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NG = no growth from upper<br />

surface of dressing after subculture<br />

onto new medium;<br />

+ = light growth,<br />

++ = growth,<br />

+++ = heavy growth.<br />

All three Leptospermum<br />

honey impregnated calcium<br />

alginates were effective<br />

barriers against strikethrough<br />

of staphylococci.<br />

Table 1. Semi-quant<strong>it</strong>ative growth of 3 species of bacteria on <strong>the</strong> upper surface of six dressings (barrier effect)<br />

Dressings<br />

Leptospermum impregnated<br />

calcium alginate 1<br />

Leptospermum impregnated<br />

calcium alginate 2<br />

Leptospermum impregnated<br />

calcium alginate 3<br />

Leptospermum impregnated<br />

tulle<br />

Buckwheat impregnated<br />

mesh<br />

Multifloral impregnated<br />

mesh<br />

Figure 1. Zones of inhib<strong>it</strong>ion caused by six wound<br />

dressings against EMRSA-15.<br />

Zones of inhib<strong>it</strong>ion were observed around dressings<br />

1-4 <strong>the</strong> Lepto spermum honey impregnated dressings<br />

indicating that <strong>the</strong> test organisms were inhib<strong>it</strong>ed.<br />

No zones of inhib<strong>it</strong>ion seen around dressings 5 and 6<br />

<strong>the</strong> buckwheat and multi floral honey impregnated<br />

dressings.<br />

Dressings: Six different commercial honey impregnated<br />

dressings were used in <strong>the</strong> study:<br />

1. Leptospermum impregnated calcium alginate<br />

2. Leptospermum impregnated calcium alginate<br />

3. Leptospermum impregnated calcium alginate<br />

4. Leptospermum impregnated tulle<br />

5. Buckwheat impregnated mesh<br />

6. Multi floral impregnated mesh<br />

TEST METHODS<br />

Zone of inhib<strong>it</strong>ion: This tests measures <strong>the</strong> release of antimicrobial<br />

agents from dressings, <strong>it</strong> is an adaptation of a<br />

technique used to determine <strong>the</strong> antimicrobial sens<strong>it</strong>iv<strong>it</strong>y<br />

of organisms, by Thomas & McCubin, 2003.<br />

12<br />

Oxford<br />

Staphylococcus aureus<br />

EMRSA P. aeruginosa<br />

NG NG +++<br />

NG NG +++<br />

NG NG +++<br />

NG ++ +++<br />

+ + +++<br />

+ ++ +++<br />

Figure 2. Zones of inhib<strong>it</strong>ion caused by each of six dressings against<br />

three species of bacteria.<br />

Solid line indicated Staphylococcus aureus most sens<strong>it</strong>ive to <strong>the</strong> dressings<br />

giving largest zones of inhib<strong>it</strong>ion. Dashed line indicates zones of inhib<strong>it</strong>ion<br />

against EMRSA-15. Solid filled bars indicate zones of inhib<strong>it</strong>ion seen against<br />

Pseudomonas aeruginosa, much sm<strong>all</strong>er zones seen, indicating less sens<strong>it</strong>iv<strong>it</strong>y<br />

to <strong>the</strong> honey impregnated dressings.<br />

Test cell suspensions were prepared from 24 hour broth<br />

cultures of each organism, diluted w<strong>it</strong>h sterile broth to<br />

give optical dens<strong>it</strong>y <strong>read</strong>ings between 0.5 and 1 using a<br />

spectrophotometer (Cecil Instruments, Cambridge, UK)<br />

at wavelength 540nm. Sterile molten Tryptic Soy Agar<br />

(TSA) (Oxoid, Cambridge, UK) 200ml was inoculated<br />

w<strong>it</strong>h 0.2ml of <strong>the</strong> broth culture and poured into bio assay<br />

plates. Samples of <strong>the</strong> dressings cut to 2 x 2 cm squares<br />

were placed evenly on <strong>the</strong> plates once set and incubated<br />

overnight at 37°C. After incubation plates were examined<br />

for zones of inhib<strong>it</strong>ion, if one was detected <strong>the</strong> length and<br />

width were measured in mm.<br />

EWMA Journal 2008 vol 8 no 3

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