Evaluation of disc susceptibility tests performed directly from positive blood cultures.
OBJECTIVE
To evaluate the accuracy of direct disc susceptibility testing performed from positive BACTEC blood culture vials, using a predetermined dilution protocol.


METHODS
Direct susceptibility testing was performed from 432 positive blood culture vials, generating 3829 antibiotic-organism results. Results were compared with those obtained by standard disc susceptibility testing according to Clinical Laboratory Standards Institute (CLSI) methods.


RESULTS
When results were compared with the reference method, no very major errors were detected. One (0.03%) major error and 89 (2.3%) minor errors were found. Error rates by organism group ranged from 1.3% for Pseudomonas aeruginosa to 8.2% for beta-haemolytic streptococci.


CONCLUSIONS
Direct susceptibility testing provided accurate susceptibility results for most organism-antibiotic combinations, with the exception of the beta-haemolytic streptococci.
Tan
T Y
TY
Division of Laboratory Medicine, Changi General Hospital, Singapore. thean_yen_tan@cgh.com.sg
Ng
L S Y
LS
Kwang
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LL
D000900:Anti-Bacterial Agents; D015169:Colony Count, Microbial; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods / Q000592:standards*; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects; D006801:Humans; D050296:Microbial Viability; D008828:Microbiological Techniques; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013291:Streptococcus / Q000187:drug effects
D000900:Anti-Bacterial Agents