Prevalence and antimicrobial resistance of Salmonella in retail foods in northern China

A total of 387 retail meat, seafood and milk powder samples were collected from nine cities in northern China in 2005 and screened for the presence of Salmonella. Salmonella strains isolated were subjected to serotyping and antimicrobial susceptibility testing. Salmonella was isolated from 81 (20.9%, 81/387) samples and classified into 23 serotypes. The isolates were frequently resistant to sulfamethoxazole (86.4%), sulfamethoxazole/trimethoprim (48.1%), nalidixic acid (30.9%), tetracycline (19.8%), carboxybenzylpenicillin (17.3%), amoxicillin (17.3%) and ampicillin (16.0%). The multiple resistance (resistance to ≥ 3 antibiotics) was found in 29.6% (n = 24) isolates. Additionally, 4 isolates from chicken displayed the ACSSuTNx profile, resistant to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline and nalidixic acid, in particular, strain HBS084 showing the resistance to as many as 20 antibiotics. Salmonella from chicken showed the higher frequency of antimicrobial resistance. Our findings indicate that in northern China food products of animal origin can be a source of exposure for consumers to multiresistant Salmonella strains.     

Comparison of the Antimicrobial and Sanitizer Resistance of Salmonella Isolates from Chicken Slaughter Processes in Korea

Salmonella is a foodborne pathogen worldwide. Outbreaks of Salmonella are commonly associated with consumption of contaminated foods such as poultry products. Therefore, the objective of this study was to determine the occurrence, biofilm formation, antibiotic resistance, and sanitizer resistance of Salmonella enterica isolated from chicken carcasses. A total of 318 samples were collected from 15 chicken slaughterhouses in 8 provinces of Korea. They were then examined for Salmonella contamination. S. enterica isolates were tested for their susceptibilities to 15 antimicrobials by broth microdilution method. Their biofilm formation ability and resistance to sanitizers were also evaluated. Eighty‐two isolates of S. enterica were obtained from the 318 samples. There were 14 serotypes and 2 untypable isolates. Fifty‐seven (69.5%) isolates were resistant to at least one antibiotic while 30 (36.6%) isolates were resistant to 5 or more antibiotics. Two S. Senftenberg and 3 S. Montevideo isolates exhibited considerable biofilm formation ability (A₆₀₀>0.2) following incubation in Luria‐Bertani (LB) broth for 48 h. Biofilm cell survival and recovery growth assay after sanitization showed that most isolates were highly susceptible to 2.5% lactic acid and 0.1% cetylpyridinium chloride. Therefore, lactic acid and cetylpyridinium chloride might be alternatively or additionally used in addition to chlorine‐based sanitizers that are frequently used to reduce Salmonella contamination of chicken carcasses. Our results provide basic information on the distribution of Salmonella serotypes in chicken slaughterhouses. This study also highlights the necessity to improve farming practices and use antimicrobial agents cautiously. This study also suggests that sanitization during the slaughtering process might be necessary to reduce Salmonella contamination of chicken carcasses.     

Molecular characterization of antibiotic resistant Salmonella isolates from Indian foods

Salmonella isolates belonging to five serovars, Salmonella enterica Ohio, S. Oslo, S. Tennessee, S. Weltevreden and S. Typhimurium, isolated during 2006-2008 from food samples like sprouts and different varieties of fresh water and marine fish were tested for antibiotic resistance. High percentages (97%) of the isolates were resistant to at least one antibiotic and 82% of the isolates were resistant to more than one antibiotic. S. Oslo was the most resistant serovar and it exhibited resistance to 13 out of 16 antibiotics tested. Integron 1, which has been shown to confer multidrug resistance to various Salmonella serovars, was detected in multidrug resistant S. Oslo. PFGE studies revealed that serovars showed very high genetic diversity. The multidrug resistant S. Oslo showed unique PFGE pattern, which could be used in epidemiological studies.     

