Saber Khelaifia

Aix-Marseille University | AMU · IHU – Méditerranée Infection Marseille France

Recent years have been marked by a paradigm shift in the study of the human microbiota, with a re-emergence of culture-dependent approaches. Numerous studies have been devoted to the human microbiota, while studies on the oral microbiota still remain limited. Indeed, various techniques described in the literature may enable an exhaustive study of t...

In recent years, metagenomics and then culturomics, which consists of the multiplication of media and culture conditions and the rapid identification of all bacterial colonies, have generated renewed interest in the human microbiota, and diseases associated with modifications in its composition in particular. The sample transport media included in...

Strain SN6T is a non-motile and non-spore-forming gram-negative bacterium which was isolated from the stool sample of an Amazonian patient. The optimum growth was observed at 37 °C, pH 7, and 0-5 g/l of NaCl. Based on the 16S rRNA gene sequence similarity, the strain SN6T exhibited 97.5% identity with Vitreoscilla stercoraria strain ATCC_15218 (L06...

To date, the axenic culture of Treponema pallidum remains a challenge in the field of microbiology despite countless attempts. Here, we conducted a comprehensive bibliographic analysis using several databases and search engines, namely Pubmed, Google scholar, Google, Web of Science and Scopus. Numerous unsuccessful empiric studies have been conduct...

Background Severe acute malnutrition (SAM) is a major public health problem affecting children under the age of five in many low- and middle-income countries, and its resolution would contribute towards achieving the several sustainable development goals. The etiology of SAM is pluri-factorial, including delayed maturation of the gut microbiota, su...

Candida auris is an emerging multidrug-resistant yeast causing nosocomial infections and associated with high mortality in immunocompromised patients. Rapid identification and characterisation are necessary for diagnosis and containing its spread. In this study, we present a selective culture medium for all C. auris clades. This medium is sensitive...

Candida auris is an emerging multidrug resistant yeast causing nosocomial infections and associated with high mortality in immunocompromised patients. Rapid identification and characterisation is necessary for its diagnosis and containing spread. In this study, we present a selective culture medium for all C. auris clades. This medium is sensitive...

Background Malassezia spp. antifungal susceptibility testing (AFST) capacities are limited by the lack of efficient and standardized AFST procedure, mainly because of the fastidious cultivation of these yeast. Objectives This study aimed to compare the FastFung broth (FFB) to modified Dixon broth (mDIXB) for the in vitro AFST of Malassezia spp. Fl...

The human gut microbiota has been explored by a wide range of culture-dependent and culture- independent methods, revealing that many microbes remain uncharacterized and uncultured. In this work, we aimed to confirm the hypothesis that some of the species present in the human gut microbiota remain uncultured not because of culture limitations, but...

We developed a novel culture medium, referred to FastFung medium as suitable for the culture of clinical fungi, including fastidious ones, for both research and diagnostic studies. It is based on Schædler agar supplemented with many essential components for the growth of fastidious fungi. It also contains selective antibacterial agents for the inhi...

The human gut microbiota has been explored by a wide range of culture-dependent and culture-independent methods, revealing that many microbes remain uncharacterized and uncultured. In this work, we aimed to confirm the hypothesis that some of the species present in the human gut microbiota remain uncultured not because of culture limitations, but b...

Malassezia is a lipid-dependent commensal yeast of the human skin. The different culture media and skin sampling methods used to grow these fastidious yeasts are a source of heterogeneity in culture-based epidemiological study results. This study aimed to compare the performances of three methods of skin sampling, and two culture media for the dete...

Background Treponema species as commensals of the human microbiome have a prevalence and function depending on the studied niche. In the oral cavity, treponemes are ubiquitous while they have been strictly linked to rural and ancestral populations in the gastro-intestinal tract and are undetected in urban populations. In this study, an in silico an...

Culturomics, a high throughput culture method with rapid identification of the colonies by Matrix Assisted Laser Desorption Ionization/Time Of Flight Mass Spectrometry (MALDI-TOF MS), has demonstrated its contribution to the exploration of the gut microbiota over the past 10 years. However, the cost, work time and workload, considerably limit its u...

