Introduction to Subcutaneous Fungal Infection
- Subcutaneous fungal infection primarily involve the dermis, subcutaneous tissue and adjacent bone.
- The disease process usually starts following a trivial trauma which is the sole source of infection.
- Major subcutaneous Mycoses are:
- Rhinosporidiosis (now not a Fungus)
- A chronic , pyogranulomatous fungal infection of cutaneous and subcutaneous tissues which remain localized or may show lymphatic spread and occasionally may disseminate to other parts of body.
- Lesions in exposed part of skin due to minor trauma
- Occurs due to inoculation of skin by Sporothrix schenkii- a thermally dimorphic fungus
- Direct examination: Specimen – pus exudate aspirate from nodules or curettage from open lesions
- KOH wet mount: small elongated yeast cells may be seen.
- Gram’s stain: Gram positive irregularly stained yeast cells , very few in number may be seen.
- Histopatology: with H&E and PAS stain
LAB DIAGNOSIS (FUNGAL CULTURE)
- Fungal culture is the gold standard for establishing definitive diagnosis of sporotrichosis.
- Media used are SDA, BHIA with actidione, blood agar, choclate agar
- Incubated at both 25⁰C and 37⁰C .
BUDDING CIGAR SHAPED YEAST CELLS
BUDDING CIGAR SHAPED YEAST CELLS
FLOWER LIKE PATTERN OF SPORES
SPOROTHRIX SCHENCKII CONIDIA
TREATMENT AND PROPHYLAXIS
- Oral Ketoconazole(10 mg/Kg /day) or itraconazole (100-200 mg/day).
- Terbinafine (250 mg twice daily)
- Amphotericin B – for severe dissminated infection in AIDS patient, CNS and pulmonary disease.
SPOROTRICHOSIS, V P CHEST INSTITUTE.
- Mycetoma is a slowly progressive ,chronic granulomatous infection of skin and subcutaneous tissues with involvement of underlying fasciae and bones usually affecting extremities , caused by fungi or higher bacteria – Actinomycetes.
- The disease is characterized by triad of
- tumefaction of affected tissue,
- Formation of multiple draining sinuses
- presence of oozing granules.
- On the basis of nature of infection there are 2 categories of disease :-
- In india Tamilnadu, south india Rajasthan, and dry western parts of india are more common.
- More prevalent in developing countries and in rural areas.
- M:F =3.5:1
- Introduction of causative agent probably by accidental minor trauma -> subcutaneous fungal infection characterized by formation of large no. of aggregates k/a grains -> dense infiltration of PMN and other leucocytes accumulate around these st. to form a microabcess
- Incubation period is unknown.
- appearance of a hard subcutaneous painless nodule(earliest sign). -> As the lesion enlarges sinuses appear on skin surface as papules or pustules that discharge their contents and then dry up leving a small scar. -> whole area becomes hard ,swollen and the limb becomes greatly deformed. -> In advanced cases pain and sweating may be seen.
EXCISED MYCETOMA WITH A DRAINING SINUS
- The diagnosis of eumycetoma is confirmed by the demonstration of grains in lesions and their identification.
- Grains or granules
- Pus and exudates
- Biopsy material
Methods used are:
- direct microscopy
- Techniques used are Immunodiffusion CIE
- It can be performed either on grains extracted from lesions and fixed immidiately in formalin or on biopsy material.
- Recognition is based on appearance of grains using H/E stain, PAS stain
- The colour and consistency of the grains vary with different agents causing the diseases
- In Actinomycotic mycetoma the grains are soft,having thin filaments
- In mycotic lesions ,are harder, broader with septae and Chlamydospores
- Eumycetoma – oral ketoconazole 200 mg twice daily and itraconazole 100 mg twice daily for 3 monthes to 18 months.
- Respond poorly, requiring surgical debridement and amputation in extreme cases.
- Actinomycetoma – Ab like sulfonamides, teracyclines ,Clav, Amikacin
- Chromoblastomycosis is a slowly progressing localized fungal infection of skin & subcutaneous tissue mostly involving exposed parts of body
- Lowerlegs are most frequently involved.
- Haematogenous and lymphatic dissemination may occur.
- Lesions are warty cutaneous nodules, like cauliflower
- SPECIMEN : SKIN SCRAPINGS (black dots) or biopsy specimen from dry crusty material recovered from surface of lesions.
