OLD MICRO Flashcards
Which dermatologic virus is vaccinated using a vaccine containing a different virus than that which is being vaccinated against?
Smallpox is vaccinated for with a live cowpox vaccine
Where do most of the subcutaneous mycoses come from?
soil
What viral family is measles in?
paramyxoviridae
Define papule
discrete, pus-filled, raised lesion
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 kind of systemic infections can Trichosporon cause? What enzyme is it positive for in the lab?
Endocarditis of prosthetic valve or on native valve if IVDU; urease
Which dermatophytoses are most common in A) Men and B) Women?
A) tinea capitis, tinea pedis, and tinea cruis B) tinea unguinum
How does Sporothrix spread?
along the chain of lymphatics
What is contained in the granules of a Mycetoma?
microcolonies of the agent embedded
How is staph aureus transmitted?
direct contact or fomites
An antibody to what is being detected in the non-treponemal test?
cardiolipin
How are HPV and MCV transmitted?
direct contact and fomites
When did routine smallpox vaccinations stop in America? When was it GLOBALLY eradicated?
1972, 1979
What is the most common complication of shingles?
post-herpetic neuralgia
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)
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)
Define vesicle
fluid-filled, raised lesion 5 mm or less
What is the most common zoophilic cause of tinea capitis worldwide?
Microsporum canis
What is a kerion?
an intense, painful, and boggy suppurative reaction often on the back of the neck and associated with cervical lymphadenopathy.
What immune response is needed to control Candidal infections?
T cell
What is the most important historical feature of HHV-6?
Extremely high fever that abruptly stops and then there is a maculopapular rash
If you are not vaccinated against VZV, what is the probability you will be infected when exposed to someone with it?
90%
Which strains of HPV are responsible for dysplasia of the cervix and white plaques
16 and 18
What virus causes herpangina?
Coxsackie A–this is basically hand, foot, and mouth without the hand and foot. And it isn’t caused by the same serotype? So I guess it’s actually completely different. Whatever.
How does staphylococcal protein A work?
Binds Fc portion of IgG to inhibit complement activation
Why is possible to achieve lifelong immunity with measles?
there is only 1 antigenic type of measles
What is the causal agent of rat bite fever?
Streptobacillus moniliformis
What is infected by Ricketsia ricketsii?
vascular endothelial cells, it is obligate intracellular
What family is molluscum contagiosum in?
poxviridae
How would you differentiate between the two causes of tinea capitis that fluoresce?
HISTORY, Microsporum canis is from an animal and Microsporum andouini is from a human
Regarding the appearance of the rash (not evolution of) how is measles different from german measles?
Germn measles is lighter in color (pink)
What is associated with leonine facies?
Lepromatous leprosy
What is a dermatophytid?
It is a secondary rash to the dermatophyte, it is caused by the immune system so there are no fungi present
Where do the following replicate A) HPV B) HHV-6 C) B19 D) HHV-8
A) mature keratinocytes (infects basal) B) T and B cells C) erythroid precursor cells D) vascular endothelial cells
What bugs cause impetigo? Bullous impetigo?
Impetigo is both staph aureus and group A strep; bullous impetigo is staph aureus only
Above what age must a child be to receive the Menomune vaccine to meningococcus?
2
Name the 3 enveloped DNA families
Hepadnaviridae, herpesviridae, and poxviridae
What is unique of the cell walls of Hortae werneckii?
They are melanized, it is a dematiaceous fungus
What is the major demographic you are concerned about in terms of complications, for B19?
sickle cell (and, though not mentioned, thalassemias as well)
Who would be most at risk of a dermatophyte becoming a chronic issue?
Can happen in anyone but HIV and IC
Gram stain of Pastuerella multocida?
Bipolar gram negative rods and oxidase positive
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
Which strains of HPV are most responsible for genital warts
6 and 11
Gram stain and shape of Proprionibacterium acnes
Gram positive rods
Name the 3 naked DNA virus families
Papovaviridae, Adenoviridae, and Parvoviridae
If a woman has rubella while pregnant, what is the likely outcome for the baby?
low birth weight, cataracts, deafness, MR, heart defects, diabetes (mulberry muffin)
What cells are infected by HPV? B19?
