- Email: [email protected]
Improvements in medicated tulle dressings
Journal
of Hospital
Infection
(1983) 4, 391-398
Improvements S. Thomas,
in medicated C. E. Dawes
tulle dressings and N. P. Hay
Mid Glamorgan Surgical Dressings Unit, East Glamorgan Hospital, Church Village, Near Pontypridd, Mid Glamorgan Summary:
The antibacterial activity of four new medicated tulle dressings was determined by a modified zone inhibition method. Six different test organisms were used and from the results of the investigation, it was concluded that although the dressings differed in their duration of action and the rate at which the medicaments were released from their individual formulations, they all possessed significant antimicrobial activity.
Introduction Since tulle gras was first introduced as a treatment for wounds during the First World War, it has become widely used in a variety of applications, particularly where large areas of tissue are to be dressed. Tulle, as it was originally described in the British Pharmaceutical Codex of 1949, consisted of a leno weave cotton or viscose cloth impregnated with a base of yellow soft paraffin containing 1.25 per cent Balsam of Peru. which was thought to impart mild antibacterial properties. Following reports of skin reactions in some patients (Trevethick, 1957) the Balsam of Peru was subsequently omitted. With the advent of sulfonamides and penicillins, medicated tulles became popular once again but the emergence of bacterial resistance associated with the use of topical antibiotics and related compounds led to a decline in their use. An alternative product containing 0.5 per cent chlorhexidine acetate in a paraffin base ‘Bactigras’ was developed which was claimed to be active against a wide range of bacteria without the problems associated with the use of topical antibiotics. Laboratory studies suggested, however, that this material failed to demonstrate the degree of activity which was expected due to the poor release of the chlorhexidine acetate from the hydrophobic paraffin base (Thomas and Russell, 1976; Andrews, Buchan and Horlington, 1982). The purpose of this study was to investigate the antibacterial activity of four new dressings containing either chlorhexidine hydrochloride, chlorhexidine gluconate or povidone-iodine in a hydrophilic base to determine if changes in formulation would result in enhanced antibacterial activity.
0195 h701.‘83~04n391
-08
53 19X3 ‘I-he Hospml
$02 00,.
391
Infectwn
Society
392
S. Thomas et al. Materials
and methods
All the new dressings were prepared from a standard knitted viscose fabric impregnated with polyethylene glycol containing either 0.5 per cent chlorhexidine gluconate, 0.5 per cent chlorhexidine hydrochloride, 5 per cent povidone-iodine (equivalent to 0.5 per cent available iodine) or 10 per cent povidone-iodine (equivalent to 1 per cent available iodine). The dressings were sealed in pouches made from a laminate of polyethylene, aluminium foil and paper and then sterilized by irradiation. In addition, two other medicated tulle dressings were included in the study for comparison. These were ‘Sofra-tulle’ (Roussel) containing 1 per cent framycetin sulphate and ‘Bactigras’ (Smith and Nephew) containing 0.5 per cent chlorhexidine acetate in a paraffin base. A non-medicated tulle, ‘Paratulle’ (Edwin Burgess Ltd) was included as a control. Test organisms Laboratory strains of Streptococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus mirabilis were used throughout the testing procedure. Method one A series of plastic petri dishes, 15 cm in diameter each containing a layer of Iso-Sensitist Agar (ISA, Oxoid) or blood agar (Oxoid) all 1 cm thick, were dried at 32°C for 2 h, inoculated with 0.4 ml of a 24 h broth culture of the test organism and dried for a further hour at 32°C. Portions of each dressing 2.5 mm square were placed on each plate and incubated at 32°C for 24 h after which time any zones of inhibition around the edges of the dressing were measured. This procedure was repeated on a second day using freshly inoculated plates but retaining the same sample of each dressing to detect the presence of residual antimicrobial activity. Method two Petri dishes, containing ISA or blood agar were dried and inoculated with each test organism as before. After drying, agar plugs 17 mm in diameter were removed and placed with their contaminated side downwards upon 25 mm square samples of each dressing placed upon the surface of a sterile plate containing ISA or blood agar as appropriate. Results The results of the first test method, designed to determine both the spectrum and duration of the activity of each of the dressings, clearly demonstrated that all four products possessed considerable antibacterial activity against all
1 Blood
____.agar
agar
- =growth
-
0.5
0.5
Test
* * + -
2 2
detectable directly
+ + + + + -t
1* *
Ractigras .-~-
beneath; * = growth visible in interstices;
T -
r
2
2
+ -
;:;
i
-
2 0.5
0.5
Chlorhexidine hydrochloride _--
2 1
1
Chlorhexidine gluconate ~---
I. Zones of inhibition around test dressings (mm)
materials Iodine 10%
up to margin of dressing but no growth
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Stash. aureus Str: faecalis
Day 2 Blood
Ps. aeruginosa K. bneumoniae Pr.*mirabilis E. coli Staph. aureus SW. faecalis
Day
Organism
Povidone -___ 5%
Table
+ = growth
OZ 1 *
* *
1 2* 3 3 *
*
Sofratulle -___-
inhibition inhibition inhibition inhibition inhibition inhibition
inhibition inhibition inhibition inhibition inhibition inhibition
under dressing.
