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Sinergia con antibiotici ed azione anti-virulenza di fitocomposti bioattivi
No full textL’aumentata diffusione di patogeni antibiotico-resistenti e la mancanza di nuove molecole antibiotiche ha risvegliato l'interesse nei confronti di fitocomposti come possibili agenti antimicrobici. Vengono esposti i risultati di nostri studi recenti riguardanti l'azione sinergica con antibiotici e le proprietà anti-virulenza di alcuni fitocomposti nei confronti di ceppi clinici di patogeni umani multi-resistenti, produttori di biofilm e invasivi per cellule. Gli studi sull’attività antimicrobica di carvacrolo (monoterpene fenolico presente negli oli essenziali di Thymus vulgaris e Origanum vulgare) e di capsaicina (alcaloide presente in piante del genere Capsicum), nei confronti di Streptococcus pyogenes, eritromicino-resistenti ed invasivi per cellule respiratorie umane, hanno dimostrato che, a concentrazioni sub-MIC, il carvacrolo agiva in sinergia (FICI≤0.5) con eritromicina e che la capsaicina, riduceva l’espressione della streptolisina O e la capacità di invadere cellule respiratorie A549. Gli studi sull’attività antimicrobica di curcumina (composto polifenolico presente nel rizoma di Curcuma longa) nei confronti di Mycobacterium abscessus, multi-resistente e produttore di biofilm, hanno dimostrato che, a concentrazioni sub-MIC, la curcumina agiva in sinergia con amikacina, claritromicina, ciprofloxacina, e linezolid ed era in grado di disgregare il biofilm maturo. Studi più recenti sull’attività anti-virulenza di olio essenziale di Cannabis sativa L. [varietà di canapa a basso contenuto di THC (<0.2%), ad uso industriale] nei confronti di Listeria monocytogenes da casi di listeriosi umana invasiva, hanno dimostrato che, a concentrazioni sub-letali, l’olio essenziale era in grado di ridurre la produzione di biofilm, la motilità, la capacità di invadere cellule epiteliali intestinali umane Caco-2 e di aumentare la sopravvivenza di larve infettate di Galleria mellonella. In un momento storico in cui l’aumento dei patogeni multi-resistenti costituisce una vera e propria emergenza sanitaria, per combattere la quale gli antibiotici a disposizione sono sempre gli stessi, una strategia che sfrutti la sinergia con antibiotici tradizionali oppure l’azione anti-virulenza di fitocomposti offre nuove prospettive alla lotta contro l’antibiotico resistenza. In particolare, l’azione anti-virulenza presenta dei vantaggi rispetto agli antibiotici in quanto non esercita una pressione selettiva verso l’antibiotico-resistenza
Association between erythromycin resistance and ability to enter human respiratory cells in group A streptococci.
No full textOngoing outbreak of invasive listeriosis due to serotype 1/2a Listeria monocytogenes, Ancona province, Italy, January 2015 to February 2016.
No full textIn the first seven weeks of 2016, five serotype 1/2a Listeria monocytogenes isolates were collected from patients with invasive listeriosis in Ancona province in Italy. These strains and six 1/2a isolates identified in 2015 in the same area were typed by ERIC-PCR and PFGE. A clonal relationship, documented between the two sets of isolates, suggested a listeriosis outbreak in Ancona that started most probably in 2015. Investigation into the source of infection is still ongoing
Antibiofilm activity of zinc-carbonate hydroxyapatite nanocrystals against Streptococcus mutans and mitis group streptococci
Full text linkPersistence of erythromycin-resistant group a streptococci in cultured respiratory cells.
