| Abstract | Infekcije urinarnog trakta (URI) koje uzrokuju Escherichia coli (E. coli) postaju sve veći problem diljem svijeta. Cilj rada je istražiti da li postoji učinkovit način da se infekcije brže izliječe sa terapijom kombinacije antibiotika. Da bi mogli napraviti istraživanje učinka kombinacije antibiotika bilo je potrebno odrediti minimalnu inhibicijsku koncentraciju (MIK) za antibiotike ciprofloksacin, rifampicin i streptomicin. Svaki od njih ima različit mehanizam djelovanja. MIK za ciprofloksacin iznosi 12,5
μg/ml, rifampicin 100 μg/ml i streptomicin 25 μg/ml. MIK vrijednosti antibiotika koje smo odredili eksperimentalno slažu se sa literaturnim vrijednostima. Kombinacije antibiotika koje smo koristili u ovom radu sastavljene su od koncentracija MIK pojedinačnih antibiotika. Istražili smo djelovanje još jednog važnog čimbenika, hranjivog medija u kojem se nalaze. Koristila su se dva medija, Luria – Bertani koji je bogat hranjivim tvarima i minimalni M9 medij koji je siromašan hranjivim tvarima. Usporedbom krivulja rasta u prisutnosti kombinacije antibiotika uočili smo da bakterije prestanu rasti nakon 1 h inkubacije sa svim testiranim kombinacijama te vidimo sličan broj bakterija tijekom 24 h uzorkovanja u LB mediju dok u M9 mediju primjećujemo blagi rast stanica tijekom inkubacije. Usporedba krivulja smrtnosti pojedinačnih antibiotika i njihovih kombinacija u LB mediju pokazala je brži i značajno veći pad broja bakterijskih stanica kod kombinacije antibiotika unutar 24 h. Slično djelovanje u oba medija ima kombinacija rifampicin – streptomicin, dok ostale kombinacije pokazuju sporiji baktericidni učinak. Usporedbom svih MIK koncentracija antibiotika u LB mediju, vidimo da imaju slično djelovanje no za sve testirane koncentracije primjećujemo da rifampicin ima najveću učinkovitost. Metodom antibiograma se pokazalo da kombinacija ciprofloksacin - streptomicin ima najučinkovitije djelovanje u LB i M9 mediju te je pokazala najveći porast učinka u usporedbi s pojedinačnim antibioticima od čak 20 puta. Usporedba sa antibiogramom je pokazala da većina koncentracija pojedinačnih antibiotika ciprofloksacina i streptomicina su pokazale jače djelovanje u LB mediju dok je kombinacija ciprofloksacin – streptomicin pokazala puno bolju učinkovitost u M9 mediju. Rezultate koje smo dobili eksperimentalnim radom bi se mogli iskoristiti kao temelj za buduća istraživanja rezistencije. |
| Abstract (english) | Escherichia coli (E. coli) urinary tract infections (UTIs) are becoming an increasing problem all over the world. The aim of this thesis was to find out whether there is an effective way to cure these infections faster with therapy combining different antibiotics. To be able to make a research about effects of antibiotic combinations, it was necessary to determine the minimum inhibitory concentration (MIC) for antibiotics: ciprofloxacin, rifampicin and streptomycin. Each of them has a different mechanism of action. Ciprofloxacin MIC is 12.5 μg/ml, rifampicin 100 μg/ml and streptomycin 25 μg/ml. The antibiotic MIC values that have been determined experimentally agree with the literary values. The antibiotic combinations used in this thesis were composed of the MIC concentrations of each individual antibiotic. Besides the research of the effect of antibiotics combination, the nutrient media they are part of has also been researched. Two different media were used: Luria - Bertani, media rich in nutrients, and a minimal M9 medium that is poor in nutrients. By comparing growth curves in the presence of antibiotic combination, it was observed that bacteria ceased to grow after 1 h incubation with all tested combinations. Also, a similar number of bacteria for 24 h of LB media sampling was noticed, while in M9 media slight growth of cells during incubation was observed. Furthermore, by comparison of kill curves of individual antibiotics and their combinations in LB medium, a faster and significantly higher bacterial cell count decrease in antibiotic combination within 24 h was observed. Similar action in both media was detected with combination rifampicin - streptomycin, while the other combinations showed a slower bactericidal effect. By comparison of all MIC antibiotic concentrations in LB media, it was seen that they have similar activity, but for all tested concentrations rifampicin demonstrated the highest efficacy. The antibiogram method showed that the ciprofloxacin - streptomycin combination had the major effect on LB and M9 media, and showed the highest effect compared to single antibiotics; up to 20 times. Comparison of antibiograms revealed that individual antibiotics ciprofloxacin and streptomycin, regardless their concentrations, had higher activity in the LB medium, while their combination showed better efficacy in the M9 medium. These results obtained by experimental work demonstrated efficacy of combined antibiotics therapy and therefore, set a basis for future research of bacterial resistance. |