HPV infects basal cells of skin, B19 infects erythroid progenitor cells
What virus causes herpetic whitlow? Population at risk?
HSV; dental hygenists who don’t understand the concept of a glove
Why do people with lepromatous leprosy have flat noses?
Mycobacterium leprae destroys the septum of the nose
What profession may be likely to get Orf infections?
Taxidermists
What 2 bugs may cause impetigo?
Staph and strep pyogenes
What is significant about Neisseria spp. Pili?
They undergo antigenic variation
How would you differentiate between erythrasma and tinea cruis?
erythrasma = corynebacterium minutissimum fluoresces coral red with Wood’s lamp, tinea cruis does not fluoresce
What are the 3 types of Bacillus anthracis infection?
Pulmonary (mediastinal widening), GI, and cutaneous which is the most common
How is smallpox transmitted? How does it spread throughout the body?
Respiratory droplets, spreads via lymphatics
What causes white piedra? Black piedra?
White piedra = trichosporon spp; black piedra = piedraia hortae
Which mycetoma granules are dark red to black?
M. mycetomatis
What kind of virus is smallpox?
small pox = enveloped dsDNA
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
Where is the most likely location of hyphae in a tinea infection?
Stratum corneum; these are dermatophytes
Name the 4 dermatologic viruses that have systemic spread and an infectious rash
HSV-1,2, VZV, Variola, and Coxsackievirus
Between chickenpox and smallpox, which has lesions that would more closely resemble molluscum?
smallpox because they are often umbilicated
Name the 3 dermatologic viruses that do not involve systemic spread
Molluscum contagiosum (can be a marker of HIV), HPV, and ORF
Name 2 derm viruses that may result in the formation of syncytia
Herpes and measles
What is the genetic makeup for HHV-6 and HHV-8?
ds DNA, enveloped
Where will you find a Cowdry Type A body? What does it tell you about the entirety of the herpesviridae family?
Intranuclear, HERPES VIRUSES REPLICATE IN THE NUCLEUS
Which bug creates a rash that looks a bit like the lupus rash?
Streptococcus pyogenes–erysipelas
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
How do ya differentate smallpox from chickenpox clinically?
synchronous lesions in smallpox, variable staged lesions in chickenpox
What are the bacterial agents to cause mycetoma (starred organisms)?
Actinomyces and Nocardia
What are the 2 major complications of measles?
Pneumonia and Subacute Sclerosing Panencephalitis
How do you get Sporothrix schencki? What area of the body is most commonly involved?
Usually from a thorn prick, often the hands
What is Hansen’s disease?
Leprosy
What is the difference between dermatophytoses and dermatomycoses?
Dermatophytoses are superficial cutaneous infections that only invade superficial layers; Dermatomycoses are similar but they go deeper than just the epidermis
What disease may occur with Malassezia furfur in the presence of a catheter?
Catheter Associated Sepsis
Please describe the evolution of the measles illness
Starts with a cold/flu like Sx 9-10 d after infection, in this they will have the classic cough, conjunctivitis, coryza, and PHOTOPHOBIA? Then they will get the rash behind ears and down (with koplick spots in mouth) 3 days later and it will progress to the feet by 6 d
How do you get a chromoblastomycosis?
generally in tropical and subtropical areas on FEET exposed to infected soil? Agricultural workers and mine workers
What is the name given to pigmented fungal cells in the pustules of a chromoblastomycosis?
Medlar body
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 bug and virulence factor causes toxic shock syndrome?
Staphylococcus aureus; TSST-1
How often does Clostridium perfringens divide?
every 12 minutes! Very rapid progression!
Why does Pseudomonas cause hot tub folliculitis?
The heat opens up the pores and lets the bug in
How does Dr. Kell pronouce “rash”?
Raysh
Why is tinea versicolor a misnomer for pityriasis versicolor?