30 No No No No No
No No No No No No
Paratulle
1 Iso-sensitest
agar
agar
H = zone of reduced growth; under dressing.
Ps. amuginosa K. pneumoniae Pr. mirabilis E. coli Staph. aureus SW. faecalis
Day 2 Iso-sensitest
Ps. aeruginosa K. pneumoniae PI. mirabilis E. coli Staph. aureus Str. fuecalis
Day
Organism
3 9
2
11
g CR)
i (RI
; *
*
*
+
-
1 -
* * *
Bactigras
1 W 3 *
:
1;
i (RI
3 ;k) 5 (R) 2
Sofratullc
No No No No No No
No No No No No No
+ = growth
inhibition inhibition inhibition inhibition inhibition inhibition
inhibition inhibition inhibition inhibition inhibition inhibition
Paratulle
- = growth up to margin of dressing but no growth detected beneath dressmg; * = growth visible in interstices;
-
1
2
-
-
+
ii 6
: 1
Chlorhexidine hydrochloride
around test dressings (mm)
f
::
:
3 3
Chlorhexidine gluconate
Zones of inhibition
+ -
3 3 4
10%
3 2.5 6
5%
II.
materials
Povidone-iodine
Test
Table
i = growth (see text).
present
Day 2 Blood agar Ps. aeruginosa K. pneumoniae l’r. mirabilis E. coli Staph. aureus Str. faecalis
Day 1 Blood agar Ps. aeruginosa K. pneumoniae Pr. mirabilis R. coli Staph. aureus Str. faecaiis
Organism
III.
beneath
dressing;
+ + + + 0 - = no growth
l’ovidone-iodine 5 ‘Y. lWO -~ -__-.
‘I’est material
‘l’able
detected
_ ..-
beneath
0 0 + -
-__
challenge
0 = no growth
0 + + -
Chlorhexidine hydrochloride ____
microbial
dressing;
of a heavy
Chlorhexidine gluconate
Eflect
beneath
_.
(p&q
dressing
Bactigras
methodi
hut evidence
+ c t -
+ + -
of growth
Sofratulle -.~-
around
the margin
+ + + + +
+ + + +
Paratulle
1 Iso-sensitest
+ =growth (see text).
