Prevalence and antimicrobial susceptibility of Vibrio species related to food safety isolated from shrimp cultured at inland ponds in Thailand

Inland farming of marine shrimp species is a relatively recent development, in response to increasing demand for the products. This study aimed to investigate the prevalence and antimicrobial resistance of potentially pathogenic Vibrio species in shrimps cultured at inland ponds with low salinity in Thailand. Of 16 shrimp samples (white-leg shrimps and black-tiger shrimps) from ponds with water temperatures from 29 to 32 °C, and salinities from 1 to 5 parts per trillion, 15 contained Vibrio cholerae (densities: 62–252,000 MPN/g). Vibrio parahaemolyticus was present in six samples (370–6,300,000 MPN/g), and Vibrio vulnificus was present in two samples (16–1300 MPN/g). V. parahaemolyticus has higher affinity for non-native white-leg shrimp than for native black-tiger shrimp. The minimum inhibitory concentrations were then measured for 12 common antimicrobial agents. Resistance to ampicillin and oxytetracycline (8% and 2% of the isolates) was documented in V. cholerae isolates, resistance to ampicillin and oxytetracycline (72% and 3%) was found in V. parahaemolyticus isolates, and resistance to nalidixic acid (20%) was detected in V. vulnificus isolates. β-lactamase and tetracycline resistance genes were detected in the resistant Vibrio isolates. The oxytetracycline-resistance phenotype was eliminated by plasmid curing, suggesting that the resistance was related to R-plasmids. Our results show that shrimps cultured even in low salinity ponds are potentially contaminated with pathogenic Vibrio species, and that shrimp are a vehicle for transfer of species with antimicrobial resistance genes to the public.     

Serovar diversity and antimicrobial resistance of non-typhoidal Salmonella enterica recovered from retail chicken carcasses for sale in different regions of China

Non-typhoidal Salmonella enterica (NTS), the etiological agents in foodborne salmonellosis, is a major public health concern. This study describes the serovar diversity and antimicrobial resistance phenotypes identified in NTS isolates from retail whole chicken carcasses across six provinces of China. From food samples tested, a total of 2210 Salmonella isolates were recovered and these were serotyped by conventional and molecular serotyping methods and tested for their susceptibility to a panel of antimicrobial compounds. Sixteen serogroups and 52 serovars were identified, with serogroups B, D1 and C1 common among Enteritidis, Indiana and Infantis isolates. The serovar distribution varied both geographically and seasonally. Most (80.18%) of these isolates were found to be resistant to at least one antimicrobial compound and 54.6% were multi-drug resistant (MDR). Resistance to nalidixic acid (NAL) was common (70.6%) among the 11 tested compounds and no isolate was found to be resistant to carbapenems. There were 119 antimicrobial resistance profiles identified in the study collection. Two-hundred eighty-four isolates, including 99 Salmonella enterica serovar Indiana (S. Indiana), were resistant to seven or eight classes of antimicrobial compound. One-hundred eighty-three S. Indiana isolates were found to be co-resistant to ciprofloxacin and cefotaxime and 179 of these were confirmed as extended-spectrum β-lactamase producers. These data begin to describe the serovar diversity and antimicrobial resistance of NTS isolates recovered from retail chicken carcasses in parts of China. The findings highlight the emergence of ciprofloxacin and cefotaxime co-resistant S. Indiana, a feature displaying serious antimicrobial resistance but not commonly reported in human infections of Salmonella until recently. The food safety implications of these findings are discussed.     

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 susceptibility of Vibrio parahaemolyticus isolated from retail shellfish in Shanghai

Vibrio parahaemolyticus is a marine and estuarine bacterium that poses the greatest threat to human health worldwide. It has been the leading bacterial cause of seafood-borne illness. This study investigated the prevalence and drug resistance of V. parahaemolyticus isolated from retail shellfish in Shanghai. A total of 140 shellfish samples were collected from February 2014 to February 2015. The occurrence of V. parahaemolyticus in shellfish was 34.3%, which has increased compared to previous reports. In addition, discernible differences of total presumptive V. parahaemolyticus counts (TPVPC) were also observed in shellfish between market A and B. The results from PCR assays indicated that thermostable direct hemolysin (tdh) gene was positive in two isolates (2.1%), and the thermostable direct hemolysin-related hemolysin (trh) gene was not detected in all isolates. Antibiotic resistance profiles of those isolates were as follows: ampicillin (87.5%), cephazolin (31.3%), cephalothin (6.3%), amoxicillin/clavulanic acid (6.3%), piperacillin (6.3%), and amikacin (3.2%). Thirty-three out of 96 isolates were resistant to two or more antimicrobial agents. It is suggested that V. parahaemolyticus in retail shellfish could be a potential risk to consumers in Shanghai.     

