Gram positive basteria:

Staphylococci (S. epidermis, S.aurus)

Streptococci (grp A,B,C,& G), S. pyogenes 

corynobacterium, other diphteroids

propionobacterium (acne)

Fungi:

Malassezia sp

Candida sp 

Acute inflamation of the skin and subcutaneous fat.

typically a diffuse, spreading skin infection, most commonly affects extremeties (70%)

Gram +:

grp A Streptococci (S. Pyogenes (most common)

S. Aurus (MSSA)

MRSA (CA & HA) (usually associated w/ purulent cellulitis)

Gram -:

E.Coli 

P. aeruginosa

Klebsiella pneumoniae

Exposure to lake or ocean water (pt hx):

Aeromonas hydrophilia & vibrio vulnificus 

Spider bite 

characterized by necrotic centers 

Inflammation of hair follicules, superficial infection involved only in the dermis 

itchy red papules appear ~ 48 hrs after exposure 

Evolves into pustules that generally heals without tx in several days 

Systemic symptoms uncomon 

Abscess or boil 

walled of pocket of pus from a hair follicle 

involves deeper layers of skin 

occur (in area of friction perspiration) as single or multiple nodules 

Gradually become red, firm and painful 

Drain by themselves 

What are carbuncles?

Multiple furincles unite into one big mass

Extended into subcutaneous tissues

Masses draines through many sinus tracts

Common in back of neck in diabetics

systemic symptoms often present (chills, fever, malaise)

spread to other tissues/bacteremia (causes serious concern)

Incision & drainage 

PO abx not necessary except:

Extensive surrounding cellulitis

Fever

Macular erythema 

Generalized swelling

Warm to the touch 

Tenderness

Tender, regional lymphadenopathy 

Lymphagitis (sometimes)

Abscess (sometimes)

Yellow indicates severe cellulitis 

Fever, chills

Hypothermia

Increase WBC

Tachycardia

Hypotension

Confusion in elderly 

Septic shock

CBC w/ differential

C-reactive protein

Creatinine

Bicarbonate

Creatinine phosphokinase

Blood cultures (+<5%)

culture/punch biopsies (5-40% +)

Drug susceptibility 

Osteomyelitis (w/ or w/o amputation)

Bacteremia, sepsis 

Clean site (soap/H2O), irrigate, remove foreign bodies 

No abx needed unless immunocompromises or DM patients use Topical abx:

- Mupirocin (bactroban)

- Neomycin/polymixin/bacitracin (Neosporin)

(weaker activity against S. aureus) (toxic if applied to open wound) 

- Clindamycin, erythromycin or benzoyl peroxide 

Cover S.pyogenes, S. aureus (MSSA):

- Dicloxacillin 

- Cephalexin 

if IV needed: 

- Nafcillin

- Cefazolin 

If PCN allergic:

- Clindamycin, vancomycin, TMP-SMZ

Treat for 5-10 days 

TMP-SMX

Doxycycline

Minocycline

Linezolid

Clindamycin 

Duration: 7-14 days 

D-test uses for MRSA clindamycin resistanceif Positive= MRSA resistant to Clinda 

Negative= MRSA susceptible to Clinda 

IV required:

Coverage for S. pyogenes, MSSA:

- Nafcillin 

- Cefzolin 

Is PCN allergic: Clindamycin, Vancomycin

Duration: 7-10 days 

Vancomycin (dosed based on renal fct)

Linezolid

Daptomycin

Telavancin

Clindamycin

Duration: 7-14 days 

- Tigecycline (Tygacil)

- Quinupristin-dalfopristin (synercid)

- Rifampin-not used monotherapy

- Misdiagnosis

-Abx resistance

-Non-adherence

-Subtherapeutic doses

IV drug abuser:

Add S. epidermis, P,aeruginosa to causative organisms (if severe)

Abx resistance (MRSA)

Immunocomprimised:

more aggressive tx, may treat longer than 10 d

must consider fungi, viral, atypicals

PCN drug of choice

Mild-moderate:

-Procaine PCN G

-PCN VK

PCN allergy:

-Clinda

-Erythromycin

Duration: 7-10 days 

Severe: need hospitalization use aqueous PCN G

What causes impetigo?

Superficial infection

S. pyogenes/ S.aureus 

Itchy, purulent discharge; dries to golden yellow crusts 

Treatment of impetigo?

Mild: topical mupirocin

numerous lesion/lack of response to topical: PO

-Dicloxacillin

-1st gen cephalosporin

- PCN VK (S.pyogenes)

PCN allergic:

-Clindamycin

Duration: 7-10 d (7 d clinical response)

Bacteria:5 organisms at same time common

Gram -, anaerobes (clostridia bacteroides), enterococcus

Assosiated w/:

-abdominal surgery

-Decubitis ulcers

-IV drug use

-Bartholin abscess 

What causes type 2 mono-microbial necrotizing fasciitis?

Bacteria: S.pyogenes, S. aureus (& MRSA), V. vulnificus, A.hydrophilia, anaerobic strep sp, clostridia sp (rare)

Associated w/:

DM, ASCVD, PVD

Surgery: aggressive surgical exploration/dbridement required

Abx: type1: coverage for anaerobes, S.aureus/S.pyogenes, G-

Type 2: coverage for S.pyogenes/S.aureus, clostridia if gas present

Hemodynamic support: shock tx, etc..

Pasteurella multocida (G-) (75%)

S. Aureus/S.yogenes (G+)(40%)

Anaerobes (A) (65%)

Pasteurella multocida (G-) (50%)

S.aureus/S.pyogenes (G+) (40%)

Anaerobes (A) (50%)

Viridans Strep (G+) (100%)

Bacteroides sp (G- A)(82%)

S.epidermidis (G+) (53%)

Corynebacterium (G+)(41%)

S.aureus (G+)(29%)

Peptostreptococcus (G+A)(26%)

Eikenella (G-A)(15%)

Wound involves hand/near joint

Deep puncture (cat)/difficult to irrigate

Immuno compromised 

tetanus prophylaxis may be needed 

Consider rabies if in area/unprovoked attack by wild animal 

Amoxicillin/clavulanic acid 875/125 mg BID * 5-10d

PCN allergy:

Doxycycline (not if <8yo)

SMX-TMP

+ Clindamycin

for 5- 10 d

Augmentin 875/125 mg BID * 5-10 d

if PCN allergic:

Clindamycin + SMX/TMP * 5-10 d 

If severe infection at presentation, then IV may be required 

Clostridium tetani (G+ anearobe)

vaccine immunizes against exotoxin C. tetani