Investigation of an extended-spectrum beta-lactamase-producing Escherichia coli outbreak in a geriatrics department.

An outbreak of extended-spectrum beta-lactamase-producing (ESBL) Escherichia coli urinary tract infection occurred on one floor of a department of the G. Clemenceau hospital. There were nine cases from March to August 1994, all of which resolved under antimicrobial therapy. Two further cases occurred, leading to a program of routine rectal swab cultures in all patients on the floor involved (first floor). ESBL E. coli carriage was found in six patients. Follow-up rectal swabs were obtained until September 1995 from all patients on the floor who were infected or colonized with ESBL E. coli between March and October 1994. Between March and June 1995, routine rectal swabs were also obtained from the patients on the other two floors of the department. Seven other carriers were detected and also underwent follow-up rectal swabs until September 1995. Ribotyping of the strains done at the national enteric molecular typing center (Pasteur Institute, Paris) demonstrated four patterns (CM1, CM2, CM3, and CM4). The strains from the first six carriers all shared the CM1 pattern, whereas among the seven carriers detected later, four (second and third floors) had a CM1 strain and the remaining three (first floor) each had a strain of the three other ribotypes (CM2, CM3, and CM4). ESBL E. coli can be carried in the digestive tract for several months. During the outbreak, the same strain was found in all the patients, whereas a variety of strains were found after the outbreak in patients without clinical symptoms due to ESBL E. coli. Routine rectal swab cultures are useful for evaluating the extent of outbreaks. However, the only effective outbreak control measures are compliance with strict hygiene procedures (signalization, technical and geographic isolation) and appropriate antimicrobial therapy. These measures were effective at the G. Clemenceau Hospital since there have been no further cases of ESBL E. coli since they were implemented. The rectal swab program has therefore been stopped, whereas strict universal hygienic precautions are still adhered to faithfully.