Natural β-lactam susceptibility and mechanisms of β-lactam resistance in Yersinia enterocolitica

Within a genospecies, mechanisms affecting natural susceptibility to a particular antibiotic are assumed to be identical. An exception to the rule has been proposed for the biovars of Yersinia enterocolitica with respect to beta -lactams. beta -lactam antibiotics are used frequently in the treatment of infections caused by Y. enterocolitica, which is responsible for a wide spectrum of human diseases including enterocolitis, lymphadenitis and ileitis. Whereas there are no differences in susceptibility to some beta -lactams among the biovars, there are significant differences in susceptibility to several others. A sound predictive statement about therapeutic success can be made using the phenotype of natural resistance. Treatment of infections with antibiotics to which the aetiological agents are naturally resistant should be avoided, as clinical and bacteriological success cannot be expected. This review discusses the molecular basis of the natural susceptibility patterns of Y. enterocolitica to beta -lactam antibiotics against the background of its taxonomy and epidemiological data. The text focuses on the biovar-dependent differences in beta -lactam susceptibility, which are caused in particular by the action of two different chromosomally encoded beta -lactamases, beta -lactamase A and beta -lactamase B. It is shown that the expression of these enzymes depends on the biovar and on the individual strain but that further mechanisms must be involved in beta -lactam resistance. (C) 2000 Lippincott Williams & Wilkins.