Quantitative determination of endotoxins released by bacterial biofilms

Implications of endotoxins in wound healing: a narrative review

Bacterial toxins are thought to play a role in delayed wound healing in critically colonised and infected wounds. Endotoxins are released from Gram-negative bacteria when they are lysed by host phagocytic cells during an immune response, or by antimicrobial agents, potentially leading to a detrimental effect on the host tissues. Endotoxins can affect all aspects of the wound healing process, leading to delayed healing and contributing to wound chronicity. Release of endotoxins by bacteria can also have serious systemic effects (for example, septic shock) that can lead to high levels of patient mortality. This review summarises the role and implications on wound healing of bacterial endotoxins, describing the impact of endotoxins on the various phases of the wound healing response. There is a paucity of in vivo/clinical evidence linking endotoxins attributed to a wound (via antibiotic treatment) or their release from infecting bacteria with parameters of delayed wound healing. Future work should investigate if this link is apparent and determine the mechanism(s) by which such detrimental effects occur, offering an opportunity to identify possible treatment pathways. This paper describes the phenomenon of antimicrobial-induced endotoxin release and summarises the use of wound dressings to reduce wound bioburden without inducing microbial death and subsequent release of endotoxins, thus limiting their detrimental effects.

Analysis of the air/water channels of gastrointestinal endoscopies as a risk factor for the transmission of microorganisms among patients

BACKGROUND

For the effective reprocessing of gastrointestinal endoscopes, contaminants must be removed from the entire surface. However, these devices have long and narrow channels that can make this process difficult.

METHODS

In this cross-sectional study, the staff assigned to reprocess gastroscopes and colonoscopes in 37 services located throughout Brazil completed a questionnaire regarding reprocessing practices geared toward the channels in these devices. In addition, samples from these air/water channels were collected for microbiological analysis.

RESULTS

Contamination was detected in 71.8% (28/39) of the samples obtained from the air/water channels of colonoscopes, and in 70% (42/60) of the samples from the air/water channels of gastroscopes. The median microbial load was 1,800 colony-forming units (CFU)/mL in the colonoscopes and 750 CFU/mL in the gastroscopes. The main microorganisms isolated from the air/water channels of gastroscopes were Pseudomonas aeruginosa (26.4%), Escherichia coli (18.9%), and Acinetobacter baumannii (9.4%), and those isolated from the colonoscopes included P aeruginosa (46.4%), A baumannii (14.3%), and Klebsiella pneumoniae (10.7%), among others. The possible causes of the contamination of these devices included the failure to fill these channels with cleaning solution, lack of friction during cleansing, and inadequate rinsing.

CONCLUSION

The contamination of the air/water channels did in fact represent a risk for the transmission of microorganisms during gastrointestinal endoscopy exams, possibly related to the inadequate reprocessing of these channels.

Microbiological quality of water and dialysate in a haemodialysis unit in Ponta Grossa-PR, Brazil

AIMS

The objective of the study was to determine the microbiological quality of samples of water and dialysate in a haemodialysis unit.

METHODS AND RESULTS

Seventy-two samples each of water and dialysate were collected during November 2003 to April 2004. The following microbiological analyses were performed: test for total and faecal coliforms, which produced negative results for all the samples; counts of total heterotrophic bacteria, where three samples of water and two of dialysate showed levels higher than those permitted by national standards; and endotoxin assay, which revealed high quantities only in samples of water that preceded reverse osmosis. Nonfermenting Gram-negative bacteria were identified in 54 samples of dialysate and in 26 samples of water. The test for adhesion to an inert surface showed that various bacteria were capable of forming biofilms. Twenty-seven per cent of the bacteria were resistant to sodium hypochlorite at 500 ppm for 10-min contact time. Sixty per cent of the isolates were resistant to three or more antibiotics.

CONCLUSIONS

Water and dialysate can be a source of infection for patients who need haemodialysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

An adequate system for water treatment, disinfection of the haemodialysis system and microbiological monitoring of the water and dialysate are necessary to reduce bacteraemia and pyrogenia outbreaks.

Efficiency in endotoxin removal by a reprocessing protocol for electrophysiology catheters based on hydrogen peroxide plasma sterilization

Electrophysiology and ablation cardiac catheters, which come in contact with blood during clinical use, are required to be non-pyrogenic (<20 endotoxin units (EU)/device). This study aimed to quantify the residual endotoxin load in reprocessed devices as a mandatory step to guarantee safe reuse. We monitored the pyrogenic status of the device (n=61) in three fundamental steps of the reprocessing protocol: after clinical use, after decontamination-cleaning treatments and after complete reprocessing, including sterilization by hydrogen peroxide gas plasma. Finally, a depyrogenation test was produced for evaluating the depyrogenation efficiency of the sole hydrogen peroxide sterilization treatment. Results showed that standard clinical use did not represent a source for endotoxin contamination, while the use of tap water and manual cleaning processing could increase the pyrogenic load in a significant way. The introduction of the sterilization by hydrogen peroxide gas plasma resulted in effective reduction of the endotoxin contamination and in safe reprocessing of 15 of 15 clinically used catheters. In addition, tests conducted on in vitro spiked catheters showed that initial pyrogenic loads of 40, 80, 200EU/device were reduced to less than 11EU/device. Depyrogenation testing demonstrated efficiency in endotoxin reduction of more than 62 times (1.8log). These results show the determining role of hydrogen peroxide gas-plasma sterilization in the reduction of pyrogenic load on medical devices. Considering actual hygienic requirements at single-use device reprocessing, hydrogen peroxide gas-plasma sterilization can be considered as an efficient treatment at non-lumen cardiac electrophysiology catheter reprocessing.

