Since antibiotics are not very selective as to which bacteria they attack, those prescribed for a toothache can quickly wipe out a whole population of intestinal microbes.

因为抗生素对它要对抗的细菌没有很大的选择性，为治牙疼而开出抗生素可能会很快杀死一大批大肠中的细菌。

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In a straight fight, therefore, it was the drug-sensitive strain that had the selective advantage when faced with a two-pronged attack.

这场直接的菌群较量说明了当面对两种进攻的时候，敏感菌有优势。

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After promotion to lead the whole education portfolio he went on to attack Labour's grammar school policy, calling the selective system "as divisive as it is archaic" and telling MPs how 11-plus exam failures - including his brother - suffered for life.

BBC: Phil Willis: Education & Employment