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Infectious Disease and Medical Microbiology > Skin, Soft Tissue Infection > Flashcards

Flashcards in Skin, Soft Tissue Infection Deck (56)
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What is the most common infectious agent in cat bites? Dog bites?

Cat: Pastuerella multicoda
Dog: Pasteurella canis


What percentage of cat bites become infected compared to dog bites?

80% vs 5%


What is empiric treatment for dog or cat bites?



What are the most common infectious organisms in a human bite? (7)

-Viridins strep 100%
-Bacteroides 82%
-Staph epidermidis 53%
-Corynebacterium 41%
-Staph aureus 29%
-Peptostreptococcus 26%
-Eikenella 15%


What are two vaccine-able disease that always need to be considered with animal bites?



What are the conditions when a bite would be treated for tetanus?

-Vaccine: minor wound and no vaccine in last 10 years or major wound and no vaccine in last 5 years
-Tetanus Ig: major wound and has not had at least 3 vaccine doses


What is the treatment plan if an animal bite might have passed on rabies?

-Rabies Ig around the wound
-Rabies vaccine at day 0, 3, 7 and 14


What organism causes Cat Scratch Disease?

Bartonella henselae


What is the typical and atypical presentations of Cat Scratch Disease?

Typical: Local lymphadenitis +/- cutaneous lesions several days after exposure that can last 1-3 weeks
Atypical (10%): liver, spleen, ocular, neurological or MSK involvement, fever of unknown origin


What tests are typically used to diagnose Cat Scratch Disease? What would you treat it with?

-Serology (IFA), blood culture, tissue PCR
-Treatment: Azithromycin


What presents as these two classic syndromes:
-triad of tenosynovitis, polyarthritis, dermatitis
-purulent arthritis

Disseminated Gonococcal Infection


What is not common in Disseminated Gonococcal infection?

Urethritis/Cervicitis (but swabs often +ve)


What treatment is used for disseminated gonococcal infection?

Ceftriaxone + Doxycycline x 7 days

(Don't forget to Tx partners!)


What is the most common cause of septic arthritis?

Hematological spread > trauma/bite > post-surgery > direct spread from osteomyelitis


What is the most common organism that causes septic arthritis?

Staph aureus


What is the treatment for septic arthritis?

-IV antibiotics based on Gram stain x 4 weeks making sure to cover Staph
-Joint aspiration in all cases, surgical drainage in hip or prosthetic infection


What is Ludwig's Angina?

Cellulitis of the submandibular/sublingual spaces


What does Ludwig's Angina almost always result from?

-Oral infection of 2nd or 3rd molars
-80% of patients report tooth pain or recent dental work


How do you manage Ludwig's Angina?

-Manage and protect airway (1/3 of cases require intubation)
-IV antibiotics based on organism
-Surgical evalualtion
-CT scan to evaluate abscess and extent of spread


What are the two most common causes of impetigo?

-S. aureus
-Group A strep


What are the two types of impetigo and their most obvious clinical feature?

Bullous (vesicles) and non-bullous (golden crust)


What are some risk factors for having a diabetic foot infection? (7)

-Previous amputation
-Wound extending to bone
-Peripheral vascular disease
-Ulcer duration >30days
-Loss of sensation
-History of recurrent ulcers
-Wound caused by trauma


Would you need to culture a minor infection if the patient has not received antibiotics within the last month?



If you are treating a foot infection in a patient that HAS received antibiotics in the past month, what modifications to antibiotic therapy must you make?

Cover gram negative rods


What is the presentation of a mild infection?

Local infection involving only the skin and subcutaneous tissue. If erythema is present, must be <2 cm around the wound.


What is the presentation of a moderate infection?

Local infection with erythema >2 cm or involving deeper structures than skin and subcutaneous tissues (eg: acbess, osteomyelitis, septic arthritis, faciitis) AND no systemic inflammatory response.


What is the presentation of a severe infection?

Local infection with signs of SIRS, as manifested by 2+ of the following:
-Temperature >38 Celsius or 90 bpm
-RR >20/min or PaCO2 12,000/mcL or 10% immature forms


What is empiric therapy for a severe infection?

Vancomycin and Pipercillin-Tazobactam/4th gen cephalosporin/carbapenem


Rank the most likely places to get cellulitis?

lower extremities > upper extremity > face


What organisms almost always cause cellulitis?

