Evaluation of radiolabeled and colorimetric DNA probes in comparison with an antigen screening assay for the detection of Salmonella from poultry farms

A total of 48 environmental drag-swab samples from various poultry farms were tested for the presence of Salmonella spp. by culture, an enzyme-linked immunosorbent assay-based Salmonella antigen screening (SAS) assay, and two DNA probes (radiolabeled and colorimetric). The radiolabeled DNA probe was allowed to hybridize with culture-positive samples (n = 8) and was found to detect Salmonella spp. in all cases (100%). Both of the probes, subsequently hybridized with culture-negative samples (n = 8), were observed to yield good agreement (91%) with the culture findings. The remaining samples (n = 32) were tested by the SAS assay, and where there was no agreement between the culture and SAS, samples were further examined by the DNA probes. Results using both probes agreed with those obtained by culturing the samples but did not agree with the SAS assay result when the ratio of samples tested to samples positive (S/P) cutoff value used was 0.5.     

Polymerase chain reaction detection of Salmonella spp. in fecal samples of pet birds

The aims of this study were 1) to determine the prevalence of Salmonella in clinically ill birds in aviaries in Ankara, Turkey, and 2) to compare conventional culture and polymerase chain reaction (PCR) for detection of Salmonella in feces from clinically ill pet birds. In the study, 185 fecal samples (feces and/or swabs) collected from the pet birds kept in the seven different aviaries in the city of Ankara were investigated for the existence of Salmonella spp. by bacterial isolation and PCR. The conventional isolation and identification methods were performed for Salmonella isolation from fecal cultures. Suspected colonies were confirmed with the Salmonella polyvalent O antiserum and serogrouped with Salmonella group-specific antiserum. PCR was performed after the fecal swabs were incubated for 18 hr in 10 ml of tetrathionate broth. Three (1.63%) out of 185 fecal samples were found to harbor Salmonella spp. by conventional identification tests and were found to belong to serogroup B. Five (2.7%) swab samples were found to harbor Salmonella DNA by PCR tests. As a conclusion, PCR following incubation of clinical samples in pre-enrichment broth seemed to be a fast and practicable method for Salmonella spp. diagnosis when compared to protracted labor-intensive conventional culture techniques.     

Salmonella surveillance in a herd of asymptomatic captive black rhinoceros (Diceros bicornis) using fecal culture and PCR.

Feces were collected from captive black rhinoceros (Diceros bicornis minor) housed at Disney's Animal Kingdom to examine the frequency of Salmonella spp. shedding in asymptomatic animals using enrichment culture and broth culture- polymerase-chain-reaction (PCR) for detection. Three samples per animal were collected during the first week of each month between February 2001 and December 2003. During the study period, six different individual animals from one herd participated in the study, including two growing calves. A total of 550 cultures, using duplicate samples at two different laboratories, and 464 PCR tests were performed. When culture and PCR results were compared by the same laboratory, similar herd prevalence was found (2.4% positive cultures compared with 2.6% positive PCR tests). However, even though tests were performed on replicate samples, not every sample that was positive by culture was positive by PCR and vice versa. These results suggest that using multiple diagnostic methods and increasing the number of samples submitted may increase the likelihood of finding an asymptomatic Salmonella shedder. Although all of the rhinos shared the same environment throughout the study period, only four out of the six animals tested shed Salmonella spp. even though a minimum of 37 fecal samples were taken from each of the negative animals. Although this study followed a small number of rhinoceros, it suggests that asymptomatic shedding probably occurs more frequently in captive black rhinoceros than was previously believed. The prevalence appears to be similar to that reported for domestic ungulates.     

Comparison of rectal mucosal cultures and fecal cultures in detecting Salmonella infection in horses and cattle

Bacteriologic cultures of 65 rectal mucosal samples and 335 fecal samples from 53 horses and 5 cattle shedding Salmonella were performed. Salmonella spp were isolated from 34 (52%) rectal mucosal samples, 21 (32%) concurrent fecal samples, and 150 (45%) total fecal samples. The use of rectal mucosal samples when compared with concurrently obtained fecal samples significantly (P less than 0.025) improved the ability to isolate Salmonella spp. Concurrent bacteriologic culture of rectal mucosal samples and fecal samples resulted in 39 (60%) isolations. Compared with a series of fecal samples, Salmonella was isolated significantly more often when rectal mucosa and feces were cultured concurrently. Salmonella was isolated from rectal mucosal samples when it was not isolated from feces.     

