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Applied and Environmental Microbiology, June 2005, p. 3351-3354, Vol. 71, No. 6
0099-2240/05/$08.00+0 doi:10.1128/AEM.71.6.3351-3354.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Evaluation of Agar Plates for Direct Enumeration of Campylobacter spp. from Poultry Carcass Rinses
Omar A. Oyarzabal,1*
Kenneth S. Macklin,1
James M. Barbaree,2 and
Robert S. Miller1
Department of Poultry Science,1
Department of Biological Sciences, Auburn University, Auburn, Alabama 368492
Received 10 September 2004/
Accepted 12 December 2004

ABSTRACT
Campy-Cefex, a modification of Campy-Cefex, modified charcoal
cefoperazone deoxycholate (mCCDA), Karmali, CAMPY, and Campy-Line
agars were evaluated for their efficiency to isolate and enumerate
Campylobacter spp. from poultry carcass rinses. Campy-Cefex
and its modification produced the best results but were statistically
similar to CAMPY, mCCDA, and Karmali.

INTRODUCTION
Campylobacter spp. are found at a high prevalence in raw poultry
carcasses. Consequently, the mishandling of raw poultry and
the consumption of undercooked poultry are important risk factors
for human campylobacteriosis (
8,
20,
27). Studies in the United
States clearly show that more than 80% of commercial chicken
carcasses may be positive for
Campylobacter spp. (
16,
23), although
negative flocks can also be found. When
Campylobacter spp. are
present, their numbers per milliliter of carcass rinse can vary
from 1 to 3 log CFU. This range makes direct enumeration on
agar plates an alternative for the rapid identification of
Campylobacter spp. in carcass rinses.
Several agar plates have been developed or adapted for the identification of Campylobacter spp. from enriched poultry samples. However, few have been used for direct enumeration of Campylobacter spp. from poultry carcass rinses. Our research goals were to compare the efficacy of five plating media for direct enumeration of Campylobacter spp. from poultry carcass rinses and to determine if a modification of Campy-Cefex (mCampy-Cefex), a low-cost medium, was comparable to the original medium.
Twenty postchill carcass rinses were collected per visit from four processing plants. Each plant was visited three times (total, 240 samples; 20 samples/visit from three visits to four plants). Samples were collected using the carcass rinse method (3) and processed within 4 h of collection. Each carcass rinse was plated onto Campy-Cefex agar (26), mCampy-Cefex, modified charcoal cefoperazone deoxycholate agar (mCCDA) (6, 13), Campy-Line agar (17), Karmali agar (15), and CAMPY agar (Table 1). CAMPY agar is also referred to as CampyFDA (14) and is based on the medium developed by Skirrow (25) with the addition of amphotericin B (similar to Campy-BAP) and sodium pyruvate, sodium metabisulfite, and ferrous sulfate (Martin Blaser, New York University School of Medicine, personal communication). Modified Campy-Cefex agar was made by replacing cycloheximide with amphotericin B and laked horse blood with regular whole, lysed horse blood.
For each medium, two plates were each spread with 0.1 ml of
the carcass rinse and four plates were each spread with 0.25
ml of the rinse (
18,
19). Plates were incubated at 42°C
for 48 h in Glad Fresh Protect bags (The Glad Products Company,
Oakland, CA) flushed with a microaerophilic gas mixture (BOC
Gases, Hixson, TN) containing 10% CO
2, 5% O
2, and 85% N
2. Plates
without
Campylobacter growth after 48 h were incubated an additional
24 h to ensure maximum recovery of
Campylobacter spp. from samples
containing low numbers of cells. Presumptive identification
was based on colony morphology, phase contrast microscopy (morphology
and motility), and positive results from catalase and oxidase
tests (
24). Confirmation of isolates was done with a multiplex
PCR assay that identifies
Campylobacter jejuni and
Campylobacter coli (
9). Bacterial DNA was extracted using PrepMan Ultra (Applied
Biosystems, Foster City, CA). The PCR assay was followed as
described previously (
9) with the following changes: the mix
was premade (OmniMix HS; Cepheid, Sunnyvale, CA), and the annealing
temperature of the amplification cycles was dropped to 47°C.
Isolates that gave typical amplicons of
C. coli with PCR were
further confirmed using API Campy tests (bioMérieux.
Hazelwood, MO).
Each plant visit was considered a replicate for statistical purposes. Colony counts were converted to log10 CFU/ml and analyzed using the general linear model (GLM) procedure of SAS (SAS Release 8.02; SAS Institute, Inc., Cary, NC). Means were analyzed for differences by Tukey's honestly significant difference test (SAS). Additionally, percent positives were analyzed using GLM procedures. For all tests, a P value of
0.05 was considered significant.
The combined results from all six plating media showed that 63.3% (152) of all of the samples were positive for Campylobacter spp. Campy-Cefex and its modification, mCampy-Cefex, were the media that produced the best results, although there were no statistical differences compared to CAMPY, mCCDA, or Karmali medium. Campy-Line, however, had the lowest counts (P
0.05) compared to the other media (Table 2). The results obtained with Campy-Line may be explained by the large numbers of antimicrobial substances incorporated into this medium. Carcass rinses taken postchill have a relatively low level of microbial contamination; therefore, a highly selective medium may not be required.
