Modeling microbial survival in buildup biofilm for complex medical devices

Abstract

BackgroundFlexible endoscopes undergo repeated rounds of patient-use and reprocessing. Some evidence indicates that there is an accumulation or build-up of organic material that occurs over time in endoscope channels. This "buildup biofilm" (BBF) develops as a result of cyclical exposure to wet and dry phases during usage and reprocessing. This study investigated whether the BBF matrix represents a greater challenge to disinfectant efficacy and microbial eradication than traditional biofilm (TBF), which forms when a surface is constantly bathed in fluid.MethodsUsing the MBEC (Minimum Biofilm Eradication Concentration) system, a unique modelling approach was developed to evaluate microbial survival in BBF formed by repetitive cycles of drying, disinfectant exposure and re-exposure to the test organism. This model mimics the cumulative effect of the reprocessing protocol on flexible endoscopes. Glutaraldehyde (GLUT) and accelerated hydrogen peroxide (AHP) were evaluated to assess the killing of microbes in TBF and BBF.ResultsThe data showed that the combination of an organic matrix and aldehyde disinfection quickly produced a protective BBF that facilitated high levels of organism survival. In cross-linked BBF formed under high nutrient conditions the maximum colony forming units (CFU) reached ~6 Log10 CFU/peg. However, if an oxidizing agent was used for disinfection and if organic levels were kept low, organism survival did not occur. A key finding was that once established, the microbial load of BBF formed by GLUT exposure had a faster rate of accumulation than in TBF. The rate of biofilm survival post high-level disinfection (HLD) determined by the maximum Log10CFU/initial Log10CFU for E. faecalis and P. aeruginosa in BBF was 10 and 8.6 respectively; significantly different compared to a survival rate in TBF of ~2 for each organism. Data from indirect outgrowth testing demonstrated for the first time that there is organism survival in the matrix. Both TBF and BBF had surviving organisms when GLUT was used. For AHP survival was seen less frequently in BBF than in TBF.ConclusionThis BBF model demonstrated for the first time that survival of a wide range of microorganisms does occur in BBF, with significantly more rapid outgrowth compared to TBF. This is most pronounced when GLUT is used compared to AHP. The data supports the need for meticulous cleaning of reprocessed endoscopes since the presence of organic material and microorganisms prevents effective disinfection when GLUT and AHP are used. However, cross-linking agents like GLUT are not as effective when there is BBF. The data from the MBEC model of BBF suggest that for flexible endoscopes that are repeatedly used and reprocessed, the assurance of effective high-level disinfection may decrease if BBF develops within the channels.

Is peracetic acid suitable for the cleaning step of reprocessing flexible endoscopes?

“…Biofilms composed of E. coli [152,153] , S. aureus [152,154,155] , Mycobacterium fortuitum [156] or Listeria monocytogenes [157] also resisted treatment with diverse biocides compared with planktonic cells. Bacteria in mature (old) biofilms were more resistant to killing than those in young biofilms [153,158,159] . An older biofilm of P. aeruginosa required up to 20-fold higher concentrations of peracetic acid (0.2%) to be eradicated, compared with their planktonic counterparts (0.01%) [151] .…”

Risco e segurança sanitária: análise do reprocessamento de produtos médicos em hospitais de Salvador, BA

“…The reusable articles are considered to be durable goods and their reuse requires reprocessing action, which includes cleansing, performance evaluation testing, disinfection or sterilization and quality control of all stages so as to ensure safety when using them. [1][2][3] The single-use products are designed to be used once, but the practice of reusing these materials is a worldwide reality. This tendency raises issues regarding the risks involved and the consequent lack of safety for patients, as well as in relation to the technical, regulatory, juridical, economic, ethical and environmental aspects of this practice.…”

O impacto da fricção, solução de limpeza e subsequente desinfecção de alto nível na remoção de biofilme buildup-5 e de biofilme tradicional-5 em canais endoscópicos gastrointestinais flexíveis

“…Em experimentos prévios realizados no laboratório (dados não publicados), pôde-se verificar que o acúmulo de microrganismos para a formação do BBF-5 é mais lento do que para o desenvolvimento do TBF-5. Entretanto, em condições em que a quantidade de microrganismos é a mesma, o BBF-5 pode ser mais difícil de ser removido quando comparado ao TBF-5, devido ao acúmulo cíclico de microrganismos após diversos ciclos de utilização, limpeza e exposição aos desinfetantes e secagem, que podem fixar o BBF-5 na superfície dos canais de PTFE (Alfa, Howie, 2009;e Zhong et al, 2009). …”

“…A solução deve ser descartada após cada uso (Beillenhoff et al, ESGE Guidelines Committee, 2008;ASGE;SHEA, 2011;Brasil, 2012;AAMI, 2015;AORN, 2016). Microrganismos podem replicar em solução de detergente enzimático, em temperatura ambiente (Alfa, Howie, 2009). …”

“…Enquanto o biofilme tradicional desenvolve durante uma hidratação contínua, o BBF forma após vários ciclos de exposição a secreções do paciente, limpeza, desinfecção de alto nível, enxágue e secagem. Este processo "cíclico" resulta em gradual acúmulo e fixação de material orgânico com microrganismos em seu interior (Alfa, Howie, 2009;e Zhong et al, 2009). …”