Cotton gauze bearing non-diffusible quaternary ammonium salts ...

Anti-microbial Efficacy, Results and Discussion
(A) (B) (C) (D) (E) (F) (G)
Figure 6 shows that GPF was expressed on native gauze but not AEM 5700-treated gauze:
The photographs taken under UV light (in B&W and color) show that treating gauze with
trimethoxysilylpropyldimethyloctadecyl ammonium chloride at least curbs the expression of GPF in
gram (-) E coli bearing the GFP gene. The question remaining to be answered is whether or not E coli
was actually killed by the action of AEM 5700. Inoculation method: Cotton was autoclaved for 30 min.
Ampicillin resistant bacterial strain was inoculated with ampicillin (0.1mg /mL) and incubated at 37ºC
with 300 rpm shaking until A = 0.5, then diluted in LB+Amp. Native and modified cottons were put in
liquid media and were incubated either at 4ºC (results not shown) or 37°C (results, vide supra)]
[Photographs: Images were captured using a UVITEC-JAI camera and processed using UVITEC-
UVIPhotoMW Version 10.02 software]
under UV light
(A) (B) (C) (D)
under visible light
A B C D
Figure 7 shows the post-incubation appearance of Luria-Broth Agar plates streaked with native and modified cotton gauze under aseptic
conditions. Plates were incubated at 37°C for 24 hours and visualized under visible and UV light to monitor bacterial growth. On the LB agar plate
that was streaked with native cotton gauze, growth of GFP producing and non-producing bacteria can be followed (A, C). In contrast, no growth was
observed in the case of modified cotton (B, D).
Figure 8 shows under UV light the post-incubation appearance of LB and LBA (100µg/ml
ampicillin) media following inoculation with native and modified cottons
LB and LBA (100µg/ml ampicillin) media (5ml) were inoculated with native and modified cotton. The
tubes were incubated at 37°C with 300 rpm shaking for 24 hours. Bacterial growth in LB (F) and LBA
(G) media that were inoculated with native cotton gauze contrasted notably against sterile LB medium
containing a piece of cotton gauze (A). LB (B, D) and LBA (C, E) media inoculated with modified cotton
gauze showed no bacterial growth.
Conclusions
The quaternary amine strategy shows merit in the matter of producing improved
single-use cottons and related self-sterilizing products of medical significance.
References
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Industry
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Background Material - The Bacterial Wall and Quaternary Ammonium Salts
Figures 9 and 10 illustrate the difference
in wall structure of gram (+) and (-)
bacteria. Gram positive bacteria have a
thick peptidoglycan layer outside their
plasma membrane. In contrast, gram
negative bacteria have a thin
peptidoglycan layer and an outer (lipid
bilayer) lipid membrane (OM) containing
lipopolysaccharide (LPS). Quaternary
ammonium salts bearing long alkyl chains
have the property of disrupting the delicate
cell membrane and therefore do not need
to be absorbed in solution to show their
bactericidal effect.
Figure 9: Gram (+) bacterial wall
Figure 10: Gram (-) bacterial wall