title: Susceptibility of Xanthomonas maltophilia and amikacin-resistant gram-negative bacteria to newer antimicrobials.
abstract: The susceptibility of Xanthomonas maltophilia and amikacin-resistant gram-negative bacteria to a variety of newer antimicrobials was determined. Sixty-three amikacin-resistant isolates were collected from 61 inpatients at a tertiary-care hospital between 1985 and 1988. The organisms included Xanthomonas maltophilia (24 isolates), Pseudomonas aeruginosa (16), Pseudomonas species (3), Serratia marcescens (10), Flavobacterium meningosepticum (4), Enterobacter species (3), Acinetobacter calcoaceticus var. anitratus (2), and Alcaligenes xylosoxidans (1). Amikacin resistance was initially determined by using the Kirby-Bauer disk diffusion method. The isolates were batched, and the minimum inhibitory concentrations (MICs) of 11 antimicrobials including amikacin were measured by using the standard agar dilution method. Of the 63 isolates initially found to be amikacin resistant by the disk diffusion method, 37% were found to be amikacin susceptible by MIC testing. Of 38 truly amikacin-resistant isolates, 76% were susceptible to ciprofloxacin, 63% to ofloxacin, 50% to imipenem-cilastatin, 47% to cefoperazone, 45% to ceftazidime, 13% to ceftizoxime, 11% to aztreonam, 11% to ceftriaxone, 5% to cefotetan, and 3% to amdinocillin. Ciprofloxacin and ofloxacin inhibited X. maltophilia to the greatest degree, with median MICs of 1 microgram/ml each. Fifteen amikacin-resistant Ps. aeruginosa isolates were inhibited by ciprofloxacin, imipenem, and ceftazidime, with median MICs of 0.375, 3, and 2 microgram/ml, respectively. Of the antimicrobials tested, ciprofloxacin had the greatest activity against amikacin-resistant organisms in vitro.
authors.affiliation: Veterans Affairs Medical Center, Boise, ID.
authors.forename: J R
authors.initials: JR
authors.lastname: Matsuyama
authors.forename: B
authors.initials: B
authors.lastname: Beail
authors.forename: C
authors.initials: C
authors.lastname: Wallis
authors.forename: D
authors.initials: D
authors.lastname: Zeleznik
authors.forename: T
authors.initials: T
authors.lastname: Tartaglione
mesh_terms: D042462:4-Quinolones; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000583:Amikacin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D004352:Drug Resistance, Microbial; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D007769:Lactams; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D014974:Xanthomonas / Q000187:drug effects*
chemical_list: D042462:4-Quinolones; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D007769:Lactams; D000583:Amikacin