The effect of concomitant use of systemic antibiotics in patients with Clostridium difficile infection receiving metronidazole therapy.

Management of Clostridium difficile infection (CDI) involves discontinuation of the offending antibiotic agent as soon as possible. However, the ongoing infection does not allow discontinuation of the offending antibiotic. We aimed to retrospectively investigate the predictors of treatment failure and impact of the concomitant use of systemic antibiotics in patients receiving metronidazole therapy. This study was conducted among patients hospitalised at a second care academic hospital from January 2013 to December 2014. Eligible patients were identified by reviewing stool toxin enzyme immunoassay results for C. difficile. Diarrhoea was defined as the passage of at least three loose or watery stools within 24 h. Among 314 patients with CDI receiving metronidazole therapy, 62 (19.7%) showed treatment failure and 105 (33.4%) received concomitant antibiotics. Underlying dialysis, fever >38.3 °C, low median serum albumin levels and concomitant use of antibiotics were independent predictors of treatment failure in patients with CDI receiving metronidazole therapy. The concomitant use of antibiotics increased the rates of treatment failure and 30-day mortality in patients receiving metronidazole therapy. These results suggest that metronidazole should be used in mild cases of CDI only after discontinuation of the offending antibiotics.

Comparison of the loads and antibiotic-resistance profiles of Enterococcus species from conventional and organic chicken carcasses in South Korea.

Antibiotic-resistant bacteria in poultry meat are a threat to public health. In this study, we compared the Enterococcus spp. loads and antibiotic-resistance profiles between carcasses of conventionally and organically raised chickens. A total of 144 chicken carcasses (72 conventional and 72 organic) was collected from local retail markets in Seoul, South Korea. Overall, 77.7% (112 of 144; 75% conventional and 80% organic) of chicken carcasses were positive for Enterococcus. The mean loads of Enterococcus spp. were greater in conventional chicken carcasses, at 2.9 ± 0.4 log CFU/mL, than those in organic chicken carcasses, at 1.78 ± 0.3 log CFU/mL (p < 0.05). A total of 104 isolates (52 from conventional and 52 from organic chicken carcasses) was randomly selected for further analysis. The predominant species was Enterococcus faecalis in both conventional and organic chicken carcasses (57.7 and 76.9%, respectively; P > 0.05). Rates of resistance to ciprofloxacin and erythromycin, which are used in veterinary medicine in South Korea, were significantly higher in conventional chicken carcasses than in organic chicken carcasses. However, we found no difference between the rates of resistance to antibiotics such as vancomycin and tigecycline, which were not registered for use in veterinary medicine in South Korea, of Enterococcus isolates from conventional and organic chicken carcasses. In addition, although multidrug resistant isolates were obtained from both types of chicken samples, the prevalence of samples positive for Enterococcus was significantly higher in conventional chicken carcasses than in organic chicken carcasses (P < 0.05). The most common multidrug resistance pattern was erythromycin-tetracycline-rifampicin in conventional chicken carcasses and quinupristin-dalfopristin-tetracycline-rifampicin in organic chicken carcasses. A high level of gentamicin resistance was observed in isolates from not only conventional (5.8%) but also organic chicken (1.9%) carcasses, with no significant difference in rates between them (P > 0.05). Despite this, our results suggest that organic food certification is effective in reducing fecal contamination and the burden of antibiotic-resistant Enterococcus spp. in chicken carcasses.

Comparison of the isolation rates and characteristics of Salmonella isolated from antibiotic-free and conventional chicken meat samples.

Salmonella contamination in chicken samples can cause major health problems in humans. However, not only the effects of antibiotic treatment during growth but also the impacts of the poultry slaughter line on the prevalence of Salmonellae in final chicken meat sold to consumers are unknown. In this study, we compared the isolation rates and antimicrobial resistance of Salmonellae among antibiotic-free, conventional, conventional Korean native retail chicken meat samples, and clonal divergence of Salmonella isolates by multilocus sequence typing. In addition, the distribution of extended-spectrum ß-lactamase (ESBL) genes in ESBL-producing Salmonella isolates was analyzed. A total of 72 retail chicken meat samples (n = 24 antibiotic-free broiler [AFB] chickens, n = 24 conventional broiler [CB] chickens, and n = 24 conventional Korean native [CK] chickens) was collected from local retail markets in Seoul, South Korea. The isolation rates of Salmonellae were 66.6% in AFB chickens, 45.8% in CB chickens, and 25% in CK chickens. By analyzing the minimum inhibitory concentrations of ß-lactam antibiotics with the disc-diffusion test, we found that 81.2% of Salmonella isolates from AFB chickens, 63.6% of isolates from CB chickens, and 50% of isolates from CK chickens were ESBL producers; all ESBL-positive isolates had the CTX-M-15 genotype. Interestingly, all ESBL-producing Salmonellae were revealed as ST16 by multilocus sequence typing and had the genetic platform of blaCTX-M gene (IS26-ISEcp1-blaCTX-M-15-IS903), which was first reported in Salmonellae around the world. The Salmonella ST33 strain (S. Hadar) isolated in this study has never been reported in South Korea. In conclusion, our findings showed that antibiotic-free retail chicken meat products were also largely contaminated with ESBL-producing Salmonellae and that their ESBL genes and genetic platforms were the same as those isolated from conventional retail chicken meat products.