Identification of sources of Salmonella organisms in a veterinary teaching hospital and evaluation of the effects of disinfectants on detection of Salmonella organisms on surface materials

OBJECTIVE: To determine sources of Salmonella organisms in a veterinary teaching hospital, compare bacterial culture with polymerase chain reaction (PCR) testing for detection of Salmonella organisms in environmental samples, and evaluate the effects of various disinfectants on detection of Salmonella organisms on surface materials. DESIGN: Prospective study. SAMPLE POPULATION: Fecal samples from 638 hospitalized horses and 783 environmental samples. PROCEDURE: Standard bacterial culture techniques were used; the PCR test amplified a segment of the Salmonella DNA. Five disinfectants were mixed with Salmonella suspensions, and bacterial culture was performed. Swab samples were collected from 7 surface materials after inoculation of the surfaces with Salmonella Typhimurium, with or without addition of a disinfectant, and submitted for bacterial culture and PCR testing. RESULTS: Salmonella organisms were detected in fecal samples from 35 (5.5%) horses. For environmental samples, the proportion of positive bacterial culture results (1/783) was significantly less than the proportion of positive PCR test results (110/783), probably because of detection of nonviable DNA by the PCR test. Detection of Salmonella organisms varied with the surface material tested, the method of detection (bacterial culture vs PCR testing), and the presence and type of disinfectant. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggested that Salmonella organisms can be isolated from feces of hospitalized horses and a variety of environmental surfaces in a large animal hospital. Although recovery of Salmonella organisms was affected by surface material and disinfectant, bleach was the most effective disinfectant on the largest number of surfaces tested.     

HRP直接标记属特异性基因探针检测沙门氏菌的研究

以活化辣根过氧化物酶复合物（ＨＲＰ—ＰＢＱ—ＰＥＩ＋—ＮＨ３＋）直接标记沙门氏菌属特异性ＤＮＡ探针ｐＬＳ２和ｐＬＳ３，探针与靶ＤＮＡ杂交后催化发光底物，经增强型化学发光反应（ＥＣＬ），用普通Ｘ光胶片自显影（ＣＰＤ）检测沙门氏菌。经狭缝杂交（Ｓｌｏｔｂｌｏｔ），该法标记探针均可检测到０．１ｐｇ的纯质粒ＤＮＡ及１０３个未经培养的鼠伤寒沙门氏菌。Ｄｏｔ—ｂｌｏｔ杂交结果证明，ＨＲＰ标记的探针仅与沙门氏菌属细菌杂交，而与试验的其他肠道非沙门氏菌不杂交。本研究表明，ＨＲＰ直接标记基因探针化学发光自显影法检测沙门氏菌，安全、快速、简便，且有高度的敏感性和特异性，是一种有较大应用前景的非放射性标记探针杂交检测方法。     

Detection of Salmonella organisms and assessment of a protocol for removal of contamination in horse stalls at a veterinary teaching hospital

OBJECTIVES: To assess methods of detecting environmental contamination with Salmonella organisms and evaluate a cleaning and disinfection protocol for horse stalls in a veterinary teaching hospital. DESIGN: Original study. SAMPLE POPULATION: 37 horses with diarrhea likely to be caused by Salmonella infection and their stall environments. PROCEDURES: Fecal samples were collected from horses daily during hospitalization; samples were obtained from stall sites after cleaning and application of disinfectants. Fecal and environmental samples were cultured for Salmonella spp and tested via polymerase chain reaction (PCR) assay to detect Salmonella DNA. RESULTS: 1 horse died and 2 were discharged prior to sample collection. Fecal samples from 9 of 34 horses yielded growth of Salmonella organisms on bacteriologic culture, and 23 yielded positive results via PCR assay on > or = 1 occasion. Among environmental samples from 21 stalls, salmonellae were detected at > or = 1 stall site on 6 of 78 occasions, and > or = 1 stall site yielded positive results via PCR assay on 69 of 77 occasions. Salmonella DNA was detected more frequently in samples of stall drains, cracks, and corners. Salmonella spp were cultured from samples of 3 stalls after both initial and second cleaning and disinfection cycles, but no organisms were detected in samples obtained after use of a peroxygen disinfectant. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that stalls in which horses with salmonellosis were housed should only be used to accommodate newly hospitalized horses after samples (collected after 2 cycles of cleaning and disinfection) from drains, cracks, and corners yield negative results on bacteriologic culture.     

