MICRO 5

Domain Eukarya, Kingdom Fungi

What is the biological classification of fungi?

50,000

Approximately how many species of fungi have been identified?

150

How many fungal species are recognized as disease-causing agents in humans?

Resistant

How do humans typically react to fungal infections?

Accidental hosts

What status do humans have in fungal infections?

Inhalation of spores or trauma

What are the two common ways fungi are introduced into human tissue?

Immunocompromised

In which patient population are fungal infections most significant and severe?

Yeasts and Molds

What are the two major groups of fungi based on colony appearance?

Yeasts

Which fungi are unicellular and form moist, creamy, opaque colonies?

2 to 60 um

What is the size range of round to oval yeast cells?

Molds

Which fungi are multicellular and appear fluffy, cottony, woolly, or powdery?

Hyphae

What are the tube-like projections typical of molds?

Mycelia

What are the loose networks formed by mold hyphae?

Dimorphic

What term describes fungi able to express either yeast-like or filamentous forms?

Thermally dimorphic

What term describes fungi that change morphology depending on the temperature?

Mold

What morphology is expressed by dimorphic fungi at 25-30 C?

Yeast

What morphology is expressed by dimorphic fungi at 35-37 C?

Histoplasma, Blastomyces, Coccidioides, and Candida

What are four medically important examples of dimorphic fungi?

Mycoses

What is the general term for fungal diseases?

Superficial, cutaneous, subcutaneous, systemic, or opportunistic

What are the five clinical classifications of mycoses?

Superficial mycoses

Which fungal infections involve hair, skin, and nails without invading deeper tissues?

Dermatophytes, tinea, and piedra

What three categories are primarily included in superficial mycoses?

Subcutaneous mycoses

Which fungal infections are confined to the tissue under the skin and do not disseminate?

Chromoblastomycosis, mycetoma, and phaeohyphomycotic cysts

What are three examples of subcutaneous mycoses?

Systemic mycoses

Which fungal infections usually involve the lungs but can disseminate to any organ system?

Blastomyces, Coccidioides, Histoplasma, and Paracoccidioides

What are four examples of systemic mycoses?

Opportunistic mycoses

Which fungal diseases are caused by harmless fungi in compromised hosts?

Diabetes or use of immunosuppressant agents

What are two clinical settings that predispose a patient to opportunistic mycoses?

Aspergillus, Candida, and Cryptococcus

What are the three most common examples of fungi causing opportunistic diseases?

Potassium hydroxide

What chemical has traditionally been used for the direct microscopic examination of fungi?

Calcofluor white

What is generally preferable to KOH for fungal identification, especially with fluorescence?

Fluorescence microscopy

What type of microscopy is required for using calcofluor white?

Glass slide or scalpel

What tools are used to collect skin scrapings for fungal studies?

Sterilized inoculating loop

What tool is used to collect a liquid sample like urine for fungal studies?

2 to 3 drops

How much 10 percent KOH solution is mixed with a fungal sample on a slide?

Lactophenol cotton blue

What optional reagent can be added to a KOH preparation to improve visualization?

Close the condenser

What adjustment is made to the microscope to improve the visibility of fungal structures in KOH?

Yeast cells and hyphal elements

What are the two characteristic microscopic structures sought during a KOH exam?

Meningitis

Analysis of the CSF provides valuable information regarding whether or not a patient has what condition?

Intelligent guesses

What does the analysis of selected CSF parameters allow clinicians to make regarding etiologic agents?

Viral, bacterial, fungal, or non-infectious

What four causes of meningitis can be differentiated using CSF parameters?

Urgent

How is the examination of CSF classified in a clinical microbiology laboratory?

Meningitis is life threatening

Why is the diagnosis of meningitis considered an urgent procedure?

Immediate confirmed confirmation

What does the diagnosis of meningitis require regardingConfirmation?

Immediate Gram stain and culture

What two procedures must happen as soon as a CSF specimen is received?

Processed immediately without storage

How should a CSF specimen be handled upon receipt in the laboratory?

Promptly

How should all CSF results be reported to the physician?

Cell microscopy

Which CSF analysis section counts total white blood cells?

Determine which WBC type predominates

Besides the total count, what is the purpose of CSF cell microscopy?

