Evaluation of colony-based examinations of diarrheagenic Escherichia coli in stool specimens: low probability of detection because of low concentrations, particularly during the early stage of gastroenteritis.
To evaluate traditional colony-based examinations of diarrheagenic Escherichia coli (DEC), we analyzed the proportions of 5 categories of DEC among E. coli in stool specimens from patients with gastroenteritis using real-time polymerase chain reaction with novel primers and probes. Among 81 DEC isolates, 48 (59.3%) were present at proportions of < or = 10%, whereas only 17 (21.0%) reached >50%. Low concentrations (< or = 10%) of DEC were found, particularly in most (71.8%) stool specimens collected within 48 h after the onset of illness, although such specimens were conventionally collected as close to the time of diarrhea onset as possible. Because the probability of detecting < or = 10% DEC by colony-based examinations is very low, traditional laboratory methods might not detect most DEC infections, especially at the start of gastroenteritis. Thus, a diagnosis of DEC infections requires a molecular method that targets not individual colonies but E. coli clusters.
Iijima
Yoshio
Y
Department of Microbiology, Kobe Institute of Health, 4-6 Minatojima-nakamachi, Chuo-ku, Kobe 650-0046, Japan. iijima@oak.ocn.ne.jp
Tanaka
Shinobu
S
Miki
Kanji
K
Kanamori
Shizuko
S
Toyokawa
Masahiro
M
Asari
Seishi
S
D001431:Bacteriological Techniques / Q000379:methods*; D004926:Escherichia coli / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000175:diagnosis* / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D005759:Gastroenteritis / Q000382:microbiology*; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity