The emergence of resistance of bacteria to antibiotics is a common phenomenon. Emergence of resistance often reflects evolutionary processes that take place during antibiotic therapy. The antibiotic treatment may select for bacterial strains with physiologically or genetically enhanced capacity to survive high doses of antibiotics. Under certain conditions, it may result in preferential growth of resistant bacteria, while growth of susceptible bacteria is inhibited by the drug. For example, antibacterial selection for strains having previously acquired antibacterial-resistance genes was demonstrated in 1943 by the Luria–Delbrück experiment. Antibiotics such as penicillin and erythromycin, which used to have a high efficacy against many bacterial species and strains, have become less effective, due to the increased resistance of many bacterial strains.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is a modern occurrence with high doeses?
Ah, so.. unanswerable

The city went through serious troubles in the mid-fourteenth century. On the one hand were the decimation of the population by the Black Death of 1348 and subsequent years of epidemics — and on the other, the series of wars and riots that followed. Among these were the War of the Union, a citizen revolt against the excesses of the monarchy, led by Valencia as the capital of the kingdom — and the war with Castile, which forced the hurried raising of a new wall to resist Castilian attacks in 1363 and 1364. In these years the coexistence of the three communities that occupied the city—Christian, Jewish and Muslim — was quite contentious. The Jews who occupied the area around the waterfront had progressed economically and socially, and their quarter gradually expanded its boundaries at the expense of neighbouring parishes. Meanwhile, Muslims who remained in the city after the conquest were entrenched in a Moorish neighbourhood next to the present-day market Mosen Sorel. In 1391 an uncontrolled mob attacked the Jewish quarter, causing its virtual disappearance and leading to the forced conversion of its surviving members to Christianity. The Muslim quarter was attacked during a similar tumult among the populace in 1456, but the consequences were minor.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): The Muslims lived near what current market?
Ah, so.. Mosen Sorel

The 10th century saw a mass migration of Turkic tribes from Central Asia into the Iranian plateau. Turkic tribesmen were first used in the Abbasid army as mamluks (slave-warriors), replacing Iranian and Arab elements within the army. As a result, the mamluks gained a significant political power. In 999, large portions of Iran came briefly under the rule of the Ghaznavids, whose rulers were of mamluk Turk origin, and longer subsequently under the Turkish Seljuk and Khwarezmian empires. These Turks had been Persianized and had adopted Persian models of administration and rulership. The Seljuks subsequently gave rise to the Sultanate of Rum in Anatolia, while taking their thoroughly Persianized identity with them. The result of the adoption and patronage of Persian culture by Turkish rulers was the development of a distinct Turko-Persian tradition.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What tribes migranted en masse to the Iranian plateau in the 10th Century?
Ah, so..
Turkic tribes