'''Bacteria''' are an [[order]] of [[life]]single-celled microorganisms. Modern [[pathology]] and [[medicine]] are based on the findings of [[Louis Pasteur]] that bacteria cause many ailments.
Bacterial disease was a source of fear for humankind for most of history. This fear was largely abated by the development of [[antibiotic]] drugs in the last half of the 1900s. The general impression was that most bacterial diseases could be cured, relatively quickly and easily. But bacteria [[evolution|evolve]] resistances to certain types of antibiotics, making their continued treatment in a recurrent infection difficult at times.<ref>http://www.chemheritage.org/educationalservices/pharm/antibiot/readings/evolve.htm</ref> Bacterial disease is becoming a more serious medical problem, particularly in hospitals which tend to harbor a population of drug-resistant bacteria.