Research summary



I, the undersigned Mariana Carmen (Balotescu) Chifiriuc, have started my research career in 1997, as a microbiologist in the the National Reference Center for Cholera and other vibrios (National Institute for Research and Development in Microbiology and Immunology “I. Cantacuzino” of Bucharest, Romania). I performed the diagnosis of Vibrionaceae strains, i.e. V. cholerae (serogroups O1 and non O1), halophilic vibrios and Aeromonas strains, as well as the epidemiological surveillance of V. cholerae strains circulating in Romania. I have brought a significant contribution to the implementation of new methods for the investigation of toxigenicity and virulence potential, as well as to the standardization of antimicrobial susceptibility testing of Vibrio isolates.

In 1999, I received a nine months fellowship from the International Network of Pasteur Institutes and Associates in the Opportunistic Infections Unit of the Pasteur Institute of Bangui, where I was involved in two projects, i.e. Blastocystis hominis, Entamoeba sp.: primary or opportunistic pathogens and Detection of Entamoeba histolytica/dispar complex using Entamoeba and Entamoeba histolytica II ELISA Techlab kits, followed by a three months fellowship at the Pasteur Institute of Paris. In 2005 I defended my PhD thesis entitled: Host-parasite relationship. Opportunistic infections in HIV-infected patients.

From 2001 to 2009, I was the National Data Manager for Romania in EARSS (European Antimicrobial Surveillance System) (EARSS Annual Reports 2002, 2008), contributing to the the implementation, maintenance and improvement of national antibiotic resistance (AR) surveillance programs, integrating our country in the global strategy established by the World Health Organization (WHO) for worldwide surveillance of drug resistance.

In 2003 I have started my teaching career at the University of Bucharest, Faculty of Biology, first as lecturer at the Department of Botany and Microbiology (2003-2007), then as associate professor (2007-2013) and since February 2013, as Full professor and PhD supervisor in the same department.

My teaching activity consists in courses of General microbiology, Immunobiology, Immunopathology, Medical microbiology, Microbiological control of water, food, air and pharmaceutical products and practical works of Immunobiology, Immunopathology and serology, General and applied microbiology, Virology (for undergraduated, Master, PhD and Postdoctoral students).

Since 2006, I am also invited for annual conferences and post-graduation training courses in the field of clinical bacteriology for specialists working in the sanitary system in Romania, being member of the OBBCSSR (Romanian Order of Biologists, Biochemist and Chemists working in the Sanitary System) ( Giving that Applied microbiology is emerging as one of the most popular career options among the students of our faculty, I was actively involved in drafting two new Master curricula, i.e. Applied microbiology and immunology and Quality management in clinical laboratories, introduced in 2013 and respectively in 2014, the last one being harmonyzed in accordance with the European Syllabus and with the European Council Directive 93/16/EEC of 5 April 1993 to facilitate the free movement of medical personnel and the mutual recognition of their diplomas, certificates and other evidence of formal qualifications.

As scientific advisor of CALILAB (Association for quality in laboratories) (, I am also involved in the design, checking and validation of the external quality control schemes for microbiology.

I am supervising around 20 undergraduated and Master students per academic year for the performance of their theses in the field of microbiology and immunology.

The main research focuses of my PhD students are: molecular characterization of virulence and resistance of opportunistic pathogens (Gram-negative bacilli, Candida albicans, chronic wounds and prostatitis associated biofilms), establishing correlations between spermatic infections and male infertility, investigation of novel antimicrobial strategies based on metallic nanoparticles.

At least 20 students were included in the research team of the coordinated projects, being first or co-authors of numerous papers indexed in international databases and sponsored to present their research results in a lot of national and international conferences.


After delivering my PhD, I have started to apply for funding independently, winning as project manager six national projects in different competitions, all of them approaching new research areas for our country (CEEX -Excellence Research-2006- Novel strategy for attenuation of bacterial pathogenicity and virulence based on QS inhibitors, CNCSIS –The National University Research Council -2007- The role of P. aeruginosa bacterial pheromones in the modulation of host-bacterial cell interaction during the infectious process, IDEAS 2007 – The role of heat shock proteins in bacterial pathogenesis and their potential use in developing new antimicrobial strategies, HUMAN RESOURCES 2010 – The correlation of Pseudomonas aeruginosa and Staphylococcus aureus virulence and/or resistance pattern with the clinical outcome of nosocomial infections, IDEAS 2011- Effects of P. aeruginosa quorum sensing  molecules on Drosophila genome: a new tool to identifycandidate genes involved in host-pathogen crosstalk; HUMAN RESOURCES 2014-Risk assessment of transposon-mediated transfer of some carbapenemase gene).