Detection of icaA and icaD loci by polymerase chain reaction and biofilm formation by Staphylococcus epidermidis isolated from dialysate and needles in a dialysis unit

Staphylococcus epidermidis, a coagulase-negative staphylococcus, is a major cause of infections associated with indwelling medical devices. Certain strains produce slime and form biofilm on polymer surfaces, where their pathogenicity is associated with biofilm formation. In this report, we investigated the presence or absence of the intercellular adhesion icaA and icaD genes by polymerase chain reaction, and phenotypic biofilm production was examined by qualitative Congo red agar (CRA) assay. A total of 32 strains of S. epidermidis were identified from dialysates and needles 4h after the initiation of dialysis. Qualitative biofilm production revealed that 16 (50%) strains produced slime on CRA plates. Among the 23 strains positive for the ica operon, 15 were biofilm positive on CRA, eight were biofilm negative, and one was icaA and icaD negative but produced slime. These results show that the ability of S. epidermidis to produce slime is not associated with the presence of icaA and icaD genes.

Bacterial Biofilms and Ocular Infections

Serious bacterial infections of the eye are often associated with abiotic prosthetic materials, such as contact lenses, intraocular lenses, and scleral buckles. In recent years, microbiologists have recognized substantial differences between bacteria growing in a sessile community attached to a surface and free-living or planktonic bacteria. These sessile surface-attached communities are known as biofilms, whose properties have important consequences for clinical medicine. As a population, bacteria in biofilms are more resistant to antimicrobial agents and the immune system, and they are more persistent than planktonic bacteria in hostile environments. These characteristics are likely the result of both biofilm-specific phenotypes and increased phenotypic diversity within biofilms as compared with planktonic communities of bacteria. Bacterial biofilm formation has been observed on human tissues, as well as on abiotic prosthetic devices. A better understanding of biofilm formation may lead to the development of novel antimicrobial agents as well as prosthetic devices that are resistant to bacterial colonization.

Lipopolysaccharide concentration and bone resorption in cholesteatoma

HYPOTHESIS

There is a relationship between the local lipopolysaccharide (LPS) concentration in cholesteatoma and local bone resorption in chronic otitis media (COM) with cholesteatoma.

BACKGROUND

During the past decade, it has become known that the recruitment of osteoclasts is the main causative factor that induces bone destruction in COM with cholesteatoma. Cellular inflammation factors like cytokines may trigger the osteoclast. Sequel to this, LPS is able to up-regulate cytokines. This makes it of interest to study whether the local LPS concentration is related to bone resorption in cholesteatoma.

MATERIALS AND METHODS

Twenty-four cholesteatoma samples and control tissue from COM patients without cholesteatoma were collected. During surgery, the degree of bone resorption was established and classified. Retrospectively, the authors checked whether patients had chronic purulent otorrhea. LPS concentration of the tissue samples was measured by the limulus amebocyte lysate test. The one-way analysis of variance test was used to determine the relation between LPS concentration, otorrhea, and local bone resorption.

RESULTS

A significantly higher concentration of LPS was measured in samples from patients with cholesteatoma with bone resorption and otorrhea compared with cholesteatoma without bone resorption and control tissue. There were no significant differences between the LPS levels of the different groups of patients with bone resorption.

CONCLUSION

It is suggested that LPS is one of the first factors in the cascade of bone resorption in COM with cholesteatoma.

Colonization of hospital water systems by legionellae, mycobacteria and other heterotrophic bacteria potentially hazardous to risk group patients

Occurrences of legionellae and nontuberculous mycobacteria were followed in water systems of a tertiary care hospital where nosocomial infections due to the two genera had been verified. The aim was to examine whether their occurrence in the circulating hot water can be controlled by addition of a heat-shock unit in the circulation system, and by intensified cleaning of the tap and shower heads. One hot water system examined had an inbuilt heat-shock system causing a temporary increase of temperature to 80 degrees C, the other was an ordinary system (60 degrees C). The heat-shock unit decreased legionella colony counts in the circulating hot water (mean 35 cfu/l) compared to the ordinary system (mean 3.6 x 10(3) cfu/l). Mycobacteria constantly present in the incoming cold water (mean 260 cfu/l) were never isolated from the circulating hot water. Water sampled at peripheral sites such as taps and showers contained higher concentrations of legionellae, mycobacteria, and mesophilic and Gram-negative heterotrophs than the circulating waters. The shower water samples contained the highest bacterial loads. The results indicate the need to develop more efficient prevention methods than the ones presently used. Prevention of mycobacteria should also be extended to incoming cold water.

