COMPARATIVE URINARY BACTERICIDAL ACTIVITY OF ORAL ANTIBIOTICS AGAINST GRAM-POSITIVE PATHOGENS
Autori:
Branka Bedenić, Ana Budimir, Ana Gverić, Vanda Plečko, Jasmina Vraneš, Marina Bubonja-Šonje, Smilja Kalenić
Sažetak
U kliničkim bakteriološkim laboratorijima antibakterijska aktivnost plazme određuje se in vitro testiranjem, obično disk-difuzijskom metodom. Međutim treba uzeti u obzir da in vitro testiranje ne odražava uvijek djelotvornost antibiotika in vivo. U ovom istraživanju ispitana je baktericidna aktivnost uzoraka urina dobivenih nakon peroralne primjene pojedinačne doze oralnog antibiotika prema relevantnim gram-pozitivnim urinarnim patogenima. Linezolid je imao zadovoljavajuće baktericidne titrove tijekom cijelog razdoblja testiranja prema svim testiranim gram-pozitivnim kokima, dok su fluorokinoloni pokazivali visoku i perzistentnu baktericidnu aktivnost prema stafilokokima, a znatno slabiju aktivnost prema enterokokima. Prema rezultatima ex vivo pokusa, amoksicilin bi se mogao preporučiti kao lijek izbora jedino za infekcije koje uzrokuje Enterococcus faecalis. Amoksicilin u kombinaciji s klavulanskom kiselinom mogao bi se razmatrati kao terapijska opcija kod infekcija koje uzrokuju Staphylococcus saprophyticus i E. faecalis. Testirani stariji cefalosporini pokazali su se djelotvornima samo prema S. saprophyticus. Njihov je nedostatak kratko poluvrijeme eliminacije u urinu, što rezultira brzim sniženjem urinarnih baktericidnih titrova tijekom ispitivanog razdoblja. Nadalje, nemaju aktivnost prema enterokokima zbog njihove intrinzične rezistencije na cefalosporine.
Summary
In routine bacteriological laboratories the antibacterial activity of antibiotics is determined by in vitro testing, usually by disk-diffusion test. However, in vitro testing does not always reflect antibacterial efficiency of antibiotics in vivo. In this investigation, the urine samples obtained in a single oral dose pharmacokinetic study were examined for their bactericidal activity against a range of relevant Gram-positive urinary tract pathogens. Urinary bactericidal activity of linezolid had been previously compared with ciprofloxacin but not with other oral antibiotics such as b-lactams. Linezolid showed satisfactory urinary bactericidal titres throughout the whole testing period against all Gram-positive cocci. Fluoroquinolones displayed high and persisting levels of urinary bactericidal activity against staphylococci, but their activity against enterococci was weaker. According to the results of ex-vivo testing amoxycillin could be recommended only for infections caused by E. faecalis. Amoxycillin combined with clavulanic acid can be considered as a therapeutic option for infections caused by S. saprophyticus and E. faecalis. Older cephalosporins had high titres only against S. saprophyticus. Their drawback is a short elimination half-time in urine resulting in rapid decrease of urinary bactericidal titers during dosing interval. Furthermore, they do not show activity against enterococci due to their intrinsic resistance to cephalosporins.
