| C. jejuni is the most commonly reported bacterial cause of gastroenteritis in the worldwide. The incidence of C. jejuni has exponentially increased in recent years without properly explainations. Although it is generally recognized that there are many sources for C. jejuni infection, Campylobacteriosis is predominantly believed to be associated with the consumption of poultry meat. Therefore, the work of reducing the occurrence of C. jejuni in poultry meat is the major solution to control Campylobacteriosis. Furthermore, an emerging public health concern regarding Campylobacter is the issue of microbial food safety due to increasing numbers of antimicrobial-resistant isolates. The objectives of this study were to: (i) investigate the prevalence of C. jejuni and C. coli among diarrhea patients, healthy food workers at Yangzhou, food samples in the local retail markets, as well as pets at Yangzhou and in Shanghai; (ii) detect the antimicrobial susceptibility with K-B method recommended by Clinical and Laboratory Standard Institute in 2007; (iii) establish an inactivation kinetics model for C. jejuni on the chicken meat during the low-temperature storage.1. Prevalence of C. jejuni and C. coli among human, food and petBetween Janaury,2007 and December,2008, 2,758 of human feces samples from two different hospitals at Yangzhou; 2,771 of human feces samples from healthy food workers in Yangzhou CDC; 1,149 of food samples from local retail markets; 510 of pet feces samples from clinical department were collected for the isolation and identification of C. jejuni and C. coli. The results showed that there were 124 strains of C. jejuni and 11 strains of C. coli isolated from 2,758 human feces samples, the average positive rate was 4.50% and 0.40% respectively. Two hospitals showed no significant difference (p>0.05), while outpatients had higher prevalence rate than that of inpatients (p<0.01). The detection rate of infection during June to October had higher prevalence rate than that of other months (p<0.05). 4 strains of C. jejuni were isolated from 2,771 healthy human feces samples, the average positive rate was 0.14%. Diarrhea patients had higher prevalence rate than that of healthy food workers (p<0.01). 22 strains of C. jejuni and 14 strains of C. coli isolated from 1,149 food samples, the average positive rate was 1.91% and 1.22% respectively. 18 strains of C. jejuni and 6 strains of C. coli isolated from pet samples in clinical department, the average positive rate was 5.36% and 1.79% respectively. 3 strain of C. jejuni was isolated from 174 pet samples in cultivation industry base, the average positive rate was 1.75%. All results obtained from this study showed that C. jejuni is the most commonly reported bacterial cause of gastroenteritis. Pets and food is the vital sources for C. jejuni infection. And provided well foundation for the right evaluation and established viable measures of Campylobacter spp..2. Antibiotic resistance of C. jejuni and C. coli isolated from humans, food and petsTo detect the antimicrobial susceptibility of 133 C. jejuni strains as well as 21 C. coli strains isolated from different origins, the K-B method recommended by Clinical and Laboratory Standard Institute in 2007 was used.The 133 isolated C. jejuni from different origins were analyzed for susceptibility to 21 kinds of antibiotics, and the results showed that these isolated strains were highly sensitive to five kinds of antibiotics such as Cefotaxime 96.24%, Gentamicin 94.74%, Erythromycin 92.48%, Azithromycin 91.73% and Amoxicillin 85.71% were resistant to some frequently used medicines such as Cefoperazone 100%, Cephalexin 97.74%, Nalicixic acid 90.23%, Cefaclor 90.22%, Co-trimoxazole 87.97%,Ciprofloxacin 87.22%, Norfloxacin 85.71%, Ofloxacin 84.96%,Levofloxacin 84.36%, Tetracycline 82.70%. The percentage of isolates was 87.22% with resistance to 8 to 14 antimicrobials.Antibiotic resistance of 21 isolated C. coli strains were all evaluated by 21 kinds of antibiotics, and the results showed that these isolates were only sensitive to five kinds of antibiotics such as Cefotaxime 95.24%, Amoxicillin 85.72%, Erythromycin 85.72%, Azithromycin 90.48%, Clidamycin 