Phenotypic and genetic characterization of antimicrobial resistance in Salmonella serovars isolated from retail meats in Alberta, Canada

This study determined the prevalence of Salmonella serovars, antimicrobial resistance (AMR) and resistance genes in Salmonella isolated from retail meats purchased in Alberta, Canada. Samples were collected during one year period (May 2007–April 2008) on weekly basis from 19 census divisions in Alberta. A total of 564 samples including chicken (n = 206), turkey (n = 91), beef (n = 134) and pork (n = 133) were purchased. Salmonella were recovered from chicken (40%), turkey (27%) and pork (2%) samples and was not found in ground beef. A total of 21, 8, and 3 different serovars were recovered from chicken, turkey and pork meats, respectively. Salmonella Hadar was most common in chicken whereas S. Heidelberg was common in turkey meat. Overall 29% (32/110) of isolates were susceptible to tested antimicrobials and resistance to ciprofloxacin, amikacin and nalidixic acid was not found in any isolate. Multiresistance (≥2 antimicrobials) was found in 56% of isolates. Resistance to amoxicillin–clavulanic acid (AMC), ceftiofur (TIO), and ceftriaxone (CRO) was found in about 21% of chicken and 25% of turkey isolates. Resistance to either of tetracycline (TET), streptomycin (STR) or ampicillin (AMP) was unconditionally associated with S. Hadar but resistance to either of TET, AMP, AMC, TIO, CRO or cefoxitin was associated with S. Heidelberg. The strA/B (42% isolates), tet(A) (28% isolates), bla_CMY-2 (21% isolates) and bla_TEM (17% isolates) were the most common resistance genes found. The bla_CMY-2 and bla_TEM genes were unconditionally associated with S. Heidelberg; tet(A) and strA/B with S. Hadar and tet(B) gene with S. Kentucky. The strA/B genes were not associated with S. Heidelberg. Our data suggests that the prevalence of Salmonella serovars varied by the meat type and that AMR and resistance genes varied by the Salmonella serovars.     

Prevalence, distribution, and molecular characterization of Salmonella recovered from swine finishing herds and a slaughter facility in Santa Catarina, Brazil

Swine can carry Salmonella strains that may be transmitted to humans by pork products. This investigation determined the distribution and types of Salmonella in 12 swine finishing herds and a slaughter facility in Santa Catarina, Brazil. A total of 1258 samples, consisting of environmental, feed, carcass, lymph node, and fecal material were collected and submitted to bacteriological isolation of Salmonella. From 487 positive samples, 1255 isolates were recovered and confirmed to be Salmonella. The distribution of positive samples was as follows: finishing pen floors 26% (16/61); feed 29% (42/143); feces 44% (52/119); pooled feces 59% (35/59); slaughter holding pens 90% (36/40); lymph nodes 46% (220/478); pre-chilled carcass surfaces 24% (24/98); and post-chilled carcass surfaces 24% (62/260). The most prevalent serovars were Typhimurium, Panama, Senftenberg, Derby, and Mbandaka. By pulsed-field gel electrophoresis, 1071 isolates were subtyped using XbaI, and duplicate isolates were removed. From the remaining 747 isolates, 163 macrorestriction profiles (pulsotypes) were identified. Six pulsotypes were considered very frequent, occurring in 33 isolates or more. The multiple correspondence analyses showed correlations between pulsotypes from shedding pigs (feces), herd environment (pen floors), and subiliac and prescapular lymph nodes and between lairage and carcass surface samples before and after chilling. All sources of Salmonella investigated contributed to the carrier state; however, pre-slaughter contamination at lairage was the variable most strongly associated with carcass contamination. A total of 59 different antimicrobial resistance profiles were observed in 572 Salmonella isolates. From these isolates, 17% (97/572) were susceptible to all 15 antibiotics tested, 83% (475/572) were resistant to at least one, and 43% (246/572) were resistant to four or more antibiotics (multi-resistant). The AmpGenKanTet profile was the most prevalent in carcass isolates and was associated with farm origin.     

