Derm bacteria Flashcards
What is the causal agent of rat bite fever?
Streptobacillus moniliformis
Explain what determines whether a person who contracts Mycobacterium leprae will develop tuberculous leprosy or lepromatous leprosy
It is all dependent on the CMI, so if that is good they will only have tuberculoid leprosy (less severe). If they have poor CMI, they will develop lepromatous leprosy
Define bulla
vesicle greater than 5 mm
How is staph aureus transmitted?
direct contact or fomites
Which bug creates a rash that looks a bit like the lupus rash?
Streptococcus pyogenes–erysipelas
Compare the rash of RMSF to Scrub typhus. What are the causal agents, respectively?
RMSF is a centripetal rash from palms and feet to trunk. Scrub typhus is trunk and outward; Ricketsia rickettsii and Orentia Tsutsugamushi (the greatest name in all of microbiology)
Discuss the 3 types of necrotizing fasciitis
Type I: polymicrobial, at least 1 anaerobe in combination with more than 1 facultative bacteria; Type II: streptococcus pyogenes with or without staph; Type III–gas gangrene, Clostridium perfringens
What is the goal of the human microbiome project?
To determine ALL of the normal flora of the human body
In general, what is the most important virulence factor for Strep pyogenes?
M protein, it evades phagocytosis
Define macule
flat and circular lesion 5 mm or less in diameter
How can you differentiate (lab-wise) N. gonorrhea and N. meningitidis?
Meningitidis metabolizes maltose and glucose whereas gonorrhea metabolizes glucose only (Carty misspoke)
What causes erysipelas? Erysipeloid?
Erysipelas = Strep pyogenes; Erysipeloid = Erysipelothrix rhusiopathiae
How does staphylococcal protein A work?
Binds Fc portion of IgG to inhibit complement activation
T/F: a Vibrio vulnificus infection can be contracted from warm seawater and is an extremely painful but self-limiting infection
False, it is from warm seawater and it is painful but it is rapidly progressive and can lead to shock/death in 50% of cases
What antigen is missing from LOS in comparison to LPS?
the O antigen
Why do people with lepromatous leprosy have flat noses?
Mycobacterium leprae destroys the septum of the nose
Causal agent of the infamous fish tank granuloma
Mycobacterium marinum
How does cutaneous anthrax present?
PAINLESS black eschar
What is the major opportunist of the normal skin flora?
Staph epidermidis on prosthetic devices esp. > 3 months
What are the 3 types of Bacillus anthracis infection?
Pulmonary (mediastinal widening), GI, and cutaneous which is the most common
What kind of capsule does B. anthracis have?
Poly D-glutamic acid
What is present in the blisters from scalded skin syndrome and bullous impetigo? What is different between these two?
Staphylococcal exfoliative toxins but NO BUGS. Bullous impetigo is a localized version of scalded skin syndrome
What is the main virulence factor of s. epidermidis?
biofilm
Who gets Cat Scratch disease and who gets Bacillary angiomatosis? Caused by?
Cat scratch is Bartonella henselae in immune competent pt and Bacillary angiomatosis is Bartonella henselae in IC pts
What bug and virulence factor causes toxic shock syndrome?
Staphylococcus aureus; TSST-1
How can you treat necrotizing fasciitis? (3)
Surgical debridement and/or amputation; combination antibiotics; hyperbaric chamber
What is infected by Ricketsia ricketsii?
vascular endothelial cells, it is obligate intracellular
Where does the name Propionibacterium acnes come from?
The fact that they metabolize sebum into propionic acid
Define papule
discrete, pus-filled, raised lesion
What bug looks like a tennis racked on light microscope? What should you think if you see tennis rackets on EM?
Clostridium perfringens; Birbeck granules of Langerhans Histiocytosis
What derm lesion is pathognomonic for Pseudomonas aeruginosa?
Ecthyma gangrenosum
What 2 bugs may cause impetigo?
Staph and strep pyogenes
How often does Clostridium perfringens divide?
every 12 minutes! Very rapid progression!
How does one get Erysipelothrix rhusiopathiae? G stain?
GI tract of animals–causes erysipeloid; gram positive rods
T/F: the sandpaper rash of scarlett fever contains catalase negative cocci in chains
false, the sandpaper rash is formed from the pyrogenic exotoxins of strep, there are no bugs (Spe)
What is Hansen’s disease?
Leprosy
What will be the key piece of information in the H&P of a necrotizing fasciitis case?
The pain will be disproportionate to the appearance of the infected area
An antibody to what is being detected in the non-treponemal test?
cardiolipin
Why do teens get acne more so than other age groups?
Hormones trigger the production of sebum which results in “food” for Propionibacterium acnes (to metabolize into propionic acid)
What may staph folliculitis progress to?
First a furuncle which is essentially a boil or abscess, then a carbuncle which is a furuncle that has gone deeper and spread laterally through the fascia
What bugs cause impetigo? Bullous impetigo?
Impetigo is both staph aureus and group A strep; bullous impetigo is staph aureus only
Regarding Mycobacterium leprae describe 1) Temperature requirements 2) Gram stain 3) Incubation period
1) grows in lower temps 32-34 C 2) No gram stain, it is acid fast rod 3) YEARS
Why does Pseudomonas cause hot tub folliculitis?
The heat opens up the pores and lets the bug in
Gram stain and virulence factor for Clostridium perfringens
Gram positive anaerobic rod, alpha toxin = lecithinase (lecithinase breaks down lipids in the cell membrane leading to cell death)
Gram stain and shape of Proprionibacterium acnes
Gram positive rods
What is significant about Neisseria spp. Pili?
They undergo antigenic variation
Define vesicle
fluid-filled, raised lesion 5 mm or less
Gram stain of Pastuerella multocida?
Bipolar gram negative rods and oxidase positive
Above what age must a child be to receive the Menomune vaccine to meningococcus?
2
Which gene allows for MRSA to be resistant to methicillin?
mecA (also resistant to nafcillin, dicloxacillin, and oxacillin)
What are 2 important areas to look for the rash of secondary syphilis?
palms of hands and soles of feet
What is associated with leonine facies?
Lepromatous leprosy
What exactly is entering the skin in a cutaneous anthrax infection?
endospores, not gram positive rods
Describe the 3 basic mechanisms of pathogenesis that organisms can use to infect the skin or have skin manifestations
1) infection from a break in the skin 2) a skin manifestation of systemic infection (meningococcemia) or 3) toxin that circulates to infect the skin
Define patch
a macule (or group of macules that has coalesced) to become greater than 5 mm in diameter
What is Ritter’s Disease? What is the major concern with it?
Scalded Skin Syndrome from the exfoliative toxins of staphylococcus; the main concern is dehydration and/or secondary infections
