Abstract Background Natural products represent important sources of antimicrobial compounds. Propolis and compounds from essential oils comprise good examples of such substances because of their inhibitory effects on bacterial spores, including bee pathogens. Methods Ethanol extracts of propolis (EEP) from Apis mellifera were prepared using different methods: double ultrasonication, double maceration and maceration associated with ultrasonication. Together with the antimicrobial peptides nisin and melittin, and compounds present in the essential oils of clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum), assays were carried out on one Bacillus subtilis isolate and Paenibacillus alvei (ATCC 6344) against vegetative and sporulated forms, using the resazurin microtiter assay. Synergism with all the antimicrobials in association with tetracycline was verified by the time-kill curve method. Potassium and phosphate efflux, release of proteins and nucleic acids were investigated. Results EEPs showed the same MIC, 156.25 µg/mL against B. subtilis and 78.12 µg/mL against P. alvei. The peptides showed better activities against B. subtilis (MIC of 12 µg/mL for melittin and 37.50 µg/mL for nisin). Antimicrobials showed similar inhibitory effects, but cinnamaldehyde (39.06 µg/mL) showed the best action against P. alvei. Melittin and nisin showed the greatest capacity to reduce spores, regarding B. subtilis there was a 100% reduction at 6.25 and 0.78 µg/mL, respectively. Concerning P. alvei, the reduction was 93 and 98% at concentrations of 80 µg/mL of melittin and 15 µg/mL of nisin. EEPs showed the highest effects on the protein release against B. subtilis and P. alvei. Nucleic acid release, phosphate and potassium efflux assays indicated bacterial cell membrane damage. Synergism between antimicrobials and tetracycline was demonstrated against both bacteria. Conclusion All antimicrobials tested showed antibacterial activities against vegetative and sporulated forms of P. alvei and B. subtilis, especially nisin and melittin. Synergism with tetracycline and damage on bacterial cell membrane also occurred.

O objetivo deste estudo foi investigar a atividade antibacteriana da própolis produzida ao longo do ano por diferentes métodos de coleta (coletor de própolis 'inteligente' - CPI, tela plástica - TP e raspagem convencional - RC) sobre Staphylococcos aureus e Escherichia coli. Foram utilizadas 15 colmeias de Apis mellifera africanizadas. Para o preparo do extrato, foi misturada a própolis produzida mensalmente pela mesma técnica de coleta. O EAP foi preparado na proporção de 30% (30 g de própolis completando o volume para 100 mL com etanol 70%). Para avaliação da atividade biológica do EAP, foram usados dois micro-organismos: uma bactéria gram positivia Staphylococcus aureus e uma gram negativa Escherichia coli, por meio da metodologia de difusão em ágar. Os resultados mostraram que a própolis apresenta atividade antibacteriana, sendo esta influenciada pela sazonalidade e método de colheita utilizado.

The antibacterial activity of propolis produced throughout the year by different methods of collection ('intelligent' collector of propolis - ICP; plastic screen - PC; conventional scraping - CS) on Staphylococcos aureus and Escherichia coli is investigated. Fifteen beehives (five per collector) of Africanized Apis mellifera were used. Monthly produced propolis, with the same collection technique, was mixed for the preparation of the extract. The ethanol extract of propolis (EEP) was prepared at the ratio of 30% (30 g of propolis, completing the volume for 100 mL with ethanol 70%). Two microorganisms, a positive bacterium Gram Staphylococcus aureus and a negative bacterium Gram Escherichia coli, through the methodology of diffusion in agar, were used for the biological activity evaluation of EEP. Results show that propolis presented antibacterial activity, affected by seasonality and by collecting method.

We evaluated the frequency of enterococci from food and found 95.2% of positivity, being E. faecium and E. faecalis the most frequent species. High-level streptomycin resistance was observed, as well as gelatinase and hemolysis activity, showing the potential role of environmental strains as reservoir of virulence and resistance traits.

