Prevalence,antimicrobial resistance and genetic diversity of Salmonella isolated from retail ready-to-eat foods in China

Salmonella is a leading cause of foodborne disease worldwide and ready-to-eat (RTE) foods are regarded as a major source of infection and outbreak. In recent years, the consumption of Chinese RTE foods has raised markedly with the pace of life increasing. However, the prevalence of Salmonella in these foods in China and its potential risk to public health has not been well determined and evaluated. This study was undertaken to investigate the prevalence of Salmonella in Chinese retail RTE food products and to determine serotype distribution, antimicrobial resistance, virulence, and genetic diversity of recovered Salmonella isolates. Out of the 539 RTE food products collected and tested from July 2011 to May 2014, 19 (3.5%) were positive for Salmonella. The contamination levels of Salmonella were mostly in the range of 0.3–10 most probable number (MPN)/g, with one sample exceeding 110 MPN/g. Among the 50 isolates identified, 37 isolates (74.0%) were resistant to at least one antimicrobial, while 21 isolates (42.0%) were resistant to more than three antimicrobials. High rates of resistance were observed for tetracycline (56.0%), ampicillin (38.0%), and streptomycin (34.0%). PCR analysis of 15 virulence genes showed that the avrA, ssaQ, mgtC, siiD, sopB, and bcfC genes were detected in all 50 isolates, whereas the genes located on plasmid and prophage varied significantly among the isolates. Ten distinct serovars were identified and S. Derby, S. Meleagridis, S. Enteritidis, and S. Senftenberg were the most prevalent serovars. A total of 11 sequence types by multilocus sequence typing and 20 profiles by pulsed-field gel electrophoresis were generated for the 20 selected isolates and the combination of these two methods presented a better knowledge of genetic diversity of Salmonella isolates. The study provided a systematical surveillance on prevalence of Salmonella in Chinese RTE foods and indicates its potential risk to public health.     

Prevalence,genetic diversity and antimicrobial resistance of Listeria monocytogenes isolated from ready-to-eat meat products in Nanjing,China

The prevalence of Listeria monocytogenes were investigated in a total of 628 ready-to-eat (RTE) meat products collected from different supermarkets and open-air markets in Nanjing, China. All isolates were further examined for the serogroup, virulence marker gene, genotype and antibiotic resistance. Thirty-three out of 628 samples (5.3%) were positive confirmed by the bacteriological method and PCR including 7.2% (17/236) of sauce pickled products, 4.2% (11/260) of cured products and 5.6% (5/90) of smoked and roasted products. Fifteen isolates (45.5%) belonged to serogroup 1/2a, 3a; 16 (48.5%) belonged to serogroup 1/2b, 3b and 2 (6.1%) belonged to serogroup 1/2c, 3c. All of them were positive for the virulence marker genes-iap, inlA, inlC, inlJ and lmo2672. Thirty-three isolates were grouped into 11 sequence types (STs) by multilocus sequence typing (MLST). The results of the antimicrobial susceptibility revealed that the isolates were sensitive to most of the antimicrobials used in the study except trimethoprim–sulfamethoxazole (100%), chloramphenicol (33.3%), ciprofloxacin (30.3%) and tetracycline (12.1%). Our findings indicated high prevalence of L. monocytogenes especially in sauce pickled products and from open-air markets, high prevalence of serogroups 1/2a, 3a and 1/2b, 3b that involved in the majority of foodborne outbreaks could be a public health concern. In addition, resistance of the isolates to the antimicrobials was also a potential health hazard for consumers.     

