| Abstract | Cilj ovog rada bio je odrediti zastupljenost enterobakterija u rizosferi ekološki
uzgojene zelene salate (Lactuca sativa L.) te istražiti osjetljivost sojeva reda Enterobacteriales
prema klinički značajnim antibioticima. Ukupno je sakupljeno 18 uzoraka rizosfernog tla tri
sorti zelene salate (kristalka, puterica i hrastov list) s područja Varaždinske (OPG1) i Istarske
županije (OPG2). Prosječne vrijednosti ukupnog broja mikroorganizama iznosile su 6,92 ±
0,12 log CFU/g za OPG1 te 7,09 ± 0,16 log CFU/g za OPG2, dok je ukupni broj
enterobakterija bio 5,68 ± 0,26 log CFU/g za OPG1, te 5,23 ± 0,42 log CFU/g za OPG2. S
obzirom da su statistički značajne razlike zamijećene samo u ukupnom broju
mikroorganizama i enterobakterija između različitih gospodarstava, ali ne i između sorata,
MALDI-TOF masenim spektrometrom identificirani su samo izolati izolirani iz rizosfernog
tla sorte kristalke (n=120). Ukupno je identificirano šest rodova i 24 različite vrste bakterija,
među kojima su tri roda i 12 vrsta pripadali redu Enterobacteriales, a po zastupljenosti se
isticala vrsta Enterobacter ludwigi (41,2%). Svi izolati enterobakterija (n=85) genotipizirani
su rep-PCR metodom te je selektirano njih 68 kojima je određena antibiotička rezistencija na
10 klasa antibiotika disk difuzijskom metodom. Među ispitivanim sojevima, jedan soj
pokazao je ekstrinzično uvjetovanu rezistenciju na dvije klase antibiotika (1,5%), dva soja
bila su rezistentna na jednu klasu (2,9%), jedan soj bio je rezistentan na jednu klasu
antibiotika (1,5%), a umjereno osjetljiv na drugu, dok su tri soja bila umjereno osjetljiva na
jednu klasu antibiotika (4,4%). Kod ostalih sojeva (n=55) rezistentnost ili umjerena
osjetljivost bila je intrinzično uvjetovana za ispitivane klase antibiotika, dok je šest sojeva bilo
osjetljivo na sve ispitivane antibiotike. Rezultati ovog rada pokazuju da enterobakterije čine
značajan udio ukupne mikrobiote rizosfere zelene salate (1,3 do 8,8%), ali da ni jedan soj ne
pripada skupini multirezistentnih bakterija. |
| Abstract (english) | The aim of this study was to determine the presence of enterobacteria in the
rhizosphere of organically grown lettuce (Lactuca sativa L.) and to investigate the sensitivity
of Enterobacteriales strains to clinically relevant antibiotics. A total of 18 rhizosphere soil
samples of three varieties of lettuce (Iceberg, Butterhead and Oak leaf) were collected from
Varaždin (OPG1) and Istria (OPG2) Counties. The average values of the total number of
microorganisms were 6,92 ± 0,12 log CFU/g for OPG1 te 7,09 ± 0,16 log CFU/g for OPG2,
while the total number of enterobacteria was 5,68 ± 0,26 log CFU/g for OPG1 and 5,23 ± 0,42
log CFU/g for OPG2. Although statistically significant differences were observed only in the
total number of microorganisms and enterobacteria between the two farms, but not between
cultivars, only isolates isolated from the rhizosphere soil of the Iceberg variety were identified
by MALDI-TOF (n=120). In total, six genera and 24 different types of bacteria were
identified, among which three genera and 12 species belonged to the order Enterobacteriales
and species Enterobacter ludwigi was the most abundant (41,2%). All isolates of
enterobacteria (n=85) were genotyped using the rep-PCR method, and 68 of them were
selected for which antibiotic resistance to 10 different classes of antibiotics was determined
using the disk diffusion method. Among the tested isolates, one showed extrinsically
conditioned resistance to two classes of antibiotics (1.5%), two isolates were resistant to one
class of antibiotics (2.9%), one isolate was resistant to one class of antibiotics (1.5%) and
moderately sensitive to another, while three isolates were moderately sensitive to one class of
antibiotics (4.4%). In the other strains (n=55), resistance or moderate sensitivity was
intrinsically determined for the tested classes of antibiotics, while six strains were sensitive to
all tested antibiotics. The results of this work show that enterobacteria make up a significant
proportion of the total microbiota of the lettuce rhizosphere (1.3 to 8.8%), but that not a single
strain belongs to the group of multiresistant bacteria. |
