MLT GlobeMOH exam preparation (UAE) – page 10
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
Amantadine inhibits which virus, though resistance now limits its clinical use?
Amantadine blocks the M2 ion channel of influenza A, preventing uncoating; influenza B lacks M2. Most circulating influenza A strains are now resistant.
Which virus is spread mainly by the fecal-oral route rather than by an arthropod?
Coxsackieviruses are enteroviruses shed in stool. Dengue and yellow fever are mosquito-borne, and Colorado tick fever is tick-borne.
A pathology report uses the older term "hepatoma". Which tumour does it refer to?
Hepatoma is an older synonym for hepatocellular carcinoma, a malignancy strongly linked to chronic HBV and HCV infection.
A traveller returns from South Asia with sudden high fever, retro-orbital pain, severe muscle and joint pain, a rash and low platelets. Which infection is most likely?
Dengue ("breakbone fever") causes fever, headache, retro-orbital pain, myalgia, arthralgia, rash, leukopenia and thrombocytopenia. NS1 antigen or RT-PCR confirms early infection.
Which lesion is classically caused by herpes simplex virus type 1 rather than type 2?
HSV-1 classically causes oral and facial lesions and adult encephalitis; HSV-2 mainly genital and neonatal infection. Zoster is VZV reactivation.
Which type of vaccine is used to prevent hepatitis A?
Licensed hepatitis A vaccines (e.g. Havrix) contain whole HAV inactivated with formalin and adsorbed to alum. Recombinant HBsAg vaccines are for hepatitis B.
A child has a very itchy rash with crops of vesicles at different stages on the trunk and face. Which virus causes chickenpox?
Chickenpox is primary VZV infection; lesions in various stages (papules, vesicles, crusts) are typical. Later reactivation causes zoster.
A patient has a painful vesicular eruption along one thoracic dermatome. Which specimen best confirms varicella-zoster virus?
Unroofing a fresh vesicle and swabbing its base gives cells and fluid rich in virus for PCR or DFA; PCR is now the method of choice.
Several people develop jaundice, diarrhoea and raised transaminases about four weeks after eating raw shellfish. Which virus is most likely?
HAV is spread fecal-orally, including via filter-feeding shellfish, and causes acute hepatitis with jaundice after a 2-6 week incubation. Norovirus from shellfish causes vomiting within 1-2 days.
What type of genome can a virus have?
A virion contains only one type of nucleic acid, DNA or RNA, which may be single- or double-stranded, linear or circular.
Making mRNA from a DNA template is called:
Transcription is DNA-directed RNA synthesis. Translation makes protein from mRNA, and reverse transcription makes DNA from RNA.
On a thin film, infected red cells are enlarged to about 1.5–2 times normal and contain irregular amoeboid trophozoites. Which Plasmodium species is most likely?
P. vivax prefers reticulocytes, which it enlarges markedly, and has amoeboid trophozoites. P. falciparum, P. malariae and P. knowlesi leave the red cell normal-sized or smaller.
In a fresh stool from a patient with bloody diarrhoea, an amoeboid trophozoite containing ingested red blood cells is seen. This finding points to:
Erythrophagocytosis is the most reliable microscopic marker of invasive E. histolytica (it distinguishes it from the look-alike E. dispar). The other organisms do not ingest red cells.
Which of these helminths is a tapeworm rather than a fluke?
D. latum is a cestode (fish tapeworm). Fasciola (liver), Fasciolopsis (intestine) and Paragonimus (lung) are trematodes.
Which feature is shared by all fungi?
Fungi are eukaryotes whose cell walls contain chitin and glucans; they are heterotrophic (saprophytic or parasitic) and never photosynthetic or worm-like.
Giardia duodenalis trophozoites show a 'falling leaf' motility in a saline mount. Which organelles drive this movement?
Giardia trophozoites have eight flagella in four pairs, giving characteristic tumbling motility. Cilia belong to Balantidium, pseudopodia to amoebae.
Of the following flagellates found in humans, which is a recognised pathogen?
T. vaginalis causes vaginitis and urethritis. Chilomastix, Pentatrichomonas and T. tenax are commensals.
A pig farmer develops dysentery caused by a large ciliated protozoan. Which animal is the main reservoir of this infection?
Balantidium coli is carried commonly by pigs, and human infection follows contact with pig faeces. Cats are linked to Toxoplasma and dogs to Echinococcus.
Chagas disease (American trypanosomiasis) is caused by:
T. cruzi causes Chagas disease, transmitted by triatomine bugs. T. b. gambiense causes African sleeping sickness and L. donovani causes kala-azar.
The term 'infestation' is used for parasites that live on the host's surface. Which group does this describe?
Infestation refers to ectoparasites (lice, mites, ticks) on skin or hair; endoparasites inside the body cause infection.