Prevalence and Characterization of Salmonella Isolated from Chicken Meat in Turkey

This study was conducted in a Turkish province to investigate the presence of Salmonella spp. in 150 chicken meat samples using 2 phenotyping techniques: classic culture technique (CCT) and immunomagnetic separation (IMS). For the confirmation of the isolates at molecular levels, invA gene was detected in these isolates. The presence of invA, class 1 (Cls1) integrons, and integrase (Int1) genes was demonstrated by PCR assay; and the resistance of the isolated Salmonella spp. strains to antibiotics was determined by disk diffusion test. All the cultural and PCR results were evaluated together; Salmonella spp. were detected in a total of 64 (42.66%) chicken meat samples. Contamination rate was higher in carcasses (53.33%, n = 75) than in meat pieces (32%, n = 75). When results of standard culture were compared with IMS technique, IMS (n = 54) showed a clear superiority over the CCT (n = 38). A very high resistance rate (≥89.28%) to vancomycin, tetracycline, streptomycin, or nalidixic acid was found. Trimethoprim‐sulfamethoxazole resistance was present in 32.14%. Relatively lower incidence of resistance (≤8.33%) to gentamicin, chloramphenicol, ampicillin, and ceftriaxone was observed. Concurrent resistance to at least 4 antibiotics was detected in 92.85% of the isolates. Cls1 integrons and Int1 were positive in 80.95% and 95.23% of the isolates, respectively. However, Int1 alone was detected in 15.47% (n = 13). In conclusion, the high prevalence of Salmonella spp. in chicken meat may pose a potential public health risk, and the presence of antibiotic‐resistant Salmonella spp. isolate together with Cls1 integron and/or integrase might play an important role in horizontal antibiotic gene transfer.     

Salmonella spp. contamination in fresh pork and chicken sausages marketed in Niterói and Rio de Janeiro,Brazil

Fresh sausages are one of the most popular meat products consumed in Brazil. However, the use of contaminated raw material, unhygienic handling during processing, and inadequate storage could be hazardous to consumer’s health, since fresh-sausage processing does not include heat treatment and the product may carry several human pathogens such as Salmonella spp.. In this study, a total of 80 fresh sausages prepared with pork and chicken meat were evaluated regarding Salmonella spp. presence by PCR after selective enrichment and bacteriological culture. Twenty-one sausage samples (27 %) proved to be contaminated with Salmonella spp.. Sixteen (76 %) contaminated samples were detected by PCR combined with enrichment broth culturing, whereas conventional microbiological screening detected only 8 (38 %). In this study, evidence was raised regarding packing conditions of fresh sausages, since it seems that there is no significant difference in Salmonella spp. contamination among samples in their original packing (23 %), wrapped in plastic or unpacked (27 %). Similarly, meat composition seems not to have a determinant influence in contamination, since 20 % of the chicken and 29 % of the pork sausages were contaminated. The contamination rate of Tuscan-type sausages was 37 %, while contamination was found in 21 % of ham sausages, suggesting that the cut of pork did not have a determinant influence in the contamination by Salmonella in fresh sausages. The results shown here indicate that fresh sausages marketed in Niterói and Rio de Janeiro may be contaminated with Salmonella spp., requiring more attention by sanitary authorities in order to assure the safety of this food.     

Analysis of ERIC-PCR genomic polymorphism of Salmonella isolates from chicken slaughter line

The chicken slaughter line is a source of cross-contamination of Salmonella. In this study, ERIC-PCR was applied to analyse the ERIC-PCR genomic polymorphism of Salmonella isolates from a commercial chicken slaughter line and to trace the route of contamination. Samples were collected from carcasses and contact surfaces at the points of post-evisceration, post-chilling and post-grading. The prevalence of Salmonella at the evisceration point was high but significantly decreased along the slaughter line. The ERIC-PCR fingerprints indicated that a total of seven groups were clustered, and the genotypic diversity of isolates progressively decreased along the slaughter line. By tracing the genotypic diversity, contact surfaces at post-evisceration were found to be the major contamination sources of Salmonella during chicken processing, since the genotype diversity of isolates from the post-evisceration point could be exactly matched to that from the post-chilling and post-grading points. Interestingly, three Salmonella strains were still detected after decontamination and washing; these three isolates having a strong capacity for attachment were able to produce biofilm on polystyrene surfaces. This study suggests that the evisceration point is the source of cross-contamination, with Salmonella isolates still present after washing procedure. Therefore, more effective measures must be undertaken to control the spread of Salmonella in such processing lines.     

