Bacteriological quality of traditional, organic and hydroponic cultured lettuce in Costa Rica

The main objective of this work was to evaluate the microbiological quality of lettuces commercialized in the Metropolitan Area of San José, Costa Rica, and cultured in different ways, in order to detect differences between the culturing methods and the risk that these products may represent for Public Health. The study was done at the Food Microbiology Laboratory, Universidad de Costa Rica, from March to July, 2010. 30 lettuce samples were analyzed (10 obtained by traditional culture, 10 by organic culture and 10 by hydropony). All samples were obtained from markets where their origin was certified. Total aerobic plate count, total and fecal coliforms count and Escherichia coli were determined to all samples, as well as the presence/abscense of Salmonella spp. and Listeria monocytogenes in 25 g. Results obtained show that there is no statistically significant difference (p < 0.001) between the different types of cultures analyzed for any of the parameters evaluated. An important percentage of the samples presented coliforms, nevertheless, just one E. coli strain was isolated from a traditionally cultured lettuce sample. Four different Salmonella spp. strains were isolated from the samples as well as one Listeria monocytogenes strain. Data obtained show that the consumption of this product, raw or without an adequate hygiene and disinfection may represent a risk for health. Also, from the bacteriological point of view, there is no significant difference between the culturing methods evaluated, suggesting that the specific directions for each type of culture are not followed or that there is an inadequate handling of the products or post harvest contamination.     

Evaluation of the bacteriological quality of ice cream sold at San Jose, Costa Rica

The presence of total and fecal coliforms, E. coli, Listeria sp and Salmonella sp. was evaluated in 65 samples of both commercial and homemade ice cream. 37.1% of homemade ice cream and 20% of commercial ice cream did not fulfill the international standard for total coliforms. At the same time 82.9% of home made samples and 56.7% of commercial ones presented fecal coliforms. E. coli was found in 51.4% of home made samples and 26.7% of commercial ones. Sixteen Listeria sp. isolates were obtained, 50% corresponded to Listeria monocytogenes and 50% to L. innocua. The overall presence of L. monocytogenes in ice cream samples was of 12.3% and it was isolated in all cases, from homemade ice cream samples. Salmonella was not isolated from the samples analyzed. Although the results obtained show an important improvement in the quality of ice cream, compared with a previous work done also in Costa Rica, further efforts shall be done, in order to offer safe products to consumers.     

Pesticide detection in Costarican vegetables based on the inhibition of serum and erythrocytic human cholinesterases

A simple and low cost method able to detect the presence of pesticides, organophosphates and carbamates based on the inhibition of serum and erythrocytic cholinesterases, was used in lettuce (Lactuca sativa), cilantro (Coriandum santivum) and celery (Apium graveolens) obtained from the Ferias del Agricultor from Valle Central of Costa Rica. The percentage inhibition of cholinesterases is related to the presence of plaguicide in the vegetable. Thirteen percent of the analyzed samples were positive for plaguicides using serum cholinesterase and 33% for erythrocytic cholinesterase. Washing and cooking the vegetables does not eliminate the presence of plaguicides but they lower slightly the concentration. Statistical evidence (p = 0.0001) indicates that erythrocytic cholinesterase has higher analytical sensitivity than serum cholinesterase. It is very important to establish the degree of contamination with pesticides in these agricultural products because they are exposed to direct contamination by fumigation, soil contamination and irrigation water, and are products that are often consumed without adequate cooking and washing.     

Sanitary and technologic evaluation of the rural processing of fresh goat cheese in Chile

A sanitary and technological diagnosis of the goat cheese rural process was carried out. The purpose was to obtain more information for the planning of a program aimed to the improvement of this small agroindustry. Samples of milk, curdle, dry abomasum, rennet, water and cheese of 10% of the small industries of two rural villages in two agricultural seasons, were taken. Moreover, dilutions of the utensils and goat udders were prepared. The samples were subjected to microbiological analysis of mesophilic aerobic bacteria count, most probable number of total and fecal coliforms, and detection of Staphylococcus aureus coagulase (+), Salmonella typhi and Brucella melitensis. Proximate chemical analysis and determinations of sodium chloride and titratible acidity in milk, cheese, dry abomasum and rennet, were carried out. Goat milk was also subjected to analysis of density. It was found that significant sanitary failures are present during th whole goat cheese process, although the highest bacteria contamination occurred at the milking, curdling and filling stages. These are characterized by excessive handling and absolute lack of hygiene. The pathogen B. melitensis was absent; therefore the causes of poisoning were attributed to the toxin produced by S. aureus and to the significant count of fecal coliforms found in the goat cheese. Even though the goats are fed under a poor feeding system, the milk presented a normal physical and chemical composition. Nevertheless, protein and fat matter losses occur during cheese preparation, as a result of handling practices and lack of process control.     

