| Abstract | Iako se dosad rezistenciji spolno-prenosive bakterije Chlamydia trachomatis nije pridavala
velika pažnja zbog dobrog kliničkog odgovora na standardnu antibiotsku terapiju, neuspjesi
liječenja povezani s laboratorijski dokazanom rezistencijom opisani su u literaturi. Hrvatska
je zemlja s visokom stopom propisivanja antimikrobnih lijekova što može utjecati na pojavu
rezistentnih ili slabije osjetljivih klamidijskih izolata. Zbog zahtjevne metodologije dosad u
našoj zemlji nije provedeno testiranje njihove antimikrobne osjetljivosti.
Cilj ovog istraživanja bio je utvrditi učinkovitost azitromicina, doksiciklina i levofloksacina
in vitro za 40 urogenitalnih klamidijskih izolata iz hrvatskih pacijenata izoliranih u razdoblju
od tri godine. 23 izolata iz obrisaka vrata maternice, 16 izolata iz obrisaka muške uretre, 1
izolat iz eksprimata prostate te 2 referentna soja podvrgnuta su testiranju antimikrobne
osjetljivosti na McCoy stanicama. Za svaki izolat određena je minimalna inhibitorna
koncentracija (MIC) kao najmanja koncentracija antibiotika bez mikroskopski vidljivih
inkluzija, te minimalna klamicidna koncentracija (MCC) kao ona koncentracija antibiotika
kod koje nije bilo vidljivih inkluzija nakon pasaže soja na staničnu kulturu bez antibiotika.
Svi ispitivani sojevi bili su osjetljivi na azitromicin, doksiciklin i levofloksacin u uvjetima in
vitro (MIC < 4 μg/ml), a obrazac „homotipne“ ili „heterotipne rezistencije“ nije pronađen
kod niti jednog testiranog izolata. Vrijednosti MCC-ova bile su jednake vrijednostima MICova,
ili su bile više u rasponu od jednog do pet razrijeđenja. Za sve izolate raspon MIC-a
azitromicina iznosio je 0,064 – 0,125 μg/ml, doksiciklina 0,016 – 0,125 μg/ml, a
levofloksacina 0,125 – 1,0 μg/ml; raspon MCC-a azitromicina iznosio je 0,064 – 2,0 μg/ml,
doksiciklina 0,032 – 1,0 μg/ml, a levofloksacina 0,125 – 2,0 μg/ml. Koncentracije testiranih
referentnih sojeva (serovar E Bour i serovar F ICCal) bile su podudarne s medijanima ili za
jedno razrjeđenje više od medijana urogenitalnih klamidijskih izolata iz hrvatskih pacijenata.
Uspoređivanjem vrijednosti MIC-ova i MCC-ova antimikrobnih lijekova pronađene su
statistički značajne razlike u njihovoj učinkovitosti in vitro. Najjači antimikrobni učinak na
testirane sojeve pokazao je doksiciklin, slijedi ga azitromicin, dok je najslabiju aktivnost
iskazao levofloksacin. Rezultati dobiveni in vitro podudaraju se s rezultatima kliničkih
istraživanja u Hrvatskoj i svijetu, premda nedostaju studije koje bi direktno usporedile
učinkovitost levofloksacina s učinkovitošću azitromicina i doksiciklina u terapiji
klamidijskih infekcija in vivo. Statistički značajna korelacija pronađena je u slučaju dva
antimikrobna para za MCC-ove: azitromicina i levofloksacina, te doksiciklina i
levofloksacina. U oba slučaja sojevi kojima je potrebna veća koncentracija azitromicina ili
doksiciklina za postizanje klamicidnog efekta trebaju i veću koncentraciju levofloksacina.
Usporedba medijana za različite kliničke uzorke nije ukazala na statistički značajnu razliku.
