Exam 2 Flashcards
Treatment for Furuncle/Carbuncle
– almost always caused by Staphylococcus aureus
– symptoms: systemic. impaired defense, cellulitits
– Empiric treatment should cover MRSA
– CA-MRSA sensitive to TMP-SMX
– CA-MSSA and streptococcus sensitive to cephalexin
SIRS criteria
Two of the following conditions:
1.) Temp above 38 or below 36
2.) HR above 90bpm
3.) RR above 20
4.) WBC above 12,000 or below 4,000 or >10% banded neutrophils
Sepsis criteria
SIRS criteria plus present source of infection
1.) CT scan of brain multiple diffuse hyperdense foci
2.) CT Scan of chest– bilateral patchy areas of consolidation and ground-glass opacities in lungs, small focal effusions, pleural effusions
Staphylococcus aureus sepsis
– infects all tissue of the body
– Toxins leading to food poisoning, enterocolitis, epidermal necrolysis, TSS, and necrotizing pneumonia
– VIRULENCE: adhesions to bind and penetrate, enzymes for tissue breakdown, cytolytic toxins, and superantigens
Superantigens
inappropriately activate T cells and likely contribute to shock
Panton-Valentine Leukocidin (PVL)
A cytotoxin found in most strains of CA-MRSA. It creates pores in the membranes of cells surrounding infection and destroys invading leukocytes. Necrotic lesions of skin and mucosa
– Gene acquired from bacteriophage (lysogenic)
Three ways for bacteria to initiate infection
1.) breach the skin
2.) Systemic disease (lung–> skin)
3.) Toxin-mediated damage (wound–> toxin–> bigger wound)
Skin defenses
1.) Dry outmost protective layer
2.) antimicrobial peptides produced by epithelial cells
3.) Low pH of sebum
4.) Low pH and high salt content of sweat
5.) presence of lysozymes
6.) Langerhans cells (resident phagocytes) in epidermis
7.) competition with normal flora for resources on the skin
Acne/Folliculitis
Follicle-associated lesion.
propionibacterium acnes (G+, aerotolerant) in follicle–> releases lipase to digest surplus trapped oil –> lesion + local inflammation
Treatment: topical agents/ oral antibiotics
Imepetigo
Superficial bacterial infection that causes skin to flake/peel, honey colored crusts. Highly contagious, seen a lot in children.
Caused by: Staphylococcus aureus or Streptococcus pyogenes
Diagnosis: observation, topical mupirocin or oral cephalexin
Staphylococcus aureus
Bacteria, G(+), cocci clustered, Catalase(+), Coagulase(+), Uses protein A, coagulase, and hemolysins/leukocidins
Superficial (boils) and deep (furuncle/carbuncle). Common in surgical wounds. Seen in TSS, and scalded skin syndrome (ET-A and ET-B)
Staphylococcus Aureus virulence factors
1.) Hyaluronidase (breaks down connective tissues)
2.) Staphylokinase (lyses formed clots)
3.) Lipase (breaks down fat)
Streptococcus pyogenes
Bacteria, G(+), cocci chains, Catalase(-), beta-hemolytic, bacitracin sensitive
Common in impetigo, erysipelas, cellulitis, TSS, necrotizing fasciitis. Strep, scarlett fever, pneumonia, glomerulonephritis, and rheumatic fever (Strep=glomneph + rheumatic, skin= only rheumatic)
Streptococcus pyogenes virulence factors
1.) streptokinase (converts plasminogen to plasmin)
2.) M protein (resists phagocytosis)
3.) Hyaluronidase (breaks down connective tissue)
4.) DNase (digests DNA)
5.) Streptolysin O (destroys RBCs)
6.) Streptolysin S (destroys WBCs)
~ encoded by lysogenized prophage
Catalase test
Differentiates between C(+) microccal and staphylococcal species from C(-) streptococcal species
– Catalase is an enzyme that breaks down hydrogen peroxide to O2 and H2O (C(+) = rapid release of oxygen bubbles)
Coagulase test
Differentiate between staphylococcus aureus (coag+) from other staphylococcus that are Coag- (ex. staph epidermidis)
–When mixed with plasma, Coag+ will cause clumping or solid media
Novobiocin sensitivity
Differentiate between Staph saprophyticus (resistant) and Staph epidermidis (sensitive)
– Novobiocin inhibits bacterial DNA gyrase in susceptible (epidermidis) microorganisms
Cellulitis
Fast-spreading infection in the dermis and in the subcutaneous tissues. Pain, tenderness, and warmth on skin. Fever and swelling of lymph nodes draining the area,
–Most common cause in healthy people: Staph aureus, strep pyogenes. in infants: group B streptococci, occasionally from varicella
Staphylococcal scalded skin syndrome
Dermolytic condition caused by staph aureus, shedding occurs within the dermis. Most common in newborns and babies.