80.95%, and were resistant to many frequently used antibiotics such as Cephalexin 100%, Ofloxacin 100%, Cefoperazone 100%, Levofloxacin 100%, Nalicixic acid 100%, Co-trimoxazole 100%, Doxycycline 100%, Ciprofloxacin 95.24%, Tetracycline 95.24%, Cefaclor 95.24%,Norfloxacin 90.48%, Oxytetracycline 85.72%, Ampicillin 80.95%. The percentage of isolates was 80.95% with resistance to 11, 14, 17 kinds of antimicrobials. The results of this study showed that the isolated C.jejuni strains were resistant to a number of common antibiotics used in clinic. For instance, Cefoperazon, Cephalexin, Cefaclor, Ofloxacin, Co-trimoxazole, Ciprofloxacin, Nalicixic acid, Levofloxacin, Oxytetracycline and so on. The multidrug resistance of isolated strains from local market was more severe than that of other isolated strains. C.jejuni strains isolated from human and pets shared the similar resistance features. It may be explained by the intimately contact between the two groups. In a word, antimicrobial resistance of the Campylobacter spp. became more and more diverse and complicated in our country. Monitoring systems for Campylobacter spp. are important for inspecting the trends of antimicrobial susceptibility and supporting development of public policies for better prevention and treatment of Campylobacteriosis.3. Inactivation kinetics model for C. jejuni on the chicken meat under low-temperature storageC. jejuni shows an increased susceptibility to low temperature. Freezing and chilling are effective interventions to reduce the occurrence of C. jejuni in poultry meat. The target of this study was to reveal the inactivation kinetics characteristics for three C. jejuni strains (ATCC33560, JR0706-2, ALM-80) on the chicken meat during the low-temperature storage, and provide useful data information for C. jejuni risk management. The survival rates of three C. jejuni strains inoculated into chicken meat samples were measured at -20℃,4℃and their survival curves were plotted respectively. The results showed that the survival cells decline by 3.16, 2.87, 3.14lgCFU/g respectively at -20℃during 55-day storage period. And the survival curves showed that in initial 20 days, the mean inactivation speeds were slow; In 25～45 days, rapid drop occurs, and during the followed period of 10 days, the mean inactivation speeds slowed down. Meanwhile, the survival cells declined by 3.47, 3.35, 3.51lgCFU/g respectively at 4℃during 10-day storage period. The mean inactivation speeds were 0.347lgCFU/d, 0.355lgCFU/d, 0.439lgCFU/d. There were some differences among inactivation speeds of different strains of C. jejuni, but there was no significant difference among the 3 strains (p>0.05). A data-fitting software was applied to fit the survival rates data. The results showed the established inactivation kinetics function produces good fitness for the 3 different strains at -20℃,4℃storage.Cold chain plays an important role in sales of chicken product. However, chicken meat may be beyond the protection of cold chain system, and the thraw-freezing process commonly occurs in practice. The effect of repeated thraw-freezing process was evaluated during the 8 times of repeated procedure. The results showed that the survival cells decline by 2.758logCFU/g. The survival curves showed that in the initial 5 times, the mean inactivation speed was fast, 0.432logCFU/time. In the last 3 times, inactivation speed slowed down with 0.07logCFU/time. Meanwhile, three"accidents"were set in the repeated thraw-freezing experiment to evaluate the function-loss of cold chain. C. jejuni strain ATCC33560 inoculated into chicken meat samples were measured at 3, 6 and 12 hours after the"accidents". In the first two thraw-freezing processes, the survival curve showed no obvious alternation at 0℃and 25℃, but rose up at 37℃. In the last thraw-freezing process, the survival curve descended at 0℃and 25℃, and remained stable at 37℃.The storage temperature can be strictly monitored if the inactivation kinetics characteristics for C. jejuni on the chicken meat are fully understood. Therefore, consumers will benefit from the fresh and safe chicken product. |
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