Main research directions approached in the research projects:

  • Investigation of the natural aquatic bacterial reservoir of virulence AR by phenotypic and genotypic tools

In strong contrast to clinical studies, there is little information available on the epidemiology of AR/virulence genes reservoirs in the environment, especially for geographically based data. The studies performed on Vibrionaceae family (aeromonads, nonhalophilic and halophilic vibrios) members have pointed out the significance of the Danubian and Black Sea aquatic environments as reservoirs of AR and virulence, and the ability of the investigated strains to survive and maintain their pathogenic potential in limiting conditions.

The study of AR and virulence profiles in bacterial strains isolated from wastewater treatment plants and receiving waters in Romania has shown that waste waters represent a source for bacterial strains resistant to different antibiotic classes (especially beta-lactams, tetracyclines and quinolones), that are released in the effluent and downstream river. These results have been included in the PhD thesis of dr. Florica Marinescu.

  • Investigation of AR features, virulence markers and their regulators in clinical strains isolated from different infections and from the hospital environment

In our studies, we tried to investigate different aspects of the complex relationships among bacterial infectious agents, the host and the inert (prosthetic devices) substratum. We have characterized the phenotypic and molecular virulence markers in Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli, Helicobacter pylori and anaerobic bacteria clinical strains. In case of S. aureus, a specific relationship between the type of clinical sample and the agr group was found. Thus, the agr I was prevalent among S. aureus strains isolated from blood cultures, whereas agr III prevailed among strains from respiratory secretions. The strains isolated from vaginal secretions belonged to agr II and agr III groups. We have demonstrated the implication of Bifidobacterium strains, otherwise considered as commensal bacteria with low virulence, probiotic and anticarcinogenic properties, in five severe clinical cases of infections associated with surgical abdominal emergencies.  At least six PhD theses have derived from these studies, defended by Otilia Banu, Magda Mitache, Madalina Ilie, Cristina Larion, Ilda Czobor, Irina Gheorghe.

We have demonstrated for the first time in the Romanian population that the CagA (cytotoxin associated gene antigen) positive H. pylori strains are more virulent and the anti- cagA IgG antibodies high titer is associated with persistence of infection after treatment, upper gastro duodenal ulcers or gastric cancer.

  • Investigation of host-pathogen crosstalk during the infectious process

In order to understand how the stress adaptation is influencing Vibrio parahaemolyticus pathogenicity and immnogenicity, we tried i) to establish the levels of heat shock proteins (HSPs) in different cellular fractions of V. parahaemolyticus in relation with a certain stress factor and ii) to investigate the in vitro cytokine response of different cell lines and the in vivo anti-HSPs response of holoxenic mice to different cellular fractions of V. parahaemolyticus grown under sub-lethal heat and osmotic shock. Our results revealed an increased GroEL and DnaK synthesis after heat or simultaneous heat and osmotic shock, correlated with the occurrence of a pro-inflammatory response associated with increased levels of IL-6 and TNF-α expression in different cellular cultures (HeLa and human diploid cells-HDC). An increased titer of anti-HSP antibodies correlated with protection against infection was observed in infected mice.

P. aeruginosa infections represent one of the major threats for injured or transplanted lungs and for their healing and one of our main research focuses is the study of host – P. aeruginosa quorum sensing signaling molecules (QSSMs) cross-talk. These studies were developed in two PhD theses performed with the support of our research projects, i.e. Carmen Curutiu and Alina Maria Holban. Considering that the mesenchymal stem cells (MSCs) are a major tool for the regenerative medicine, including therapy of lung damaging diseases, we investigated the effects of P. aeruginosa quorum sensing signaling molecules (QSSMs) on human MSCs death signaling pathways and cytokine profile. Our data revealed that N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL), N-butanoyl-L-homoserine lactone (C4-HSL), 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS), and its precursor, 2-heptyl-4-quinolone (HHQ), significantly impact on several core signaling mechanisms of MSCs in a specific and time-dependent manner. The significant influence of the purified bacterial autoinducers on the MSCs signaling pathways may suggest that the accumulation of these mediators could interfere with the normal function of these cells in the human body, and eventually, impair or abolish the success of the stem cells therapy during P. aeruginosa infections.

