Infections of the skin, muscle and soft tissue - DONE Flashcards
What protects the epidermis from infections?
Protection of the epidermis depends on the mechanical barrier afforded by the stratum corneum
What can cutaneous inoculation cause?
intracellular infection of the squamous epithelium with vesicle formation may arise from cutaneous inoculation, as in HIV1 infection
What are the risk factors of staph infections of the skin and deep soft tissues?
- chronic skin conditions (e.g. eczema)
- skin damage (e.g. skin bites, minor trauma)
- injections (e.g in diabetes)
- poor personal hygiene
Where do we usually form pus-containing blisters?
hair follicles
S. aureus produce 3 types of toxins:
- cytotoxins
- pyrogenic toxin antigen
- exfoliative toxin
When does illness usually occur when having S.aureus?
illness develops after toxin synthesis and absorption and the subsequent toxin-initiated host response
What is folliculitis?
staphylococcal infections
superficial infection that involves the hair follicle, with a central area of purulence (pus) surrounded by induration and erythema
Furuncle =
boil
Furuncles:
staphylococcal infections
= boil
- more extensive than folliculitis
- painful lesion that tend to occur in hairy, most regions of the body
- extend from hair follicle to become a true abscess with an area of central purulence
Carbuncles:
staphylococcal infections
- cluster of boils caused by infection (s. pyogenes also possible, but less common)
Where are carbuncles usually located?
staphylococcal infections
most often located in the lower neck and more severe and painful than furuncle
Staphylococcal skin infections - treatment:
- What is the most important therapeutic intervention?
The most important therapeutic intervention - surgical incision and drainage of all suppurative collections
Staphylococcal skin infections - treatment:
- If there is a risk of dissemination and bacteria?
Antibiotic therapy may be recommended:
-
MSSA treatment:
dicloxacillinPO 500 mg qidorcephalexinPO 500 mg qid, clindamycinPO 300 mg tid
MRSA treatment:
clindamycinPO 300 mg tid, TMP-SMX PO 480-960 bid, doxycyclinePO bid, linezolidPO 600 mg bid
Mastitis def:
infection of the breast which usually develops in 1-3% of nursing mothers
What are the etiologies of mastitis?
- s. aureus (the most common)
- s. epidermidis
- streptococci
When does mastitis occur?
generally presents within 2-3 weeks after delivery
What are the clinical manifestations of mastitis?
range from cellulitis to abscess formation
- systemic signs, fever and chills, are often present in more severe cases
What is the treatment of mastitis?
cephalexin PO 500 mg qid, cephadroxil PO 1g once a day
SSSS =
Staphylococcal scaled-skin syndrome
Who is mainly affected by SSSS?
SSSS primarily affects newborns and children, much less common in adults
What are the symptoms of SSSS?
- SSSS may vary from a localized blister to exfoliation of much of the skin surface
- skin is usually fragile and often tender, with thin-walled, fluid-filled bullae
- gentle pressure results in rupture of the lesion, leaving denuded underlying skin
- generalized symptoms: fever, lethargy, poor feeding, dehydration
What causes SSSS?
exfoliative toxin-producing strains
What does SSSS usually follow?
SSSS usually follows localized skin infection
What is the treatment of SSSS?
anti-staphylococcal + supportivetherapy
What does the streptococcal superficial infections usually involve?
- impetigo
- erysipelas
- cellulitis
What does the streptococcal deep seated infections involve?
- necrotizing fascitis
- myositis
- myonecrosis
Impetigo =
pyoderma
- honeycomb-like crust
Impetigo (pyoderma) def:
- superficial infection of the skin caused by primarily by the GAS, occasionally by other streptococci of s.aureus
- not painful lesions
- FEVER IS NOT A FEATURE OF IMPETIGO
Who usually gets Impetigo (pyoderma)?
most often in young children
What are the usual sites of involvement of Impetigo (pyoderma)?
- face (around the nose and mouth)
- legs
What is the treatment of Impetigo (pyoderma)?
- the same as in streptococcal pharyngitis
- if s.aureus etiology is possible, empirical treatment should cover both streptococci and s.aureus
- CloxacillinPO 500 mg qidorcephalexinPO 250 mg qid–10 days
- Topical mupirocin ointment is also effective
What do we do if the empirical treatment of Impetigo (pyoderma) is ineffective?