Hepatoprotective and neuroprotective tocopherol analogues isolated from the peels of Citrus unshiu Marcovich.

Three tocopherol analogues methoxytocopherol (1), α-tocopherol (2) and γ-tocopherol (3) were isolated from the peels of Citrus unshiu Marcovich. The protective effects of the isolated compounds against tert-butyl hydroperoxide-induced hepatotoxicity in human liver-derived HepG2 cells and glutamate-induced oxidative stress in HT22-immortalised hippocampal cells were evaluated. Compounds 1-3 were significantly protective in HepG2 cells with EC50 values of 21.22 ± 2.01, 25.21 ± 2.11 and 25.25 ± 1.21 µM, respectively, and in HT22 cells, compounds 1-3 had EC50 values of 20.62 ± 1.36, 6.44 ± 1.65 and 9.52 ± 1.54 µM, respectively.

Comparison of 2 types of broths and 3 selective agars for the detection of Campylobacter species in whole-chicken carcass-rinse samples.

In this study, we compared the effectiveness of 2 types of Bolton broths and 3 selective media for isolating Campylobacter spp. from naturally contaminated whole-chicken carcass-rinse samples. One hundred chickens were rinsed with buffered peptone water, and the rinses were added to 2× Bolton broth (with or without blood supplementation). The samples were incubated and then streaked onto Preston agar, modified cefoperazone charcoal deoxycholate agar (mCCDA), and Campy-Cefex agar, which was followed by incubation under microaerobic conditions. No statistical differences were observed (P > 0.05) in isolation rate and selectivity between the 2 types of Bolton broths. Among the 3 selective agars, Preston agar yielded a significantly (P < 0.05) better isolation rate and selectivity. The Campy-Cefex agar, which is recommended by many food authorities for its high quantitative detection ability, showed extensive contamination with competing microorganisms and exhibited the lowest isolation rate and selectivity.

Evaluation of selective enrichment broths and chromogenic media for Salmonella detection in highly contaminated chicken carcasses.

We evaluated the effectiveness of 2 selective enrichment broths, Rappaport-Vassiliadis Soy (RVS) and Muller-Kauffmann tetrathionate with novobiocin (MKTTn), for the isolation of Salmonella from chicken carcasses obtained from 3 different types of retail markets. We also compared a chromogenic agar, chromID Salmonella agar (SM-ID 2), with a classic plating medium, xylose lysine deoxycholate agar (XLD). Salmonella were isolated from 118 of the 180 samples (65.5%). Salmonella were detected in 105 samples (88%) plated on XLD and 111 samples (94%) plated on SM-ID 2 when RVS broth was used for enrichment, and 43 samples (36.4%) plated on XLD and 67 samples (56.8%) plated on SM-ID 2 when the MKTTn broth was used. The highest sensitivity was found in the RVS-XLD combination (0.99), followed by RVS-SM-ID 2 (0.97). The specificity of the RVS-SM-ID 2 combination was the highest (0.89), but that of the MKTTn-XLD combination was zero. The results of this study indicate that the selective enrichment broths had a great effect on the sensitivity and specificity of plating media, and our study confirms that the RVS broth is the most suitable enrichment for the investigation of Salmonella in chicken carcasses. This observation suggests that use of RVS broth for selective enrichment and SM-ID 2 for selective isolation may be the best combination to determine the presence of Salmonella in chicken carcasses.

Prevalence, phenotypic traits and molecular characterization of emetic toxin-producing Bacillus cereus strains isolated from human stools in Korea.

