MLT GlobeMOH exam preparation (UAE) – page 22
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
MRSA resists nearly all beta-lactams because mecA encodes:
PBP2a has low affinity for beta-lactams, so wall synthesis continues. Efflux and gyrase mutations explain tetracycline and quinolone resistance.
Urinalysis shows many pus cells, yet the routine aerobic urine culture yields no growth. Which of the following is LEAST likely to explain this finding?
Sterile pyuria reflects inflammation without growth on routine media: mycobacteria, chlamydiae and prior antibiotics all cause it. Suprapubic aspiration is simply a contamination-free collection method, not a cause of pyuria.
Some bacteriophages carry a lysozyme-like enzyme in their tail. What is its role during infection?
Phage tail lysozyme punches a hole in the peptidoglycan so the DNA can be injected; later, endolysins lyse the cell for release. Animal viruses do not need this enzyme.
Which statement about viral hepatitis is FALSE?
Anti-HCV EIA is the standard screening test, confirmed by HCV RNA. HDV is a defective virus using HBsAg as its coat, and alcohol accelerates HCV liver disease.
Adeno-associated virus (a dependoparvovirus) cannot complete replication alone. Which helper virus classically supplies the missing functions?
AAV is a defective parvovirus requiring co-infection with adenovirus (or herpesvirus) for productive replication, hence the name adeno-associated virus.
Tobacco mosaic virus is typical of most plant viruses in genome type. What is that genome?
The majority of plant viruses, including TMV, have positive-sense ssRNA genomes. DNA plant viruses (geminiviruses, caulimoviruses) are the minority.
When an electron micrograph report describes a virus as "isometric", what capsid symmetry is usually meant?
Isometric (roughly spherical) viruses almost always have icosahedral symmetry. Helical viruses are rod-shaped or filamentous; complex/binal describes poxviruses and tailed phages.
Infectious mononucleosis is suspected in a teenager. Which investigation is NOT practical for routine diagnosis?
EBV cannot be grown in routine cell culture. Diagnosis uses heterophil antibodies and EBV-specific serology (VCA IgM/IgG, EBNA).
Years after an early-childhood infection, a child develops progressive behavioural decline, myoclonus and very high CSF antibody titres. Subacute sclerosing panencephalitis follows which virus?
SSPE is a rare, fatal, persistent measles infection of the brain affecting grey and white matter, with high measles antibody in CSF. It is prevented by measles vaccination.
The first rotavirus vaccine (RotaShield) was withdrawn in 1999. Which adverse event led to its withdrawal?
RotaShield was linked to intussusception. Current oral rotavirus vaccines carry a much smaller risk and are recommended worldwide.
Endemic Burkitt lymphoma in African children, with a t(8;14) MYC translocation, is associated with which virus?
Nearly all endemic Burkitt lymphomas carry EBV, with malaria as a co-factor; high antibody to EBV early antigen (restricted pattern) is characteristic.
Which intestinal nematode can pass through several free-living generations in soil in addition to its parasitic cycle?
S. stercoralis has a heterogonic cycle with free-living adult males and females in soil. Hookworm larvae live in soil but do not form free-living adult generations, and Ascaris has no free-living stage.
In Trypanosoma and Leishmania, the 'kinetoplast' seen near the base of the flagellum is:
The kinetoplast is a DNA-rich region of the single large mitochondrion, lying next to the basal body. It stains dark with Giemsa and helps identify amastigotes.
Which intestinal helminth does NOT cause autoinfection (reinfection of the same host without an external phase)?
Ascaris eggs must embryonate in soil for weeks, so autoinfection cannot occur. H. nana, Enterobius and Strongyloides can all reinfect the same host.
In the human host, Plasmodium multiplies asexually in liver cells and red blood cells by which process?
Schizogony (multiple nuclear division producing merozoites) occurs in hepatocytes and RBCs. Sporogony is the sexual-phase multiplication in the mosquito.
Which finding confirms intestinal Taenia solium infection and distinguishes it from T. saginata?
Taenia eggs look alike, so species identification relies on gravid proglottids (T. solium 7–13 branches, T. saginata more than 12) or molecular tests. Tapeworms have no trophozoite or cercarial stage.
In current classification, malaria parasites belong to which phylum?
Plasmodium, with Toxoplasma and Cryptosporidium, belongs to the Apicomplexa (older term: Sporozoa), named for the apical complex used to invade cells. Platyhelminthes are flatworms.
Which of the following is a flagellate that lives in the human intestine?
Chilomastix mesnili is an intestinal commensal flagellate with a lemon-shaped cyst. T. vaginalis is urogenital, Endolimax is an amoeba, and Echinococcus is a tapeworm.
Which tapeworm can complete its whole life cycle in a single human host, without an intermediate host?
H. nana (dwarf tapeworm) eggs hatch in the villi, form cysticercoids and mature in the same host. The Taenia species and Echinococcus require intermediate hosts.
On a thin film, infected red cells are oval with fimbriated (ragged) edges and show James's dots. Which species is this?
P. ovale makes about a third of infected red cells oval with fimbriated margins. P. vivax enlarges cells but usually keeps them round.