agar
agar
-
+ + -t -t
-
5%
+ 0 0 0 0 -
-
10%
+ + -
0 -
+ -
-
Chlorhexidine hydrochloride
-
Chlorhexidine gluconate
+ + + + -
+ + + + -
Bactigras
+ + -
-
Sofratulle
+ + + + + +
+ + + + + +
Paratulle
present beneath dressing; - = no growth detected beneath dressing; 0 = no growth beneath dressing but evidence of growth around the margin
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Staph. uureus Str. faecalis
Day 2 Iso-sensitest
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Staph. aureus Str. faecalis
Day
Organism
IV. Effect of a heavy microbiul challenge (plug method) material
Povidone-iodine
Test
‘I’able
Improved
tulle
dressings
397
of the organisms tested (Tables I and II). Sufficient activity was retained even after 2 days, to exert a significant effect upon the majority of the test organisms, although a reduction in activity was noted. The second test method was designed to simulate the effect of a massive microbiological challenge to a non infected wound. The agar plate represented the wound with the agar plug providing the source of contamination (Tables III and IV). The results of this method were comparable with those obtained previously and although all of the new products prevented growth of the organisms on the sterile ISA plate after 24 h, the povidone-iodine dressings were less effective than the two new chlorhexidine products after prolonged incubation in the presence of blood agar. In several instances, it was noted that although no growth occurred directly beneath the dressing and the contaminated plug, some growth was evident around the margin of the test samples suggesting that some organisms had travelled along the surface of the fibres of the dressing on to the surrounding agar. Discussion
Polyethylene glycols (PEG), the base material used in these dressings, are condensation polymers of ethylene oxide and water, available with molecular weights in the range of 200-4000. Materials of different molecular weight may be blended to obtain any desired viscosity. Polyethylene glycols are strongly hydrophilic with a tendency to be hydroscopic and have been used as the basis of a variety of topical drug carrier systems including creams, suppositories and pessaries. In contrast to the traditional tulle materials, formulations based upon PEG may be easily removed by gentle cleansing with water or saline. This can be a considerable advantage in the management of a wound especially if it is to receive a skin graft. Their hydrophilic nature also means that any medicament present is more readily available to extraction by an aqueous environment. This is in marked contrast to the use of a traditional paraffin tulle base as a carrier for a medicament as previous studies have shown that even vigorous extraction with water at 25“C or immersion in plasma at 37’C failed to extract significant amounts of chlorhexidine from a paraffin base (Thomas and Russell, 1976). Andrews et al. (1982) questioned the value of in-vitro testing of these dressings, claiming that such tests give an unrealistically low estimate of the activity that the product would have in viva as their animal study revealed a significant reduction in the numbers of Staph. aureus in standard pig wounds dressed with a chlorhexidine tulle (‘Bactigras’) when compared with similar wounds dressed with a non-medicated tulle as a control. Lawrence (1977 a&) similarly reported that this material was effective in controlling colonization of wounds by Staph. aureus in-vivo. Minimum inhibitory concentrations of chlorhexidine gluconate for
398
S. Thomas
et al.
various micro-organisms are published in the handbook I.C.I. Antiseptics in Practice which reports that the growth of six strains of Staph. aureu~ was prevented by l-2 mg/l of chlorhexidine gluconate. Other potential pathogens such as Ps. aeruginosa and Pr. mirabilis required concentrations considerably in excess of this value from 3 to 60 pg/ml and 25-100 mg/l respectively. The results of the laboratory studies suggest that the quantities of chlorhexidine which are released from the paraffin base, although very low, are sufficient to exert some effect upon Staph. aureu~ but are too low to produce any significant effect upon the other organisms tested. In contrast, the new formulation based upon PEG released much greater quantities of the antimicrobial to produce levels which were able to inhibit the growth of even the most resistant of the organism tested. If the claim of Andrews et al. (1982) that the in-vitro test produces a low estimate of a product’s probable in duo activity is correct, then it is likely that these new formulations (which performed well in the laboratory) will be extremely active clinically and provide a significant advance in the battle against wound infection. References Andrews, J. K., Buchan, I. A. & Horlington, M. (1982). An experimental evaluation of a chlorhexidine medicated tulle gras dressing. Journal of Hospital Infection 3, 149-I 57. I.C.I. Antiseptics in Practice published by I.C.I. Ltd (1978) pp. 32-33. Lawrence, J. C. (1977a). The treatment of small burns with a chlorhexidine medicated tulle gras. Burns 3, 239-244. Lawrence, J. C. (19776). Minor burns. Nursing Mirror 144, 58-60. Thomas, S. & Russell, A. D. (1976). An in vitro evaluation of Bactigras, a tulle dressing containing chlorhexidine. Micyobios Letters 2, 169-177. Trevethick, R. A. (1957). Sensitization to Tulle Gras Dressings (Letter). British Medical Journal 2, 883-884.
of Hospital
Infection
(1983) 4, 391-398
Improvements S. Thomas,
in medicated C. E. Dawes
tulle dressings and N. P. Hay
Mid Glamorgan Surgical Dressings Unit, East Glamorgan Hospital, Church Village, Near Pontypridd, Mid Glamorgan Summary:
The antibacterial activity of four new medicated tulle dressings was determined by a modified zone inhibition method. Six different test organisms were used and from the results of the investigation, it was concluded that although the dressings differed in their duration of action and the rate at which the medicaments were released from their individual formulations, they all possessed significant antimicrobial activity.
