Hektoen Enteric Agar Research Articles

Development of an improved selective medium for the detection of Shigella spp.

We developed an improved selective medium (HEX medium, modified Hektoen Enteric agar medium) for the detection of Shigella spp. from foods. Conventional culture media for Shigella spp. are neither specific nor sensitive. HEX medium contains lactose, sucrose, d-xylose, and salicin as a differentiation marker. The concentration of bile salts No.3 was reduced to a level of 0.3% which completely inhibited tested gram positive bacteria. All Shigella spp. tested (Shigella flexneri, Shigella dysenteriae, Shigella boydii, and Shigella sonnei) produced green colonies on HEX medium, while Hafnia alvei, found to be false positive for Shigella on HE agar, appeared as differentiable orange colonies on HEX medium. A total of 300 uninoculated and inoculated food samples were used to evaluate the specificity and sensitivity of HEX medium. The specificity was 13.50, 38.50, and 83.50 (%) on MacConkey agar, HE agar, and HEX medium, respectively. The sensitivity was 76.00, and 84.00 (%) for S. flexneri and 80.00, and 92.00 (%) for S. sonnei on HE agar and HEX medium, respectively. HEX medium had superior specificity and sensitivity compared to HE agar. Therefore HEX medium can be an appropriate selective and differential medium for detection of Shigella spp. from foods.

Prevalence of Salmonella spp. and serogroups found in venomous and nonvenomous snakes maintained in a zoological collection

This study set out to identify Salmonella species and serogroups found in the fecal matter from the snake collection, including venomous snakes, from a local zoo. Snakes are known asymptomatic carriers ofSalmonella spp. Previous studies have shown that Salmonella subspecies arizoniae can cause osteomyelitis in Ridgenose Rattlesnakes (Crotalus willardi). This study examining the carriage rate of serogroups in multiple snake species can help determine the possible spread of clinically significant Salmonella spp. within the collection and possible disease manifestations in both humans and snakes. All fecal samples were collected by professionally trained reptile keepers. Feces were placed in buffered peptone water using aseptic technique. The samples were then enriched using selenite broth and plated for isolation on hektoen enteric agar. Single colonies that tested positive motility, negative indole reaction, and negative for urease were sequenced using 16s ribosomal sequencing techniques. The samples were also serogrouped using a latex agglutination test. A total of thirty‐two samples were taken from twenty‐six species of snakes. Of the samples, 84.38% (27/32) had positive Salmonella colonies. The twenty‐seven positive Salmonella colonies were isolated and sequenced from 22 species of snakes. Serogrouping revealed clinically significant Salmonella serogroups C, A, B, and E or G. Clinically significant Salmonella spp. were found to be prevalent in the venomous and nonvenomous snakes. Polymerase Chain Reaction (PCR) is being conducted to examine the pathogenicity islands from the isolates.

Efficiency of Plating Media and Enrichment Broths for Isolating <i>Salmonella</i> Species from Human Stool Samples: A Comparison Study

A comparative study was performed to evaluate best practice culture media and enrichment broths for recovering Salmonella species from human stool samples. A total of 1297 human stools were collected and processed in this study. Evaluation of agar media was carried out by direct plating (DP), 1096 stool samples were inoculated on Modified Semisolid Rappaport-Vassiliadis (MSRV), Xylose-Lysine-Deoxycolate (XLD), MacConkey (MAC), and Hektoen Enteric (HE) agars. Evaluation of enrichment broths were carried out by enrichment all 1297 stool samples in Selenite broth (SB), Rappaport-Vassiliadis (RV) broth, and Buffered Peptone Water (BPW), followed by plating on MSRV, MAC, and HE agars. A total of 102 Salmonella-positive stools by DP, 85.3% (87/102) were recovered utilizing MSRV while recovery from XLD, MAC, and HE agars were 34.3% (35/102), 34.3% (35/102), and 29.4% (30/102) respectively. A total 299/1297 stools samples were Salmonella-positive on at least one plating medium after enrichment procedure were 77.3% (177/299) for SB, 86.0% (197/299) and 78.6% (180/299) for RV and BPW respectively. All Salmonella isolated in this study was nontyphi Salmonella. Presently, the data suggest that the use of MSRV over MAC, HE, and XLD agars for isolation nontyphi Salmonella species from human stools is more efficacious. Additionally, use of MSRV in combination with MAC and HE agars following enrichment in RV broth enhances recovery of nontyphi Salmonella species. However, RV broth is inhibitory to typhi Salmonella, thus use of MSRV medium in combination with MAC, HE or XLD agars in direct plating following enrichment in non-selective BPW is an alternate method for recovery of both typhi and nontyphi Salmonella species contaminated in human stool samples.

