Carbapenemases: a problem in waiting?
Carbapenems are stable to most prevalent beta-lactamases, and chromosomal carbapenemases are restricted to Stenotrophomonas maltophilia, to a few Bacteroides fragilis, and to rare pathogens. Nevertheless, an acquired metallo-beta-lactamase called IMP-1 is beginning to emerge in Pseudomonas aeruginosa and Enterobacteriaceae isolates in Japan, and has also been found in isolates from Singapore. Furthermore, IMP-producing Acinetobacter spp. have been identified in Italy and Hong Kong. Recently a second group of acquired metallo-carbapenemases, the VIM types, has been recorded from P. aeruginosa isolates in five Eurasian countries. Weak carbapenemases belonging to molecular class D are emerging in A. baumannii world-wide, with two sub-groups apparent. A few acquired carbapenemases belonging to molecular class A also have been reported. Finally it has also been shown that enzymes with feeble carbapenemase activity (e.g. AmpC types and some SHV enzymes) may confer resistance in exceptionally impermeable strains; counterwise, even potent carbapenemases, such as IMP-1, may only give a small reduction in susceptibility in Enterobacteriaceae that lack permeability lesions. Is the emergence of carbapenemase a problem waiting to happen?
Livermore
D M
DM
Antibiotic Resistance Monitoring and Reference Laboratory, Central Public Health Laboratory, 61 Colindale Avenue, NW9 5HT, London, UK. dlivermore@phls.nhs.uk
Woodford
N
N
D015780:Carbapenems / Q000378:metabolism* / Q000627:therapeutic use*; D011995:Recombination, Genetic; D013379:Substrate Specificity; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D015780:Carbapenems; D001618:beta-Lactamases