Prevalence and characterization of Yersinia enterocolitica isolated from retail foods in China

Yersinia enterocolitica is an important food-borne enteropathogen that causes gastrointestinal syndromes. The aims of this study were to identify Y. enterocolitica in food samples in China, and to assess the pathogenic potential and antimicrobial resistance, and to characterize the genotypes of the isolates. From July 2011 to May 2014, a total of 2320 food samples were obtained, and 47 (2.03%) were found positive for Y. enterocolitica, while 706 retail-level ready-to-eat products and 249 vegetable samples were negative. A total of 58 Y. enterocolitica strains were isolated. All isolates belonged to biotype 1A, and the primary serotype was O:8. All strains lacked the ail, virF, ystA, and ystC virulence genes, but harbored the ystB, fepD, ymoA, fes, and sat genes. All 58 strains were sensitive to kanamycin and sulfonamide, but were resistant to two or more antibiotics. Most of the strains expressed the β-lactamase genes; the presence of blaA and blaB was detected in 97% and 100% of isolates, respectively. Many strains were resistant to trimethoprim/sulfamethoxazole (79.3%), ampicillin (91.4%), and cephalothin (91.4%). The 58 strains were grouped into three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) at a similarity coefficient of 70%, and each cluster was largely organized by geographical region. This study provides a valuable accounting of the prevalence of Y. enterocolitica from a nationwide survey of foods in China, and highlights the seasonal effects of Y. enterocolitica prevalence in foods in China for the first time.     

Prevalence and characterization of Listeria monocytogenes isolated from retail-level ready-to-eat foods in South China

Listeria monocytogenes is an important food-borne pathogen causing meningitis, meningoencephalitis and abortion. To assess the potential risk to consumer health, the presence of L. monocytogenes was investigated using qualitative and quantitative methods. Ten (6.33%) of 158 retail RTE food samples were positive for L. monocytogenes and the contamination levels were less than 10 MPN/g,while none of 65 dairy products was positive for L. monocytogenes. The 37 strains were grouped into five clusters and two singletons, five clusters and two singletons, and three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and RAPD fingerprint respectively, at similarity coefficient of 80%. The susceptibility test showed that 83.8% were susceptible to 15 antimicrobials; two were penicillin-resistant, and one was multidrug-resistant to kanamycin, tetracycline, sulfamethoxazole, rifampin, gentamycin, penicillin, and ampicillin. Virulent L. monocytogenes that possess partial antimicrobial resistance, and serotypes frequently associated with listeriosis were recovered from RTE foods. Consumers may, therefore, be exposed to potential risks of L. monocytogenes infection in South China. This study contributed to the prevalence and contamination levels of L. monocytogenes in RTE foods in South China for the first time, providing baseline information for Chinese regulatory authorities to formulate a regulatory framework for controlling L. monocytogenes to improve the microbiological safety of RTE foods.     

Prevalence and characterization of Listeria monocytogenes isolated from retail food in Henan,China

Listeria monocytogenes, an important foodborne pathogen, is the causal agent of listeriosis. In this study, a total of 954 food samples originating from raw meat, cooked meat products, seafood, and vegetables purchased from supermarkets and open-air markets in Henan province, China, were analyzed for the presence of L. monocytogenes. All L. monocytogenes isolates were subjected to serotyping, pulsed-field gel electrophoresis (PFGE), and antimicrobial resistance. The overall percentage of L. monocytogenes prevalence was 6.2% (n = 59) with the highest rate of 7.4% for cooked meat products followed by raw meat (6.7%). The isolates belonged to five serotypes (1/2a, 1/2b, 1/2c, 4b, and 4c), with serotype 1/2a being predominant (55.9%). PFGE revealed a low genetic diversity among the isolates, irrespective of their sources, suggesting that dominant clones are widespread in different food products in Henan. Resistance to cefotaxime (30.5%) and ciprofloxacin (13.5%) was most often, whereas resistance to tetracycline, trimethoprim/sulfamethoxazole, and erythromycin was observed less frequently. The presence of L. monocytogenes in food products and antimicrobial resistance among the isolates represents a potential public health risk. Our results indicate that effective hygienic measures and bacteriological controls are necessary in China to reduce the contamination of retail food samples by L. monocytogenes.     

