Effect of folic acid supplementation on proliferation and apoptosis in bovine mammary epithelial (MAC-T) cells.

Folic acid (FA) is known to be an important micronutrient in humans; however, information regarding the effect of FA supplementation on bovine mammary epithelial (BME) cells is insufficient. FA supplementation is reported to increase milk production in dairy cows, but the underlying molecular mechanisms are unknown. This study examined the effects of FA supplementation on the proliferation and apoptosis of a BME cell line (MAC-T). MAC-T cells were treated with various concentrations (deficient in FA (DF) < 0.01 ng/mL; low-level FA (LF) 3.1 ng/mL; normal FA (NF) 15.4 ng/mL; and high-level FA (HF) 30.8 ng/mL) based on serum folate (10-20 ng/mL) in milking cows. HF treatment significantly increased the proliferation of MAC-T cells. Cellular apoptosis was observed mainly in the DF group. The number of apoptotic cells in DF media was significantly higher than that in NF media. The bcl-2/bax mRNA expression ratio was significantly increased in the HF group compared to that in the DF group. FA supplementation significantly increased the ratio of Bcl-2/Bax protein levels in MAC-T cells. FA supplementation increases proliferation and decreases apoptosis in these cells. This study might provide information regarding the molecular mechanism through which FA supplementation is associated with increased milk yield.

Prevalence, Antibiotic-Resistance, and Virulence Characteristics of Vibrio parahaemolyticus in Restaurant Fish Tanks in Seoul, South Korea.

Vibrio parahaemolyticus is a marine bacterium that causes foodborne diarrhea. Many seafood restaurants keep live fish and shellfish in fish tanks for use in raw seafood dishes; thus, the present study aimed to investigate the prevalence, antibiotic-resistance, and virulence characteristics exhibited by V. parahaemolyticus detected in restaurant fish-tank water samples collected in Seoul, South Korea. Fish-tank water samples were collected from 69 restaurants in Seoul, and screened for the presence of V. parahaemolyticus via both a commercial detection kit, and a real-time polymerase chain reaction (RT-PCR) to detect the toxR gene. Antibiotic susceptibility and virulence determinants of V. parahaemolyticus isolates were evaluated and identified using standard disk-diffusion and RT-PCR methods, respectively. Thirty-five (50.7%) of the 69 analyzed water samples were found to be contaminated with V. parahaemolyticus. Those isolates were most often resistant to ampicillin (51.4% of isolates), followed by amikacin and tetracycline (11.4%), and ceftazidime (8.6%). Thirty (85.7%) out of the 35 isolates carried all four cytotoxicity-inducing type III secretion system 1 (T3SS1) genes [specifically, 34 (97.1%), 33 (94.3%), 35 (100%), and 32 (91.4%) isolates carried genes encoding the VP1670, VP1686, VP1689, and VP1694 T3SS1 proteins, respectively]. The type VI secretion systems (T6SS1 and T6SS2) genes were also detected in 11 (31.4%) and 27 (77.1%) isolates, respectively. However, virulence determinants such as the hemolysin (tdh and trh), urease (ureC), T3SS2α, or T3SS2ß genes that are known to be associated with enterotoxicity were not detected in all isolates. Although some known major virulence genes were not detected in the V. parahaemolyticus isolates, the results of this study indicate that restaurant fish tanks are a potential source of antibiotic-resistant V. parahaemolyticus. The presented data support the need for strict guidelines to regulate the maintenance of restaurant fish tanks to prevent antibiotic-resistant foodborne vibriosis.

Prevalence, toxin-typing, and antimicrobial susceptibility of Clostridium perfringens from retail meats in Seoul, Korea.

