Transmission dynamics of ESBL-producing Escherichia coli clones in rehabilitation wards at a tertiary care centre.

Increasing resistance due to the production of ESBL in Escherichia coli (ESBL-E. coli) has become a major threat to public health. Our aims were to study the incidence of ESBL-E. coli acquisition during hospitalization and the transmission rates of different ESBL-E. coli clones. This was a prospective case-control study, conducted in two geriatric rehabilitation wards in Tel-Aviv. Serial rectal cultures were collected from admission till discharge. All patient-unique ESBL-E. coli isolates were subjected to molecular typing by PFGE, MLST and determination of ESBL genes. An acquisition of ESBL-E. coli was defined as traceable when a patient with the same ST, PFGE type and ESBL gene was hospitalized in the same ward in parallel to the acquisition case. ESBL-E. colis were recovered from 125 patients out of 492 enrolled: 52 were recovered upon admission, 59 acquired ESBL-E. coli during their stay, and there was undetermined status in 14 patients. A low Norton's score was associated with acquisition (O.R. 1.14 for each point, 95% C.I. 1.01-1.29, p < 0.05). ESBL-E. coli infections (n = 9) had occurred only in ESBL-E. coli carriers. The pandemic ST131 clone was the most common (48/125). The majority of the isolates (101/125) produced CTX-M-type ESBL. Of the 59 acquisition cases, 32 were traced to another patient. In-hospital dissemination was highest in the CTX-M-27-producing ST131 and the SHV-5-producing ST372 sub-clones (acquisition/admission ratios of 17/11 and 9/3, respectively), with almost all cases traced to other patients. In conclusion, most ESBL-E. coli acquisition cases were traceable to other patients. The transmission potential varied significantly between ESBL-E. coli clones.