Control of the growth of Alicyclobacillus acidoterrestris in industrialized orange juice using rosemary essential oil and nisin.

The use of rosemary essential oil (RO) and its combination with nisin (RO+N) in preventing the multiplication of Alicyclobacillus acidoterrestris in orange juice was evaluated. The minimum inhibitory and bactericidal concentrations (MIC and MBC) for RO were both 125 µg ml-1 while RO+N displayed a synergistic effect. The use of RO and RO+N at concentrations of 1, 4 and 8× MIC in orange juice for 96 h was evaluated in terms of their sporicidal effectiveness. With regard to the action against A. acidoterrestris spores, RO at 8× MIC was sporostatic, whereas RO+N at 1× MIC was sporicidal. Morphological changes in the structure of the micro-organism after treatment were also observed by microscopy. Furthermore, flow cytometric analysis showed that most cells were damaged or killed after treatment. In general, the antioxidant activity after addition of RO+N decreased with time. The results demonstrate that using the combination of RO and nisin can prevent the A. acidoterrestris growth in orange juice.

Antibacterial activity of Barbatimão (Stryphnodendron adstringens) against Staphylococcus aureus: in vitro and in silico studies.

We evaluated the activity of the aqueous fraction and the ethyl acetate fraction of Stryphnodendron adstringens against Staphylococcus aureus and proposed their mechanism of action. The antibacterial activity of S. adstringens fractions was evaluated against S. aureus and the cell targets were rated by docking. The fractions showed moderate antibacterial activity against S. aureus without toxicity on two mammalian cell lines. They also showed synergistic antibacterial activity with tannic acid (TA). In silico assays indicated FabG, FabZ and FabI as probable targets. The metabolic pathway for fatty acid biosynthesis in S. aureus was affected by components of S. adstringens. The synergistic effect when combining TA with S. adstringens fractions suggests a natural alternative to S. aureus control. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study describing the possible targets of action of Stryphnodendron adstringens on Staphylococcus aureus. Molecular dynamics simulations showed that the components of S. adstringens affected the metabolic pathway for fatty acid biosynthesis (FAS II) in S. aureus, inhibiting the FabI, FabG and FabZ enzymes. As tannic acid (TA) is a known inhibitor of some targets identified, we showed synergistic antibacterial activity of S. adstringens in combination with TA. This combination did not show toxicity against HaCaT and Vero cells and based on all these results we suggest that S. adstringens can be a natural and sustainable alternative to S. aureus control.

Photodynamic inactivation of foodborne bacteria by eosin Y.

AIMS: The aim of this study was evaluate the effect of photodynamic inactivation mediated by eosin Y in Salmonella enterica serotype Typhimurium ATCC 14028, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778. METHODS AND RESULTS: Bacteria (107 CFU per ml) were incubated with eosin Y at concentrations ranging from 0·1 to 10 µmol l-1 , irradiated by green LED (λmax 490-570 nm) for 5, 10 and 15 min and the cellular viability was determined. Pseudomonas aeruginosa was completely inactivated when treated with 10 µmol l-1 eosin Y for 10 min. Treatments reduced B. cereus and Salm. Typhimurium counts to 2·7 log CFU per ml and 1·7 log CFU per ml, respectively. Escherichia coli counts were slightly reduced. Staphylococcus aureus presented the highest sensitivity, being completely inactivated by eosin Y at 5 µmol l-1 and 5 min of illumination. The reduction of cellular viability of photoinactivated Staph. aureus was also demonstrated by flow cytometry and morphological changes were observed by scanning electron microscopy. CONCLUSIONS: Eosin Y in combination with LED produced bacterial inactivation, being a potential candidate for photodynamic inactivation. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evidenced the efficacy of photodynamic inactivation as a novel and promising alternative to bacterial control.

Occurrence and antibiotic resistance of coliform bacteria and antimicrobial residues in pasteurized cow's milk from Brazil.

In this study we examined the hygienic and sanitary quality of pasteurized cow's milk in the state of Paraná, Brazil, by determining the presence of coliforms and occurrence of antimicrobial residues. A total of 260 milk samples were collected from commercial establishments in different regions of the state. Coliform populations were estimated by the multiple-tube test, and antimicrobial residues were detected by enzyme-linked immunosorbent assay. Overall, 105 samples (40.4%) were unsuitable for consumption according to Brazilian legal standards. Among the coliforms, Escherichia coli and Klebsiella pneumoniae were respectively identified in 77.05 and 36.07% of the samples. The highest rates of resistance to antimicrobial agents were observed for ampicillin (19.2%), cephalothin (18.9%), and tetracycline (17.1%). Antimicrobial residues were detected in 80 samples (30.8%). Forty-eight samples (18.5%) were positive for tetracycline, 29 (17.4%) for neomycin, 9 (3.5%) for beta-lactams, 6 (2.3%) for gentamicin, 4 (1.5%) for chloramphenicol, and 1 (0.4%) for streptomycin-dihydrostreptomycin. The results demonstrate a high prevalence of coliforms and also a high occurrence of antimicrobial residues in pasteurized cow's milk from Paraná, Brazil.