Listeria monocytogenes in ready-to-eat foods in Italy: Prevalence of contamination at retail and characterisation of strains from meat products and cheese

In the framework of a European Union (EU) Coordinated Monitoring Programme, different types of ready-to eat (RTE) products, including soft and semi-soft cheese (n = 398) and cooked meat products (n = 403), were collected at retail in Italy and tested for detection and enumeration of Listeria monocytogenes. An Integrative Survey of 2696 samples, including soft and semi-soft cheese (n = 894) and cooked meat products (n = 1802) was carried out to have statistically representative results at the national level. Considering the results obtained both from the EU and the national Integrative Survey, prevalence of contamination of meat products was 1.66% (95% CL: 1.02–2.73%) at the arrival of the samples at the laboratory and 1.92% (95% CL: 1.31%–2.82%) at the end of shelf-life. Spalla cotta was the most frequently contaminated meat product. Prevalence of contamination in cheese was 2.13% (95% CL: 1.37%–3.3%) at the arrival at the laboratory and 1.01% (95% CL: 0.41%–2.55%) at the end of shelf-life. To get information about differences between cheese rinds and pastes, these two parts were separately analysed in the Integrative Survey samples. L. monocytogenes was detected in 4.02% (95% CL: 2.60%–6.19%) of cheese rinds (n = 473), whereas only the 0.34% (95% CL: 0.12%–0.98%) of cheese pastes (n = 894) were contaminated. This difference was statistically significant (χ² = 10.026, P < 0.05). Gorgonzola and Taleggio were the most frequently contaminated cheeses. Non-compliance with EU official criteria (100 CFU/g) was reported in 0.55% of meat products at arrival at the laboratory, in 0.46% at the end of shelf-life, and in 1.9% of cheese rinds. PFGE showed that cheese rinds could have been the origin of the few pastes' contamination, highlighting genetic similarity between isolates found in these two cheese components. Genetic subtyping also showed the presence of different pulsotypes, usually belonging to different clusters, in isolates from different food types. The presence of some pulsotypes predominantly prevalent over the others, in products from the same manufacturer, could suggest environmental strains as the main source of contamination.     

Prevalence and antimicrobial resistance of Listeria monocytogenes and Salmonella strains isolated in ready-to-eat foods in Eastern Spain

Antimicrobial resistance is a major global public health concern and a food safety issue considered in the framework of Horizon 2020. Bearing this in mind, the current study determined the prevalence of Listeria monocytogenes and Salmonella strains isolated in ready-to-eat food sampled in industry and retail between 2006 and 2012 by the Official Food Control Services of the Valencian administration (Spain). The presence of L. monocytogenes was analysed in a total of 2864 samples including pasteurized cheese (624); cooked ham (487); dried pork sausages (192); ice cream (758) and smoked salmon (803). The presence of Salmonella was analysed in a total of 1264 samples: pasteurized cheese (289); cooked ham (316); dried pork sausages (78); ice cream (376) and smoked salmon (205). The results showed that L. monocytogenes was present in 3.8% of the samples, being most common in smoked salmon. Salmonella was not found in any of the products studied with the exception of 7 out 78 samples of dried pork sausage. Both L. monocytogenes and Salmonella showed resistance to 4 antimicrobials (ampicillin, cephalothin, tetracycline and trimethoprim-sulfamethoxazole). Moreover, the former was resistant to amikacin, ciprofloxacin, erythromycin and vancomycin while the later showed resistance to amoxicillin-clavulanate and chloramphenicol. Furthermore, multi-resistance was found for both microorganisms.     

Occurrence and antibiotic resistance profiles of Listeria monocytogenes isolated from seafood products and market and processing environments in Iran

This study was designed to determine the occurrence of Listeria monocytogenes in popular seafood products and their market and processing environments. The frequency of L. monocytogenes contamination was found to be 4.83% in raw and 14.5% in RTE seafood products. In raw products, the prevalence of L. monocytogenes was significantly higher (P < 0.05) in freshwater fish (11.4%) than in seawater fish (1.80%) and shrimp (1.69%). Cold-smoked fish had the highest frequency of L. monocytogenes contamination among the RTE products. The microbial load of L. monocytogenes in seafood products was in the range of <0.3 to 1100 MPN/g; and did not exceed 100 MPN/g in most of the examined samples. The incidence of L. monocytogenes in environmental and personnel samples was 17.1% and 16.2% in markets, and 21.3% and 18.2% in processing plants, respectively. It was found that contamination of processed fish fillets and shrimp flesh with L. monocytogenes mainly originated from the processing environments, rather than the raw materials. In addition, the implemented cleaning procedures were insufficient to eliminate L. monocytogenes from the market and processing environments. Serological examinations revealed that serotype 1/2a (45.7%) was the predominant serotype of L. monocytogenes followed by 4b (40.3%), 1/2c (5.39%), 1/2b (4.68%), and 4c (3.96%). Regarding seasonal variability, 1/2a was the dominant serotype during warm seasons, whereas 4b was the most prevalent serotype during cold seasons. The isolates of L. monocytogenes were highly resistant to penicillin, ampicillin, tetracycline, and vancomycin. The results indicate that prevalence of L. monocytogenes serotypes 1/2a and 4b, which are associated with foodborne outbreaks of human listeriosis; and their resistance to commonly used antibiotics for treatment of human listeriosis could be a public health concern.     