Multiplex TaqMan® detection of pathogenic and multi-drug resistant Salmonella

Overuse of antibiotics in the medical and animal industries is one of the major causes for the development of multi-drug-resistant (MDR) food pathogens that are often difficult to treat. In the past few years, higher incidences of outbreaks caused by MDR Salmonella have been increasingly documented. The objective of this study was to develop a rapid multiplex real-time polymerase chain reaction (PCR) assay for simultaneous detection of pathogenic and MDR Salmonella spp. A multiplex TaqMan®real-time PCR was designed by targeting the invasin virulence gene (invA), and four commonly found antibiotic resistance genes, viz. ampicillin, chloramphenicol, streptomycin and tetracycline. To avoid false negative results and to increase the reliability of the assay, an internal amplification control (IAC) was added which was detected using a locked nucleic acid (LNA) probe. In serially diluted (5 ng–50 fg) DNA samples, the assay was able to detect 100 genomic equivalents of Salmonella, while in a multiplex format, the sensitivity was 1000 genomic equivalents. The assay performed equally well on artificially contaminated samples of beef trim, ground beef of different fat contents (73:27, 80:20, 85:15 and 93:7), chicken rinse, ground chicken, ground turkey, egg, spinach and tomato. While the detection limit for un-enriched inoculated food samples was 10⁴ CFU/g, this was improved to 10 CFU/g after a 12-h enrichment in buffered peptone water, with 100% reproducibility. The multiplex real-time assay developed in this study can be used as a valuable tool to detect MDR virulent Salmonella, thus enhancing the safety of food.     

Prevalence and distribution of Salmonella serotypes in marketed broiler chickens and processing environment in Coimbatore City of southern India

Broiler chicken is gaining popularity among the consumers of India. Since poultry is recognised as a leading food vehicle for Salmonella contamination, the prevalence and distribution of Salmonella serotypes in broiler chickens and processing environments of retail outlets has been studied. In the present study 214 samples of broiler chicken and 311 environmental samples from cage were analysed for the presence of Salmonella. Of the various body parts of live chicken analysed prevalence varied from 1.4% in cloacca to 6.9% in crop region. Environmental samples from the cage showed higher prevalence of Salmonella ranging from 0 to 16.67%. Apart from Salmonella enteritidis, which was the predominant Salmonella serotype in the chickens as well as in the environmental samples, other serotypes such as S. bareilly, S. cerro, S. mbandaka and S. molade were also encountered. The results of the research calls for strict hygiene standards for retail broiler chicken processing outlets.     

Microbiological quality of chicken wings damaged on the farm or in the processing plant

Selling of damaged chicken wings (those with bone protrusion) for human consumption is prohibited in the European Union on the grounds of possible risks to human health arising from microbial contamination. Standard food industry tests were used to assess different categories of chicken wings (undamaged, farm damaged and factory damaged; n = 264) for, coliforms, Enterobacteriaceae, total viable counts, Pseudomonas spp., Staphylococcus aureus and Salmonella spp. No significant differences in bacterial numbers existed among wings belonging to the three categories. Only low numbers of bacteria were found throughout, and 97% of all results would pass the standards of a leading UK retailer. These results were strengthened by a longitudinal survey of wing breakage, which showed almost all wing puncturing occurred during the de-feathering process, limiting the likelihood of microbial contamination. Combined, these results indicate there is no increased health risk from consumption of damaged, compared to undamaged, chicken wings. The existing imposed regulations may therefore be an unnecessary burden on the poultry industry.     

Multiplex PCR for the simultaneous detection of Salmonella spp. and Salmonella Enteritidis in food

Multiplex PCR assay (mPCR) for the detection of Salmonella spp. and S. Enteritidis was developed in this study using artificially contaminated chicken carcasses. The assay showed 100% specificity to detect approximately 1 CFU of Salmonella in 10 g of chicken skin after non‐selective enrichment. The mPCR was evaluated in Minas cheese, fresh pork sausage and chicken carcasses commercially available. Salmonella spp. was detected in nine of sixty‐six chicken carcasses, five of fifty‐two cheese samples, and five of fifty‐two sausage samples. The serovar Enteritidis was detected in two samples of contaminated sausage. The mPCR results were confirmed by conventional culture and biochemical identification of the isolates. Serotyping confirmed the presence of S. Enteritidis in sausage samples and showed contamination by serovars Schwarzengrund and Montevideo in chicken carcasses.     

