An insight into the antibiofilm properties of Costa Rican stingless bee honeys.

OBJECTIVE: There is an increasing search for antibiofilm agents that either have specific activity against biofilms or may act in synergy with antimicrobials. Our objective is to examine the the antibiofilm properties of stingless bee honeys. METHOD: Meliponini honeys from Costa Rica were examined along with Medihoney as a reference. All honeys were submitted to a screening composed of minimum inhibitory concentration, inhibition of biofilm formation and biofilm destruction microplate-based assays against a Staphylococcus aureus biofilm forming strain. Dialysis led to the isolation of an antibiofilm fraction in Tetragonisca angustula honeys. The honey antibiofilm fraction was evaluated for protease activity and for any synergistic effect with antibiotics on a Staphylococcus aureus biofilm. The active fraction was then separated through activity guided isolation techniques involving SDS-PAGEs, anion exchange and size exclusion fast protein liquid chromatographies. The fractions obtained and the isolated antibiofilm constituents were tested for amylase and DNase activity. RESULTS: A total of 57 Meliponini honeys from Costa Rica were studied in this research. The honeys studied belonged to the Tetragonisca angustula (n=36) and Melipona beecheii (n=21) species. Costa Rican Tetragonisca angustula honeys can inhibit the planktonic growth, biofilm formation, and are capable of destroying a Staphylococcus aureus biofilm. The antibiofilm effect was observed in the protein fraction of Tetragonisca angustula honeys. The biofilm destruction proteins allowed ampicillin and vancomycin to recover their antimicrobial activity over a Staphylococcus aureus biofilm. The antibiofilm proteins are of bee origin, and their activity was not due to serine, cysteine or metalloproteases. There were 2 proteins causing the antibiofilm action; these were named the Tetragonisca angustula biofilm destruction factors (TABDFs). TABDF-1 is a monomeric protein of approximately 50kDa that is responsible of the amylase activity of Tetragonisca angustula honeys. TABDF-2 is a protein monomer of approximately 75kDa. CONCLUSION: Tetragonisca angustula honeys from Costa Rica are a promising candidate for research and development of novel wound dressings focused on the treatment of acute and chronic Staphylococcus aureus biofilm wound infections.

Evaluación del efecto del cultivo probiótico Lactobacillus rhamnosus adicionado a yogurt natural y con probi6ticos comerciales sobre poblaciones de Staphylococcus aureus, Escherichia coli O157: H7, Listeria monocytogenes y Salmonella enteritidis / Evaluation of the effect of Lactobacillus rhamnosus probiotic culture added to yogurt over Staphylococcus aureus, Escherichia coli O157: H7, Listeria monocytogenes and Salmonella enteritidis populations

Se evaluó el efecto de diferentes tipos de cultivos probióticos en yogurt sobre poblaciones conocidas de Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes y Salmonella enteritidis. Los tres tipos diferentes de yogurt comercial utilizados fueron: sin probióticos adicionados, con probióticos CHR HANSEN® (Lactobacillus casei CRL_431 y L. acidophilus CRL_730) y otro con los mismos probióticos mencionados anteriormente, adicionado con cultivo de Lactobacillus rhamnosus (LR-35). Se inoculó aproximadamente 109 UFC/mL de cada bacteria potencialmente patógena en los diferentes tipos de yogurt, se mantuvo en refrigeración a 4ºC durante la vida útil de cada uno de estos alimentos (aproximadamente 30 días) y se realizó un recuento bacteriano cada cuatro días incluyendo el mismo día de la inoculación. Los resultados obtenidos demuestran que, existe diferencia en cuanto a inhibición entre los yogures sin probióticos y el yogurt comercial con probióticos, observándose un efecto inhibitorio evidente, por parte del segundo sobre las poblaciones de S. aureus, E. coli O157:H7 y L. monocytogenes. Con respecto a los yogures comerciales con probióticos más L. rhamnosus, no se observó alguna diferencia con respecto al efecto inhibitorio que poseen los yogures con probióticos L. casei y L. acidophilus . En los yogures en que se evaluó S. enteritidis se obtuvo la muerte de ésta al cabo de cuatro días. El presente estudio confirma el efecto antagónico que poseen los cultivos probióticos sobre bacterias potencialmente patógenas para el ser humano y animales que pueden estar contenidas en los alimentos.No obstante, el uso del probiótico Lactobacillus rhamnosus no ejerce un efecto inhibitorio adicional.

