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Flashcards in Micro: bacterial Infection Deck (34):

Major virulence factor of Staph epidermidis

Biofilm formation


Most common microbe in skin infections

S. aureus


Honey crusted lesions

-caused by S aureus and S. pyogenes


Cause of Scalded Skin Syndrome.

Exfoliative toxins produced by S. aureus
-usually infants and IC elderly patients
-mortality of the disease is due to dehydration and secondary infection


Cause of bullous Impedigo

Exfoliative toxins produced by S. aureus
-localized form of Scalded Skin Syndrome


Cause of Toxic Shock Syndrome and its general pathogenesis.

TSST-1 superantigen toxin released by S. aureus
-toxin induces massive immune response leading to fever, hypotension and shock, macular erythematous rash
-eventual multiple system organ failure from the shock


Major cause of cellulitis

S. pyogenes infection of subcutaneous tissue
-following some type of skin trauma


Describe the 3 types of Necrotizing Fasciitis

Type 1: polymicrobial, at least 1 anaerobe along with more than 1 facultative bacteria
Type 2: S. pyogenes w/ or w/o S. aureus
Type 3: Gas gangrene caused by Clostridium perfringens


Diagnostic feature of Necrotizing Fasciitis noted on physical exam.

Pain that is disproportionate to the appearance of the infected area.


Cause of Scarlet Fever

Complication of pharyngitis caused by S. pyogenes
-result of damage caused by pyrogenic exotoxins


Which S. pyogenes exotoxins can cause a Toxic Shock-like Syndrome?

Spe A and Spe C
-both are considered superantigens that can induce a massive immune response


Cause of Erysipelas

Butterfly pattern bright red rash appears on the face with raised borders due to a superficial skin reaction to the S. pyogenes exotoxin.
-there is notable lymphadenopathy


Major causative agent of acne and the pathogenesis of the lesions.

Propionibacterium acnes
-excessive sebum production by hormones causes increased bacterial growth and recruitment of WBCs resulting in inflammation and pimples


Causative agent of Hansen Disease and the two types.

Mycobacterium leprae
1. With good cell mediated immunity (CMI): tuberculoid leprosy
2. With poor CMI: lepromatous leprosy


Describe the presentation of Tuberculoid leprosy.

Dry, blotchy, red patch lesion with associated nerve damage leading to sensation loss


Describe the presentation Lepromatous leprosy.

Skin thickens and nodules form. Thickening of nostrils, ears, and cheeks with possible destruction of the nasal septum.


Fish tank granuloma.

Small papule caused by infection of Mycobacterium marinum. Microbe enters thru a break in the skin.


Folliculitis after spending time in a hot tub.

Pseudomonas a.


Characteristic ulcerated skin lesion when a Pseudomonas a. infection enters the bloodstream.

Ecthyma Gangrenosum


Painless black eschar

Cutaneous Anthrax
-caused by B. anthracis


Describe the anthrax toxin.

PA is present with either EF or LF (not both)
1. Protective Antigen (PA): binds cell membrane and mediates endocytosis of EF or LF

2. Edema Factor (EF): activates adenylate cyclase increasing cAMP and disrupting water homeostasis

3. Lethal Factor (LF): induces cellular apoptosis


Unique structural feature of B. anthracis

Glutamic acid capsule


Virulence factors of N. meningitidis



Lab test to differentiate the two major Neisseria species.

meningitidis metabolizes maltose and glucose
gonorrhoaea metabolisms only glucose


Complication of Meningococcemia caused by N. meningitidis.

Waterhouse-Friderichsen syndrome
-bilateral hemorrhage of the adrenal glands causing coma and death


Copper colored rash over entire body.

Sequelae of secondary Syphilis (Treponema pallidum)


Describe the progression of Lyme Disease

Infection by Borrelia burgdorferi
1. Stage 1: erythema migrans (bullseye rash at tick bite site)
2. Stage 2: arthritis, fatigue, Bell Palsy, meningitis, peripheral neuropathy, AV node block
3. Stage 3: chronic arthritis, encephalopathy


Pathogenesis of Rocky Mountain Spotted Fever.

Rickesttsia rickettsii infects phagocytes
-spreads to vascular endothelium where it infects the endothelial cells
-causes a rash that begins on the hands and feet and spreads inward toward the trunk (cenTRIPETAL spread)
-vector is a tick


Pathogenesis of Scrub Typhus.

Orientia tsutsugamushi infects endothelial cells causing an itchy rash that starts on the trunk and spreads to the extremities (cenTRIFUGAL spread)


Pathogenesis of Gas Gangrene

Clostridium perfringens infects a deep cut
-bacteria use alpha toxin (lecithinase) which breaks down lipid cell membranes primarily in muscle cells
-also produces gas bubbles leading to a crepitus sound noted on physical exam
-considered a form of necrotizing fasciitis so the presentation will be pain out of proportion to the appearance of the lesions


Infectious agent causing a lesion, by gram positive rod, after coming into contact with contaminated meat or animals.

Erysipelothrix rhusiopathiae


Wound exposed to salt water.

Vibrio vulnificus
-can cause systemic disease with a 50% mortality rate if untreated


Describe the pathogenesis of Cat Scratch Fever.

Infection by Bartonella henselae
-bacteria grow intracellular causing inflammatory reaction
-in IC patients can progress to Bacillary Angiomatosis with cutaneous papules resembling Kaposi sarcoma


Bi-polar staining and bone pain.

Infection with Pasteurella multocida
-usually from dog or cat bite
-infection causes osteomyelitis