Clostridium perfringens is a ubiquitous, Gram-positive, spore-forming bacterium. It can contaminate many types of retail meat products and cause food poisoning by producing enterotoxins in the small intestines of humans and domestic animals. We investigated the prevalence, toxin-encoding gene profile, and antimicrobial resistance of C. perfringens in beef, chicken, and pork meat purchased from retail markets in Seoul, Korea. C. perfringens was detected according to the International Organization for Standardization 7937, with some modifications, and confirmed using the Vitek 2 system. In total, 38 C. perfringens strains were isolated from 200 meat samples (38/200, 19%; thirty-three from chicken, and five from beef). Among the six toxins evaluated, including alpha, beta, epsilon, iota, enterotoxin (encoded in the cpe gene), and netB, only the cpa gene was detected in all isolates by polymerase chain reaction (PCR) amplification. The antimicrobial resistance of the isolates was evaluated using the agar dilution method and resistance to ampicillin (12/38, 31.6%), tetracycline (38/38, 100%), chloramphenicol (26/38, 68.4%), metronidazole (13/38, 34.2%), and imipenem (27/38, 71%) was observed. Interestingly, 30 of the 38 isolates (78.9%) were multiple-drug resistant, showing resistance to more than three different antimicrobial classes.

Comparison of Direct Syringe Filtration and Membrane Filtration for the Selective Isolation of Campylobacter jejuni from Ready-to-Eat Sprouts.

Culture method using enrichment broth and selective agar is one of the most common isolation methods for detecting Campylobacter jejuni from food. However, the overgrowth of competing bacteria in enrichment culture complicates the selective isolation of C. jejuni. In this study, we compared an enrichment/plating method for the isolation of C. jejuni from sprout samples with an enrichment/plating method with syringe or membrane filtration when transferring enriched broths to plates. Four types of sprout samples were artificially contaminated with various levels of C. jejuni and incubated in 100 mL of Bolton broth for 48 h. Enrichment broths were either directly transferred onto modified charcoal-cefoperazone-deoxycholate agar or filtered through membrane or with a syringe. A significantly higher (p < 0.05) isolation rate of Campylobacter positives was obtained with both filtration methods (58-61%) than with the method without filtration (10%). Membrane filtrations yielded 61%, whereas syringe yielded 58% positives. In most cases of unfiltered samples (98%), high competing flora covered most of the plate, making differentiation and picking of suspicious colonies difficult. However, less plates were contaminated with competing flora in both filtration methods. Only 5% of plates were contaminated in the syringe filtration method, whereas no competing flora was observed in membrane filtration (0%).

Evaluation of Selective-Enrichment and Chromogenic Media for Salmonella Detection in Raw Shell Egg Contents with a Low Microbial Load.

The current study was conducted to evaluate the ability to recover Salmonella from shell egg contents by culture methods. A total of 4,000 eggs were obtained from a grading and packing center located in the Gyeonggi Province of South Korea, and 200 samples were created by pooling 20 broken eggs. The pooled samples were held at room temperature for 4 d before a 25-mL aliquot of each pool was added to 225 mL of modified trypticase soy broth (mTSB) and incubated at 35°C for 24 ± 2 h. A loopful of the culture was streaked onto chromogenic Druggan-Forsythe-Iversen (DFI) agar and incubated at 36 ± 1°C for 18-24 h. In addition, 1 mL and/or 0.1 mL of the mTSB cultures were added to 10 mL of Muller-Kauffmann tetrathionate with novobiocin (MKTTn) or Rappaport-Vassiliadis (RV) broth, and they were incubated for 24 ± 2 h at 35 ± 2°C or 42 ± 0.2°C, respectively. A loopful from these cultures was streaked onto Brilliant Green (BG), xylose lysine deoxycholate (XLD), and bismuth sulfite (BS) agar plates, respectively. Directly streaking onto DFI agar revealed the presence of Salmonella in 14 out of the 200 pooled samples (7%); whereas the combination of RV medium and BG, XLD, and BS agar detected the pathogen in only 9 (4.5%), 7 (3.5%), and 3 (1.5%) of the pooled samples, respectively. When MKTTn broth was used, Salmonella was detected in 7 (3.5%), 2 (1%), and 0 (0%) of the samples when streaked onto BG, XLD, and BS agar, respectively. The results indicate that direct plating onto DFI agar without enrichment was the most suitable among the methods evaluated in this study for detecting Salmonella in raw shell egg contents with a low microbial load.

