Epidemiology and successful control of a large outbreak due to Klebsiella pneumoniae producing extended-spectrum beta-lactamases

Abstract

An outbreak due to extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) was detected from May 1993 to June 1995. A total of 145 patients, particularly patients in intensive care units (ICUs) (107 patients [72%]), were colonized or infected. Infection developed in 92 (63%) patients, and primary bacteremia caused by ESBL-KP was the most frequent infection (40 of 92 patients [43%]). A single clone of ESBL-KP was identified by pulsed-field gel electrophoresis analysis throughout the whole period, and no molecular epidemiological relationship could be found between the epidemic strain and non-ESBL-KP isolates. To determine risk factors for ESBL-KP infection weekly rectal swabs were obtained in three serial incidence surveys (470 patients); the probabilities of carriage of ESBL-KP in the digestive tract were 33% (October and November 1993), 40% (May and June 1994), and 0% (October and November 1995) at 10 days of ICU admission. A logistic regression model identified prior carriage of ESBL-KP in the digestive tract (odds ratio, 3.4; 95% confidence interval 1.1 to 10.4) as an independent variable associated with ESBL-KP infection. A statistically significant correlation was observed between the restricted use of oxyimino-beta-lactams (189 defined daily doses [DDD]/ 1,000 patient-days to 24 DDD/1,000 patient-days) and the trends of ESBL-KP infection (r = 0.7; P = 0.03).

FIG. 1

Numbers of patients colonized or infected with K. pneumoniae over the course of the study period.

FIG. 2

ESBL-KP and non-ESBL-KP incidence rates in ICUs after the implementation of the restricted use of oxyimino-β-lactams in ICUs.

FIG. 3

Probability of remaining free of digestive tract colonization with ESBL-KP. Line with slashes, first period; line with squares, second period; solid line, third period.

FIG. 4

PFGE of total DNA from K. pneumoniae isolates cut with XbaI. (A) ESBL-KP isolates. Lane 1, PFGE marker (New England BioLabs); lanes 2 and 3, isolates from the blood of non-ICU patients; lanes 4 to 6 and 10, isolates from the blood of ICU patients; lanes 7 and 8, 11 and 12, and 13 and 14, isolates from the blood and feces of three patients, respectively; lane 9, blood isolate with a susceptibility pattern different from those of the other isolates. (B) Non-ESBL-KP isolates. Lane 1, PFGE marker (New England BioLabs); lanes 2 to 8, 10, 11, 13, and 14, isolates from the blood of 11 patients, respectively; lanes 9 and 12, non-ESBL-KP strains isolated from the blood of the same patient during two different episodes of bacteremia, respectively.