15-10-21 - Infections of the Skin Flashcards
What are 7 features of the skin that allow it to act as an effective defence barrier?
- Epidermis – hard horny layer of dead cells
- The surface is dry
- The skin is constantly shedded and turned over
- The pH of the skin is slightly acidic
- Sweat secretion is low pH
- Rich blood and lymphatic supply, allowing the effective movement of immune proteins
- Produces anti-microbial substances e.g fatty acids, sebum (contains lysozymes), defensins
What are 6 examples of skin conditions?
Where in the skin do they occur?
- Keratinised epithelium – ringworm
- Epidermis – impetigo
- Hair follicles – folliculitis
- Subcutaneous fat – cellulitis
- Deep fascia (around bones and muscles) – necrotising fasciitis
- Muscle – GAS Gangrene
What are the 3 routes of infection into the body?
What are they all?
Skin -
* Pores (holes where bacteria can collect)
* Hair follicles
Wounds -
* Scratches
* Cuts
* Burns
Bites -
* Insects
* Animals
What do impetigo, erysipelas, cellulitis, and necrotising fasciitis look like?
What is the function of normal skin microbiota?
How do they do this?
Where are they normally found?
What are 5 examples of microbiota found on the skin?
- Normal skin microbiota prevents pathogens from colonising the surface of the skin
- They do this by competing for space and resources
- They also secrete chemicals against pathogens and can stimulate the skins immune system
- They are typically found in the upper epidermis and upper areas of hair follicles
- Examples of microbiota on the skin:
- Coagulase-negative staphylococci (staph epidermis and staph aureus)
- Streptococcus pyogenes
- Proprionibacterium acnes
- Corynebacterium species
- Candida species
What are 4 common bacterial infections of the skin?
- Staphyloccocus aureus
- Stereptoccoccus pyogenes
- Pseudomonas Aureginosa
- Mycobacterium TB (only really in immunocompromised people as a skin infection)
What is the morphology of Staphylococcus Aureus?
How do they grow?
How do they come out on a gram-stain test?
What are some virulence factors?
What conditions can Staph Aureus cause?
What are anti-biotic resistance strains of Staph Aureus?
- Staphylococcus Aureus presents with cocci morphology and grow in clusters (like grapes)
- They stain gram positive on a gram stain test
- Multiple virulence factors, including encapsulation and enzymes
- Staph aureus can cause a huge range of illnesses, from pneumonia to skin abscesses, furuncles, and cellulitis
- Anti-biotic resistance strains of Staph Aureus:
- MRSA
- VRSA
What is the morphology of Streptococcus Pyogenes?
How do they grow?
How do they come out on a gram-stain test?
What are some virulence factors?
What group of Streptococcus is dangerous to red blood cells?
- Streptococcus Pyogenes presents with cocci morphology and grows in chains
- They present as gram positive on a gram stain test
- They have multiple virulence factors:
- They can be encapsulated, which prevents desiccation (drying out), foils phagocytosis or reduces complement-mediated lysis
- They can produce many cells which attack host cells and immune pathways
- Group A streptococcus (GAS) are beta haemolytic meaning they can cause beta haemolysis (complete haemolysis) of RBCs surrounding them
What is the morphology of Pseudomonas Aureginosa?
How do they come out on a gram-stain test?
What do they have for movement?
What type of pathogen are they?
Where are they normally found?
Where do they typically cause infections and why?
What do they produce?
- Pseudomonas Aureginosa presents with Coccobacillus morphology
- Gram negative on a gram stain test
- They possess monotrichous flagellum for movement
- They are opportunistic pathogens, meaning it typically only causes infection when the hosts immune system is impaired in some way (immunosuppression).
- It is normally a common part of skin microbiota
- Found colonising catheters, as they are a good biofilm former
- Produces endotoxin A, which induces inflammation and a fever
What are different forms of skin lesions?
- Macule
- Flat, red, local inflammation
- Papule
- Raised, red, more marked inflammation
- Vesicle
- Small blister
- Ulcer
- Disruption of epithelium
What are different terms relating to skin conditions?
What are the 2 types of fungal infections of the skin?
What are examples of each?
- Dermatophytes
- Tinea species
- Tinea pedis (athletes’ foot)
- Tinea corposis (ringworm of the body)
- Tinea cruris (ringworm of the groin)
- Yeasts
- Candida albicans
- Malassezia furfur
What are 5 viral infections of the skin? What are symptoms of each
- Human papilloma virus (HPV) - warts/genital warts
- Herpes simplex virus 1 (HSV1) – cold sores
- Herpes simplex virus 2 (HSV2) – Genital herpes
- Varicella zoster virus (VZV) – chicken pox, shingles
- Coxsackie A virus – hand, foot and mouth disease
What are mites called?
What do they cause and how?
Does the infection have any symptoms?
What may occur?
What might this lead to?
- Mites are known as sarcoptes scabei
- They cause scabies by burrowing inti the skin, and females laying eggs
- This infection is asymptomatic
- Hypersensitivity (allergic reactions) may occur
- May lead to superinfection – infection occurring after, or on top, of previous infection
What do these conditions look like? • Staphylococcal Scalded skin syndrome • Toxic shock syndrome, • Folliculitis • Furuncles
What do these condition look like?
• impetigo (contagiosa/nun bullous)
• impetigo (bulluous)
What do these conditions look like?
• Carbuncles
• Wound dehiscence (splitting) with superficial infection
• S aureus infection in patient with diabetes mellitus (diabetes)
• Catheter related infections
• Ecythyma granulosum look like?
