Reliability of the colistin disk test in identification of Serratia marcescens and Serratia liquefaciens.
Resistance to polymycin B or E (colistin) in the disk test, which is used as a means of identification, was tested in 43 strains of Serratia marcescens and 26 of Serratia liquefaciens. While all strains had MIC values greater than 32 mg/l for colistin, false susceptibility to both polymyxins was encountered in the 24 h disk test in 9% of Serratia marcescens and 12-96% of Serratia liquefaciens strains, depending on the kind of polymyxin, temperature and duration of incubation. Using colistin disks and incubation at 25 degrees C for 48 h, the percentage of false susceptible results could be minimized.
D003091:Colistin / Q000494:pharmacology*; D003470:Culture Media; D004352:Drug Resistance, Microbial; D008826:Microbial Sensitivity Tests; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D012705:Serratia / Q000145:classification* / Q000187:drug effects / Q000254:growth & development; D012706:Serratia marcescens / Q000145:classification* / Q000187:drug effects / Q000254:growth & development; D013696:Temperature; D013997:Time Factors
D003470:Culture Media; D011113:Polymyxins; D011112:Polymyxin B; D003091:Colistin