DEPARTMENT OF PATHOGENIC BACTERIA

Hristo Najdenski, PhD, Associate Professor

Head of Department

Tel: (+359 2) 979 31 61

E-mail:

1958 / Born October 24, Velingrad
1982 / MVD, Faculty Veterinary Medicine, Thracian University, Stara Zagora
1987 / PhD in Micribiology, Institute of Microbiology, BAS
1988 / Research Scientist, Institute of Microbiology, BAS
1992-93 / Visiting Scientist, Institut Pasteur, Paris, France
1996 / Associate Professor, Institute of Microbiology, BAS
2000 / Head of the Department Pathogenic Bacteria and Deputy Director of the Institute of Microbiology
2002 / Visiting Scientist, Department of Medical Biochemistry, Turko University, Finland
2005 / Visiting Scientist, Institute for Agricultural and Fisheries Research, Technology and Food Unit, Melle, Belgium

Staff

Anna Vesselinova, DSc.,

Tatyana Radoucheva, PhD, Associate Professor

Nadya Markova, PhD, Associate Professor

Vesselin Kussovski, PhD, Associate

Neli Slavova-Azmanova, MD,PhD, Research

Elica Golkocheva-Markova, PhD, Research Scientist

Mariana Ninova, MS, Research Scientist

Neli Georgieva, DVM, Research Assistant

Iva Tzvetkova, MS, Research

Anton Caro, DVM, Research Assistant

Albena Cherneva, Laboratory Assistant

Radka Georgieva, Laboratory Assistant

PhD-students

Mihail Iliev, MS

Violeta Valcheva,

Main Research Topics:

  • Factors and mechanisms of bacterial virulence
  • Bacterial-host interactions in zoonoses and particularly dangerous infections
  • Surface bacterial structures and bioenergetic mechanisms
  • Sunlight and the survival of Enterobacteriaceae bacteria in water ecosystems
  • Influence of environmental factors on the survivability of pathogenic yersiniae - epidemiology and prevention.
  • Detection and enumeration of pathogens in products of animal origin by using the polymerase chain reaction.
  • In vitro determination of antibacterial and antifungal activity of substances with organic and non-organic origin.
  • Photophysical and photosensitizing properties of phthalocyanine complexes as antibacterial and antiviral agents
  • Molecular characterisation of Mycobacterium tuberculosis strains and Monitoring the burden and transmission of tuberculosis in Bulgaria; Incidence of multidrug-resistant TB (MDR-TB); Genotypic detection of drug resistant mutations

Most Important Achievements:

  • The increased growth ability and virulence of septicaemic pathogens in animal corps was found, and the relationship of this phenomenon to the changes in energetic metabolism of the bacteria was proved.
  • Pathogenic strains of the species Yersinia enterocolitica have been isolated from children with gastrointestinal disorders, from tonsils of pigs, as well as from the viscera of wild animals (boars, wild cats, deers, birds, and fishes). Microorganisms of the species Yersinia pseudotuberculosis (serotypes 0:1, 0:2, 0:3, and 0:5) have been isolated from the viscera of boars, wild cats and birds.
  • Yersinia outer membrane proteins have been isolated and used in improved ELISA and immunoblot tests for routine laboratory diagnosis of natural yersiniosis in humans and pigs and experimental yersiniosis of rabbits.
  • Bacterial-host interactions (invasion, persistence, intracellular survival, as well as the bioenergetic mechanisms ensuring these processes) were characterized. Pathogenesis of experimental melioidosis, listeriosis, yersiniosis, salmonelosis, etc. and immune response of different hosts were established in details.
  • Clinical, immunological, and pathomorphological examinations were followed after experimental oral infections of rabbits with two wild and four genetically constructed mutant strains of Y. enterocolitica 0:8. A lower virulence and bacterial load of the viscera, weaker morphological changes, better immunogenicity and well expressed tissue tropism to the lymphoid tissue of the mutant strains DwzzGB and sodA-314 in comparison with mutants 8081-R2, DwbcEGB and wild strains WA-314 and 8081-L2 were established.
  • The photoinhibitory effect could be used in the practice for photosterilization of contaminated with enterobacteria water ecosystems;
  • The role of Yersinia antigens (LPS) in induction of reactive arthritis was proved in experimental models.
  • The role of outer membrane proteins YopK and YpkA during experimental oral pig model with Yersinia pseudotuberculosis was studied. It was established that these mutant strains are less virulent in comparison with wild type strain. Nevertheless the strains were characterized with high immunogenic potential and ability to colonize the lymphoid tissues. This ability was the highest in yopK mutant strain.
  • The first time in our country was studied the incidence and transmission of multidrug-resistant Mycobacterium tuberculosis strains using advanced molecular epidemiological methods and population structure analysis. The multidrug resistant and hypervirulent Beijin strain was not found in Bulgaria. The results contribute to control the global spread of multidrug TB worldwide.
  • It was found that the methicilin-resistant and methicilin-sensitive strains of Staphylococcus aureus as well as Pseudomonas aeruginosa and Candida albicans can be effectively photoinactivated with the cationic phthalocyanine ZnPeMe. Anionic phtalocyanine ZnPcS and cationic phthalocyanine ZnPeMe are effective virucidal photosensitisers for the studied DNA-viruses – Herpes virus simplex type I and Vaccinia virus.
  • The method of PCR-DGGE was optimized and successfully applied for direct detection and typing of Campylobacter jejuni and Campylobacter coli in caecal samples of broilers without preliminary enrichment. This method allows reliable and fast detection and identification of pathogenic Campylobacters being causative agent №1 of food infections in humans.