Introduction Since tulle gras was first introduced as a treatment for wounds during the First World War, it has become widely used in a variety of applications, particularly where large areas of tissue are to be dressed. Tulle, as it was originally described in the British Pharmaceutical Codex of 1949, consisted of a leno weave cotton or viscose cloth impregnated with a base of yellow soft paraffin containing 1.25 per cent Balsam of Peru. which was thought to impart mild antibacterial properties. Following reports of skin reactions in some patients (Trevethick, 1957) the Balsam of Peru was subsequently omitted. With the advent of sulfonamides and penicillins, medicated tulles became popular once again but the emergence of bacterial resistance associated with the use of topical antibiotics and related compounds led to a decline in their use. An alternative product containing 0.5 per cent chlorhexidine acetate in a paraffin base ‘Bactigras’ was developed which was claimed to be active against a wide range of bacteria without the problems associated with the use of topical antibiotics. Laboratory studies suggested, however, that this material failed to demonstrate the degree of activity which was expected due to the poor release of the chlorhexidine acetate from the hydrophobic paraffin base (Thomas and Russell, 1976; Andrews, Buchan and Horlington, 1982). The purpose of this study was to investigate the antibacterial activity of four new dressings containing either chlorhexidine hydrochloride, chlorhexidine gluconate or povidone-iodine in a hydrophilic base to determine if changes in formulation would result in enhanced antibacterial activity.
0195 h701.‘83~04n391
-08
53 19X3 ‘I-he Hospml
$02 00,.
391
Infectwn
Society
392
S. Thomas et al. Materials
and methods
All the new dressings were prepared from a standard knitted viscose fabric impregnated with polyethylene glycol containing either 0.5 per cent chlorhexidine gluconate, 0.5 per cent chlorhexidine hydrochloride, 5 per cent povidone-iodine (equivalent to 0.5 per cent available iodine) or 10 per cent povidone-iodine (equivalent to 1 per cent available iodine). The dressings were sealed in pouches made from a laminate of polyethylene, aluminium foil and paper and then sterilized by irradiation. In addition, two other medicated tulle dressings were included in the study for comparison. These were ‘Sofra-tulle’ (Roussel) containing 1 per cent framycetin sulphate and ‘Bactigras’ (Smith and Nephew) containing 0.5 per cent chlorhexidine acetate in a paraffin base. A non-medicated tulle, ‘Paratulle’ (Edwin Burgess Ltd) was included as a control. Test organisms Laboratory strains of Streptococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus mirabilis were used throughout the testing procedure. Method one A series of plastic petri dishes, 15 cm in diameter each containing a layer of Iso-Sensitist Agar (ISA, Oxoid) or blood agar (Oxoid) all 1 cm thick, were dried at 32°C for 2 h, inoculated with 0.4 ml of a 24 h broth culture of the test organism and dried for a further hour at 32°C. Portions of each dressing 2.5 mm square were placed on each plate and incubated at 32°C for 24 h after which time any zones of inhibition around the edges of the dressing were measured. This procedure was repeated on a second day using freshly inoculated plates but retaining the same sample of each dressing to detect the presence of residual antimicrobial activity. Method two Petri dishes, containing ISA or blood agar were dried and inoculated with each test organism as before. After drying, agar plugs 17 mm in diameter were removed and placed with their contaminated side downwards upon 25 mm square samples of each dressing placed upon the surface of a sterile plate containing ISA or blood agar as appropriate. Results The results of the first test method, designed to determine both the spectrum and duration of the activity of each of the dressings, clearly demonstrated that all four products possessed considerable antibacterial activity against all
1 Blood
____.agar
agar
- =growth
-
0.5
0.5
Test
* * + -
2 2
detectable directly
+ + + + + -t
1* *
Ractigras .-~-
beneath; * = growth visible in interstices;
T -
r
2
2
+ -
;:;
i
-
2 0.5
0.5
Chlorhexidine hydrochloride _--
2 1
1
Chlorhexidine gluconate ~---
I. Zones of inhibition around test dressings (mm)
materials Iodine 10%
up to margin of dressing but no growth
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Stash. aureus Str: faecalis
Day 2 Blood
Ps. aeruginosa K. bneumoniae Pr.*mirabilis E. coli Staph. aureus SW. faecalis
Day
Organism
Povidone -___ 5%
Table
+ = growth
OZ 1 *
* *
1 2* 3 3 *
*
Sofratulle -___-
inhibition inhibition inhibition inhibition inhibition inhibition
inhibition inhibition inhibition inhibition inhibition inhibition
under dressing.
