Atypical Chryseobacterium meningosepticum and meningitis and sepsis in newborns and the immunocompromised, Taiwan.

From 1996 to 1999, 17 culture-documented systemic infections due to novel, atypical strains of Chryseobacterium meningosepticum occurred in two newborns and 15 immunocompromised patients in a medical center in Taiwan. All clinical isolates, which were initially misidentified as Aeromonas salmonicida by an automated bacterial identification system, were resistant to a number of antimicrobial agents. The isolates were characterized as atypical strains of C. meningosepticum by complete biochemical investigation, 16S rRNA gene sequence analysis, cellular fatty acid analysis, and random amplified polymorphic DNA fingerprinting (RAPD). This is the first report of a cluster of atypically variant strains of C. meningosepticum, which may be an emerging pathogen in newborns and the immunocompromised

Incidence of Constitutive and Inducible Clindamycin Resistance in Staphylococcus aureus and Coagulase-Negative Staphylococci in a Community and a Tertiary Care Hospital

The incidences of inducible clindamycin resistance at two hospitals (an inner-city hospital and a suburban community hospital) were 7 and 12% for methicillin-resistant Staphylococcus aureus, 20 and 19% for methicillin-susceptible S. aureus, and 14 and 35% for coagulase-negative staphylococci, respectively. Given the variability of inducible resistance to clindamycin found in our two hospitals, we conclude that susceptibility testing of staphylococci should include the disk diffusion induction test (D-test)

Characteristics of NDM-1-Producing Escherichia coli Isolates That Belong to the Successful and Virulent Clone ST131▿

An NDM-1 carbapenemase-producing Escherichia coli isolate of sequence type 131 (ST131) that belonged to phylogenetic group B2 was obtained from a patient with a urinary tract infection who returned to the United States after a recent hospitalization while visiting India. NDM-1-producing E. coli ST131 had significantly more virulence factors than NDM-1-producing E. coli ST101, previously isolated from a patient in Canada. The presence of NDM β-lactamases in a very successful and virulent E. coli sequence type is of concern

Accuracies of β-Lactam Susceptibility Test Results for Pseudomonas aeruginosa with Four Automated Systems (BD Phoenix, MicroScan WalkAway, Vitek, and Vitek 2)

Contemporary clinical isolates and challenge strains of Pseudomonas aeruginosa were tested by four automated susceptibility testing systems (BD Phoenix, MicroScan WalkAway, Vitek, and Vitek 2; two laboratories with each) against six broad-spectrum β-lactams, and the results were compared to reference broth microdilution (BMD) and to consensus results from three validated methods (BMD, Etest [AB Biodisk, Solna, Sweden], and disk diffusion). Unacceptable levels of error (minor, major, and very major) were detected, some with systematic biases toward false susceptibility (piperacillin-tazobactam and imipenem) and others toward false resistance (aztreonam, cefepime, and ceftazidime). We encourage corrective action by the system manufacturers to address test biases, and we suggest that clinical laboratories using automated systems should consider accurate alternative methods for routine use

Multicenter Studies of Tigecycline Disk Diffusion Susceptibility Results for Acinetobacter spp.

Acinetobacter sp. isolates having multidrug resistance (MDR) patterns have become common in many medical centers worldwide, limiting therapeutic options. A five-center study tested 103 contemporary clinical Acinetobacter spp., including MDR strains, by reference broth microdilution and disk diffusion (15-μg disk content) methods against tigecycline. Applying U.S. Food and Drug Administration tigecycline breakpoint criteria for Enterobacteriaceae (susceptibility at ≤2 μg/ml [≤1 μg/ml by the European Committee on Antimicrobial Susceptibility Testing]; disk diffusion breakpoints at ≥19 mm and ≤14 mm) to Acinetobacter spp. led to an unacceptable error rate (23.3%). However, an adjustment of tigecycline disk diffusion breakpoints (susceptible/resistant) to ≥16/≤12 mm reduced intermethod errors to an acceptable level (only 9.7%, all minor)