If epimirical treatment is ineffective – MRSA infection is possible (culture should be taken)
Erysipelas def:
- infection involving the skin and subcutaneous tissues, develops over a few hours
- protal of entry - any break in the skin
What are the distinctive features of erysipelas?
well-defined indurated margins and intense pain
- flaccid bullae may develop during the second or third day of illness, but extension of deeper soft tissue is rare
What are the clinical features of erysipelas?
- pain
- intense red colour
- lesion is warm to the touch
- appears shiny and swollen
- fever and chills are common
Which areas of the body gets erysipelas?
- face
- lower extremities
What happens to erysipelas after 5-10 days?
After 5-10 days desquamation of the involved skin occurs
Erysipelas treatment:
- PenicillinG IV 3 mln U qid orV-penicillin PO 1.5 mln U tid–10 days
- Clindamycin IV or PO 600 mg tid–10 days
Cellulitis def:
Streptococcal cellulitis tends to develop at anatomy sites in which normal lymphatic drainage has been disrupted (e.g. sites of prior cellulitis, the arm ipsilateral to a mastectomy and axillary lymph nodes dissection, lower limb with previous deep vein thrombosis)
What causes cellulitis?
- fissures of the skin- a portal of entry for streptococci
- cellulitis may also involve recent surgical wounds
- infection may also be associated with lymphangitis manifested by red streaks extending proximally along superficial lymphatics from the infection site
What is the treatment of cellulitis?
penicillinG, clindamycin–as in erysipelas; cephazolinIV 1-2g tid, ampicillin/sulbactam1.5-3 g IV qid
Necrotizing fascitis
- may be associated with GAS or mixed aerobic-anaerobic bacteria or may occur as a component of gas gangrene caused by clostridium perfringens
What are the early manifestations of necrotizing fascitis
- early diagnosis is difficult - pain and unexplained fever is the only presenting manifestation
What does necrotizing fascitis look like after the early manifestations?
- swelling develops and is followed by browny edema and tenderness -> dark-red induration of the epidermis -> bullae filled with blue or purple fluid -> skin becomes friable and takes on a bluish, maroon, black colour
How does the spread of necrotizing fscsitis occur?
rapid spread occur along fascial planes through venous channel and lymohatics
What happens in the late stages of necrotizing fascitis?
toxic shock and multiorgan failure
What are the predisposing factors of necrotizing fascitis?
- peripheral vascular disease
- diabetes mellitus
- surgery
- penetrating injury to the abdomen
Fournier’s gangrene:
Leakage into the perineal are result in a syndrome called Fournier’s gangrene - massive swelling of the scrotum and penis with extension into the perineum or the abdominal wall and legs
What is the frequency of myositis occurring concomintantly?
in 20-40% of cases, myositis occurs concomitantly
In how many cases does the myonecrosis occur concomitantly with fascitis?
in 50% - both are a part of the toxic shock syndrome
What may induce primary myositis (streptococcal necrotizing myositis)
S. pyogenes may induce primary myositis (streptococcal necrotizing myositis) in association with severe systemic toxic shock syndrome.
What is the treatment of necrotizing fascitis?
- early surgical exploration
- GAS: clindamycinIV 600-900 mg q6h plusPenicillinG IV 4 mln U q4h orCephalosporin(first or second generation)
- Mixed aerobesand anaerobes:
- AmpicilinIV + ClindamycinIV + CiprofloxacinIV
- VancomycinIV + MetronidazoleIV + CiprofloxacinIV
Gas gangrene:
usually follows severe penetrating injuries that result in interruption of the blood supply and introduction of soil to wounds
What causes gas gangrene?
caused by the clostridial species:
- c. perfringens
- c. septicum
- c. histolytium
Spontaneous non-traumatic gangrene-
among patients with neutropenia, gastrointestinal malignancy, recent radiation therapy, etc. (Cl. septicum)
When does the gas gangrene of the uterus occur?
- after abortion
- vaginal delivery
- cesarean section
What causes gas gangrene of the uterus?
C. sordelli
What is the clinical picture of gas gangrene of the uterus?
