*3.1. Prevalence and Contamination Levels of Campylobacter*

Of 306 poultry samples, *Campylobacter* spp. were identified from 45 samples (14.7%, 15 chicken samples and 30 duck samples) after enrichment (qualitative), but the number of positive samples was higher in quantitative results than in qualitative samples (Table 3). Since other bacteria may also be enriched with *Campylobacter*, resulting in disturbing the identification, the prevalence rate was lower in qualitative results than in quantitative results. The mean contamination levels of the isolated *Campylobacter* spp. in chicken and duck samples were 22.0 ± 36.3 CFU/g and 366.1 ± 733.6 CFU/g, respectively (Table 3).

**Table 3.** Prevalence and contamination levels of *Campylobacter* in chicken and duck carcasses at wet markets in Korea during summer and winter.


Different upper letters (A, a, and b) in the same column indicate a difference (*p* < 0.05).

These results suggest that a quantitative method may be appropriate to investigate *Campylobacter* prevalence rather than a qualitative method, and duck samples have a higher contamination frequency and have higher levels of contamination significantly (*p* = 0.0210) than those in chicken samples in the Korean markets. *Campylobacter* was isolated regardless of the season; however, the contamination levels of *Campylobacter* were higher in the winter than in the summer. Of the 45 *Campylobacter* spp. isolates, 29 isolates were *C. jejuni* and 16 isolates were *C. coli.* In France, 372 of 425 chicken samples (87.5%) were *Campylobacter* positive, and their mean contamination level was 2.4 log CFU/g [35]. Also, Garin et al. [36] showed that *Campylobacter* spp. were detected from 491 of 750 chicken carcasses (65.5%) in five countries (Senegal, Cameroon, Madagascar, New Caledonia and Vietnam), and the mean value of contamination level was 3.2 log CFU/g. Additionally, Zhu et al. [37] analyzed 1587 chicken carcasses collected from seven provinces in China, and 716 carcasses (45.1%) were contaminated to Campylobacter, and the contamination level was 2.1 log CFU/g (median value). These studies indicate that *Campylobacter* contamination levels were similar among countries, however, the prevalence of *Campylobacter* can be considered low in wet markets in Korea. *Campylobacter* are microaerophilic bacteria. Thus, the bacterial cell counts can be gradually decreased under aerobic condition during distribution. Hence, long exposure time to aerobic condition during distribution to wet markets may induce low prevalence of *Campylobacter* in poultry in Korea.

#### *3.2. Antimicrobial Resistance Patterns*

Because antimicrobial resistance patterns were not different between *C. jejuni* and *C. coli*, the data were combined in Table 4. The *Campylobacter* isolates were resistant to nalidixic acid (93.3%), ciprofloxacin (91.1%), and tetracycline (71.1%) (Table 4). The isolates showed especially strong resistance to antibiotics such as nalidixic acid ciprofloxacin, tetracycline. However, *Campylobacter* isolates were sensitive to chloramphenicol (others), enrofloxacin (fluoroquinolones), erythromycin (macrolides), and amikacin (aminoglycosides) (Table 4). In Italy, *Campylobacter* isolates also showed high resistance rates to ciprofloxacin, tetracycline, and nalidixic acid [38]. Similarly, in the USA, the rate

of antimicrobial resistance to tetracycline was very high, at 99.1% in *Campylobacter* isolates from broiler carcasses, followed by resistance to nalidixic acid and ciprofloxacin [39].


**Table 4.** Percentage of susceptibility and resistance of seven antibiotics for *Campylobacter* isolates from poultry.

(1) A: Aminoglycosides, M: Macrolides; T: Tetracyclines; F: Fluoroquinolones; Q: Quinolones.

Raeisi et al. [40] showed that *Campylobacter* isolates from poultry were resistant to ciprofloxacin, tetracycline and nalidixic acid. Also, 100% of *C. jejuni* isolates (*n* = 31) from chicken in China had resistance to ciprofloxacin and nalidixic acid [41]. In Poland, *Campylobacter* isolates were susceptible to erythromycin and resistant to tetracycline and ciprofloxacin [42]. Taken together, we can conclude that both poultry and human isolates of *Campylobacter* spp. are generally resistant to quinolone and fluoroquinolone antibiotics, such as nalidixic acid and ciprofloxacin. This may be caused by the use of these antibiotics in veterinary and human medicine. Therefore, this result suggests that antibiotics used for humans should not be used in poultry.
