Six methicillin-resistant strains of isolated in Britain were examined for loss of resistance after storage for 30 mth at room temperature. Resistance to methicillin was lost from five out of six, to tetracycline from four out of six, to erythromycin from two out of four, and penicillinase from all five that were producers of it. The methicillin-sensitive segregants resembled the wild strains in bacteriophage-typing pattern, haemolysin production, Tween 80 reaction, pigmentation, and resistance to lysostaphin and to other antibiotics.

Methicillin resistance was transduced from lysates of three of the strains. Although the effect of ultraviolet light was characteristic for a plasmid gene in strain no. 11164, transduction occurred at low frequency (10-10) from this and from the other strains, and to a narrow range of recipients. Methicillin resistance was not transferred to recipients in mixed culture.

In contrast, plasmid genes determining lactamase production, or resistance to tetracycline or erythromycin, were transduced from lysates and transferred in mixed cultures from these strains at frequencies from 10-10. These results may account for the confinement of methicillin resistance to few types of staphylococci whilst other resistance genes have become much more widespread.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error