Biology Reference
In-Depth Information
Saccharomyces cerevisiae (Kubo et al .,
1992; Kubo and Fujita, 2001).
Similarly, the bactericidal effect of
dodecanol was also confirmed by the time
kill curve method as shown in Fig. 16.6.
longer showed any activity up to 100 mg/ml.
In other words, dodecanol is the most effec-
tive. On the other hand, hexanol (C6) did
not exhibit any activity against S. cholerae-
suis up to 1600 mg/ml. It appears that
S. choleraesuis showed different suscepti-
bility to alkanols possessing different chain
length. The similar parabolic function of the
lipophilicity and maximized with alkyl
chain lengths was previously reported with
a series of alkyldimethylbenzylammonium
chlorides (Daoud et al ., 1983). Notably, no
alkanol exhibits any noticeable antibacte-
rial activity against the other Gram-negative
bacteria tested: E. coli, P. aeruginosa,
E. aerogenes, P. vulgaris and H. pylori . In
other words, alkanols fall short of the broad
spectrum of activity as far as Gram-negative
bacteria are concerned but specifically
against S. choleraesuis . It seems that S. chol-
eraesuis differs from other Gram-negative
bacteria. This difference may be caused by
their different permeability of the outer
membrane layer because this plays a major
role in the general resistance of Gram-
negative bacteria, especially to lipophilic
antibiotics. Noticeably, most Gram-negative
bacteria are surrounded by the outer mem-
brane and this functions as an effective but
less specific barrier (Nikaido, 1994). If the
selective elimination of Salmonella bacteria
is desirable, alkanols may be considered to
be superior.
The bactericidal effect of decanol
against S. choleraesuis was confirmed by
the time kill curve method as shown in
Fig. 16.5. Cultures of S. choleraesuis , with a
cell density of 5 × 10 5 CFU/ml, were exposed
to two different concentrations of decanol.
The number of viable cells was determined
following different periods of incubation
with decanol. The result verifies that MIC
and MBC are the same. It shows that ½MIC
slowed growth but that the final cell count
was not significantly different from the con-
trol. The result shows that lethality occurred
notably quickly, within the first 1 h after the
addition of decanol. This rapid lethality
very likely indicates that the antibacterial
activity of decanol against S. choleraesuis is
associated with the disruption of the mem-
brane, similar to the effect described against
8
7
6
5
4
3
2
1
0
0
12
20
24
4
8
Incubation time (h)
16
Fig. 16.5. Effect of decanol on the growth of
S. choleraesuis subsp. choleraesuis ATCC 35640.
Exponentially growing cells were inoculated into
NYG broth and cultured at 37°C. Decanol, 0 ( ),
25 ( ), and 50 ( ) m g/ml.
8
7
6
5
4
3
2
1
0
0
4
8 12
Incubation time (h)
16
20
24
Fig. 16.6. Effect of dodecanol on the growth of
S. choleraesuis subsp. choleraesuis ATCC 35640.
Exponentially growing cells were inoculated into
NYG broth and then cultured at 37°C. Dodecanol,
0 ( ), 3.13 ( ), and 6.25 ( ) m g/ml.
 
 
Search WWH ::




Custom Search