The effect of different types of probiotics present in yogurt over known populations of Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enteritidis was evaluated. The three types of yogurt used were: without added probiotics, with added probiotics (Lactobacillus casei CRL_431 and L. acidophilus CRL_730 CHR HANSEN®) and another one with the same probiotics mentioned above and Lactobacillus rhamnosus (LR-35) culture. About 109 CFU/ mL of each potentially pathogenic bacteria was added to each type of yogurt tested, and kept in refrigeration at 4ºC during its shelf life, about 30 days. Bacterial count was done the initial day and every four days. Results obtained show that there is a difference in the inhibition between yogurts without added probiotics and the commercial yogurt with added probiotics; there is a clear inhibitory effect of the last one over S. aureus, E coli O157:H7 and Listeria monocytogenes. The yogurt with added probiotics and L. rhamnosus did not show any additional inhibitory effect over the bacteria tested when compared with the yogurt with added probiotics. S. enteritidis could not be evaluated because it was not detectable in any yogurt samples evaluated four days after its inoculation. This study confirms the antagonic effect of probiotic cultures over potentially pathogenic bacteria for human beings and animals that may be present in food. Nevertheless, the use of L. rhamnosus did not produce any additional inhibitory effect.

Species distribution and susceptibility to azoles of vaginal yeasts isolated prostitutes.

OBJECTIVE: We investigated the use of miconazole among female prostitutes in Costa Rica as well as the distribution of vaginal yeasts and the susceptibility pattern to azoles of strains obtained from this population. Our intention was to relate a frequent use of miconazole to occurrence of vaginal yeasts resistant to azoles. METHODS: Vaginal samples were taken from 277 patients that have previously used azoles. Vaginal swabs were obtained for direct microscopy and culture. Yeast isolates were identified by germ tube test and assimilation pattern. Susceptibility testing was determined using a tablet diffusion method. RESULTS: The number of clinical Candida isolates (one from each patient) was 57 (20.6%). C. albicans was the predominant species (70%), followed by C. parapsilosis (12%), C. tropicalis (5.3%), C. glabrata and C. famata (3.5% each), C. krusei, C. inconspicua and C. guilliermondii (1.7% each). The majority of vaginal Candida isolates were susceptible to ketoconazole (91%), fluconazole (96.5%), and itraconazole (98%). A lower susceptibility of some isolates to miconazole (63%) was observed as compared to the other azoles tested. Moreover, the strains, nonsusceptible to miconazole, were more often obtained from patients that have used this antifungal at least four times within the last year before taking the samples as compared to those with three or less treatments (P<.01). CONCLUSION: An indiscriminate use of miconazole, such as that observed among female prostitutes in Costa Rica, results in a reduced susceptibility of vaginal yeasts to miconazole but not to other azoles.

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 per cent 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.

Efecto del horno de microondas sobre el crecimiento y sobrevivencia de Escherichia coli O157 H7 inoculada en tortas de carne de res / Effect of microwave oven over the growth and survival of Escherichia coli O157 H7 inoculated in bovine minced meat samples

The use of microwave ovens in food industry is a growing trend. It is used for thawing, drying and cooking food, but the microorganism's inactivation that this treatment may exert or not is still a subject of worldwide discussion. At the same time. Escherichia coli O157:H7 now presents itself as an emerging pathogen, distributed worldwide and associated with food. Its resistance to adverse environments has been widely discussed. The purpose of this work was to determine the effect of different times of exposure and cooking intensities of microwave oven on the survival of this bacterium inoculated into minced meat samples. These were inoculated with a high (10(7)-10(9) CFU/mL) or low (10(7)-10(7) CFU/mL) population of E. coli O157:H7, frozen for 3 days at-4 degrees C and thawed in a Whirlpool microwave oven according to their weight. They were radiated at levels of 70 per cent, 80 per cent, 90 per cent and 100 per cent for periods of 30, 60, 90 and 120 seconds. In each sample the rate of survival of the bacteria was determined according to the methodology described by Vanderzant & Splittstoesser. The results obtained showed that the rate of destruction of the bacteria analyzed was significant (p < 0.005). The number of bacteria present in the meat samples diminished dramatically as the exposure time and temperature increased, even though, for the complete elimination of this microorganism, a prolonged exposure was necessary, even though it did cause undesirable organoleptic characteristics in the food samples.

