OPPORTUNISTIC MYCOSES
Candida yeasts that is, fungi that exist predominantly in a unicellular form. small (4-6 µm), thin-walled, ovoid cells (blastospores) that reproduce by budding. do not require special fungal media for cultivation. forms, pseudohyphae, and hyphae may be found in microscopic examination of clinical specimens stains gram-positive. form smooth, creamy white, glistening colonies that may resemble staphylococcal colonies.
creamy colonies
Candida A rapid, presumptive identification of C. albicans can be made by placing the organism in serum and observing germ tube formation small projections from the cell surface that appear within 90 minutes. However, both false-negative and falsepositive germ tube formation may occur.
Candida albicans Chlamydospore formation is also used to identify C. albicans. There are more than 150 species of Candida, but only a small percentage are regarded as frequent pathogens for humans CHROMagar
Chromagar
Chromagar
C. albicans recovered from soil, animals, hospital environments, inanimate objects, and food. Nonalbicans species may live in animal or nonanimal environments. Only rarely are Candida spp. laboratory contaminants. The organisms are normal commensals of humans and are commonly found on skin, throughout the entire gastrointestinal (GI) tract, in expectorated sputum, in the female genital tract, and in the urine of patients with indwelling Foley catheters.
C. albicans There is a relatively high incidence of carriage on the skin of health care workers. Although the vast majority of Candida infections are of endogenous origin, human-to-human transmission is possible: thrush of the newborn, which may be acquired from the maternal vagina, balanitis in the uncircumcised man, which may be acquired through contact with a partner having Candida vaginitis. Candida infection can be acquired from the hospital environment. İn immunocompromised patients: systemic infection( AIDS/diabetes..)
ASPERGILLOSIS Mold Aspergillus Invasive aspergillosis a major cause of morbidity and mortality in immunosuppressed patients. fungus ball due to aspergillus (also known as aspergilloma); allergic responses to Aspergillus, including allergic bronchopulmonary aspergillosis (ABPA); semi-invasive or invasive infections, (chronic necrotizing pneumonia to invasive pulmonary aspergillosis ) and other syndromes of tissue invasion.
easily cultured grow rapidly (within 24-72 hours) at a broad range of temperatures on a variety of media. A distinguishing characteristic of pathogenic Aspergillus species is their ability to grow at 37 C. In addition, strains of A. fumigatus are able to grow at temperatures of 50 C, a feature that, in addition to morphology, can also be used to identify this species. Most species initially appear as small, fluffy white colonies on culture plates within 48 hours. Presumptive identification of an Aspergillus species is usually readily accomplished by appearance of the fungus on gross and microscopic inspection of the colony growing on medium, which provides typical sporulation.
Aspergillus fumigatus most pathogenic species most common species in invasive infection, Colonies of A. fumigatus are typically gray-green with a wooly to cottony texture. hyphae are hyaline (lightly pigmented), have septa, usually branched at acute (typically 45 degrees) angles. The conidial head is columnar with conidiophores that are smooth walled and uncolored, or darkened in the upper portion near the vesicle. Like other Aspergillus spp., it is widespread in nature found in soil, on decaying vegetation, in the air, and, more recently, in water supplies.
Aspergillus flavus common isolate in sinusitis as well as in skin and invasive infections. produces an aflatoxin, is found in soil and decaying vegetation. Colonies are olive to lime green and grow at a rapid rate.
Aspergillus terreus common soil-related isolate that has been increasingly reported in invasive infection in immunocompromised hosts. conidia are small (2.0-2.5 µm), and the colony color and fruiting structures are characteristic for this species. A distinguishing feature : the presence of globose accessory conidia that are produced on hyphae. resistance to many antifungals, including amphotericin B
Aspergillus niger found in soil, on plants, and even in food and condiments (such as pepper). Colonies are initially white but quickly become black with the production of the pigmented fruiting structures. It grows rapidly with a pale yellow reverse. The role of A. niger in invasive infection is less well established, with its decreased pathogenicity perhaps due in part to the fact that its larger conidia do not readily reach deep into lung tissues. common colonizing isolate and can cause superficial infection, such as otitis externa.
Diagnosis and Susceptibility Testing invasive aspergillosis requires a tissue biopsy showing invasion with hyphae and a positive culture for Aspergillus. The diagnosis can also be established with positive cultures from a normally sterile site such as a needle biopsy or cerebrospinal fluid (CSF), although blood cultures are rarely positive. not distinguishable from a number of other opportunistic molds, including Fusarium, Scedosporium (Pseudallescheria), and others so that a positive culture is needed to confirm the diagnosis. Cultures for Aspergillus in respiratory samples in high-risk patients, particularly if obtained via bronchial alveolar lavage, can support the diagnosis of probable invasive aspergillosis. Aspergillus is also cultured from patients in whom no clinical illness is apparent so that positive cultures in patients with a low risk for invasive aspergillosis should be interpreted with caution.
Nonculture methods Radiographic findings Detection of galactomannan by EIA nonspecific fungal marker β-glucan using a variation of the limulus assay to detect endotoxin. Molecular diagnostics including polymerase chain reaction (PCR) have also been developed for Aspergillus.
