Skin and Soft Tissue Infections Flashcards
What is the most common pathogen in skin abscesses?
S. aureus (75%)
What ate the main kinds of skin abscesses?
- nodules, carbuncles and furuncles
What is a nodule?
- painful and red in the dermis and deeper structures
What is a furuncles?
- boils in the hair follicle
- inflammatory nodule with overlying pustule collection in the dermis and the deeper structures
What are carbuncles?
- collection of furuncles
Where are skin abscesses usually located?
- on the back of the neck, face and axillae
What is the difference between an abscess and cellulitis?
Abscess - kind of like a pocket
Cellulitis - goes into the structure of the fat and the hair glands
Where does an abscess usually start?
- typically in the hair follicle
What is the general approach to treating skin abscesses?
- drainage plus/minus heat compresses by 30 minutes, 3-4 times daily for small lesions, or surgical incision and drainage for larger lesions
When is antimicrobial therapy needed to treat a skin abscess?
- for abscesses larger than 2 cms, multiple lesions, extensive cellulites, systemic signs of infection, indwelling medical device or immunocompromised
What are the 2 most common antibiotics for treating skin abscesses?
Cloxacillin
Cephalexin
What is the alternative therapy for treating skin abscess in a severe beta lactam allergy?
clindamycin
What is the risk of using Clindamycin to treat a skin abscess?
increasing resistance in S. aureus
What are the risk factors for a MRSA infection?
- MRSA colonization, close contact with MRSA infection, previous antimicrobials or S aureus infection particularly is treatment failure with regimen that lacked MRSA coverage
In what facilities are hospital acquired MRSA infections generally spread?
- medical procedures
- dialysis
- hospitalization
- long term care facilities
- higher antimicrobial resistance rates than CA strains
What antibiotics are MRSA resistant to? What causes this resistance
- penicillins
- cephalosporins
- carbapenams
– alterations in the penicillin binding protein causes this resistance to occur
How can S. aureus get into the body?
- natural bug on the skin- if a patient is immunocompromised or in the case of a cut it can get into the skin
What medications are used to treat community acquired skin and soft tissue infections?
- Clindamycin (if macrolide resistant there will be an increased risk of inducible clindamycin resistance developing during therapy)
- Doxycycline
- TMP-SMX
Explain an approach to managing patients with recurrent furuncles or carbuncles?
- S. aureus colonized (positive nasal swabs) - mupirocin 2% applied 2-3 time daily for 5 days every month
- decolonize their nose as a way to get rid of the staph where it is colonized. This can get rid of the skin and staph infections and these patients are susceptible to
Describe the characteristics and most common pathogens of impetigo?
- highest incidence in children 2-5 years old
- superficial infection of epidermis, 90% non-bullous, 10% bullous
What bacteria are potentially in non-bullous impetigo?
S aureus and S pyogenes
What bacteria are potentially in bullous impetigo?
S aureus
Gram positive cocci in clumps are _____
Staph aureus
Gram positive cocci in a chain are _____
Strep pyogenes
Is antimicrobial therapy always indicated?
- moderate to severe non-bullous, and bullous infection
- mild, non-bullous infections often resolve spontaneously within weeks, however antimicrobial therapy reduces transmission, hastens symptoms and progression, prevents complications
Where is strep. viridans usually found?
in the mouth and in endocarditis
What factors influence the selection of topical antimicrobial therapy?
- non-bullous infections with limited area and number of lesions and low risk of complications
- mupirocin 2% applied bid for 5 days - mono carboxylic acid inhibits RNA synthesis, more effective than the alternatives
What are the anti-staph antibiotics used to treat impetigo?
- cloxacillin, cephalexin (these are anti-staph - clindamycin in the case of severe beta lactic allergies)
- – duration of 7 days
What are the po antimicrobial options for pathogen-directed therapy?
(MSSA)
cloxacillin and cephalexin
Clindamycin in the case of severe beta lactic allergies
What are the po antimicrobial options for pathogen directed therapy? (MRSA)
Clindamycin and doxycycline or TMP-SMX
What are the po antimicrobial options for pathogen directed therapy to treat S. pyogenies?
Pen V or Amoxicillin
Clindamycin in the case of a severe beta lactam allergy
Doxycycline does not cover ______ infections
Strept. pyogenes
Who can you not give doxycycline to? Why?
- You cannot give doxy to pregnant women and children- it affects the bone and teeth formation
What is the main side effect associated with TMP-SMX?
-severe allergy or sensitivity reactions
Describe cellulitis
- diffuse, superficial skin infection of epidermis and dermis that can extend to cutaneous lymphatics and SC fat; erysipelas synonymous with cellulitis, with various definitions but generally superficial involving upper dermis or lower superficial lymphatics with more delineated borders
What bug is the most common in cellulitis?
- S pyogenes and other beta hemolytic streptococcus including Group B, C, F or G, or less common S aureus (typically associated with purulence abscess, wound, trauma)
What is the clinical presentation of cellulitis?