Evaluación de la actividad de cultivos probióticos sobre Listeria monocytogenes durante la producción y almacenamiento de yogur / Evaluation of the activity of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt

The effect of probiotic cultures over Listeria monocytogenes during the production and storage of yogurt was evaluated. A yogurt mixture (10.6 per cent non-fat solid liquids, 3 per cent fat and 0.3 per cent gelatin) was prepared, homogenized and pasteurized. Yogurt was inoculated with 0, 10(2), 10(4) and 10(6) CFU/mL of L. monocytogenes and 0.02 per cent of traditional lactic culture YC 180 (Streptococcus thermophilus and Lactobacillus bulgaricus) and probiotic culture ABY-1 (Bifidobacterium longum, B. bifidum, B, infantis, Lactobacillus acidophilus, Streptococcus thermophilus y Lactobacillus delbrueckii subsp. bulgaricus). It was incubated for 3 h at 43 degrees C until pH reached an approximate value of 4.8, followed by refrigeration at 5 degrees C for 21 days. During fermentation, samples were taken every hour, and during storage every 3 days, analyzing pH and lactic, bifidobacteria and pathogen count for each time. It was demonstrated that there was no significant simple effect for the type of culture used (ABY-1 and YC 180) (p = 0.684) over the amount of L. monocytogenes present in yogurt during the fermentation and storage periods. The presence of bifidobacteria in the ABY-1 culture did not present a significant effect over L. monocytogenes. Neither the effect of time presented a significant effect over L. monocytogenes (p = 0.448). In this case, the ABY-1 and YC 180 cultures present a bacteriostatic effect over the pathogen. The probiotic cultures had a bacteriostatic but not bactericidal effect over L. monocytogenes. This is not related to the protective effect of these cultures in bowel, since in-vivo conditions favor the production of antimicrobial substances, such as bacteriocins that act over pathogens.

Neurobehavioural and cognitive profile of traumatic brain injury patients at risk for depression and suicide.

The possibility that patients who have suffered a traumatic brain injury will commit suicide is high, and in many cases clinicians tend to underestimate this possibility. In this study, 39 consecutive patients are studied through a Rorschach technique more than 1.5 years after their hospital discharge. The data show that 48.6% of the patients fulfil the criteria that classifies them as depressive, and, of these, 65% are at clinical risk to commit suicide (33.3% of the total of TBI patients); 25.6% have not met the criteria of depression or suicidal tendencies, and another 25.6% show very low suicide tendency scores. Only 15.6% of the total patients presented only depression without risk of suicide. The neurobehavioural and cognitive profile of the TBI suicide-prone patient shows an emotional person with cognitive difficulties in how they interpret reality, the person tries to understand what is happening around them, but is unable to cope. They show concrete thoughts, although they have difficulties solving problems and have few intellectual resources to cope with their surroundings. They do not know how to distance themselves from the emotional aspects of situations.

Growth and survival of Escherichia coli O157: H7 in meat, poultry and vegetables mixed with different concentrations of mayonnaise.

In the last 20 years Escherichia coli O157: H7 has emerged as a new pathogen, causing worldwide disease, death and economic loss. Different studies have revealed important survival characteristics of this pathogen, although there are divergent criteria about its ability to survive in various mayonnaise formulations. We studied the effect of different mayonnaise concentrations (0%, 18%, 37% and 56%) (weight/weight) over the survival of the bacterium in common foods from a neotropical environment (Costa Rica). High [10(7)-10(8) Colony Forming Units (CFU)/ml] and low E. coli populations (10(4)-10(6) CFU/ml) were inoculated, (three replicates) in meat, chopped cabbage and poultry, and mixed with commercial mayonnaise to obtain the concentrations specified. They were incubated at 12 degrees C for 24, 48 and 72 hr. The E. coli O157: H7 enumeration was done according to a standard methodology. Populations of E. coli O157: H7 showed an increasing trend during the first incubation period (48 hr), in all the preparations, regardless of the fat concentration used. Our data indicate that E. coli O157: H7 is capable of surviving and growing in meat, cabbage and poultry mixed with mayonnaise, independently of its concentration.

Effect of storage temperatures on growth and survival of Escherichia coli O157: H7 inoculated in foods from a neotropical environment.