Evaluation of the presence of bacteria in food and environment of an Oncological Service of a National Hospital, San José, Costa Rica

The microbiological quality of 92 samples from the Oncological Service of a National Hospital, San José, Costa Rica was evaluated during the months of February to July, 2002. Of these samples, 48 were from salads, refreshments, and fruits and 44 from surfaces, air and hands of the medical personnel. The presence of total and fecal coliforms was determined by the total plate count technique, using Violet Red Bile Agar for the isolation of total and fecal coliforms, Baird-Parker Agar for Staphylococcus aureus, Cetrimide Agar for Pseudomonas and Listeria was enriched in University of Vermont Broth, Fraizer Broth and isolated in Oxford Agar. From the food samples analyzed, 77% were positive for at least one of the parameters studied; the fruits presented the greater contamination (94%) and the cooked salads the minor, even though Listeria was isolated in 13% of them. All tested salads (100%) were positive for fecal coliforms. Pseudomonas and S. aureus were isolated from fruits, raw salads, and refreshments. All the analyzed surfaces, with an exception, were negative for the parameters evaluated. 75% of the hands of the medical personnel were positive for at least one of the parameters evaluated; 25% had total coliforms (2.8x10(3) UFC/hand), 13% fecal coliforms (2.4x10(3) UFC/ hand), 69% S. aureus (1.3x10(3) UFC/hand) and 19% Pseudomonas sp. 115 isolates were randomly selected, and identified using miniaturized tests (API). When comparing these identifications with the 166 isolations done at the Clinical Laboratory of the Hospital from the infected patients of oncology, by means of variance analysis, it was determined that both bacterial populations were statistically similar.     

Bacteriological evaluation of fresh tilapia (Oreochromis niloticus) coming from the northern region of Costa Rica

The following work presents an evaluation of the normal and pathogenic flora associated to tilapia (Oreochromis niloticus), since there are no previous national studies referred to the microbiological quality of this product. The total aerobic plate count, lactic bacteria, Enterococcus sp and Aeromonas sp and fecal and total coliform count, and the presence of Listeria sp and Salmonella spp from the external surface of tilapias were evaluated. A total of 50 samples, coming from San Carlos and Ca?as zones were transported in ice to the Food and Water Microbiology Laboratory, Universidad de Costa Rica, where the laboratory analysis were performed, according to the methodology presented by de American Public Health Association, 1998. The results obtained confirm the microbiological freshness of the product when the analysis was performed, although coliform levels were unacceptable. Listeria sp was not found, but the isolation of Salmonella spp. confirms the fecal contamination of water where the tilapia is grown, aside of the Public Health concern. Also, it was found a high number of Aeromonas sp, as part of its normal flora, so we recommend including this genus in the quality standards for fresh fish. According to the data obtained, there was no significant difference (95% confidence) between the total plate count, fecal and total coliforms, Enterococcus sp. and Aeromonas sp. from the samples coming from the zones of San Carlos and Ca?as.     

Effect of liming and carbofuran on groundnut yield in sandy soils in Niger

One of the constraints to groundnut production in sandy soils of Niger is crop growth variability. In early 1989, a trial on the effect of lime and carbofuran on soil pH, Al toxicity, nematode population and groundnut yield was initiated to study crop growth variability. Groundnut was sown in the 1989 rainy season, followed by pearl millet (Pennisatum glaucum) in the 1989–90 dry season and again groundnut in the 1990–91 rainy, and dry seasons. In 1989 the carbofuran treatment increased the pod yield. Lime application did not change the pH and exchangeable Al⁺⁺⁺ contents in the soil and did not increase groundnut yield. In the 1990–91 rainy and dry season, however, the application of 10 t ha^–1 of lime increased pH, decreased exchangeable Al⁺⁺⁺, improved crop growth and increased the yield of groundnut to the same level as was achieved by the carbofuran treatment. Application of lime did not affect the nematode population, which were reduced by the carbofuran.International Crops Research Institute for the Semi-Arid Tropics (ICRISAT); Submitted as ICRISAT Journal Article No 1228(via Paris)     

