Biologia, Bratislava, 56/Suppl. 9: 43-47, 2001.

ISSN 0006-3088 (Biologia). ISSN 1335-6399 (Biologia. Section Cellular and Molecular Biology).

 

Full Paper

Values of minimum inhibitory concentrations of antibiotics in Stenotrophomonas maltophilia clinical strains influence of an extended incubation period.

 

Petr Hejnar*, Milan Kolar & Dagmar Koukalova

Department of Microbiology, Faculty of Medicine, Palacky University, Hnevotinska 3, CZ-77515 Olomouc, Czech Republic; tel.: ++ 420 68 5632406, fax: ++ 420 68 5632966, e-mail: hejnar@fnol.cz

* corresponding author

Received: December 28, 2000 / Accepted: June 15, 2001

 

Abstract

In 106 Stenotrophomonas maltophilia clinical strains the susceptibility to 19 kinds of antibiotics was tested by the broth dilution micromethod at 24 and 48 h incubation. Isolated strains demonstrated the lowest frequency of resistance to cotrimoxazole (7.5% of resistant strains at 24 h incubation and 18.9% at 48 h), to ofloxacin (13.2% and 30.2%), to ciprofloxacin (19.8% and 50.9%) and to cefoperazone/sulbactam (20.8% and 37.7%). The lowest increase of the number of resistant strains after extended incubation was recorded in gentamicin (by 10.4%), ceftazidime (by 11.3%) and cotrimoxazole (by 11.4%). On the contrary, the highest increase of resistance occurrence was demonstrated in cefoperazone and ciprofloxacin (by 31.1%). Average values of the growth of minimum inhibitory concentrations (MICs) were the smallest in ciprofloxacin and ofloxacin (2.3 times), the biggest in piperacillin/tazobactam (4.5 times) and piperacillin (5.0 times). As far as the stability of MIC is concerned, the biggest occurrence of strains with the MIC growth doubled as a maximum was found in ceftazidime (78.4%), ofloxacin (76.1%) and ciprofloxacin (75.3%), the smallest in piperacillin/tazobactam (43.2%) and piperacillin (38.9%). The importance of incubation extended to 48 h during the testing of S. maltophilia strains was pointed out for correct setting their susceptibility to antibiotics.

 

Key words: S. maltophilia, resistance to antibiotics, influence of extended incubation.