Comparison of fecal versus rectoanal mucosal swab sampling for detecting Escherichia coli O157:H7 in experimentally inoculated cattle used in assessing bacteriophage as a mitigation strategy.
This study was conducted to compare fecal grab (FEC) and rectoanal mucosal swab (RAMS) techniques as sampling methods for surveillance of Escherichia coli O157:H7 in conjunction with administration of a mitigation therapy. The study was nested within a larger experiment that investigated bacteriophage as a preharvest strategy for controlling E. coli O157:H7 in feedlot steers. Samples (FEC and RAMS) were collected from 16 of the 32 feedlot steers (control and oral bacteriophage treatment; n = 8) involved in the mitigation study. All steers had been inoculated on day 0 with 10(10) CFU of nalidixic acid-resistant E. coli O157:H7, and samples were collected on 16 occasions over the next 83 days. FEC samples were assessed by direct plating of serial dilutions in PBS, plus a 6-h enrichment and immunomagnetic separation when E. coli O157:H7 concentrations were below limits detectable by direct plating (i.e., <1 log CFU/g). All RAMS samples were assessed by enrichment and immunomagnetic separation. E. coli O157:H7 was detected more frequently (P < 0.01) by FEC than by RAMS. Overall, 213 of 256 samples were positive either by FEC or RAMS. Discrepancies between sampling techniques were observed in 63 of the 213 positive samples; FEC missed 11 samples that were positive by RAMS, and RAMS missed 52 of those positive by FEC (miss rates of 5.16 and 24.41%, respectively). Kappa values (0.36 to 0.45) indicated only fair to moderate agreement between FEC and RAMS results, but this agreement was higher at lower levels of E. coli O157:H7 shedding (later in the experimental period). Selection of sampling procedure could significantly influence the assessed merit during testing of potential strategies for controlling E. coli O157:H7 on the farm.
Niu
Y D
YD
Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, Liaoning, People's Republic of China.
Xu
Y
Y
McAllister
T A
TA
Rozema
E A
EA
Stephens
T P
TP
Bach
S J
SJ
Johnson
R P
RP
Stanford
K
K
D001003:Anal Canal / Q000382:microbiology; D000818:Animals; D001435:Bacteriophages / Q000502:physiology; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control*; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology*; D008297:Male; D008460:Meat / Q000382:microbiology; D011897:Random Allocation; D012007:Rectum / Q000382:microbiology; D012680:Sensitivity and Specificity