Bacterial infections-Andrews/Bolognia Flashcards
Why do gram positive bacteria stain purple/violet?
Thick layer of Peptidoglycan in the cell wall does not let crystal violet wash out
What is beta hemolysis?
complete lysis of red cells surrounding the colony
What is alpha hemolysis?
partial or “green” hemolysis associated with reduction of red cell hemoglobin.
Is group A strep usually beta or alpha hemolytic?
Beta hemolytic
A painful, erythematous nodule with pale center located on fingertips, thenar, and hypothenar eminences in bactremia/septicemia/endocarditis?
Osler Node (OUCHY)-From immune complex deposition and small vessel vasculitis
A non-tender, angular hemorrhagic lesions on palms and soles in bactremi/septicemia/endocarditis?
Janeway lesions-septic emboli forming microabscesses
What is the pathogenesis of community acquired MRSA?
Altered penicillin binding protein (PBP) called PBP2a-site where antibiotics bind to interrupt cell wall,
Virulence-Panton-valentine leukocidin (PVL)-Pore forming cytotoxin – can cause destruction of leukocytes and tissue necrosis
What is the most common cause of folliculitis? Associated with swimming pools and jacuzzi’s? Associated with long term antibiotic therapy such as for acne or rosacea?
Staph aureus, pseudomonas, gram-negatives
What is the name for a superficial folliculitis? Deep folliculitis?
Bockhart’s impetigo, sycosis barbae
What is the most common causes of pygenic paronychia if there is abscess formation? If erythema and swelling? Chronic swelling?
Staph Aureus, Strep pyogenes, candida
What is the Splendore-Hoeppli phenomenon
granule consisting of non-filamentous bacteria in a hyaline matrix w/ IgG and Complement C3 in “bunch of grapes” cluster,eosinophilic periphery with basophilic center in Botryomycosis?
What is the most common cause of botryomycosis?
Staph Aureus
What is the most common cause of pyomyositis? What is the most common location in kids and in the tropics? Most common location in temperate areas, HIV, DM, IVDA?
Staph aureus, thigh, deltoid
In impetigo contagiosa what types are related to nephritis?
M type 2
In bullous impetigo what causes the reaction?
exfoliative toxins A & B - S. aureus, group 2 phage type 71 (or 55); that bind to desmoglein 1 on the extracellular domain
What causes staph scalded skin syndrome?
S. Aureus exfoliative toxins A & B from group 2 phage strains 55 & 71 bind to desmoglein 1
What causes toxic shock syndrome?
S. Aureus exotoxin (TSST-1 toxin) superantigen or group A strep M types 1 & 3-exotoxin A 80% of the time
What causes scarlet fever?
Exotoxin via group A b-hemolytic strep types A, B, and C that leads to a delayed hypersensitivity rxn
What is Fournier’s gangrene?
Localized type of necrotizing fasciitis (type 1-polymicrobial) of scrotum or penis
What is Meleney’s gangrene?
polymicrobial necrotizing faciitis as a complication to surgical trauma
What are the tree types of necrotizing fasciitis?
Type I – polymicrobial
TypeII – group A streptococcal
Type III – gas gangrene or clostridial myonecrosis
What streptococcal species is common cause of meningitis and sepsis in the neonate?
Strep agalactiae
What streptococcal species would you be concerned about in the hands of a fisherman?
Streptococcus iniae
If you saw purple swelling in the finger webs but sparing the phalanges in a fishermen what would you be thinking?
Erysipeloid of Rosenbach caused by Erysipelothrix rhusiopathiae
What is the pathogenesis of bacillus anthracis?
Polyglutamic acid capsule – inhibits phagocytosis
Two EXOTOXINS:
Edema toxin= Edema Factor (EF) + Protective Antigen (PA)
Affects water homeostasis leading to edema through increased cAMP levels
Lethal toxin = Lethal Factor (LF) +PA
Causes shock and death by realease of TNF -alpha and IL-1beta
In erythrasma what causes the coral-red fluorescence w/ Wood’s lamp (365 nm)?
Coproporphyrin III
What causes erythrasma?
Corynebacterium minutissimum
What causes pitted keratolysis?
Corynebacterium; Kytococcus (Micrococcus) sendentarius-Elaborates serine proteases K1 and K2 keratin-degrading serine proteases that destroy the S.Corneum
What causes trichomycosis axillaris?
Corynebacteria tenuis
What is the mechanism that causes gas gangrene?
α-toxin – biological activity similar to phospholipase C and sphingomyelinase
Perfringolysin – disrupts endothelial cell integrity, impairs recruitment of phagocytes, and induces intravascular platelet aggregation
from C. perfringens (most common)
What do you use to treat actinomyces? Nocardia?
SNAP-Sulfa(bactrim) for nocardia, actinomyces use penicillin G
What is the strongest risk factor for recurrence of erysipelas/cellulitis in the lower extremity?
lymphedema
What is catalase?
enzyme that serves to protect the cell from toxic effects of high concentrations of hydrogen peroxide (H2O2) by catalyzing its decomposition into molecular oxygen and water, without the production of free radicals
What clinical feature helps you differentiate between sycosis barbae (vulgaris) from tinea barbae?
Tinea barbae never involves the upper lip where sycosis barbae (vulgaris) usually does
Differential Dx of Slendore-Hoeppli immune complex deposition?
Actinomycosis Mycetoma Sarcoid Botryomycosis Sporotrichosis Nocardia
What are pastia lines and it is associated with what?
accentuation over skin folds, linear petechial eruption, usually antecubital or axillary folds
associated with Scarlet Fever
What are pastia lines and it is associated with what?
accentuation over skin folds, linear petechial eruption, usually antecubital or axillary folds
associated with Scarlet Fever
What is the treatment for listeriosis?
AMPICILLIN or bactrim
What is the differential for Splendore-Hoeppli phenomenon ?
Actinomycosis Mycetoma Sarcoid Botryomycosis Sporotrichosis Nocardia
What is the criteria for diagnosing rheumatic fever?
Two major criteria, or one major and two minor criteria, and signs of a previous strep infection
What are the major criteria in diagnosing rheumatic fever?
Arthritis in several joints (polyarthritis)
Heart inflammation (carditis)
Nodules under the skin (subcutaneous skin nodules)
Rapid, jerky movements (chorea, Sydenham chorea)
Skin rash (erythema marginatum)
What are the minor criteria in diagnosing rheumatic fever?
Fever
High ESR
Joint pain
Other laboratory findings
