One of the many interesting controversies that microbiologists can ponder today is whether the alarming proliferation of antibiotic-resistant strains is primarily a consequence of the widespread use of antibiotics in humans and in animal husbandry. An examination of bacteria isolated from terrestrial animals in the Galapagos, a remote location with limited exposure to humans, revealed an absence of antibiotic resistance genes. Likewise, plasmids from bacterial collections that predate the antibiotic era were mostly devoid of resistance elements. Furthermore, a study of Dutch soil samples showed an increase in antibiotic resistance genes in contemporary samplings as compared to those from the pre-antibiotic era. On the other hand, antibiotic resistance genes were both abundant and diverse in ancient DNA recovered from Pleistocene deposits (30,000 years ago). Likewise, a survey of present-day actinomycetes revealed that multidrug resistance was prevalent even though human sources of antibiotics were presumed absent in this environment.
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