- appearance can include orange-peel-like, vesicles, bullae, petechiae or ecchymoses, phlebitis or lymphangitis (streaking)
- local pain, erythema, warmth, deem with systemic sings of infection (fever, chills and malaise)
What are the risk factors for cellulitis?
- skin disruption (abrasion, insect bite, ulcer, wound, trauma, IVDU), inflammation (eczema, radiation)
- advanced age, obesity
- diabetes mellitus, immunocompromised
- peripheral vascular disease, lymphatic obstruction
What are the important adjuvant, non-pharm measures for treating cellulitis?
- immobilization
- elevation
- cool and warm dressing
Why would we use rifampin to treat a staphylococcal infection?
- used in combination with other medications because on its own it can lead to resistance
- we use rifampin to treat some STAPH infections but only in combination with other antibiotics
- also use in the case of prosthetic join replacement
What enzyme does rifampin induce?
- Cyp P450
What is the interaction between TMPSMX and spironolactone?
- affects the renal elimination of potassium so it will increase the K in the body
- doxy does not have this interaction with spironolactone
What factors are considered in selecting po vs IV antimicrobials for treating cellulitis?
- severity of cellulitis based on location, area and progression
- systemic signs of infections (fever, chills, confusion)
- po tolerability
What is the drug indicated for treating a mild cellulitis infection with S. pyogenes? (po)
Pen V
Amov
[Clinda]
— TMPSMX and Doxy both lack strept coverage so therefore clinda is our drug
What are the medications that are used for severe cellulitis with suspected pyogenes and/or MSSA?
- cloxacillin
- cephazolin, cephalexin
[clinda]
You can never give _____ and ______ with an MSSA infection? (do not want to miss the chance that the patient is infected with staph)
penicillin and amoxicillin
What antibiotic (IV) us used to treat severe cellulitis in outpatient IV programs?
- ceftriaxone (can be given OD)
What are the drugs that could be used in treating moderate cellulitis for treating suspected s.pyogenes and/or MRSA?
- clindamycin
- doxy + (pen and amox)
- TMP-SMX + (pen and amox)
What are the risk factors for MRSA?
- MRSA colonization, close contact with MRSA infection, previous antimicrobials or S.aureus infection particularly if treatment failure with regimen that lacked MRSA coverage
What is used for severe cellulitis with suspected S.pyogenes and/or MRSA?
- vancomycin (this is the drug of choice)
[linezolid (also po) or daptomycin]
What are the potential disadvantages of using Levo or Moxi?
- quinolines should never be used for a SSTI
- less effective than the alternative due to unreliable strept and staph activity from intrinsic or acquired resistance during therapy
- unnecessarily broad Gram negative coverage
- increasing resistance and significant cover regarding collateral resistance
Why might a cellulitis infection get worse after you start antibiotics?
- if the patient receives appropriate therapy and the bacteria break open - release all of the toxins that were inside of the cells so you can notice that the site of infection may not get better in 2 days and might actually get worse
- should notice that fever and fatigue are better however
What is the typical response and duration of therapy for uncomplicated cellulitis?
Response: clinical improvement within 24-48 hours, visible improvement may be delayed for 72 hours
Duration: 5 days (for 14 days for severe infection, slow response, immunocompromised)
Describe type 1 necrotizing cellulitis
- Type 1 (80%) associated with surgery or trauma; polymicrobial mixed infection with GP, GN and anaerobes
Describe type 2 necrotizing cellulitis
- Type 2 (streptococcal gangrene, flesh eating bacteria) caused by virulent S.pyogenes, very rapid progression with severe systemic signs of infection including septic shock
Describe type 3 necrotizing cellulitis
Type 3 (clostridial gas gangrene- C.perfringens, myonecrosis- C.septicum) associated with surgery or trauma, very rapid progression with gas production and myonecrosis
What is used as empirical broad-spectrum antimicrobial therapy for necrotizing cellulitis?
- pip-tazo or meropenum + vanco + clinda
S.pyogenes is treated with what?
- PenG and clinda and IVIG for toxic shock
Clostridium is treated with what?
- PenG and clinda and IVIG for toxic shock
Aeromonas hydrophila (fresh water) is treated with what?
- TMPSMX or Cipro and Ceftriaxone for Doxy
Vibrio vulnificus (sea water) is treated with what?
- ceftriaxone and doxy/cipro
Why do we want to save carbapenems for last resort?
- broadest antibiotics that we have - carbapenams are the last line of antibiotics and we want to save these antibiotics for when we absolutely need them- we are very worried about resistance
Clindamycin is a _____ inhibitor?
- ribosomal- therefore it is inhibiting the synthesis of proteins in the body
- – macrolides and tetracyclones are also ribosomal inhibitors of protein synthesis
What bugs are typically present in a dog or cat bite wounds?