Detection and characterization of Salmonella in lairage, on pig carcasses and intestines in five slaughterhouses

In this study, conducted at five slaughterhouses, individual pigs were sampled and followed up from stunning to cooling down of the carcasses. In this way, Salmonella prevalence and possible risk points were described. At the lairage area, pens were sampled using overshoes. At stunning and bleeding, pigs were individually identified and subsequently swabs were taken of the oral cavity and the carcass after polishing, splitting and forced chilling. Additionally, duodenum, ileum, rectum and mesenteric lymph nodes were extracted and samples were taken of the scalding water. All samples were submitted to Salmonella isolation and Salmonella isolates were serotyped and genotyped by pulsed-field gel electrophoresis (PFGE). Of all samples taken (n = 1953), 14.1% were Salmonella positive. The prevalence of S. in the lairage area varied widely (from 0 to 100%) between the slaughterhouses. Of the sampled pigs (n = 226), 48.2% were positive in at least one sample. Statistical analysis revealed that the contamination of the lairage area was related to a higher amount of positive carcasses after polishing. Furthermore, the contamination of the carcasses after splitting and forced chilling was related to the contamination level of the carcass after polishing. A relation between the outer (carcass) contamination and the inner (gut content and lymph nodes) contamination of a pig could not be established. The predominant serotypes were S. Typhimurium (58.7%) and S. Derby (17.4%). Genotyping revealed 46 different PFGE profiles among the 276 Salmonella isolates. The same genotype at the lairage area as in the oral cavity of the pigs was found in 95%. The results indicate that the lairage area is a primary source of Salmonella in slaughter pigs and that carcass contamination originates from the environment rather than from the pig (inner contamination) itself. It further shows that slaughterhouses vary in their capability of dealing with Salmonella positive pigs. A slaughterhouse specific approach is needed, however, general guidelines should be provided to decrease the contamination level of the lairage area and the slaughter environment.     

Salmonella contamination of laying-hen flocks in two regions of Algeria

A preliminary epidemiological study of Salmonella contamination in laying-hen flocks was carried out in the regions of Annaba and Eltarf, Algeria, from March to October 2008 and March to November 2009. Our objectives were (i) to estimate the prevalence of infection by Salmonella spp. in seven pooled samples during the hens' laying period (ii) to identify the serotypes and antimicrobial resistance phenotypes of isolates, and (iii) to characterize the factors that may be related to Salmonella contamination in Algerian henhouses. For this purpose, 18 out of 22 operational laying-hen houses were sampled one to three times during these periods: once at the start of laying (pullets aged 22–31 weeks), once in the middle of laying (47–60 week) and once at the end of laying prior to depopulation (70–86 week). The flocks'Salmonella status was assessed by collecting 2754 environmental samples that were analyzed according to the ISO 6579 method. The antibiotic resistance of Salmonella strains was tested as per the guidelines of the Clinical and Laboratory Standards Institute (CLSI). The relationship between each potential risk factor and the Salmonella status of laying-hen flocks was evaluated by calculating the relative risk with 95% confidence intervals. Eight flocks tested positive for Salmonella spp., with a higher prevalence at the end of laying than at either the beginning or middle. Only 19 isolates were recovered from the 2754 samples analyzed and nine different serotypes identified. S. enteritidis (n = 4) was the most prevalent serovar, along with S. Kentucky and S. Hadar (n = 3), followed by S. Heidelberg, S. Manhattan and S. Virchow (n = 2), whereas S. Dublin, S. Typhimurium and S. Albany were found only once. Thirteen isolates were resistant to at least one antimicrobial agent. Of these, six were resistant to at least three different antimicrobial classes. Salmonella serovar Kentucky isolates were resistant to fluoroquinolones with ciprofloxacin MIC ≥ 8 mg/L. Six risk indicators were identified as potentially related to the Salmonella status of layer houses.     