Genotypic characterization and antimicrobial resistance of Listeria monocytogenes from ready-to-eat foods

Listeria monocytogenes is an important foodborne pathogen. The aims of this study were to determine genetic relatedness of L. monocytogenes isolated from ready-to-eat (RTE) foods in Malaysia. L. monocytogenes isolates from RTE foods were characterized by multiplex-PCR serotyping, REP-PCR, BOX-PCR, RAPD, PFGE, virulotyping and antibiotyping. Of the 32 L. monocytogenes isolates analyzed, 21 (65.6%) were assigned to serogroup “1/2a, 3a”, seven (21.9%) serogroup “1/2c, 3c”, and four (12.5%) serogroup “4b, 4d, 4e”. All the L. monocytogenes harbored inlA, inlB, inlC and inlJ virulence genes. More than half (53%) L. monocytogenes isolates were resistant to penicillin G, followed by tetracycline (15.6%), amoxicillin-clavulanic acid (12.5%), vancomycin (9.4%) erythromycin (6.3%), clindamycin, streptomycin, kanamycin, and chloramphenicol (each 3.1%). REP-PCR, BOX-PCR, RAPD and PFGE generated 28 (D = 0.992), 31 (D = 0.998), 32 (D = 1), and 20 (D = 0.916) patterns, respectively. These results indicate that L. monocytogenes isolates from RTE food were heterogeneous. There was no correlation between antibiograms and serogroups or pulsotypes or PCR-typing and/or sources of isolates. Since different subtyping methods often give different discriminatory powers, the use of more than one subtyping approach is necessary in providing a more accurate picture of the genetic diversity of L. monocytogenes. In conclusion, L. monocytogenes isolates from RTE possess the internalin genes and are genetically diverse. Furthermore, the occurrence of resistant isolates belonging to epidemiologically important serogroups “1/2a, 3a” and “4b, 4d, 4e” in RTE foods is a matter of public health concern.     

Prevalence and antibiotic susceptibility of Listeria spp. isolated from raw meat and retail foods

Listeria and particularly Listeria monocytogenes is an important foodborne pathogen that can cause listeriosis with flu-like symptoms in healthy people, and severe complications in immunocompromised subjects, children, pregnant women and the elderly. A research survey was conducted to check the presence of Listeria spp. in raw meat and retail products and to analyse their antibiotic resistances. Total prevalence was 11.7%: in raw meat was 21.4%; in ham it was 5.2%; in fresh soft cheese it was 3.49%; in sandwiches it was 5.88%, while we found no isolates in smoked salmon and only two in ready salads (1.23%). The highest percentage of prevalence of L. monocytogenes was found in samples of ham (37.5%), lower percentages were in sandwiches (25.0%), in raw meat samples (23.6%), in fresh soft cheeses (20.0%), while ready salads and smoked salmons were not contaminated. The susceptibility of 168 strains of Listeria spp. was determined by disk diffusion method: we found 51 (30.4%) strains resistant to three or more antibiotics. All isolated strains, except one, are susceptible or at least to one of the first choice antibiotics (ampicillin and gentamycin) or to trimethoprim–sulfamethoxazole used as antibiotic of second choice in the treatment of human listeriosis. Strains isolated from ready-to-eat food show high level of resistance to ampicillin, gentamycin and meticillin. Meticillin is used normally, in treatment of Enterococcus spp. human infection; L. monocytogenes can transfer antibiotic resistance genes from plasmids and transposons to Enterococcus spp. in vitro and in vivo causing an increase of these bacteria resistant to meticillin. L. monocytogenes, in the last decades, is becoming resistant to a lot of antibiotics, a continued surveillance on its incidence on raw foods and on emerging resistances are important to identify food that can represent a risk of infection for the population, particularly for immunocompromised, children, pregnant women and the elderly to ensure effective treatment of human listeriosis with effective antibiotics.     