Os sanitizantes químicos tradicionais utilizados na indústria de alimentos apresentam, como desvantagem, o possível desenvolvimento de resistência e adaptação bacteriana, interferindo na eficiência bactericida mínima destes produtos. Os óleos essenciais com atividade antimicrobiana despertam grande interesse na indústria de alimentos, pela possível utilização como princípios ativos de sanitizantes. Esta pesquisa objetivou determinar a concentração inibitória mínima (CIM) dos óleos essenciais (OEs) de cravo-da-índia e canela contra bactérias Gram positivas (Staphylococcus aureus e Listeriamono cytogenes) e Gram negativas (Escherichia coli e Salmonella sp.) e compará-la com a CIM do hipoclorito de sódio, além de determinar a concentração bactericida mínima (CBM) dos OEs para L. monocytogenes. Foi utilizado o método da microdiluição e os OEs foram caracterizados, quimicamente, por cromatografia gasosa - espectrometria de massa. Os componentes principais dos OEs de canela e cravo-da-índia foram o cinamaldeído (67,58%) e o eugenol (77,58%), respectivamente. A CIM do OE de canela foi de 0,04%, para as bactérias Gram positivas, e < 0,02%, para a bactérias Gram negativas. O OE de cravo-da-índia teve CIM de 0,04% para Salmonella sp., 0,06% para E. coli e S. aureus e 0,08% para L. monocytogenes. Para todas as bactérias testadas, a CIM do hipoclorito de sódio foi > 0,2%. A CBM para L. monocytogenes, no OE de cravo-da-índia, foi de 0,18% e o OE de canela destacou-se por apresentar CBM < 0,02%, demonstrando a possibilidade do uso destes OEs, principalmente o de canela, como princípios ativos de sanitizantes.

The traditional chemical sanitizers used in the food industry have the disadvantage of a possible development of bacterial resistance and adaptation, interfering with their minimum bactericidal efficiency. Essential oils with antimicrobial activity arouse great interest in the food industry for their possible use as active ingredients of sanitizers. This study aimed to determine the minimum inhibitory concentration (MIC) of cinnamon and clove essential oils (EOs) against Gram-positive (Staphylococcus aureus and Listeriamono cytogenes) and Gram-negative (Escherichia coli and Salmonella sp.) bacteria, as well as compare it with the MIC of sodium hypochlorite, and to determine the minimum bactericidal concentration (MBC) of EOs for L. monocytogenes. The microdilution method was used and the EOs were chemically characterized by gas chromatography - mass spectrometry. The main components of the cinnamon and clove EOs were respectively cinnamaldehyde (67.58%) and eugenol (77.58%). The cinnamon EO MIC was 0.04% for Gram-positive bacteria and < 0.02% for Gram-negative bacteria. The clove EO showed MIC of 0.04% for Salmonella sp., 0.06% for E. coli and S. aureus and 0.08% for L. monocytogenes. For all bacteria tested the sodium hypochlorite MIC was > 0.2%. The MBC for L. monocytogenes of the clove EO was 0.18%, while the cinnamon EO distinguished itself for presenting MBC < 0.02%, demonstrating the possibility of using these EOs, especially the cinnamon one, as active principles of sanitizers.

