Atypical Mycobacterial Infections Flashcards
Slow growing mycobacteria - MUKAHISST
M. Marinum M. Ulcerans M. Kansasii M. Avium M. Haemophilum M. Intracellulare M. Szulgai M. Scrofulaceum M. Tuberculosis
Fast-growing mycobacteria
M. Abscessus M. Chelonae M. Fortuitum M. Mageritense M. Wolinskyi M. Smegmatis M. Mucogenicum
M. Marinum
@
Swimming pool granuloma
Fish tank granuloma
Cultured at 30-33 degree celcius
Growth inhibition at 37 degree celcius
Slow growing mycobacteria
Pathogenic on abraded skin (though hx of trauma cannot always be elicited)
Survives readily in water
Can be cultured from
- Dead fish
- Sides of tanks
- Sand samples
- Water samples
Causes disease in many fish species Fresh or saltwater - Esp enclosures of water that are not often replenished i.e. swimming pools, aquariums - Heated water in temperate climates - Seawater - Natural pools and rivers - Beaches - Tropical fish tanks i.e. Siamese fighting fish, snakehead —> most infections from cleaning out fish tanks - Fish farms
Human infection follows contact with fishes/contaminated water
CLINICAL FEATURES
Hx of trauma and water/fish related hobbies or occupations
Incubation period 2-3 weeks following inoculation onto abraded skin
Initial Solitary Nodule or pustule
May break down into an ulcer or abscess vs remain as verrucous plaque
Subsequent multiple lesions
Sporotrichoid spread (nodules extend along line of lymphatic vessels) Regional lymph glands may be enlarged
Fish fanciers —> dominant hand and fingers
Swimmers —> elbows, knees, feet
DDX Leishmaniasis Sporotrichosis Other atypical mycobacterial infection - M kansasii (slow grower) - M chelonae (fast grower) - M gordonae
PREDISPOSING FACTORS —> fish related activities Keeping and rearing tropical fish Fishworkers Fishmongers Cooks
COMPLICATIONS Deeper infection (from direct extension of the skin infection) —> tenosynovitis, osteomyelitis, bursitis, septic arthritis Disseminated lesions (immunocompromised patients)
IX
Skin biopsy for
- histopathology
- MCS at 30-33 degree celcius, observed for 6 weeks (usually positive by 2-4 weeks) —> susceptibility testing in treatment failure
- Monoclonal antibody against M marinum antigens
- PCR
HISTO
Early lesions -
Non-specific inflammation
Older lesions - Ulceration Pseudoepitheliomatous hyperplasia Well-formed tuberculoid granulomas with fibrinoid masses \+/- Langhans giant cells Intracellular AFB in 10% of cases
GENERAL MX
Use gloves
Cover cuts and grazes
Maximum chlorination of swimming pools
SYSTEMICS —> drugs to be continued for 1-2 months after resolution of symptoms Iusually total course 3-4 months)
Clarithromycin*** (drug of choice, lack of significant side effects)
Clarithromycin + ethambutol
Clarithromycin + ethambutol + rifampicin (in cases of osteomyelitis or deep infection)
Azithromycin (alternative to clarithromycin)
Amikacin (refractory disseminated cases)
OTHER SYSTEMICS Sulphonamides Bactrim Rifampicin Rifabutin and ethambutol Doxycyline Minocycline Streptomycin
SURGICAL
Debridement for deeper infection (controversial)
PHYSICAL RX
PDT
REASONS FOR RX FAILURE
Involvement of deeper structures
Delay in Dx
Inappropriately administered ILCS
COMPLICATIONS
Deep infection of the hand can be aggressive —> permanent disability —> consult ID, hand surgery specialist
M. Kansasii
Mainly lung pathogen
Slow growing mycobacteria
M. Ulcerans
@ Buruli ulcer (Uganda) Bairnsdale ulcer (Aus) Searls ulcer (Aus)
Slow growing mycobacteria
Culture at 32 degree celcius
Rural tropical wetlands
Esp areas with stagnant water i.e. ponds, swamps
Acquired from aquatic niches
Very rarely person-person transmission
Hosts -
- Possums
- Koalas
Local minor often unnoticed skin trauma that permits the inoculation
Latent period 4 months
Infects Skin and subcut tissues
—> septal panniculitis —> necrotic, calcify
—> leukocytoclastic vasculitis
Notifiable disease
RISK FACTORS
Visit/residence in endemic area
Failure to wear protective clothing
Exposure to unprotected natural water resources
Inadequate care of minor skin wounds
HIV seropositivity —> increase risk or assoc with aggressive disease
CLINICAL FEATURES
Usually children
Usually arm or leg (but can be trunk or head)
Painless (painful if secondarily infected)
Nodule, papule, plaque, oedema —> large indolent painless shallow necrotic ulcer with undermined edges
Extends rapidly and irregularly
May be surrounded by induration
Usually single ulcer, satellites may develop
Floor of ulcer = necrotic fat, clear mucoid discharge
No constitutional symptoms i.e. fever, LN
Disseminated disease in context of HIV
DDX EARLY LESIONS (nodules, papule)
FB granulomas
Epidermoid cyst
Adnexal tumours
DDX ulcers Ulcerated TB Blastomycosis (or other deep fungal infection) Cellulitis PG necrotising fasciitis
IX —> sample at least 2 sites per lesion for increased sensitivity
Skin bx for Tissue culture at 32 degree celsius
Skin bx for Histopathology
Swab/FNA/skin bx for PCR (highest sensitivity, results within 48hrs)
Swab/FNA for Direct smear with AFB stains i.e. ZN stain (if PCR not available)
SYSTEMICS for total 8 weeks
First line -
Oral Rifampicin 10mg/kg + IM streptomycin 15mg/kg daily for 8 weeks under direct supervision***
Second line -
Oral Rifampicin 10mg/kg + IM or IV amikacin15mg/kg daily for 8 weeks under direct supervision
Third line -
Oral Rifampicin 10mg/kg + Oral clarithromycin for 8 weeks
Oral Rifapentine + oral moxifloxacin for 8 weeks
Small Lesions < 5cm
ABs only for 8 weeks
Moderate Lesions 5-15cm
ABs for 4 weeks, surgery, ABs another 4 weeks (total 8 weeks)
Advanced Lesions > 15cm
ABs for at least 1 week, surgery, ABs (total 8 weeks)
COMPLICATIONS
Immune reconstitution inflammatory syndrome (paradoxical reaction occuring during treatment) —> deterioration after initial improvement —> avoid Rx change, persist with Rx
Bone involvement subjacent to skin lesions
Metastatic osteomyelitis from lymphohaematogenous spread
Fibrosis, calcification in the healing process —> contractures, severe deformity
COURSE/PROGNOSIS
Variable
Usually prolonged
PROPHYLAXIS BCG vaccination (short term protection, may protect against osteomyelitis)
