Variations in colistin susceptibility among different species of the genus Acinetobacter

nalidixic acid, chloramphenicol and sulfamethoxazole. 12 This study is the first report of a P. stutzeri isolate exhibiting fluoroquinolone resistance that was related at least to mutations in gyrA and parC topoisomerase genes. References 1 Grimaldi D, Podglajen I, Aubert A et al. Case of indolent endocarditis due to Pseudomonas stutzeri with genetic evidence of relapse after 4 years. 6 Mammeri H, Poirel L, Mangeney N et al. Chromosomal integration of a cephalosporinase gene from Acinetobacter baumannii into Oligella urethralis as a source of acquired resistance to b-lactams. 8 Poirel L, Rodriguez-Martinez JM, Al Naiemi N et al. Characterization of bla DIM-1 , a novel integron-located metallo-b-lactamase gene from a Pseudomonas stutzeri clinical isolate in the Netherlands. 9 Akasaka T, Tanaka M, Yamaguchi A et al. Type II topoisomerase mutations in fluoroquinolone-resistant clinical strains of Pseudomonas aeruginosa isolated in 1998 and 1999: role of target enzyme in mechanism of fluoroquinolone resistance. 11 Miro E, Verges C, Garcia I et al. Resistance to quinolones and b-lactams in Salmonella enterica due to mutations in topoisomerase-encoding genes, altered cell permeability and expression of an active efflux system. 12 Jude F, Arpin C, Brachet-Castang C et al. TbtABM, a multidrug efflux pump associated with tributyltin resistance in Pseudomonas stutzeri. Sir, Bacteria of the genus Acinetobacter with Acinetobacter baumannii in particular have emerged as important nosocomial pathogens, especially for patients in intensive care. 1 A. baumannii has a remarkable capacity to develop resistance to all clinically relevant antimicrobial agents. Strains of this species resistant to most available agents are encountered in hospitals worldwide. The recent spread of carbapenem resistance has drastically narrowed options for treatment of A. baumannii infections and has led to the reintroduction of polymyxins with colistin in particular for the systemic treatment of infections caused by these bacteria. 1 Even though A. baumannii is clinically and epidemiologically the most important species of the genus, other Acinetobacter species have also been implicated in human infections and strains of some of these species may also be multidrug resistant combined with the ability to spread among hospitalized patients. 1 Currently, 22 species with valid names and at least 11 additional putative species are recognized within the genus with as many as 25 of them having been found in human specimens. 1,2 However, the identification of Acinetobacter species in diagnostic laboratories is cumbersome owing to the lack of practical diagnostic systems providing reliable identification of these …