Growth inhibition and morphological alterations of Staphylococcus aureus caused by the essential oil of Aloysia triphylla / Inhibición del crecimiento y alteraciones morfológicas de Staphylococcus aureus causadas por el aceite esencial de Aloysia triphylla

Aloysia triphylla essential oil (EO) has antimicrobial activity on Staphylococcus aureus which is a pathogen responsible for severe infections and food contamination. The target of EO is mainly in the cytoplasmic membrane. In this work the mechanisms of action of the EO of A. triphylla on S. aureus were investigated. A. triphylla was collected from La Paz. The oil was analyzed by GC-MS. The antimicrobial effects were evaluated by MIC, MBC, killing time and TEM. MIC values were 23 μg/mL for 6.3 x 104 CFU/mL, 92 μg/mL for 5.71 x 105 CFU/mL and 180 μg/mL for 9 x 106 CFU/mL. The MBC was 5920 μg/mL for all cellular concentrations and it was necessary more time to kill bigger cell populations. Multilamellar and mesosome-like structures on the membrane were seen by TEM. A. triphylla oil is an antibacterial compound against S. aureus which main mechanism of action seems to be the cytoplasmic membrane disruption.

El aceite esencial (AE) de Aloysia triphylla posee actividad antimicrobiana contra Staphylococcus aureus, patógeno responsable de infecciones nosocomiales e alimenticias. El blanco de acción de los AE es la membrana citoplasmática. El mecanismo de acción del AE de A. triphylla sobre S. aureus fue investigado. El AE de A. triphylla (La Paz, Argentina) fue analizado por CG-EM. Se evaluó́ el efecto antimicrobiano por CIM, CBM, tiempo de muerte y MET. Los valores de CIM fueron 23 μg/mL para 6.3 x 104 UFC/mL, 92 μg/mL para 5.71 x 105 UFC/mL y 180 μg/mL para 9 x 106 UFC/mL. La CBM fue 5920 μg mL para todas las concentraciones celulares estudiadas. El tiempo de muerte fue determinado; necesitando mayor tiempo para matar una población celular elevada. Fueron observados por MET estructuras multilamerales y semejantes a mesosomas. El AE de A. triphylla es un potencial compuesto antibacteriano contra S. aureus donde su principal mecanismo de acción es por disrupción de la membrana citoplasmática.

Structure and antimicrobial activity of phloroglucinol derivatives from Achyrocline satureioides.

The new prenylated phloroglucinol α-pyrones 1-3 and the new dibenzofuran 4, together with the known 23-methyl-6-O-demethylauricepyrone (5), achyrofuran (6), and 5,7-dihydroxy-3,8-dimethoxyflavone (gnaphaliin A), were isolated from the aerial parts of Achyrocline satureioides. Their structures were determined by 1D and 2D NMR spectroscopic studies, while the absolute configuration of the sole stereogenic center of 1 was established by vibrational circular dichroism measurements in comparison to density functional theory calculated data. The same (S) absolute configuration of the α-methylbutyryl chain attached to the phloroglucinol nucleus was assumed for compounds 2-6 based on biogenetic considerations. Derivatives 7-16 were prepared from 1 and 5, and the antimicrobial activities of the isolated metabolites and some of the semisynthetic derivatives against a selected panel of Gram-positive and Gram-negative bacteria, as well as a set of yeast molds, were determined.

Achyrofuran is an antibacterial agent capable of killing methicillin-resistant vancomycin-intermediate Staphylococcus aureus in the nanomolar range.

Currently, there is a pressing need for novel antibacterial agents against drug-resistant bacteria, especially those which have been common in our communities and hospitals, such as methicillin-resistant Staphylococcus aureus (MRSA). The South American plant Achyrocline satureioides ("Marcela") has been widely used in traditional medicine for a number of diseases, including infections. Several crude extracts from this plant have shown good antimicrobial activities in vitro. In the search for the active principle(s) that confers these antimicrobial activities, we have processed the dichloromethane extract from the aerial parts of the plant. One of the isolated compounds showed extraordinary antibacterial activities against a set of clinically relevant Gram-positive strains that widely differ in their antibiogram profiles. This compound was identified as achyrofuran on the basis of its spectroscopic and physical data. We determined the MIC to be around 0.1 µM (0.07 µg/ml) for the reference methicillin-resistant and vancomycin-intermediate S. aureus strain NRS402. Moreover, nanomolar concentrations of achyrofuran killed 10(6) bacteria within 12 h. Based on the presence of the 2,2'-biphenol core, we further studied whether achyrofuran killed bacteria through a mechanism of action similar to that reported for the naturally occurring antibiotic MC21-A. Indeed, we found that achyrofuran was not bacteriolytic by itself although it greatly compromised membrane impermeability as determined by increased SYTOX Green uptake.

Antimycotic effect of the essential oil of Aloysia triphylla against Candida species obtained from human pathologies.