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.     

Campylobacter species and their antimicrobial resistance in Latvian broiler chicken production

In the present study Campylobacter species and their antimicrobial resistance in Latvian broiler chicken production was determined. Furthermore, this is the first report on the antimicrobial resistance patterns for Campylobacter isolates from broiler chickens at slaughterhouse and retail level in Latvia. Two biggest Latvian broiler chicken meat producing company products were included in the study. Altogether, 74 randomly selected broiler chicken Campylobacter spp. isolates were analysed for species identification. Campylobacter isolates were obtained during a 12-month period within the Latvian Campylobacter prevalence study in 2010. Colony multiplex PCR was used for all isolates to identify Campylobacter species. Minimal inhibitory concentration (MIC) was determined for 58 Campylobacter spp. isolates. Resistance to one or more antimicrobials was detected in all 58 isolates (100%). A high proportion of the isolates were resistant to ciprofloxacin (100%) and nalidixic acid (87.9%). Multidrug resistance, which was determined as resistance to three or more unrelated antimicrobials, was detected in 39 isolates (67.2%). Moreover, all multiresistant isolates were resistant to ciprofloxacin and nalidixic acid. Analyses of Campylobacter isolates from two Latvian broiler chicken meat producing companies resulted with significant differences in Campylobacter species; from the company A mainly Campylobacter coli were found, while in the company B Campylobacter jejuni.     

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.     

Isolation,identification and antimicrobial resistance of Cronobacter spp. isolated from various foods in China

Cronobacter spp. are important foodborne pathogens that can cause severe diseases such as meningitis, sepsis, and necrotizing enterocolitis in neonates. In this study, 195 food samples, including cereals, cereal products, powdered infant formula (PIF), infant food formula, herbs, spices, vegetables, and fruits, were analyzed for the presence of Cronobacter spp. by culture-based method. The presumptive isolates were further confirmed by targeting the 16S rDNA gene using PCR. Out of 195 samples, 13 samples (6.7%) were positive for Cronobacter species. 12 of 85 cereal and cereal products (14.1%), and 1 of 22 herbs and spices (4.5%) were contaminated. In contrast, no Cronobacter was detected in commercial powdered infant formula, infant food formula, vegetables, or fruits. Alignment of 16S rRNA gene sequences showed that 13 isolates was most closely related to the genus Cronobacter. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis revealed that Cronobacter sakazakii was the only Cronobacter species isolated from various food samples. The antimicrobial susceptibility of 13 Cronobacter isolates was determined by the standard disk diffusion method. All isolated strains, except one resistant to ampicillin, were sensitive or displayed intermediate susceptibility to the 10 antimicrobial agents investigated. No multiple drug resistance was observed.     

Low contamination of Campylobacter spp. on chicken carcasses in Minas Gerais state,Brazil: Molecular characterization and antimicrobial resistance

Here, we evaluated Campylobacter contamination on chicken carcasses and phenotypic and genotypic profiles of antimicrobial resistance of the isolated strains. A total of 95 of samples were collected from 19 slaughterhouses from Minas Gerais - Brazil, and analyzed by MPN-PCR method. Campylobacter was found in 16.8% of samples with microbial load ranging from 60 to 184 MPN/carcass. All isolates were resistant to at least 5 (31.2%) of the antimicrobials screened using the disk diffusion method. Thr-86-Ile gyrA mutation, bla_OxA-61 and tet(O) genes were found in 95%, 100% and 40% resistant isolates to ciprofloxacin, ampicillin and tetracycline, respectively. Almost all isolates (90%) showed the three genes required to synthesize the CmeABC efflux system. The use of efflux pump inhibitor (PAβN) resulted in a significant reduction in the MICs of antimicrobials (2–128 fold), indicating the importance of efflux systems in conferring antimicrobial resistance. Campylobacter were detected at low concentrations in Brazilian chicken carcasses. However, high-levels of antimicrobial resistance were observed and associated with several mechanisms. This study provides a baseline survey on contamination of Campylobacter in Brazilian chicken carcasses and its antimicrobial resistance, giving support for actions directed at reducing this pathogen in the food chain.     

