Carvacrol (CV) is a phenolic monoterpenoid found in essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), pepperwort (Lepidium flavum), wild bergamot (Citrus aurantium bergamia), and other plants. Carvacrol possesses a wide range of bioactivities putatively useful for clinical applications such antimicrobial, antioxidant, and anticancer activities. Carvacrol antimicrobial activity is higher than that of other volatile compounds present in essential oils due to the presence of the free hydroxyl group, hydrophobicity, and the phenol moiety. The present review illustrates the state-of-the-art studies on the antimicrobial, antioxidant, and anticancer properties of CV. It is particularly effective against food-borne pathogens, including Escherichia coli, Salmonella, and Bacillus cereus. Carvacrol has high antioxidant activity and has been successfully used, mainly associated with thymol, as dietary phytoadditive to improve animal antioxidant status. The anticancer properties of CV have been reported in preclinical models of breast, liver, and lung carcinomas, acting on proapoptotic processes. Besides the interesting properties of CV and the toxicological profile becoming definite, to date, human trials on CV are still lacking, and this largely impedes any conclusions of clinical relevance.
This is the first known description of ESBL-producing and AmpC β-lactamase-producing Shigella and of PMQR Shigella in Iran. The emergence of CTX-15, CMY-2 and qnrS1 genes may compromise the treatment of shigellosis. Strategies to minimize the spread of ESBL-producing and AmpC-β-lactamase-producing Shigella should be implemented.
Cathelicidins are a family of antimicrobial peptides which exhibit broad antimicrobial activities against antibiotic-resistant bacteria. Considering the progressive antibiotic resistance, cathelicidin is a candidate for use as an alternative approach to treat and overcome the challenge of antimicrobial resistance. Cathelicidin-BF (Cath-BF) is a short antimicrobial peptide, which was originally extracted from the venom of Bungarus fasciatus. Recent studies have reported that Cath-BF and some related derivatives exert strong antimicrobial and weak hemolytic properties. This study investigates the bactericidal and cytotoxic effects of Cath-BF and its analogs (Cath-A and Cath-B). Cath-A and Cath-B were designed to increase their net positive charge, to have more activity against methicillin resistant S. aureus (MRSA). The results of this study show that Cath-A, with a +17-net charge, has the most noteworthy antimicrobial activity against MRSA strains, with minimum inhibitory concentration (MIC) ranging between 32-128 μg/ml. The bacterial kinetic analysis by 1 × MIC concentration of each peptide shows that Cath-A neutralizes the clinical MRSA isolate for 60 min. The present data support the notion that increasing the positive net charge of antimicrobial peptides can increase their potential antimicrobial activity. Cath-A also displayed the weakest cytotoxicity effect against human umbilical vein endothelial and H9c2 rat cardiomyoblast cell lines. Analysis of the hemolytic activity reveals that all three peptides exhibit minor hemolytic activity against human erythrocytes at concentrations up to 250 μg/ml. Altogether, these results suggest that Cath-A and Cath-B are competent candidates as novel antimicrobial compounds against MRSA and possibly other multidrug resistant bacteria.
The objective of this study was to assess the genotypic diversity associated with antimicrobial susceptibility of Salmonella serovars isolated from patients arriving with diarrhoea to six hospitals of Tehran, Iran. During 2007-2008, a cross-sectional convenience study was performed. Stool samples were screened for the presence of Salmonella, serotyped, tested for antimicrobial susceptibility using disk diffusion and examined for the presence of relevant resistance genes and integrons by PCR. A total of 1,120 patients were screened for the presence of Salmonella. Out of 71 Salmonella isolates recovered, the following serovars were identified: 17 Typhi, 14 Paratyphi C, 13 Enteritidis, 11 Paratyphi B, 10 Paratyphi A and six Infantis. Most resistance was observed towards sulfamethoxazole (30%), tetracyclines (25%), nalidixic acid (22%), spectinomycin (17%), trimethoprim (15%), ampicillin (14%) and kanamycin (14%). The tetracycline resistance genes tet(A), tet(B), and tet(G) were found in 28%, 14% and 6% of the tetracycline resistant isolates, respectively. The genes aadA, aadB, strA, strB and aphA1-Iab were present in 83%, 55%, 34%, 1% and 17% of the aminoglycoside resistant isolates, respectively. Additionally, bla (PSE) and bla (TEM) β-lactamase genes were detected in 63% and 18% of the ampicillin-resistant isolates. The 23 sulphonamide resistant isolates harboured sul1 and intI1 genes, typical to class 1 integrons. Nine of these isolates also yielded amplicons for intI2 (class 2 integrons). The presence of multi-drug resistant Salmonella may compromise the successful treatment of enteric infection diseases. The enforcement of strict prescription practices will help to minimise the emergence of resistance.
The increasing incidence of antimicrobial resistance bacterial infection and decreasing effectiveness of conventional antibiotics to treatment have caused serious problems worldwide. The demand for new generationantibiotics to combat microbial pathogens is imperative. Cationic antimicrobial peptides (AMPs) with different sources from prokaryotic to complex eukaryotic organisms, with variable length, amino acid composition and secondary structure, have been consideredduring the past decades. The advantages of large number of AMPs are related to broad spectrum and morphogenetic activities, low resistance rate among microorganismswithout side effect on human cells, rapid killing of bacteria via membrane damage and intracellular targets,and their critical roles in anti-inflammatory. Ribosomal synthesized peptides of Gram positive bacteria with various post translational modificationsrepresent extended types of antimicrobial peptide with different structural and functional diversity. These types of peptides have been considered as new therapeutic agents for pharmaceutical development .In addition, non- ribosomal synthesized peptides are a wide range of peptides , an extremely extensive range of biological activities and pharmacological properties that are not synthesized by ribosomes, show interesting biological properties ranging from antibiotic to bio surfactants. This review focused on genetics, mechanism of action and modifications, resistance mode of Gram positive bacteria to AMPs and the biotechnological application of ribosomally and non-ribosomally synthesized peptides derived from Gram positive bacteria.
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