Prevalence of Salmonella spp. in Packed and Unpacked Red Meat and Chicken in South of Tehran.

Background:Despite of the advances in infectious diseases prevention and food technology, food-borne diseases are considered major problems in developed and developing countries. Meat plays a key role in transferring zoonotic diseases to human.Objectives:This study was conducted in south of Tehran, Iran, to investigate the prevalence rate of Salmonella spp. in packed and unpacked red meat and chicken.Materials and Methods:A total of 379 packed and unpacked samples including 189 red meat and 190 chicken samples were collected randomly. From each sample, 25 g was separated and treated with 225 mL of buffered peptone water, homogenized and incubated at 37°C for 24 hours. Samples were enriched using Rappaport-Vassiliadis broth and then streaked onto Hektoen enteric agar.Results:Totally, 86 out of 190 chicken and 38 out of 189 red meat samples were contaminated with Salmonella spp. The most isolated serotypes were Salmonella thompson (67.7%), S. heaardt (6.5%), S. enteritidis (4.8%), and S. veyle (4%), respectively. In general, the rate of chicken contamination was higher than meat, as 43.3% of packed and 46% of unpacked chicken samples were contaminated.Conclusions:These results confirmed the pervious findings, stating that proper packaging of meat products can effectively decreases the rate of microbial contaminations.

Rapid identification of Salmonella using Hektoen enteric agar and 16s ribosomal DNA probe-gold nanoparticle immunochromatography assay in clinical faecal specimens

A rapid identification of Salmonella, one of the most common foodborne pathogens worldwide, in clinical patients can enable better rational managements and prevent further outbreaks. The traditional immunochromatography using antibody-gold nanoparticles (Ab-AuNPs), such as the home pregnancy test, has been used for the Salmonella detection. In this study, we developed a new and rapid method using DNA probe-AuNPs for the detection of 16s ribosomal DNA of Salmonella. To evaluate the proposed method in clinical specimens, we performed a clinical test by identifying 159 stool samples on Hektoen agar containing black or crystalloid colonies using the method and the VITEK 2 system for confirmation. Eighty of the isolates were correctly identified as Salmonella to achieve 100% sensitivity. Seventy-five samples were correctly identified as non-Salmonella spp., but four were incorrectly identified as Salmonella. The specificity was 94·93%. The assay time is about 30 min after the DNA purification. The time-consuming and labour-intense biochemical tests can be replaced. We demonstrated that this assay is a rapid, convenient and cost-effective tool for Salmonella identification of clinical faecal samples, which is worth for further promotion and clinical use. This is the first application of using 16s ribosomal DNA probe-Au-NPs and immunochromatography on clinical samples. This is the first application of using 16s ribosomal DNA probe-gold nanoparticles and immunochromatography method on clinical samples with sensitivity 100% and specificity 94·93%. The assay time is about 30 min after the DNA purification. We find this assay a rapid, convenient, sensitive and inexpensive tool for Salmonella identification of clinical faecal samples, which is worth further promotion and clinical use and can replace the traditional time-consuming and labour-intense biochemical tests. The potential benefit of this approach is to develop a rapid point-of-care test that provides results while the patient is still at the doctors' office.