Gas gangrene
Caused by clostridium perfringens (anaerobic) that creates many exotoxins (ex. alpha-toxin). Spores of these species can be found in soil, human skin, and in the human intestine/vagina.
Treated with: penicillin and clindamycin
Clostridium perfringens
Bacteria, G(+), Bacilli, spore-forming, obligate anaerobe, only non-motile Clostridium member. Present in cellulitis (cracked skin), gas gangrene (myonecrosis with crepitus) (deep muscle lacerations), food poisoning
Treated with: surgical removal of infected areas. Hyperbaric oxygen to kill anaerobic organisms. Penicillin or clindamycin (only effective in local, weak infections)
Pseudomonas aeroginosa
Bacteria, G(-), bacilli, lactose non-fermenter, oxidase(+), glucose non-fermenter. “HOT TUB FOLLICULITIS”
–Comes from burn wound infection and folliculitis (hto water bacteria)
A vertical mattress suture is ideal for what kind of wound closure?
Both deep and superficial layers– good for gaping wounds
A horiztonal mattress suture is good for what kind of wound?
High tension wounds, and brittle skin (prevents tears)
Wound closure
Primary: Sutures, staples, tape, adhesives
Secondary: organic healing via the body
Contraindications for wound closure
- wound infection
- gross contamination
- infected tissue
- non-cosmetic wounds that come late to medical attention
- Animal bites
- Deep puncture wounds that cannot be irrigated properly
Time frame for sutures
Clean, uninfected lacerations on any part of the body in healthy patients: 18 hours
Facial wounds: 24+ hours
Wound management
Evaluate: Vascular, neuro, bleeding, healing expectation
Anesthesia: Local v digit v field block
Wound toilet: copiously irrigate
Wound closure: type and size
Complications of wound closures
Hypertrophic scars (keloids)
Wide scars (tension in collagen reformation)
Wound Dehiscence (non-adherence, wound splitting open)
Infection
Absorbable sutures
Gut, Chromic, Vicryl, Monocryl, PDS
Non-absorbable sutures
Prolene, Nylon, Stainless steel (bones/cartilage), Silk
Natural vs. synthetic
Natural: intense inflammation (ex. cow/sheep intestines, chromic/gut, silk)
Synthetic: less inflammation (ex. vicryl, monocryl, PDS, prolene, nylon)
Monofilament sutures
Appears as a single strand of suture material, minimal tissue trauma, ties smoothly, requires more knots, possesses memory (ex. monocryl, PDS, prolene, nylon)
Multifilament sutures
Fibers are twisted or braided together, greater resistance in tissue, fewer knots required (ex. vicryl, chromic, silk)
Suture size
zero is the reference size. More zeros is smaller
5-0 < 4-0 < 3-0 <2-0
Simple sutures
Simple interrupted stitches that are individually knotted, it used for uncomplicated laceration repairs and wound closures
Horizontal mattress sutures
Provides added strength, used in tough skin/calloused skin.