β-lactam antibiotics have a well-known activity which disturbs the bacterial cell wall biosynthesis and may be cleaved by β-lactamases. However, these drugs are not active on archaea microorganisms, which are naturally resistant because of the lack of β-lactam target in their cell wall. Here, we describe that annotation of genes as β-lactamases in...

The last 5 years have seen a turning point in the study of the gut microbiota with a rebirth of culture-dependent approaches to study the gut microbiota. High-throughput methods have been developed to study bacterial diversity with culture conditions aimed at mimicking the gut environment by using rich media such as YCFA (yeast extract, casein hydr...

Malassezia is lipid-dependent commensal yeast of the human skin. The different culture media and skin sampling methods used to grow these fastidious yeasts are a source of heterogeneity in culture-based epidemiological study results. This study aimed to compare the performances of three methods of skin sampling, and two culture media for the detect...

Phages and cancer immunity Gut bacteria are involved in the education of T cell immune responses, and the intestinal ecosystem influences anticancer immunity. Fluckiger et al. report microbial antigens that might cross-react with antigens associated with tumor cells. They found that a type of intestinal bacteria called enterococci harbor a bacterio...

In this study, we compared three methods of skin sampling, namely sterile gauze, dry swab and TranswabTM with transport medium. Additionally, we compared the performances of the FastFung medium with the reference Dixon agar for the detection of Malassezia spp. by culture. We showed that sterile gauze is the best technique to recover Malassezia yeas...

Background The spectrum of infections caused by methanogens remains to be described. We searched for methanogens in the blood of febrile patients using specific tools. Methods Blood culture samples routinely collected in patients with fever were prospectively screened by specific PCR assays for methanogens. Positive samples were observed by autofl...

Strain Marseille-P2082, an anaerobic, non-motile, asporogenous, Gram-negative, coccoid bacterium was isolated from the faeces of a 33 year-old obese French woman before bariatric surgery. The isolate exhibits 98.65% 16S rRNA gene nucleotide sequence similarity with Negativicoccus succinicivorans strain ADV 07/08/06-B-1388T, its current closest phyl...

Over the past decade, metagenomics has become the preferred method for exploring complex microbiota such as human gut microbiota. However, several bias affecting the results of microbiota composition, such as those due to DNA extraction, have been reported. These bias have been confirmed with the development of culturomics technique. In the present...

Uncontrolled oxidative stress, reported in Salmonella and HIV infections, colorectal cancer or severe acute malnutrition, has been associated with anaerobic gut microbiome alteration, impaired butyrate production, mucosal immunity dysregulation and disruption of host-bacterial mutualism. However, the role of major antioxidant molecules in the human...

Using taxono-genomics method, we describe here a Gram negative bacterium named Prevotella rectalis sp. nov., strain Marseille-P4334T (= CSUR P4334) isolated from the rectum. Strain Marseille-P4334T has genome that measure 3.03 Mbp with 43.3 mol% G+C content.

Massilistercora timonensis gen. nov., sp. nov. strain Marseille-P3756T is a new species from Firmicutes phylum isolated from the human gut microbiota with a genome of 2,769,591 bp-long (51.2% G+C). The closest species based on 16S rRNA sequence was Merdimonas faecis strain BR31 with 95.2 % sequence similarity. Considering phenotypic features and co...

An increasing number of scientists are turning to the microbiota to understand and/or explain the origin of various human metabolic or inflammatory diseases. Oxygen-intolerant bacteria represent the major population of the human intestinal microbiota. Their isolation is often difficult or even fastidious. The number of studies showing their benefic...

Archaeal sequences have been detected in human colostrum and milk, but no studies have determined whether living archaea are present in either of these fluids. Methanogenic archaea are neglected since they are not detected by usual molecular and culture methods. By using improved DNA detection protocols and microbial culture techniques associated w...

Microbiology has been largely developed thanks to the discovery and optimization of culture media. The first liquid artificial culture medium was created by Louis Pasteur in 1860. Previously, bacterial growth on daily materials such as some foods had been observed. These observations highlighted the importance of the bacteria's natural environment...

The interest in studying gut microbiota has been rekindled with the advent of molecular techniques, in particular, metagenomics. Culturomics (high throughput microbial culture with identification of the colonies by Maldi-TOF) has demonstrated its complementarity with metagenomics for comprehensive study of the microbiota. The main metagenomic studi...