  • Assessment of the antimicrobial activity of novel antimicrobial compounds, including nanostructures and nanomaterials

We have optimized methods for the study of the antimicrobial and antibiofilm activity of different nanomaterials, oru expertise in this field being recognized my the majority of the research groups involved in the development of novel antimicrobial strategies or novel biomaterials.

Assessed parameters:

  1. qualitative screening of the antimicrobial properties of the tested compounds by an adapted disk diffusion method;
  2. quantitative assay of the antimicrobial activity performed by binary micro dilution method;
  3. study of the anti-biofilm activity of the tested compounds by i) the microtiter method, ii) a simple model using bacterial cells immobilised in an agar matrix which is similar to the natural biofilm polysaccharide matrix; iii) biofilm development on different material specimens distributed in liquid medium.
    • Finding, selecting and testing the efficiency of some alternative strategies for the treatment of severe infections caused by highly resistant bacteria, with biofilm forming potential

The results of the studies of the ability of lactic acid bacteria to exhibit antimicrobial activity by inhibiting or killing pathogenic bacteria have been published in two patents, one book chapter in a Biotechnology Treatise and >10 papers and constituted a starting point for the PhD thesis of my younger colleague, Lia-Mara Ditu. We have studied the beneficial effects of whole cultures of probiotic strains as well as of culture fractions, such as supernatants  and heat inactivated bacterial bodies. We have shown that probiotic fractions induced an increase of the growth inhibition zone diameters for aminoglycosides, β-lactams and quinolones.

The efficiency of essential oils or polyphenolic extracts obtained from different plants, and their synergistic effects with antibiotics was tested against human and plant pathogens and represented the focus of one PhD thesis defended by Marcela Popa.

  • Identification and testing of new QS interference strategies

We have demonstrated  the QS inhibitory activity of soluble micromolecules secreted by probiotic Lactobacillus strains (i.e. phenyl lactic acid) or by plants (i.e. usnic acid), revealed by the ability of sIC of PLA to decrease the adherence to the cellular and inert substrata, the expression of haemolysins, lecithinase and caseinase and to attenuate P. aeruginoasa pathogenicity in an experimental animal model infection. Our studies on natural QS inhibitors were the first in the country and have been included in the PhD thesis and postdoc of Dr. Ani Ioana Cotar, the postdoc of Crina Saviuc and the ongoing PhD thesis of Bianca Ciubuc and inspired many research groups from our university and from other universities of the country, such as Bucharest Politehnica University, which started to develop antimicrobial nanostructures including plant-derived compounds and extracts (PhD Alexandru Grumezescu).

By using real-time RT-qPCR we demonstrated for the first time the inhibitory activity of the Lactobacillus paracasei subsp. paracasei probiotic culture filtrate on P. aeruginosa quorum-sensing genes expression.


Research directions

Through the future projects and research directions, I intend to provide the financial and conceptual basis for top priority research giving to students and young researchers the opportunity for adequate training in order to obtain competitive results and to perform their dissertation theses.

2.3.1. Biological research on virulence, drug resistance and ecology of microbial pathogens isolated from significant clinical contexts, but also from the natural environment.

To enable containment of AR and develop novel strategies for limiting the dissemination of more virulent pathogens, each country should further support research of the ecological determinants and genetic mechanisms that underline the evolution of microbial pathogens and their interaction with animal and human hosts.