Tinea describes ringworm type infections, Malassezia furfur is NOT a ringworm
Define macule
flat and circular lesion 5 mm or less in diameter
What derm lesion is pathognomonic for Pseudomonas aeruginosa?
Ecthyma gangrenosum
Genetic makeup of A) Measles B) rubella and C) B19
A) enveloped ssRNA B) enveloped ssRNA C) naked ss DNA
Which strains of HPV are responsible for warts on fingers and knees?
2, 3, 10
What does it mean for a fungus to be dematiaceous?
The hyphae and/or spores are darkly pigmented because they contain melanin granules
Name the 4 superficial fungi (not the dermatophytes)?
Malassezia furfur (pityriasis versicolor); Horatea werneckii (tinea nigra); Trichosporon spp. (white piedra); Piedraia hortae (black piedra)
What bug looks like a tennis racket on light microscope? What should you think if you see tennis rackets on EM?
Clostridium perfringens; Birbeck granules of Langerhans Histiocytosis
T/F: both Piedraia hortae and Hortae werneckii are dematiaceous fungi?
True these are black piedra and tinea nigra, respectively
Which gene allows for MRSA to be resistant to methicillin?
mecA (also resistant to nafcillin, dicloxacillin, and oxacillin)
What exactly is entering the skin in a cutaneous anthrax infection?
endospores, not gram positive rods
What is the major opportunist of the normal skin flora?
Staph epidermidis on prosthetic devices esp. > 3 months
Genetic makeup of A) B19 B) HHV-6
A) naked ssDNA B) enveloped ds DNA
What is the main virulence factor of s. epidermidis?
biofilm
What are the names for the asexual and sexual forms of pityriasis versicolor?
Asexual = Malassezia furfur; Sexual = Pityrosporum orbiculare
When a person has a mycetoma, which two organisms are most likely to cause a superinfection?
staph and strep (NF of the skin = most likely)
If you have a biopsy with syncytia (and it is a derm question) how can you differentiate between herpes and measles WITHOUT clinical Hx?
Look for a Cowdry Type A body in the newclaus
Define bulla
vesicle greater than 5 mm
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
Where does the name Propionibacterium acnes come from?
The fact that they metabolize sebum into propionic acid
What does Malassezia furfur look like on Wood’s lamp? On KOH?
Wood’s lamp = fluoresce bright yellow; KOH = spaghetti and meatballs
What virus causes a blistering “rash” and is a picornavirus?
Coxsackie A and A16
Name the 3 major dermatophytes
Microsporum, trichophyton, and epidermophyton floccosum
How would you differentiate between tinea cruis and candida for jock itch?
Candida affects both the scrotum and thigh; Tinea cruis only affects the thigh? Yes I’m sure never in the history of the world has tinea cruis ventured to the scrotum
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 is the most common dermatophyte fungus?
Trichophyton rubrum
What is the difference in appearance between endothrix lesions and ectothrix lesions?
Endothrix = fungi inside hair shaft, hair breaks and does not leave black dots; Ectothrix = fungi outside of hair, hair breaks and leaves little black dots
How is HPV transmitted?
direct contact and fomites
Name the 4 dermatologic viruses that have systemic spread and a non-infectious rash
HHV-6, HHV-8, measles, and rubellla
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 are some ways (4) that the hyphal form of Malassezia furfur can be induced?
Increased temperature, high humidity, greasy skin (teens), hyperhidrosis
What kind of virus are the Coxsackie viruses?
naked ss RNA picornaviruses
In what sense is the rash of B19 similar to that in lupus?
It is on the face and is sensitive to sunlight
Name the classic 5 childhood exanthems
rubella (german measles), rubeola (normal measles), roseola (HHV-6), chickenpox (VZV), and 5th disease or Parvovirus B19
What antigen is missing from LOS in comparison to LPS?
the O antigen
How do you get a mycetoma? What kind of inflammation?
Traumatic inoculation; granulomatous (subset of chronic)
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
How is the location of white piedra different from that of black piedra?
