Extrachromosomal and Chromosomal Drug Resistance in Methicillin Resistant Staphylococcus Aureus

Antibiotic resistance plasmids of Staphylococcus aureus and their clinical importance.

“…This number of copies would seem to represent relaxed replication, although attempts to alter the numbers of copies per cell by incubation in the presence of tetracycline have not been successful (110). However, in two strains, Kayser et al (99,100) found that tetracycline resistance is chromosomal; this has been confirmed for one of these strains (I. Chopra, and R. W. Lacey, unpublished observations). In this strain, there is no covalently closed circular DNA equivalent to tetracycline resistance, the resistance is stable after growth at 43 C, and the frequency of transduction of the resistance was stimulated > 10-fold by UV light.…”

“…Genes that determine neomycin resistance may be present in plasmids conferring resistance to streptomycin and other antibiotics (see below). In many resistant strains, however, neomycin resistance is not accompanied by resistance to streptomycin and is plasmid mediated (13,14,37,45,99,100,103,112). Neomycin resistance is unstable under most cultural conditions.…”

“…Thus the specificity of the recipient is striking. (v) The frequency of transduction of methicillin resistance is increased to a moderate extent by UV light irradiation (49,99,100). This presumably indicates that the transduced genes have become integrated into recipient genetic material, which may or may not be the chromosome.…”

“…However, in 1967 and 1968, neomycin resistance appeared in several countries, including the United Kingdom, Switzerland, and Denmark in a variety of "new" strains as judged by marked variations in their phage-typing and antibiotic sensitivity patterns (Table 7; 37,99,100,103,112,150).…”

Genetic basis, epidemiology, and future significance of antibiotic resistance in Staphylococcus aureus: a review.

“…There are several reports of an extrachromosomal locus for these genes (Chabbert et al, 1964;Novick and Bouanchaud, 1971;Kayser, Felix, and Wust, 1972;.…”