CRYPTOCOCCOSIS a chronic, subacute to acute pulmonary, systemic or meningitic disease, initiated by the inhalation of basidiospores and/or desiccated yeast cells of Cryptococcus neoformans :encapsulated immunocompromised hosts predominantly the commonest cause of fungal meningitis; worldwide, 7-10% of patients with AIDS are affected. Meningitis is the predominant clinical presentation with fever and headache as the most common symptoms. Secondary cutaneous infections occur in up to 15% of patients with disseminated cryptococcosis and often indicate a poor prognosis. Lesions usually begin as small papules that subsequently ulcerate, but may also present as abscesses, erythematous nodules, or cellulitis.
ZYGOMYCOSIS Mucorales, causing subcutaneous and systemic zygomycosis (Mucormycosis) : Rhizopus, Mycocladus (Absidia), Rhizomucor, Mucor, Cunninghamella, Saksenaea, Apophysomyces, Cokeromyces Mortierella
ZYGOMYCOSIS in the debilitated patient,the most acute and fulminate fungal infection known. typically involves the rhino-facial-cranial area, lungs, gastrointestinal tract, skin, or less commonly other organ systems. often associated with acidotic diabetes, starvation, severe burns, intravenous drug abuse, and other diseases such as leukemia and lymphoma, immunosuppressive therapy, or the use of cytotoxins and corticosteroids, therapy with desferrioxamine (an iron chelating agent for the treatment of iron overload) and other major trauma. The infecting fungi have a predilection for invading vessels of the arterial system, causing embolization and subsequent necrosis of surrounding tissue. A rapid diagnosis is extremely important if management and therapy are to be successful.
OTHER MYCOSES DUE TO YEASTLIKE FUNGI Malassezia spp. usually catheter related tend to occur in premature infants other patients receiving lipid infusions Trichosporon spp. catheter-associated fungemia also via the respiratory or gastrointestinal tract most common cause of noncandidial yeast infection in patients with hematologic malignancies, mortality with excess of 80%
Rhodotorula spp. carotenoid pigments (pink to red colonies) variably encapsulated, budding yeast cells immuncompromised patients and those with indwelling devices central venous catheter infection, fungemia ocular infections peritonitis meningitis
Blastoschizomyces capitatus Hematologic malignancies Part of normal skin flora Similar diseases like Trichosporon Blood cultures usually positive
MYCOSES DUE TO OTHER HYALINE MOLDS (Hyalohyphomycosis) Hyaline (nonpigmented) septate, Branching Filamentous fungi(may be indistinguishable from Aspergillus) Fusarium Fungal keratitis (contact lenses) 75% of patients with positive blood cultures Macroconidia,microconidia
Scedosporium Antifungal resistant opportunistic pathogen Disseminated or located infections (corneal ulcers, endophtalmitis, sinusitis, pneumonia, endocarditis, meningitis, arthritis, osteomyelitis)
Acremonium Similar Fusarium Positive blood cultures Disseminated skin lesions Commonly found in soil, decating vegetation
Paecilomyces uncommon invasive disease in organ and hematopoietic stem cell recipients individuals with AIDS other immunocompromised patients through skin or intravascular catheters Trichoderma previously non pathogenic immuncompromised patients peritoneal dialysis fatal disseminated disease
Scopulariopsis Usually in nails Serious deep infection in neutropenic leukemia patients Nasal system, skin and soft tissues, blood, lungs,brain
Deep infections PHAEOHYPHOMYCOSIS
PNEUMOCYSTOSIS Pneumocystosis jirovecii (formerly P.carinii) especially in AIDS patients reservoir unknown respiratory tract is main portal of entry involvement of lymph nodes, spleen, bone marrow, genitourinary tract, eyes, ears,skin, thyroid Laboratory diagnosis: Giemsa, calcuflour, immunflorescence!
Mycotoxins/Mycotoxicosis
MYCOTOXINS and MYCOTOXICOSIS as opportunistic pathogens, filamentous fungi can produce toxins. cause diseases called mycotoxicosis following ingestion, inhalation or direct contact with the toxin acute/ chronic rapid death to tumor formation more than 100 toxigenic fungi over 300 compounds as mycotoxins
Dangerous in countries where methods of food handling, storage inadequate malnutrition prevelant few regulations to protect exposed populations
Aflatoxins primarily by Aspergillus flavus A.parasiticus Many other aspergillus species A.flavus most common in agriculture Corn, cottonseed, peanut Aflatoxin B1 most potent natural carcinogen toxicity and carcinogenicity
Aflatoxins Acute aflatoxicosis...death Chronic aflatoxicosis...cancer, immunsuppression LIVER is the main target organ Hepatitis in human Chronic low level exposure to toxin...development of hepatocellular carcinoma Consumption of contaminated foods Aerosols in dust, in air near farm sources Pulmonary cancer in animals, not enough evidence in human
Other mycotoxins Citrinin :significance in human disease not known Ergot Alkaloids:ingested when contaminated grain used for bread or in cereals :important for also veterinary, gangrene, abortion, seizures, ataxia Fumonisins: Corn pathogen:esophageal cancer Ochratoxin:Urinary tract tumours Trichothecenes: dermatitis, intoxication