Dermatology lab Flashcards
pain when opening mouth suggests what?
otitis media
What are the two parts of the tympanic membrane
upper=pars flaccida and has blood vessels
lower: pars tensa: manubrium of malleus is visible, points rostrally
What should the abnormal ear canal be assessed for?
- erythema
- discharge
- degree of stenosis
- proliferation/hyperplasia of ear canal lining 5. ulceration
what are two ways that cytology can be collected?
direct and wet mount
What are three direct technique methods?
- impressions
- swabs
- scraping with scalpel blade
What are the advantages of the direct techniques?
- smear is easier to read
- thinner preparation so don’t need to focus up and down as much
- organisms stain more deeply
- easier to identify and quantitate bacteria on direct techniques
- inflammatory cells and other cells such as acantholytic cells can be IDed more easily
- makes nice preparations with moist soft exudative lesions
what are disadvantages of
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what are disadvantages of direct techniques?
- picks up much less material than tape smear from non-exudative skin lesions
- may not obtain adequate samples from dry or minimally greasy skin
- staining takes longer than with the tape preparations (3 diff quick steps + dry)
What are the advantages of the tape technique?
- much better at picking up material on minimally exudative or dry skin
- much faster staining and no air-drying
- well tolerated by pets in areas such as interdigital spaces
- great for looking for malassezia
What are disadvantages of the tape technique?
- very busy slide
- more difficult to examine bacteria “swimming” in the slide
- not good of IDing cellular inflammation, acantholytic cells etc
What is the impression smear best for?
moist, exudative lesions, pustules, crusts, very greasy skin, draining lesions
What is the impression smear not good for?
dry or minimally exudative lesions, small areas, ears
What is the swab good for
moist exudative lesions, small areas, ears
What is the tape best for?
greasy or dry skin, minimally abnormal skin, awkward areas, small areas, sensitive areas
What is tape not good for?
purulent lesions, pustules, wet skin
What does recent bathing do?
interfere with cytologic assessment
What should you assess on cytology?
presence of yeast, bacteria (characterize), cellular response
How do you differentiate bacteria and melanosomes on a cytology slide?
melaonsomes are brown/black, whie bacteria are blue/purple
What are skin scrapings primarily indicated for?
ectoparasite infestations
What are skin scrapings primarily indicated for?
ectoparasite infestations
What are deep skin scrapings required for?
to find demodex canis and demodex cati
what should be done before/while performing a deep scraping?
squeezing the skin
How is a deep skin scraping performed?
by using a #10 scalpel blade dipped in mineral oil and scraping in the direction of hair growth until slight dermal bleeding is observed.
How many sites should be sampled for demodex? Should they be pooled?
- 3
2. no do NOT pool. keep separate and record site of origin
What are superficial skin scrapings used for?
- sarcoptes
- notoedres
- cheyletiella
- demodex gatoi
- sometimes lice
IS it important to record site of origin for superficial skin scrapings?
no because even 1 mite is highly abnormal
How many scrapings should be done for sarcoptes? and where should they be done?
5-10 areas
- ear margins
- elbows
- hocks
- areas with excessive crust and scale
How do you look for otodectes or demodex mites in ear canals?
by performing a swab to collect exudate
why is it good to supplement skin scrapings with hair plucks when looking for demodex?
because hair plucks can retrieve demodex from areas that are difficult to scrape.
How likely are you to find sarcoptes on a skin scraping. What should you do if it fails?
- 20-30% of cases
2. treatment trial
What are two methods that help to find surface mites on cats?
- fecal floatations to find cheyletiella and others
2. make sure to take at least one scraping from dorsal neck
What can clear tape ectoparasite prep be used to find?
superficial parasites (it can sample larger areas)
- cheyletiella
- lice
- poultry mites
- fur mites
How can fleas be found/diagnosed?
- parting hair on caudal dorsum and turning pet over
- flea combs
- finding flea dirt
How do you differentiate flea feces from specks of soil?
if you rub flea feces on moistened tissue the flea dirt should dissolve into a bloody smear
How do you differentiate flea feces from specks of soil?
if you rub flea feces on moistened tissue the flea dirt should dissolve into a bloody smear
What can flea dirt harbor
bartonella henselae–causative agent of cat scratch fever so avoid contact with broken skin
how do you find lice and nits?
lice can usually be found with naked eye and removed by clear tape or flea combs.
nits can usually be removed with a hair pluck
What are 6 reasons to perform a trichogram?
- find demodex
- find nits (lice ova) or occasionally cheyletiella ova
- diagnose colour dilution alopecia or other structural abnormalities of hair
- look for evidence of self-inflicted alopecia
- to look for dermatophytes infected hair (not sensitive or specific)
- to determine ratio of hairs in telogen or anagen
A hair sample from an alopecia pet containing mostly telogen hairs suggets what?
endocrinopathy
What is the purpose of wood’s lamp?
quick way to detect dermatophyte infected hairs. must see the fluorescence along the hairs, NOT on the skin and remember drugs, soaps and bacteria may show fluorescence (not on hair shaft) and give false positive
When is dermatophyte fungal culture indicated?
when there is possible dermatophytosis and to ID the fungus
What are two ways to collect samples
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What are two ways to collect samples for dermatophyte fungal culture?
1, take hairs and scales from edge of lesion (or that fluoresced under wood lamp)
2. mackenzie toothbrush technique
How do you differentiate dermatophytes and nondermatophytes on DTM (dermatophyte test medium)
- the colour indicators turns from yellow to red when proteins in the medium are used and since dermtophytes preferentially use proteins the colony growth is preceded by focal colour change of the medium
What is hte colour of dermatophyte colonies?
white, cream, tan
What is the colour of contaminant fungal colonies
grey or green
What are the two types of media the fungus is grown on?
sabouraud
How are fungal colonies examined under microscope?
use clear tape to pick up material and place tape on drop of lactophenol cotton blue stain
How are fungal colonies examined under microscope?
use clear tape to pick up material and place tape on drop of lactophenol cotton blue stain
What should you do when biopsying alopecic areas?
draw a line parallel to the direction of hair growth
Where should you biopsy depigmentation
biopsy depigmentating areas (gray) rather than depigmented areas
Is there surgical preparation of a biopsy site?
no
how do you anesthetize for biopsy?
inject subQ and fan beneath the lesion. make sure deep enough so doesn’t disrut dermis. mix sodium bicarb (1:10) to make sting less. keep in mind the toxic dose
How do you perform a punch biopsy?
- 6mm usually
- rotate in one direction until feel decreased resistance
- use thumb forceps to remove biopsy and cut using scissors
- grasp the subQ tissue
- suture
How do you perform a punch biopsy?
- 6mm usually
- rotate in one direction until feel decreased resistance
- use thumb forceps to remove biopsy and cut using scissors
- grasp the subQ tissue
- suture
When is culture indicated?
- recurrent pyoderma
- severe or deep pyoderma
- therapy has failed to resolve pyoderma
- zoonotic transmission suspected
- numerous rod-shaped bacteria on cytology from skin or ears (less predictable response to antibiotics)
which is more appropriate for culture, ulcers/erosive lesins or intact pustules?
intake pustules–can open with sterile needle and swab
how can you sample from collarettes
by undermining edge with culture swab