A Single-Step Enrichment Medium for Nonchromogenic Isolation of Healthy and Cold-Injured Salmonella spp. from Fresh Vegetables.

Culture-based detection of nontyphoidal Salmonella spp. in foods requires at least four working days; therefore, new detection methods that shorten the test time are needed. In this study, we developed a novel single-step Salmonella enrichment broth, SSE-1, and compared its detection capability with that of commercial single-step ONE broth-Salmonella (OBS) medium and a conventional two-step enrichment method using buffered peptone water and Rappaport-Vassiliadis soy broth (BPW-RVS). Minimally processed lettuce samples were artificially inoculated with low levels of healthy and cold-injured Salmonella Enteritidis (100 or 101 colony-forming unit/25 g), incubated in OBS, BPW-RVS, and SSE-1 broths, and streaked on xylose lysine deoxycholate (XLD) agar. Salmonella recoverability was significantly higher in BPW-RVS (79.2%) and SSE-1 (83.3%) compared to OBS (39.3%) (p < 0.05). Our data suggest that the SSE-1 single-step enrichment broth could completely replace two-step enrichment with reduced enrichment time from 48 to 24 h, performing better than commercial single-step enrichment medium in the conventional nonchromogenic Salmonella detection, thus saving time, labor, and cost.

Resistance of Strains Producing Extended-Spectrum ß-Lactamases Among Salmonella from Duck Carcasses at Slaughterhouses in Three Major Provinces of South Korea.

The current study was carried out to estimate Salmonella spp. contamination of duck carcasses and to determine the antibiotic susceptibility profiles and serotype distribution of the isolates. Salmonella spp. was detected in 21.7% (26/120) of fresh raw duck carcasses sampled at different slaughterhouses in South Korea. Eight Salmonella serovars were identified; the most prevalent serovar was S. Typhimurium (34.6%), followed by S. Virchow (30.8%). All isolates were resistant to at least one antibiotic, and five remarkable isolates were resistant to more than 10 antibiotics, including third- and fourth-generation cephalosporins. Additional phenotypic and genetic characterization demonstrated that these isolates harbored resistance genes to broad-spectrum ß-lactams, blaCTX-M-15 and blaCMY-2 genes, among the most prevalent ß-lactamase enzymes worldwide. Based on molecular subtyping performed using the DiversiLab™ automated repetitive-sequence-based PCR system, isolates were classified into cluster A and cluster B. Among ß-lactamase-producing Salmonellas, the isolate showing >98% similarity in their repetitive-sequence-based PCR banding pattern seemed to have acquired the resistance gene (blaCMY-2) and thus a distinct multiresistance profile. Given that antibiotic-resistant genes might be transferred by plasmid-mediated conjugation, periodic microbiological assessment within slaughterhouses is recommended for pathogens not to be transmitted through cross-contamination during slaughtering and dressing.

Evaluation of Tazobactam-Supplemented, Modified Charcoal-Cefoperazone-Deoxycholate Agar for Qualitative Detection of Campylobacter from Chicken Carcass Rinse.

Overgrowth of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli on modified charcoal-cefoperazone-deoxycholate agar (mCCDA) is the most common confounding factor for the isolation of Campylobacter from poultry samples. mCCDA modified by supplementation with tazobactam, an ESBL inhibitor, was evaluated for Campylobacter isolation from chicken carcass rinse with regard to isolation rate and selectivity. In total, 120 whole chicken carcasses purchased from retail stores were rinsed with buffered peptone water enriched with 2× blood-free Bolton broth at 42°C for 48 h and then inoculated onto mCCDA with and without tazobactam supplementation (mCCDA or T-mCCDA) at 42°C for 48 h under microaerobic conditions. Suspect colonies were subcultured and confirmed by colony PCR. Plates with tazobactam exhibited a higher Campylobacter isolation rate (56.7% vs. 30.8%, p < 0.05) and selectivity (0.8 vs. 83.3% plates contaminated with non-Campylobacter, p < 0.05) than mCCDA. Thus, tazobactam-supplemented mCCDA would be a useful option for qualitative detection of Campylobacter in chicken carcass rinse.

