Sensitivity of an immunomagnetic-separation-based test for detecting Escherichia coli O26 in bovine feces.
The sensitivity of a test for cattle shedding Escherichia coli serogroup O26 was estimated using several fecal pats artificially inoculated at a range of concentrations with different E. coli O26 strains. The test involves the enrichment of fecal microflora in buffered peptone water, the selective concentration of E. coli O26 using antibody-coated immunomagnetic-separation beads, the identification of E. coli colonies on Chromocult tryptone bile X-glucuronide agar, and confirmation of the serogroup with E. coli serogroup O26-specific antisera using slide agglutination. The effective dose of E. coli O26 for an 80% test sensitivity (ED(80)) was 1.0 x 10(4) CFU g(-1) feces (95% confidence interval, 4.7 x 10(3) to 2.4 x 10(4)). Differences in test sensitivity between different E. coli O26 strains and fecal pats were also observed. Individual estimates of ED(80) for each strain and fecal pat combination ranged from 4.2 x 10(2) to 4.8 x 10(5) CFU g(-1). These results suggest that the test is useful for identifying individuals shedding a large number of E. coli O26 organisms or, if an appropriate number of individuals in a herd are sampled, for identifying affected herds. The study also provides a benchmark estimate of sensitivity that can be used to compare alternative tests for E. coli O26 and a methodological approach that can be applied to tests for other pathogenic members of the Enterobacteriaceae and other sample types.
Hall
L M
LM
Scottish Agricultural College, Stratherrick Rd., Inverness IV2 4JZ, United Kingdom. malcolm.hall@sac.ac.uk
Evans
J
J
Smith
A W
AW
Pearce
M C
MC
Knight
H I
HI
Foster
G
G
Low
J C
JC
Gunn
G J
GJ
D000818:Animals; D001431:Bacteriological Techniques; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D015169:Colony Count, Microbial; D003470:Culture Media; D004197:Disease Reservoirs; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology*; D018189:Immunomagnetic Separation / Q000379:methods*; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity
D003470:Culture Media