Rapid identification of Aeromonas species in stool samples with chromogenic media and matrix-assisted laser desorption ionization-time of flight mass spectrometry: an institutional experience

To evaluate the routine use of chromogenic media together with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) in gastrointestinal infections caused by Aeromonas spp. as rapid, practical, cost-effective and reliable methods. Materials and methods: Between August 2007 and March 2012, a total of 13,194 stool specimens of patients were included in the study. The stool samples and the reference strains were inoculated onto Cefsulodin-Irgasan-Novobiocin agar, sheep blood agar, eosin-methylene blue agar, and Hektoen enteric agar media together with CHROMagar Salmonella Plus. All the Salmonella and Aeromonas suspected colonies were identified with an automated system (Phoenix) and MALDI-TOF. Results: Some of the pink colonies resembling Salmonella were identified as Aeromonas spp. without any discordance (100%) between the systems. A total of 86 Aeromonas strains were identified: 30 A. caviae, 27 A. hydrophila, 16 A. veronii, 11 A. sobria, and 2 A. salmonicida. When analyzed macroscopically, those Aeromonas species had prominent colony appearance differences from classically detected Salmonella on CHROMagar Salmonella Plus media. Conclusion: A combination of CHROMagar Salmonella Plus and MALDI-TOF will help to detect Aeromonas species in 24 h in a cost-effective, practical, and reliable manner.

Antitoxic activity of serum and colostrum antibodies induced by prepartum immunization of mares with binding domains of Toxin A and B of Clostridium difficile

test would be performed on any black or green colonies found on either hektoen agar. Our lab has performed 810 Reveal tests on suspicious cultures from January 16, 2010 to December 31, 2011. There were 150 Reveal positive samples and 660 negative samples. There was 100% correlation (100% sensitivity and 100% specificity) of the Reveal test results to the BBL Crystal identification results. The Reveal test has been shown in our lab to save 24 hour to 48 hours in notifying the veterinarian of a positive Salmonella culture. Further studies are warranted with the Reveal test system on Selenite broths. If similar correlations are noted with the broths then Salmonella results may be able to be obtained in a 24 hour turnaround time.

Effects of Solid-Medium Type on Routine Identification of Bacterial Isolates by Use of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a rapid method for the identification of bacteria. Factors that may alter protein profiles, including growth conditions and presence of exogenous substances, could hinder identification. Bacterial isolates identified by conventional methods were grown on various media and identified using the MALDI Biotyper (Bruker Daltonics, Billerica, MA) using a direct smear method and an acid extraction method. Specimens included 23 Pseudomonas isolates grown on blood agar, Pseudocel (CET), and MacConkey agar (MAC); 20 Staphylococcus isolates grown on blood agar, colistin-nalidixic acid agar (CNA), and mannitol salt agar (MSA); and 25 enteric isolates grown on blood agar, xylose lysine deoxycholate agar (XLD), Hektoen enteric agar (HE), salmonella-shigella agar (SS), and MAC. For Pseudomonas spp., the identification rate to genus using the direct method was 83% from blood, 78% from MAC, and 94% from CET. For Staphylococcus isolates, the identification rate to genus using the direct method was 95% from blood, 75% from CNA, and 95% from MSA. For enteric isolates, the identification rate to genus using the direct method was 100% from blood, 100% from MAC, 100% from XLD, 92% from HE, and 87% from SS. Extraction enhanced identification rates. The direct method of MALDI-TOF analysis of bacteria from selective and differential media yields identifications of varied confidence. Notably, Staphylococci spp. from CNA exhibit low identification rates. Extraction enhances identification rates and is recommended for colonies from this medium.