Prevalence of Listeria spp. and antibiotic susceptibility of Listeria monocytogenes isolated from raw chicken and ready-to-eat chicken products in Jordan

Listeria monocytogenes is the causal agent of listeriosis, a disease that can be serious and is often fatal in susceptible individuals. The objective of the study was to determine the prevalence of Listeria spp. in raw chicken and ready-to-eat (RTE) chicken products in Amman, Jordan and the antimicrobial resistance of L. monocytogenes isolates. A total of 280 raw chicken and RTE chicken products (chicken-shawirma, chicken-burger, chicken-sausage and mortadella) were collected from Amman abattoir and local retail markets in Amman city. Listeria spp. were isolated by the conventional International Organization for Standardization (ISO) method and L. monocytogenes identified by biochemical and Polymerase Chain Reaction (PCR). Results of conventional method showed that out of total 280 samples, 141 (50%) were found to be contaminated with Listeria spp. [L. monocytogenes (18.2%), Listeria ivanovi (26.1%), Listeria grayi (3.5%), Listeria seeligeri (1.8), Listeria welshimeri (0.7%)]. The PCR confirmed all L. monocytogenes isolates (51 isolates: 15 from raw dressed broiler chicken, 23 from chicken-burger, 9 from chicken-sausage, and 4 from chicken-shawirma). Five of the tested L. monocytogenes isolates were resistance to two antibiotics (tilimicosin and tetracycline) among the ten tested antibiotics as determined by microbroth dilution method. The results presented in this study indicate the potential risk of contamination of RTE chicken products with L. monocytogenes.     

Prevalence,genetic diversity and antimicrobial susceptibility of Listeria monocytogenes isolated from open-air food markets in Greece

A total of 210 food samples originating from milk products, ready-to-eat salads, raw meat and raw meat products purchased in ten open-air market places in Thessaloniki, Greece, were analyzed for the presence of Listeria monocytogenes. Thirty (14.3%) contained L. monocytogenes with the highest prevalence in raw meat (27.5%), raw meat products (18%) and cheese (8%). The strains were susceptible to 16 antimicrobials as determined by microbroth dilution, except one strain which displayed resistance to tetracycline (MIC > 32 μg/ml). This strain carried the tetracycline resistance gene tet(M). Pulsed-field gel electrophoresis (PFGE) revealed a low genetic diversity among the isolates, irrespective of their origin. This suggests that dominant L. monocytogenes clones are widespread in different food product types in open-air food markets in Greece. The high prevalence of L. monocytogenes in these products indicates that appropriate hygienic measures and periodic bacteriological controls are also necessary in open-air food markets to reduce contamination with food-borne pathogens. Greek specialties made with raw meat and raw milk may contain L. monocytogenes and should not be consumed by persons at risk.     

Toxigenicity and genetic diversity of Staphylococcus aureus isolated from Vietnamese ready-to-eat foods

The aim of this study was to investigate the prevalence and genetic diversity of Staphylococcus aureus and staphylococcal enterotoxins (SEs) in ready-to-eat foods marketed in Hanoi, Vietnam. Out of 212 samples tested, 45 were contaminated with this bacterium and 18 contained strains having classical SEs. Among different food products, the bacterial occurrence ranged between 12.5% and 35.4% and milk samples had the highest prevalence. The production of SEs varied according to the food types and 26 different ribotype patterns were observed among the 45 strains. Our dendogram analysis showed the existence of many clones without clear-cut affiliation to any particular food type indicating both diverse primary and secondary contamination sources. The SEs also occurred in a wide variety of genetically different S. aureus strains which might facilitate the bacterium with better ecological fitness to cause epidemics. It can be concluded that Vietnamese ready-to-eat foods pose a high risk of contamination by toxigenic S. aureus population urging the need of implementing proper hygienic practices.     