High Occurrence Rate and Contamination Level of Bacillus cereus in Organic Vegetables on Sale in Retail Markets.

Organic foods have risen in popularity recently. However, the increased risk of bacterial contamination of organic foods has not been fully evaluated. In this study, 100 samples each of organic and conventional fresh vegetables (55 lettuce samples and 45 sprout samples) sold in South Korea were analyzed for aerobic bacteria, coliforms, Escherichia coli, and Bacillus cereus. Although the aerobic bacteria and coliform counts were not significantly different between the two farming types (p > 0.05), the occurrence rate of B. cereus was higher in organically cultivated vegetables compared with those grown conventionally (70% vs. 30%, respectively). The mean contamination level of B. cereus-positive organic samples was also significantly higher (1.86 log colony-forming unit [CFU]/g vs. 0.69 log CFU/g, respectively) (p < 0.05). In addition, six samples of organic vegetables were found to be contaminated with B. cereus at over 4 log CFU/g categorized as unsatisfactory according to Health Protection Agency guideline. The relatively higher occurrence rate of B. cereus in organic vegetables emphasizes the importance of implementing control measures in organic vegetable production and postharvest processing to reduce the risk of food poisoning.

High occurrence of extended-spectrum ß-lactamase-producing Salmonella in broiler carcasses from poultry slaughterhouses in South Korea.

The emergence of antibiotic-resistant foodborne Salmonella has become a major public health problem. Consumption of undercooked poultry contaminated with Salmonella can induce food poisoning in humans. In this study, we investigated the occurrence and antibiotic resistance patterns of Salmonella spp. isolated from 120 chicken carcasses produced in 6 poultry slaughterhouses in South Korea. A total of 11 samples (9.2%) were found contaminated with Salmonella: 5 isolates were serotyped as Salmonella Bellevue strain (slaughterhouse C) and 6 isolates were serotyped as Salmonella Enteritidis strain (slaughterhouse E). Salmonella Bellevue isolates were resistant to five antibiotics (ampicillin, chloramphenicol, nalidixic acid, tetracycline, and trimethoprim/sulfamethoxazole), while Salmonella Enteritidis isolates were resistant to nine antibiotics (ampicillin, cefotaxime, ceftazidime, cefazolin, cephalothin, amikacin, nalidixic acid, streptomycin, and tetracycline). All cephalosporin-resistant Salmonella Enteritidis isolates exhibited the extended-spectrum ß-lactamase (ESBL) phenotype and carried the gene encoding CTX-M-15, the most prevalent ESBL enzyme worldwide. Based on molecular subtyping performed using the automated rep-polymerase chain reaction (PCR) system (DiversiLab), the isolates showing ≥ 95 similarity in their rep-PCR banding patterns were classified into 5 pulsotypes. Given that cephalosporins are the drugs of choice for invasive Salmonella infections, the high incidence of ESBL-producing strains in chicken should emphasize the necessity of regular monitoring of the occurrence of antibiotic-resistant ESBL-positive Salmonella strains in poultry meat.

Quantitative Prevalence and Toxin Gene Profile of Bacillus cereus from Ready-to-Eat Vegetables in South Korea.

Ready-to-eat (RTE) foods such as prepared vegetables are becoming an increasingly popular food choice. Since RTE vegetables are not commonly sterilized by heat treatment, contamination with foodborne pathogens such as Bacillus cereus (B. cereus) is a major concern. The objective of this study was to assess the quantitative prevalence and toxin gene profiles of B. cereus strains isolated from RTE vegetables. We found that 70 of the 145 (48%) tested retail vegetable salad and sprout samples were positive for B. cereus. The B. cereus isolates harbored at least one enterotoxin gene. The detection rates of nheABC, hblCDA, cytK, and entFM enterotoxin genes among all isolates were 97.1%, 100%, 81.4%, and 98.6%, respectively. No strain carried the emetic toxin genes. Only 4 strains (5.7%) from the 70 isolates were psychrotrophic and were able to grow at 7°C. All of the psychrotrophic isolates possessed at least 1 enterotoxin gene.

