I. Barcina et al., DIRECT VIABLE COUNT OF GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA USINGCIPROFLOXACIN AS INHIBITOR OF CELLULAR DIVISION, Journal of microbiological methods, 22(2), 1995, pp. 139-150
Following the method described by Kogure et al. (Can. J. Microbiol. 25
(1979) 415-420), we used ciprofloxacin, a quinolone which inhibits ce
ll division of Gram-positive and Gram-negative bacteria, to quantify t
he number of viable bacteria in a series of cultures. As test bacteria
we used three Escherichia coli strains, two of them sensitive to nali
dixic acid and a third resistant to this inhibitor, and three Gram pos
itive bacteria: one rod (Lactobacillus plantarum) and two cocci (Enter
ococcus faecalis and Micrococcus varians). Ciprofloxacin is an efficie
nt inhibitor of cell division in all six strains, although the effect
on the morphology of the rods and cocci was clearly different. The per
centage of viable bacteria was determined in the case of the rods by t
he increase in either length or biovolume and, for the cocci, by the i
ncrease in cell biovolume. Image analysis was required to detect varia
tions in cell biovolume in the case of cocci and rods. For nalidixic a
cid-sensitive strains, it was possible to use both, as similar percent
ages of viable bacteria were detected with both inhibitors. The differ
ences between the colony forming units (CFU) and direct viable (DVC) c
ounts were much higher in the strains showing typical arrangements tha
n in those strains without them. Finally, we found no significant diff
erences in the number of viable bacteria in the natural population of
the Butron river when we used either ciprofloxacin or nalidixic acid a
s inhibitors of cell division.