Presence of enterotoxigenic Staphylococcus aureus in artisan fruit salads in the city of San Luis, Argentina

An increase in the consumption of fruit juices and minimally processed fruits salads has been observed in recent years all over the world. In this work, the microbiological quality of artisan fruit salads was analysed. Faecal coliforms, Salmonella spp, Shigella spp, Yersinia enterocolitica and Escherichia coli O157:H7 were not detected; nevertheless, eleven strains of Staphylococcus aureus were isolated. By multiplex PCR, all isolates showed positive results for S. aureus 16S rRNA gene and 63.6% of them were positive for sea gene. Furthermore, PCR sea positive strains were able to produce the corresponding enterotoxin. Finally, the inactivation of these strains in fruit salads by nisin, lysozyme and EDTA, was studied. EDTA produced a total S. aureus growth inhibition after 60 h of incubation at a concentration of 250 mg/L. The presence of S. aureus might indicate inadequate hygiene conditions during salad elaboration; however, the enterotoxigenicity of the strains isolated in this study, highlights the risk of consumers' intoxication. EDTA could be used to inhibit the growth of S. aureus in artisan fruit salads and extend the shelf life of these products.

Species identification, slime production and oxacillin susceptibility in coagulase-negative staphylococci isolated from nosocomial specimens

Ninety-two coagulase negative staphylococci (CNS) (forty-five of clinical origin and forty-seven of environmental origin), collected in a hospital in San Luis, Argentina, from March to June, 1999, were identified to species level by the ID 32 Staph and API Staph System (bioMérieux). Slime production was investigated by the quantitative and qualitative methods. Oxacillin susceptibility was determined by the disk diffusion test (1 æg), the agar dilution method (0.125 to 4 mg/ml) and agar screen (6 æg/ml). The presence of mecA gene was investigated by PCR. The clinical CNS species most commonly isolated were S. epidermidis, S. haemolyticus, S. hominis and S. saprophyticus. The frequency of slime production by clinical and environmental isolates was similar (25/45 and 27/47, respectively) and the results obtained by the quantitative and the qualitative methods correlated well. The mecA gene was detected in all S. epidermidis, S. haemolyticus and S. hominis isolates, which were resistant to oxacillin by the phenotypic methods. However, this gene was not present in S. klossii, S. equorum, S. xylosus and S. capitis strains. The gene was neither found in two out of the six S. saprophyticus isolates, in two out of three S. cohnii subsp. urealyticum isolates and in two out of five S. cohnii subsp. cohnii isolates, all of which resulted oxacillin resistant according to MIC. The gene was not found in oxacillin-susceptible strains either. Most of the CNS isolates (enviromental and clinical) that were slime producers were found to be oxacillin resistant, which makes the early detection of these microorganisms necessary to prevent their dissemination in hospitals, particularly among immunocompromised patients.

Primer aislamiento de cepas de Staphylococcus aureus productores de toxina del síndrome de shock tóxico-1 en manipuladores de alimentos en Argentina / 1st isolation of strains of Staphylococcus aureus producing toxic shock syndrome toxin 1 in foof handlers in Argentina

Se investigó la incidencia de portadores nasales de Staphylococcus aureus productor de toxina del síndrome de shock tóxico (TSST-1) en 39 operarios de una fábrica de productos lácteos y en muestras tomadas al azar de los alimentos manipulados, leche cruda y derivados lácteos fermentados (DLF), en una fábrica de la provincia de Buenos Aires (Argentina). El aislamiento de cepas se realizó en agar salino manitol y en agar de Baird-Parker. Luego de identificarlas se investigó la producción de TSST-1. En 8(20,5%) de los individuos se aisló S. aureus; 7(87,5%) de las cepas petenecieron al biotipo A (acovar humano) y 1(12,5%) al biotipo B (ecovar aviario y porcino). Tres cepas (37,5%) biotipo A, produjeron TSST-1. Teniendo en cuenta el número de operarios, el 7,6%) fueron portadores de cepas toxigénicas. Se aislaron 3 cepas de S. aureus de muestras de leche cruda, 1(33,3%) correspondió al biotipo B y 2(66,6%) al biotipo C (ecovar bovino y ovino). Trece cepas fueron aisladas de DLF, 5(38,0%) pertenecientes al biotipo A, 1(7,7%) al biotipo B y 7(53, 8%) al biotipo C. Ninguna de ellas resultó productora de TSST-1

Determinación de la calidad higiénica e invesigación de Salmonella spp y Yersinia enterocolitica en halados / Determination of the sanitary quality and research of Salmonella spp and Yersinia enterocolítica in ice-creams

Con el prepósito de ocnocer la calidad sanitaria de helados de fabricación industrial y semiindustrial y la presencia de especies patógenas o potencialmente patógenas de Salmonela y Yersinia enterocolítica, se examinaron 50 muestras procedentes de 5 establecimientos en la ciudad de San Luis. El recuento de coliformes fue positivo en el 100% de las muestras con valores < ou 20/g. El 14,0% de las muestras fueron positivas para Staphylococcus aureus en 1 g. en el recuento en placas 12,0% dieron menos de 10 u.f.c./g, 4,0% entre 101 y 1000 y 4,0% entre 10001 y 10000. Se aislaron 15 cepas, 26,6% ecovar A (humano) y las restantes C (bovino). todas fueron sensibles a cloranfenicolm cefalosporina y eritromicina; 46,6% a penicilina G y ampicilina; 93,3% a Kanamicina (6,6% intermedias = I); 73,3% a meticilina (26,6% I); 86,6% a tetraciclina (13,3% I). el 6,0% de las muestras superó el límite de aceptabilidad para S. aureus. No se hubo aislamiento de Salmonella spp. El 40% de las muestras se aisló Y. enterocolótica, una de ellas tipicada como B1; 0:3,50, 51; Lis Xz. El hallazgo de estas últimas en muestras con valores de coliforme inferiores al límite establecido en algunas legislaciones, sugiere una contaminación post procesamiento