No full textRecombination between Streptococcus suis ICESsu32457 and Streptococcus agalactiae ICESa2603 yields a hybrid ICE transferable to Streptococcus pyogenes
Full text linkIntegrative conjugative elements (ICEs) are mobile genetic elements that reside in the chromosome but retain the ability to undergo excision and to transfer by conjugation. Genes involved in drug resistance, virulence, or niche adaptation are often found among backbone genes as cargo DNA. We recently characterized in Streptococcus suis an ICE (ICESsu32457) carrying resistance genes [tet(O/W/32/O), tet(40), erm(B), aphA, and aadE] in the 15K unstable genetic element, which is flanked by two ∼1.3kb direct repeats. Remarkably, ∼1.3-kb sequences are conserved in ICESa2603 of Streptococcus agalactiae 2603V/R, which carry heavy metal resistance genes cadC/cadA and mer. In matings between S. suis 32457 (donor) and S. agalactiae 2603V/R (recipient), transconjugants were obtained. PCR experiments, PFGE, and sequence analysis of transconjugants demonstrated a tandem array between ICESsu32457 and ICESa2603. Matings between tandem array-containing S. agalactiae 2603V/R (donor) and Streptococcus pyogenes RF12 (recipient) yielded a single transconjugant containing a hybrid ICE, here named ICESa2603/ICESsu32457. The hybrid formed by recombination of the left ∼1.3-kb sequence of ICESsu32457 and the ∼1.3-kb sequence of ICESa2603. Interestingly, the hybrid ICE was transferable between S. pyogenes strains, thus demonstrating that it behaves as a conventional ICE. These findings suggest that both tandem arrays and hybrid ICEs may contribute to the evolution of antibiotic resistance in streptococci, creating novel mobile elements capable of disseminating new combinations of antibiotic resistance genes
43rd NATIONAL CONGRESS OF THE ITALIAN SOCIETY OF MICROBIOLOGY
No full textIntroduction: Capsaicin (8-methyl-N-vanillyl-
6-nonenamide) is the active component responsible
for the fruit pungency of Capsicum plants,
cultivated for food and also for medicinal uses since
ancient times. Besides its multiple pharmacological
and physiological properties (pain relief, cancer
prevention, weight reduction, cardiovascular, and
gastrointestinal benefits), capsaicin has recently
received attention because of its antimicrobial activity
and anti-virulence properties. The aim of the
present study was to investigate the effects of capsaicin
on Streptococcus pyogenes, the most common
cause of acute bacterial pharyngotonsillitis.
Materials and Methods: The erythromycin-resistant
[erm(B)/cMLS], high cell-invasive, and strong
biofilm producer S. pyogenes pharyngeal isolate
SP1070 was used throughout the study. Capsaicin
was purchased from Sigma-Aldrich and stored (10
mg/mL stock solution) in absolute ethanol at -20°C.
The MIC and MBC were determined according to
the CLSI guidelines. Survival in presence of capsaicin
was studied by the live/dead assay. Biofilm
formation was tested by a microtiter assay and
quantified by measuring the absorbance at 690 nm.
Cell experiments were performed using the human
alveolar carcinoma A549 cell line.
Results: The MIC and the MBC of capsaicin were
both 128 μg/mL. In the live/dead assay, several red
cells were detected as early as 15 min after incubation
with capsaicin at MIC; all cells were red after
60 min of incubation. At capsaicin sub-MICs (1/2– 1/16 × MIC), a significant increase in biofilm production
and in the number of streptococci adherent
to A549 cells was observed; whereas a strong reduction
in the number of intracellular bacteria was
detected.
Discussion and Conclusions: Our findings reveal
that capsaicin has a dual effect on S. pyogenes.
High-level capsaicin exerts a bactericidal effect,
probably due to the disruption of the cell membrane,
this result being in agreement with previous
studies on Gram-positive and Gram-negative
pathogens; while sub-lethal capsaicin modifies
virulence properties in vitro, such as the ability to
form biofilm and to adhere/invade epithelial cells.
Capsaicin-induced effects on biofilm formation
seem to be similar to those observed for a variety of
antibiotics that at sub-lethal concentrations can act
as agonists of bacterial biofilm production in vitro.
Overall, capsaicin-induced effects on S. pyogenes
deserve further studies
Antimicrobial activity of essential oils and carvacrol, and synergy of carvacrol and erythromycin, against clinical, erythromycin-resistant Group A Streptococci.
Full text linkIn the present study, we have evaluated the in vitro antibacterial activity of essential oils from Origanum vulgare, Thymus vulgaris, Lavandula angustifolia, Mentha piperita, and Melaleuca alternifolia against 32 erythromycin-resistant [MIC ≥1 µg/mL; inducible, constitutive, and efflux-mediated resistance phenotype; erm(TR), erm(B), and mef(A) genes] and cell-invasive Group A streptococci (GAS) isolated from children with pharyngotonsillitis in Italy. Over the past decades erythromycin resistance in GAS has emerged in several countries; strains combining erythromycin resistance and cell invasiveness may escape β-lactams because of intracellular location and macrolides because of resistance, resulting in difficulty of eradication and recurrent pharyngitis. Thyme and origanum essential oils demonstrated the highest antimicrobial activity with MICs ranging from 256 to 512 µg/mL. The phenolic monoterpene carvacrol [2-Methyl-5-(1-methylethyl) phenol] is a major component of the essential oils of Origanum and Thymus plants. MICs of carvacrol ranged from 64 to 256 µg/mL. In the live/dead assay several dead cells were detected as early as 1 h after incubation with carvacrol at the MIC. In single-step resistance selection studies no resistant mutants were obtained. A synergistic action of carvacrol and erythromycin was detected by the checkerboard assay and calculation of the FIC Index. A 2- to 2048-fold reduction of the erythromycin MIC was documented in checkerboard assays. Synergy (FIC Index ≤0.5) was found in 21/32 strains and was highly significant (p <0.01) in strains where resistance is expressed only in presence of erythromycin. Synergy was confirmed in 17/23 strains using 24-h time-kill curves in presence of carvacrol and erythromycin. Our findings demonstrated that carvacrol acts either alone or in combination with erythromycin against erythromycin-resistant GAS and could potentially serve as a novel therapeutic tool
Interspecies mobilization of an erm(T)-carrying plasmid of Streptococcus dysgalactiae subsp. equisimilis by a coresident ICE of the ICESa2603 family.
