Opportunistic mycosis are infections due to fungi of low
virulence in patients who are immunologically compromised. They are infections
that takes advantages of the weakened immune defence an attack, the phrase opportunistic
infection is otherwise shortened to “01”.
Opportunistic mycosis are caused by fungi particularly
opportunistic fungi, i.e those that takes advantage of certain situations such
as bacteria, protozoan, or other fungi infections that usually do not cause
disease in healthy host. A compromised immune system how ever, present on
opportunity for the pathogen to infect the host.
CAUSES OF
OPPORTUNISTIC MYCOSIS
Opportunistic mycosis are caused by immunodeficiencies
associated with the followings.
1. Malnutrition
2. Fatigue
3. Recurrent infection
4. Immuno suppressing agent
5. Advanced HIV infection
6. Genetic predisposition
7. Skin damage
8. Medical procedure
9. Pregnancy
10. Use of antibiotic
Fungi species that may become opportunistic include the followings
Ø
Aspergillus species
Ø
Candida albicans
Ø
Cryptococcus neoformans
Ø
Histoplasma capsulantum
Ø
Cryptosporidium
Ø
Ispora belli
Ø
Pityrosporum ovale
SUPERFICIAL CANDIDOSIS
Superficial Candidal infections involving the skin, nails and
mucous membrane are very common through out the world candidal albican accounts
fo80-90% of cases, but other species e.g C. tropicalis C. glabrata etc. may
occur. C. albicans are found in
small numbers in the commensal flora (mouth, gastrointestinal tract, vagina,
skin) of about 20% of the normal population. The carriage rate tends to
increase with age and is higher in the vagina during pregnancy. Immunity
depends on non-specific and immunological defenses. The non specific inhibitory
factors includes inhibitors in serum such as unsaturated transferring and
epithelial proliferation. Specific immunity depends on sensitized T Lymphocytes
and Phagocytes especially neutropils
(a) Pathogenesis
i.Mucosal
infection: This is the commonest form of superficial Candidosis. In oral Candidosis, white flecks appear on the buccal mucosa and the hard palate,
although these are adherent, they can be removed; the surrounding mucosa is red
and sore. Infection may spread to the tongue. This kind of infection occurs
most frequently in infancy and old age or in severely immunocompronised
patients, including those with AIDS.
ii.Vaginal Candidosis: itching, soreness and non-homogeneous white discharge accompany
typical white lesions on the epithelial surfaces of the vulva, vagina and
cervix. Vaginal candidosis is common, especially during pregnancy; most women
will have at least one episode during pregnancy; most women will have at least
one episode during their lifetime and some suffer recurrent attacks.
iii. Candida
infections of the skin almost invariably occur at moist sites such as the
axillae, groin, perineum, submammary folds and occasionally the toe clefts. In
infacts, Candida Spp. is often secondary invaders in napkin demiatitis.
Infection of the finger webs, nail folds and nails is associated with frequent
immersion of the hands in water and is an occupational disease e.g. among
housewives, nurses and barmaids. Superficial infections of the penis occasionally
occur after intercourse with females with vaginal thrush. Candida may also
infect the outer ear.
(b)Laboratory Diagnosis: Specimens
of skin and nail are collected in the same way as for suspected ringworm. For
infections that are transport to the laboratory especially for vaginal
discharge, Swabs should first be moistened in sterile or saline water before
use. In gram stained smears, the fungus is seen as budding gram positive yeast
cells; Candida sp. Grow well on sabouraud medium or on blood agar at 25-37Oc;
typical yeast colonies appear within 1-2days.
(c) Treatment and Prevention: Most superficial infections respond well
to topical therapy with an imidazole. In oral Candidosis, nystatin,
amphotericin B or miconazole may be effective in Izenge or gel form. Most cases
of vaginal Candidosis can be trated successful with a single application of a
topical imidazole or with oral fluconazole or itraconazole. Intermittent
prophylaxis with an oral azole or vaginal pessaries is of benefit in
controlling recurrent vaginal Candidosis.
Treatment of
occupational disease of the finger web and nails involves a combination of
anti-fungal therapy, nail care and avoidance of prolonged exposure to water by
use of protective gloves or drying of hands carefully after washing.
TINEA VERSICOLOR
Tinea versicolor is a
long term (chromic) fungal infection of the skin. It is caused by the fungus
pityroporum ovale a type of yeast is normally found on human skin. It only
causes problems under certain circumstances. The condition is only common in
adolescence and young adult male. It typically occurs in hot climate. The main
symptom is patches of discolored skin lesions with sharp boarder and fine
scales. The patches are often dark reddish tan in colour. The most common site
are the back, underarm, upper arm, chest and neck. Affected areas do not darken
in the sun. In African Americans there may be loss of skin color or an increase
in skin color. Other symptoms include increased sweating and heating.
DIAGNOSIS
Skin scrapping in
potassium hydroxide solution should show the yeast.
TREATMENT
Treatment consist of
applying anti fungal medicine to the skin like ketoconazole, miconazole and
clotrimazole, over the counter anti dandruff shampoo applied to the skin for
minutes each day may also help treat the skin.
PREVENTION
People with a history of
tinea versicolor should try to avoid excessive heat or sweating.