Neoactinobaculum massilliense gen. nov., strain Marseille-P6182T (= CSUR P6182) and Pseudopropionibacterium massiliense sp. nov., strain Marseille-P6184T (= CSUR P6184) are a new bacterial genus and new bacterial species belonging to the Actinobacteria phylum that have been isolated from the human oral microbiota.

Olsenella timonensis sp. nov., strain Marseille-P2300T (= CSUR P2300; =DSM102072), is a new bacterial species from the phylum Firmicutes in the family Atopobiaceae.This bacteria species was isolated from the human gut microbiota.

We present here a new passive filtration-based culture device combined to a rapid identification with a new electron microscope (Hitachi TM4000) used for the detection and culture of Treponema species from the human oral cavity. Of the 44 oral samples herein cultivated, 14 were found positive for Treponema using electron microscopy and were also cu...

Nonribosomal peptides are assemblages, including antibiotics, of canonical amino acids and other molecules. β-lactam antibiotics act on bacterial cell walls and can be cleaved by β-lactamases. β-lactamase activity in humans has been neglected, even though eighteen enzymes have already been annotated such in human genome. Their hydrolysis activities...

Massilicoli timonensis sp. nov., strain Marseille-P3755T (= CSUR P3755 = DSM 103513) is a new bacterial species from the phylum Firmicutes and the family Clostridiales which was isolated from the human gut microbiota.

β-lactams targeting the bacterial cell wall are not efficient on archaea. Using phylogenetic analysis and common ancestor sequences for bacterial β-lactamases, we found serendipitously class B and class C-like β-lactamase genes in most archaea genomes. The class B β-lactamase appears to be highly conserved in archaea and to has been transferred in...

Massilimicrobiota timonensis gen. nov., sp. nov. strain Marseille-P2264 is a new species from Firmicutes phylum isolated from the human gut. Its genome was 2,849,574 bp-long with a 31.8% G+C content. The closest species based on 16S rRNA sequence was Longibaculum muris with 95.6% sequence similarity. Considering phenotypic features, 16S rRNA sequen...

Background: Oxygen diffused from the human gut mucosa and shape the microbiota with a radial gradient of microbes according to their oxygen tolerance, while microbial and chemical oxygen consumption maintains the lumen in a deeply anaerobic state. Uncontrolled oxidative stress and hyperoxygenation have been reported as a pathogenic mechanism in Sal...

Oceanobacillus timonensis Marseille-P3532T (CSUR P3532, CCUG 70981) and Oceanobacillus senegalensis Marseille-P3587T (CSUR P3587, CCUG 70613), are the type strains of O. timonensis sp. nov. and O. senegalensis sp. nov., respectively. They are moderately halophilic, aerobic, motile and Gram-stain positive bacteria. The strains P3532T and P3587T were...

Bacteroides bouchesdurhonensis sp. nov., strain Marseille-P2653T (= CSUR; P2653=DSM103120) is a new bacterial species belonging to the Firmicutes phylum in the family Bacteroidaceae that was isolated from the human gut microbiota.

We report here the main characteristics of Coprococcus phoceensis strain Marseille-P3062 T (CSUR P3062). The 16S rDNA sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry spectrum analysis were used to identify and characterize this new anaerobic bacterial species, which was isolated from the left colon cleans...

Objectives: Methanogenic Archaea are considered as extremely oxygen-sensitive organisms, and their culture is fastidious, requiring specific equipment. We report here conditions allowing the cultivation of Methanobrevibacter smithii in an anaerobic chamber without the addition of hydrogen. Methods: We first enriched the stool sample in an anaero...

[This corrects the article DOI: 10.1016/j.nmni.2016.06.003.].

[This corrects the article DOI: 10.1016/j.nmni.2016.06.002.].

Abstract Enterococcus timonensis sp. nov., strain Marseille-P2817T is a Gram-positive coccus, facultative anaerobe, motile and non spore-forming which was isolated from the sputum of a healthy adult man in Marseilles. We present herein its phenotypic description together with a MALDI-TOF analysis and genome sequencing and comparison. Enterococcus t...

