Browsing by Author "Silva, J."
Now showing 1 - 10 of 50
Results Per Page
Sort Options
- Antibiotic resistance of Enterobacteriaceae isolated from the domestic food related environmentsPublication . Azevedo, I.; Albano, H.; Silva, J.; Teixeira, P.Background: Multidrug resistant Enterobacteriaceae which was confined to the hospital environments is now emerging in the domestic food related environments as well. The main objective of the present study was to investigate the prevalence of antibiotic re-sistant Enterobacteriaceae in the domestic food related environments. Methods: Resistance to ampicillin, chloramphenicol, ciprofloxacin, gentamicin, tetracy-cline, nalidixic acid, nitrofurantoin, and trimethoprim was evaluated in 125 isolates; col-lected in domestic food related environments using agar micro dilution method. Results: Results indicated that 49.6% of the isolates were resistant to at least one antibi-otic (32.8% to ampicillin, 6.4% to nitrofurantoin, 4% to tetracycline, 3.2% to nalidixic acid, 2.4% to chloramphenicol and 1.7% to trimethoprim). Resistance to multiple antibi-otics was observed in 6.4% of the isolates. Conclusion: This study implicates existence of antibiotic resistant Enterobactericeae in the domestic food related environments. This resistance phenomenon requires continual vigilance; and further studies are required to evaluate the role of domestic surfaces in the transmission of resistant pathogens and spread of infectious diseases.
- Antimicrobial susceptibility of Campylobacter jejuni isolated from poultry products and human cases of campylobacteriosisPublication . Camilo, R.; Mena, C.; Silva, J.; Teixeira, P.
- Application of nisin and chitosan as antimicrobial agents in traditional cured and smoked “Alheira”Publication . Fonseca, S. C.; Jácome, S.; Pinheiro, R.; Alves, M. R.; Noronha, L.; Silva, J.; Almeida, G.; Todorov, S. D.; Pintado, M. E.; Gomes, A; Morais, Alcina M. M. B.; Vaz-Velho, M.; Teixeira, Paula
- Assessment of characteristics of Pediococcus pentosaceus SB83 to be used in the prevention of neonatal listeriosisPublication . Borges, S.; Barbosa, J.; Silva, J.; Teixeira, P.The normal vaginal microbiota is dominated by lactobacilli, at 107 to 108 CFU/mL of vaginal fluid in healthy premenopausal women (Bolton et al. 2008). Lactobacilli contribute to the prevention of genital infections and play a role in the maintenance of a healthy state. The capacity that lactobacilli have to adhere and compete for adhesion sites in the vaginal epithelium and the capacity to produce antimicrobial compounds (hydrogen peroxide , lactic acid , bacteriocin-like substances and biosurfactants) are important in the impairment of colonization by pathogens. Furthermore, the production of lactic acid may help to maintain a low vaginal pH, approximately 4-4.5, that makes the vaginal environment more conducive to lactobacilli growth (Bolton et al. 2008). There is often a loss of colonization by lactobacilli caused by antibiotic therapy, douching, sexual activity, hormone deficiency, and contraceptive measures. The selection and use of “vaginal probiotics” can be important to restore a healthy vaginal microbiota (Pascual et al. 2008). Probiotic have been defined as “live microorganisms, which when administered in adequate amounts, confer a health benefit on the host”. Lactic acid bacteria (LAB) may play a major role in preventing illness of the host, including bacterial vaginosis, yeast vaginitis, urinary tract infection and sexually transmitted diseases. The administration of probiotics by mouth and intravaginally has been shown to be safe, and for pregnant women this restoration could be important to lower the risk of preterm labor (Reid and Bocking 2003). Listeria monocytogenes is a bacterium that, during pregnancy, can cause many serious complications including preterm labor, chorioamnionitis, spontaneous abortion, stillbirth and neonatal infection. Vaginal colonization by pathogens can result in transmission to the fetus/neonate by vertical transmission. Therefore, the vaginal application of LAB could be a preventive strategy to reduce the global burden of neonatal infections. The aim of this study was to select, identify and characterize an isolate of LAB to be considered as vaginal probiotic candidate.
- Bacteriocin production by spray-dried lactic acid bacteriaPublication . Silva, J.; Carvalho, A.S.; Teixeira, P.; Gibbs, P.A.Cell survival and antagonistic activity against Listeria innocua, Listeria monocytogenes and Staphylococcus aureus were investigated after spray-drying three bacteriocin-producing strains of lactic acid bacteria: Carnobacterium divergens, Lactobacillus salivarius and Lactobacillus sakei.
- Behavior of Listeria monocytogenes isolates through gastro-intestinal tract passage simulation, before and after two sub-lethal stressesPublication . Barbosa, J.; Borges, S.; Magalhães, R.; Ferreira, V.; Santos, I.; Silva, J.; Almeida, G.; Gibbs, P.; Teixeira, P.The effects of previous exposure to sub-lethal acidic and osmotic stresses on the survival of Listeria monocytogenes during exposure to gastro-intestinal (GI) tract simulation, was investigated. Six L. monocytogenes strains isolated from cheeses were selected and exposed to high salt concentrations or acidic conditions and their viability compared in quick and slow digestions. The results demonstrated that (i) all isolates were more sensitive to the exposure to acidic than to osmotic sub-lethal conditions (ii) significant differences (p < 0.05) between the two types of digestion were observed; in slow digestion, the log reduction was higher for all the tested isolates (iii) all isolates were inhibited in the presence of bile salts for both types of digestion (iv) differences between quick and slow digestion were not observed (p > 0.05) after exposure to either osmotic or acidic stress (v) a higher cellular inactivation (p < 0.001) was observed during the passage through the GI tract simulation after exposure to osmotic than to acidic stresses and (vi) neither osmotic nor acidic sub-lethal stresses conferred resistance to simulated GI tract conditions.