Total and fecal coliforms,some enterobacteria staphylococcus sp. and moulds in salads for hot dogs sold in Maracay,Venezuela

Fast food sold on the streets are good vehicle to transmit gastrointestinal diseases to consumers because they are highly manipulated. The vegetables are a good media for pathogens growth. Raw vegetables salads for hot dog sold in Maracay were studied. Total and fecal Coliforms and Staphylococcus sp. were quantified by the Most Probable Number Technique, Coliforms and Staphylococcus isolated were partially identified. Also the mould population was quantified and identified. Microbial growth was correlated with pH and acidity measurements. MPN/g of Total Coliforms was 1.44 x 10(5) and 4.57 x 10(4) for fecal Coliforms. E. coli was no detected. 87 isolated from the Coliforms were partially identified as Citrobacter freundii variety 1 (45.09% of the isolated), C. freundii variety II (21.57%), Enterobacter aerogenes variety I (17.65%) and E. aerogenes variety II (15.69%); Staphylococcus sp. 3.93 x 10(6) MPN/g and all of its isolated (52) were coagulase negative. The mould population was 4.5 x 10(4) ufc/g, Penicillium sp., Aspergillus, sp., Fusarium sp. were partially identified. The salads presented a pH of 5.92 and an acidity of 0.78 ml of NaOH.     

Quality characterization of several bolognas in Mexico. I. Chemical and microbiologic evaluation

The State of Sonora, is one of the main producers of beer, cattle and pork in México. In the work herein reported, it was determined that the total processed meat consumption in Sonora was 403.69 ton/month. The main product was bologna which for this reason, was the basis of our study. Chemical and microbiological evaluations of the commercial brands of bologna, purchased in local markets, were performed, including analysis for determinations of protein, ash, nitrites, phosphates and benzoic acid content. Total mesophyllic counts, and most probable number of coliforms, Staphylococcus aureus (positive coagulase) and Salmonella sp. were also determined. The results of the chemical analysis revealed that none of the brands complied with established norms, particularly in regard to protein, carbohydrates, phosphates and benzoic acid levels which exceeded the norms. Aerobic mesophyllic counts, and most probable number of coliforms, had wide variations even within the same brand. Only one sample contained Staphylococcus aureus, and all samples were negative for Salmonella sp.     

Microbiological quality and effect of washing and disinfection of pre-cut Chilean vegetables

Actually it is possible to find a great offer of pre-cut vegetables in the Chilean market. These products present certain advantages, such as saving time in their preparation at home. The microbiological quality of some of these vegetables, pre-cut celery and pre-cut cabbage was assayed. Two different types of the products were studied. The traditional pre-cut vegetable and another one, which is also pre-cut but it is labeled as "ready-to-eat" (minimally processed). The last one could be consumed without previous washing or disinfecting. The assayed microbiological parameters were: total plate count, Enterobacteriaceae count, total coliforms and fecal coliforms most probable number, investigation of Escherichia coli and absence or presence of Salmonella. The effect of washing and washing and disinfecting on the natural microflora was also carried out. A disinfectant product for home use was obtained from the market. When comparing the obtained results for the two vegetables from both types, a high level of total plate count, Enterobacteriaceae count and total coliforms most probable number was observed. Fecal coliforms were detected only in samples of the traditional type in both vegetables. In each case E. coli was identified. No samples showed presence of Salmonella. Washing and washing and disinfecting effect was low. The maximum reduction of the present microflora of both vegetables was only up to 2 logarithm cycles.     