A strictly anaerobic, motile, non–spore-forming, Gram-negative, rod-shaped bacterium designated Marseille-P3110 T was isolated from the left colon cleansing of a 76-year-old Frenchwoman. Its 16S ribosomal RNA (rRNA) gene showed a 93.2% similarity level with the 16S rRNA of Dielma fastidiosa strain JC13, the closest species with a validly published...

A new bacterium, strain AT3 T , was isolated by microbial culturomics from a faecal sample from a Frenchman after bariatric surgery. The isolate exhibited 96.6% 16S ribosomal RNA gene nucleotide sequence similarity with Anaerotruncus colihominis strain WAL 14565 T = CCUG 45055 T = CIP 107754 T . Phenotypic and genomic characteristics showed that th...

In 2008, as part of a feasibility study for radioactive waste disposal in deep geological formations, the French National Radioactive Waste Management Agency (ANDRA) drilled several boreholes in the transposition zone in order to define the potential variations in the properties of the Callovo–Oxfordian claystone formation. This consisted of a rare...

Intensive efforts have been made to describe the human microbiome and its involvement in health and disease. Culturomics has been recently adapted to target formerly uncultured bacteria and other unclassified bacterial species. This approach enabled us to isolate in the current study a new bacterial species, Parabacteroides timonensis strain Marsei...

Background/objectives High salt intake has been linked to several diseases including obesity and an increased risk of death; however, fecal salinity and the ability of salt to alter the gut microbiota, which was recently identified as an instrumental factor for health and disease, remains poorly explored. Methods/subjects We analyzed the fecal sam...

A Gram-positive, moderately halophilic bacterium, referred to as strain Marseille-P3518T, was isolated from a stool sample with 2% NaCl concentration from a healthy 15-year-old male living in Dielmo, a village in Senegal. Cells are aerobic, rod-shaped and motile and display endospore formation. Strain Marseille-P3518T can grow in a medium with 0-20...

Using culturomics, a recently developed strategy based on diversified culture conditions for the isolation of previously uncultured bacteria, we isolated strain Marseille‐P3296T from a fecal sample of a healthy pygmy female. A multiphasic approach, taxono‐genomics, was used to describe the major characteristics of this anaerobic and gram‐positive b...

By applying the culturomics concept and using culture conditions containing a high salt concentration, we herein isolated the first known halophilic archaeon colonizing the human gut. Here we described its phenotypic and biochemical characterization as well as its genome annotation. Strain Arc-HrT (= CSUR P0974 = CECT 9307) was mesophile and grew o...

Clostridium niameyense sp. nov. strain MT5 is the type strain of C. niameyense sp. nov., a new species within the genus Clostridia. C. niameyense is a Gram-positive, anaerobic bacillus. The strain MT5 (= CSUR P1468 = DSMZ 100441), whose genome is described here, was isolated from a faecal sample collected from a patient with anorexia and marasmus l...

Anaerobes represent the dominating population in the human gut microbiota and play a key role in gut homeostasis. In addition, several anaerobes are now considered as probiotics and they remain essential to several processes in the field of biotechnology. With the implementation of MALDI-TOF MS in routine laboratories, anaerobes are no longer negle...

Bacillus salis strain ES3T (= CSUR P1478 = DSM 100598) is the type strain of B. salis sp. nov. It’s an aerobic, Gram-positive, moderately halophilic, motile and spore-forming bacterium. It was isolated from commercial table salt as part of a broad “culturomics” study aiming to maximize the culture conditions for the in-depth exploration of halophil...

Strain Marseille-P2645T was isolated in a colon sample from a Frenchwoman who underwent a colonoscopy. Bacterial cells were Gram negative, non–spore forming, mobile and strictly anaerobic. The genome of strain Marseille-P2645T is 3 950 441 bp long and contains 3374 protein-coding genes. The DNA G+C content is of 51.66 mol%. Strain Marseille-P2645T...

Strain SIT6T was isolated from the fecal flora of a severely malnourished child as part of a broad “culturomics” study aiming to maximize the culture conditions for the in-depth exploration of the human microbiota. An analysis of the 16S rRNA gene sequence showed that strain SIT6T shared 94.1% 16S rRNA gene sequence similarity with Bacillus thermoa...