No full textOBJECTIVES: The recently documented presence of almost identical, small, non-self-transmissible, erm(T)-carrying plasmids in clonally unrelated erythromycin-resistant isolates of Streptococcus pyogenes and Streptococcus
agalactiae suggests that these plasmids somehow circulate in the streptococcal
population. The objective of this study was to characterize the erm(T)-carrying
genetic element in a clinical isolate of Streptococcus dysgalactiae subsp.
equisimilis (Sde5580) and to provide a possible explanation for the spread of
erm(T)-carrying plasmids in streptococci.
METHODS: The erm(T)-carrying element of Sde5580 was investigated by plasmid
analysis, PCR experiments and sequencing. Transfer and retransfer experiments
were performed using S. pyogenes, S. agalactiae and Streptococcus suis strains as
recipients and by selection in the presence of suitable drug concentrations.
Transconjugants were analysed by SmaI-macrorestriction analysis. Genetic studies
also included PCR-restriction fragment length polymorphism analysis using HindIII
endonuclease.
RESULTS: Sde5580 contained two mobile genetic elements: a 4950 bp erm(T)-carrying
plasmid (p5580) almost identical to the non-self-transmissible erm(T)-carrying
plasmids of S. pyogenes and S. agalactiae mentioned above, and an ~63 kb
cadC/cadA-carrying integrative and conjugative element (ICESde3396-like) of the
ICESa2603 family. p5580 was transferable at high frequency to the recipients of
all three species through in trans mobilization by the coresident ICESde3396-like
element. p5580 and ICESde3396-like were able to be transferred either separately
or together.
CONCLUSIONS: This is the first evidence of horizontal transfer of an
erm(T)-carrying plasmid between streptococci. In trans mobilization by coresident
ICEs may be one mechanism for the spread of erm(T)-carrying plasmids in the streptococcal population
Characterization of a Streptococcus suis tet(O/W/32/O)-carrying element transferable to major streptococcal pathogens.
No full textMosaic tetracycline resistance determinants are a recently discovered class of hybrids of ribosomal protection tet genes. They may show different patterns of mosaicism, but their final size has remained unaltered. Initially thought to be confined to a small group of anaerobic bacteria, mosaic tet genes have then been found to be widespread. In the genus Streptococcus, a mosaic tet gene [tet(O/W/32/O)] was first discovered in Streptococcus suis, an emerging drug-resistant pig and human pathogen. In this study we report the molecular characterization of a tet(O/W/32/O) gene-carrying mobile element from a S. suis isolate. tet(O/W/32/O) was detected, in tandem with tet (40), in a circular 14,741-bp genetic element [39.1% G+C; 17 open reading frames (ORFs) identified]. The novel element, that we designated 15K, also carried the macrolide resistance determinant erm(B) and an aminoglycoside resistance four-gene cluster including aadE (streptomycin) and aphA (kanamycin). 15K appeared to be an unstable genetic element that, in the absence of recombinases, is capable of undergoing spontaneous excision under standard growth conditions. In the integrated form, 15K was found inside a 54,879-bp integrative and conjugative element (ICE) (50.5% G+C; 55 ORFs), that we designated ICESsu32457. An ∼1.3-kb segment was identified that apparently served as the att site for excision of the unstable 15K element. The novel ICE was transferable at high frequency to recipients from pathogenic Streptococcus species (S. suis, Streptococcus pyogenes, Streptococcus pneumoniae, and Streptococcus agalactiae), suggesting that the multiresistance 15K element can successfully spread within streptococcal populations
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