Prevalence,seasonality and antibiotic susceptibility of Campylobacter spp. isolates of retail broiler meat in Iran

Campylobacter species, are the most common cause of bacterial gastroenteritis worldwide. The main route of transmission is generally believed to be via undercooked meat and meat products. This study was conducted to determine the prevalence, seasonality and antibiotic susceptibility of Campylobacter spp. isolates of retail broiler meat in Mashhad, Iran. From January 2013 through December 2013, 360 broiler meat samples were purchased in Mashhad, Iran. Identification of a presumptive Campylobacter species was performed using the cultural method and a polymerase chain reaction (PCR) assay. Antimicrobial susceptibility testing was performed using the disc diffusion method. Overall, 227 samples (63.1%) were positive for Campylobacter. The most prevalent Campylobacter spp. isolated was Campylobacter jejuni (88.1%). There was a significant seasonal prevalence of Campylobacter spp. in broiler meat in Mashhad, Iran (P < 0.0001). The highest isolation rate was also in summer (78.9%). The antimicrobial susceptibility test showed that 93.4% of the isolates were resistant to one or more antimicrobial agents. Resistances to tetracycline (87.2%) and ciprofloxacin (79.3%) were the most common resistances. The findings of this study showed a relatively high prevalence of Campylobacter contamination and antimicrobial resistance in broiler meats in Mashhad, Iran. To the authors' knowledge this is the first study on the seasonal prevalence and antibiotic susceptibility of Campylobacter spp. isolated from broiler meat in Iran.     

Isolation and characterization of Cronobacter spp. from indigenous infant flours sold in public health care centres within Abidjan,Côte d'Ivoire

The aim of this study was to evaluate the prevalence of Cronobacter spp. in indigenous infant flours sold in public health care centres within Abidjan (Côte d'Ivoire) and to assess their antimicrobial susceptibility. A total of 133 samples of cereal-based indigenous flours were collected from randomly selected public health care centres within Abidjan and subjected to Cronobacter spp. isolation and identification by using biochemical tests, API 20E system and duplex PCR detection. Subsequently, the antimicrobial susceptibility test was performed for confirmed isolates. Our results showed that the samples contained Cronobacter spp. in addition to 18 other Enterobacteriaceae species among with Enterobacter cloacae (21.84% of total isolates) and Pantoea spp. (14.08%) were the most frequently isolated species. Ninety samples (67.7%) were contaminated by Enterobacteriaceae and 16 samples (12.0%) by Cronobacter spp. Gentamycin, colistine, tobramycin, ticarcillin–clavunate and trimethoprim–sulphamethoxazole remained the most potent antimicrobial agents against Cronobacter spp. while resistance occurred most often to nalidixic acid (87.5%), aztreonam (75.0%), amoxicillin–clavunate (68.7%), ampicillin (62.5%) and cefotaxime (62.5%). Twelve resistant phenotypes were defined among Cronobacter spp. isolates and the most common phenotype (25% of isolates) was amoxicillin–clavunate/cefotaxime/aztreonam/tetracycline/nalidixic acid resistant. Furthermore, all the strains tested were resistant to at least four antibiotics.     

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.     

Antimicrobial resistance and virulence genes of Arcobacter isolates recovered from edible bivalve molluscs

The goals of this study were to assess the prevalence, antimicrobial susceptibility and the presence of virulence genes of arcobacters recovered from edible bivalve molluscs. A total of 106 samples (21 clams, 18 mussels, 20 oysters, 20 razor clams, 11 scallops and 16 surf clams) were analysed by culture between 2010 and 2013. The obtained colonies were identified by multiplex PCR and PCR-RFLP and genotyped by ERIC-PCR. Furthermore, nine putative virulence genes (cadF, ciaB, cjl349, irgA, hecA, hecB, mviN, pldA and tlyA) were assessed by PCR and the antimicrobial resistance was tested by the dilution agar method. The global prevalence was 40.5%, with the highest value in surf clams (87.5%) followed by razor clams (65.0%), mussels (33.3%), clams (23.8%), scallops (18.0%) and oysters (15.0%). The most commonly found species was Arcobacter butzleri (62%) followed by Arcobacter cryaerophilus (21%), Arcobacter skirrowii (16%) and Arcobacter defluvii (1%). A high resistance was found to nalidixic acid and ampicillin, while the predominant detected virulence genes were mviN (83.8%), ciaB (82.8%) and tlyA (72.7%). Our results indicate a high prevalence of arcobacters in shellfish and the pathogenic potential of the recovered isolates suggests that this type of food could be a plausible transmission route of virulent strains to humans.     