Prevalence,acquired antibiotic resistance and bacteriocin production of Enterococcus spp. isolated from tunisian fermented food products

In this study, a total of 100 fermented food products including dairy (Lben, Rayeb, Rigouta, and Jben) olive and vegetable products, harvested in Northwestern Tunisia, were investigated for the presence of Enterococcus spp. Our results showed high levels of contamination with Enterococcus spp., identified according to standard bacteriological, biochemical and phenotypic criteria. 143 isolates were recovered; E. faecium (46.15%) was the predominant species, followed by E. faecalis (27.27%), E. casseliflavus (12.58%), E. durans (8.39%) and E. mundtii (5.59%). None of the isolates showed acquired resistance againts clinically relevant drugs used for enterococcal infections treatment in human medicins, and no haemolytic activity was demonstrated. Furthermore, over 50% of the isolates within each species exhibited antilisterial bacteriocin production. Further data are needed to enhance understanding of bacteriocin production of enterococci in fermented food products as well as the potential risks to quality and safety, including possible transmission of antibiotic resistant organisms to human consumers.     

Listeria monocytogenes in ready-to-eat vacuum and modified atmosphere packaged meat and fish products of Estonian origin at retail level

The prevalence, counts and genetic diversity of Listeria monocytogenes in ready-to-eat (RTE) vacuum and modified atmosphere packaged meat and fish products was studied in Estonia. Within two consecutive years 370 RTE food samples were collected at retail level from which 11% were found to be positive for L. monocytogenes. Contamination was higher among RTE fish products (17%) than in RTE meat products (6%). Generally, the counts of L. monocytogenes in positive products remained under ten colony forming units (CFU) per gram of product. Only 1.6% of the RTE meat and fish products contained L. monocytogenes in range of 10–100 CFU/g and 0.3% more than 100 CFU/g at the end of shelf-life. The food category containing highest L. monocytogenes prevalence was RTE lightly salted fish products with the prevalence of 32%. Only one (0.3%) RTE food sample exceeded the 100 CFU/g food safety criterion set out in the EU Regulation 2073/2005. Pulsed-field gel electrophoresis (PFGE) characterization of the isolates showed an overall similarity higher than 70%, and nine clusters based on 100% similarity were revealed. PFGE genotyping revealed that the few predominant pulsotypes were associated with particular food plants.     

Prevalence,enumeration, and characterization of Salmonella isolated from aquatic food products from retail markets in China

This study aimed to estimate the extent and level of Salmonella contamination of aquatic food products in China, and to determine serotype, virulotype, and the antimicrobial resistance profiles of recovered Salmonella isolates. Out of 554 samples collected from July 2011 to May 2014, 86 (15.5%) tested positive for Salmonella. The highest contamination rate occurred in oysters (23.1%, 6/26), followed by freshwater fish (18.6%, 43/231), shrimp (13.0%, 13/100), and saltwater fish (12.2%, 24/197). The contamination levels generally corresponded to a most probable number (MPN)/g of 0.3–10, although one sample exceeded 110 MPN/g. Among the 103 isolates, S. Typhimurium, S. Wandsworth, S. Thompson, and S. Derby were the most prevalent serovars. Sixty-eight isolates (66.0%) were resistant to at least one antimicrobial, and 35 (34.0%) were resistant to more than three. High rates of resistance were observed for tetracycline (35.9%), ampicillin (28.2%), nalidixic acid (26.2%), trimethoprim-sulfamethoxazole (25.2%), chloramphenicol (20.4%) and streptomycin (18.4%). Of note, S. Thompson isolates exhibited resistance to multiple extended-spectrum cephalosporins, ciprofloxacin, and other antimicrobials. PCR analysis of 15 virulence genes showed that ssaQ, mgtC, siiD, sopB, and bcfC were present in all 103 isolates, whereas the remaining loci were variably distributed. S. Typhimurium, S. Enteritidis, and S. Weltevreden isolates exhibited a wider range of pathogenicity determinants compared with the other strains. Our study provides a comprehensive surveillance on prevalence of Salmonella in aquatic food products from China and indicates its potential risk to public health. These data are valuable for epidemiological studies, risk management, and public health strategies.     