30 No No No No No
No No No No No No
Paratulle
1 Iso-sensitest
agar
agar
H = zone of reduced growth; under dressing.
Ps. amuginosa K. pneumoniae Pr. mirabilis E. coli Staph. aureus SW. faecalis
Day 2 Iso-sensitest
Ps. aeruginosa K. pneumoniae PI. mirabilis E. coli Staph. aureus Str. fuecalis
Day
Organism
3 9
2
11
g CR)
i (RI
; *
*
*
+
-
1 -
* * *
Bactigras
1 W 3 *
:
1;
i (RI
3 ;k) 5 (R) 2
Sofratullc
No No No No No No
No No No No No No
+ = growth
inhibition inhibition inhibition inhibition inhibition inhibition
inhibition inhibition inhibition inhibition inhibition inhibition
Paratulle
- = growth up to margin of dressing but no growth detected beneath dressmg; * = growth visible in interstices;
-
1
2
-
-
+
ii 6
: 1
Chlorhexidine hydrochloride
around test dressings (mm)
f
::
:
3 3
Chlorhexidine gluconate
Zones of inhibition
+ -
3 3 4
10%
3 2.5 6
5%
II.
materials
Povidone-iodine
Test
Table
i = growth (see text).
present
Day 2 Blood agar Ps. aeruginosa K. pneumoniae l’r. mirabilis E. coli Staph. aureus Str. faecalis
Day 1 Blood agar Ps. aeruginosa K. pneumoniae Pr. mirabilis R. coli Staph. aureus Str. faecaiis
Organism
III.
beneath
dressing;
+ + + + 0 - = no growth
l’ovidone-iodine 5 ‘Y. lWO -~ -__-.
‘I’est material
‘l’able
detected
_ ..-
beneath
0 0 + -
-__
challenge
0 = no growth
0 + + -
Chlorhexidine hydrochloride ____
microbial
dressing;
of a heavy
Chlorhexidine gluconate
Eflect
beneath
_.
(p&q
dressing
Bactigras
methodi
hut evidence
+ c t -
+ + -
of growth
Sofratulle -.~-
around
the margin
+ + + + +
+ + + +
Paratulle
1 Iso-sensitest
+ =growth (see text).