White piedra is facial, axillary, and pubic hair whereas black piedra is only on the face and scalp
What are 2 important areas to look for the rash of secondary syphilis?
palms of hands and soles of feet
What kind of capsule does B. anthracis have?
Poly D-glutamic acid
Which strains of HPV are responsible for plantar warts?
1 and 4, flat and grow inward
Which of the childhood exanthems will have a multinucleate giant cell under microscopy?
measles
Herpes is a derm virus with giant cells. But, thankfully, not a childhood exanthem.
How can you treat necrotizing fasciitis? (3)
Surgical debridement and/or amputation; combination antibiotics; hyperbaric chamber
Severe complications of viral infection of eczematous skin occur with ________
HERPES!
Causal agent of the infamous fish tank granuloma
Mycobacterium marinum
How can you differentiate (lab-wise) N. gonorrhea and N. meningitidis?
Meningitidis metabolizes maltose as well as glucose only whereas gonorrhea metabolizes glucose only (carty misspoke)
Compare and contrast the incubation period of measles and german measles
German measles is 2-3 weeks, measles is only 9 days
What is the key feature of ALL herpes viruses?
latency! i.e. nerve ganglia for HSV and VZV, B cells for EBV, etc? B/T cells for HHV-6
What is erythema infectiosum? Exanthem subitum?
B19, HHV-6
What is the vaccine type for measles?
MMR, live-attenuated
In general, what is the most important virulence factor for Strep pyogenes?
M protein, it evades phagocytosis
How do you grow Malassezia furfur? What is the likely significance of the fact that lesions occur in the distribution of sebaceous glands?
On solid media with olive oil since it requires long chain fatty acids to grow; sebum contains fatty acids!
What is the transmission of A) measles B) rubella and C) B19
ALL = RESP DROPLETS
How does a wart actually form in HPV infections?
when the virus infects basal cells (stratum basale) it stimulates cell division
How does cutaneous anthrax present?
PAINLESS black eschar
What family of virus is measles? German measles?
rubeola = paramyxoviridae, rubella = togaviridae
What is the most likely cause of tinea capitis in the U.S?
Trichophyton tonsurans
What kind of virus is measles? What family? What is the transmission? Incubation period?
enveloped ssRNA, paramyxoviridae, respiratory droplets, 9-10 d
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
What kind of virus is molluscum contagiosum?
enveloped DS DNA virus (complex shape)
What virus causes hand, foot, and mouth? What kinda, sorta, but not really all that similar disease is caused by fungus?
Coxsackie A16; two foot, one hand which is a tinea infection
What is the most important virulence factor of the tineas?
keratinases to get through the stratum corneum
Define patch
a macule (or group of macules that has coalesced) to become greater than 5 mm in diameter
What kind of virus is orf and how is it transmitted?
enveloped DS DNA virus; sheep, goats, and reindeer
How is smallpox transmitted? Chickenpox?
RESPIRATORY DROPLETS
What 3 bugs should be on the differential for “jock itch”?
Erythrasma = Corynebacterium minutissimum; Tinea cruis, and candida
Which mycetoma granules are white?
Pseudallescheria boydii
How does one get Erysipelothrix rhusiopathiae? G stain?
GI tract of animals–causes erysipeloid; gram positive rods
Which causal agent of a mycetoma may disseminate in HIV or IC pts?
P. boydii (white granules)
What is the danger of tinea pedis? Why does the normal flora change?
Secondary infection from itching and–the normal flora changes because there are antibiotics produced by the fungus, this may also impact the secondary infection risk
Describe how HPV infects
it is a naked dsDNA virus that infects the basal layers of skin but replicates in the mature layers
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 the goal of the human microbiome project?
To determine ALL of the normal flora of the human body
What is the causal agent behind Tinea nigra?
Hortae werneckii
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
What is the most common mode of transmission for a systemic mycosis?
respiratory (i.e. coccidiodes etc.)
What causes erysipelas? Erysipeloid?
Erysipelas = Strep pyogenes; Erysipeloid = Erysipelothrix rhusiopathiae
Which mycetoma granules are black?
M. grisea and E. jeanselmei