- little or no fever
- lack of purulent discharge
- refractory hypotension
- extensive peripheral edema and effusions
- markedly elevated WBC
What is the treatment of gas gangrene?
- aggressive surgical exploration
- visualization of the deep structures
- removal necrotic tissue
- reducing compartment pressure
- obtaining material for gram staining and for cultures
What is the primary antibiotic for gas gangrene?
- Clindamycin + Penicillin G
What is the alternative treatment of gas gangrene?
- Clindamycin + Cefoxitin
What are the most common infections complicated serious burns are:
- pneumonia
- septicemia
- cellulitis
- wound infection
what is the most predominant causes of burn-wound infection in pre-antibiotic era, but still remains important?
- strep
- staph
What is a major problem in burn-wound management?
- pseudomonas aeruginosa
What is an increasingly important pathogens when it comes infectious complications of burns?
fungi (c. albicans, aspergillus)
Burn-wound impetigo:
Characterized by loss of epithelium from a previously re-epithelialized surface
Invasive infection in unexcised burn wounds
- Secondary to a partial or full-thickness burn wound and is manifested by separation of the eschar or by violaceous, dark brown, or black discoloration of the eschar
Green discolouration of the wound or subcutaneous factor erythema gangrenosum
susp. Invasive P. aeruginosa infection
Infection of burn wounds - diagnosis:
and sepsis
- changes in temperature
- hypotension
- tachycardia
- neutropenia
- thrombocytopenia
- renal failure
Burn-surgical wounds are found in up to……
39% of patients
What is the treatment of infections of burn wounds?
- closure and healing of wounds
- topical antimicrobial agents
- systemic treatment
- alternative treatment: vancomycin and ciprofloxacin
- linezolid
Linezolid:
infections of burn wounds
efficacy in reducing bacterial growth and toxic shock syndrome
What are the topical agents used in treating infections of burn wounds?
- silver sulfadiazine cream
- mafenide acetate cream
- sillver nitrate cream
- mupirocin (MRSA)
dramatically decrease incidence of infection
What are the systemic treatment of infections of burn wounds?
- antibiotic active against gram-positive bacteria plus drugs active against P. aeruginosa and other gram-negativees
What are the alternative treatment of infections of burn wounds?
- vancomycin
- ciprofloxacin
infectious complications of bites:
the microbiology of bite- wound infections in general reflects the oropharyngeal flora of the biting animal, although organims from the soil, the skin of the animal and victim, and the animal´s feces may also be involved
Of all animal bites how many are from dogs?
80% of all animal bite wounds -> 15-20% become infected
When is the infection manifested after the bite?
infection manifests 8-24h after the bite - cellulitis with purulent discharge, fever, lymphadenopathy, lymphangitis
The microbiology of dog-bite wound infections usually mixed:
- ß-hemolytic streptococci, Pasteurella sp, Staphylococcus sp, Eiknella corodens,
- anaerobic bacteria such as Actinomyces, Fusobacterium, Prevotella, Porphyromonas
Infection with C. canimorsus (Gram-NEGATIVE) may result……
in fulminant sepsis, especially in host with impaired hepatic function, after splenectomy or immunocompromised
What is the treatment of dog bites and cat bites?
- amoxicillin/clavulanate
- clindamycin + ciprofloxacin
C. canimorsus (Gram-NEGATIVE) treatment?
penicillin G IV every 4h
Cat bites treatment?
same as in dog bites
Cat bites:
cat bites are more likely to cause septic arthritis and osteomyelitis (mainly localized in hand) compared to dogs
Pasteurella multocida:
cat bites
- gram-negative coccbacillus
- implicated in the majority of cat-bite wound infection, but the microflora is usually mixed
- tend to advance rapidly (within hours)
- causing severe inflammation with purulent drainage
% of the human bites that gets infected:
wounds infected in 10-15% of cases of human bites
Aerobic species in human bite infections:
- strep
- s.aureus
- E.corrodens
- H. influenzae
Anaerobic species human bite infections:
- Fusobacterium
- Prevotella
- Porphyromonas
- Peptostreptococcus
Flora of hospitalized patients:
human bite infections
Flora of hospitalized patients may include Enterobacteriacea
What is the treatment of human bite infections:
amoxicillin/clavulanate or fluoroquinolone