AIMS: To investigate the prevalence and genotypic/phenotypic characters of emetic toxin-producing Bacillus cereus strains isolated from sporadic food poisoning cases in Korea. METHODS AND RESULTS: The prevalence of emetic B. cereus was determined in 56 899 stool samples from sporadic food poisoning cases in Korea between 2004 and 2006. We assessed toxin profiles, phenotypic traits and antibiotic resistance. The molecular subtyping was ascertained using an automated repetitive sequence-based PCR (rep-PCR) system, DiversiLab™, with these emetic strains isolated from sporadic food poisoning cases and other emetic strains isolated from an outbreak and food samples. Emetic B. cereus was present in 0·012% of sporadic food poisoning cases. The prevalence of nheABC, hblCDA, cytK and entFM enterotoxin genes among emetic strains was 100, 14·3, 14·3 and 100%, respectively. Most emetic strains were negative for salicin hydrolysis (100%), starch fermentation (85·7%) and haemolysis (85·7%). One emetic isolate, VK7, exhibited several unique traits, such as harbouring the hbl gene and ability to hydrolyse starch. All isolated strains were highly resistant to ß-lactam antibiotics. All emetic strains except VK7 exhibited an identical rep-PCR banding pattern, while nonemetic strains were classified into various pulsotypes. CONCLUSIONS: Most emetic strains except one isolate exhibited similar genotypic/phenotypic traits and subtyping pattern. Automatic rep-PCR (DiversiLab™) may be used to discriminate emetic strains from nonemetic strains, although we could not distinguish between most emetic strains using that. SIGNIFICANCE AND IMPACT OF THE STUDY: Result of this study may contribute an extended database on the prevalence and toxigenic traits of emetic B. cereus strains isolated from Korea.

Evaluation of the efficacy of immunocastration vaccine composed of gonadotrophin-releasing hormone conjugated with Salmonella typhimurium flagellin in rats.

Immunocastration is an alternative method to replace surgical castration that is commonly performed in domestic and pet animals. In this study, a new immunocastration vaccine was developed, and its efficacy was evaluated in male rats. Six tandem copies of gonadotrophin-releasing hormone (GnRH) peptide were genetically fused to Salmonella typhimurium flagellin fljB (STF2) that is a ligand of toll-like receptor 5 (TLR5). The recombinant STF2-GnRH protein expressed in Escherichia coli was used as the immunocastration vaccine. Sixteen male rats were equally assigned to four groups. Excluding the control rats, three groups were immunized with 100, 200 and 400 µg of the STF2-GnRH vaccine, respectively. All of the immunized rats developed significantly higher titres of antibodies to GnRH than the control rats. The size and weight of both testes and epididymides from the immunized rats were significantly smaller than those of the control rats. Testicular tissues in the immunized rats demonstrated atrophy of seminiferous tubules and decreased numbers of both spermatogonia and spermatocytes. These data indicate that the newly developed STF2-GnRH vaccine has a potent immunogenicity to GnRH and efficiently suppresses the development of testes in rats.

Pretreatment of polyethylene terephthalate substrate for the growth of Ga-doped ZnO thin film.

The effect of the pretreatment of polyethylene terephthalate (PET) substrate on the growth of transparent conducting Ga-doped ZnO (GZO) thin film was investigated. Because of its high gas and moisture absorption and easy gas permeation, PET substrate was annealed at 100 degrees C in a vacuum chamber prior to the sputtering growth of GZO thin film for the outgassing of impurity gases. GZO thin film was deposited on the pretreated PET substrate by rf-magnetron sputtering and significantly improved electrical properties of GZO thin film was achieved. Electrical and structural characterizations of the GZO thin films were carried out by 4-point probe, Hall measurement, and scanning electron microscopy, and the effects of the pretreatment on the improved properties of GZO thin films were discussed. This result is not only useful to PET substrate, but also could be applicable to other plastic substrates which inevitably containing the moisture and impurity gases.

Production and characterization of a monoclonal antibody to Campylobacter jejuni.