Two step stitch: simple stitch made, needle reversed and 2nd simple stitch made adjacent to first
Vertical mattress sutures
precise approximation of skin edges with eversion, provides additional strength to wound tension (for large gaping wounds)
Two step stitch: simple stitch made “far, far” relative to wound edge (large bite). needle reversed and 2nd stitch made inside first “near, near”
Arms and scalp sutures
4-0, for 7-10 days
Face sutures
5-0 or 6-0, for 3-5 days
Hands, feet, legs, trunk
3-0, 4-0, 5-0, for 10-14 days
Palms or soles
3-0, 4-0, for 14-21 days
Classical complement pathway
- Triggered by antigen binding to IgG (2) or IgM (pentamer)
- C1q, C1r2, C1s2
- Covalent attachment of C4b and C3b to surfaces via thioester bonds
- C4b2a is the C3 convertase
- C4b2a3b is the C5 convertase
MBL complement pathway
- Doesn’t require specific antibody, triggered by polysaccharide structure of microbes
- C1 independent formation of of the classical pathway C3 convertase (C4b2a)
- MBL –> MASP1 and MASP2 (like C1q –> C1r C1s in classical)
Alternative complement pathway
- Easily reactive to any foreign materials, LPS, and nucleophiles
- Oldest pathway
- Factor B and Factor D and properdin
- C3bBbC3b is the C5 convertase
- FB amplies C3bB binding
- FI, FH decays/inactivates C3b
C3 convertases
Classical: C4b2a
MBL: C4b2a
Alternative: C3bBb
C5 convertase
Classical: C4b2aC3b
MBL: C4b2a3b
Alternative: C3bBbC3b
Terminal lytic pathway
Occurs after the binding of C5b, 6, 7, 8, 9
- 9 is not required but the lysis will be SLOW without it
- osmolysis by puncturing a hole in the cell membrane
S protein in the fluid phase
C5b-9 may bind S protein in fluid phase (unattached), inhibiting lysis
Regulators of complement activation in plasma
Classical pathway: C1 INH, C4BP (no cleavage of C4)
Alternative pathway: Factor H (C3bBb inhibitor)
Membrane attack complex: S protein (inhibitor, binds C5b-7 and blocks its integration into membranes)
Membrane bound regulators of Complement activation
C3 convertase: CD46 cofactor activator
C3 convertase: CD55 decays acceleration
membrane attack complex: CD59, inhibitor of C9 (on your cells)
Factor H
A fluid phase inhibitor of alternative pathway C3 convertase. It binds C3bBb and dissociates the Bb. “decay acceleration of convertase” creates iC3b
- Also a cofactor for cleavage of C3b by Factor I
Things C4b and C3b can do
1.) Participate in continued pathway activation leading to MAC
2.) interact with CR1 –> opsonization clearance of immune complex
3.) degrades into fragments –> interacts with CR2 and CR3 –> opsonization clearance of immune complex
4.) augmentation of humoral immunity (x100)
Interaction with complement receptors
C3b: CR1 –> Clearance of immune complex
iC3b: CR1, CR2, CR3 –> Clearance of immune complex
C3d: CR2 –> Augment humoral immunity
CR1 (CD35) activity
Major ligands: C3b, C4b
- RBCs, WBCs, T cells, B cells
- transport immune complexes by RBC
- promotes immune adherence (opsonized)
- promotes phagocytosis with Fc receptors
- Blocks formation of C3 convertase
Binding of C3b to the Ab:ag complex
interferes with lattice formation, limiting its growth and keeps Ab:ag complexes soluble
Immune complex transport
Major mechanism for removal of ICs. ICs coated with C3b bind to CR1 (on RBC) and transport them to the spleen/liver/etc for clearance via macrophages
CR2 (CD21/CD19/CD81)
Major ligands: C3d, C3dg, iC3b
- B CELLS, follicular DC, some T cells
- B cell co-receptor, bind EBV
- augments stimulation of the B cell to increase humoral immune response
CR3 (CD11b/CD18)
CR4 (CD11c/CD18)
Major ligand: iC3b
- Cell adhesion binds immune complex
- monocytes, macrophages, neutrophils, NK, T cells
What are the anaphylatoxins
GPCRs (7-transmembrane proteins)
C3a and C5a via C3a receptor, C5a receptor, respectively
– potent inflammation causers: Chemotaxis, smooth muscle contraction, increased vascular permeability, degranulation of mast cells, neutrophil activation
C1, C2, C4 deficiency
Immune-complex disease
C3 deficiency
Susceptibility to encapsulated bacteria
C5-C9 deficiency
Susceptibility to Neisseria (meningitis)
Factor D, prosperdin (Factor P) deficiency
Susceptibility to encapsulated bacteria and Neisseria but NO immune-complex disease
Factor I deficiency
Similar effects to deficiency of C3
Immune complex Disease
– Type III hypersensitivity
– Ex. Lupus (SLE), Rheumatoid arthritis, glomerulonephritis
Complement deficiencies
–increase IC or autoimmune disease (Classical pathway or C3 deficiencies)