Premda rezistentni sojevi nisu pronađeni, određeni izolati pokazuju značajno više
koncentracijske vrijednosti. Tako je vrijednost MCC-a azitromicina iznosila 1 μg/ml ili bila
veća kod 29,4% izolata iz obrisaka muške uretre i eksprimata prostate, tj. kod 15% svih
testiranih izolata, što je relevantno u usporedbi s dostupnom literaturom. Kako još uvijek nije
jasno može li C. trachomatis razviti rezistenciju in vivo uslijed selekcijskog pritiska
antimikrobnog liječenja, nužno je nastaviti s ovakvom vrstom istraživanja – poglavito u
zemljama s velikom potrošnjom antibiotika. |
| Abstract (english) | Although the resistance of sexually transmitted bacterium Chlamydia trachomatis was not of
great concern due to its excellent sensitivity to standard antibiotic therapy, treatment failures
associated with laboratory-confirmed resistance have been described in the literature. Croatia
is a country with a high rate of antimicrobial drug prescriptions which can give rise to
resistant or less sensitive chlamydial strains. Due to the laborious methodology, chlamydial
isolates so far have not been subjected to antimicrobial susceptibility testing in our country.
The aim of this study was to evaluate in vitro efficacy of azithromycin, doxycycline and
levofloxacin for 40 urogenital chlamydial strains isolated from Croatian patients over a
period of three years. 23 isolates from cervical swabs, 16 isolates from male urethral swabs,
1 isolate from expressed prostatic secretions and 2 reference strains were subjected to
antimicrobial susceptibility testing on McCoy cells. Minimal inhibitory concentration (MIC)
as the lowest concentration of antibiotic without microscopically visible inclusions and
minimal chlamydicidal concentration (MCC) as the concentration without visible inclusions
after one passage in antibiotic-free cell culture have been determined for each strain.
All strains were susceptible to azithromycin, doxycycline and levofloxacin in vitro (MIC < 4
μg/ml), hence “homotypic” or “heterotypic” resistance pattern has not been found in any of
the tested isolates. MCC values were equal to MIC values, or were one to five dilutions
higher. For all strains together MIC ranged from 0.064 to 0.125 μg/ml for azithromycin,
from 0.016 to 0.125 μg/ml for doxycycline, and from 0.125 to 1.0 μg/ml for levofloxacin;
MCC ranged from 0.064 to 2.0 μg/ml for azithromycin, from 0.032 to 1.0 μg/ml for
doxycycline, and from 0.125 to 2.0 μg/ml for levofloxacin. Concentrations of tested
reference strains (serovar E Bour and serovar F ICCal) were in concordance with medians of
urogenital chlamydial strains from Croatian patients, or were one dilution higher.
Comparison of MIC and MCC values of antimicrobial drugs revealed statistically significant
difference in their in vitro efficacy. The strongest antimicrobial effect was shown by
doxycycline, followed by azithromycin, whilst levofloxacin was the least effective. Our in
vitro results are in accordance with the results of clinical research in our country and abroad,
although we lack studies that directly compare the efficacy of levofloxacin with the
effectiveness of azithromycin and doxycycline in the treatment of chlamydial infections in
vivo. Statistically significant correlation was found for MCC in the case of two pairs of
antimicrobials: azithromycin and levofloxacin, and doxycycline and levofloxacin. In both of
those cases strains that require higher concentrations of azithromycin or doxycycline for
chlamydicidal effect also necessitate a higher concentration of levofloxacin. Comparison of
medians for different clinical samples did not show any statistically significant difference.
Although resistant strains have not been found, certain isolates exhibited a significantly
higher concentration values. The value of MCC for azithromycin was 1 μg/ml or higher in
29.4% of isolates from male urethral swabs and expressed prostatic secretions, i.e. in 15% of
all the tested isolates, which is relevant when compared to the available literature. Since we
still lack information on whether C. trachomatis is evolving in vivo in response to selection
pressure of antimicrobial treatment, it is essential to continue with this kind of resistance
surveillance – particularly in countries with high antibiotic consumption. |