Campylobacter species are a group of spiral-shaped bacteria that can cause disease in humans and animals. We developed a high-affinity monoclonal antibody (MAb) probe that recognizes Campylobacter jejuni cells. Cell suspensions grown under microaerobic conditions at 42 degrees C for 20 h on Bolton agar plates with lysed horse blood were used as live and heat-killed preparations, centrifuged at 8,000 x g for 20 min, and resuspended in carbonate buffer (pH 9.6) for coating on the enzyme-linked immunosorbent assay plates. BALB/c mice were immunized with C. jejuni sonicated cells at 10(7) CFU/ml to generate MAb-producing hybridoma clones. Of about 500 initial hybridoma clones, MAb 33D2, which reacted with C. jejuni and Campylobacter coli, was selected for further evaluation. MAb 33D2 is in the immunoglobulin subclass G2a and had relatively weaker reactivity with the C. coli strains tested. MAb 33D2 did not show any cross-reactions with the nine non-Campylobacter bacteria tested in the enzyme-linked immunosorbent assay and had a stronger affinity for C. jejuni as live versus heat-killed cells. In Western blot assays, MAb 33D2 recognized two major antigens of 62 and 43 kDa in extracts from C. jejuni cells but only one antigen of 62 kDa in extracts from C. coli cells.

Reporting 678 putative cSNPs from full-length enriched cDNA sequences of the Korean native pig.

Sequences from the clones of full-length enriched cDNA libraries serve as valuable resources for functional genomic studies. We have analysed 1970 high-quality chromatograms (Phred value >or= 30) that were obtained from sequencing the 5' ends of brainstem, liver, neocortex and spleen clones derived from full-length enriched cDNA libraries from Korean native pigs. In addition, 50,000 pig expressed sequence tag (EST) sequence trace files were obtained from Genbank and combined with our sequencing information to facilitate SNP identification in silico. The process generated 8118 contigs, of which 239 included minimum one sequence from Korean native pig and contained 678 putative coding single nucleotide polymorphisms (cSNPs). Of these, 33 putative cSNPs were randomly selected for confirmatory analysis and validated using 20 pigs from four different breeds (Duroc, Landrace, Yorkshire, Korean native pig). Of the 33 putative cSNPs, 20 were confirmed (61%), which was similar to the frequency reported in other studies. We also identified 15 new cSNPs from the validation process, which were not detected by our in silico analysis. Our study shows that analysing genetically diverse pig breeds including the Korean native pig could serve as a useful strategy for generating a large number of cSNPs.

Prevalence of hepatitis E virus and sapovirus in post-weaning pigs and identification of their genetic diversity.

Hepatitis E virus (HEV) and sapovirus (SaV) induce acute hepatitis and gastroenteritis, respectively, in humans. As pigs have been recognized as an important reservoir for these viruses, we evaluated the infection rates of both viruses using fecal samples collected from post-weaning pigs via RT-PCR methods. In the five swine farms assessed in this study, 3 farms were found to be HEV-positive and 4 farms were SaV-positive. The overall prevalence of HEV and SaV in the pigs was 17.0 and 23.1%, respectively. Phylogenetic tree analysis revealed that the isolated swine HEVs belonged to genotype 3 and the porcine SaVs belonged to genogroup III. This study proved that both HEV and SaV are prevailing in post-weaning pigs in Korea.

A new HLA-A*24 variant, A*2475, identified by sequence-based typing in the Korean population.

A novel human leukocyte antigen (HLA) A*24 allele was identified in the Korean population and designated HLA-A*2475. The HLA-A*2475 allele shows one nucleotide difference from A*24020101 in exon 3 at nucleotide position 575 (T-->C), resulting in an amino acid change, Leu168Arg.

Identification of Salmonella enterica serovar Typhimurium using specific PCR primers obtained by comparative genomics in Salmonella serovars.

Salmonella enterica serovar Typhimurium is a major foodborne pathogen throughout the world. Until now, the specific target genes for the detection and identification of serovar Typhimurium have not been developed. To determine the specific probes for serovar Typhimurium, the genes of serovar Typhimurium LT2 that were expected to be unique were selected with the BLAST (Basic Local Alignment Search Tool) program within GenBank. The selected genes were compared with 11 genomic sequences of various Salmonella serovars by BLAST. Of these selected genes, 10 were expected to be specific to serovar Typhimurium and were not related to virulence factor genes of Salmonella pathogenicity island or to genes of the O and H antigens of Salmonella. Primers for the 10 selected genes were constructed, and PCRs were evaluated with various genomic DNAs of Salmonella and non-Salmonella strains for the specific identification of Salmonella serovar Typhimurium. Among all the primer sets for the 10 genes, STM4497 showed the highest degree of specificity to serovar Typhimurium. In this study, a specific primer set for Salmonella serovar Typhimurium was developed on the basis of the comparison of genomic sequences between Salmonella serovars and was validated with PCR. This method of comparative genomics to select target genes or sequences can be applied to the specific detection of microorganisms.