Selected Publications:

Najdenski H., Vesselinova A. (2002): Experimental mixed infection of rabbits with Yersinia enterocolitica and Listeria monocytogenes. J. Vet. Med. B 49, 97-104.

Najdenski, H., Vesselinova, A., Golkocheva, E., Garbom, S., Wolf-Watz, H. (2003): Experimental infections with wild and mutant Yersinia pseudotuberculosis strains in rabbits. J. Vet. Med. B50, 280-288.

Najdenski, H., Golokocheva, E., Vesselinova, A., Bengoechea, J-A., Skurnik, M. (2003): Proper expression of the O-antigen of lipopolysaccharide is essential for the virulence of Yersinia enterocolitica O:8 in experimental oral infection of rabbits. FEMS Immunol. Med. Microbiol., 38, 97-106.

Bengoechea J.A., Najdenski H., Skurnik M. (2004): Essential role of the lipopolysaccharide O-antigen status of Yersinia enterocolitica O:8 in virulence and in the outer membrane regulatory network. Mol. Microbiol. 52, 451-469.

Najdenski H., Golkocheva E., Vesselinova A., Russmann H. (2004): Comparison of the course of infection of virulent Yersinia enterocolitica serotype O:8 with an isogenic soda mutant in the peroral rabbit model. Int. J. Med. Microbiol. 294, 383-393.

Ignatova M, Voccia S, Gilbert B, Markova N, Mercuri PS, Galleni M, Sciannamea V, Lenoir S, Cossement D, Gouttebaron R, Jerome R, Jerome C. (2004): Synthesis of copolymer brushes endowed with adhesion to stainless steel surfaces and antibacterial properties by controlled nitroxide-mediated radical polymerization. Langmuir. 20, 10718-26.

Markova, N., L. Michailova, V. Kussovski, M. Jourdanova, T. Radoucheva (2005):Intranasal application of Lentinan enhances bactericidal activity of rat alveolar macrophages against Mycobacterium tuberculosis. Pharmazie60, 42-48.

Markova N, Michailova L., Kussovski V, Jourdanova M, Radoucheva T. (2005): Intranasal application of lentinan enhances bactericidal activity of rat alveolar macrophages against Mycobacterium tuberculosis.Pharmazie60, 42-8.

Drandarska, I, Kussovski, V., Nikolaeva, S., Markova, N. (2005): Combined immunomodulating effects of BCG and Lentinan after intranasal application in guinea pigs. International Immunopharmacology5, 795-803.

Michailova, L, Kussovski, V., Radoucheva, T., Jourdanova, M., Berger, W., Rinder, H., Markova, N. (2005): Morphological variability and cell wall deficiency of Mycobacterium tuberculosis in “heteroresistant” strains isolated from newly diagnosed tuberculosispatients. The International Journal of Tuberculosis and Lung Disease9, 907-14.

Bonovska, M., Tzvetkov,Y., Najdenski,H., Bachvarova,Y. (2005): PCRfordetectionofMycobacteriumtuberculosisinexperimentallyinfecteddogs. J. Vet. Med.52(10), 5-8.

Najdenski, H., Golkocheva, E., Kussovski, V., Ivanova, E., Manov, V., Iliev M., Vesselinova, A., Bengoechea, J.A., Skurnik, M. (2006): Experimental pig yersiniosis to assess attenuation of Yersinia enterocolitica O:8 mutant strains. FEMS Immunol. Med. Microbiol.47, 425-435.

Mokrousov, I., Jiao,W.W., Valcheva, V., Vyazovaya, A., Otten, T., Ly, H. M., Lan, N. N., Limeschenko, E., Markova, N., Vyshnevskiy, B., Shen, A.D., Narvskaya O. (2006): RapidDetectionoftheMycobacteriumtuberculosisBeijinggenotypeanditsancientandmodernsublineagesbyIS6110-basedinversePCR. J. Clin. Microbiol.44, 2851–2856.

Mokrousov, I., Jiao, W.W., Sun,G.Z., Liu,J.W., Valcheva, V., Li, M., Narvskaya,O., Shen, A.D. (2006): Evolution of drug resistance in different sublineages of Mycobacterium tuberculosis Beijing genotype. Antimicrob. Agents and Chemotherapy 50, 2820-2823.

Golkocheva, E., Stoilov, R., Najdenski, H. (2006): Serological findings in blood sera of patients with Yersinia-triggered arthritis. Clin. Microbiol. Infect. 12 (s4), P1739.