Nazaré Pestana

Incidence of Salmonella from poultry products and their susceptibility to antimicrobial agents.

The incidence of Salmonella in 60 samples of poultry products of national origin available for consumers obtained from two local butcher shops and one canteen of the city of Porto and the susceptibility to antimicrobial agents allowed for human or animal therapy were evaluated. The results show that poultry samples are frequently contaminated with Salmonella (60%), belonging to 10 different serotypes. Salmonella enteritidis and S. hadar were the most prevalent serotypes. In addition, a high number (75%) of the Salmonella isolates was resistant to one or more antimicrobial agents and eight different resistance profiles were recorded. Resistance to nalidixic acid and enrofloxacin was demonstrated for 50% of the isolates and the occurrence of resistant and multiresistant S. enteritidis isolates were less frequent than for S. hadar. This study suggests a high incidence of Salmonella on Portuguese poultry products and shows that they could be a potential vehicle of resistant Salmonella foodborne infections.

Incidence and susceptibility to antimicrobial agents of Listeria spp. and Listeria monocytogenes isolated from poultry carcasses in Porto, Portugal

The occurrence of Listeria spp. and Listeria monocytogenes in 63 samples of Portuguese poultry carcasses obtained from two local butcher shops and one canteen in the city of Porto, Portugal, and the susceptibility of these bacteria to antimicrobial agents allowed for use in human or animal therapeutics were evaluated. All poultry samples were contaminated with Listeria spp., and L. monocytogenes was isolated from 41% (26 of 63) of the samples. Other Listeria species, including L. innocua, L. welshimeri, and L. seeligeri, were also isolated from poultry samples. A multiplex polymerase chain reaction method was used for the identification of all of the Listeria isolates; this method showed total conformity with the conventional method of biochemical identification and proved to be more reliable, faster, and less arduous. In addition, high percentages of Listeria spp. (84%) and L. monocytogenes (73%) isolates were found to be resistant to one or more antimicrobial agents of different groups, and 12 different resistance profiles were recorded. The frequency of the resistance of L. monocytogenes isolates to enrofloxacin and clindamycin is notable. The results of this study suggest a high incidence of L. monocytogenes on Portuguese poultry products available for consumers and indicate that poultry could be a potential vehicle of foodborne infections due to strains of L. monocytogenes that are resistant to antimicrobial agents.

Microbiological quality of ready-to-eat salads: an underestimated vehicle of bacteria and clinically relevant antibiotic resistance genes.

The increase demand for fresh vegetables is causing an expansion of the market for minimally processed vegetables along with new recognized food safety problems. To gain further insight on this topic we analyzed the microbiological quality of Portuguese ready-to-eat salads (RTS) and their role in the spread of bacteria carrying acquired antibiotic resistance genes, food products scarcely considered in surveillance studies. A total of 50 RTS (7 brands; split or mixed leaves, carrot, corn) were collected in 5 national supermarket chains in Porto region (2010). They were tested for aerobic mesophilic counts, coliforms and Escherichia coli counts as well as for the presence of Salmonella and Listeria monocytogenes. Samples were also plated in different selective media with/without antibiotics before and after enrichment. The E. coli, other coliforms and Enterococcus recovered were characterized for antibiotic resistance profiles and clonality with phenotypic and genetic approaches. A high number of RTS presented poor microbiological quality (86%--aerobic mesophilic counts, 74%--coliforms, 4%--E. coli), despite the absence of screened pathogens. In addition, a high diversity of bacteria (species and clones) and antibiotic resistance backgrounds (phenotypes and genotypes) were observed, mostly with enrichment and antibiotic selective media. E. coli was detected in 13 samples (n=78; all types and 4 brands; phylogenetic groups A, B1 and D; none STEC) with resistance to tetracycline [72%; tet(A) and/or tet(B)], streptomycin (58%; aadA and/or strA-strB), sulfamethoxazole (50%; sul1 and/or sul2), trimethoprim (50%; dfrA1 or dfrA12), ampicillin (49%; blaTEM), nalidixic acid (36%), ciprofloxacin (5%) or chloramphenicol (3%; catA). E. coli clones, including the widespread group D/ST69, were detected in different samples from the same brand or different brands pointing out to a potential cross-contamination. Other clinically relevant resistance genes were detected in 2 Raoultella terrigena carrying a bla(SHV-2) and 1 Citrobacter freundii isolate with a qnrB9 gene. Among Enterococcus (n=108; 35 samples; Enterococcus casseliflavus--40, Enterococcus faecalis--20, Enterococcus faecium--18, Enterococcus hirae--9, Enterococcus gallinarum--5, and Enterococcus spp.--16) resistance was detected for tetracyclines [6%; tet(M) and/or tet(L)], erythromycin [3%; erm(B)], nitrofurantoin (1%) or ciprofloxacin (1%). The present study places ready-to-eat salads within the spectrum of ecological niches that may be vehicles for antibiotic resistance bacteria/genes with clinical interest (e.g. E. coli-D-ST69; bla(SHV-2)) and these findings are worthy of attention as their spread to humans by ingestion cannot be dismissed.

