INTRODUCTION:

Wound infection is one of the most common complication of any surgical procedure.¹ The risk factor for wound infection could be both due to patient as well surgical technique related.² Patient-related factors include coincident remote site infection, diabetes, cigarette smoking, systemic steroid use, obesity, extremes of age and poor nutritional status. Surgical-related factors include skin asepsis, duration of operation, antimicrobial prophylaxis, operating theatre environment, sterilisation of instruments, and surgical technique.³ Conventional suture materials require passage of a foreign material through tissue, which responds by evoking and inflammatory reaction.

Silk and other multifilament suture materials are associated with the phenomenon of ‘wicking,’ which makes the surgical site retentive to bacteria and allows for the ingress of bacteria into the tissues and thus acts as a reservoir for secondary infection.⁴ Staphylococcus aureus is the most commonly associated pathogen associated with the surgical site infections. The other organisms associated are: Enterobacteriaceae (18.8%), Enterococcus spp. (8.0%), Pseudomonas aeruginosa, Pseudomonas spp., Streptococcus spp., anaerobic bacilli, anaerobic cocci, Acinetobacter spp., and fungi like candida.^5,6

An ideal surgical tissue adhesive must meet the following criteria: strong binding strength, ease of application, tissue biocompatibility, biodegradable and reasonable cost. Cyanoacrylates demonstrate most of these properties, giving them an edge over the conventional wound closing agents.

Coover was the first to synthesize cyanoacrylate in 1959. The chemical structure of cyanoacrylate is H 2C = C (CN) COOR, where R- is any alkyl group ranging from methyl to decyl.⁷ The lower homologs were cytotoxic and its use in medicine was discontinued, however, higher homologs, starting from butyl are considered safe.^8,9 Cyanoacrylate preparations have been used for more than 50 years in surgery; they have an application is a diverse array of surgical procedures ranging from ophthalmic, orthopedic, gastrointestinal, microvascular to plastic surgeries.¹⁰

Cyanoacrylates are liquid monomers that polymerize on contact with wound moisture to form a solid bond. These solidified adhesives unite and hold the incised tissues stably, avoiding penetration of foreign bodies, thus promoting wound healing and vascularization.^11,12

The use of 2-octyl cyanoacrylate tissue adhesive is commonplace in plastic and cardiac surgery, and investigations showed that it was associated with a decrease in infection rates.^13,14 Cyanoacrylate tissue adhesive might act as a physical barrier restricting the ingress of micro-organisms into the tissues.¹⁵

The aim of this invitro study was to assess if iso-amyl cyanoacrylate tissue adhesive possessed an inherent antimicrobial activity. The organisms used were the ones that were commonly associated with wound infections. The null hypothesis for the study was that iso-amyl cyanoacrylate did not posses an inherent antimicrobial activity against pathogens commonly associated with surgical wound infection.

MATERIAL AND METHODS:

Bacterial cultures from the American Type Culture Collection (ATCC) were isolated for Staphylococcus aureus (ATCC 25923), Streptococcus mutans (ATCC 25175), pseudomonas aeruginosa (ATCC 27853) and candida albicans (10231). The organisms were incubated in nutrient broth at temperature of 35°C until reaching 0.5 on the McFarland scale (turbidity of bacterial suspension at a population of approximately 1.5 x 10⁸ organisms).

The inocula were then seeded on agar plates (150 mm in diameter) containing Brain Heart Infusion Agar following the Kirby-Bauer modified technique. 3 Wells of 8 mm diameter were punched in each plate and filled with 5μL, 10μL and 20μL respectively, of iso-amyl cyanoacrylate tissue adhesive (Amcrylate^® 0.25 ml) from freshly opened ampoules, under aseptic conditions. The antimicrobial effect iso-amyl cyanoacrylate tissue adhesives were compared to that of Ampicillin 10 mg and amphotericin B 10 mg, which acted as positive controls. The ampicillin acted as a control for the bacteria’s studied, whereas, amphotericin B was the control of choice fungal organism studied namely: candida. The plates were then incubated at 37^oC for 24 hours using 20L SSU bacteriological incubator.

After the completion of the incubation period, the agar plates were observed carefully to rule out any form of contamination by organisms other than the species which were standardized and inoculated for the purpose of the study. These plates were then analyzed to observe the bacterial inhibitory halos or zone of inhibition (if any). These bacterial inhibitory halos or zone of inhibition were then measured in millimeters and compared with the positive control namely: Ampicillin and Amphotericin B.