Glucose and protein

What two concentrations are primarily checked in CSF chemistry?

Increased

Is protein concentration in the CSF usually increased or decreased in infections?

Destruction of tissue

Why is protein usually increased in an infected CSF?

Decreased

Is glucose concentration in the CSF usually increased or decreased in infections?

Increased utilization by microbes and host tissue

Why is glucose usually decreased in an infected CSF?

Lumbar puncture

What is the medical term for a spinal tap?

Physician

Who is responsible for collecting a CSF specimen?

Strict aseptic technique

Under what condition must a physician collect a CSF specimen?

At least three

What is the minimum number of sterile leak-proof tubes required for CSF collection?

Cell microscopy, chemistry, and microbiology

What are the three laboratory sections that receive the CSF tubes?

Prompt delivery

What is a must for CSF transport due to the nature of possible pathogens?

Fastidious

What term describes pathogens like Neisseria meningitidis that may die during transport?

Neisseria meningitidis and Hemophilus influenzae

What are two examples of fastidious CSF pathogens?

Volume of the sample

What is the usual limiting factor in testing CSF, especially in children?

Judicious use

How must a lab technician handle CSF specimens to accommodate all requested tests?

Plating onto culture media

Because it requires aseptic technique, what is usually the first laboratory step for CSF?

Sterile needle and syringe

What tools are used to aspirate CSF for culture plating?

0.5 ml

Approximately what volume of CSF is aspirated for plating?

BAP, MacConkey, and Chocolate agar

What are the three routine media used for CSF plating?

CO2 conditions

Under what environmental condition is Chocolate agar incubated for CSF specimens?

Gram stain and other stains

What is the remaining CSF in the syringe used for after plating?

AFB (Acid Fast Stain)

Which stain is requested if TB meningitis is suspected?

India Ink

Which stain is requested if Cryptococcosis is suspected?

Serology section

Which lab section might receive remaining CSF for rapid antigen detection?

Isolation of a bacterium

What is the gold standard for the diagnosis of bacterial meningitis?

5 percent sheep blood agar, Chocolate agar, Thioglycolate broth, and MacConkey agar

What are the four routine bacteriologic media for CSF?

CALAS and Streptex

What are two examples of rapid antigen or antibody tests for CSF?

Nigrosin stain

What is another name for the India ink stain?

Negative stain

How is the India ink stain classified?

Clear halos against a dark background

How does the capsule of an organism appear in an India ink preparation?

Basidiomycetous yeasts

What type of fungi are Cryptococcus neoformans?

Large polysaccharide capsules

What is the distinguishing structural feature of Cryptococcus neoformans?

Oval

What is the shape of Cryptococcus neoformans cells?

Pigeon, bat, and bird droppings

Where is Cryptococcus neoformans commonly found in nature?

Decomposing fruits and vegetables

What is another environmental source of Cryptococcus neoformans besides droppings?

Inhalational route

What is the mode of transmission for Cryptococcus?

Pneumonia

What lung condition can Cryptococcus cause initially?

Spinal column, brain parenchyma, and meninges

To what three sites can Cryptococcus disseminate?

Cryptococcal meningoencephalitis

What clinical disease results from disseminated Cryptococcus?

Immunodeficiency states

What is a major risk factor for Cryptococcus infection?

Low sensitivity

What is the primary diagnostic drawback of the India ink stain?

Latex agglutination or ELISA

Which two tests for Cryptococcus are more sensitive and specific than India ink?

One drop

How much India ink and CSF are placed on the slide for preparation?

HPO with low lighting

Under what microscope objective and lighting condition is India ink examined?

Gram-negative diplococci

What is the Gram stain morphology of Neisseria species?

Coffee beans or kidney beans

What do Neisseria diplococci resemble?

Flattened

How are the adjacent ends of Neisseria diplococci described?

True pathogens

How is Neisseria gonorrhoeae classified as a species?

Normal flora

Where are most Neisseria species, other than pathogens, typically found?

Mucosa of respiratory, alimentary, and genital tracts

What are three mucosal sites where normal Neisseria flora live?

Neisseria meningitidis

Which Neisseria inhabit oral and upper respiratory flora but can cause clinical disease?