Fecal shedding of Salmonella spp by horses in the United States during 1998 and 1999 and detection of Salmonella spp in grain and concentrate sources on equine operations

OBJECTIVE: To estimate prevalence of fecal shedding of Salmonella spp among horses in the US horse population and prevalence of Salmonella spp in grain or other concentrate used as horse feed on equine operations in the United States. DESIGN: Cross-sectional survey. SAMPLE POPULATION: Horses on 972 operations in 28 states. PROCEDURE: Fecal samples were collected from horses resident at each operation. Only a single sample was collected from any individual horse; number of horses from which samples were collected on each operation was determined on the basis of number of horses on the operation. A single sample of grain or concentrate was also collected from each operation. All samples were tested for Salmonella spp by means of bacterial culture. RESULTS: Overall, 0.8% (SE, 0.5) of resident horses shed Salmonella spp in their feces. The overall prevalence of operations positive for fecal shedding of Salmonella spp (i.e., operations with > or = 1 horse shedding Salmonella spp in its feces) was 1.8% (SE, 0.7). Prevalence of grain or other concentrate samples positive for Salmonella spp was 0.4%. Serotypes of Salmonella spp that were identified in grain or other concentrate were not those typically associated with clinical disease in horses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the national prevalence of fecal shedding of Salmonella spp by horses in the United States was 0.8%, and that prevalence of Salmonella spp in grain or other concentrate used for horse feed was 0.4%.     

Prevalence of Salmonella spp in cloacal, fecal, and gastrointestinal mucosal samples from wild North American turtles

OBJECTIVE: To determine prevalence of Salmonella spp in samples collected from wild North American turtles. ANIMALS: 94 wild North American turtles of 6 species in 2 genera. DESIGN: Prospective microbiologic study. PROCEDURES: A convenience sample of wild North Carolina turtles admitted to a veterinary college was evaluated for Salmonella spp by use of standard techniques via microbiologic culture of cloacal swab and fecal samples. Gastrointestinal mucosa samples were also collected at necropsy from turtles that died or were euthanized. Cloacal swab samples were also collected from wild pond turtles for bacteriologic culture. Controls were established by use of wild-type Salmonella Typhimurium LT2. RESULTS: 94 turtles were tested for Salmonella spp; Salmonella spp were not detected in any sample. By use of a pathogen-prevalence and sample-size table, the true prevalence of Salmonella spp was estimated as < 5%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that wild turtles in central North Carolina may not be active shedders or carriers of Salmonella spp. Despite this 0% prevalence of infection, proper hygiene practices should be followed when handling wild turtles.     

An allele-specific PCR assay for the rapid and serotype-specific detection of Salmonella pullorum

Salmonella serovar Pullorum is a causative agent of pullorum disease (PD) in poultry and is responsible for severe economic losses to the poultry industry in many parts of the world. A definitive detection of Pullorum requires culture followed by serotyping and biochemical identification, a process that is tedious and takes several weeks to accomplish. We have developed a rapid allele-specific polymerase chain reaction (PCR) method based on the nucleotide polymorphism in rfbS gene sequence for the serotype-specific detection of Pullorum and its differentiation from the closely related Gallinarum. The specificity of this PCR assay was tested using DNA samples from Pullorum (n = 13), Salmonella serotypes other than Pullorum (n = 19), and closely related non-Salmonella organisms (n = 5). The PCR assay was highly serotype-specific as the PCR amplicon of 147 base pairs was observed only in the case of Pullorum, while all the other DNA samples tested PCR negative. A definitive identification of Pullorum cultures was possible in less than 3 hr. As little as 100 pg of SP DNA was detected. This allele-specific PCR method is highly specific as well as sensitive and may be an effective molecular tool in the rapid and serotype-specific detection of Pullorum and differentiation from other Salmonella species.     

