Letters in Applied Microbiology

Actinomycetes produce secondary metabolites with many bioactivities such as antimicrobial, which can be useful as alternatives against resistant bacterial strains. Therefore, the screening of new habitats is likely to provide new strains with high potential. In this work, the antimicrobial capacity was used to select Streptomyces sp. strains isolated from Raf Raf forest (Tunisia). From the strain displaying higher activity, FR7, an ethyl acetate extract was prepared under optimized culturing conditions (10 days at 30 ºC in ISP2 medium with initial pH 8), showing significant antimicrobial activity against Micrococcus luteus and Staphylococcus aureus (MIC = 5 μg ml-1), and Listeria monocytogenes and Pseudomonas aeruginosa (MIC = 20 μg ml-1)...

Oral candidiasis (OC) is the most frequent opportunistic fungal infection, which is a predictive indicator of immunosuppression and disease progression among people living with HIV/AIDS (PLWHA). In the present study, 109 Candida isolates were collected from 94 PLWHA afflicted with oral Candida infection (OCI) following highly active antiretroviral therapy (HAART). The susceptibility profiles of Candida spp. to six antifungal agents were evaluated using CLSI broth microdilution. The prevalence of OCI was 34...

Enterococci are commensals of the human intestinal tract. Their use as probiotics is supported by their ability to confer several health benefits and eliminate foodborne pathogens but is controversial due to the presence of virulence and antibiotic resistance traits. To use them as probiotics requires thorough research to establish their safety. Here we sequenced the whole genome of a newly isolated Enterococcus durans MN187066 and used a suite of bioinformatics tools to analyze its beneficial probiotic traits as well as antimicrobial resistance and virulence genes...

The prophylactic and therapeutic overuse of antimicrobials on the farm has contributed to the emergence of hard-to-fight bacterial strains causing bovine mastitis. Aiming at alternative therapies, this study evaluated the antimicrobial activity of 20 essential oils against clinical Staphylococcus aureus strains. Of them, five with strong activities were selected and evaluated for their minimum inhibitory concentrations (MIC) in culture medium and milk, cytotoxicity against bovine mammary cells (MAC-T), anti-adhesive properties, and interactions among themselves and with cefoperazone...

Efficacy of cleaning methods against SARS-CoV-2 suspended in either 5% soil load (SARS-soil) or simulated saliva (SARS-SS) were evaluated immediately (hydrated virus, T0) or 2 hours post-contamination (dried virus, T2). Hard water dampened wiping (DW) of surfaces, resulted in 1.77-3.91 log reduction (T0) or 0.93-2.41 log reduction (T2). Incorporating surface pre-wetting by spraying with a detergent solution (D+DW) or hard water (W+DW) just prior to dampened wiping did not unilaterally increase efficacy against infectious SARS-CoV-2, however the effect was nuanced with respect to surface, viral matrix, and time...

The present work aimed to produce a cupuassu juice (Theobroma grandiflorum) fermented by the probiotic bacterium Lactiplantibacillus plantarum Lp62 and to analyze its antioxidant potential, antimicrobial activity and resistance to biological barriers. The fermented beverage showed an increase in the content of phenolics, flavonoids and antioxidant potential. The culture showed antagonistic activity against pathogens, but this result was not observed when the juice was tested. The probiotic strain remained viable under refrigeration, even in an acidified environment, and survived simulated gastrointestinal transit in vitro...

Biofilms are used widely to remove nitrogen from wastewater; however, most biofilm carriers (i.e. polyurethane foam, PUF) are hydrophobic organic materials with millimetre-scale apertures, ineffective attachment, and unstable colonisation of microorganisms. To address these limitations, hydrophilic sodium alginate (SA) mixed with zeolite powder (Zeo) was crosslinked in PUF to form a micro-scale hydrogel (PAS) with a well-organised and reticular cellular structure. Scanning electron microscopy revealed that immobilised cells were entrapped in the interior of hydrogel filaments and rapidly formed a stable biofilm on the surface...

Coxiella burnetii, the causative agent of Q fever, is a small, coccoid, Gram-negative strict intracellular pathogen. One of the most common ways of acquiring Q fever is through inhalation of aerosols containing the bacteria. Because C. burnetii is highly infectious, spreads easily through the air, and is very resistant to environmental conditions, it is considered a biological threat. This paper presents the development and validation of a specific real-time polymerase chain reaction (real-time PCR or qPCR) assay for the detection of C...

This study aimed to standardize the use of an ex vivo wound model for the evaluation of compounds with antibiofilm activity. The in vitro susceptibility of Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 27853 to ciprofloxacin and polyhexamethylene biguanide (PHMB) was evaluated in planktonic and biofilm growth. The effects of ciprofloxacin and PHMB on biofilms grown on porcine skin explants were evaluated by CFU-counting and confocal microscopy. MICs against S. aureus and P. aeruginosa were, respectively, 0...

No abstract text is available yet for this article.

Acinetobacter baumannii is a well-known nosocomial pathogen that commonly inhabits soil and water and has been implicated in numerous hospital-acquired infections. The existing methods for detecting A. baumannii have several drawbacks, such as being time-consuming, expensive, labor-intensive, and unable to distinguish between closely related Acinetobacter species. Thus, it is important to have a simple, rapid, sensitive, and specific method for its detection. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay using hydroxynaphthol blue dye to visualize A...