Characterization of Escherichia coli-Producing Extended-Spectrum ß-Lactamase (ESBL) Isolated from Chicken Slaughterhouses in South Korea.

In South Korea, few reports have indicated the occurrence and characteristics of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli in food-producing animals, particularly in poultry slaughterhouses. In this study, we investigated the occurrence and antibiotic resistance of ESBL-producing E. coli from whole chicken carcasses (n=156) and fecal samples (n=39) of chickens obtained from 2 slaughterhouses. Each sample enriched in buffered peptone water was cultured on MacConkey agar with 2 mg/L cefotaxime and ESBL agar. ESBL production and antibiotic susceptibility were determined using the Trek Diagnostics system. The ESBL genotypes were determined by polymerase chain reaction (PCR) using the bla(SHV), bla(TEM), and bla(CTX-M) gene sequences. Subtyping using a repetitive sequence-based PCR system (DiversiLab™) and multilocus sequence typing (MLST) were used to assess the interspecific biodiversity of isolates. Sixty-two ESBL-producing E. coli isolates were obtained from 156 samples (39.7%). No bla(SHV) genes were detected in any of the isolates, whereas all contained the bla(TEM) gene. Twenty-five strains (40.3%) harbored the CTX-M group 1 gene. The most prevalent MLST sequence type (ST) was ST 93 (14.5%), followed by ST 117 (9.7%) and ST 2303 (8.1%). This study reveals a high occurrence and ß-lactams resistance rate of E. coli in fecal samples and whole chickens collected from slaughterhouses in South Korea.

Prevalence, characterization, and antimicrobial susceptibility of Salmonella Gallinarum isolated from eggs produced in conventional or organic farms in South Korea.

To determine the prevalence of Salmonella serotype Enteritidis in eggs in South Korea, we conducted a microbiological survey of commercially available eggs produced in conventional or organic farms during the period from 2010 to 2012. The contents of 7,000 raw shell eggs (6,000 of conventional and 1,000 of organic origin) were examined to evaluate the extent and type of Salmonella Enteritidis contamination. A total of 26 salmonellae (7.4% of all pooled samples) were isolated from 350 homogenized pools, each containing the contents from 20 eggs. An unexpected and particularly surprising finding was that all the Salmonella isolates were serotyped as Salmonella Gallinarum. Salmonella Gallinarum was more common in eggs from organic farms: 10 of 50 egg pools (20.0%) from organic and 16 of 300 egg pools (5.3%) from conventional farms tested positive for Salmonella Gallinarum. However, organic and conventional isolates showed similar antimicrobial susceptibilities. All the isolates and a vaccine strain, SG 9R, which has been widely used in South Korea, were further characterized using the automated repetitive sequence-based PCR (rep-PCR) system, DiversiLab, to ascertain the molecular subtypes and to identify differences from the vaccine strain. The rep-PCR identified 2 distinct clusters among the 26 Salmonella Gallinarum isolates with a greater than 96% similarity index. These were clearly differentiated from the vaccine strain, SG 9R, with which there was a less than 86% similarity index. We found there was low genetic heterogeneity among isolates within each cluster and were able to distinguish wild type strains from the live vaccine strain (SG 9R) using the DiversiLab system.

Identification and phylogenetic analysis of Enterococcus isolates using MALDI-TOF MS and VITEK 2.

The bacterial genus Enterococcus encompasses 38 species. Two of the most common species are E. faecalis and E. faecium. Recently, however, there has been an increase in clinical reports concerning less prevalent Enterococcus species, such as E. durans, E. hirae, and E. gallinarum. Rapid and accurate laboratory methods are needed to facilitate the identification of all these bacterial species. In the present study, we compared the relative accuracy of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), VITEK 2, and 16S rRNA gene sequencing using 39 enterococci isolates from dairy samples, and compared the resultant phylogenetic trees. We found that MALDI-TOF MS correctly identified all isolates at the species level except for one, whereas the VITEK 2 system, which is an automated identification system using biochemical characteristics of species, misidentified ten isolates. However, phylogenetic trees constructed from both methods showed all isolates in similar positions. Our results clearly showed that MALDI-TOF MS is a reliable and rapid tool for identifying Enterococcus species with greater discriminatory power than the biochemical assay method of VITEK 2.