Staph or Strep


What is the presentation of simple cellulitis?

-no fever or systemic symptoms
-Normal WBC count
-Lymphadenopathy or lymphangitis common


What is the presentation of severe cellulitis?

-systemic symptoms
-bullae, hemorrhage, severe swelling


Is needle aspiration or blood cultures useful in mild or localized infections?



When is imaging used in cellulitis management?

-Xray if trauma or foreign body is suspected
-Ultrasound to see if abcess or DVT is suspected


What is a very easy technique for tracking the progress of infections?

Draw a line around it with a pen.


What are the general differences between managing mild vs severe cellulitis?

-Mild: Outpatient, oral antibiotics
-Severe: Admit, IV antibiotics


Pt's presenting with a clenched fist injury are at risk of what?

1. Septic joint
2. Osteomyelitis
3. Give IV antibiotics and get imaging done


What is the DDx for infectious lymphadenopathy?

1. S. aureus
2. GAS
3. Toxoplasmosis
4. Viral (HIV, CMV, EBV)
5. Bartonella henselae = Cat scratch disease
6. Mycobacterium (TB etc.)


Risk factors for septic arthritis

1. Old age
2. DM
3. Joint disease
4. Recent joint surgery
5. Prosthetic joint


What is the clinical triad for septic arthritis?

1. Fever
2. Pain
3. Decreased ROM in joint


Approach to Dx of septic arthritis

1. Aspirate synovial fluid (look for WBCs, Gram stain, culture)
2. Blood cultures
3. X-ray to rule out osteomyelitis


What organism is the most likely cause of non-bullous and bullous impetigo, as well as scalded skin syndrome?

S. aureus


What is Nikolsky's Sign?

Skin reddens, fluid collects underneath, and skin rubs off, leaving raw red base (S. aureus toxin mediated skin damage)


Tx for non-bullous impetigo

1. Topical antibiotic if localized (mupirocin)
2. Cloxacillin or 1st gen Cephalosporin PO


Tx for bullous impetigo

1. PO or IV Cloxacillin, 1st gen Cephalosporin, or Vancomycin (MRSA)


How should the assessment of a diabetic foot ulcer be structured?

1. Look at whole pt for signs of systemic illness
2. Affected limb/foot (things that may impair healing, PVD)
3. The infection itself


Questions to ask about diabetic foot ulcer

1. Is there an infection?
2. What risk factors are present?
3. How severe is the infection?
4. How should I manage the infection? What drugs?


How do you rank the severity of a diabetic foot infection?

1. No Sx of infection = uninfected
2. Infection present (2 of: swelling, erythema, pain, warmth, pus)
3. Mild = local infection (skin/SQ, not deeper), erythema < 2 cm
4. Moderate = Erythema > 2 cm, or is deeper than SQ, no SIRS
5. Severe = local infection with > 2 SIRS criteria


When should a pt be hospitalized with a diabetic foot infection?

1. Severe infection
2. Moderate infection with poor social support
3. Pt's failing outpatient Tx


Most mild-moderate diabetic foot infections can be Tx with what?

1. Agents that cover Strep and Staph


What is Erisypelas?

1. Infection limited to upper dermis and superficial lymphatics
2. Sharp, raised, and well marked erythema
3. Rapid onset, fever, and signs of systemic toxicity


What causes Erisypelas?

1. Almost always beta hemolytic strep
2. Tx with penicillin V or amoxicillin for outpatient
3. Severe or facial involvement = IV benzathine penicillin G in hospital


What is necrotizing fasciitis?

Deep infection of SQ tissue leading to severe destruction of fat and fascia


Causes of necrotizing fasciitis

1. Immunocompromised/post-op pt's = polymicrobial
2. Healthy pt's = GAS


S/S's of necrotizing fasciitis

1. Systemic signs: fever, tachycardia, hypotension
2. Skin: bullae, disproportionate pain, swelling, erythema, crepitus


Management of necrotizing fasciitis

1. Immediate surgical consult
2. Cultures (best from surgery)
3. IV antibiotics: polymicrobial (Pip-taz and metronidazole or clinda) and for GAS type = Clindamycin + penicillin G