Microbiological contamination of enteral feeding solutions used in Costa Rican hospitals

Enteral feeding is the most common and preferred modality for providing nutritional support to hospital patients with a functional gastrointestinal tract that can not satisfy their nutritional requirements. Nevertheless, enteral feeding may be an important cause of bacterial infection. The aim of this study was to evaluate the microbial contamination level of enteral feedings distributed in Costa Rican hospitals. A total of 124 samples of enteral feeding, coming from five different hospitals from San José, Costa Rica, were evaluated during the second semester of 1997 and first of 1998 for the presence and identification of total and fecal coliforms, Pseudomonas sp. and Listeria sp. A subpopulation of the Pseudomonas isolated was analyzed for their antibiotic susceptibility patterns. The concentration of Gram negative rods in the samples of enteral feeding solutions ranged from 10(3) to 10(7) CFU/mL, markedly exceeding the permissible level (10(2) CFU/mL or less). The coliforms most frequently isolated included Enterobacter cloacae, Escherichia coil, Serratia sp. and Klebsiella pnuemoniae, Pseudomonas sp. was isolated in more than 70% of the samples made from commercial based solutions, fruits and vegetables. P. aeruginosa and P. fluorescens were the species most frequently isolated. Listeria sp. was not isolated from enteral solutions samples. The results obtained demonstrate that it is urgent to assure strict hygiene during the preparation and handling of all enteral feed in order to avoid bacterial growth. The implementation of HACCP (Hazard Analysis and Critical Control Points) system will be required in a near future for better quality control of enteral nutrition mixtures.     

Microbiological contamination of enteral feeding solutions used in Costa Rican hospitals

Enteral feeding is the most common and preferred modality for providing nutritional support to hospital patients with a functional gastrointestinal tract that can not satisfy their nutritional requirements. Nevertheless, enteral feeding may be an important cause of bacterial infection. The aim of this study was to evaluate the microbial contamination level of enteral feedings distributed in Costa Rican hospitals. A total of 124 samples of enteral feeding, coming from five different hospitals from San José, Costa Rica, were evaluated during the second semester of 1997 and first of 1998 for the presence and identification of total and fecal coliforms, Pseudomonas sp. and Listeria sp. A subpopulation of the Pseudomonas isolated was analyzed for their antibiotic susceptibility patterns. The concentration of Gram negative rods in the samples of enteral feeding solutions ranged from 10(3) to 10(7) CFU/mL, markedly exceeding the permissible level (10(2) CFU/mL or less). The coliforms most frequently isolated included Enterobacter cloacae, Escherichia coil, Serratia sp. and Klebsiella pneumoniae. Pseudomonas sp. was isolated in more than 70% of the samples made from commercial based solutions, fruits and vegetables. P. aeruginosa and P. fluorescens were the species most frequently isolated. Listeria sp. was not isolated from enteral solutions samples. The results obtained demonstrate that it is urgent to assure strict hygiene during the preparation and handling of all enteral feed in order to avoid bacterial growth. The implementation of HACCP (Hazard Analysis and Critical Control Points) system will be required in a near future for better quality control of enteral nutrition mixtures.     

Bacteriological evaluation of goat milk and cheese distributed in the Metropolitan Area of San José, Costa Rica

In the last years, there has been an increase in the production, industrialization and consumption of goat's milk and derivate products, including cheese, worldwide. Nevertheless, in Costa Rica there is no study of these products, reason why the objective of this work was to determine the microbiological characteristics of goat's milk and fresh cheese distributed in the Metropolitan Area of San José, Costa Rica, in order to evaluate its impact in the economical field and as a potential risk for Public Health. A total of 25 raw goat's milk samples, obtained by manual milking from 5 different producers tested in five different dates and 15 cheese samples, elaborated with pasteurized milk, commercially available and coming from three different producers were analyzed. The study included the analysis of spoilage bacteria (total aeobic count and lactic bacteria count), indicators of hygiene (total coliforms), fecal contamination (fecal coliforms), manipulation (Staphylococcus aureus) and pathogens (Listeria monocytogenes and Salmonella spp). High results were obtained for the total aerobic count and lactic bacteria count of the milk and cheese samples, showing a reduced shelf life. Total coliforms, in limits beyond the established ones by the Costa Rican legislation for human consumption raw milk, were found in 100% of milk samples, as well as for fecal coliforms in 76% of them. All cheese samples, except one, were negative for these indicators, suggesting good manufacturing practices. S. aureus counts were low and both Salmonella spp. and L. monocytogenes were not isolated from samples analyzed.     

