7 - Bacterial Diseases Flashcards
Primary infections
- Normal skin
- Coagulase-positive staphylococci 98% of PRIMARY skin infections are GRAM POSITIVE
- Beta-hemolytic streptococci
- ***We will focus on primary infections today
Secondary infections
- Damaged skin
- Proteus
- Pseudomonas
- Escherichia coli
- ***Usually worse infections
Impetigo contagiosa (superficial)
- Common in childhood, during the summer (high humidity)
- Erythematous vesicle
- Honey crusted lesion with amber exudate (golden-looking crust)
- Causative agent S. aureus (most common), Group A strep, S. pyogenes
Impetigo contagiosa (superficial) treatment
Treatment
o Beta-lactamase-resistant antibiotics (erythromycin, oxacillin, dicloxacillin) – antibiotic with gram POSITIVE coverage
o Topical antibiotic ointment (Neosporin, mupirocin, etc.)
o STUDY topical treatment is just as effective as oral antibiotics
Impetigo contagiosa (bullous)
- Less common
- Bullae less than 3 cm in diameter with amber liquid or white/yellow pus
- Can still see honey crusting, but over a much larger lesion
- Treatment = Same as superficial impetigo
Ecthyma
- Similar to superficial impetigo, but you will see shallow erosions through the epidermis of the lower extremity, still honey crusted
o Not deep enough to be considered a secondary infection (ulcer) - Causative agent = Streptococcus or other
- Treatment
o Same as impetigo - NOTE = lesions look similar to ecthyma gangrenosum (pseudomonas septicemia), which would be gram negative
Ecthyma gangrenosum
- Green coloration Chemical component in the bacteria produce a green exudate
- Causative agent = Pseudomonas
Cellulitis
- Infection of skin and subcutaneous tissue
- Causative agent Group A strep, S. aureus, Pseudomonas, other
- May or may not have a portal of entry
- Organism will cause the 5 cardinal signs of infection
Cellulitis treatment
o Penicillinase-resistant penicillin or cephalosporin
o Response to antibiotics is typically rapid (3-4 days)
o If the response is not rapid, determine if there is an abscess
Erysipelas
General
o AKA “St. Anthony’s Fire” because the redness is so deep in color
o Very severe strep infection, common in the lower extremity
o Primary pyogenic infection associated w/ lymphatic obstruction
Elephantiasis nostras verrucosa
o Swollen legs w/ high intensity redness – Fire engine red
Causative agent = Streptococcus pyogenes
Erysipelas treatment
o CBR (complete bed rest) – may need to admit to hospital
o Elevation of extremity
o IV antibiotics (cephalosporins)
o Cool wet dressing
o Unna boot (used to ↓ swelling/edema, gauze dressing with either calamine lotion or zinc oxide to reduce itching)
Cutaneous abscess
- Localized subcutaneous or dermal accumulation of purulent material
- Usually starts as a folliculitis, may have cardinal signs of infection
- Causative agent Staphylococcus or streptococcus (gram stain)
- Treatment = Incision and drainage
Folliculitis
- Inflammation of the hair follicle caused by infection or injury
- Appearance Red elevated and tender pustule
- Causative agent = Coagulase positive staphylococci
o May start after an abrasion or surgical incision
o It is difficult to avoid hair follicles along the surgical incision
o Hair along the incision starts to grow again, causes a pimple - Treatment = Incise and apply topical antibiotic
Pseudomonal folliculitis
- Causative agent Pseudomonas (gram negative)
o May obtain organism from follicle or contaminated hot tub - Lesions on legs, buttock and arms (anywhere submerged in water)
- Treatment is the same
(“Hot tub dermatitis”)
Furunculosis
- Acute staphylococcal infection of the hair follicle with more inflammation and spread of cellulitis
- Common in athletes
- Treatment
o Incision and drainage
o Oral antibiotics
