN

Manifestation of Erysipelas (St. Anthony's fire)

- localized areas with pain
- erythema
- warmth
- systemic manifestations -lymphadenopathy

Cellulitis

- involves SKIN and SUBCUTANEOUS TISSUE
- NORMAL SKIN NOT CLEARLY DIFFERENTIATED

Manifestation of cellulitis

- local inflammation with systemic signs

Necrotizing Fasciitis (flesh eating or streptococcal gangrene)

- involves DEEP SUBCUTANEOUS TISSUE
- cellulitis \> bullous and gangrenous \> spread to fascia \> muscle and fat
- become systemic and cause multi-organ failure leading to death

Complications of Streptococcus Pyogenes

- Acute glomerulonephritis
- Rheumatic fever
- Scarlet fever
- non- supporative, immune
mediated complications

Acute glomerulonephritis

commonly associated with skin infections

Rheumatic fever

associated with s. pyogenes throat infection

Scarlet fever

- develops in some people who have strep throat.
- manifested by STRAWBERRY TONGUE
- bright red rash that covers most of the body, sore throat and fever

Laboratory diagnosis of Streptococcus Pyogenes

- Microscopy
- Culture
- Bacitracin test

Microscopy of Streptococcus Pyogenes

- infected tissue will show gram-positive cocci in pairs and chains associated with leukocytes

Culture of Streptococcus Pyogenes

- positive beta hemolysis in blood agar

Bacitracin test of Streptococcus Pyogenes

- antibiotic susceptibility test with (+) zone of inhibition of growth around
the Bacitracin disc.

Treatment and Prevention of Streptococcus Pyogenes

- DOC (drug of choice): PENICILLIN
- Alternate drugs: macrolides (erythromycin,
azithromycin) or cephalosporin
- drainage of pus through debridement

Pseudomonas aeruginosa

- gram negative bacilli
- arranged in PAIRS ENCAPSULATED
- opportunistic pathogen
- common cause of NASOCOMICAL INFECTIOSN
- capable of producing water soluble PIGMENTS (pyocyanin - blue)
- resistant to most antibiotic
- affects extensive skin burns

Virulence of Pseudomonas aeruginosa

- ADHESINS (flagella, pili. LPS, alginate)
- TOXINS (exotoxin A, pigments)
- ENZYMES

Mode of transmission of Pseudomonas aeruginosa

colonization of previously injured skin

What does Pseudomonas aeruginosa cause to wearers of contact lenses

corneal keratitis

What does Pseudomonas aeruginosa cause to intravenous drug abusers

endocarditis and osteomyelitis

What does Pseudomonas aeruginosa cause to healthy individuals?

external otitis (swimmer's ear)

What does Pseudomonas aeruginosa cause to diabetics

severe external otitis

Clinical Findings of Pseudomonas aeruginosa

- BLUE-GREEN pus that exudes a SWEET GRAPE-like odor
- folliculitis and secondary infections in individuals with acne
- nail infections from immersion in contaminated water
- Osteochondritis

Osteochondritis in Pseudomonas aeruginosa

- one of the clinical finding of Pseudomonas aeruginosa
- most common cause of inflammation of the bone and a cartilage of the foot following a penetrating injury

Laboratory Diagnosis of Pseudomonas aeruginosa

GRAM STAINING: gram negative bacilli, individual or in pairs
CULTURE: flat colonies with green pigmentation with sweet grape like odor
OXIDASE TEST: Positive, aerobic and can use oxygen as a terminal electron acceptor in respiration.

Acronym AERUGINOSA

A: aerobic
E: Exotoxin A
R: Rod/ resistance
U: UTI, burns, injuries
G: green-blue dressing
I: iron-containing lesions
N: negative gram
O: odor of grapes
S: slime capsule sometimes
A: Adherin pili

Treatment and prevention of Pseudomonas aeruginosa

- resistant to most antibiotics, culture and sensitivity must be done
- prevent contamination of sterile hospital equipment and instruments
- prevent cross-contamination of patients by hospital personnel

Clostridium perfringens

- gram positive bacilli
- anaerobic
- rarely produce endospores
- widely distributed in nature
- associated with soil and water contaminated feces

4 lethal toxins produced by Clostridium perfringens

- ALPHA
- BETA
- IOTA
- EPSILON

Most lethal toxin produced by Clostridium perfringens

ALPHA TOXIN
- acts as LECITHINASE cause lysis of erythrocytes (RBC), platelets, and leukocytes (WBC)
- cause massive hemolysis
- bleeding and tissue destruction

Mode of transmission of Clostridium perfringens

- the colonization of the skin following physical trauma or surgery

Clinical findings of Clostridium perfringens

- cellulitis
- suppurative myositis
- myonecrosis or gas gangrene

Suppurative myositis in Clostridium perfringens

- acute intramuscular infection that develops secondary to hematogenous microorganism spread into the body of skeletal muscle, manifested by abscess formation of large muscle groups

Myonecrosis or Gas gangrene

- life threatening infection following physical trauma or surgery
- characterized by massive tissue necrosis with gas formation, shock, renal failure, and death within two days of onset.