The research of alternative substances to treat infections caused by Candida species is a need. Aromatic plants have the ability to produce secondary metabolites, such as essential oils (EO). The antimicrobial properties of Aloysia triphylla (L'Her.) Britton (cedrón) EO has been previously described. The aims of this work were to determine the antimicrobial activity and the effect on the cell structure of the EO of A. triphylla against Candida sp isolated from human illnesses. The EO was obtained by hydrodistillation of A. triphylla leaves. The minimum inhibitory concentration (MIC) was performed with microdilution method and the minimum fungicidal concentration (MFC) was determined. A. triphylla EO's showed antifungal activity against all yeast: C. albicans, C. dubliniensis, C. glabrata, C. krusei, C. guillermondii, C. parapsilosis and C. tropicalis which were resistant to fluconazol (150 mg/mL). The range of MIC values was from: 35 to 140 microg/mL and the MFC: 1842 to 2300 microg/mL. The time of killing at the MFC against C. albicans (3 x 10(5) UFC/mL) was 140 min. The dates of OD620 and OD260 suggest lysis and loss of absorbing material, respectively. The HROM shows distortion in morphology and shape of the cell, with large vacuoles in the cytoplasm. These studies clearly show that A. triphylla EO is a promising alternative for the treatment of candidiasis.

Virulence factors and antimicrobial resistance of Staphylococcus aureus isolated from bovine mastitis in Rio de Janeiro / Fatores de virulência e resistência antimicrobiana em Staphylococcus aureus isolados de mastite bovina no Rio de Janeiro

The study was conducted to characterize pheno-genotypically the virulence factors and resistance pattern of Staphylococcus aureus isolates from milk samples of cows with subclinical mastitis. All hemolytic isolates presented beta-hemolysin, and 38 percent of the non-hemolytic isolates were able to express hemolysins in the presence of a beta-hemolytic strain. The amplification of the coa-gene displayed four different size polymorphisms with about 400 bp, 600 bp, 700 bp and 900 bp. The spaA gene that encodes the IgG-binding region of protein A revealed sizes of 700 bp and 900 bp. The amplification of region X from spaA yielded a single amplicon for each isolate with the prevalent amplicon size being of 180 bp. Amplification of sae gene yielded an amplicon size of 920 bp in 71 percent of the isolates. Antibiotic resistance pattern revealed that 42 percent S. aureus were susceptible to all antimicrobials tested. Seven different antibiotic patterns were observed. Our results indicated that 47 percent and 25 percent of S. aureus strains exhibited resistance to penicillin and oxacillin respectively. All oxacillin-resistant isolates were mecA-positive.

O presente estudo foi conduzido com o objetivo de caracterizar feno-genotipicamente os fatores de virulência e perfil de resistência aos antibióticos de Staphylococcus aureus isolados de amostras de leite de vacas com mastite clínica e subclínica. Em todos os isolados hemolíticos foi detectada a presença de beta hemolisina e 38 por cento dos não-hemolíticos produziram hemolisinas na presença de cepa beta-hemolítica. A amplificação do gene coa apresentou quatro tipos polimórficos distintos com aproximadamente 400 bp, 600 bp, 700 bp e 900 bp. O gene spaA que codifica a região de ligação da proteína A à IgG apresentou bandas de 700 bp e 900 bp. A amplificação do gene que codifica a região X revelou um único amplicon para cada isolado sendo o tamanho prevalente o de 250pb. A amplificação do gene sae resultou em amplicons com 920 pb em 71 por cento dos isolados. O teste de suscetibilidade antimicrobiana revelou que 42 por cento dos S. aureus foram sensíveis a todos os antibióticos testados. Foram observados sete diferentes padrões de resistência. Os resultados indicaram que 47 por cento e 25 por cento dos isolados foram resistentes à penicilina e oxacilina, respectivamente. Todos os isolados resistentes à oxacilina foram positivos para o gene mecA.

Chemical constituents and antimicrobial activity of the essential oil of Lantana xenica.

The aim of this work was to evaluate the chemical composition of Lantana xenica essential oil and its antimicrobial activity. The oil from the aerial parts of Lantana xenica Mold. (Verbenacea) was obtained by steam distillation and analyzed by gas chromatography/mass spectrometry. The major constituent of the oil was (E)-caryophyllene (35.2 %), with minor amounts of gamma-cadinene (13.3 %), alpha-pinene (9.3 %), ocimene (9.2 %) and germacrene D (6.6 %). The antimicrobial assays showed that the essential oil of L. xenica inhibited the growth of Bacillus cereus and Proteus mirabilis and both bacteria were inhibited by (E)-caryophyllene, the major component of the oil. Enterococcus faecalis, Staphylococcus epidermidis and S. aureus showed a lower inhibition. The bacteria Micrococcus luteus, Klebsiella sp., Escherichia coli and the yeast Candida albicans were insensitive to both the oil and (E)-caryophyllene.