MIDTERMS-INFECTIONS OF THE SKIN Flashcards
- is a Gram-positive coccus usually arranged in grapelike clusters.
- Found in the skin and nasopharynx
- Produce enzymes and toxins responsible for its pathogenicity and also through direct invasion and destruction of tissues
Staphylococcus aureus
Skin infections are transmitted through;
- direct contact with a person having purulent lesions,
- from hands of healthcare or hospital workers, and
- through fomites like bed linens and contaminated clothing.
MODE OF TRANSMISSION BY Staphylococcus aureus
- Also known as boil, it’s an extension of folliculitis
- Characterized by larger and painful nodules, with underlying collection of dead and necrotic tissue
Furuncle
- Pyogenic (pus-producing) infection involving the hair follicle
Folliculitis
- Represents a coalescence of furuncles that extends into the subcutaneous tissue with multiple sinus tracts
Carbuncle
- Folliculitis occurring at the base of the eyelids
Sty or Hordeolum
- Primarily a disease of newborns and young children.
- Manifested as an abrupt onset of a perioral erythema (redness) that covers the whole body within two days
Staphylococcal scalded skin syndrome (Ritter’s disease)
- Infection is common in young children and primarily involves the face and limbs
- Initially, it starts as flattened red spot (macule) which later on becomes a pus-filled vesicle that ruptures and forms crust (honey-colored crust).
- May be caused by both S. aureus and S. pyogenes
Impetigo
- Part of normal flora of the skin and is commonly associated with “stitch abscess, UTI and endocarditis.
- It also causes infections in individuals with prosthetic devices
Staphylococcus epidermidis
- are Gram-positive cocci, group A beta-hemolytic (cause complete hemolysis of blood)
- M protein— major virulence factor (anti-phagocytic)
- Produces enzymes and toxins responsible for the pathogenesis of infections caused by the organism
Streptococcus pyogenes
- Is a purulent skin infection that is localized, commonly involving the face and the upper and lower extremities.
- The vesicles rupture and form a honey-colored crust.
Pyoderma (impetigo)
- Soft tissue infections are acquired through direct contact with an infected person or fomite.
MODE OF TRANSMISSION BY Streptococcus pyogenes
- It usually follows a respiratory tract or skin infection caused by S. pyogenes.
- Patients manifest with localized raised areas associated with pain, erythema and warmth
- It is grossly distinct from normal skin
Erysipelas (St. Anthony’s fire)
- non-supporative, immune-mediated complications and skin infections
Acute glomerulonephritis
- Also known as “flesh-eating”
- Involves the deep subcutaneous tissue, then spreads to the fascia, then the muscle and fat
- May become systemic and cause multi-organ failure, leading to death
Necrotizing fasciitis
- Infection involves the skin and subcutaneous tissue, and, unlike erysipelas, the infected and the normal skin are not clearly differentiated
- It is also manifested as local inflammation with systemic signs
Cellulitis
- usually associated with S. pyogenes throat infection
Rheumatic fever
- Colonization of previously injured skin
MODE OF TRANSMISSION by Pseudomonas aeruginosa
- is a gram-negative bacillus that is encapsulated
- capable of producting water-soluble pigments (e.g pyocyanin-blue)
- opportunistic pathogen
- common cause of nosocomial infections (hospital-acquired)
- resistant to antibiotics
Pseudomonas aeruginosa
- is commonly associated with colonization of burn wounds
- characterized by a blue-green pus that exudes a sweet grape-like odor
- Other skin infections: FOLLICULITIS
- Secondary infections: ACNE, NAIL INFECTIONS
Pseudomonas aeruginosa
- Culture shows flat colonies with green pigmentation and a characterized sweet, grape-like odor.
Pseudomonas aeruginosa
preventing contamination of sterile hospital equipment and instruments, and cross-contamination of patients by hospital personnel
TREATMENT AND PREVENTION of Pseudomonas aeruginosa (P. aeruginosa)
- gram-postive bacillus
- anerobic
- capable of producing endospores
- produces four lethal toxins: alpha, beta, iota, and epsilon toxins
- Alpha- most lethal because it causes massive hemolysis, bleeding and tissue destruction
MODE OF TRANSMISSION
* Colonization of the skin following trauma or surgery
CLINICAL FINDINGS
* causes soft tissue infections like cellulitis, suppurative myositis and myonecrosis (gas gangrene)
* Gas gangrene- is a life-threatening infection following trauma or surgery and is characterized by massive tissue necrosis with gas formation, shock, renal failure, and death within 2 days of onset.
LABORATORY DIAGNOSIS
* Microscopic detection of gram-positive bacilli and culture under an anaerobic conditions.