Rapid detection of Salmonella sp. by means of a combination of selective enrichment broth and MALDI-TOF MS

The identification of Salmonella sp. in stool samples usually takes 2 days when employing routine procedures. Fast approaches are necessary in order to shorten the analysis time. The aim of this work was the development of a rapid procedure for the detection of Salmonella sp. from clinical stool samples. Spiked stool samples were cultured in selective selenite enrichment broth. Identifications were directly performed from the liquid broth by the MALDI Biotyper. After the evaluation of this method, the same procedure was applied to clinical samples. Coevally, the samples were streaked on Hektoen agar and single colonies were analyzed by the MALDI Biotyper. For comparison, the liquid broth was plated according to the standard laboratory procedure. A total of 4,847 samples were analyzed for Salmonella sp. In total, 108 Salmonella sp.-positive samples were identified; 66 of these were identified after the streaking of stool samples on Hektoen agar and subsequent MALDI Biotyper analysis of Salmonella sp. suspicious colonies. These and a further 34 samples were detected as Salmonella sp.-positive directly from the selenite enrichment broth on day one. Eight Salmonella sp.-positive samples were not detected before plating of the selenite broth and subsequent MALDI Biotyper analysis on day two. The combination of MALDI Biotyper analysis and selective selenite enrichment broth identification delivers positive results for the majority of the samples already after one day.

식품으로부터 쉬겔라 검출을 위한 분리배지 비교

본 연구는 식품으로부터 Shigella spp.를 검출하기 위해서 현재 사용되고 있는 분리배지를 대상으로 분리 성능을 비교하였다. MAC, SSA, DCA, XLD, HEA와 CHROMagar 총 6개의 분리배지를 대상으로 비교하였다. 일반 Shigella spp.에 대한 성장은 MAC에서 TSA와 비슷한 수준 균수를 보였고 DCA에서 낮은 균수로 측정되었다. 소고기, 돼지고기, 새우를 대상으로 한 회수실험은 S. sonnei가 CHROMagar에서 성장이 유의적으로 높았으며(p＜0.05) 양상추와 양배추에서는 S. sonnei가 SSA에서의 성장이 유의적으로 높게 나타났다(p＜0.05). 식품 상재균은 소고기, 새우, 양배추에서 전체적으로 낮은 수준으로 측정되었으나 각 배지에서 유의적 차이는 없었다(p＞0.05). 열 스트레스를 받은 S. sonnei는 MAC, SSA에서만 성장하였다. Enterobacteriaceae를 대상으로 한 선택성 측정 결과 HEA가 가장 높은 선택성을 나타내었다. Morganella spp.는 각 분리배지에서 Shigella spp.와 구분되지 못하였다. 실험에 사용된 배지는 각각의 조건에 따라 분리되는 특성이 상이하므로 식품에서 분리배지를 이용하여 Shigella spp.를 분리하고자 할 경우 분리 균의 상태에 따라 분리배지를 선택하여 사용하는 것이 바람직할 것으로 생각되었다.

Evaluation of Culture Media for Selective Enrichment and Isolation of Salmonella in Seafood

Seafood, including fish, shrimp, clam, crab, mussel, oyster, lobster, squid, octopus, and cuttlefish samples, was used to compare the recovery of Salmonella serovars by different selective enrichment and isolation media. The samples were selectively enriched in Rappaport-Vassiliadis (RV) broth and tetrathionate broth (TT), followed by selective isolation on Hektoen enteric (HE) agar, xylose lysine desoxycholate (XLD) agar, bismuth sulfite (BS) agar, and Brilliant Green (BG) agar media. Of 443 seafood samples analyzed, 108 were found to be contaminated with Salmonella. The role of selective enrichment in Salmonella spp. recovery with RV medium was distinctly high (70%) compared to TT broth (30%). The selective enrichment in RV broth followed by selective isolation on XLD, HE, BS, and BG agar recovered Salmonella at levels of 56, 41, 28, and 16%, respectively. Similarly, after enrichment in TT broth, XLD and HE agars recovered 27 and 23% respectively. The recovery of Salmonella with enrichment in TT followed by isolation on BS and BG was abysmally low at 4.6 and 5%, respectively. There was no significant difference (P > 0.05) in the recovery of Salmonella using the combinations of XLD and HE media with selective enrichment in RV broth. However, performance difference (P < 0.05) was observed in the recovery when BS and BG with RV, and XLD, HE, BS, and BG agars with TT broth were used. The present study showed that the combination of RV with XLD was the most efficient media for isolation of Salmonella from seafood when compared to other isolation media combinations.