Antimicrobial resistance in thermotolerant Campylobacter isolated from different stages of the poultry meat supply chain in Argentina

The objective of this study was to investigate the antimicrobial resistance in thermotolerant Campylobacter spp. isolated from different stages of the poultry meat supply chain in Argentina. Six poultry meat chains were studied from the reproductive farm to the chicken at the retail. Chickens sampled along each food chain were from the same batch. Samples collected were: a) cloacal samples from hens and chickens on the farm, b) chicken carcasses from the slaughterhouse and retail market. Samples obtained were examined for Campylobacter spp. Antimicrobial resistance was evaluated using the disk diffusion method. Almost all isolates were resistant to nalidixic acid (91.2%) and ciprofloxacin (88.2%). A large proportion of thermotolerant Campylobacter isolated from hens and broilers <1 wk showed resistance to erythromycin in comparison with the rest of the stages of the poultry meat supply chain (P = 0.031). Campylobacter isolated from broilers (both <1 wk and >5 wk) and carcasses at slaughterhouse and at retail showed a proportion of resistance to ciprofloxacin and enrofloxacin higher than isolates from hens (P = 0.015 and P = 0.031, respectively). One strain was resistant to all the antibiotics analyzed, and 46.1% of the isolates were resistant to three or more drug classes. Almost 50% of the isolates were resistant to all quinolones tested (ciprofloxacin, nalidixic acid, and enrofloxacin), and 13.2% were resistant to all quinolones and erythromycin. Campylobacter strains isolated from carcasses at retail showed higher resistance to all quinolones than strains isolated from hens (P = 0.016). These results reflect an alarming situation with potential serious consequences to the public health.     

Safety aspects, genetic diversity and technological characterisation of wild-type Streptococcus thermophilus strains isolated from north Italian traditional cheeses

Antibiotic susceptibility, antimicrobial activity, genotypic and technological properties of 52 Streptococcus thermophilus isolates, collected from four north Italian traditional cheeses, was investigated. RAPD-PCR, was used to study genetic variability and distinguish closely related strains; the results showed a high degree of heterogeneity among isolates. With regard to technological properties, after 6 h of incubation in milk 25% of the streptococcal strains could be defined as fast acid producers, while after 24 h the majority of isolates (79%) displayed only weak acidification activity. Reduction activity was generally low; in fact, none of these S. thermophilus strains showed a Eh < −102 mV). All the studied S. thermophilus were susceptible to ciprofloxacin, levofloxacin, penicillin G, ampicillin, mupirocin, nitrofurantoin, quinupristin/dalfopristin and rifampicin. Nine isolates were classified as resistant to tetracycline, 6 to streptomycin, 5 to oxacillin, 3 to erytromycin, 3 to vancomycin and only one to chloramphenicol. PCR-based detection did not identify any of the common genetic determinants for vancomycin (vanA, vanB, vanC1, vanC2, vanC3, vanD, vanE, vanG) or erythromycin (ermB and ermC). The genetic basis of the tetracycline resistance phenotype in these strains was linked to tetS-tetL genes (8 isolates) or the tetM gene (1 isolate), and the integrase element int of the Tn916/Tn1545 family of transposons was negative. Four strains were able to produce antimicrobial compounds against Clostridium tyrobutyricum. The study provides new evidence of the resistance of S. thermophilus to antimicrobial agents, confirming the importance of including an accurate safety assessment of phenotypic/biotechnological data when carrying out strain selection for dairy applications.     