Evaluation of a PCR to detect Salmonella in fecal samples of horses admitted to a veterinary teaching hospital.

The diagnostic accuracy of a PCR used to identify horses shedding Salmonella spp. in their feces during hospitalization was estimated, relative to bacterial culture of serially collected fecal samples, using longitudinal data. Five or more fecal samples were collected from each of 116 horses admitted as inpatients, for reasons other than gastrointestinal disease, between July 26, 2001 and October 25, 2002. All 873 fecal samples collected were tested with a PCR based on oligonucleotide primers defining a highly conserved segment of the histidine transport operon gene of Salmonella typhimurium, and each sample was cultured for Salmonella spp. One or more samples from 87 (75%) horses were PCR positive, and Salmonella was cultured from 1 or more samples from 11 (9.5%) horses. All culture-positive horses had at least 1 PCR-positive result, whereas only 29 (28%) culture-negative horses were PCR negative on all fecal samples tested. The PCR was most specific, relative to bacterial culture of serially collected fecal samples, when used to test samples from Quarterhorse or breeds other than Thoroughbred or Standardbred, or from clinical (vs. healthy, accompanying horses) cases. Overall, the PCR had the greatest agreement (70%), compared with bacterial culture of serially collected fecal samples, using a cutoff of 2 or more positive PCR test results to define a Salmonella-positive horse. The reasons why some fecal samples, from which Salmonella organisms cannot be isolated, are PCR positive need to be determined before the PCR can be incorporated into Salmonella surveillance programs for hospitalized equine populations.     

Use of pooled samples for the detection of Salmonella in feces by polymerase chain reaction.

Many epidemiological studies of Salmonella rely on conventional bacteriological culture methods to detect Salmonella in fecal samples. These culture-based methods are inefficient for epidemiological studies in populations with a low prevalence of Salmonella. The objective of this study was to optimize a protocol that uses pooled Salmonella enrichment broth cultures of bovine feces and polymerase chain reaction (PCR) for the detection of the invA gene of Salmonella in feces. In one field trial, 196 animals were sampled, and all samples were tested by culture, invA PCR on individual samples, invA PCR on pools of 5 samples, and BAX PCR on individual samples. All assays showed a high agreement on individual samples (kappa > or = 0.75). The invA PCR was run on each of 40 pools and detected 19 of 22 culture-positive pools. In another field trial, 152 samples were taken from 4 dairies, and the invA PCR was performed on pools of 5 samples in addition to bacteriological culture of individual samples. Salmonella was detected in 5 of the 32 pools (7 total positive samples) by both PCR and culture. One pool was PCR-positive but culture-negative. Pooling did not dramatically affect the performance of the invA PCR; most of the culture-positive samples were detected, including all of the samples when there were 4 or more Salmonella colonies on the agar plate. Based on these field trials, invA PCR on pooled samples appears to be an efficient method of Salmonella detection as long as Salmonella loads are not extremely low.     

Failure to detect Salmonella species in a population of wild tuatara (Sphenodon punctatus)

AIM: To assess the prevalence of faecal excretion of Salmonella serovars by wild tuatara (Sphenodon punctatus) on Stephens Island, New Zealand. METHODS: One hundred cloacal swabs obtained as part of health-screening for the translocation of adult tuatara from Stephens Island were subjected to general aerobic culture and enrichment, and cultured specifically for Salmonella spp. RESULTS: No Salmonella spp were cultured from any of the cloacal samples, which suggests that, at the 95% confidence interval, the maximum prevalence of tuatara in the island population that were shedding Salmonella spp not detected by our sample size was 1.5%. Mixed bacteria were grown from the 70 cloacal swabs cultured aerobically. A predominant organism was evident in 30 cultures, and these were identified as Hafnia alvei type 1 (n=16) and type 2 (n=7), Corynebacterium spp (n=4), Klebsiella oxytoca (n=2), and Moraxella spp (n=1). CONCLUSIONS: The absence of intestinal carriage of Salmonella spp by the tuatara sampled in this study may indicate either lack of exposure, or an innate resistance to intestinal colonisation in tuatara. The significance of the other bacteria cultured as potential pathogens to the tuatara and as zoonotic risks is also uncertain. Wildlife managers should screen translocated reptiles for Salmonella spp, and thereby avoid exposing wild and managed populations to infection.     

