Enterobacterial repetitive intergenic consensus-polymerase chain reaction typing of Escherichia coli isolated from hospitalized neonates

Abstract

Objective To explore the genetic relationship among the isolates of Escherichia coli, and to analyze the epidemiological status. Methods One hundred and ten strains of Escherichia coli were isolated from 102 hospitalized neonates in the Neonatal Center of Beijing Children's Hospital. The homologous relation among the strains were typed and studied by using enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) method. Results One hundred and two cases of neonates were selected, including 61 male cases and 41 female cases. Among them, 94 cases were full-term infants, 8 cases were preterm infants, 25 cases≤7 days, and 77 cases>7 days. One hundred and ten strains of Escherichia coli isolated clinically by ERIC-PCR typing were divided into 58 types, fingerprints indnded 4-12 bands, and the similarity coefficient was between 26.2% and 100.0%. The dominant genotype contained 6 strains, with 4-5 bands, and the similarity coefficient was 88.9%-100.0%. In dominant genotype E58, 5 out of 6 strains were attacked in March, and 1 strain attacked by the end of February. In the second dominant type E32, 4 out of 5 strains were spread in May, and 1 strain in July. In E23 type, 4 out of 5 strains were distributed in September, and 1 strain in October. There were 8 pairs of clinical isolates from 8 neonatal patients, including 7 pairs of them belonging to the same genotype, and the other 1 pair of isolates did not belong to the same genotype and was distantly related. From homology analysis point of view, the possibility of the different isolates was infectious or contaminant. Two strains were isolated from the blood and cerebrospinal fluid of the same patient, belonging to the same genotype, with 100.0% similarity coefficient. Five isolates were confirmed to have closer relationship by ERIC-PCR genotyping. One isolate derived from a child and the other 4 isolates derived from the other 4 children were considered hospital-acquired infection since these five children shared one ward. Conclusions Escherichia coli infections in full-term infants are more common. Most of them are late infections, and boys are more than girls. Different seasons may have different types of epidemic caused by Escherichia coli infection of respiratory tract. Strains of high homology hospital-acquired infection by Escherichia coli was found at Beijng Children's Hospital had Escherichia coli hospital-acquired infection. ERIC-PCR typing method can track the source of infection, which plays a role in prevention and control of nosocomial infection. Key words: Escherichia coli; Enterobacterial repetitive intergenic consensus; Polymerase chain reaction; Infant, newborn