MLT GlobeMOH exam preparation (UAE) – page 9
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
The oxidation of ammonia to nitrite by soil bacteria such as Nitrosomonas is called:
Nitrification converts ammonia to nitrite then nitrate. Denitrification reduces nitrate to nitrogen gas.
Which form of leprosy has the highest bacillary load and is most infectious?
Poor cell-mediated immunity in lepromatous leprosy allows huge numbers of bacilli (multibacillary) shed from nasal mucosa. Tuberculoid disease is paucibacillary.
Ciprofloxacin and other fluoroquinolones kill bacteria by inhibiting:
Fluoroquinolones inhibit DNA gyrase (topoisomerase II) and topoisomerase IV. Rifampicin inhibits RNA polymerase.
Which group of infections is most characteristic of Staphylococcus aureus?
S. aureus causes localised pyogenic infections (furuncles, abscesses, bullous impetigo). Scarlet fever is caused by S. pyogenes.
The commonest cause of community-acquired urinary tract infection is:
Uropathogenic E. coli causes about 70–80% of uncomplicated UTIs. Proteus and Pseudomonas are more common with catheters or stones.
Vibrio cholerae on TCBS agar forms colonies that are:
V. cholerae ferments sucrose, turning the bromothymol blue indicator yellow. V. parahaemolyticus does not and forms green colonies.
Which gram-negative organism is a leading cause of neonatal meningitis?
E. coli with K1 capsule and group B streptococcus are the main causes of neonatal meningitis. Group A streptococcus is not.
Borrelia recurrentis, transmitted by lice, causes:
Antigenic variation produces recurring fever episodes, and spirochaetes are seen in blood films during fever. Q fever is caused by Coxiella burnetii.
Staphylococcus aureus grows in terms of oxygen requirement as a:
S. aureus grows with or without oxygen, using respiration or fermentation. Micrococci are obligate aerobes.
Which property is typical of Shigella?
As Enterobacterales, Shigella is oxidase-negative. It is non-motile, does not ferment lactose rapidly and is urease-negative.
A urine report shows many white cells (pus cells). This is termed:
Pyuria means leucocytes in urine, often from infection. Haematuria is blood; oliguria and anuria describe reduced output.
Among Enterobacterales, which route accounts for most horizontal spread of acquired antimicrobial resistance genes between cells?
Conjugation of resistance plasmids (often carrying transposons and integrons) is the main vehicle of horizontal resistance transfer. Point mutation is vertical, not transfer; transformation and transduction occur but are less important in Gram-negative rods.
A blood bank screens every donation for hepatitis B infection. Which method is routinely used to detect HBsAg?
HBsAg screening uses immunoassays (ELISA or chemiluminescence), which are cheap, automated and sensitive. PCR is used mainly for viral load and NAT, not routine first-line serology.
A virus hides silently in sensory ganglion neurons for decades and later reactivates. Which virus family behaves this way?
Alphaherpesviruses (HSV, VZV) establish lifelong latency in sensory ganglia and reactivate as cold sores or shingles. Toga-, picorna- and orthomyxoviruses cause acute infections.
Hepatitis C is often called a "silent" infection. Which feature explains why screening, not symptoms, finds most cases?
Most acute HCV infections cause no symptoms, yet many become chronic and slowly lead to cirrhosis. Cases are found by anti-HCV screening with RNA confirmation.
Which innate lymphocytes kill virus-infected cells early, recognising cells that have lost MHC class I, before specific T cells appear?
NK cells detect "missing self" (reduced MHC I) and stress ligands on infected cells and lyse them within days. Neutrophils mainly target bacteria.
The term "arbovirus" describes viruses grouped by which shared feature?
Arboviruses (arthropod-borne) are carried by mosquitoes, ticks or sandflies, e.g. dengue and West Nile viruses. HIV, influenza and rhinovirus spread without vectors.
Which of these viruses is primarily hepatotropic, causing acute hepatitis as its main disease?
HAV replicates mainly in hepatocytes, causing acute hepatitis. HSV and EBV only occasionally involve the liver, and HIV targets CD4 cells.
Which statement about infectious mononucleosis is correct?
Classic mononucleosis is EBV infection, typically in adolescents, with heterophil antibodies and atypical lymphocytes. Treatment is supportive.
Echoviruses were named "enteric cytopathic human orphan" viruses. Which site do they primarily infect?
Echoviruses are enteroviruses that replicate in the gut and are shed in feces, though they can spread to cause meningitis or rash.