Comparison of three DNA preparation methods for real-time polymerase chain reaction confirmation of Mycobacterium avium subsp. paratuberculosis growth in an automated broth culture system.

Three methods of harvesting DNA from broth culture tubes for quantitative real-time polymerase chain reaction (qrtPCR) confirmation of Mycobacterium avium subsp. paratuberculosis (MAP) were evaluated. A commercial DNA extraction kit, the boil method (boiling for 5 minutes), or direct addition of broth culture media to the PCR reaction mix were tested. Samples were evaluated at 8 or 11 days of incubation and at the time of instrument-signal culture-positive. In total, when tested at time to instrument signal positive, 10/10 (100%) of samples extracted by the commercial method were positive on qrtPCR, whereas 9/10 (90%) were positive after the boil method, and 6/10 (60%) were positive after the direct method. Increased volumes of egg-yolk emulsion added to the culture tubes prolonged the number of cycles to threshold positive for the samples that were not subjected to commercial extraction or boiling. Samples were not reliably positive when tested at 8 or 11 days of incubation. The boil method appears to represent a reasonable time- and money-saving method to harvest DNA for qrtPCR confirmation of MAP in broth culture at time to instrument signal positive.     

Improved diagnostic and real-time pcr in rapid screening for Salmonella in the poultry food chain

The goal of this study was to improve the diagnostic applicability of genus- and serovar- (S. Enteritidis and S. Typhimurium) specific PCR systems in screening faecal and caecal samples of poultry, poultry feed and poultrymeat for Salmonella, by keeping the opportunity to obtain Salmonella cultures from positive samples. Peptone broth pre-enrichment cultures of the samples were tested by PCR. In faecal and caecal samples from broiler chicks a strong inhibitory action was frequently observed. This could be reduced markedly by the addition of bovine serum albumin (BSA) acting as amplification facilitator. The results of testing pre-enrichment cultures from artificially contaminated faecal, poultry feed and poultrymeat samples (using S. Enteritidis, S. Typhimurium and S. Hadar as contaminants) suggest that the sensitivity of the above systems is 10(1)-10(2) CFU g(-1) sample. The testing of 95 caecal samples from slaughtered chicks resulted in 49% culture-positive and 76% PCR-positive samples. The suitability of a generic real-time PCR for testing faecal samples of poultry was also studied. Its detection limit for these samples was found to be lower than that of the diagnostic PCR system. Both methods reduced the time required for Salmonella detection to 24-30 h, and the advantage of the real-time PCR was its increased sensitivity. We have established a diagnostic and a real-time PCR system for rapid and reliable genus- and serovar- (S. Enteritidis and S. Typhimurium) specific detection of Salmonella for monitoring purposes in the poultry food chain. Sensitivity is equal to, or higher than, that of the standard bacterial culture method, and the method still provides the Salmonella culture if needed.     

DNA探针、粪检菌和ELISA三种方法在诊断副结核病中的比较研究

本研究在已构建的副结核分枝杆菌Ｃ２株ＤＮＡ基因文库的基础上，应用正、反向杂交试验从基因文库中筛选出特异性片段ＰＴＰ３１，以光敏生物素标记制成ＤＮＡ探针。用此ＤＮＡ探针以及粪检菌和ＥＬＩＳＡ三种方法分别对３２份副结核菌素（ＰＰＤ）变态反应阳性牛粪便及相应血清样品进行检测，其检出率分别为４７％（１５／３２）、５６％（１８／３２）和３４％（１１／３２）。对随机采集的２７６份牛粪便及血清样品，３种方法的检出率分别为１０％（２７／２７６）、１３％（３６／２７６）和７％（７９／２７６）。本研究结果表明，ＤＮＡ探针与粪检菌呈现正相关性，ＤＮＡ探针比ＥＬＩＳＡ方法能够检出更多的阳性数。     

Salmonella typhimurium DT104 in farmed rabbits

A total of 1,000 rectal samples were collected from rabbits coming from 25 rabbit farms in southern Italy. All samples were processed for isolation of Salmonella spp. by standard culture method based on the ISO 6579:2002 method. Salmonella spp. was isolated from 1/25 rabbit farms analyzed. In particular, four out of 1,000 rectal swab samples, taken from young rabbits, were serotyped as S. Typhimurium and phage typed as S. Typhimurium DT104. All the isolates were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (ACSSuT pentaresistance type). The findings of the present study suggest the rabbit as potential carrier of S. Typhimurium DT104.     

