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Although cefoperazone is the most commonly used antibiotic in Campylobacter-selective media, the distribution of cefoperazone-resistant bacteria such as extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is increasing. Here we evaluated the potential of cephamycins for use as supplements to improve modified charcoal-cefoperazone-deoxycholate agar (mCCDA) by replacing cefoperazone with the same concentrations (32 mg/L) of cefotetan (modified charcoal-cefotetan-deoxycholate agar, mCCtDA) and cefoxitin (modified charcoal-cefoxitin-deoxycholate agar, mCCxDA). In chicken carcass rinse samples, the number of mCCDA plates detecting for Campylobacter (18/70, 26%) was significantly lower than that of mCCtDA (42/70, 60%) or mCCxDA plates (40/70, 57%). The number of mCCDA plates (70/70, 100%) that were contaminated with non-Campylobacter species was significantly higher than that of mCCtDA (20/70, 29%) or mCCxDA plates (21/70, 30%). The most common competing species identified using mCCDA was ESBL-producing E. coli, while Pseudomonas species frequently appeared on mCCtDA and mCCxDA.

The objective of this investigation was to determine the prevalence and characteristics of extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in ready-to-eat (RTE) vegetables. A total of 189 RTE vegetable samples (91 sprouts and 98 mixed salads) were collected in a retail market in South Korea from October 2012 to February 2013. The prevalence of ESBL-producing E. coli and K. pneumoniae was 10.1%. Of these, 94.7% were from the sprout samples. All isolates were resistant to cefotaxime, and many of the ESBL producers were also resistant to non-β-lactam antibiotics, including gentamicin, trimethoprim/sulfamethoxazole, and ciprofloxacin (73.7%, 63.2%, and 26.3% respectively). TEM-1, SHV-1, -2, -11, -12, -27, -28 and -61, and CTX-M-14, -15 and -55 β-lactamases were detected alone or in combination. The genetic platforms of all CTX-M producing isolates were ISEcp1-blaCTX-M-orf477 and ISEcp1-blaCTX-M-IS903 in CTX-M groups 1 and 9, respectively. To our knowledge, this is the first report of the prevalence and characterization of ESBL-producing E. coli and K. pneumoniae isolated from RTE vegetables. The results of this study indicate that RTE vegetables, sprouts, in particular, may play a role in spreading antimicrobial resistant bacteria and ESBL genes to humans.

We compared Bolton enrichment broth supplemented with antimicrobial triclosan (T-Bolton broth) and normal Bolton broth for the isolation of Campylobacter jejuni (C. jejuni) and Campylobacter coli (C. coli) from chicken carcass rinse. Whole chickens were rinsed with buffered peptone water prior to enrichment in normal Bolton broth or T-Bolton broth, followed by inoculation onto modified charcoal-cefoperazone-deoxycholate agar (mCCDA). Suspect colonies were confirmed by PCR. We observed a significantly higher number of C. jejuni or C. coli-positive samples in the T-Bolton broth (71.3%) than in the normal Bolton broth (27.5%) (p0.05). Furthermore, the number of contaminated mCCDA plates was lower after enrichment in T-Bolton broth (3.8%) than in the normal Bolton broth (75%) (p0.05), indicating that T-Bolton broth has higher selectivity. Finally, we identified extended-spectrum β-lactamase-producing Escherichia coli as the predominant competing flora in normal Bolton broth. In conclusion, the use of T-Bolton broth results in significant elimination of competing bacteria.