Correspondence

If, as [Burke A Cunha] asserts, cephalosporins have a low resistance potential, how does he explain the rapid selection and global dissemination of almost 100 bla.m variants, which, together with nearly 30 blaSHV genes and many other bla genes confer resistance to a wide range of -lactam antibiotics, including, third-generation cephalosporins?5 Selection for any one of these resistance determinants will ensure the perpetuation of other resistance markers even if they are not selected for directly. Since resistance determinants may be allied closely to bacterial cellular housekeeping functions, the selective pressure for the maintenance of resistance need not necessarily involve the continued use of the target antibiotic. Classification of antibiotics as having high or low resistance potential is subjective and dependent on too many ill-defined parameters to be useful in controlling the spread of antibiotic resistance. Indeed, some prescribers get the impression that profligate prescribing is resistance-risk-free. Antibiotics must be used responsibly and restrictively, irrespective of perceived resistance potential, to control resistance. *John Heritage, Mark Wilcox, Jonathan Sandoe