PrepTest 154, Section 3, Question 16
For nearly a century after the discovery in(452 more words not shown)
It can be inferred from(24 more words not shown)
- AV. cholerae cannot(7 more words not shown)
- BV. cholerae 's(7 more words not shown)
- CV. cholerae responds(7 more words not shown)
- DV. cholerae cannot(13 more words not shown)
- EV. cholerae 's(11 more words not shown)
Reading the passage
The numbers to explain are 51 out of 52 versus seven out of 52, using the same water samples. Why would the antibody test find bacteria that culture methods miss?
What we’re looking for
Culture methods require the bacteria to grow. The antibody method detects a feature of their cells. If some living bacteria aren't reproducing, the second method can reveal them while the first cannot. That gives us a specific explanation for the gap, beyond simply saying the new test is better.
Working the answers
- ACorrect
The bacteria cannot always be grown in a culture dish. The dormant state explains why: they are viable but have stopped reproducing. So a sample can contain living bacteria, yield a positive antibody result, and still produce no growth in the culture test. That directly explains the much lower culture count.
- B
A limit on binding would be a problem for the antibody method, the method that found far more positive samples. It doesn't explain why growth-based detection missed bacteria that the antibody method found.
- C
Temperature and salinity may help explain reactivation. This choice doesn't identify the difference between the two detection methods that produced these results.
- D
Culture techniques did find bacteria in seven of the water samples. That contradicts the idea that culturing requires samples from human tissue or waste. The issue is whether the bacteria reproduce, not a rule limiting cultures to human material.
- E
The fluorescent molecule is linked to the antibody used in the test; it isn't described as a normal component of the bacterium's membrane. In any event, explaining a light signal alone wouldn't explain why the culture method misses so many bacteria.
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