Susceptibility to tigecycline of isolates from samples collected in hospitalized patients with secondary peritonitis undergoing surgery

Activity of tigecycline against nosocomial secondary peritonitis isolates collected along 18 months in 29 Spanish hospitals was tested by Etest in a central laboratory, considering Food and Drug Administration (FDA)/British Society for Antimicrobial Chemotherapy (BSAC)/European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. A total of 600 facultative/aerobic isolates (392 Gram negative, 208 Gram positive) and 100 anaerobes were tested. None of the 220 Escherichia coli isolates was resistant to tigecycline (MIC50/MIC90 = 0.25/0.5 μg/mL), with 0.5% (FDA breakpoint) and 3.6% (BSAC/EUCAST breakpoint) intermediate strains. All Extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates (15 strains), all Klebsiella pneumoniae, and Klebsiella oxytoca isolates (42 strains) were susceptible to tigecycline. No isolates resistant to tigecycline were found among Streptococcus viridans, Staphylococcus aureus, and Enterococcus faecium, but 18.9% of Enterococcus faecalis strains were intermediate following BSAC/EUCAST breakpoints. All (but 1) isolates of the Bacteroides fragilis group (n = 45) were tigecycline susceptible, as well as Gram-positive anaerobes. Tigecycline offers an adequate activity profile against isolates from secondary peritonitis when tested by Etest regardless of the breakpoints used for categorization.