Evolution among Antibiotic Resistance Plasmids in the Hospital Environment
Plasmid mediated resistance to antibiotics was first discovered about 25 years ago in Japan because of the unexpected appearance of multiple drug resistance during an outbreak of bacillary dysentery (1). Ever since this time the unexpected appearance of a new or unusual drug resistance marker or an unusual pattern of multiple drug resistance has been a clue that plasmids might be involved as carriers of the resistance genes, and in many cases the ‘epidemic strain’ of the pathogen involved in the outbreak has been found to contain one or more resistance plasmids. Spectacular examples of this are the extensive epidemic of bacillary dysentery due to Shigella dysenteriae Type I in Central America and southern Mexico during 1969–70, investigated by Mata, et al. (2) and the somewhat smaller but still dramatic epidemic of typhoid fever which occurred in and around Mexico City in 1972, investigated by Olarte et al. (3). In both instances the epidemic strain was found to contain a plasmid which conferred resistance to multiple antibiotics. On a smaller scale, many outbreaks of hospital-associated infection have been shown to be due to a particular strain of a gram-negative organism which contains one or more plasmids.
KeywordsTyphoid Fever Serratia Marcescens Bacillary Dysentery Multiple Drug Resistance Large Plasmid
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