Clinical and economic evaluation of BBL™ CHROMagar™ Salmonella (CHROMSal) versus subculture after selenite broth enrichment to CHROMSal and Hektoen enteric agars to detect enteric Salmonella in a large regional microbiology laboratory

Stool culture for enteric pathogens is one of the most labor-intensive clinical microbiology procedures. Direct plating of stool to BBL™ CHROMagar™ Salmonella (CHROMSal) (BD Diagnostics, Sparks, MD) versus subculture after selenite broth enrichment (Sel) to CHROMSal (Sel-CHROMSal) and Hektoen enteric agar (Sel-Hek) (PML Microbiologicals, Eugene, OR) to detect Salmonella were compared. The number of colony picks and biochemical/serotyping tests per plate was recorded. A cost comparison was done. Fifty-one of 2999 (1.7%) stools yielded Salmonella sp., and 80% of isolates grew on CHROMSal by 24 h. CHROMSal demonstrated much less false-positive growth compared to Sel-Hek ( P < 0.0001), which reduced biochemical and serotyping tests by 85% and 20%, respectively. Sel-CHROMSal and CHROMSal versus Sel-Hek improved enteric Salmonella detection when compared to a true positive “gold standard” (i.e., recovery by any culture method) with a sensitivity, specificity, positive predictive value, and negative predictive value of 100% and 94.12%, 100% and 99.97%, 100% and 97.96%, and 100% and 99.90%, respectively. CHROMSal use would result in substantial cost and labor savings.

CHROMagar Salmonella Detection Test Kit

BBL CHROMagar Salmonella was evaluated by an external food testing laboratory for the recovery of Salmonella in peanut butter using the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA-BAM) procedure. The peanut butter was found to be negative for the presence of Salmonella and, therefore, was seeded with heat-stressed Salmonella at target concentrations of 0.2 and 2 CFU/25 g. The Salmonella-seeded samples remained at room temperature for 14 days before analysis to stabilize the Salmonella in the food environment. Twenty 25 g test portions from each seeded level and five 25 g samples of uninoculated control samples were processed using enrichment broths as outlined in the FDA-BAM procedure. BBL CHROMagar Salmonella-prepared plates were evaluated with the FDA reference method media (bismuth sulfite, xylose lysine desoxycholate, and Hektoen enteric agars). Fractionally positive results were obtained from the lower inoculum level of peanut butter samples. Five positive cultures were recovered from both the BBL CHROMagar Salmonella and reference methods. The two methods gave identical results for all cultures resulting in a method agreement of 100%. McNemar's chi2 test, which assesses the evidence for difference in marginal proportions between two methods, could not be evaluated because it requires one or more discrepant cultures. However, because there were no discrepant cultures, the marginal proportions for the two methods were identical; therefore, there is no evidence of a difference between the methods. This study demonstrates that the results from BBL CHROMagar Salmonella are comparable to the three reference method media for the detection of Salmonella in peanut butter using the FDA-BAM procedures.

Patógenos isolados do trato gastrintestinal de cães saudáveis no Rio de Janeiro

A total of 30 stool samples from 13 healthy dogs were analyzed in order to detect microorganisms in their gastrointestinal tract. The samples were enriched in alkaline peptone water added with 1% and 3% sodium chloride and Rappaport-Vassiliadis enrichment broth (37oC/18-24h). Then, they were streaked onto Pseudomonas-Aeromonas selective agar base, tiossulfate citrate bile sucrose agar, eosin methylene blue agar, and Hektoen enteric agar. After the biochemical characterization, the results showed 41 bacterial isolated strains, from which Escherichia coli, Vibrio fluvialis, and Aeromonas caviae were the main pathogens encountered.

