Browsing by Author "Campos, Ana"
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- High-pressure processing and lytic bacteriophage cocktail phageguard S as a synergistic hurdle system towards salmonella inactivation in egg whitePublication . Maciel, Cláudia; Campos, Ana; Komora, Norton; Pinto, Carlos A.; Brandão, Teresa R. S.; Saraiva, Jorge A.; Teixeira, PaulaSalmonella spp. still represents a major public health concern as the etiological agent of foodborne diarrhoeal illnesses. Salmonella Enteritidis is the most common serovar associated with non-typhoidal salmonellosis in the United States and Europe, through the ingestion of raw, undercooked eggs or egg-derived food products. The consumption pattern has changed worldwide, towards a growing demand for minimally processed foods. The association of emerging technologies with conventional antimicrobial agents has been scarcely exploited as a feasible multi-hurdle decontamination approach. The purpose of the present work was to develop a novel non-thermal technology through the combination of mild high pressure processing (HPP, 300 MPa) with the bacteriophage PhageGuard S towards a 4-strain Salmonella cocktail inactivation in egg white. A preliminary set of experiments allowed to establish the most adequate parameters to be employed in the proposed system. Concerning the HPP (200 to 600 MPa) resistance pattern of thirteen food and clinical Salmonella strains belonging to serovars Enteritidis, Typhimurium and Senftenberg, a prominent intrastrain heterogeneity was observed and as expected, higher pressure magnitudes elicited a lower survivability. Regarding the impact of the pressure processing on the egg white viscoelastic profile, it was found that from 400 MPa onwards the complex viscosity and elastic modulus increased noticeably. The second part of the work sought to investigate the decontamination potential of the proposed treatment. In the challenge assays performed in egg white comprising a high bacterial load (107 CFU mL-1), HPP per se was not able to accomplish a prominent bactericidal effect, whilst the combination with the bacteriophage elicited Salmonella inactivation to values below the detection limit. The association of the two hurdles was determined to be a synergism. Moreover, a scarce impact on the physical features of egg white – color, foaming capacity and rheological properties - was observed throughout the 7-day refrigerated storage (4ºC). To our knowledge, this is the first study documenting a sustainable non-thermal technology as a suitable alternative to egg white pasteurization since the synergistic system HPP-PhageGuard S accomplished a Salmonella 5- log reduction.
- Methods currently applied to study the prevalence of Clostridioides difficile in foodsPublication . Barbosa, Joana; Campos, Ana; Teixeira, PaulaClostridioides difficile is responsible for most cases of antibiotic- and hospital-associated diarrhoea. Several studies have demonstrated the presence of C. difficile in different foods such as meat, raw milk, vegetables and seafood, which supports the hypothesis that foods contaminated with spores may be contributing to the exposure to and transmission of C. difficile. Generally, the prevalence of C. difficile in foods is low and there is no standard methodology for its isolation. Available methods have been optimized for stool samples rather than foods. In the majority of the studies, a similar base culture medium has been used and different selective and enrichment compounds are further added, which is, sometimes, controversial. Despite the extensive use of cycloserine and cefoxitin, as well as moxalactam and norfloxacin, many authors believe that the use of these selective supplements had an adverse effect on the recovery of C. difficile and only enabled recovery of resistant isolates from food samples. Another example is the use of sodium taurocholate to potentiate the germination of C. difficile spores; there are studies reporting that the addition of this component in the enrichment medium did not exert a beneficial effect on C. difficile recovery. Variations in sample amounts, dilution factors, incubation times, among others, may also affect the recovery of C. difficile from foods. Numerous studies have recently emerged, since there is increasing interest in C. difficile as a potentially foodborne pathogen. Thus, the purpose of this review is to summarize the methodologies currently used on the isolation/detection of C. difficile in foods and its subsequent characterization and typing.
- Survival of clinical and food Acinetobacter spp. isolates exposed to different stress conditionsPublication . Campos, Ana; Lopes, Maria Sequeira; Carvalheira, Ana; Barbosa, Joana; Teixeira, PaulaAcinetobacter baumanni is recognized as one of the most important agents of nosocomial infections. Other species such as Acinetobacter lwoffii have also been associated with such infections. These species can be found in food products, such as vegetables, fruits and meats which can be a source of transmission of these organisms to community and hospital settings. Evidence that hospitals’ kitchens are a route of entry of pathogenic and antimicrobial-resistant bacteria was recently demonstrated. This study aimed to determine whether different Acinetobacter spp. isolated from human and food samples (lettuce, turkey meat, apple and pear) were resistant to stress conditions often applied in food processes, such as exposure to 60 °C, AMUKINA® and vinegar. Also the influence of food matrices on the behavior of isolates to these stress conditions was evaluated. Treatment with AMUKINA® and vinegar were effective against all clinical and food isolates. Exposure to 60 °C resulted in the reduction of the majority of isolates to values below the detection limit of the enumeration technique, however, it is important to note that most of the reductions only occurred after 30 min of exposure. One food isolate identified as A. baumanni was resistant to this thermal treatment and one clinical isolate only decreased 4 log cycles after 1 h. In general, food isolates were demonstrated to be more resistant than clinical isolates and no significant differences (p > 0.05) were found between A. baumanni and A. lwoffii species. With the exception of one food isolate that was more resistant to thermal stress in the presence of turkey meat, the food matrices investigated did not confer protection to the applied stresses. Due to the limited knowledge on this topic, we believe that this study is an important contribution to understanding the behavior of Acinetobacter spp. when exposed to treatments commonly applied to foods.