MLT GlobeDHA exam preparation (Dubai) – page 9
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
Which statement about mumps is correct?
Mumps may cause orchitis, oophoritis and pancreatitis besides parotitis. It has one serotype, grows in cell culture, and is prevented by live MMR vaccine.
The name "reovirus" is an acronym. What does it stand for?
Reoviruses were isolated from respiratory and enteric tracts but not linked to any disease, hence "orphan".
Human papillomavirus types 6 and 11 are the usual cause of which lesion?
Low-risk HPV 6 and 11 cause genital warts; high-risk types 16 and 18 cause cervical and other anogenital cancers. HCC is linked to HBV/HCV.
A young man with painful parotid swelling develops painful testicular swelling a week later. Which virus is responsible?
Orchitis occurs in about 20-30% of post-pubertal males with mumps; it is usually unilateral and rarely causes sterility.
Enterobacteria phage lambda belongs to which group of viruses?
Viruses that infect bacteria are bacteriophages; lambda infects E. coli. Virophages parasitise giant viruses, and arboviruses are carried by arthropods.
Which base is found in RNA and replaces thymine in DNA?
RNA uses uracil in place of thymine to pair with adenine. Adenine, guanine and cytosine are found in both nucleic acids.
In a protozoan life cycle, what is the active, motile stage that feeds and multiplies inside the host called?
The trophozoite is the vegetative, feeding and dividing form. Sporozoites and merozoites are invasive stages of apicomplexans, and gametocytes are sexual precursor cells.
How do most medically important fungi reproduce and disperse?
Fungi multiply mainly through spores (conidia, sporangiospores, ascospores and others), which are also what laboratories identify microscopically. Cysts, ova and trophozoites belong to protozoa or helminths.
A skin scraping is treated with KOH plus calcofluor white to look for fungal hyphae. Which microscope is needed to read it?
Calcofluor white binds chitin and cellulose and fluoresces blue-white under UV/blue excitation, so a fluorescence microscope is required. It is not visible with ordinary bright-field illumination.
Novy–MacNeal–Nicolle (NNN) biphasic medium is used to culture which parasite?
On NNN medium Leishmania amastigotes transform into motile promastigotes. Trichomonas is grown in Diamond's/InPouch media, Entamoeba in xenic media, and Cryptococcus is a yeast grown on fungal media.
A parasite that cannot complete its life cycle or survive without a host is termed:
Obligate parasites depend entirely on a host. Facultative parasites can also live freely, accidental parasites infect an unusual host, and 'paratenic' describes a transport host, not a parasite type.
'Ringworm' (tinea) of the skin is caused by which organism?
Ringworm is a dermatophyte fungal infection caused by Microsporum, Trichophyton or Epidermophyton; no worm is involved. Cryptococcus is a yeast causing meningitis.
An itchy papulovesicular rash on the feet of a barefoot farmer ('ground itch') is caused by skin penetration of:
Ground itch is the local reaction to hookworm L3 larvae entering the skin. Avian schistosome cercariae cause swimmer's itch after water exposure, not soil contact.
Harmless microorganisms normally living on skin, in the upper respiratory tract and in the gut are best described as:
Normal microbiota are commensals: they live on the host without causing disease. Saprophytes feed on dead matter in the environment.
Echinococcus granulosus, the cause of hydatid disease, is classified as a:
E. granulosus is a small cestode living in the dog intestine; its larval hydatid cyst develops in humans. It is not a protozoan.
Lactophenol cotton blue (LPCB) mounting fluid is routinely used in the laboratory to examine:
LPCB kills, preserves and stains fungal elements (chitin takes up cotton blue), making it the standard mount for mould identification. Protozoa use iodine or trichrome; blood parasites use Giemsa.
Which genus is NOT a dermatophyte?
Dermatophytes comprise Microsporum, Trichophyton and Epidermophyton (plus newer genera like Nannizzia). Madurella causes eumycetoma, a subcutaneous infection.
Moulds that obtain nutrients from dead and decaying organic matter are called:
Saprophytic fungi decompose dead matter; many (e.g. Aspergillus) can become opportunistic pathogens, but their nutritional mode is saprophytic.
A yeast from a vaginal swab is incubated in serum at 37°C for 2–3 hours and produces germ tubes. The organism is most likely:
The germ tube test presumptively identifies C. albicans (and C. dubliniensis). C. glabrata and Cryptococcus are germ tube negative; C. difficile is a bacterium.
Which feature does NOT describe tapeworms (cestodes)?
Cestodes are flat, segmented hermaphrodites. A cylindrical unsegmented body is characteristic of nematodes.