RESULTS:

Table 1 shows the measure of the zone of inhibition in millimeters for the organisms cultured in brain heart infusion agar studied after an incubation period of 24 hours. The gram positive aerobic organisms namely: Staphylococcus aureus and Streptococcus mutans showed a positive result, the size of the zone of inhibition increasing with the volume of the iso-amyl cyanoacrylate adhesive. Also, the zone of inhibition for the volume of 10 μL of the iso-amyl cyanoacrylate was equivalent to that obtained by Ampicillin. Candida albicans, an opportunistic fungus, also showed a zone of inhibition whose size increased with the volume of the iso-amyl cyanoacrylate adhesive. The anti-bacterial activity of 20 μL of iso-amyl cyanoccrylate was equivalent to that obtained by amphotericin B. Pseudomonas aeruginosa, a gram negative aerobic organism, did not show any anti-bacterial activity for the cyanoacrylate adhesive or ampicillin. Figure 1 and 2 shows an example of the inhibitory effect of the cyanoacrylate tissue adhesive.

Table 1: The measure of the zone of inhibition in millimeters for the organisms.

Organism	Iso-amyl cyanoacrylate			Control Ampicillin 10mg
Organism	5 Μl	10 Μl	20 μL	Control Ampicillin 10mg
Streptococcus mutans	12	14	16	14
Staphylococcus aureus	14	15	16	15
pseudomonas aeruginosa	-	-	-	0
Candida albicans	10	10.5	11	Amphotericin B
Candida albicans	10	10.5	11	11

Fig 1: No inhibitory effect of iso-amyl cyanoacrylate and Ampicillin on Pseudomonas aeruginosa.

Fig 2: Zone of inhibition against Staphylococcus aureus increases with increasing volume.

DISCUSSION:

Post-surgical wound closure is an important aspect of day to day clinical practice, it is routinely used with the intention of wound approximation or closure of the wound by primary union. The different materials are employed which include suture materials, tissue adhesives and surgical staples. The tissue adhesives commonly employed in medicine for wound closure include cyanoacrylate tissue adhesives with varying chain lengths such as methyl, butyl, amyl up to octyl are used. Newer innovative advancements are also seen in the form of Fibrin based tissue adhesives. Since these materials have been extensively used in the human body their biocompatibility and physical properties have been studied extensively. Clinical studies have proven that there are fewer wound infections associated with cyanoacrylate tissue adhesives¹⁴, however the inherent antimicrobial effect of iso-amyl cyanoacrylate tissue adhesives has yet to be explored, which was the rationale behind this study design. The organism selected for the study i.e. Staphylococcus aureus and Streptococcus mutans, pseudomonas aeruginosa and Candida albicans are the organisms that are commonly associated with surgical wound infections.^16,17,18

This study show that iso-amyl cyanoacrylate did have an inhibitory effect on aerobic, gram positive organisms namely: Staphylococcus aureus and Streptococcus mutans and Candida albicans, however there was no such effect on pseudomonas aeruginosa which is an aerobic, gram negative organism, these results are confluent with those obtained by a similar study.¹⁹ We observed that the antimicrobial activity increase with the increase in the volume of adhesive from 5-20 μL. The cyanoacrylate adhesive as well as ampicillin did not have any inhibitory effect on Pseudomonas aeruginosa, which is a common opportunistic pathogen associated with nosocomial infections. It is also known to be multi drug resistant.²⁰

The antibacterial effects of cyanoacrylate in gram positive bacteria than in gram-negative possibly because the latter are protected by an outer carbohydrate capsule.^21,22 The possible explanation for the inhibitory effect on gram positive organisms could be the strong electronegative charge of the polymer that could react with the cell wall of gram-positive organisms that have a positive charge, the gram-negative organism however is protected by the bacterial cell wall.^23,24

Cyanoacrylates are applied to the tissue margins in an unpolymerized form, following which polymerization occurs by anionic or zwitter-ionic interactions with hydroxide or amine groups presented in the body.^25,26 Cyanoacrylate polymer decomposed to produce cyanoacetate and formaldehyde which diffused out producing inhibition halos even in a polymerized state.^26,27

This study assessed the inhibitory effect, if any, of iso-amyl cyanoacrylate. The antibacterial activity could either be bacteriostatic or bactericidal. The limitation of the study is that this aspect was not assessed by this study. This can be done by inoculating sample obtained from the clear agar within the inhibitory halos and re-cultured on new bacterial culture plates. Another limitation of the study is that only the unpolymerized form of the adhesive was tested. Further tests using both the polymerized as well as the unpolymerized forms of the adhesives need to be tested, this would establish if the polymercaptan reaction has a role to play in the antimicrobial effect.

CONCLUSION:

Iso-amyl cyanoacrylate tissue adhesives have an antimicrobial effect on gram positive organisms and fungi commonly associated with surgical wound infections. This would be an added benefit these tissue adhesives have over conventional suture materials.

CONFLICT OF INTEREST:

None.

FUNDING:

The funds required for the study were provided by the researchers themselves.

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Received on 11.03.2019 Modified on 19.04.2019

Research J. Pharm. and Tech 2019; 12(8): 3899-3902.

DOI: 10.5958/0974-360X.2019.00671.1