Bacterial growth kinetic without the influence of the immune system using vacuum‐assisted closure dressing with and without negative pressure in an in vitro wound model

Abstract

The physical capacity of negative pressure wound therapy (NPWT) dressing on the bacterial growth in an in vitro wound model was investigated. Standardised wounds were contaminated with a clinical Staphylococcus aureus strain and incubated at 35 degrees C for 6 hours. Four wounds were treated with continuous negative pressure (125 mmHg) and four controls without. Bacterial load per gram tissue and per gram polyurethane sponge were measured after 24, 36 and 72 hours. Without negative pressure, the initial mean S. aureus load per gram tissue was 1.42 x 10(4), with negative pressure 1.84 x 10(4), P = 0.294. After 24, 36 and 72 hours, both models yielded comparable numbers of organisms (24 hours: P = 0.081; 48 hours: P = 0.455; 72 hours: P = 0.825, respectively). Bacterial load of sponges with or without negative pressure also did not differ. Over a period of 72 hours, sponges with negative pressure yielded 1.60 x 10(8), those without negative pressure yielded 1.74 x 10(8) CFU/g sponge (P = 0.876). In non vital tissue without the influence of the immune system, the bacterial load did not decrease in our in vitro model using an NPWT dressing. This observation was independent of the physical effect of continuous negative pressure at 125 mmHg. The reduction in bacteria demonstrated in previous studies appears to be caused by other effects than physical suction alone. However, the results obtained are limited as non viable tissue was used and the effect of suction on dead tissue might be very different from that occurring on perfused tissue, for example, in an animal model or in patients.

Influence of Antimicrobial Coatings of Vacuum-Assisted Closure Dressings on Methicillin-Resistant Staphylococcus aureus Growth Kinetics: An In Vitro Study

“…The authors concluded that in the absence of a functional host defense, physical suction alone does not reduce the bacterial load of wounds or NPWT foams [21]. These results are therefore consistent with our finding of unrestrained MRSA growth on pure polyurethane foams.…”

“…Assadian et al [21] investigated the MRSA load of tissue and uncoated foam dressing samples in an in vitro model using NPWT and porcine skeletal muscle. Irrespective of the applied suction, no significant differences in bacterial load between tissue samples and uncoated polyurethane sponges were found after a 72-h observation period.…”

“…Although the combination of physical suction and silver dressings is an established procedure in surgical site infection management, neither approach has been proved to be clearly superior to conventional dressings regarding the reduction of bacterial load and duration of incision healing [3,[21][22][23]. Mouës et al [24] quantified the bacterial load by taking repeated surgical site infection biopsies during treatment with either NPWT (n = 29) or conventional moist gauze (n = 25).…”

A retrospective study of deep sternal wound infections: clinical and microbiological characteristics, treatment, and risk factors for complications

“…Prompted by its increasing use, several studies have found the clinical effect of VAC to be comparable to traditional closed drainage or open packing, with improvement in sternal wound healing, reinfection rates, length of intensive care unit stay, and possibly mortality (Deniz et al, 2012;Risnes et al, 2012;Sjogren et al, 2005aSjogren et al, , 2005bVos et al, 2012). The effect of bacterial load with VAC, however, has had conflicting results (Assadian et al, 2010;Lalliss et al, 2010;Moues et al, 2004) with some studies showing bacterial accumulation, up to 10 4 -10 6 colonies of bacteria per gram of tissue (Weed et al, 2004;Yusuf et al, 2013). The significance of these observations remains unclear.…”

The change of wound contamination under the infl uence of local application of negative pressure

“…Во многих ис-следованиях сообщалось, что бактериальная на-грузка снижалась быстрее в ранах, обработанных отрицательным давлением, чем в тех, на кото-рые накладывались обычные марлевые повязки, пропитанные изотоническим раствором [5][6][7]. Напротив, результаты других исследований по-казывают, что бактериальная нагрузка в ране уве-личилась или оставалась довольно стабильной, хотя и с уменьшением числа грамотрицатель-ных палочек, но при этом с увеличением числа колоний Staphylococcus aureus при применении отрицательного давления [8,9]. Результаты еще одного исследования показали, что использова-ние VAC достоверно не улучшало очистку ран от микрофлоры [10].…”