- pasteurella multocida. steptococcus or S.aureus, fusobacteria, prevotella, porphyromonas, bacteroides spp
P. multocida is typically susceptible to Pen, Doxy, FQ, TMPSMA and is resistant to what?
- Clinda
How many days before do you give antibiotics prophylactically for animal bite wounds?
- 3-5 days before to prevent infection of high risk wounds from a moderate to severe bite, on face, on hands involving joins, significant edema or immunocompromised
What is the duration of therapy when treating a bite wound that is already infected?
5 to 10 days
What is the first line antibiotic for treating an animal bit wound?
- amoxi-clav 875/125 mg q12h, children 20 mg/kg
What are the alternatives that are used to treat animal bite wounds?
- Doxy + (clinda or metro)
- Cipro/levo/moxy) + (clinda or metro)
- TMPSMX + (clinda or metro)
- Macrolide/azolide (if susceptible pasteurella) +clinda
- Macrolide/azolide (susceptible pasteurella) + clinda
What is used in the case of a severe animal bite infection?
- pip-tazo
- ceftriax + metro
- cipro/levo/moxi and clinda/or metro
Why can you not use doxy in pregnancy or children?
- has effects on the bones or calcification of the teeth
Why can you not use cipro and quinolones in pregnancy?
- tendon issues
Why can you not used TMPSMA in pregnancy?
- displaced bilirubin and can cause babies to be born with jaundice
What bacteria is cat scratch disease caused by??
bartonella henselae
What does cat scratch disease appear as?
- presents as papule or pustule with lymphadenopathy within 3-30 days
What is cat scratch disease treated with?
- azithromycin 500mg then 1 250mg q24h for 4 days
What bacteria are commonly found in human bite wounds?
- B hemolytic streptococcus in over 80%, eikenella corrodens in 30%, then S. aureus and oral anaerobes
E. corrodens is susceptible to what antibiotics?
- penicillins, doxy, TMPSMX, and is resistant to clinda and metronidazole
How long does antimicrobial treatment for human bite infections last?
7-14 days or 4-6 weeks for septic arthritis
first line is amoxi-clav
What are the alternatives used to treat human bite wounds?
- doxy + (clinda or metro)
- cipro/levo/moxi + clinda or metro
- TMPSMX + clinda or metro
What diabetes related factors increase the risk of diabetic foot ulcers and infections?
- angiopathy with peripheral vascular disease and schema
- neuropathy with sensory, motor and autonomic dysfunction
- immune dysfunction
What are the adjuvant (non-antimicrobial) measures for treating diabetic foot ulcers?
- glycemic control
- wound care including debridement, dressing changes
- pressure relief, off-loading, elevation
What ar the clinical features of a diabetic foot infection?
- erythema, swelling (edema), warmth and purulent discharge
- little to no pain or systemic signs of infection in >50%
What is the classification of a mild diabetic foot infection?
- superficial skin with erythema <2 cm, swelling, heat or pain; no systemic signs of infection
What is the classification of a moderate diabetic foot infection?
- deep localized with erythema >2 cm, abscess, fasciitis, septic arthritis or osteomyelitis, no systemic signs of infection
What is the classification of a severe diabetic foot infection?
- significant systemic signs of infection, eg. tachycardia, tachypnea, leukocytosis, hypotension
Describe the most common pathogens in DFIs?
- superficial, acute cellulitis and/or infected ulcer not treated with antimicrobials in the previous month - strept and staph
What is the most common pathogen in a deep, chronic infected ulcer and treated with antimicrobials int he previous month?
- mixed polymicrobial with gram positive aerobes, gram negative aerobes and anaerobes in 25-40%
What are the common complications of DFIs?
- spread to joints or bone
- amputation in 10-20% of cases at one year and 25-50% at 5 years
What factors are considered in using antimicrobials in treating DFIs?
- infected wound vs colonized ulcer
- adequate wound debridement and care
- severity of infection and clinical status
- bone involvement
- risk factors for antimicrobial resistance: chronic infections, repeat antimicrobial exposure, low antimicrobial concentrations at the infection site, MDR pathogens that limit options for antimicrobial therapy
What antibiotics are used for a mild DFI with suspected gram positive?
- cloxacillin (plus/minus doxy or TMPSMX)
- cephalexin (plus/minus doxy or TMPSMX)
[clindamycin]
What antibiotics are use for moderate acute or chronic infection with suspected mixed, polymicrobial?
- amoxi-clav (plus doxy or TMPSMX)
[clindamycin plus cipro/levo/moxi]
Clindamycin has _____ coverage
anerobic
What other Ab has anaerobic coverage?
- metronidazole
- moxifloxacin also has some anaerobic coverage
What is used in a severe, chronic infection that is mixed polymicrobial?
- piptazo
- meropenum
- cefriaxone+ metro
- ceftazidime + metro
What factors do you consider when choosing a dose for an antibiotic?
- severity
- limiting toxicity
- body weight
- kidney function
- generation into the bone or the CSF to limit the growth of bacteria in these cases
