| Abstract | Rod Francisella pripada porodici Francisellaceae, patogenim Gram negativnim bakterijama. Taksonomski se dijeli u pet vrsta, a najvirulentnija i najviše proučena vrsta Francisella tularensis uzročnik je bolesti tularemije kod ljudi i životinja. Put prijenosa uključuje posredstvo vektora od kojih je najčešći krpelj, a infekcije su zabilježene i u izravnom kontaktu s zaraženom životinjom ili inhalacijom inficiranog aerosola. F. tularensis je ovisno o soju široko rasprostranjena u Sjevernoj Americi, ali i u Europi i Aziji. Može se podijeliti u tri soja koja uključuju F. tularensis subsp. tularensis, F. tularensis subsp. holartica i F. tularensis subsp. mediasiatica. Zbog vrlo niske infektivne doze i lakog prenošenja zračnim putem F. tularensis se smatra potencijalnim biološkim oružjem te je iz tog razloga u znatnijoj mjeri istražena. Iako se donedavno smatrala sojem F. tularensis, danas Francisella novicida čini zasebnu vrstu. F. novicida je zbog svoje avirulentnosti kod ljudi, povoljna za proučavanje eksperimentalne tularemije pri čemu ne zahtjeva rad u laboratorijima visoke zaštitne razine. Izolirana pretežito iz slanih i boćatih voda, uspješno obitava u vakuolama unutar stanica ameba koje joj omogućuju preživljavanje u vodenom okolišu. Posjeduje i sposobnost inficiranja makrofaga u koje ulazi fagocitozom i razmnožava se unutar fagosoma. Prilikom razmnožavanja F. novicida, dolazi do staničnih promjena koje rezultiraju lizom i u konačnici apoptozom stanica. Naglasak ovog završnog rada stavljen je na istraživanje citopatskog učinka kojeg uzrokuje F. novicida kod stanica Acanthamoeba castellani i imortaliziranih mišjih makrofaga. Praćena je kinetika rasta bakterije na BCYE agaru kao i količina ispuštenih staničnih proteina, DNK i enzima laktat dehidrogenaze u supernatantu, u vremenskim odmacima od 24, 48 i 72 sata nakon inficiranja. Rezultati pokazuju da se F. novicida bolje razmnožava i raste unutar ameba te da se tijekom porasta broja unutarstaničnih bakterija, statistički značajno više povećava i količina ispuštenih staničnih proteina, DNK i LDH, no što ih se otpusti spontano tijekom životnog ciklusa stanice. U konačnici može se zaključiti da su A. castellanii i imortalizirani mišji makrofagi dobar model za proučavanje unutarstaničnog načina preživljavanja i patogeneze F. novicida i ostalih vrsta roda Francisella. |
| Abstract (english) | The genus Francisella belongs to the family Francisellaceae, pathogenic Gram-negative bacteria. It is taxonomically divided into five species, and the most virulent and most studied species, Francisella tularensis, is the causative agent of tularemia in humans and animals. The route of transmission involves the mediation of vectors, of which the most common are ticks. Infections have also been reported in direct contact with an infected animal or by inhalation of an infected aerosol. F. tularensis, depending on the strain, is widespread in North America, but also in Europe and Asia. It can be divided into three strains involving F. tularensis subsp. tularensis, F. tularensis subsp. holartica and F. tularensis subsp. mediasiatica. Due to it's very low infectious dose and easy airborne transmission, F. tularensis is considered as a potential biological weapon and has therefore been extensively researched. Although, recently considered a strain of F.tularensis, today Francisella novicida forms a separate species. F. novicida is due to its avirulence in humans, favorable for the study of experimental tularemia without requiring work in laboratories of high protective level. Isolated predominantly from salt and brackish waters, it successfully inhabits vacuoles within amoeba cells that allow it to survive in the water ecosystems. It also has the ability to infect macrophages, which enters by phagocytosis and multiplies within the phagosome. During the multiplication of F. novicida, cellular changes result in lysis and ultimately apoptosis. The aim of this work was to investigate the cytopathic effect caused by F. novicida in Acanthamoeba castellani cells and Immortalized bone marrow macrophages. The kinetics of bacterial growth on BCYE agar as well as the amount of released cellular proteins, DNA and enzyme lactate dehydrogenase in the supernatant were monitored, at intervals of 24, 48 and 72 hours post infection. The results show that F. novicida reproduces and grows better within amoebae. As the number of intracellular bacteria increases, the amount of released cellular proteins, DNA and LDH increases statistically significantly more than they are released spontaneously during the cell life cycle. Ultimately, it can be concluded that A. castellanii and Immortalized bone marrow macrophages are a good model for studying the intracellular mode of survival and pathogenesis of F. novicida and other species of the genus Francisella. |
