Klebsiella, Enterobacter, Citrobacter, Serratia, Plesiomonas, and OtherEnterobacteriaceae

Abstract

This chapter talks about the new species of Enterobacteriaceae that have been added to or transferred between existing genera. Most common gram-negative organisms isolated from respiratory tract, urinary tract, and bloodstream infections from intensive care unit patients in the United States were K. pneumoniae (15%), E. cloacae (9%), Serratia marcescens (6%), Enterobacter aerogenes (4%), Proteus mirabilis (4%), Klebsiella oxytoca (3%), and Citrobacter freundii (2%). The organisms are, in general, readily isolated from clinical material, and few of the clinically relevant strains covered present difficulties in isolation from sterile body sites. Isolation from nonsterile body or environmental sites may require specialized media such as CHROMagar Orientation and chromID CPS, which perform similarly for the detection of urinary tract pathogens covered in the chapter and can reliably replace MacConkey and blood agars. The chapter also discusses diarrheal pathogens that are easily isolated, and about biochemical tests most useful for separating members. Even when unusual enterobacteria covered in the chapter are included in commercial system databases, the number of strains available to use in challenge studies is very limited; therefore, the ability of these systems to accurately identify these organisms is really unknown. General antimicrobial susceptibility and specialized phenotypic testing procedures are also discussed in the chapter.