Detection and enumeration of Salmonella enteritidis in homemade ice cream associated with an outbreak: comparison of conventional and real-time PCR methods.

Salmonellosis caused by Salmonella Enteritidis (SE) is a significant cause of foodborne illnesses in the United States. Consumption of undercooked eggs and egg-containing products has been the primary risk factor for the disease. The importance of the bacterial enumeration technique has been enormously stressed because of the quantitative risk analysis of SE in shell eggs. Traditional enumeration methods mainly depend on slow and tedious most-probable-number (MPN) methods. Therefore, specific, sensitive, and rapid methods for SE quantitation are needed to collect sufficient data for risk assessment and food safety policy development. We previously developed a real-time quantitative PCR assay for the direct detection and enumeration of SE and, in this study, applied it to naturally contaminated ice cream samples with and without enrichment. The detection limit of the real-time PCR assay was determined with artificially inoculated ice cream. When applied to the direct detection and quantification of SE in ice cream, the real-time PCR assay was as sensitive as the conventional plate count method in frequency of detection. However, populations of SE derived from real-time quantitative PCR were approximately 1 log higher than provided by MPN and CFU values obtained by conventional culture methods. The detection and enumeration of SE in naturally contaminated ice cream can be completed in 3 h by this real-time PCR method, whereas the cultural enrichment method requires 5 to 7 days. A commercial immunoassay for the specific detection of SE was also included in the study. The real-time PCR assay proved to be a valuable tool that may be useful to the food industry in monitoring its processes to improve product quality and safety.

Optimization of ferrioxamine E concentration as effective supplementation for selective isolation of Salmonella enteritidis in egg white.

Utilization of ferrioxamine E (FE) as a sole source of iron distinguishes Salmonella from a number of related species, including Escherichia coli. FE is not able to serve as a source of iron for E. coli or the Proteus-Providencia-Morganella group. This confers a selective advantage on Salmonella Enteritidis in egg white supplemented with FE. The optimum concentration of FE that promoted a selective advantage for Salmonella in egg white was determined. Four supplementation concentrations were evaluated (25, 50, 200, and 500 microg/ml) in egg white artificially inoculated with proportionally mixed cultures of a rifampin-resistant strain of Salmonella Enteritidis (0.1 ml of 102 CFU/ml) and E. coli K-12 (0.1 ml of 10(1) through 10(8) CFU/ml). After a 24-h incubation at 37 degrees C, Salmonella and E. coli populations were enumerated. At higher concentrations of FE (>50 microg/ml), both Salmonella and E. coli were able to use the iron supplement (1 to 8.5 log CFU/ml and 1.8 to 8 log CFU/ml, respectively); however, lower FE concentrations (< or = 50 microg/ml) exclusively promoted Salmonella growth. Salmonella was unrecoverable without supplementation. This study indicates that optimum levels of FE supplementation in egg can improve the selective detection for Salmonella Enteritidis among other competitive organisms.

Rapid, specific detection of Enterobacter sakazakii in infant formula using a real-time PCR assay.

Enterobacter sakazakii is a rare cause of invasive infection with high mortality rates in neonates. Powdered milk-based infant formulas have been associated with the E. sakazakii-related outbreaks in premature or other immunocompromised infants. In this study, an assay was developed for the specific detection of E. sakazakii in infant formula using an application of the fluorogenic 5' nuclease assay (TaqMan). A set of primers and probe was designed using the E. sakazakii partial macromolecular synthesis operon: the rpsU gene 3' end and the primase (dnaG) gene 5' end. The specificity of the assay was evaluated using 68 Enterobacter and 55 non-Enterobacter strains. The newly developed assay enables us to detect 100 CFU/ ml in pure culture and in reconstituted infant formula in 50 cycles of PCR without enrichment. The assay was specific enough to discriminate E. sakazakii from all other Enterobacter and non-Enterobacter strains tested. The developed real-time PCR assay could save up to 5 days and eliminate the need for plating samples on selective or diagnostic agars and for biochemical confirmation steps. The real-time PCR assay could be used to rapidly screen infant formula samples for E. sakazakii and would be a boon to food industries and regulatory agencies.

Rapid, specific detection of Salmonella Enteritidis in pooled eggs by real-time PCR.

