Increasing prevalence of gastrointestinal colonization with ceftazidime-resistant gram-negative bacteria among intensive care unit patients.

Background: The occurrence of nosocomial infections due to third-generation cephalosporin-resistant gram-negative bacteria is increasing. Gastrointestinal colonization is an important reservoir for antibiotic-resistant bacteria, and it often precedes clinical infection.

Objective: To estimate the prevalence of gastrointestinal colonization with ceftazidime-resistant gram-negative bacteria among intensive care unit (ICU) patients at a university-affiliated tertiary-care hospital during 2 distinct periods and to assess whether, at any time during the index hospitalization, colonized patients had a clinical culture positive for the same organism that was recovered from surveillance culture.

Setting: Two ICUs at the University of Maryland Medical Center, a 656-bed tertiary-care hospital located in Baltimore, Maryland. Both ICUs provide care to adult patients.

Methods: We performed a cross-sectional study of adult patients admitted to the medical ICU or the surgical ICU from June 14 to July 14, 2003, and from June 14 to July 14, 2006. Perirectal swab samples were obtained for surveillance culture on admission to the intensive care unit, weekly thereafter, and at discharge. Each culture sample was plated onto MacConkey agar supplemented with ceftazidime.

Results: In 2003, a total of 33 (18.8%) of 176 patients were colonized with ceftazidime-resistant gram-negative bacilli; in 2006, 60 (31.4%) of 191 patients were (P<.01). This increase was largely driven by an increase in ceftazidime-resistant Klebsiella isolates (which accounted for 6.4% of isolates in 2003 and for 22.8% in 2006; P<.01). In 2003, a total of 16 (48.5%) of 33 colonized patients had a clinical culture positive for the same organism that was recovered from the perirectal surveillance culture, compared with 22 (36.6%) of 60 colonized patients in 2006 (P=.28).

Conclusion: Our data suggest that gastrointestinal colonization with ceftazidime-resistant gram-negative bacilli is common, that its prevalence is increasing, and that colonization may result in clinical cultures positive for these bacilli.