Location: Poultry Microbiological Safety Research
Title: Modified ecometric technique (four-quadrant sequential streak) to evaluate Campylobacter enrichment broth proficiency in suppressing background microflora Authors
Submitted to: Poultry Science Association
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2009
Publication Date: July 20, 2009
Citation: Richardson, L.J., Cox Jr, N.A., Buhr, R.J., Cason Jr, J.A., Berrang, M.E. 2009. Modified ecometric technique (four-quadrant sequential streak) to evaluate Campylobacter enrichment broth proficiency in suppressing background microflora. Poultry Science Association. 88(S1):433P. P.132. Technical Abstract: Ecometric technique is a semi-quantitative scoring method used for quality control of culture media in microbiological laboratories. The technique involves inoculation with defined populations of specific culture onto solid media via a standardized chronological streaking technique, leading to ever-decreasing numbers of colonies. The objective was to evaluate a modified ecometric technique’s (four-quadrant sequential streak (FQS) procedure) efficacy in determining undefined background microflora levels in different Campylobacter enrichment broths. Acquisition of natural background microflora to evaluate the technique was achieved by using post-pick carcasses (n=30) obtained from a commercial poultry processing plant and performing a whole carcass rinse in 0.1% buffered peptone water and then separating the rinses for a total of 120 efficacy test samples. Aliquots (2mL) from each sample were transferred into 18 mL of Bolton and Tecra broth and incubated microaerobically at 42°C for 48 h. For the FQS procedure, an aliquot (10µL) from each type of sample was transferred onto campy-cefex agar. The initial aliquot (10µL) was streaked (five passes per quadrant) onto the plating media and designated quadrant 1. Then, from that quadrant streaked into another quadrant and designated quadrant 2. This was repeated for designated quadrants 3 and 4. After incubation, the growth of non-Campylobacter colonies on campy-cefex was expressed as absolute growth index (AGI). Growth on all four quadrants (1 through 4) was nominated an AGI of 4; growth on quadrants 1-3 was an AGI of 3, and so forth. Standard dilutions (10E0 to 10E-5) were also prepared from the two enrichment broths and spread plated onto campy-cefex for enumeration of background microflora. A significant (P<0.05) difference in background microflora suppression in the two Campylobacter enrichment broths was observed using the FQS and enumeration procedure. The mean AGI was 0.17 and 2.84 for Tecra and Bolton broth, respectively. The mean log cfu/mL of background microflora was 0.39 and 4.69 for Tecra and Bolton broth, respectively. Relationship of AGI to log10 cfu/mL present within the broths were AGI 4 : 5.9, AGI 3 : 4.9, AGI 2 : 4.1, AGI 1 : 1.9, and AGI 0 : 0.2. A positive correlation between decreasing levels of background microflora within the broths were observed as the AGI declined. The FQS procedure can be used for rapid semi-quantitative estimation of an enrichment broth’s efficacy in suppressing background microflora without performing enumeration.