Micro: bacterial Infection Flashcards
Major virulence factor of Staph epidermidis
Biofilm formation
Most common microbe in skin infections
S. aureus
Honey crusted lesions
Impetigo
-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
- With good cell mediated immunity (CMI): tuberculoid leprosy
- 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
- Edema Factor (EF): activates adenylate cyclase increasing cAMP and disrupting water homeostasis
- Lethal Factor (LF): induces cellular apoptosis
Unique structural feature of B. anthracis
Glutamic acid capsule
Virulence factors of N. meningitidis
Capsule
LOS
Pili
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
- Stage 1: erythema migrans (bullseye rash at tick bite site)
- Stage 2: arthritis, fatigue, Bell Palsy, meningitis, peripheral neuropathy, AV node block
- 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
