The Enterobacteriaceae comprise several genera commonly referred to as the enteric gram-negative bacilli and several species less commonly encountered in clinical practice (Table 132.1). The unique features of Salmonella, Shigella, and Yersinia are considered in separate chapters. These organisms are ubiquitous in the environment and are readily recovered from water and soil. The human reservoir for most species is the colon, although other muscosal sites may become colonized, particularly in health care–related settings. Members of the Enterobacteriaceae are important causes of community-acquired and hospital-acquired infections of almost any organ system, with hospital-acquired strains increasingly demonstrating resistance to multiple classes of antibiotics through a variety of resistance mechanisms. This growing dilemma underscores the need for accurate diagnoses and intelligent use of a diminishing antimicrobial arsenal.

URINARY TRACT INFECTION

The Enterobacteriaceae are the most important etiology of both community-acquired and nosocomial urinary tract infection, with E. coli the most frequently encountered pathogen. The success of E. coli, in part, may be attributed to the adaptation of specialized adherence fimbriae that facilitate attachment to normal uroepithelium.

The symptoms of urinary tract infection are common to all uropathogens but may assist in defining the location and extent of infection. In women the three principle manifestations are urethritis, characterized primarily by dysuria; cystitis, characterized by frequency, urgency, dysuria, suprapubic tenderness with or without fever; or pyelonephritis, characterized by nausea and vomiting, fever, chills, flank pain and costovertebral angle tenderness.