An assay was developed for the specific detection of Salmonella Enteritidis in eggs with the use of an application of the fluorogenic 5' nuclease assay (TaqMan). In this assay, a segment of the gene sefA specific to Salmonella group D strains such as Salmonella Enteritidis was used. The amplification of the target gene products was monitored in real-time by incorporating a fluorescent dye-labeled gene-specific probe in the PCR reaction. This method correctly detected and distinguished Salmonella Enteritidis from nearly 50 of non-group D Salmonella and other non-Salmonella strains. Detection of the sefA gene was linear for DNA extracted from approximately 10(2) to 10(9) CFU/ml in phosphate-buffered saline and 10(3) to 10(8) CFU/ml in raw egg. In two trials, when applied to detection of Salmonella Enteritidis in homogenized egg pools and compared with conventional culture methods, the newly developed PCR method yielded a 100% correlation with results obtained by a conventional culture method. However, the PCR method required only 2 days, compared to the 5 days required by the culture method. The sensitivity of this assay was approximately less than 1 CFU/600 g of egg pool. The real-time PCR assay proved to be a rapid, highly sensitive test for detection and quantification of low concentrations of Salmonella Enteritidis in egg samples.

Comparison of homogenization methods for recovering Salmonella Enteritidis from eggs.

For Salmonella Enteritidis (SE) detection, shell eggs have been homogenized with stomachers, with electric blenders, and by hand massaging. However, to date, there have been no published reports addressing whether the method of homogenization affects the recovery of SE from raw eggs. Three inoculum levels (10, 126, and 256 SE cells per pool of 10 eggs) were used to conduct three experiments. The 10-egg pools were homogenized by one of four homogenization methods--mechanical stomaching, electric blending, hand massaging, and hand stirring-for 30 s. The homogenized eggs were then incubated at 37 degrees C, and SE colonies were enumerated after 24 and 48 h of incubation. After 24 h of incubation, no SE was recovered from egg samples from stomached or electrically blended pools inoculated with <10 cells, while levels of 106 CFU/ml were found for samples from whipped or hand-massaged pools inoculated with <10 cells. Similarly, after 24 h of incubation, the numbers of SE cells recovered from hand-massaged or hand-stirred egg pools inoculated with 126 cells were significantly larger than the numbers recovered from stomached or electrically blended egg pools inoculated with 126 cells. The number of SE cells recovered from samples homogenized with a blender was still significantly smaller than the numbers recovered from samples homogenized by the other three methods when the inoculum level was increased to 256 CFU per pool. However, the SE count for all samples approached 9 log10 CFU/ml after 48 h of incubation. It is concluded that the detection of small SE populations in shell egg samples could be improved with the use hand massaging and hand stirring for homogenization.

Preenrichment versus direct selective agar plating for the detection of Salmonella Enteritidis in shell eggs.

The relative effectiveness of two methods for the recovery of Salmonella Enteritidis (SE) from jumbo and medium shell eggs was compared. The first method used in the comparison consisted of a preenrichment of the sample, and the second method was developed by the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). Three bulk lots of blended, pooled eggs, each containing 220 liquid whole eggs that were thoroughly mixed manually were artificially inoculated with different levels of SE cells between approximately 10(0) and 10(3) CFU/ml. Twenty samples containing the contents of approximately 10 eggs each (by weight) were withdrawn from each of the inoculated bulk lots and incubated for 4 days at room temperature (ca. 23 degrees C). For the APHIS method, each sample was cultured by direct plating onto brilliant green (BG), brilliant green with novobiocin (BGN), xylose lysine desoxycholate (XLD), and xylose lysine agar Tergitol 4 (XLT4) agars. For the preenrichment method, 25-g portions from each pool were enriched in modified tryptic soy broth with 30 mg/liter of FeSO4. After 24 h of incubation, the preenrichments were subcultured to tetrathionate and Rappaport-Vassiliadis broths, and streaked to BG, BGN, bismuth sulfite, XLD, and XLT4 agar plates. SE isolates were confirmed biochemically and serologically. In all of the experiments, the preenrichment method recovered significantly more SE isolates (P < 0.05) of all the phage types and inoculum levels than did the APHIS method. From a total of 539 jumbo egg test portions analyzed, 381 (71%) were SE-positive by the preenrichment method and 232 (43%) were positive by the APHIS method. From a total of 360 medium egg test portions analyzed, 223 (62%) were SE-positive by the preenrichment method and 174 (48%) were positive by the APHIS method. The preenrichment method provided greater sensitivity for the isolation of SE in contaminated egg slurries than did the APHIS method.