Sestre Milosrdnice University hospital and Institute of Clinical Medical Research
Abstract
Moraxella catarrhalis, a commensal of the nasopharynx, has been recognized with increasing frequency as a potential pathogen in respiratory tract infections. The ß-lactamase production in Moraxella catarrhalis, first described in 1977, has been ever more frequently reported in many countries of the world. However, there have no such reports from Croatia so far. The aim of this study was to investigate antibiotic susceptibilities and ß-lactamase production in Moraxella catarrhalis isolates from Croatia. Fifty Moraxella catarrhalis strains were collected from various clinical specimens at Zagreb University Children\u27s Hospital during the 1990-1992 period. Antibiotic susceptibilities to a wide range of antibiotics were determined by the broth microdilution method according to NCCLS. In all strains, ß-lactamases were detected by the disk chromogenic substrate (nitrocefin) test. The prevalence of ß-lactamase positive strains in the study period was 100%. No resistance to amoxicillin/clavulanate, cephalexin, ceftibuten, tetracycline, erythromycin, azithromycin and chloramphenicol was observed. In all strains, the activity of amoxicillin was strongly enhanced in the presence of clavulanic acid. Older cephalosporins were equally active, however, the thirdgeneration cephalosporin ceftibuten showed significantly lower minimal inhibitory concentrations compared with older compounds. Among non ß-lactam antibiotics, tetracycline and erithromycin showed similar activity. Azithromycin had a markedly stronger inhibitory activity in comparison with erythromycin and tetracycline. According to our results, amoxicillin combined with clavulanic acid should be the antibiotic of choice for the treatment of infections caused by ß-lactamase positive isolates of Moraxella catarrhalis. Oral cephalosporins, tetracycline, macrolides or azithromycin could be an option too.Moraxella catarrhalis se je ranije smatrala komenzalom u respiracijskom traktu, ali se danas zna da je ona značajan respiracijski patogen. Proizvodnja ß-laktamaze, prvi puta opisana 1977., javlja se sa sve većom učestalošću u mnogim zemljama svijeta. Dosadnije bilo izvještaja iz Hrvatske. Cilj ovoga istraživanja bio je ispitati osjetljivost na antibiotike i proizvodnju ß-laktamaze u kliničkim izolatima Moraxella catarrhalis iz Hrvatske. Pedeset izolata Moraxella catarrhalis prikupljeno je iz različitih kliničkih uzoraka u Klinici za dječje bolesti Zagreb od 1990. do 1992. godine. Osjetljivost na antibiotike je određivana mikrodilucijskom metodom prema NCCLS. Proizvodnja ß-laktamaza je utvrđivana metodom diska s kromogenim supstratom (nitrocefinski test). Supstratni profil je određivan biološkom metodom. ß-Laktamaze su dokazane pomoću nitrocefinskog testa u svim sojevima. Učestalost ß-laktamaza pozitivnih izolata Moraxella catarrhalis u ispitivanom razdoblju je iznosila 100%. Nije zapažena rezistencija na amoksicilin/klavulanat, cefaleksin, ceftibuten, tetraciklin, eritromicin, azitromicin i kloramfenikol. Aktivnost amoksicilina se je značajno pojačala u prisutnosti klavulanske kiseline u svim sojevima. Stariji cefalosporini su bili podjednako djelatni, dok je ceftibuten kao cefalosporin treće generacije imao značajno niže minimalne inhibicijske koncentracije u odnosu na starije generacije. Među ne ß-laktamskim antibioticima tetraciklini i eritromicin su imali slične minimalne inhibicijske koncentracije. Azitromicin je imao jače inhibicijsko djelovanje od tetraciklina i eritromicina. Prema rezultatima našega istraživanja amoksicilin u kombinaciji s klavulanskom kiselinom bi bio antibiotik izbora za liječenje infekcija uzrokovanih sojevima Moraxella catarrhalis pozitivnim na b-laktamazu. Oralni cefalosporini, eritromicin, tetraciklini i azitromicin bi također mogli predstavljati moguću terapiju