Quince jam quality: microbiological, physicochemical and sensory evaluation

Abstract The present work aimed to study the quality of 18 brands of quince jam commercially available in the Portuguese market. Microbiological analyses included enumeration of yeasts and molds. Sugar content was determined by refractometry (°Brix), while the quantification of the preservatives benzoic and sorbic acids as well as other organic acids (citric, malic, lactic, quinic, succinic) was carried out by HPLC/UV. For sensory analysis, a panel of 10 assessors with slight training was used following the quantitative descriptive analysis methodology. Microbiological analyses revealed that four quince jam samples presented a total number of yeasts and molds higher than 103 cfu/g, which is above the expected levels for this parameter. With respect to sugar content, four samples presented °Brix lower than 63%, while most of the samples (eleven) contained between 63% and 70% of sucrose. Only three samples presented °Brix higher than 70%. A large variability among the commercial brands of quince jam was noticed for benzoic, sorbic, citric, malic, quinic and succinic acids contents. Benzoic acid content exceeded the legal limits of 500 mg/kg in five samples. The sum of benzoic and sorbic acids was above the limits allowed by legislation (1000 mg/kg) in two samples. Categorical principal components analysis using number of molds, number of yeasts, benzoic, sorbic, succinic, malic, citric, quinic acids as variables was performed to determine similarities/differences between quince jam samples. Results from sensory analysis revealed mainly a group of samples with typical soft odour and taste, attributes correlated with low granulous texture and shiny surfaces, in contrast to another group of samples with intense odour, but less typical, more acid and puree, sandy type of texture. Other samples were situated between this two extremes. Apart from the few points raised above, mainly in what concerns preservative levels, in general terms one can say that the products investigated are in good agreement with the major national specifications, though some action should be undertaken to assure that better practices will help lowering the number of easily avoidable non-conformities.

Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extract

Abstract Context: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer. Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation. Materials and methods: Physical, microbiological and functional stability were evaluated during 6 months storage at 20 °C and 40 °C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed. Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20 °C for 6 months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610 ± 70 µgh−0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4 h after product’s application. Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.

Shelf Life Assessment of Modified Atmosphere Packaged Turbot (Psetta maxima) Fillets: Evaluation of Microbial, Physical and Chemical Quality Parameters

Quality and safety of turbot fillets under modified atmosphere packaging (MAP) were assessed by microbial (total viable counts), physical (drip loss, pH, colour CIE Lab) and chemical parameters (total volatile basic nitrogen (TVBN), trimethylamine nitrogen (TMAN), biogenic amine contents). Three different atmospheres (MAP 1, 10/40/50 % O2/CO2/N2; MAP 2, 10/60/30 % O2/CO2/N2; MAP 3, 10/80/10 % O2/CO2/N2) were tested. Packaged turbot fillets were stored at 2 ± 1 °C and monitored over 30 days, at intervals of 5 days. Fillets from the control group, packaged with air (AIR), were the first to present signs of degradation reaching rejection threshold values for all evaluated parameters. In MAP fillets, total bacterial count was lower than 106 cfu/g for a longer period. After 10 days of storage, MAP and AIR fillets showed significant differences (p < 0.05) on the values of TVBN, TMAN and biogenic amines. MAP fillets presented a higher drip loss, and fillets in AIR became more yellowish (upper b* values) while those in MAP looked whitish for an increased period (upper L* values). All microbial, chemical and physical traits revealed the protective effect of the different MAP studied, especially those with a higher percentage of CO2. MAP application added, at least, 5 days to shelf life of turbot fillets.

The in vivo extracellular life of facultative intracellular bacterial parasites: Role in pathogenesis

Classically labeled facultative intracellular pathogens are characterized by the ability to have an intracellular phase in the host, which is required for pathogenicity, while capable of extracellular growth in vitro. The ability of these bacteria to replicate in cell-free conditions is usually assessed by culture in artificial bacteriological media. However, the extracellular growth ability of these pathogens may also be expressed by a phase of extracellular infection in the natural setting of the host with pathologic consequences, an ability that adds to the pathogenic potential of the infectious agent. This infective capability to grow in the extracellular sites of the host represents an additional virulence attribute of those pathogens which may lead to severe outcomes. Here we discuss examples of infectious diseases where the in vivo infective extracellular life is well documented, including infections by Francisella tularensis, Yersinia pestis, Burkholderia pseudomallei, Burkholderia cenocepacia, Salmonella enterica serovar Typhimurium and Edwardsiella tarda. The occurrence of a phase of systemic dissemination with extracellular multiplication during progressive infections by facultative intracellular bacterial pathogens has been underappreciated, with most studies exclusively centered on the intracellular phase of the infections. The investigation of the occurrence of a dual lifestyle in the host among bacterial pathogens in general should be extended and likely will reveal more cases of infectious diseases with a dual infective intracellular/extracellular pattern.