- Biopreservation strategies in combination with mild high pressure treatments in traditional Portuguese ready-to-eat meat sausagePublication . Castro, S. M.; Kolomeytseva, M.; Casquete, R.; Silva, J.; Queirós, R.; Saraiva, J. A.; Teixeira, P.Thrombomodulin (TM) is an endothelial cell membrane protein that acts as a major cofactor in the protein C anticoagulant pathway. The EGF-like domains 4-6 of TM (TM456) are essential for PC activation. In this study, we proposed a liposomal recombinant TM conjugate to mimic the membrane TM structure and its anticoagulant activity. First, a DSPE-PEG2000-TM456 was successfully synthesized by site-specific conjugation of azido-TM456 with DSPE-PEG2000-DBCO via copper-free click chemistry quantitatively. Then, liposome-TM456 was fabricated via direct liposome formation with the DSPE-PEG2000-TM456 and other lipids. This liposomal formulation of TM456 retained protein C activation activity as that of TM456. Also, liposome-TM456 was much more stable and had a longer plasma half-life than TM456 and DSPE-PEG2000-TM456, respectively. Moreover, liposome-TM456 showed in vivo anticoagulant effect by decreasing the mortality from 80% to 20% in a thrombin-induced thromboembolism mouse model. The reported liposome-TM456 conjugate mimics the endothelial TM anticoagulation activity and may serve as an effective anticoagulant agent candidate for future development.
- Case report of clinical salmonellosis by salmonella typhimurium that occurred in portuguese childrenPublication . Freixo, R.; Albano, H.; Silva, J.; Teixeira, P.Aims: Aim of this study is to characterize clinical isolates of Salmonella Typhimurium that occurred in Portuguese children on the basis of their virulence and antimicrobial resistance profiles and pulsed-field gel electrophoresis typing and to analyse possible strain relatedness. Methods and Results: Different Salmonella serotypes were isolated from clinical cases of salmonellosis that had occurred in two Portuguese hospitals (a total of 259 isolates). All Salm. Typhimurium strains, with the age of the patients known, (total of 26 isolates) were selected for this study. These isolates were characterized for their virulence gene profiles (agfA, iroB, slyA, hin/H2, spv), antimicrobial resistance profiles and investigated for the occurrence of multi-drug-resistant Salm. Typhimurium DT 104 by PCR. Salmonella isolates showed high rates of resistance to four or more antibiotics, 100% resistance to sulfadiazine and a high percentage of strains with the resistance profile of Salm. Typhimurium DT 104, two of them with this phage type (determined by PCR). A relationship between some clusters and their resistance and virulence profiles was detected, each cluster having the same profile. Conclusions: This study showed high-antibiotic resistance of the Salmonella strains investigated, and the presence of multidrug-resistant Salm. Typhimurium DT104 in infections of Portuguese children. Significance and Impact of the Study: Study is based on regarding the increase in antibiotic resistance by Salmonella strains isolated from infections in Portuguese children and on the presence of Salm. Typhimurium DT 104 circulating in Portugal.
- Characterisation of enterococci strains isolated from an artisanal Portuguese cheesePublication . Silva, J.; Carvalho, A. S.; Duarte, G.; Lopes, Z.; Domingues, P.; Teixeira, Paula; Gibbs, P. A.The main objective of this study was to characterise 8 enterococci strains, isolated from artisanal cheeses of good quality produced in the North of Portugal, including their potential pathogenicity, to determine technologically important characteristics and survival during drying, in order to evaluate the possibility of their use as adjunct starters in cheese production. Phenotypic and genotypic characteristics were used for strains identification. Based on acid production from sugar fermentation and β-galactosidase activity, two strains were identified as Enterococcus durans and 6 strains as E. faecalis. The enterococci strains were further analysed by RAPD-PCR, proteins profile and fatty acids profile. RAPD-PCR was demonstrated to be the most discriminatory typing method. Strain-to-strain variation was observed forthe ability to survive during storage in dried state.
- Characterization for enterotoxin production, virulence factors, and antibiotic susceptibility of Staphylococcus aureus isolates from various foods in PortugalPublication . Pereira, V.; Lopes, C.; Castro, A.; Silva, J.; Gibbs, P.; Teixeira, P.Staphylococcus aureus represents a public health challenge worldwide. The aim of this study was the characterization of different food isolates of S. aureus on the basis of their production of enterotoxins, hemolysins and resistance to antibiotics. A total of 148 coagulase-positive staphylococcal strains isolated from different food origins were identified to the species level. By multiplex PCR, 69% of the isolates were shown to be enterotoxigenic (SEs); the most common were sea seg, sea seg sei and seg sei. According to CLSI [CLSI, Clinical and Laboratory Standards Institute, 2007. Performance Standards for Antimicrobial Susceptibility Testing; Fifteenth Informational Supplement. CLSI document M100-S15. Clinical and Laboratory Standards Institute, Wayne, PA], 38% of the isolates were resistant to oxacillin ( 6 mg/mL; MRSA positives) but only 0.68% showed the presence of mecA gene. 70 and 73% of the S. aureus strains were resistant to b-lactams, ampicillin and penicillin, respectively. The virulence pattern was demonstrated to be origin and strain dependent. These findings emphasise the need to prevent the presence of S. aureus strains and SEs production in foods