Prevalence,antimicrobial resistance profiling and genetic diversity of Campylobacter jejuni and Campylobacter coli isolated from broilers at slaughter in China

A total of 651 samples from broiler cecal samples, carcasses, carcass parts collected at the slaughterhouse level in Sichuan Province of China were examined for the occurrence of Campylobacter jejuni and Campylobacter coli. After confirmed by species-specific multiplex PCR, the recovered isolates were examined for resistance to antimicrobials using an agar dilution method and investigated for the mutation of gyrA, tetO gene and V domain of 23S rRNA as well as the presence of class 1 integron and the associated gene cassettes. In addition, the genotype relatedness of the isolates was determined by pulsed-field gel electrophoresis (PFGE) profiling. The prevalence of Campylobacter was 56.1% in cecal samples, 31.0% in carcasses and 17.0% in carcass parts, respectively. Among them, C. jejuni accounted for 24.6% and C. coli occupied 20.0% of the samples. The strains of C. jejuni were most frequently resistant to ciprofloxacin (88.1%), followed by resistance to tetracycline (79.4%) and levofloxacin (78.1%). Most of the C. coli isolates were resistant to ciprofloxacin (100%), tetracycline (98.5%), levofloxacin (98.5%), clindamycin (98.5%) and erythromycin (93.9%). Antimicrobial resistance profiling showed that 93.7% of campylobacters were multidrug resistant (MDR) strains. Moreover, class 1 integrons were detected in 98.6% of MDR campylobacters, among which 98.7% were positive for C. jejuni and 98.5% for C. coli. Three kinds of gene cassettes-associated amplicons were identified and the amplicons profile of 1000–750–500–250 bp was the predominant pattern linked to the aminoglycoside resistance gene of aadA2. The presence of mutation in gyrA, tetO and 23S rRNA between C. jejuni and C. coli varied from 89.7% to 97.3%, 96.6% to 94.1%, and 95.0% to 96.7%, respectively. Finally, the results of PFGE indicated that, 33 PFGE profiles were generated among 78 isolates of C. jejuni and the similarity level ranged from 42.1% to 99.1%. By contrast, 15 PFGE patterns were produced among 68 C. coli isolates sharing a similarity level of 54.0%–99.7%. Comparison of the PFGE and antimicrobial resistance profiles of the isolates reflected the high genetic diversity of Campylobacter tested. A poor correlation among the antimicrobial resistance patterns, resistance determinants and PFGE genotypes was observed in C. jejuni. Our study showed that there were several points of cross-contamination during broiler slaughter, and a high diversity of PFGE types in the Campylobacter isolates with high resistances to ciprofloxacin and tetracycline.     

Prevalence and antimicrobial resistance of Campylobacter species isolated from the avian eggs

Campylobacter is one of the most important food borne pathogens that cause bacterial gastroenteritis worldwide. The most commonly isolated species in humans are Campylobacter jejuni (C. jejuni) and Campylobacter coli. The emergence of antimicrobial resistance in Campylobacter spp. has been a growing public health concern globally. Information about antimicrobial resistance of Campylobacter at different levels of production is important for the development of control strategies for this pathogen. This study was conducted to determine the prevalence and antimicrobial resistance of Campylobacter spp. isolated from different eggs from different avian species in Iran. A total of 440 egg samples were collected from different avian and analyzed for the presence of Campylobacter spp. in eggshell and eggs content under sterile conditions using Campylobacter selective agar base and the species were identified by biochemical tests. The suspected colonies were subjected to PCR assay for final confirmation as Campylobacter spp., and identification of C. jejuni or Campylobacter coli. Antimicrobial susceptibility testing was performed by the Kirby–Bauer disk diffusion method using Mueller Hinton agar. Campylobacters were detected in a total of 7 out of 100 (7%) eggshell of chicken samples and in 3 out of 60 (5%) eggshell of duck samples. In addition, Campylobacter spp. were also detected in 3.3%, 2.5%, 4.2%, 5% and 3.8 of the eggshell of goose, ostrich, partridge, quail and turkey samples, respectively. The overall prevalence rate of Campylobacter species from different avian eggs was found to be 7.7% (34/440). Among different avian egg samples, Campylobacter jejuni was more frequently isolated 28 (n = 28, 6.3%) than C. coli 6 (n = 6, 1.3%). In addition, the prevalence of C. jejuni was highest in summer and lowest in autumn. In this study Campylobacter spp. showed significant difference in resistance pattern with tetracycline and ciprofloxacin but gentamicin resistance was not found in both C. coli and C. jejuni isolates. Therefore, gentamicin is safe and effective drugs for the treatment of human campylobacteriosis if avian egg is considered as the source of infection.     