TREATMENT AND PREVENTION
* Surgical wound debridement and high-dose penicillin therapy are the main approaches to the management of the diseases.
Clostridium perfringens
- gram-positive bacilli
- aerobic
- sporeforming
- encapsulated
- arranged in long chains
- characteristics: bamboo rod or medusa head appearance .
MODE OF TRANSMISSION
* inoculation of B. anthracis through break in the skin from either the soil or infected animal products
CLINICAL FINDINGS
* Anthrax is a disease of herbivores.
* The skin infection cutaneous anthrax, is the most common form
* characterized by painless papules at the site of inoculation that becomes ulcerative, and later develops into necrotic eschars.
LABORATORY DIAGNOSIS
* Microscopic examination and culture
TREATMENT AND PREVENTION
* Antibiotics like penicillin or doxycycline are the drugs of choice.
Bacillus anthracis
- Caused by Malassezia furfur (Pityrosporum orbiculare)
- M furfur is part of a normal flora of parts of the body in which the skin is particularly rich in sebaceous glands.
-Diagnosis is made by microscopic visualized of “spaghetti” and meatballs”appearance of M.furfur with alkaline stain.
Tenia versicolor (pityriasis versicolor)
-This infection caused by Exophiala werneckki, a fungus produces melanin.
- Diagnosis is made by direct microscopic examination of skin scrapings with potassium hydroxide and culture using Sabouraud’s dextrose agar medium.
-Treatment same as tinea versicolor
Tinea Nigra
- Fungal infection involving the keratinized structure of the body such as like the skin, hair and
nails.
CUTANEOUS MYCOSES OR DERMATOPHYTOSES
infect the skin hair and nails
Trichophyton-
infect the hair and nails only
Microsporum-
infect the skin and nails only.
Epidermophyton-
also known as athlete foot
Tinea pedis
body
Tinea corporis
scalp
Tinea capitis
groin
Tinea cruris or jock itch
- The infection initially involves the deeper layer of the dermis and subcutaneous tissue later bones.
- The infection are relatively rare exception of sporotriochosis
SUBCUTANEOUS MYCOSES
beard
Tinea barbae
hands
Tinea manus
known as onychomycosis nails
Tinea unguium
- Warts- caused by a DNA virus, the human papillomavirus (family Papovaviruses)
- 70 serotypes
- Capable of transforming infected cells into malignancy
Mode of transmission
* Direct contact through mucousal or skin breaks
* Sexual contact
* Passage through infected birth canal
* Childhood habit of chewing warts
Clinical findings
* Skin warts- benign, self-limiting, proliferations of the skin that regress in time. It may be flat,
dome-shaped, or plantar.
* Genital and anogenital warts- known as condylomata acuminata, STD
Laboratory diagnosis
* Based on gross appearance of the lesions and histologic appearance on microscopic examination that includes hyperkeratosis
Treatment and prevention
* Removal of lesion by: Surgical excision, cryosurgery, electrocautery, application of caustic agents like podophyllin, interferon for genital warts. Prevention is to avoid contact with infected tissue.
Human Papillomarvirus
ü Infection of the body
ü Acquired during wrestling or playing rugby
Herpes gladiatorum
ü Primary infection
ü Caused by HSV-1
ü Presents as vesicles that rupture and ulcerates
ü Lesions- located in the buccal mucosa, palate, gingivae, pharynx, and the tongue
Gingivostomatitis
Etiologic agent
* ______________ virus types 1 and 2
* DNA viruses under the family of herpesvirus
* Capable of latency in the neurons and are capable of recurrent infections
Mode of transmission
* HSV is present in oral and genital secretions and vesicle fluid.
* Transmitted through: oral contact (kissing), fomites (sharing of glasses, toothbrushes and other saliva-contaminated materials), sexual contact, transplacental (during pregnancy), during childbirth
Laboratory diagnosis
* Based mainly on the clinical presentation of the infection
* Can be made using the Tzanck smear to demonstrate the characteristics inclusion bodies known as the Cowdry type A inclusions and other histopathologic changes
* Cell culture but seldom requested
Treatment and prevention
* ACYCLOVIR- drug of choice
* No available vaccine for HSV
Herpes simplex
ü Involving the fingers
ü Caused by both HSV types 1 & 2
Herpetic whitlow
ü Represents recurrent mucocutaneous HSV infection
ü Caused by HSV-1 & 2
ü Lesions- located at vermillion borders of lips
Herpes labialis (fever blister or cold sore)
ü Occurring in children with eczema
Eczema herpeticum
NEVER BACK DOWN NEVER WHAT!!!!!!!!!!!!!!!???????????
NEVER GIVE UP!!!!!!!!!!!!!!!!!!11
