Maria de Fátima Borges

Toxigenic status of Staphylococcus aureus isolated from bovine raw milk and minas frescal cheese in Brazil.

A group of 291 Staphylococcus aureus isolates from mastitic cows milk (n = 125), bulk tank milk (n = 96), and Minas frescal cheese (n = 70) were screened for staphylococcal enterotoxin (SE) genes (sea, seb, sec, sed, see, seg, seh, sei, selj, and sell) and for the tst-1 gene encoding staphylococcal toxic shock syndrome toxin 1 by PCR assay. A total of 109 (37.5%) of the isolates were positive for at least one of these 11 genes, and 23 distinct genotypes of toxin genes were observed. Of the S. aureus isolates bearing SE genes, 17 (13.6%) were from mastitic cows milk, 41 (41.7%) were from bulk tank milk, and 51 (72.9%) were from Minas frescal cheese. The occurrence of exclusively more recently described SE genes (seg through sell) was considerably higher (87 of 109 PCR-positive strains) than that of classical SE genes (sea through see, 15 strains). The SE genes most commonly detected were seg and sei; they were found alone or in different combinations with other toxin genes, but in 60.8% of the cases they were codetected. No strain possessed see. The tst-1 gene was found in eight isolates but none from mastitic cows milk. Macrorestriction analysis of chromosomal DNA from 89 S. aureus isolates positive for SE gene(s) was conducted with the enzyme SmaI. Fifty-five distinct pulsed-field gel electrophoresis patterns were found, demonstrating a lack of predominance of any specific clone. A second enzyme, Apa I, used for some isolates was less discriminating than Sma I. The high genotype diversity of potential toxigenic S. aureus strains found in this study, especially from Minas frescal cheese, suggests various sources of contamination. Efforts from the entire production chain are required to improve consumer safety.

Occurrence of Listeria monocytogenes in salami

Eighty-one samples of four different types of salami (Friolan, Hamburguese, Italian and Milanese), belonging to five brands, and purchased at Rio de Janeiro market, were evaluated for the occurrence of Listeria monocytogenes. The pathogen was detected in 13.3% of Italian type samples of salami, while L. innocua occurred in 6.5% of the Italian type and in 16.6% of the Milanese type. The remaining samples were negative for Listeria spp.

Electrochemical immunosensors for Salmonella detection in food

Pathogen detection is a critical point for the identification and the prevention of problems related to food safety. Failures at detecting contaminations in food may cause outbreaks with drastic consequences to public health. In spite of the real need for obtaining analytical results in the shortest time possible, conventional methods may take several days to produce a diagnosis. Salmonella spp. is the major cause of foodborne diseases worldwide and its absence is a requirement of the health authorities. Biosensors are bioelectronic devices, comprising bioreceptor molecules and transducer elements, able to detect analytes (chemical and/or biological species) rapidly and quantitatively. Electrochemical immunosensors use antibody molecules as bioreceptors and an electrochemical transducer. These devices have been widely used for pathogen detection at low cost. There are four main techniques for electrochemical immunosensors: amperometric, impedimetric, conductometric, and potentiometric. Almost all types of immunosensors are applicable to Salmonella detection. This article reviews the developments and the applications of electrochemical immunosensors for Salmonella detection, particularly the advantages of each specific technique. Immunosensors serve as exciting alternatives to conventional methods, allowing “real-time” and multiple analyses that are essential characteristics for pathogen detection and much desired in health and safety control in the food industry.

Production of hydroxyapatite–bacterial cellulose nanocomposites from agroindustrial wastes

In the present work, bionanocomposites based on bacterial cellulose (BC) obtained from alternative sources (cashew juice and sisal liquid waste) and hydroxyapatite (HA) were developed. BC–HA composites were prepared through alternate immersion in CaCl2 and Na2HPO4 solutions. Cellulose was successfully produced from the alternative sources of media without the need for additional supplementation and HA crystals that homogeneously precipitated onto the BC surface. The Ca/P ratio ranged from 1.53 to 1.58, indicating the presence of calcium-deficient HA in the composites; this is a phase similar to biological apatite. After immersion into synthetic body fluid, the HA layer formed on the surface of pure BC and the composites, attesting the material’s bioactivity. Moreover, apatite deposition on the composites was up to three times higher than observed on pure cellulose with no significant desorption of apatite from the composites. These results support that the BC derived from agroindustrial wastes have potential to produce nanocomposites of cellulose/HA for use in bone tissue regeneration.

Safety, beneficial and technological properties of Enterococcus faecium isolated from Brazilian cheeses

This study aimed to characterize the safety and technological properties of Enterococcus faecium strains isolated from Brazilian Coalho cheeses. High levels of co-aggregation were observed between Enterococcus faecium strains EM485 and EM925 and both Escherichia coli and Clostridium perfringens . Both strains presented low levels of hydrophobicity. E. faecium EM485 and EM925 were both able to grow in the presence of 0.5% of the sodium salts of taurocholic acid (TC), taurodeoxycholic acid (TDC), glycocholic acid (GC), and glycodeoxycholic acid (GDC), although they showed the ability to deconjugate only GDC and TDC. Both strains showed good survival when exposed to conditions simulating the gastro intestinal tract (GIT). When tested for the presence of virulence genes, only tyrosine decarboxylase and vancomycin B generated positive PCR results.

