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First report of CTX-M beta-lactamases from Bosnia and Herzegovia

FIRST REPORT OF CTX-M β -LACTAMASES FROM BOSNIA AND HERZEGOVINA B. Bedenić1, S. Uzunovic- Kamberovic2, J Vranes3 1. Department of Microbiology, School of Medicine, University of Zagreb 2. Cantonal Institute of Public Health, Zenica, Bosnia and Herzegovina 3. Zagreb Institute of Public Health, Zagreb, Croatia 5. National Institute of Public Health, Warshaw, Poland Background and aim Plasmid-mediated extended- spectrum β -lactamases (ESBL) are most commonly of the TEM, SHV or CTX-M type. To date more than 120 TEM enzymes, more than 50 SHV enzymes, and more than 30 CTX-M have been reported (www.lahey.org/studies). CTX-M enzymes are increasingly found in eneterobacterial species around the world. They have a much higher level of activity against cefotaxime and ceftriaxone than ceftazidime. They are derived from the chromosomal β -lactamases of the genus Kluyvera. Recently first E. coli strains with high resistance to cefotaxime and ceftriaxone have been isolated in Zenica-Doboj Canton in Bosnia and Herzegovina. The aim of this study was to characterize β - lactamases produced by these isolates. Materials and methods Two Escherichia coli strains with unusual resistance phenotype (no inhibition zones around cefotaxime and ceftriaxone disks) were isolated in the Laboratory for Sanitary Microbiology in Zenica, Bosnia and Herzegovian. Extended-spectrum β -lactamases (ESBL) were detected by double-disk synergy test and CLSI combined disk test using both ceftazidime and cefotaxime disks. Susceptibility to a wide range of antibiotics was determined by the broth microdilution method according to CLSI. The transfer of the cefotaxime resistance determinants was determined by the broth mating method using E coli recipient resistant to rifampicin. ESBLs were characterized by isoelectric focusing, substrate profile determination, PCR and sequencing of blaCTX-M genes. Genetic relatedness between the strains was tested by PFGE. Results The both isolates were highly resistant to cefotaxime, ceftraxone, cefuroxime, amoxicillin and gentamicin (MIC >128 mg/L). MICs of ceftazidime and aztreonam were also quite high (64 and 128 mg/L respectively). One isolate was resistant to cefoxitin. The strains were susceptible to ciprofloxacin and carbapenems. MICs of cefotaxime were strongly reduced in the presence of clavulanate (eight to ten dilutions). Resistance to cefotaxime was transferred to E. coli recipient from two of the strains with low frequency (2.6 and 6.3 x 10-7). Resistance to gentamicin, cotrimoxazole and cloramphenicol was cotransferred alongside with cephalosporine resistance. PCR has detected blaCTX-M genes in both isolates. Sequencing of blaCTX-M genes revealed CTX-M-15 β - lactamase in both isolates. The both isolates possessed an additional TEM-1 β -lactamase. PFGE showed that the isolates were not clonally related. Conclusions This is the first report of CTX-M β -lactamases from Bosnia and Herzegovina. CTX-M-15 β -lactamase was previously reported from many countries in the world such as Croatia, , Bulgaria, Austria, Poland, Switzerland, United Kingdom thus we can conclude that it is widespreas in Europe. Carbapenems and fluoroquinolones should be recommended as antibiotics of choice for the treatment of infections caused by our CTX-M producing bacteria. Since, there was no clonal spread of CTX-M producing E. coli strains in the community of Zenica – Doboj Canton according to PFGE, we could conclude that the CTX-M producing isolates ocurred independently.

CTX-M beta-lactamases; Escherichia coli; cefotaxime

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