The use of essential oils in foods has attracted great interest, due to their antagonistic action against pathogenic microorganisms. However, this action is undesirable for probiotic foods, as products containing Lactobacillus rhamnosus. The aim of the present study was to measure the sensitivity profile of L. rhamnosus and a yogurt starter culture in fermented milk, upon addition of increasing concentrations of cinnamon, clove and mint essential oils. Essential oils were prepared by steam distillation, and chemically characterised by gas chromatography-mass spectrometry (GC-MS) and determination of density. Survival curves were obtained from counts of L. rhamnosus and the starter culture (alone and in combination), upon addition of 0.04% essential oils. In parallel, titratable acidity was monitored over 28 experimental days. Minimum inhibitory concentration values, obtained using the microdilution method in Brain Heart Infusion medium, were 0.025, 0.2 and 0.4% for cinnamon, clove and mint essential oils, respectively. Cinnamon essential oil had the highest antimicrobial activity, especially against the starter culture, interfering with lactic acid production. Although viable cell counts of L. rhamnosus were lower following treatment with all 3 essential oils, relative to controls, these results were not statistically significant; in addition, cell counts remained greater than the minimum count of 10(8)CFU/mL required for a product to be considered a probiotic. Thus, although use of cinnamon essential oil in yogurt makes starter culture fermentation unfeasible, it does not prevent the application of L. rhamnosus to probiotic fermented milk. Furthermore, clove and mint essential oil caused sublethal stress to L. rhamnosus.

As propriedades biológicas da própolis de Apis mellifera são amplamente relatadas sendo comuns variações nas mesmas em função da região onde foram produzidas. A ação antimicrobiana de própolis obtidas em três regiões do Brasil (Botucatu-SP, Mossoró-RN e Urubici-SC) foi investigada sobre linhagens isoladas de infecções clínicas humanas (Staphylococcus aureus, Escherichia coli, Enterococcus sp, Pseudomonas aeruginosa e Candida albicans). Foram preparados extratos alcoólicos de própolis (EAP) e determinada a Concentração Inibitória Mínima (CIM) seguida do cálculo da CIM90%. A própolis de Botucatu foi a mais eficiente sobre S. aureus (0,3%v/v), Enterococcus sp (1,1%v/v) e C. albicans (2,1% v/v). Para E. coli, a própolis eficiente foi de Urubici (7,0%v/v) e para P. aeruginosa a de Mossoró (5,3%v/v). Os resultados mostram maior sensibilidade das bactérias Gram positivas e levedura em relação às Gram negativas. É possível concluir que, para os microrganismos testados e amostras de própolis testadas, há diferenças na atividade antimicrobiana em função do local de produção e que isso se explica pela diferença de composição química da própolis.

The antimicrobial activity of Apis mellifera propolis is widely reported, and the variations in this property according to the region where it was produced have been mentioned. Thus, the antimicrobial activity of propolis from three Brazilian regions (Botucatu, SP; Mossoró, RN and Urubici, SC) was investigated on isolated strains from human clinical material (Staphylococcus aureus, Escherichia coli, Enterococcus sp, Pseudomonas aeruginosa, and Candida albicans). Ethanolic Extracts of Propolis (EEP) were prepared and the Minimal Inhibitory Concentration (MIC) was determined based on the method of EEP dilution in agar and the MIC90% calculated. Propolis from Botucatu was the most effective against S. aureus (0.3%v/v), Enterococcus sp (1.1%v/v), and C. albicans (2.1% v/v). The effective propolis against E. coli was from Urubici (7.0%v/v), and against P. aeruginosa, from Mossoró (5.3%v/v). The results shows that there are differences in the activity according to the region where the propolis were produced and Gram positive bacteria were more susceptible that Gram negative bacteria.

Propolis is a natural resinous substance collected by bees from tree exudates and secretions. Its antimicrobial activity has been investigated and inhibitory action on Staphylococcus aureus growth was evaluated. The in vitro synergism between ethanolic extract of propolis (EEP) and antimicrobial drugs by two susceptibility tests (Kirby and Bauer and E-Test) on 25 S. aureus strains was evaluated. Petri dishes with sub-inhibitory concentrations of EEP were incubated with 13 drugs using Kirby and Bauer method and synergism between EEP and five drugs [choramphenicol (CLO), gentamicin (GEN), netilmicin (NET), tetracycline (TET), and vancomycin (VAN)] was observed. Nine drugs were assayed by the E-test method and five of them exhibited a synergism [CLO, GEN, NET, TET, and clindamycin (CLI)]. The results demonstrated the synergism between EEP and antimicrobial drugs, especially those agents that interfere on bacterial protein synthesis.