Subcutaneous Fungal Infection

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:
    • Mycetoma
    • Sporotrichosis
    • Chromoblastomycosis
    • Phaeohyphomycosis
    • Lobomycosis
    • Rhinosporidiosis (now not a Fungus)

Sporotrichosis

  • 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

LAB DIAGNOSIS

  • 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

ASTEROID BODY

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

  • 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
    1. tumefaction of affected tissue,
    2. Formation of multiple draining sinuses
    3. presence of oozing granules.
  • On the basis of nature of infection there are 2 categories of disease :-
    • Eumycetoma
    • Actinomycetoma

EPIDEMILOGY

  • 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

PATHOGENESIS

  • 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

CLINICAL FEATURES

  • 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

LAB DIAGNOSIS

  • The diagnosis of eumycetoma is confirmed by the demonstration of grains in lesions and their identification.
  • SPECIMEN COLLECTION:
    • Grains or granules
    • Pus and exudates
    • Biopsy material
  • Methods used are:
    • direct microscopy
    • culture
    • serology
    • histopathology

SERODIAGNOSIS

  • Techniques used are Immunodiffusion CIE

Histopathology :

  • 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

GRAINS

  • 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

TREATMENT

  • 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

CHROMOBLASTMYCOSIS

  • Chromoblastomycosis is a slowly progressing localized fungal infection of skin & subcutaneous tissue mostly involving exposed parts of body

CLINICAL FEATURES

  • Lowerlegs are most frequently involved.
  • Haematogenous and lymphatic dissemination may occur.
  • Lesions are warty cutaneous nodules, like cauliflower

LAB DIAGNOSIS

  • SPECIMEN : SKIN SCRAPINGS (black dots) or biopsy specimen from dry crusty material recovered from surface of lesions.
  • Direct examination:
    • 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.

FUNGAL CULTURE

  • 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.

IMMUNODIAGNOSIS

  • Double immunodiffusion
  • IFA
  • ELISA
  • Serological tests usually not employed due to lack of infrastructure.

TREATMENT

  • CRYOTHERAPY
  • THERMOTHERAPY
  • LASER THERAPY
  • CHEMOTHERAPY

Phaeohyphomycosis

  • Phaeohyphomycosis is subcutaneous & systemic infection, caused by various heterogenous group of phaeoid (dematicious) fungi.

AGENTS OF PHAEOHYPHOMYCOSIS

  • Bipolaris
  • Curvularia
  • Exserohilum
  • Alternaria
  • Exophiala
  • Phialophora
  • Wangiella
  • Cladophialophora
  • Cladosporium
  • Haetomicem
  • Ochroconies

LAB DIAGNOSIS

  • 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.

HISTOPATHOLOGY

  • 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,
    • e.g:
      • Wangiella dermatitidis,
      • Exophiala jeanselei
      • Exophiala spinifera
      • Aurebasidium pullulens

RHINOSPORIDIOSIS

  • 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

  • Lobomycosis is a slowly progressive chronic, granulomatous fungal infection of the skin & subcutaneous tissue.
  • Causative organism is recently redesignated fungus – Lacazia loboi.

LABAROTARY DIAGNOSIS

  • Specimen:- skin curettage or, biopsy by surgical incision
  • DIRECT EXAMINATION:-
    • 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.

TREATMENT

  • 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
    • Cryotherapy
    • Electrodessication

INFECTIVE SYNDROME

  • PURULENT
  • N.meningitidis
  • S.pneumoniae
  • H.influenzae
  • E.coli
  • Listeria
  • Gr.B Streptococci
  • ASEPTIC
  • Enterovirus
  • Herpes virus
  • Adenovirus
  • Cryptococcus
  • Free living amoeba
  • Mumps
  • Measles

NEONATAL MENINGITIS

  • E.coli
  • Gr.B Streptococci
  • Listeria
  • H.influenza

UTI

  • E.coli
  • Proteus
  • Klebsiella
  • Pseudomonas
  • S.saprophyticus
  • Enterococcus
  • Candida

SORE THROAT

  • Gr.B Beta hemolytic Streptococci
  • Corynebacterium diptheriae
  • H.influenzae
  • B.pertussis
  • N.gonorrhoeae
  • Treponema vincenti
  • Candida albicans
  • Epstein Barr virus
  • Adenovirus
  • Coxsackievirus A

PNEUMONIA

  • Streptococcus pneumoniae
  • Mycoplasma
  • Legionella
  • Chlamydia pneumoniae
  • Influenza, Parainfluenza virus
  • Respiratory syncitial virus

HOSPITAL ACQUIRED PNEUMONIA

  • Pseudomonas
  • E.coli
  • Klebsiella
  • Legionella
  • Immunocompromised persons
  • Pneumocystis carinii

GIT INFECTIONS

  • V.cholerae
  • E.coli
  • Shigella
  • Salmonella
  • Yersinia enterocolitica
  • S.aureus
  • B.cereus
  • Cl.difficile
  • Rotavirus
  • Astrovirus

FOOD POISIONING

  • S.typhimurium
  • V.parahaemolyticus
  • C.jejuni
  • S.aureus
  • B.cereus
  • Cl.botulinum
  • Cl.perfringens

STD

  • TREPONEMA PALLIDUM
  • CHLAMYDIA TRACHOMATIS
  • H.DUCREYI
  • HSV
  • N.GONORRHOEAE
  • C.TRACHOMATIS
  • M.GENITALIS
  • TRICHOMONAS VAGINALIS
  • GAEDNERELLA VAGINALIS
  • HUMAN PAPILLOMA VIRUS
  • HIV

WOUND/PUS INFECTION

  • S.aureus
  • S.pyogenes
  • S.pneumoniae
  • E.coli
  • Proteus
  • Pseudomonas
  • Cl.perfringens
  • Klebsiella
  • Citrobacter
  • Enterobacter

PUO

  • UTI
  • RTI
  • SEPTICEMIA
  • ENTERIC FEVER
  • BRUCELLOSIS
  • RELAPSING FEVER
  • RHEUMATIC FEVER
  • LEPTOSPIROSIS
  • TYPHUS FEVER
  • MALARIA

Other Microbiology Notes :-

Dracunculus Medinensis

Ancylostoma duodenale (Hook worm)

Schistosoma: Blood Flukes (Bilharzia)

. Stool Examination

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