Sterilisation of some improvised suture materials for external tissue apposition

Abstract

Sir,The non-availability and low quality of most of the available suture materials in northern Nigeria has necessitated preliminary evaluation of some locally available threads to use in their stead. These include nylon rope strand, cobblers' thread, embroidery thread, nylon fishing line and hair-braiding thread, which are easily available and less costly. They have been tested as improvised sutures in dogs 1 and in rabbits. 2 Fishing line as improvised suture has been successfully used in humans. 3 The practice therefore of using improvised suture materials is gradually gaining ground in low-income economies; however, concerns remain on adequate methods of sterilisation and their duration. There is need, therefore, to evaluate and, consequently, validate the chemical (cold) sterilisation (the cheapest and easily available) method of these improvised suture materials and the time duration of effective sterilisation.We conducted a study in our Microbiology Laboratory of the Department of Public Health and Preventive Medicine, Ahmadu Bello University (Reference no ABUVMPH 20/05/ 0012). Experimental suture materials were immersed in sterilised 200 mL plastic containers filled with 70% alcohol and chlorhexidine 0.3 W/V and submerged for 30 min, 1 h, 10 and 24 h, respectively. At the end of this time interval, a swab of the sample materials was obtained and carefully put into a tube containing distilled water. Thereafter, a sample of each of the experimental materials was incubated at 37 °C for 48 h and the bacterial load was determined at the microbiology laboratory. Seven trials were carried out.It was observed that the total aerobic/coliform plate counts (105 cfu/mL) of CT, ET and HBT immersed in 70% alcohol or chlorhexidine 0.3 w/v at different time periods displayed a similar pattern. The plate counts at 0 min ranged between 15 and 38 (105 cfu/mL) and sometimes too numerous to count (TNTC) for CT, ET and HBT. Values started reducing after 30 min of immersion in 70% alcohol or 0.3 w/v of chlorhexidine and at 60 min post-immersion, the total plate count was nil (Table 1).Regardless of the type of experimental suture material, similar results were observed. We conclude that disinfection of semi-critical products with 70% alcohol and strictly observing the time period of exposure is reliable in achieving sterility. 4 It has been reported that 70% alcohol is more effective than chlorhexidine, as it produces significant growth inhibition due to its ability to coagulate and denature proteins. 5 Cold sterilisation with 70% alcohol or chlorhexidine (0.3 W/ V) for at least 1 h was likewise very effective.Further issues such as the strength of the suture, knotting strength and potential for any allergic reactions (especially after sterilisation) should be trialled before acceptance of such suture materials to be used in humans. Scientific evaluation in animal and clinical use is awaited.