The modification of Campy-Cefex agar described here performed
similarly to Campy-Cefex. This is not surprising, because the
only changes made involved the replacement of the antifungal
compound and the type of blood. The addition of blood and/or
other ingredients to neutralize the toxic effects of compounds
produced in the presence of oxygen and light is common in the
formulation of
Campylobacter media (
5). Lysed horse blood was
the best supplement out of 22 supplements screened by Bolton
and Coates (
4) for compounds that facilitate aerotolerance.
Amphotericin B has been used to replace cycloheximide in the
preparation of
Campylobacter enrichment broth (Bolton formula)
(
12). By replacing laked horse blood (Oxoid) with whole lysed
horse blood, the price of this medium was reduced considerably
(Table
3) without affecting its efficacy for
Campylobacter sp.
recovery. Usually, the supplements are the most expensive components
of the media (Table
3).
A combination of two or more media increased the likelihood
of detecting
Campylobacter-positive samples compared to a single
medium. However, no statistical differences were seen among
combinations. Some of the combinations are exemplified in Table
4. Considering performance, price, and preparation time, the
combination of mCampy-Cefex and mCCDA yielded the best results
for enumeration of
Campylobacter spp. from poultry carcass rinses.
CAMPY agar consistently exhibited more contaminants that interfered
with the recognition of
Campylobacter colonies. The most prevalent
contaminant was
Acinetobacter baumannii, which grew on all plates
except Campy-Line.
Acinetobacter lwoffi grew in a mixed culture
with
A. baumannii on Karmali.
Pseudomonas spp. and
Staphylococcus hominis grew on Campy-Cefex. The identification of the contaminants
was performed at the National Veterinary Services Laboratories
(Ames, IA).
Of the 152 positive samples, the multiplex PCR identified 143
as
C. jejuni, 3 as
C. coli, and 6 as containing both
C. jejuni and
C. coli. A total of 509 isolates were tested with the multiplex
PCR, with 496 (97%) identified as
C. jejuni and 13 (3%) identified
as
C. coli. C. coli isolates grew on mCampy-Cefex (1 isolate),
mCCDA (4 isolates), CAMPY (4 isolates) and Karmali (4 isolates).
One
C. coli isolate was found in one visit to plant D, and the
rest (12 isolates) were found in a single visit to plant B.
Seven samples taken from a single visit to plant B had both
C. jejuni and
C. coli growing in different media. Karmali and
mCCDA agars that contained a single antibacterial compound (cefoperazone,
selective against gram-positives) performed similarly to CAMPY,
a medium containing multiple antibacterial compounds (polymyxin
and trimethoprim, selective against gram negatives; and vancomycin
and novobiocin, selective against gram positives) for isolation
of
C. coli. Consequently, we believe that antimicrobial substances
contained in the media are not the only accountable factors
involved in the successful isolation of
C. coli. The discovery
that some strains of
C. coli are more susceptible to cephalothin
than
C. jejuni strains (
7,
22) prompted the replacement of cephalothin
by cefoperazone in isolation media (
10) to increase the probability
of isolating
C. coli. However, further studies are needed to
assess the most suitable medium for direct isolation of
C. coli from poultry carcass rinses.
Direct plating is a valuable technique to study Campylobacter spp. in poultry carcasses. Direct plating (18, 19) and a spiral-plating system (23) have been used with success to enumerate Campylobacter spp. in postchill carcass rinses. Dickins et al. (11) used concentration and filtration methods with direct plating, without enrichment, to study the genomic diversity of Campylobacters isolates from retail poultry carcasses. The results from those studies showed that 67% of the contaminated carcasses had more than one distinguishable pulsed-field gel electrophoresis pattern. In countries where commercial poultry flocks are colonized with a range of bacterial genotypes, such as Australia and the United States (21, 28), direct plating or filtration and direct plating may provide a useful technique to study the genomic diversity of Campylobacter spp. These results show that direct plating of carcass rinses is an inexpensive, easy-to-perform enumeration technique for Campylobacter spp. A well-validated enumeration technique is useful to assess the impact of intervention strategies aimed at reducing Campylobacter spp. in poultry meat, which is an important area of research for regulatory agencies and the poultry industry in the United States and the United Kingdom (1, 2).

ACKNOWLEDGMENTS
We thank Ann Cooper for her technical support.

FOOTNOTES
* Corresponding author. Mailing address: Department of Poultry Science, 260 Lem Morrison Drive, Auburn University, Auburn, AL 36849-5416. Phone: (334) 844-2608. Fax: (334) 844-2641. E-mail:
oyarzoa{at}auburn.edu.


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Applied and Environmental Microbiology, June 2005, p. 3351-3354, Vol. 71, No. 6
0099-2240/05/$08.00+0 doi:10.1128/AEM.71.6.3351-3354.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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