Characterization and horizontal transfer of class 1 integrons in Salmonella strains isolated from food products of animal origin

A total of 81 Salmonella isolates from retail meats and seafood in Hebei province, China, were assayed for the presence of and horizontal transfer of class 1 integrons. By the PCR screening for the integrons, class 1 integron was detected from strains in serotypes of Derby, Indiana, London and Choleraesuis, which were isolated from pork, chicken or seafood; however, two isolates contained the empty integron that lacked the resistance cassette, a potential hotspot for development of the multidrug resistance. In contrast, two other isolates had the antibiotic resistance gene cassettes within the class 1 integron, which were dfrA1-aadA1 and aadB-cmlA, respectively. The conjugation experiments demonstrated the plasmid-mediated transfer of the class 1 integrons. Furthermore, each of the integrons was transmitted to Streptococcus mutans via natural gene transformation. These findings suggest the possible transfer of class 1 integrons from foodborne pathogens to human residential bacteria via horizontal gene transfer.     

The Presence of Salmonella spp. in Belgrade Domestic Refrigerators

The probability of contamination of domestic refrigerators seems to be greater for Salmonella, than other, distinctly psychrotolerant bacteria. This survey investigated Salmonella spp. contamination of domestic refrigerators in households (n = 100). The presence of Salmonella species was found in 13.95% of households that kept eggs in designated egg storage in refrigerators (n = 86). We identified 12 serotypes of Salmonella spp. with antimicrobial resistance, of which 50% were identified as S. Typhimurium. The results obtained confirm the need to strongly advise consumers how to properly arrange different foodstuffs inside household refrigerators.     

Toxin profile, antibiotic resistance, and phenotypic and molecular characterization of Bacillus cereus in Sunsik

Sunsik, a ready-to-eat food in Korea, is comprised of various agricultural and marine products, and has been an important concern in Bacillus cereus food poisoning. The aim of this study was to investigate the toxin profiles, genotypic and phenotypic patterns as well as antibiotic resistance of B. cereus strains isolated from Sunsik. A subtyping method known as automated repetitive sequence-based PCR system (DiversiLab™) was used to assess the intraspecific biodiversity of these isolates. Thirty-five B. cereus strains were isolated from 100 commercial Sunsik samples, all of which harbored at least 1 enterotoxin gene. The detection rates of nheABC, hblCDA, cytK, and entFM enterotoxin gene among all isolates were 97%, 86%, 77%, and 100%, respectively. Most strains also produced corresponding enterotoxins such as HBL (83%) and NHE (94%). One strain (2.9%) carried the emetic toxin genes, including ces and EM1, and was positive for the HEp-2 cell emetic toxin assay. Most strains were positive for various biochemical tests such as salicin hydrolysis (86%), starch fermentation (89%), hemolysis (89%), motility test (100%) and lecithinase hydrolysis (89%). All isolates were susceptible to most antibiotics although they were highly resistant to β-lactam antibiotics. By using the automated rep-PCR system, all isolates were successfully differentiated, indicating the diversity of B. cereus strains present in Sunsik.     

Pulsed field,ribotype and integron analysis of multidrug resistant isolates of Salmonella enterica serovar Newport

Twenty-one isolates of Salmonella enterica serovar Newport were evaluated for their antimicrobial resistance, pulsed field gel electrophoresis (PFGE) profiles, ribotype profiles, and their integron profiles. Antimicrobial resistance profiles indicated that 20 of the 21 isolates were resistant to the following antibiotics: amoxicillin–clavulanic acid (AMOX/CA), ampicillin (AMPC), cefoxitin (CFOX), ceftiofur (TIO), cephalothin (CRIN), chloramphenicol (CHL), streptomycin (STR), tetracycline (TET), and sulfamethoxazole (SMX). Five isolates showed resistance to gentamycin (GEN) and kanamycin (KAN). Trimethoprim–sulfamethoxazole (SMX/TMP) resistance was observed in six isolates. Eight of the twenty one isolates showed intermediate resistance to ceftriaxone (CTRX), with one isolate exhibiting complete resistance. PFGE clearly resolved the Salmonella Newport isolates into nine distinct clusters, and a good congruence was observed between PFGE and antibiotic resistance patterns. Automated riboprinting clearly distinguished between antibiotic resistant and sensitive strains of Salmonella Newport, and resolved the isolates into two ribogroups. One group consisted of the multidrug resistant isolates, and the other grouping contained the sensitive isolate. Three different integrons (1.0, 1.2, and 1.8 kb) were observed in many of the isolates, and several isolates contained more than one integron. Restriction fragment length polymorphisms (RFLP) indicated that integrons of the same size were indistinguishable.When integron analysis and ribotype analysis were used in conjunction, four subtypes of multidrug resistant Salmonella Newport isolates were clearly defined. These results demonstrate the possibility of utilizing automated ribotyping and integron analysis to rapidly subtype multidrug resistant Salmonella Newport isolates.     

