Intestinal Colonization by Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae in Infants

Members of the Enterobacteriaceae family are common agents of nosocomial infections. Intestinal colonization by these microorganisms represents a major step in the development of systemic infection. Extended-spectrum b-lactamase-producing bacteria are usually associated with outbreaks, but endemic infections are common in intensive care units.

To determine the frequency of intestinal colonization with extended-spectrum b-lactamase-producing Enterobacteriaceae in newborns.

This was a descriptive cohort study. Newborns from two general hospitals (A and B) in Mexico City were included during a five-month period; those with a hospital stay > 7 days were selected. Fecal samples were obtained by rectal swab on day 7 and every week until discharge. Extended-spectrum b-lactamase production was confirmed in enterobacteria by the Etest. Clonal relatedness was established by pulsed-field gel electrophoresis.

102 newborns were included; 63/102 (61.7%) were colonized by extended-spectrum b-lactamase-producing Enterobacteriaceae on day 7, 17/21 (81%) on day 14, and 6/8 (75%) on day 21 of hospitalization. Klebsiella pneumoniae was recovered most frequently (75.4%). A predominant clone (95%) was found in hospital B, and a major clone (75%) in Hospital A. Other extended-spectrum b-lactamase-producing Enterobacteriaceae isolates were Enterobacter spp. (16%) and Escherichia coli (7.6%).

High rates of colonization and horizontal transmission of extended-spectrum b-lactamase-producing Enterobacteriaceae were found in the newborn care units of two general hospitals. Clonal relatedness was identified. Lack of adherence to standard precautions and hand hygiene were determining factors.