Application of a spectrophotometric method for the determination of post-antibiotic effect and comparison with viable counts in agar.
The post-antibiotic effects of gentamicin and ciprofloxacin at 1x, 2x and 4x MIC on Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 were studied using a spectrophotometric method and the classic method of viable counts on agar as a reference. Monitoring of the growth kinetics was carried out by viability counting on the plate every hour and by means of the optical density of the cultures measured by spectrophotometry at a wavelength of 450 nm. No statistically significant differences were found between the results obtained with the spectrophotometric method and the reference method. The former method was much quicker, much easier to use and to replicate.
Microbiology Service, General Specialty Hospital Virgen de las Nieves, Granada, Spain. cdiagnostico@hsa.sas.cica.es
M C
MC
Domínguez
M
M
de La Rosa
M V
MV
Borobio
D000362:Agar; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development*; D002939:Ciprofloxacin / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005839:Gentamicins / Q000494:pharmacology*; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development; D013053:Spectrophotometry / Q000379:methods*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D005839:Gentamicins; D002939:Ciprofloxacin; D000362:Agar