Improvement of modified charcoal-cefoperazone-deoxycholate agar by supplementation with a high concentration of polymyxin B for detection of Campylobacter jejuni and C. coli in chicken carcass rinses.

Modified charcoal-cefoperazone-deoxycholate agar (mCCDA) was improved by supplementation with a high concentration of polymyxin B. The ability of the supplemented medium to isolate Campylobacter jejuni and C. coli from chicken carcass rinses was compared to that of Campy-Cefex agar and mCCDA. Modification of mCCDA with increased polymyxin B yielded a significantly (P < 0.05) higher isolation rate and greater selectivity than those achieved using Campy-Cefex agar and mCCDA.

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 ß-lactam antibiotics. By using the automated rep-PCR system, all isolates were successfully differentiated, indicating the diversity of B. cereus strains present in Sunsik.

Isolation and characterization of Shiga toxin-producing Escherichia coli (STEC) in retail edible beef by-products.

The prevalence of Shiga toxin-producing Escherichia coli (STEC) was investigated in 350 edible beef intestinal samples, including omasum (n=110), abomasum (n=120), and large intestines (n=120), collected from traditional beef markets in Seoul, Korea. A total of 23 STEC strains were isolated from 15 samples (four strains from three omasa, 10 from five abomasa, and nine from seven large intestines). The O serotypes and toxin gene types of all STEC isolates were identified, and antimicrobial resistance was assessed using the disk diffusion method. The isolation rates of STEC from edible beef intestines were 2.8% in omasum, 4.2% in abomasums, and 5.9% in large intestines. All STEC isolates harbored either stx1, or both stx1 and stx2 genes simultaneously. Among the 23 isolates, 13 strains were identified as 11 different O serogroups, and 10 strains were untypable. However, enterohemorrhagic Esherichia coli O157, O26, and O111 strains were not isolated. The highest resistance rate observed was against tetracycline (39%), followed by streptomycin (35%) and ampicillin (22%). Of the 23 isolates, 12 isolates (52%) were resistant to at least one antibiotic, nine (39%) isolates were resistant to two or more antibiotics, and one isolate from an abmasum carried resistance against nine antibiotics, including beta-lactam/beta-lactamase inhibitor in combination and cephalosporins. This study shows that edible beef by-products, which are often consumed as raw food in many countries, including Korea, can be potential vehicles for transmission of antimicrobial-resistant pathogenic E. coli to humans.

Properties of broiler breast meat with pale color and a new approach for evaluating meat freshness in poultry processing plants.

The current trend in monitoring meat quality is to move the quality measurements from the laboratory to the processing line. To provide better meat quality control in the commercial poultry processing plants, we evaluated the quality of broiler breast meat samples, observing different colors, and assessed their freshness using a Torrymeter. Different colors were classified based on the mean ± standard deviation of lightness (L*) values in 1,499 broiler breast fillets: Dark (L* < 56), normal (56 ≤ L* ≤ 62), and pale (L* > 62). To characterize the differences between the pale and normal color groups, we evaluated additional fillets for meat quality traits. Changes in meat quality during storage were also evaluated. The L* and Torrymeter values (freshness values) allowed us to distinguish between the pale and normal meat samples. Normal and pale fillets showed a significant difference in pH, Torrymeter values, and water-holding capacity (P < 0.001). The L* values were significantly correlated with cook and drip loss (P < 0.01) and were higher (paler, +1.2 L* unit) at 72-h postmortem than at 4-h postmortem. Torrymeter values were correlated with cook loss (P < 0.05) and pH (P < 0.001), and significantly decreased with the increase in storage period (P < 0.001). These results suggest the applicability of the Torrymeter, a fast and non-destructive device, in distinguishing stale and fresh breast fillets. With its portability and simplicity, the Torrymeter is expected to be a valuable tool to estimate meat freshness. Especially, the use of Torrymeter for evaluating pale breast fillets may allow easy identification and separation of fillets according to their pale, soft, and exudative properties in commercial poultry processing lines.