agar
agar
-
+ + -t -t
-
5%
+ 0 0 0 0 -
-
10%
+ + -
0 -
+ -
-
Chlorhexidine hydrochloride
-
Chlorhexidine gluconate
+ + + + -
+ + + + -
Bactigras
+ + -
-
Sofratulle
+ + + + + +
+ + + + + +
Paratulle
present beneath dressing; - = no growth detected beneath dressing; 0 = no growth beneath dressing but evidence of growth around the margin
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Staph. uureus Str. faecalis
Day 2 Iso-sensitest
Ps. aeruginosa K. pneumoniae Pr. mirabilis E. coli Staph. aureus Str. faecalis
Day
Organism
IV. Effect of a heavy microbiul challenge (plug method) material
Povidone-iodine
Test
‘I’able
Improved
tulle
dressings
397
of the organisms tested (Tables I and II). Sufficient activity was retained even after 2 days, to exert a significant effect upon the majority of the test organisms, although a reduction in activity was noted. The second test method was designed to simulate the effect of a massive microbiological challenge to a non infected wound. The agar plate represented the wound with the agar plug providing the source of contamination (Tables III and IV). The results of this method were comparable with those obtained previously and although all of the new products prevented growth of the organisms on the sterile ISA plate after 24 h, the povidone-iodine dressings were less effective than the two new chlorhexidine products after prolonged incubation in the presence of blood agar. In several instances, it was noted that although no growth occurred directly beneath the dressing and the contaminated plug, some growth was evident around the margin of the test samples suggesting that some organisms had travelled along the surface of the fibres of the dressing on to the surrounding agar. Discussion
Polyethylene glycols (PEG), the base material used in these dressings, are condensation polymers of ethylene oxide and water, available with molecular weights in the range of 200-4000. Materials of different molecular weight may be blended to obtain any desired viscosity. Polyethylene glycols are strongly hydrophilic with a tendency to be hydroscopic and have been used as the basis of a variety of topical drug carrier systems including creams, suppositories and pessaries. In contrast to the traditional tulle materials, formulations based upon PEG may be easily removed by gentle cleansing with water or saline. This can be a considerable advantage in the management of a wound especially if it is to receive a skin graft. Their hydrophilic nature also means that any medicament present is more readily available to extraction by an aqueous environment. This is in marked contrast to the use of a traditional paraffin tulle base as a carrier for a medicament as previous studies have shown that even vigorous extraction with water at 25“C or immersion in plasma at 37’C failed to extract significant amounts of chlorhexidine from a paraffin base (Thomas and Russell, 1976). Andrews et al. (1982) questioned the value of in-vitro testing of these dressings, claiming that such tests give an unrealistically low estimate of the activity that the product would have in viva as their animal study revealed a significant reduction in the numbers of Staph. aureus in standard pig wounds dressed with a chlorhexidine tulle (‘Bactigras’) when compared with similar wounds dressed with a non-medicated tulle as a control. Lawrence (1977 a&) similarly reported that this material was effective in controlling colonization of wounds by Staph. aureus in-vivo. Minimum inhibitory concentrations of chlorhexidine gluconate for
398
S. Thomas
et al.
various micro-organisms are published in the handbook I.C.I. Antiseptics in Practice which reports that the growth of six strains of Staph. aureu~ was prevented by l-2 mg/l of chlorhexidine gluconate. Other potential pathogens such as Ps. aeruginosa and Pr. mirabilis required concentrations considerably in excess of this value from 3 to 60 pg/ml and 25-100 mg/l respectively. The results of the laboratory studies suggest that the quantities of chlorhexidine which are released from the paraffin base, although very low, are sufficient to exert some effect upon Staph. aureu~ but are too low to produce any significant effect upon the other organisms tested. In contrast, the new formulation based upon PEG released much greater quantities of the antimicrobial to produce levels which were able to inhibit the growth of even the most resistant of the organism tested. If the claim of Andrews et al. (1982) that the in-vitro test produces a low estimate of a product’s probable in duo activity is correct, then it is likely that these new formulations (which performed well in the laboratory) will be extremely active clinically and provide a significant advance in the battle against wound infection. References Andrews, J. K., Buchan, I. A. & Horlington, M. (1982). An experimental evaluation of a chlorhexidine medicated tulle gras dressing. Journal of Hospital Infection 3, 149-I 57. I.C.I. Antiseptics in Practice published by I.C.I. Ltd (1978) pp. 32-33. Lawrence, J. C. (1977a). The treatment of small burns with a chlorhexidine medicated tulle gras. Burns 3, 239-244. Lawrence, J. C. (19776). Minor burns. Nursing Mirror 144, 58-60. Thomas, S. & Russell, A. D. (1976). An in vitro evaluation of Bactigras, a tulle dressing containing chlorhexidine. Micyobios Letters 2, 169-177. Trevethick, R. A. (1957). Sensitization to Tulle Gras Dressings (Letter). British Medical Journal 2, 883-884.