- KOH WET MOUNT: Shows characteristic sclerotic bodies.dark brown yeast like cells with septa
- Biopsy: H/E ,Giemsa stain and Fontana Masson stain also show characteristic muriform cells.
- Identification of causal fungal agent is made by culture isolation and by studying colony morphology and microscopic appearance of sporulation pattern .
- Media used is SDA with actidione and.other Ab
- Colonies are floccose,grey to dark brown in color with black reverse.
- Final identification is by slide culture.
- Double immunodiffusion
- Serological tests usually not employed due to lack of infrastructure.
- LASER THERAPY
- Phaeohyphomycosis is subcutaneous & systemic infection, caused by various heterogenous group of phaeoid (dematicious) fungi.
AGENTS OF PHAEOHYPHOMYCOSIS
- CT/MRI – for cerebral & paranasal
- Direct examination :-
- Specimen – aspirates from abscesses, curettage from plaques, nodules, drained abscesses
KOH wet mount :-
- Fungi are usually pigmented & dark brown in colour .
- Yeast like cells/hyphae or, both may be seen.
- Yeast like cells singly or, in short chains & occasionally as spherical elements that may resemble chlamydospores.
- Hyphae are 3-4μm in Diameter short or, elongated irregularly swollen septate, branched or, unbranched.
- Masson – Fontana staining may be required.
- Geimsa stain, PAS stain, Masson – Fontana stain is used – show septate hyphae AND conidia in chains.
FUNGAL CULTURE :-
- Media – SDA with Cyclohexamide
- Incubated at 25o C & 37o C for 4 weeks.
- Grow very slowly but growth is visible by 1-2 weeks.
- Some of these grow as black yeasts but subsequently become mycelial during course of incubation,
- Wangiella dermatitidis,
- Exophiala jeanselei
- Exophiala spinifera
- Aurebasidium pullulens
- Rhinosporidiosis is a chronic granulomatous disease of mucous membrane of man and animals characterized by febrile polyps of nasal cavity, conjunctiva and other body sites.
- The disease is caused by Rhinosporidium seeberi which had been a taxonomically controversial endosporulating protist.
- It is a localised infection
- Diag: lesions having fungal spherules embedded in stroma of connective tissue and capillaries
- Spherules contains many endospores
- Treatment : excision of the polyp
- Lobomycosis is a slowly progressive chronic, granulomatous fungal infection of the skin & subcutaneous tissue.
- Causative organism is recently redesignated fungus – Lacazia loboi.
- Specimen:- skin curettage or, biopsy by surgical incision
- KOH & CFW stained wet mount :- yeast cells of L.lobi are globose to elliptical or, lemon shaped, doubly refractile , thick walled & multinucleate fairly uniform in size ranging from 6-12 μm.
- There may be chains of 20 or, more yeast of hourglass like yeast cells with a large connecting isthmus.
GROCOTS METHANAMINE SILVER STAIN OF L.LOBOI
Fungal culture :-
- Animal inoculation on Armadilo (Euphractus sexcentus)
- Foot pads of mice also used.
- Does not resolve spontaneously nor it has effective medical treatment.
- Antifungal drugs – 5 Flurocytosine, Itraconazole, Amphotericin B
- Antileprotic :- Clofazimine, 300 mg/day has shown good results.
- Clofazimine + Itraconazole has also been claimed to be succesful.
- Surgery –
- Surgical excision
- Gr.B Streptococci
- Herpes virus
- Free living amoeba
- Gr.B Streptococci
- Gr.B Beta hemolytic Streptococci
- Corynebacterium diptheriae
- Treponema vincenti
- Candida albicans
- Epstein Barr virus
- Coxsackievirus A
- Streptococcus pneumoniae
- Chlamydia pneumoniae
- Influenza, Parainfluenza virus
- Respiratory syncitial virus
HOSPITAL ACQUIRED PNEUMONIA
- Immunocompromised persons
- Pneumocystis carinii
- Yersinia enterocolitica
- TREPONEMA PALLIDUM
- CHLAMYDIA TRACHOMATIS
- TRICHOMONAS VAGINALIS
- GAEDNERELLA VAGINALIS
- HUMAN PAPILLOMA VIRUS
- ENTERIC FEVER
- RELAPSING FEVER
- RHEUMATIC FEVER
- TYPHUS FEVER
Other Microbiology Notes :-
All books/videos/software featured here are free and NOT HOSTED ON OUR WEBSITE. If you feel that your copyrights have been violated, then please contact us immediately.
Contact us: firstname.lastname@example.org