Although the blaIMP genes can migrate into A. baumannii,
they do not appear to be a major contributor to carbapenem
resistance. A new group of transferable class D blactamases
have emerged almost exclusively in A. baumannii
and are capable of increasing the MIC of imipenem
to 16mg/L or higher. The first of these enzymes
(OXA-23) was found in Scotland 15 years ago [21]. This
enzyme was transferable [22] and had a unique amino
acid sequence [23
]. Thought to be an isolated observation,
blaOXA-23 has subsequently been found in Brazil [24]
and very recently has been reported to be responsible for
two outbreaks in southeast England. A second group of
class D carbapenemases has been found in A. baumannii
isolated largely in southwest Europe, these enzymes
share about 60% homology with OXA-23 [25]. The success
of the vancomycin-resistance operon in Grampositive
pathogens and transferable carbapenamses in
Gram-negative pathogens is certain to make treatment
of hospital infection very difficult or near impossible. The
introduction of linezolid and the streptogrammins might
M