Biofilms: microbial life on surfaces

Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.

A survey of reprocessing methods, residual viable bioburden, and soil levels in patient-ready endoscopic retrograde choliangiopancreatography duodenoscopes used in Canadian centers

OBJECTIVES

To obtain information about current reprocessing practices and to obtain samples from the biopsy channel to quantitate soil levels and bioburden in patient-ready flexible duodenoscopes used for endoscopic retrograde choliangiopancreatography (ERCP).

DESIGN

Participating centers were sent a questionnaire and a kit for on-site collection of samples from the biopsy channel of the duodenoscope.

SETTING

Thirty-seven hospitals from across Canada participated. The only criterion was that they currently used and reprocessed flexible duodenoscopes for ERCP procedures.

METHODS

The questionnaire obtained information on reprocessing practices. The kit included a detailed instruction booklet outlining sample collection and all of the tubes, sterile water, and brushes needed for it. Samples were collected on-site from all ERCP scopes in each center on Monday morning and shipped by overnight courier on ice to the research center. Each sample was assayed by routine microbiologic methods for total viable count and protein, blood, carbohydrate, and endotoxin levels.

RESULTS

Microbial overgrowth was present in 7% of 119 scope samples. Cleaning appeared to be reasonably well done in most of the centers, and 43% of the centers were in total compliance with basic national guidelines. The data from the scope samples indicated that there was significantly greater buildup of protein, carbohydrate, and endotoxin associated with ERCP scopes from centers using glutaraldehyde, compared with those using peracetic acid. Carbohydrate was the soil component detected most frequently and in the highest concentration in scope channels.

CONCLUSIONS

Although cleaning was generally well done, areas for improvement included ensuring the availability of written reprocessing protocols, immersion of scopes during manual cleaning, use of adequate fluid volume for rinsing, adequate drying of scopes prior to storage, and the separation of ERCP valves from scopes during storage.

Biofilms: survival mechanisms of clinically relevant microorganisms

Though biofilms were first described by Antonie van Leeuwenhoek, the theory describing the biofilm process was not developed until 1978. We now understand that biofilms are universal, occurring in aquatic and industrial water systems as well as a large number of environments and medical devices relevant for public health. Using tools such as the scanning electron microscope and, more recently, the confocal laser scanning microscope, biofilm researchers now understand that biofilms are not unstructured, homogeneous deposits of cells and accumulated slime, but complex communities of surface-associated cells enclosed in a polymer matrix containing open water channels. Further studies have shown that the biofilm phenotype can be described in terms of the genes expressed by biofilm-associated cells. Microorganisms growing in a biofilm are highly resistant to antimicrobial agents by one or more mechanisms. Biofilm-associated microorganisms have been shown to be associated with several human diseases, such as native valve endocarditis and cystic fibrosis, and to colonize a wide variety of medical devices. Though epidemiologic evidence points to biofilms as a source of several infectious diseases, the exact mechanisms by which biofilm-associated microorganisms elicit disease are poorly understood. Detachment of cells or cell aggregates, production of endotoxin, increased resistance to the host immune system, and provision of a niche for the generation of resistant organisms are all biofilm processes which could initiate the disease process. Effective strategies to prevent or control biofilms on medical devices must take into consideration the unique and tenacious nature of biofilms. Current intervention strategies are designed to prevent initial device colonization, minimize microbial cell attachment to the device, penetrate the biofilm matrix and kill the associated cells, or remove the device from the patient. In the future, treatments may be based on inhibition of genes involved in cell attachment and biofilm formation.

Endotoxin Levels in Steam and Reservoirs of Table-top Steam Sterilizers

PURPOSE

To document endotoxin levels in "Statim" cassette sterilizer reservoirs and in steam delivered to the cassette in the unwrapped instrument cycle. To document endotoxin levels in sterilizer reservoir water using different management protocols.

METHODS

Endotoxin levels were determined using the Limulus Amebocyte Lysate test. Endotoxin preparations were from Escherichia coli and Ralstonia pickettii. All samples were collected in depyrogenated glassware and stored at -20 degrees C until assayed.

RESULTS

The majority of water samples contained < 1.0 Endotoxin Unit (EU)/ml. The highest level found in sterilizers in clinical use was 5.3 EU/ml. Endotoxin was not detected in steam condensate within the limits of the assay. When the endotoxin level in the reservoir water was experimentally enhanced to 200 EU/ml, cassette steam condensate endotoxin levels were from 0.5% to 5% of the reservoir level. Daily and weekly emptying of the cassette reservoir consistently yielded low endotoxin levels as did monthly emptying, but with the latter there was a trend toward higher levels that favors weekly emptying as a precautionary measure.

CONCLUSIONS

Endotoxin levels in the reservoirs of 23 sterilizers involving 240 samplings were never high enough to yield detectable endotoxin levels in steam in the sterilizer cassette. Regular weekly emptying of sterilizer reservoirs would eliminate the risk of endotoxin transfer during steam sterilization.