Identification of Salmonella using colony-print and detection with antibody-coated gold nanoparticles

In this study, we developed an easy screening test that identifies Salmonella in 2 h after colony-print which is a procedure based on the transfer of surface cells of the colonies to a nitrocellulose membrane. Gold nanoparticles coated with the anti- Salmonella antibody were used to highlight the Salmonella spp. on the membrane to facilitate the selectivity. On Hektoen agar, 134 stool samples containing black or crystalloid colonies were identified using the proposed method. Without any equipment, such as microscope, the red dots corresponding Salmonella were observed. After colony-print test, 22 of the isolates were correctly identified as Salmonella to achieve 100% sensitivity. 111 samples were correctly identified as non- Salmonella spp., but one was incorrectly identified as Salmonella. The specificity is 99.1%. This method is simple, straightforward, inexpensive, and fast. It can be easily applied to the routine workload of clinical laboratories, and can be very useful when large amounts of fecal samples should be evaluated for rapid screening and diagnosis.

Isolamento de coliformes, estafilococos e enterococos de leite cru provenientes de tanques de refrigeração por expansão comunitários: identificação, ação lipolítica e proteolítica

Isolation and identification of microorganisms in raw milk is interesting from the viewpoint of public health, since, depending on the species isolated, directed actions may be taken to improve milk quality. Milk deterioration is mainly the result of the growth of psychrotrophic microorganisms that produce heat-resistant lipases and proteases which are not denatured during pasteurization, conferring rancid and sour flavors, respectively. Thus, this work aimed at isolating and identifying the main genera of bacteria belonging to the Enterobacteriaceae family, oxidase-positive Gram-negative, Staphylococcus and Enterococcus genera, as well as determining lipase and protease activity in 16 rural farms in Boa Esperanca-MG, Brazil. The Gram-negative bacteria were isolated in Eosin Methylene Blue (EMB) and Hektoen Enteric agar media. Staphylococci were isolated in Baird-Parker agar and Enterococcus in KF agar. Colonies of interest were collected and submitted to Gram stain and to catalase and oxidase tests. Following these procedures, the isolates selected were identified using Bactray I, II and III; Api 20 Strep and tests suggested by Bergey's Manual of Determinative Bacteriology. Sorological identification of Enterococcus was carried out using Prolex. Milk from the 16 rural properties contained strains of fecal microorganisms, such as Escherichia coli and Enterococcus from the Lancefield D group. Oxidase-positive Gram-negative bacteria were identified in five farms. Staphylococcus was found in 10 farms. Milk collected from the farms investigated contained microorganisms that compromise its quality. All the microorganism groups tested showed lipase and protease activities.

Isolation of Salmonella Typhimurium from Outbreak-Associated Cake Mix

During May and June of 2005, 26 persons in several states were infected by a single strain (isolates indistinguishable by pulsed-field gel electrophoresis) of Salmonella enterica serotype Typhimurium after eating cake batter ice cream. The cake mix used to prepare the cake batter in the ice cream was implicated by epidemiologic investigation as the source of Salmonella contamination. Initial tests did not detect Salmonella in cake mix collected during the outbreak investigation. The objective of this study was to evaluate different procedures to isolate Salmonella from the implicated cake mix, cake, and ice cream. All outbreak-associated food samples (14 samples) were collected during the outbreak investigation by health departments of several of the states involved. Different combinations of Salmonella isolation procedures, including sample size, preenrichment broth, enrichment broth, enrichment temperature, and isolation medium, were used. Salmonella Typhimurium was isolated from two cake mix samples; the food isolates were indistinguishable from the outbreak pattern by pulsed-field gel electrophoresis subtyping. Universal preenrichment broth was substantially better than was lactose broth for preenrichment, and tetrathionate broth was better than was Rappaport-Vassiliadis broth for isolating Salmonella from the two positive cake mix samples. Although more typical Salmonella colonies were observed on plates from enrichment cultures grown at 35°C, more confirmed Salmonella isolates were obtained from plates of enrichment cultures grown at 42°C. Brilliant green agar, xylose lysine tergitol 4 agar, xylose lysine desoxycholate agar, Hektoen enteric agar, and bismuth sulfite agar plates were equally effective in isolating Salmonella from cake mix. The best combination of preenrichment-enrichment conditions for isolating the outbreak strain of Salmonella was preenrichment of cake mix samples in universal preenrichment broth at 35oC for 24 h, followed by enrichment in tetrathionate broth at 42°C for 24 h.