SYSTEMIC CANDIDOSIS OR CANDIDIASIS
Systemic candidiasis
is an iatrogenic and opportunistic infection encountered among certain groups
of hospital patients, who carry more yeasts in the mouth and gastro-intestinal
tract than the normal population. The causative organism is Candida albicans
and other species of candida who are normal flora of the skin, mucous membrane
and GIT. They colonize all humans during birth or shortly thereafter.
Candidiasis occurs world-wide and is the most common systemic mycosis. The
highest number of yeasts occurs:
(a) In patients
treated with antibiotics or steroids
(b)In immunocompromised patients
(c)After surgical procedures such as organ ‘transplants or heart
surgery.Several factors predispose to yeast overgrowth:
(d) Natural
receptive states(infancy, old age, pregnancy). In non-pregnant women, the
incidence of candidal vaginitis is between 10-17% but it doubles during
pregnancy.
(e)Changes in local bacteria flora (e.g.
secondary to antibiotics, oral contraceptives and hormones)
(f) Changes to epithelial surfaces (e.g. due to moisture, local
occlusion, trauma).
(g) T lymphocyte defects (primary or secondary disease e.g. AIDS or
immunosuppression)
(g) Neutropenia (primary or secondary to disease or immunosuppression)
(i) Endocrine disease (e.g. diabetes mellitus)
(j) Miscellaneous conditions (e.g. zinc or iron deficiency).
Clinical
Manifestation: infection may be localized e.g. in the urinary tract,
liver, heart valves (endocarditis), meninges or peritoneal cavity or may be
widely disseminated and associated with a septicaemia (candidaemtia)
Deep-seated Candidosis is difficult to diagnose and treat candidaemia is seen
in postoperative or immanosuppressed patients, contaminated intravenous
catheters. Common sites of involved in disseminated infections are rare. One
common sign of deep-seated candidosis is the presence of white lesions within
the eyes (candida endophthalmitis) candida endocarditis usually follows surgery
for valve replacement, but also occurs in drug addicts. Infections of the
kidney is blood-borne. Bladder infections are usually associated with the
presence of an indwelling urinary catheter, the infection often clears when the
underlying cause is corrected.
Laboratory diagnosis: appropriate samples are examined microscopically in KOH or after gram staining.
In tissue sections, the fungus is
seen best if with PAS or methenamine-silver. Candida sp. Grows readily in
sabouraud agar and blood cultures. The most widely used serological tests are
immunodiffusion and BLISA for detection of antibodies to somatic extracts of C.
albicans. PCR is now used to diagnose invasive candidosis.
Treatment: drug of
choice for most forms of systemic candidosis are; intravenous amphotericin B,
intravenous or oral fluconazole. Both drugs can be in combination with
flucytosine, but flucytosine cannot be used alone because of resistance.
Ketoconazole and intravenous itraconazole have also been used successfully.
ASERGILLOSIS
ETIOLOGY
This is the most widely
spread fungi that causes disease in human hosts. The fungi is filamentous and
is omnipresent, it is found wherever organic debris occurs, especially in soil,
decomposing plant matter, house hold dust, building materials, some foods and
water. In fact, it is almost impossible to avoid inhalation of Aspergillus
spores the etiological agent are cosmopolitan. In people with healthy immune
system Aspergillus does not cause disease. However, infection results when
healthy immune system functions deteriorate.
PATHOGENSIS
Aspergillus fumigates is
the usual of pulmonary Aspergillus. A flavus is more common in some locations
such as hospitals than, A fumigates and is apparently more common in the air. A
flavus is the leading cause of invasive disease of immune suppressed patients
and the most common cause of superficial infection. Invasive disease typically
results in pulmonary infection (with liver, bone or skin).
In immuno competent patients. Asperillus localized broncho
pulmonary infections. Invasion Asperillosis has a mortality rate of 50 to 100%.
The major portal of entry a Aspergillus is the respiratory tract. Inhalation of
condiospores can lead to several types of pulmonary Aspergillosis. One type is
allergic Aspergillosis. Infected individuals may develop an immediate allergic
response and suffer asthma attacks when exposed to fungal antigens on the
condiospores. The major clinical manifestation of the allergic response is a
bronchii resulting from both type I and type III hypersensitivities. Although
tissue invasion seldom occurs in broncho pulmonary Aspergillosis., the fungi
often can be cultured from the sputum, where it forms colonies within the lungs
that develop into “fungus balls” called Asperillomas.
These
consist of a tangled mass hyphae growing in a circumscribed area. From the
pulmonary focus, the fungus may spread, producing disseminated Aspergillosis in
a variety of tissues and organs.
In patients whose
resistance is severely compromised invasive Aspergillosis may occur and fill
the lung with fungal hyphae.
CULTURE
Aspergillosis spp
grow readily at 35-370C on sabroud agar without cyclohexamine.
LABORATORY DIAGNOSIS
The fungi depends on
identification, either by direct examination of pathological specimens or by isolation
and characterization of the fungus. An enzyme immune essay that detects
galactomannan (an exoantigen of asperillus) can be used to screen suspected
case of aspergillosis.
TREATMENT
It is with
voriconazole and triaconazole.
REFERENCES
Opportunistic mycosis
Wikipedia the free encyclopedia.
Scribed, October
9, www.scribed.com dod 7314372
Dermatol clinic 2003,395
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