Effect of detergents as antibacterial agents on biofilm of antibiotics-resistant Vibrio parahaemolyticus isolates

Vibrio parahaemolyticus (V. parahaemolyticus) is a halophilic, Gram-negative human pathogen known as a leading cause of seafood-derived food poisoning. Due to high contamination rate of seafood in Asian countries, V. parahaemolyticus is considered as a food safety concern. V. parahaemolyticus is able to produce biofilm which is more resistant toward disinfectants and antibodies than its planktonic form. Thirty six V. parahaemolyticus isolates from seafood were tested for their susceptibility using 18 different antibiotics. Two V. parahaemolyticus isolates were resistant to bacitracin, chloramphenicol, rifampin, ampicillin, vancomycin, nalidixic acid, penicillin and spectinomycin. Fourteen V. parahaemolyticus isolates were found to be resistant to bacitracin, tetracycline, rifampin, ampicillin, vancomycin, penicillin and spectinomycin. The remaining two isolates were resistant to more than 2 antibiotics. Majority of the V. parahaemolyticus isolates (97.2%) showed MAR index > 0.2, indicating that these isolates were originated from high risk sources. To investigate effect of three common detergents on antibacterial-resistant V. parahaemolyticus, 16 V. parahaemolyticus isolates resistant to more than 7 antibiotics were selected. V. parahaemolyticus (ATCC 17802) was used as reference strain. Detergents were tested for their minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) and time–kill curves were constructed to assess the concentration between MIC and bactericidal activity of detergents. Detergents D1 (Linear alkyl benzene based) was found to be the most effective with MIC and MBC ranged between 97.656 and 1562.5 μg/ml and 781.25–3125 μg/ml, respectively. The time–kill curves demonstrated that the bactericidal endpoint for resistant V. parahaemolyticus isolates reached after 30 min incubation with D1 at concentration 8 × MIC. The isolate VP003 was killed at 8 × MIC within 0.5 h and the reduction in CFU/ml was 3 log units (99.9%). V. parahaemolyticus biofilms were formed in 96 wells microtiter plates at 37 °C and 24 h-old biofilm were used to test antibacterial activity of detergents. Results showed that biofilm-producing ability of antibacterial-resistant V. parahaemolyticus isolates were inhibited at 1562.5–6250 μg/ml of D1 and eradicated at 3125 – ≥50,000 μg/ml of D1. Detergents showed potential antimicrobial activity against V. parahaemolyticus     

Presence,distribution, serotypes and antimicrobial resistance profiles of Salmonella among pigs,chickens and goats in South Africa

Salmonellosis is an infectious zoonotic disease of socio-economic importance worldwide. Food animals with subclinical infection as well as farm effluents are usually the sources of contaminated meat, eggs and milk, which cause diarrhoea and systemic infections in humans. The indiscriminate use of antibiotics to curb salmonellosis in both animals and humans has contributed to the emergence and spread of drug-resistant bacteria among both pathogenic and commensal organisms. The aim of the study was therefore to determine the presence, serovar distribution and antimicrobial resistance profiles of Salmonella isolated from domestic livestock species in South Africa. For this purpose,1069 rectal and cloacal swabs were collected from pigs (n = 322), chickens (n = 286) and goats (n = 461) from smallholder farms in Limpopo, Eastern Cape, Northern Cape, North West and KwaZulu Natal provinces of South Africa. The frequency of occurrence of Salmonella per animal species was highest in pigs (5.90%; n = 19), followed by chickens (3.15%; n = 9) and goats had the lowest proportion of 0.43% (n = 2). Nine Salmonella serovars were obtained including S. Techimani, a serovar that was not previously observed in South African animals. Six isolates were assigned to Salmonella II. Some of the Salmonella were untypable (n = 6). All Salmonella isolates were sensitive to cefotaxime, enrofloxacin, florphenicol and polymyxin B. Most of the Salmonella isolates were resistant to at least one antimicrobial (n = 20; 66.7%) and resistance was predominant towards trimethoprim (n = 11; 36.7%), followed by ampicillin (n = 5; 16.7%), oxytetracycline (n = 3; 10%), and kanamycin (n = 1; 3.3%). The results illustrate the presence of diverse and rare Salmonella serovars that were not previously isolated from animals in South Africa. The pattern of development of antibiotic resistance should be monitored and followed-up. The occurrence of elevated trimethoprim resistant Salmonella in South African food animals could lead to the emergence and distribution of drug resistant salmonellosis in human beings.     

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.     

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.