Genotypic characterization of Listeria monocytogenes isolated from milk and ready-to-eat indigenous milk products

Listeria monocytogenes is a food borne pathogen associated with severe diseases in humans and animals. We present the genotypic analysis of 18 L. monocytogenes isolates recovered from milk and ready-to-eat (RTE) indigenous milk products by multiplex-PCR, allowing serovar predictions, and by random amplification of polymorphic DNA (RAPD) assays. Multiplex-PCR serotyping assay revealed 72.2% (13/18) strains belonging to serovar group 4b, 4d, 4e, 22.2% (4/18) to serovar group 1/2b, 3b while 5.5% (1/18) to serovar group 1/2a, 3a. RAPD analysis revealed five RAPD profiles from eight L. monocytogenes strains from milk, and seven RAPD profiles from ten strains from milk products. Though RAPD analysis allowed discrimination among isolates of the same serotype and among isolates from the same sampling areas or those isolated from different areas, our results suggests that most of the L. monocytogenes isolates were indeed sporadically harboured by single food items. Thus, RAPD together with multiplex-PCR serotyping allowed rapid discrimination of L. monocytogenes strains and therefore could serve as an economical tool for typing L. monocytogenes strains. In addition, the predominance of L. monocytogenes serotype 4b in our study is of public health concern, as this serotype has been most frequently associated with human listeriosis.     

Comparison of Vibrio parahaemolyticus isolates from aquatic products and clinical by antibiotic susceptibility,virulence, and molecular characterisation

Vibrio parahaemolyticus is a common foodborne pathogen found in aquatic products and represents a major threat to human health worldwide. Though not all this bacteria were harmful to human beings, the pathogenic V. parahaemolyticus always harbors either tdh (the thermostable direct hemolysin) or trh (TDH-related hemolysin) gene, or both. Additionally, the extensive use of antibiotics has been shown to be a contributing factor to the increasing incidence of antimicrobial-resistant strains. In this study, thirty-one clinical isolates were examined and compared with 95 (38.0%) aquatic product isolates (fishes, n = 28; shrimps, n = 67) collected from 250 samples in Guangdong, China. All isolates were studied by antibiotic susceptibility analysis, tdh and trh genes detection, serotyping and molecular typing (ERIC-PCR). The antimicrobial resistance patterns of these aquatic product isolates to 12 antimicrobial agents revealed that most of the isolates were resistant to streptomycin (90.53%). The isolates were also resistant to follow by ampicillin (33.68%) and cephalothin (30.53%). For clinical isolates, they were resistant to streptomycin (93.55%), ampicillin (87.10%), and cefazolin (64.52%). All isolates showed no resistance to azitromycin, chloramphenicol, ciprofloxacin, or nalidixic acid. The clinical isolates were positive for tdh (100%) and trh gene (77.42%), with ratios of only 2.11% and 28.42%, respectively in the aquatic product isolates. Serotyping detected shown that the isolates contained O1, O2, O3, O4, and O11, with the O3 serotype being the most common among the clinical isolates (48.39%), while the O2 (41.05%) makes the maximum proportion on aquatic product isolates. ERIC-PCR results demonstrated the isolates (n = 126) were classified into eight clusters, revealing genetic variation and relatedness between clinical and aquatic product isolates. This study provided a foundation for understanding the distinction between aquatic product and clinical isolates and yielded basic information for achieving food safety through control of V. parahaemolyticus contamination.