One of the most important problems contributing to poor outcomes and high costs of antimicrobial resistance is the adequate selection of the initial (empiric) antibiotic therapy before susceptibility test results become available. Speed is essential when one deals with bacterial infections. When severe or nosocomial infections are suspected, they are often treated empirically with broad-spectrum antibiotics. However, the increased use of broad-spectrum antibiotics is not restricted to hospitalized patients in intensive care units or patients seen in emergency rooms. If physicians could get the identity of the microorganism and its resistance profile from the microbiology laboratory at the same time with the biochemistry and hematology results, antibiotic prescription rates could go down dramatically. Also, when antibiotics are needed, more targeted and inexpensive antibiotics could be used. Moreover, the patients carrying resistant microorganisms could be rapidly isolated, preventing the spread of multidrug-resistant organisms within hospital settings and other institutions. Thus, the availability of a rapid method for the direct detection of resistant bacteria in the clinical sample, much earlier than the susceptibility testing results, would improve this first and foremost step.

One major aim of my future research is to develop a rapid method for the direct detection of resistant bacteria in the clinical specimens by using flow cytometry. We consider this approach to be innovative, because it relies on a completely different concept: testing for resistance instead of testing for susceptibility.

I will continue the research on nosocomial agents, started during the project Human Resources No. 135/2010 The correlation of P. aeruginosa and S. aureus virulence and/or resistance pattern with the clinical outcome of nosocomial infections (NI).

This is a “hot field” of high interest for the public health and absolutely needed in order to identify new milestones for the control and limitation of nosocomial infections. One of my research goals is to harmonize complex phenotypic and genotypic laboratory methods in order to establish some virulence and resistance profiles of nosocomial agents that could be used for clinical diagnosis, epidemiological investigations, or routine surveillance of NIs.

2.3.2. Development of new experimental models for studying the host-pathogen relationship.

In the Ideas research project no. 154/2011, Effects of P. aeruginosa quorum sensing  molecules on Drosophila genome: a new tool to identify candidate genes involved in host-pathogen crosstalk, we proposed an original, integrative in vivo approach for the investigation of the way in which quorum sensing signaling molecules (QSSMs) of P. aeruginosa modulate the genome of Drosophila melanogaster (the fruit fly), in order to identify the most sensitive eukaryotic genes targeted by the two QSSM and find their orthologous in the human genome. Microarray studies were performed worldwide on D. melanogaster infected with alive or heat-killed P. aeruginosa, but to our knowledge, none focused on QSSMs effects on the transcriptome of D. melanogaster. Since the concentration of the synthetic QS molecules is controllable, we will be able to simulate different scenarios of infections with various bacterial charges and to monitor accordingly the modulation of the transcription rate of GOIs (genes of interest). We expect that the synergic interaction among microbiologists and fruit fly geneticists will empower the advantages of P. aeruginosa and D. melanogaster models, leading to the overcoming of some severe difficulties faced when treating multiresistant bacterial infections.

2.3.3. Biomedical applications of nanotechnology

In my future research, I will continue to be interested in the applications of nanotechnology for improved delivery of drugs, especially antibiotics as well as for obtaining improved surfaces with anti-biofilm properties (catheter devices, wound dressings etc).

The family of natural polymers (chitosan, alginate, cellulose, pectin) have a lot of advantages pleading for the possibility of the in vivo use of these macromolecular systems for target drug delivery, with minor risks for the occurrence of side effects. As polysaccharides are resistant to the digestive action of gastrointestinal enzymes and remain intact in the physiological environment of stomach and small intestine (being degraded only when they reach the colon by the abundant microbiota), they could be used as oral drug delivery vehicles. In the future research, we will investigate the potential of natural polymers and/or nanosized materials to improve the antibiotics activity or to deliver new antimicrobial substances in active forms.

The scaffolds obtained from natural polymers could be used as macromolecular carriers for the small molecule antibiotics, to induce the endocytosis of the drug by the target cell via a specific receptor and, following this first step, subcellular distribution of the drug to sites where the microorganisms are localized. In this way, we will transcend the great disadvantage of many classes of antibiotics which are acting only on the extracellular pathogens.       We also continue to study the interaction of different types of nanoparticles with the planktonic and adherent bacterial, as well as with the eukariotic cells, in the purpose to select the most biocompatible ones.

The financial support for this studies representing top priority fields of the biomedical, public health and environment protection research will be assurred on short term by the ongoing projects awarded as project manager or in partnership. In the future, I will continue to apply in national and international  competitions and to develop international collaborations in order to access research fundings.

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