Escherichia coli O157: H7 has emerged as a new pathogen and is found worldwide. We studied the effect of several storage temperatures on the survival of this bacterium in common foods from a neotropical environment (Costa Rica) because at least seven clinical cases have been reported from the country, and no epidemiological link or probable food association has been described. High (10(6)-10(8) CFU/ml) and low (10(4)-10(6) CFU/ml) populations of E. coli were inoculated (three replications) in ground meat, chopped cabbage, chicken giblets and pasteurized milk and incubated at 0, 6 and 12 degrees C for 24, 48 and 72 h. Vegetables and milk were also stored at 22 degrees C for the same periods. The E. coli O157: H7 enumeration was done according to the methodology described in the Bacteriological Analytical Manual. Populations of E. coli O157: H7 showed either an increasing or decreasing trend, according to temperature, time or food base. Our data indicate that E. coli O157: H7 is capable of surviving and growing in meat, cabbage, milk and chicken giblets; food items commonly consumed by Costa Ricans.

[Nutritional and microbiological profile of soybean sausages available in Costa Rica]. / Perfil nutricional y microbiológico de los embutidos de soya disponibles en Costa Rica.

The nutritional and microbiological quality of 80 soybean sausage samples (50% frankfurter and 50% sausage mortadela) was studied. On average, the protein content was 17.5 g/100 g in sausage mortadela and 20 g/100 g in frankfurter. The mean total fat content was 5.5 g/100 g for both products. However when products of different manufacture industries were compared, a highly significant difference (p = 0.0000) in the fatty acids speciation between both groups and between samples of the same product were found. Bigger differences were found in the content of palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2). Cholesterol was not detected in samples analyzed. On average the atherogenicity index was 0.55 for sausage mortadela and 0.59 for frankfurter. A consumption of 25 grams of of soybean protein from these sausages can bring an intake of saturated fatty acids between 20-90% of the daily recommendation. Likewise, they can supply between 12-70% of the recommended daily polyunsaturated fatty acids. These variations are owing to the big difference in fatty acids speciation in each sausage brand. Around 20% of soybean sausages studied showed total coliform levels above 10(4)/g, being more frequent in sausage mortadela. Also 60% of this product and 10% of frankfurters showed psychrotroph levels of 10(6)/g. Clostridium perfringens, in levels above 10(2)/g was evidenciated in 5% of samples, Escherichia coli was not isolated from them. The findings of this study suggest the urgent need for implementing a quality control system for soybean sausages, before national health authorities consider to support nutritional campainings that promote their consumption.

[Datura stramonium poisoning]. / Intoxicación por Datura stramonium.

Datura stramonium is a hallucinogenic plant, widely distributed and easily accessible, which contains toxic anticholinergic alkaloids. Voluntary or accidental ingestion can produce serious illness or death. The clinical presentation is similar to that seen in cases of atropine poisoning. Signs and symptoms such as mydriasis, tachycardia, arrhythmias, agitation, seizures and coma can appear. Diagnosis is clinical and early treatment should be given, including gastrointestinal decontamination, supportive care and physostigmine in life-threatening cases. Prognosis is usually favorable.

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.

[Listeria monocytogenes incidence and evaluation of the sanitary quality of filleted fresh fish from the Metropolitan Area of San José]. / Incidencia de Listeria monocytogenes y evaluación de la calidad sanitaria del pescado fresco fileteado del Area Metropolitana de 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.

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.

[Presence of Clostridium perfringens in meat-based preparations in public food services in central San Jose, Costa Rica]. / Presencia de Clostridium perfringens en preparaciones a base de carne en servicios de alimentación pública del Cantón Central de San José, Costa Rica.

In Costa Rica there are a large number of public food services distributed along the country, where a considerable number of people eat daily. Clostridium perfringens is a bacteria associated with foodborne illness related, especially, to meat products kept for long time at temperatures under 70 degrees C. The aim of this study was to evaluate the public food services that use water baths for keeping food hot in order to establish the presence of C. perfringens in cooked bovine meat dishes and to evaluate the enterotoxigenic capacity of the strains isolated. 81 samples of cooked bovine meat plates coming from 27 public food services, located in the Central County of San José were analyzed. The methodology described by Labbe & Harmon for the isolation of C. perfringens was used in 10 g of sample. Also, the enterotoxigenic capacity of the strains was evaluated using the passive-reverse-latex-agglutination assay from Oxoid. From the 27 public food services analyzed, eight (30%) were positive in the three samplings done, nine (33%) were positive in one or two occasions, and ten (37%) were negative all times. This implies that in 17 (63%) of the establishments studied, the bacteria was isolated at least once. From the 81 preparations studied, 37 (46%) were positive for the bacteria. The temperatures at which food was kept varied from 56 to 82 degrees C, with an average of 68.7 degrees C. From the 37 strains identified as C. perfringens, 12 (32%) were positive for enterotoxin. In conclusion, the presence of C. perfringens in bovine meat dishes, maintained in water baths, represents an important risk for public health, and the temperature at which the preparation is kept is critical for the multiplication of the bacteria.