Distribution and Characterization of Antimicrobial Resistant Pathogens in a Pig Farm, Slaughterhouse, Meat Processing Plant, and in Retail Stores.

The emergence of antibiotic resistance in foodborne pathogens isolated from meat pro-ducts and their producing environment has been an increasing and leading threat to public health. The aim of the study was to identify pathogens and their antimicrobial resistance isolated from pig production to pork meat distribution phases. Through this study, food spoilage and foodborne or clinical pathogenic bacteria were isolated and identified from pork (belly and neck) meat product and its related environmental samples that include pig swabs, diets, feces, liquid manure, workers' gloves, dust fan swabs, carcass swabs, floor swabs, and drain water in the affiliated farm, slaughterhouse, meat processing plant, and in retail stores. All carcasses at the slaughterhouse and meat products at the meat processing plant were tracked from pigs at a targeted farm. Nine different selective media agars were used to effectively isolate various pathogenic bacteria. A total of 283 presumptive pathogenic bacteria isolated from 126 samples were selected and identified using MALDI-ToF MS. Twenty-three important foodborne pathogens were identified, and some of them, Shiga-toxin-producing E. coli (STEC), Listeria monocytogenes, Staphylococcus aureus, and Yersinia enterocolitica, were further confirmed using PCR. The PFGE patterns of 12 STEC isolates were grouped by sample source or site. All the foodborne pathogens used in the study were not resistant to amoxicillin/clavulanate, ciprofloxacin, and gentamicin, whereas some of the STEC, L. monocytogenes, and S. aureus isolates were resistant to various antibiotics, including ampicillin, erythromycin, tetracycline, and vancomycin. The most common antimicrobial resistance pattern in the pathogenic STEC isolates was AMP-KAN-STR-SXT-TET. Consequently, this study provides valuable information for the distribution of antimicrobial-resistant pathogens along the pork meat production chain and can assist farmers and stakeholders to develop a systematic strategy for reducing the current emergence and spread of antimicrobial resistance in the different phases of pig production and distribution.

Evaluation of Ceftazidime as an Antibiotic Supplement in Mannitol-Yolk-Polymyxin B Agar Used for Enumeration of Bacillus cereus in Ready-to-Eat Vegetables.

ABSTRACT: The Bacillus cereus group of bacteria, which causes foodborne diseases, can be detected by culture on selective media. However, the presence of competing flora is the most common factor preventing the accurate enumeration of B. cereus on selective agars. In this study, we improved the selectivity of mannitol-yolk-polymyxin B agar (MYPA) and its modified version containing trimethoprim (mMYPA) developed in our previous study by supplementation with ceftazidime (16 µg/mL). Ceftazidime-supplemented MYPA (C-MYPA16) and mMYPA (C-mMYPA16) were evaluated for bacteria recovery and selectivity with three types of ready-to-eat vegetables. Four B. cereus and one Bacillus thuringiensis strains were mixed and artificially inoculated into vegetable salad, radish sprouts, and sprout mix and then recovered on MYPA, mMYPA, C-MYPA16, and C-mMYPA16. In all tested vegetables, mMYPA, C-MYPA16, and C-mMYPA16 culture resulted in similar recovery of B. cereus and B. thuringiensis (P > 0.05), whereas radish sprout and sprout mix colonies grown on MYPA were undistinguishable. C-mMYPA16 was the most selective medium because it eliminated most of the competing flora, especially that in sprouts, without negatively affecting the recovery of B. cereus and B. thuringiensis. Our results indicate that supplementation of mMYPA with ceftazidime may improve the selectivity of this medium for B. cereus and B. thuringiensis in food testing.