Microbiological stability through storage period of Sphyraena ensis in Costa Rica

At the present study some of the microbiological and biochemical changes that occur through storage period in Sphyraena ensis, a fish specie of frequent consumption in Costa Rica were studied. Samples of S. ensis obtained during rainy and dry season were evaluated. Analysis included aerobic psychrotrophic count, identification and count of Vibrio, Enterococcus and Pseudomonas through a six day storage period at two different refrigeration temperatures, 2 and 7 degrees C. Same time, a commercial enzymatic immunoassay was used for the evaluation of the variation on the concentration of histamine produced in the different samples. Results obtained show that there is an increase on the bacteriological counts through the storage period, this increase is bigger as refrigeration temperature increases. Most of the samples maintained at 7 degrees C showed counts above 106 CFU/g after three days of storage, those stored at 2 degrees C did not present such high population levels. Nevertheless, after 6 days of storage, all samples, despite the storage temperature used, presented levels above the described one. Also, an histamine concentration increased through storage time, especially when the product was conserved at the higher temperature due to an increase in the number of histidine descarboxilating bacteria. There is no statistical difference between the counts obtained during rainy or dry season; nevertheless, there is a difference assicieated to the bacterial genera isolated.     

Use of coaxial photocatalytic reactor (CAPHORE) in the TiO2 photo-assisted treatment of mixed E. coli and Bacillus sp. and bacterial community present in wastewater

This paper reports the photocatalytic disinfection of water contaminated by a mixture of Escherichia coli and Bacillus sp. as well as that of wastewater containing a larger microbial community. The photocatalytic reactions were carried out in a coaxial photocatalytic reactor called CAPHORE, using TiO₂ P-25 of Degussa. E. coli is more sensitive than Bacillus sp. to photocatalytic treatment. Bacterial inactivation was dependent on organic matter and dissolved oxygen (DO) concentration.

Of the bacterial community present in partially treated wastewater, E. coli appears to be more sensitive to the treatment than Enterococcus sp., coliforms (other than E. coli), and Gram-negative (other than coliforms). After photocatalytic treatment, no bacterial recovery of previous groups was observed for 24 h in the dark. However a very low bacterial inactivation rate was observed for the whole bacterial population present in wastewater and detected by non-selective media. The effective disinfection time (EDT), the time necessary for total inactivation of bacteria without re-growth in a subsequent dark period referenced at 24 h (or 48 h), was reached only for Enterococcus sp., and coliform groups. EDT₂₄ was not reached for the whole population.     

Seasonal variations in the seed oil ofThevetia peruviana (Pers.) K. Schum

The fixed oil ofThevetia peruviana (Pers.) K. Schum. (T. neriifolia Juss) was obtained by solvent extraction, and its yield and composition were studied to reflect the effect of seasonal variations. Ripe and unripe seeds collected in December and February (the dry season) gave average yields of 72 and 52%, v/w, respectively, and those of May and August (the rainy season) gave 56 and 41%, v/w, respectively. Sitosterol was isolated and identified from the unsaponifiable fraction. Oleic, linoleic, stearic and palmitic acids were shown to be present in all the oils, while myristic, lauric, capric and caprylic acids were identified only in the oil from unripe seeds collected in the rainy season. The physical and chemical constants of the oils are given also.     

Structural Properties of Dried Potatoes,Mushrooms, and Strawberries as a Function of Freeze-Drying Pressure

The structural and thermophysical properties of freeze-dried agricultural products (potatoes, mushrooms, and strawberries) were investigated to determine whether these properties were affected by freeze drying conditions. The true density of freeze-dried products was measured with a helium stereopycnometer, and apparent density was obtained by measuring their geometric characteristics. Porosity and pore size distribution were also measured with a mercury porosimeter. The mechanical properties of freeze-dried agricultural products were obtained using a universal testing machine. Dried products were equilibrated in saturated salt solutions of constant water activity and scanned with a differential scanning calorimeter (DSC) for the evaluation of glass transition temperature. Simple mathematical models were developed in order to correlate the structural and mechanical properties with process conditions. The apparent density and mechanical properties of freeze-dried products increased with the applied freeze-drying pressure, whereas the porosity decreased. The glass transition temperature decreased with the increment of moisture content and it was not highly influenced by process conditions.     