[Microwave effect on survival of sporulated bacteria inoculated in minced meat]. / Efecto de las microondas sobre la sobrevivencia de bacterias esporuladas inoculadas en carne molida.

Due to the current tendency of cooking and heating meat prepared foods in microwave ovens and the possibility that they transmit bacterial diseases, the survival rate of spore-forming bacteria was evaluated in minced meat samples. Meat was innoculated with a known number of Bacillus cereus and Clostridium perfringens spores, and laterly thawed and cooked in an Amana microwave oven (2450 Hz). Survival rate was determined according to the methodology described by Vanderzant & Splittstoesser, and the activity of the enzyme acid phosphatase was determined as cooking parameter. B. cereus spore showed a decrease in its number as the time of exposition increased, but without fully disappearing. C. perfringens spores also decreased in number, but showed a later increase, associated with the germination of survival spores.

[Presence of total coliforms, Escherichia coli and Listeria sp. in enteral formulas]. / Presencia de coliformes totales, Escherichia coli y Listeria sp. en fórmulas enterales.

The presence of total coliforms, Escherichia coli and Listeria sp. was evaluated in 65 samples of enteral nutrition formulas. In more than the 75% of the samples made up from cooked vegetables, fruits or meat broth, the score level of total coliforms was of 10(4) UFC/g. In 12-31% of the different enteral food formula, E. coli was isolated in levels ranging form 3.0 x 10(2) to 2.1 x 10(4) UFC/g. Enteral nutrition formulas made out of fruits and those elaborated with meal broth presented this agent more frequently and in bigger quantities. Listeria sp. was isolated in 17% of the fruit preparations and in enteral formulas made with milk. L. grayi, L welshimeri and L. innocua were the species found.

[Effect of microwaves over Staphylococcus aureus and Salmonella spp. inoculated into frozen minced meat]. / Efecto de microondas sobre Staphylococcus aureus y Salmonella spp. inoculados en carne molida congelada.

The efficacy of the microwave oven in the destruction of some pathogenic microorganisms inoculated into minced meat was studied. These were inoculated with Salmonella spp. or Staphylococcus aureus, freezed for 2-3 days at -4 degrees C and thawed, according to their weight, in an Amana microwave (24450 Hz). They were radiated at levels of 60%, 70%, 80% and 90% for periods of 15, 45, 60, 90 and 105 seconds. The rate of survival of each bacteria was determined according to the methodology described by Vanderzant and Splittstoesser, as well as the activity of the acid phosphate enzyme as cooking parameter. The microbiological analysis shows that, despite the cooking level used, the time required for the elimination of both bacteria is greater than the one in which the meat is considered enzymatically and organoleptically cooked.

[Presence of various pathogenic microorganisms in fresh vegetables in Costa Rica]. / Presencia de microorganismos patógenos en hortalizas de consumo crudo en Costa Rica.

This study reports the occurrence of some pathogenic microorganisms in vegetable consumed on a daily basis by Costa Ricans. Cryptosporidium sp. oocysts were found in 5.2% (4/80) of cilantro leaves, in 8.7% (7/80) of cilantro roots and 2.5% of lettuce samples. A 1.2% (1/80) incidence was found in other vegetables samples (carrot, cucumber, radish and tomatoe). Oocysts of this parasite were absent in cabbage. Giardia intestinalis was only detected in 5.2% (4/80) of cilantro leaves and in 2.5% (2/ 80) of cilantro roots. Entamoeba histolytica cysts were found in 6.2% (5/80) of cilantro leaves, in 2.5% (2/80) cilantro roots, in 3.8% (3/80) lettuce and in 2.5% (2/80) radish samples. At least a 2% incidence of this amoeba was found in other vegetable samples (carrot, cucumber, cabbage and tomatoe). Listeria monocytogenes was isolated in 20% (10/50) of the samples of cabbage salad. Hepatitis A virus and Rotavirus were evidenciated in three of the lettuce pooles, suggesting that at least three of the samples were contaminated with these viruses.