Shelf life of minimally processed pineapples treated with ascorbic and citric acids

Abstract The purpose of this research was to determine the shelf life of minimally processed (MP) ‘Perola’ pineapples treated with ascor -bic acid (AA) and citric acid (CA) based on physical, chemical, sensorial and microbiological attributes. Slices were dipped into drinking water (control) or combined solutions of AA:CA (%) (1.0:0.5 and 1.0:1.0) with sodium hypochlorite (NaClO 20 mg L –1 ) for 30 seconds. The samples were conditioned in polyethylene terephtalate packages and stored at 4±1 °C per 13 days. The low peroxidase activity in the slices treated with antioxidant combinations was related to low pH values observed in these samples. The treatments 1.0:0.5 and 1.0:1.0 (AA:CA, %) favored maintenance of the initial a* values and avoided the pulp browning. The ascorbic acid increased more than double on the 2 nd day in the treated slices. By the 4 th day the CO 2 values suggested a higher respiratory activity in the slices treated with anti-browning compounds. The antioxidant treatments did not produce detectable residual flavors in the MP pineapple. Regardless of microbiological safety during the 13 days of cold storage, the control slices can be kept by 6 days, afterwards the color and dehydration become strong enough to affect the appearance. On the other hand, MP ‘Perola’ pineapples treated with 1.0:0.5 (AA:CA, %) and NaClO (20 mg L

Determinantes de virulência em Enterococcus endógenos de queijo artesanal

The presence of Enterococcus spp. in food poses a danger to public health due to its frequent association with various clinical infections. Pathogenicity in Enterococcus is multifactorial and complex, and stems from a sequence of virulence factors. The aim of this study was to evaluate the presence of phenotypic and genotypic determinants of virulence in Enterococcus spp. isolated from curd cheese. A total of 53 strains of Enterococcus spp. were analysed as to their susceptibility to antimicrobial agents, production of hemolysins, DNAse, thermonuclease, and gelatinase, and the profile of virulence-encoding genes. It was found that 75.5% of the strains were resistant to at least one of the nine antibiotics tested, 26.42% were resistant to two, and 3.77% to three antibiotics. The presence of vancomycin-resistance phenotypes was seen in 11.33% of the strains. Haemolytic activity was observed in 100% of strains and DNAse production in only 3.8%. There was no production of thermonuclease or gelatinase. Strains resistant to vancomycin and teicoplanin were identified as E. faecium and Enterococcus spp. The profile of the genetic determinants of virulence was highly variable, and 90% of the strains harboured at least one of the nine genes being studied. The efaA gene showed the highest prevalence (70%), followed by the ace gene (50%), the esp gene and gelE gene (40%).

Interferência da microbiota autóctone do queijo coalho sobre Staphylococcus coagulase positiva

High levels of microbial contamination, commonly found in animal origin foods and food processing environments, are able to hinder the growth in these products. In some contexts where lactic acid bacteria (LAB) are the normal dominant microbiota, such as in fermented food, Staphylococcus coagulase positive (SCP) colonises, persists and produces food poisoning. With the aim of verifying the interference of autochthonous microbiota encountered in Curd cheese over the presence of Staphylococcus aureus, 64 samples from 16 dairy were submitted to microbiological analysis to determine the levels of Microorganisms aerobes mesophilics (MAM), LAB and SCP. The results showed that the indigenous microbiota of the samples did not lead to inadequate growth, development and isolation of SCP, since this pathogen was detected even in samples with high levels of counts of AM and BAL.

Nanofibrillated bacterial cellulose and pectin edible films added with fruit purees.

Bacterial cellulose (BC) is a water resistant and strong material for edible films. Previous studies have been conducted on edible films containing fruit purees, but not using BC. In this study, films with or without fruit (mango or guava) purees were prepared using different ratios of nanofibrillated BC (NFBC) to pectin. The addition of fruit purees increased water vapor permeability (in about 13-18 times), reduced tensile strength (in more than 90%) and modulus (in about 99%), and increased elongation (in about 13 times), due to plasticizing effects of fruit sugars and matrix dilution by the purees. The partial or total replacement of pectin with NFBC resulted in improved physical properties, making the films stronger, stiffer, more resistant to water, and with enhanced barrier to water vapor. Fruit containing films based on pectin are suggested for sachets, whereas applications for food wrapping or coating may benefit from the use of NFBC.

Determinants of virulence inEnterococcusendogenous to artisanal cheese

The presence of Enterococcus spp. in food poses a danger to public health due to its frequent association with various clinical infections. Pathogenicity in Enterococcus is multifactorial and complex, and stems from a sequence of virulence factors. The aim of this study was to evaluate the presence of phenotypic and genotypic determinants of virulence in Enterococcus spp. isolated from curd cheese. A total of 53 strains of Enterococcus spp. were analysed as to their susceptibility to antimicrobial agents, production of hemolysins, DNAse, thermonuclease, and gelatinase, and the profile of virulence-encoding genes. It was found that 75.5% of the strains were resistant to at least one of the nine antibiotics tested, 26.42% were resistant to two, and 3.77% to three antibiotics. The presence of vancomycin-resistance phenotypes was seen in 11.33% of the strains. Haemolytic activity was observed in 100% of strains and DNAse production in only 3.8%. There was no production of thermonuclease or gelatinase. Strains resistant to vancomycin and teicoplanin were identified as E. faecium and Enterococcus spp. The profile of the genetic determinants of virulence was highly variable, and 90% of the strains harboured at least one of the nine genes being studied. The efaA gene showed the highest prevalence (70%), followed by the ace gene (50%), the esp gene and gelE gene (40%).