Calcium Carbonate Phosphate Binding Ion Exchange Filtration and Accelerated Denitrification Improve Public Health Standards and Combat Eutrophication in Aquatic Ecosystems

Cultural eutrophication, the process by which a lake becomes rich in dissolved nutrients as a result of point and nonpoint pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. The process occurs naturally in all lakes, but phosphate-rich nutrient runoff from sources such as storm drains and agricultural runoff is a major cause of excess phosphate-induced eutrophication. Especially in Madrona Marsh, one of the last remaining vernal marshes in the greater Los Angeles area, California, cultural eutrophication has become a major problem. In this study, calcium carbonate was found to be an excellent phosphate binder, reducing up to 70% of the phosphates in a given sample of water, and it posed relatively negligent ecological repercussions. This study involved the testing of this principle in both the laboratory and the real ecosystem. A calcium carbonate lacing procedure was first carried out to determine its efficacy in Madrona Marsh. Through this, ammonia was found to interfere with the solubility of calcium carbonate and therefore to be a hindrance to the reduction of phosphate. Therefore, various approaches for reduction of ammonia were tested, including aeration, use of fiber growth media, and plants, mainly Caulerpa verticellata, chosen for it hardiness, primarily in an attempt to increase population of Nitrobacter and Nitrosomonas. All were successful in moderately reducing ammonia levels. In addition, soil sampling, sediment analysis, microscopic plant analysis, microorganism and macroinvertebrate identification, and rate law formulations were conducted. The effect of phosphate and ammonia reduction on the populations of enterobacteria was also an important focus of this experiment. Varying concentrations of phosphate, ammonia, and calcium carbonate in conjunction with phosphate were tested in Madrona Marsh to determine their effects on the populations of enteropathogens on nonspecific blood agar, MacConkey agar, and Hektoen agar. Initial analyses suggest a strong correlation between phosphate concentrations and bacterial populations; a 66% decrease in phosphate resulted in a 35% reduction in bacterial populations and a 45% reduction in enteropathogenic populations. Likewise, a strong correlation was shown between calcium carbonate concentrations and bacterial reduction greater than that which can be attributed to the phosphate reduction alone. This was followed by the construction of various phosphate binding calcium carbonate filters, which used the ion exchange principle, including a spring loading filter, PVC pipe filter, and a galvanized filter. All were tested with the aid of Stoke's law formulation. The experiment was extremely successful in designing a working phosphate-binding and ammonia-reducing filter, and a large-scale agitator-clarifier filter system is currently being planned for construction in Madrona Marsh; this filter will reduce phosphate and ammonia levels substantially in the following years, bringing ecological, economical, and health-related improvements to the overall ecosystem and habitat.

Shigella Species

Shigella Species

Assessment of the presence of Salmonella spp. in Egyptian dairy products using various detection media.

To make a preliminary assessment of the incidence of Salmonella in Egyptian dairy products, and to investigate the effectiveness of various protocols for the detection of the pathogen in these products. Samples of milk and related dairy products were randomly collected from local markets and examined for the presence of Salmonella. While most samples were free of the organism, isolates of Salmonella enterica subsp. enterica serovar Typhimurium PT 8 could be recovered from 'matared' cream specimens. These isolates were susceptible to antibiotics usually used to challenge infections caused by Salmonella. A combination of buffered peptone water, Muller-Kauffman tetrathionate broth, and brilliant green phenol red agar gave the best results for the detection of the pathogen. Selenite-cystine broth and Hektoen enteric agar were ineffective as an enrichment and a plating medium, respectively, in the isolation of Salmonella. A modified identification strategy that reduces the burden of serological testing of presumptive isolates is proposed. 'Matared' cream could be a vehicle for transmitting Salmonella. Using the above combination of media, beside the suggested modified confirmatory procedure, should increase the effectiveness and ease of the detection of Salmonella in milk and dairy products.