Monitoring of radical scavenging compounds from oxidized lipids (RSOL) by 2,4-dinitrophenylhydrazine (DNPH) derivatization in thermally oxidized linoleic acid and lard systems

From February to October 2011, 209 samples of retail raw meat and fishery products were randomly obtained from 41 grocery stores in Korea and cultured for the presence of Enterococcus spp. Ninety-six enterococcal isolates were recovered from 76 samples, with contamination rates ranging from 18.5% in fishery product samples to 43.9% in chicken samples. Antimicrobial disk susceptibility testing was conducted according to the Clinical and Laboratory Standards Institute protocol. The antibiotic resistance rates of the 96 enterococci isolates were as follows: tetracycline (TE) 77.1%; erythromycin (E) 50%; rifampin (RD) 44.8%; and vancomycin (VAN) 9.4%. Disk diffusion showed that 9 isolates were resistant to vancomycin. The minimum inhibitory concentration (MIC) was ≥32 μg/mL for all 9 isolates, and all were resistant to vancomycin. Among the 9 vancomycin-resistant enterococci (VRE) identified, the vanA gene was carried by 1 Enterococcus durans strain and the vanB gene was carried by 2 Enterococcus faecium, and 1 Enterococcus hirae strains. Further genotyping of the VRE isolates using pulsed-field gel electrophoresis (PFGE) revealed extensive heterogeneity. The VRE were recovered from various animal sources with a particularly high prevalence of E. faecium found in fishery products and chicken.     

Prevalence and characterization of Salmonella enterica in dried milk-related infant foods in Shaanxi,China

The aim of this study was to investigate the existence and characteristics of Salmonella enterica in dried milk-related infant foods. Twenty-four (3.4%) of 705 samples, including 5 (2.0%) of 246 powdered infant formula, 18 (4.0%) of 445 infant rice cereal, and 1 (7.1%) of 14 other infant foods, were positive for Salmonella. Fifteen serotypes were identified in 40 Salmonella isolates; Salmonella Duesseldorf (15.0%) and Salmonella Indiana (15.0%) were more frequently detected than other serotypes. Resistance to chloramphenicol (82.5%) was most common, followed by tetracycline (57.5%), ceftiofur (52.5%), kanamycin (52.5%), streptomycin (50.0%), gentamycin (45.0%), nalidixic acid (35.0%), ceftriaxone (32.5%), ciprofloxacin (25.0%), amikacin (20.0%), and cefoxitin (15.0%). Twenty-eight (70.0%) isolates were resistant to ≥8 antimicrobials, with 5 (12.5%) being resistant to 14 antimicrobials. Amino acid substitutions in gyrase A (GyrA) were most frequently detected as Ser83Arg/Asp87Glu and in p53-associated Parkin-like cytoplasmic protein (ParC), they were all Ser80Arg; the quinolone resistance gene qnrS (47.5%) was commonly detected as well as aminoglycoside acetyltransferase [aac(6′)-Ib; 25.0%], qnrA (17.5%), and qnrB (15.0%) genes. Thirty distinct pulsed-field gel electrophoresis patterns were identified among 40 isolates; no identical pulsed-field gel electrophoresis pattern was detected among Salmonella isolates with the same serovar that was recovered in 2010 and 2012. Our results suggest that dried milk-related infant foods could be contaminated with Salmonella and highlight that the dangers to infant health should not be neglected.