A survey for Mycobacterium avium subspecies paratuberculosis in the Royal Zoological Society of Antwerp

Paratuberculosis is a chronic intestinal disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (Map). Very little is known about the status of paratuberculosis in European zoos. In this study, the presence of Map in the animal collection of the Royal Zoological Society of Antwerp (RZSA) was investigated. Faecal and post mortem samples from 48 ruminants were used to set up cultures. DNA from faeces, tissue and positive cultures were tested by IS900 polymerase chain reaction (PCR). Additionally, 448 serum samples were tested with an ELISA kit. All culture samples were negative whereas PCR gave three positives on biopsy samples and one positive on faecal samples. With the ELISA, 21 sera could be classified as positive. There is evidence that Map is present in the RZSA but no high level faecal shedders could be detected. Further investigations are required in other European Zoos in order to complete the picture of Map infections.     

The prevalence and PCR detection of Salmonella contamination in raw poultry

Contaminated poultry meat has been identified as one of the principal foodborne sources of Salmonella. The development of rapid detection assays for Salmonella would enable official agencies and food industries to identify contaminated foodstuffs in a more timely manner. In addition, these diagnostic tools could allow more 'real time' decisions to be made regarding end product acceptability. In this study, a survey was carried out to determine the prevalence of Salmonella in raw broiler carcasses. A total of 198 neck skin samples were obtained from within 40 flocks at a commercial broiler slaughtering facility. The presence of Salmonella was assessed by traditional culture methods and by a Salmonella-specific polymerase chain reaction (PCR) test. Salmonella was recovered from 32 (16%) of all samples using traditional culture methods. In contrast, the PCR assay proved to be more sensitive and detected Salmonella DNA in 38 (19%) of the samples tested. The pathogen was detected in 45 (23%) of the 198 samples when culture and PCR results were combined. The sensitivity of the PCR test was also greater than culture when detecting Salmonella from within flocks (53% of flocks by PCR, 30% of flocks by culture). The combination of both tests revealed that 55% of the flocks were contaminated with Salmonella. The PCR assay proved to be a highly specific and sensitive method for detecting Salmonella and the incorporation of a routine PCR test in conjunction with standard culture could be effective in providing a more accurate profile of the prevalence of this pathogen in broiler carcasses.     

Prevalence of exposure to Salmonella spp in finishing swine marketed in Iowa

OBJECTIVE: To describe the prevalence of antibodies against Salmonella spp in swine marketed in Iowa. ANIMALS: Swine marketed by 1,044 low-volume producers and 45 high-volume producers. PROCEDURE: Samples of diaphragm muscle collected from swine carcasses were tested by an indirect ELISA based on lipopolysaccharides from Salmonella spp, in particular Salmonella serovar Typhimurium. Prevalence of positive results for antibodies against Salmonella spp for carcasses, lots, and swine for each producer was determined. Producer-level seroprevalence was used to classify swine from producers as having negligible, low, moderate, or widespread evidence of previous or historical exposure to Salmonella spp. RESULTS: From low-volume producers, 23,609 of 25,478 (92.7%; 95% confidence interval [CI], 92.4% to 92.9%) samples had negative results, and 1,863 (7.3%; 95% CI, 7.05% to 7.56%) had antibodies against Salmonella spp. Of the 6,299 lots of swine tested, 1,191 (18.9%) contained at least 1 sample with positive results. From high-volume producers, 203 of 2,486 (8.1%; 95% CI, 6.8% to 9.3%) samples had antibodies against Salmonella spp, and 124 of 629 lots had at least 1 sample with positive results for antibodies against Salmonella spp. CONCLUSIONS AND CLINICAL RELEVANCE: Less than 10% of pigs marketed in Iowa are apparently exposed to Salmonella spp. Most swine marketed by low-volume producers had negligible or little evidence of exposure to Salmonella spp, whereas a higher percentage of swine marketed by high-volume producers had positive results when tested to detect antibodies against Salmonella spp.