Laboratory diagnosis of Clostridium perfringens

MICROSCOPIC: gram-positive bacilli in pairs
CULTURE: grow under anaerobic condition

Treatment and Prevention of Clostridium perfringens

- Surgical wound debridement
- high dose penicillin therapy

Bacillus Anthracis

- gram positive bacilli
- arrange individually or in pairs or long serpentine chains describe as "bamboo fishing rod" or "medusa's head"
- aerobic, spore forming, encapsulated
- can affect SKIN, LUNGS, GASTROINTESTINAL TRACTS
- can be used in bioterrorism
- produces ANTHRAX TOXIN resulting in an ulcer with a black eschar.
- deadly disease to livestock and, occasionally, to humans.
- only permanent (obligate) pathogen within the genus Bacillus.
- Endospores survive in soil tests for up to 60 years

Virulence of Bacillus Anthracis

POLYPEPTIDE CAPSULE
- responsible for evading phagocytosis
EDEMA and LETHAL TOXINS
- both inhibit the host's immune response

LETHAL TOXINS
- targets and kills
macrophages, which disables
an essential defense of the
host

EDEMA TOXIN of Bacillus Anthracis

local edema (swelling) and interferes with phagocytosis by
macrophages

LETHAL TOXIN of Bacillus Anthracis

targets and kills macrophages, which disables an essential defense of the host

Mode of transmission of Bacillus Anthracis

- inoculation into open skin from either soil or infected animal products
- ingestion of infected meat or milk
- inhalation of aerosolized spores

Clinical Findings of Bacillus Anthracis

- disease of the herbivores (sheep and cattle)
- people at risk are those who handle animals, hides wool

3 form of Anthrax Disease

Cutaneous anthrax
Pulmonary anthrax
Gastrointestinal anthrax

Cutaneous anthrax (skin infection)

- most common form
- painless papule at site of inoculation \> ulcerative \> develop necrotic eschar
- associated with painful lymphadenopathy and edema.

Laboratory diagnosis of Bacillus Anthracis

GRAM STAINING: peripheral blood contains a large number of B. anthracis
BLOOD TEST: detects inhalation and cutaneous cases of anthrax within an hour
CULTURE: spores observe only in low carbon dioxide tension
DEMONSTRATION of spores can be done through DORNER STAIN or WIRTZ CONKLIN STAIN

Treatment and prevention of Bacillus Anthracis

DOC: PENICILLIN and DOXYCYLINE
- CIPROFLOXACIN recommended in RESISTANT CASES
- prevention through VACCINATION ANIMALS (1 dose, live attenuated vaccine)
- VACCINATION HUMANS: individual at risk such as animal handlers, military personnel, slaughter houses (1 dose, inactivated antigen)
- 3 doses over 4 weeks of vaccine to persons exposed to Bacillus Anthracis

Patient care of Bacillus anthrax

- Standard Precautions
- Add Contact Precautions for cutaneous anthrax patient if there is a large amount of uncontained drainage.
- Use soap, water for handwashing; alcohol does not have sporicidal activity.

Fungal Skin infections

Superficial Mycoses
Cutaneous Mycoses or Dermatophytosis
Subcutaneous Mycoses

Superficial Mycoses

Tinea Versicolor (Pityriasis versicolor)
Tinea Nigra

Tinea Versicolor (Pityriasis versicolor)

- caused by Malassezia furfur (Pityrosporum orbiculare)
- more common in tropical regions
- appear in FACE, NECK TRUNK, ARMS

Malassezia furfur (Pityrosporum orbiculare)

- causes Tinea versicolor
- normal flora of the skin
- found in areas rich in sebaceous glands

Lesions of Tinea versicolor (Pityriasis versicolor)

- irregular
- discrete hypo- or hyperpigmented macules
- scaly with a dry, chalky appearance

Laboratory diagnosis of Tinea versicolor

Microscopic: visualization of "spaghetti and meatball" appearance of M. furfur with ALKALINE STAIN OF 10% KOH or NaOH
DEMONSTRATED with Periodic AcidSchiff stain (PAS stain) or hematoxyllineosin stain (H & E stain)

Treatment of Tinea versicolor

- application of KERATOLYTIC AGENTS containing SELENIUM DISULFIED or SALICYLIC ACID
- topical ANTIFUNGAL drugs like KETOCONAZOLE

Tinea Nigra

- caused by caused by Hortaea werneckii (formerly Exophiala werneckii)
- appears in PALMS and SOLES
- common in tropical and subtropical regions
- seen in ADOLESCENTS, YOUNG ADULTS, FEMALES

Hortaea werneckii (formerly Exophiala werneckii)

- causes tinea nigra
- dematiaceous fungus
- produces melanin and grows as mold producing ANNELIDS or ANNELLOCONIDIA

Lesions of Tinea Nigra

- gray to black
- well demarcated macules

Diagnosis of Tinea Nigra

MICROSCOPIC: skin scraping with potassium hydroxide
CULTURE: Sabouraud's dextrose agar medium

Treatment of Tinea Nigra

- similar to tinea versicolor
- application of KERATOLYTIC AGENTS containing SELENIUM DISULFIED or SALICYLIC ACID
- topical ANTIFUNGAL drugs like KETOCONAZOLE

Cutaneous Mycoses or Dermatophytosis

- fungal infection involving keratinized body structures SKIN, HAIR, NAILS
- caused by group of fungi called DERMATOPHYTES

Dermatophytes

- produce keratinase
- keratinophilic and keratinolytic

Keratinase

- enzyme capable of breaking down keratin

3 genera that cause infection of Cutaneous mycoses or Dermatophytosis

Microsporum
Trichophyton
Epidermophyton

Microsporum

- infect the HAIR and NAILS only
- produces both MICROCONIDIA and MACROCONIDIA
- predominant MACROCONIDIA

Trichophyton

- infect SKIN, HAIR, NAILS
- produces predominant MICROCONIDIA

Epidermophyton

- infect the SKIN and NAILS only
- produces SMOOTH-WALLED MACRONIDIA in bundles of 2 and 3