DEPARTMENT OF PATHOGENIC BACTERIA
Hristo Najdenski, PhD, Associate Professor
Head of Department
Tel: (+359 2) 979 31 61
E-mail: usema@bas.bg
1958
1982
1987
1988
1992-93
1996
2000
2002
2005
STAFF
Born October 24, Velingrad
MVD, Faculty Veterinary Medicine, Thracian University, Stara Zagora
PhD in Micribiology, Institute of Microbiology, BAS
Research Scientist, Institute of Microbiology, BAS
Visiting Scientist, Institut Pasteur, Paris, France
Associate Professor, Institute of Microbiology, BAS
Head of the Department Pathogenic Bacteria and Deputy Director of the Institute of
Microbiology
Visiting Scientist, Department of Medical Biochemistry, Turko University, Finland
Visiting Scientist, Institute for Agricultural and Fisheries Research, Technology and
Food Unit, Melle, Belgium
Anna Vesselinova, DSc., Professor MStoy@abv.bg
Tatyana Radoucheva, PhD, Associate Professor tradoucheva@abv.bg
Nadya Markova, PhD, Associate Professor nadya.markova@gmail.com
Vesselin Kussovski, PhD, Associate Professor vkussovski@yahoo.com
Neli Slavova-Azmanova, MD,PhD, Research Scientist nellystz@yahoo.com
Elica Golkocheva-Markova, PhD, Research Scientist golkocheva@microbio.bas.bg
Mariana Ninova, MS, Research Scientist
Neli Georgieva, DVM, Research Assistant
Iva Tzvetkova, MS, Research Assistant likovska@abv.bg
Anton Caro, DVM, Research Assistant anton_caro@abv.bg
Albena Cherneva, Laboratory Assistant
Radka Georgieva, Laboratory Assistant
PHD-STUDENTS
Mihail Iliev, MS Iliev@microbio.bas.bg
Violeta Valcheva, MS vivi088@abv.bg
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 multidrugresistant 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. B 50,
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. Pharmazie 60, 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. Pharmazie 60, 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
Immunopharmacology 5, 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 tuberculosis patients. The International
Journal of Tuberculosis and Lung Disease 9, 907-14.
Bonovska, M., Tzvetkov, Y., Najdenski, H., Bachvarova, Y. (2005): PCR for detection of
Mycobacterium tuberculosis in experimentally infected dogs. 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): Rapid
Detection of the Mycobacterium tuberculosis Beijing genotype and its ancient and modern
sublineages by IS6110-based inverse PCR. 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.