Chlamydias are
Answer: D
Correct answer: All the above
Chlamydiae are non-motile, obligate intracellular parasites that cannot be grown on cell-free media - they must be cultured in living cells, because they cannot make their own ATP and depend on the host’s. That energy dependence is what defines them.
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Dark ground microscopy is used for detection of
Answer: A
Correct answer: spirochetes
Dark-ground (dark-field) microscopy lights the specimen obliquely so that only scattered light enters the objective, making a very thin unstained object shine against a black background. It is the standard way of seeing Treponema pallidum, which is too slender for ordinary bright-field work and stains poorly.
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Which of the following is true about the viral envelope?
Answer: D
Correct answer: All the above
All three are true of the viral envelope: it is derived from a host cell membrane as the virus buds out; it is therefore lipoprotein in nature; and it carries projecting spikes (peplomers) of virus-coded glycoprotein, which are what bind the receptor on the next cell. Being lipid, it is destroyed by soap and by ether - which is why enveloped viruses are the easier ones to disinfect.
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Killed corpuscular vaccines contain
Answer: C
Correct answer: inactivated bacteria
A killed corpuscular vaccine contains whole bacteria inactivated by heat or chemicals. Nothing multiplies, so it is safe and stable but generally needs a larger dose and booster injections. The old typhoid, cholera and whooping cough vaccines were of this kind.
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Monoclonal antibodies are used in
Answer: D
Correct answer: All of the above
Monoclonal antibodies are used for all three: as therapeutic agents, since a single specificity can be directed at one target; for the identification of cells and tissues, as in typing leukaemias by their surface markers; and, radiolabelled, for imaging, localising a tumour by where the antibody accumulates.
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Live vaccines contain
Answer: A
Correct answer: attenuated bacteria
A live vaccine contains organisms that have been attenuated - weakened by repeated passage or by mutation so that they multiply in the recipient without causing disease. Because they multiply, the dose is small and the immunity strong and long-lasting; the price is that they must be kept cold and are unsafe for the immunocompromised. BCG and oral polio are examples.
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