– Infections (Classic, alt, MBL pathways)
– Neisseria infections (alt pathway and terminal lytic)
aHUS (atypical hemolytic uremic syndrome)
MCP (CD46), Factor I, Factor H, C3, Factor B
damage to platelets, RBCs, and kidney inflammation. Leads to systemic thrombotic microangiopathy. Blood clot disorder in small vessels from overstimulation of the alternate pathway
Age-related macular degeneration (eye)
Polymorphisms in factor H
Autoimmune-like conditions, including paroxysmal nocturnal hemoglobinuria
DAF, CD59, CD55
Hereditary angioedema (HAE)
C1 INH
– Reccurent episodes of localized edema in skin, GI tract, or larynx
– C1 inhibitor inhibits C1 esterase (too much activation) –> leads to over consumption –> C4, C2
– Also inhibits MASP, kallikrein, plasmin, Factor XIa, Factor XIIa, and bradykinin B2 receptor
Paroxysmal nocturnal hemoglobinuria
Deficiency on CD55 and CD59
Treatment for C1 INH
– Anabolic steroids to increase synthesis of C1 INH
– Purified C1INH (but expensive)
– Kallikrein inhibitors and bradykinin B2 receptor inhibitors (excess kinin formation responsible for the episodes of edema)
DAF (CD55 and CD59) deficiency and treatment
DAF: in a post-translational modification of the peptide anchors that bind the proteins to the cell membrane
– increased susceptibility of erythrocytes to MAC-mediated lysis (PNH, RBC osmolysis)
Treatment: antibody to C5 (eculizumab) reduces hemolysis (HOWEVER: inhibiting C5 can lead to susceptibility to neisseria infections)
Superficial fungal skin infections
- Pityriasis versicolor
- Tinea nigra (tinea= gnawing worm or moth)
Cutaneous fungal skin infections
Dermatophytosis (other Tineas)
Subcutaneous fungal skin infections
- Sporotrichosis
- Chromoblastomycosis
~ RARE
Cutaneous/systemic fungal skin infections
- Candidiasis
- Cryptococcosis
- Blastomycosis
Pityriasis (tinea) versicolor
Malassezia furfur
- epidermal infections on the back, chest, neck, and upper arms. Painless but may itch, scaling, and can recur easily
- spaghetti and meatballs (spores and hyphae)
- Diagnosis by KOH mount/prep of skin scraping
Tinea Nigra
Exophiala werneckii (Hortaea werneckii)
- Tropical infection. Florida, North, South Carolina
- Dark brown/black patches on the soles of the hands or feet. Irregularly shaped but well circumscribed, fine scale, painless, generally does not recur (long time to clear)
- Diagnosis by KOH mount/prep of skin scraping. Expect to see hyphae that are thick, irregular, and have a slight color
Effective treatment for Pityriasis versicolor and Tinea nigra
- application of dandruff shampoo containing selenium sulfide
- topical antifungals
~ Skin discoloration will take longer to resolve in pityriasis versicolor compared to the M. furfur infection
Dermatophytoses
Trichophyton- most common in USA (microsporum, epidermophyton)
- Lives on you dead stuff
- Secrete keratinase (digests keratin, hair, skin, nails)
- Warm + moist skin = occurrence and recurrence
Ringworm
Tinea corporis (body) dermatophytoses cutaneous infection
- itchy red rash presents on the trunk/extremities
- Centrifugally from a core, leaving a central clearing
- expanding raised red border, scaling
- common in children
Jock itch
Tinea Cruris (groin) dermatophytoses cutaneous infection
- itchy red rash extending anywhere from the groin, upper thigh, and perineum to the perianal region
- Similar pattern to tinea corporis
- common in children
Athlete’s foot
Tinea pedis (feet) dermatophytoses cutaneous infection
- Trichophyton rubrum
- common in adults rather than children
- co-present with onychomycosis
Scalp ringworm
Tinea capitis (scalp) dermatophytoses cutaneous infection
- Trichophyton tonsurans
- Male, urban, african decent
- 5-10 year olds, very transmissible
Onychomycosis
Tinea unguium (nail) dermatophytoses cutaneous infection
- Trichophyton rubrum
- Clinical signs resemble psoriasis
Acute: spongiosis, acanthosis, pappillomatosis with edema, and hyperkeratosis
Chronic: nail bed = hyperkeratotic, thickened, nail detaches or becomes distorted
Candidiasis
Candida albicans
- skin, mouth, GI tract
- YEAST, pseudohyphal form
- diaper rash, skin folds, oral thrush, vulvovaginal
Diaper rash
Candida albicans: initiates with irritant dermatitis
fecal bacteria –> urease –> urea in urine –> increased pH –> overgrowth of c. albicans
Sporotrichosis
Caused by sporothrix schenckii on soil and plants
- rose gardner’s disease
-Dimorphic: 37C=yeast that buds, 25C=hyphae
- cultured on Sabouraud SDA