Emergence of a Plasmid Mediated blaVIM-1 in Citrobacter koseri: Report from the SENTRY Antimicrobial Surveillance Program (Italy)

Citrobacter koseri can be a cause of sepsis and meningitis, leading to central nervous system abscesses in neonates and young infants with associated high mortality rates, among other infections.1 Reports of complicated C. koseri infections in adolescents and adults have increased in recent years, 2, 3 showing that the importance of this pathogen is not limited to younger children alone. The antimicrobial treatment of infections caused by C. koseri has been changing due to several reports of isolates carrying extended-spectrum b-lactamases and other resistance encoding genes. Resistance to carbapenems remains rare; however, antimicrobials in this class have been used to treat the most serious C. koseri infections.1, 2 A total of 428 C. koseri isolates were submitted to the sEnTRY Antimicrobial surveillance Program during the 2000-2005 period. These isolates were consecutively collected in 105 medical centers located in north America, Latin America, Asia-Pacific and Europe from bloodstream infections, skin and soft tissue infections, urinary tract infections and pneumonia in hospitalized patients according to defined protocols. Only clinically significant non-duplicate patient isolates were included in the study. species identification was confirmed by standard biochemical tests and/or using the Vitek system (bioMérieux, Hazelwood, Missouri, UsA), where necessary. All isolates were susceptibility tested against more than 25 antimicrobials by reference broth microdilution procedures as described by the CLsi 4 using validated panels manufactured by TREK Diagnostics (Cleveland, Ohio, UsA). escherichia coli ATCC 25922 and pseudomonas aeruginosa ATCC 27853 were routinely included during testing for quality assurance. in general, C. koseri isolates showed 97.7 to 100.0% susceptibility to all agents tested, including piperacillin/tazobactam, cephalosporins, carbapenems, aminoglycosides, tetracyclines, fluoroquinolones and polymyxin B (table 1). Meropenem and imipenem exhibited the best in vitro activity against this species (MiC50, <0.12 and <0.5 mg/L, respectively); however, one isolate (75-8776A) displayed decreased susceptibility to imipenem (MiC, 8 mg/L; intermediate). This strain was recovered in July 2005 from a blood culture specimen collected from a 51 y/o male patient hospitalized in a hematology-oncology ward in a hospital in Genoa, italy. The index isolate remained susceptible to meropenem, aztreonam, amikacin, gentamicin and tigecycline (table 2).