挥发性脂肪酸和氨氮对污泥厌氧消化中病原指示微生物灭活的影响

通过外源添加不同浓度挥发性脂肪酸(VFA)和氨氮,模拟研究剩余污泥固态中温(35℃)厌氧消化条件下,VFA和氨氮浓度对病原指示微生物灭活效果的影响。试验结果表明:经过VFA组持续8 d和氨氮组持续28 d的厌氧消化后,消化液中的总大肠杆菌和粪大肠杆菌的杀灭率均达到99.9%以上;且初始VFA和氨氮浓度越高,消化系统中病原指示微生物的灭活效果越好。厌氧消化结束后,高浓度VFA组和氨氮组粪大肠杆菌均在检测限以下,表明剩余污泥固态厌氧消化中产生的高浓度VFA和氨氮能够提高剩余污泥消化残渣的生物安全性。     

Octacosanol Administration to Humans Decreases Neutral Sterol and Bile Acid Concentration in Feces

To investigate octacosanol (OC) metabolism in humans and its influence on cholesterol metabolism, two studies were conducted. In the first study ten healthy women received daily 30 mg OC for a period of 4 weeks. Blood and feces samples were collected at baseline and after the intervention. Serum concentrations of total cholesterol, LDL cholesterol, and HDL cholesterol were not altered following OC administration. Concentrations of excreted cholesterol end products decreased with the intervention (neutral sterols: 24.6 ± 9.7 mg/g vs. 20.3 ± 7.5 mg/g dry matter, P < 0.05; bile acids: 6.47 ± 3.89 mg/g vs. 4.03 ± 2.26 mg/g dry matter, P < 0.05). OC was not detected in serum samples, but the fecal OC concentration increased after the intervention period (11 ± 7 μg/g vs. 817 ± 179 μg/g dry matter, P < 0.05). In the second kinetic study on three participants, OC was identified in serums after oral application of 50 mg OC within 8 h. The decrease in the concentration of fecal cholesterol end products may underline a systemic effect of OC on cholesterol metabolism, even though the serum cholesterol levels were not influenced. Dual first authorship. S. Keller and F. Gimmler having contributed equally to the basic science presented.     

Listeria monocytogenes incidence and evaluation of the sanitary quality of filleted fresh fish from the Metropolitan Area of San José

Fish constitutes a very important part of human diet due to its protein content. The poor commercialization system existing in Costa Rica for this product causes an important secondary contamination that may include microorganisms such as fecal coliforms, Staphylococcus aureus and even pathogens such as Listeria monocytogenes. There is a lack of recent information about the microbiological quality of the fish that arrives to the Metropolitan Area of San José, Costa Rica, so the aim of this work was to study it through the detection of microbiological indicators and the incidence of L. monocytogenes. Five different samplings were realized to 27 fisheries located in two different areas from San José, Costa Rica: the Central Market and the rest of the Metropolitan Area. Each time, a 500 g sample of fresh filleted fish was taken and transported to the Food Microbiology Laboratory, Universidad de Costa Rica, for performing the different analysis, which included the presence/absence of L. monocytogenes, total plate count, total and fecal coliforms count and Most Probable Number of Staphylococcus aureus. Also, a hygiene evaluation of the different fisheries was performed. According to this, 22.2% of the fisheries were classified as excellent, 14.8% as good, 40.8% as regular and 22.2% as bad. Fisheries hygiene is independent of the incidence of L. monocytogenes with a 95% confidence level, and there is no significant relationship between hygiene and the other indicators analyzed. There is a significant relationship between the incidence of Listeria sp. and the hygiene of the Central Market area. It was determined that 96.3% and 29.6% of the fisheries accomplish with the microbiological limits established by ICMSF for S. aureus and total plate count, respectively. Listeria sp. was found in 65.2% of the fish samples analyzed. From these, 52.3% was L. monocytogenes, 43.2% L. innocua, 3.4% L. ivanovii and 1.1% L. seeligeri. In 88.9% of the fisheries the presence of L. monocytogenes was positive at least once.