Infections - Mycobacterial Flashcards
What are the slow growing mycobacteria
KMATS M. Kansasi M. Marinum M. Avium M. TB M. Scrofulaceum
M. Leprae is a very small slightly curved rod
True
Which are fast growing mycobacteria
FACD M. Fortuitum M. Abscessus M. Chelonae M. GooDii
A minority of exposed individuals do not develop leprosy
False majority
WHO Classificatoin of Leprosy
1 - paucibacillary, single lesion Leprosy
2 - paucibacillary, 2-5 skin lesions
3 - multibacillary
Not as commonly used as the LL/BL/BB/BT/TT/I classification
What are clinical features of lepromatous leprosy
LEPROSY Leonine facies Eyes - lagophthalmos, eyebrows (madarosis) Peripheral and sensory neuropathy (foot drop) - in BT/TT Resorption of bone (shortened digits) Orchitis and sterility Saddle nose Y (Gynaecomastia, IchthYosis)
Form with least cellular immunity and greatest number of bacilli
- multiple poorly defined erythematous macules, papules, nodules and plaques
- lesions are widespread and USUALLY symmetric
Most common sites are the face, buttock and lower extremities
Infiltration of the skin of forehead can lead to leonine facies
- additional signs and late sequelae:
—> madarosis of eyebrows
—> saddle nose
—> enlarged earlobes
—> acquired ichthyosis on Lower extremities
Anaesthesia in glove and stocking distribution
Lagophthalmos
Histoid leprosy is characterised by the development of dermatofibroma-like papules and nodules
True
Clinical features of borderline leprosy
Features intermediate between two ends of spectrum - cutaneous lesions are usually symmetric
- may have unilateral earlobe swelling
- severity of cutaneous and pierhpheral nervous system abrnoalities depend on whether pt “leans” towards BT or BL pole
- within cutaneous plaques, hairs are usually ABSENT
Clinical features of Tuberculoid leprosy
Borders of skin lesions are slightly elevated -this is the preferred site for histologic exam
- seen only a few well demarcated plaques and sometimes only NEURAL involvement
- in some patients, they are hypopigmented plaques
- typically partial bu not complete pigment loss
- plaques need to be examined for alopecia as well as anesthesia or hypostheisa
- unilateral neuropathic changes eg. Digital resorption may be seen
Leprosy reactions - type 1
Reversal reaction with “upgrading”
- enhancement of cell mediated immunity with a Th1 cytokine pattern
- delayed type hypersensitivity reaction
Occurs with BT, BB or BL or tuberculoid leprosy with immunologic recovery during or after tx
- PINE (lone pine type 1)
—> P: acute nerve pain or tenderness (neuritis) and loss of function
—> I: incr inflammation in established skin lesions
—> N: neurological impairment in absence of painful nerves
—> E: emergence of new lesions of the skin
—>
—>
—>
Leprosy reaction type 2 - excessive humoral immunity with a Th2 cytokine pattern and formation of immune complexes, may be accompanied by increased cell mediated immunity
True
Features of type 2 leprosy reaction
erythema nodosum leprosum most common FLOSHING - fever - lymphadenitis - orchitis - severe joints welling and pain - hepatosplenomegaly - iridocyclitis - nodular skin lesions - glomerulonephritis
What is Lucio phenomenon
Reactional state characterised by thrombotic phenomena in addition to necrotising cutaneous small vessel vasculitis
Grenz zone on histo
True
Virchow cells and granulomas can be seen in indeterminate form
False
What are Virchow cells
Macrophages with numerous bacilli as well as lipid droplets in their cytoplasm
WITH NERVE INVOLVEMENT, CUTANEOUS NERVES SHOW LAMINATION OF THE PERINEURIUM, CAUSING AN ONION SKIN APPEARANCE
TRUE
WHAT STAINs can be used to help diagnose leprosy
Gram stain Ziehl-Nielsen Wade-Fite Methanamine silver is good for detecting fragmented AFB Sudan III and Sudan IV
How to perform a slit skin smear
Samples can be obtained from earlobes, chin, extensors forearms, dorsal fingers , buttocks and trunk
- fold of skin is firmly squeezed between thumb and forefinger of examiner with forceps
Small incision made with a scalpel bald
Liquid nitrogen is smeared onto a slide + allowed to dry
Smear is usually stained by the FITE or Z-N method and search made for red rods at 100 x with oil immersion
Organisms can be found in 100% of those with lepromatous leprosy, 75% of those with borderline leprosy and 5% of those with suspected tuberculoid leprosy
What are the 3 classic skin tests with leprosy (now infrequently used)
- histamine - 0.001% histamine placed on suspect patch and another on normal skin as control. Both sites are pricked with needle then extent of wheal and flare is recorded.
- pilocarpine - tincture of iodine applied to suspected lesion and normal skin prior to injection of pilocarpine
—> areas then dusted with starch will turn blue ., if normal sweating, as sweating is decreased in lesions of leprosy since relies on parasympathetic nerve fibres - Lepromin test intradermal injection of 0.1mL suspension of heat killed. M. Leprae
Treatment of paucibacillary leprosy
Daily Dapsone 100mg
Monthly rifampin 600mg
For 6 months
Treatment of multibacillary leprosy
Monthly Rifampicin 600mg and clindamycin 300mg + daily clofazimine 50mg and dapsone 100mg, for 12 months
TB subtypes
TB chancre TB verrucosa cutis Scrofuloderma Orificial TB Lupus vulgaris Miliary TB TB gumma Papulonecrotic tuberculid Lichen scrofulosorum Erythema induratum
M. Ulcerans is caused by a slow growing mycobacteria
True
Mycobacterium is thought to be harboured by snails, water insects, fish and aquatic plants
True
Organisms are found at edge but not base of ulcers of M.ulcerans
False within base and surrounding necrotic tissue
M. Ulcerans are very painful
False . Painless due to mechanism of inhibiting pain receptors by binding to angiotensin II type 2 receptors on neurons
M ulcerans lesions do not tend to spontaneously resolves
False can resolve over 6-9 mo
BCG vaccine provides no immunity towards M ulcerans
False - emerging evidence it may protect against Buruli ulcers and osteomyelitis in the short term
M ulcerans patients are usually unwell
False usually well
Clarithromycin is first line for m. Marinum
True
Sporotrichoid spread in which mycobacteria?
FKMS Fortuitum Kansasi Marinum Scrofulaceum