Human saliva contains natural antimicrobial enzymes. In this in vitro study, we evaluate the antimicrobial activity of a dentifrice containing a salivary enzyme complex (SEC) with xylitol versus a standard 0.12% chlorhexidine (CHX) dentifrice. Adherent cells of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, Fusobacterium nucleatum subsp polymorphum and Corynebacterium matruchotii were exposed to SEC-xylitol and CHX dentifrices for 2 mins and viable CFUs were enumerated. Exposure to the SEC-xylitol dentifrice resulted in a significant reduction in bacterial viability, which was greater than that shown by the CHX dentifrice, against all organisms tested...

Probiotics are known to possess strain and species-specific functional properties, of which hypocholesteremia is of major interest. Bile salt hydrolase (BSH) activity is one of the key mechanism involved in hypocholesterolemic effect. The study was designed to genetically characterize probiotics from human milk on the basis of Simple Sequence Repeat (SSR), isolate potent hypocholesterolemic strains, detect BSH activity, deconjugation of bile salts and bsh polymorphism. Current study, for the first-time, linked genetic diversity with cholesterol reduction potential and prove presence of conserved bsh of Levilactobacillus brevis in genetically diverse species...

Mangroves create an ecological environment for a diverse assemblage of organisms, including marine and mangrove oomycetes. Halophytophthora spp., in particular, are isolated from fallen senescent mangrove leaves. Studies reported on Philippine oomycetes are mostly on their distribution and taxonomy; while fatty acid studies have not yet been fully explored. Recently, oomycetes were reported as efficient producers of various fatty acids, therefore, bioprospecting efforts are aimed at obtaining more industrially important fatty acid compounds for aquaculture, biodiesel production, and human consumption...

Aflatoxin (AFs)-contaminated diet in feeding domestic animals is one of the biggest health concerns for humans. Therefore, various methods have been developed to detoxify AFs. In the present study, adding Saccharomyces cerevisiae probiotic yeast and titanium dioxide nanoparticles (TiO2-NPs) reduces the toxicity of Aflatoxin B1 (AFB1) in laying hens was studied. After preparing laying hens, they were fed with a diet containing AFB1 for 14 days and supplemented with Saccharomyces cerevisiae and TiO2-NPs. Weight changes, serum levels of albumin, globulin, total protein, aspartate transaminase (AST), and alanine transaminase (ALT) were measured over 14 days...

The ecological state of Lake Sevan, the largest drinking water reservoir for the South Caucasus, formed under the influence of climatic and social changes. This study assesses the bacteriological quality of water in the rivers of the Lake Sevan basin and tetracycline-resistant bacteria isolated from fish and people living near the rivers of the Lake Sevan basin in Armenia in autumn 2019 and spring 2020. No differences have been shown for the tetracycline resistance of investigated E. coli isolated from the human gut and the Masrik, Argichi, and Gavaraget Rivers...

Zearalenone (ZEN) is an estrogenic mycotoxin produced by the Fusarium species and induces severe reproductive disorders in animals thus a major concern in the livestock industry. Probiotic bacteria treatments have been shown to inactivate mycotoxins, therefore, in this study, we investigated the effect of two commercial probiotic feed additives on the sequestration of ZEN. Commercial probiotic blends containing clay-based binder with Aspergillus niger, Bacillus licheniformis, Bacillus pumilus, and Bacillus subtilis at various proportions from BioMatrix International were incubated with ZEN in a time-dependent manner and then analyzed by ELISA to quantify unbound ZEN...

Biofilms are surface-associated microbial clusters embedded in extracellular polymeric substances (EPSs). Biofilms formed on food contact surfaces create challenges for the food industry due to their increased tolerance to antimicrobial agents and disinfectants. This study aimed to evaluate the effect of the biofilm maturation period on their resistance to gaseous ClO2. Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157: H7 biofilms formed on stainless steel (SS) and high-density polyethylene (HDPE) surfaces were investigated...

Acinetobacter baumannii (AB) has become multidrug-resistant (MDR) in recent years and currently there are limited effective treatment options. Nutrient metals (e.g. iron) are essential to the metabolic functions of AB. This study examined the impact of iron chelation on the growth of AB in vitro and in vivo. Susceptible and MDR AB bloodstream isolates (n = 9) were recovered from unique patients between 2011 and 2018. Clonal diversity was ascertained by Fourier Transform Infrared Spectroscopy. In vitro bacterial densities were measured over 20 hours to determine growth profiles...

To investigate the characteristics of different LAB strains isolated from subtropics and their effects on Napier grass (Pennisetum purpureum Schum.) silage with two dry matter levels, sugar fermentation pattern and growth profiles of three screened lactic acid bacteria (LAB) strains [Pediococcus pentosaceus (PP04), Weissella cibaria (WC10), and Lactobacillus plantarum (LP694)] were characterized, and then used either individually or in combination at 1.0 × 106 cfu·g-1 fresh weight to inoculate grass having 15% or 25% dry matter (DM)...