The survival of multi-drug resistant bacteria on raw Douglas fir material

In today's age of ecological transition, the use of materials such as renewable wood in construction is particularly relevant, but also a challenge in the healthcare sector where the hygiene dimension also comes into play. In this study we have investigated the survival of multi-resistant bacteria commonly responsible for healthcare-associated infections (HAIs) (ESBL-positive Klebsiella pneumoniae and glycopeptide-resistant Enterococcus faecalis) on two different types of wood (Douglas fir : Pseudotsuga menziesii and Maritime Pine : Pinus pinaster) compared to other materials (smooth: stainless steel and rough: pumice stone) and the effect of a disinfection protocol on the bacterial survival on Pseudotsuga menziesii. Approximately 108 bacteria were inoculated on each material and bacterial survival was observed over several days (D0, D1, D2, D3, D6, D7 and D15). Each analysis was performed in triplicate for each time and material. The results show an important reduction of the bacterial inoculum for Klebsiella pneumoniae and Enterococcus faecalis on Douglas fir, in contrast with the results obtained on maritime pine, stainless steel and pumice stone. No bacterial survival was detected on Douglas fir after application of a hospital disinfection protocol. These different results show that wood may have a place in the future of healthcare construction. Further studies would be interesting to better understand the different properties of wood.

Confocal spectral microscopy, a non-destructive approach to follow contamination and biofilm formation of mCherry Staphylococcus aureus on solid surfaces

Methods to test the safety of wood material for hygienically sensitive places are indirect, destructive and limited to incomplete microbial recovery via swabbing, brushing and elution-based techniques. Therefore, we chose mCherry Staphylococcus aureus as a model bacterium for solid and porous surface contamination. Confocal spectral laser microscope (CSLM) was employed to characterize and use the autofluorescence of Sessile oak (Quercus petraea), Douglas fir (Pseudotsuga menziesii) and poplar (Populus euramericana alba L.) wood discs cut into transversal (RT) and tangential (LT) planes. The red fluorescent area occupied by bacteria was differentiated from that of wood, which represented the bacterial quantification, survival and bio-distribution on surfaces from one hour to one week after inoculation. More bacteria were present near the surface on LT face wood as compared to RT and they persisted throughout the study period. Furthermore, this innovative methodology identified that S. aureus formed a dense biofilm on melamine but not on oak wood in similar inoculation and growth conditions. Conclusively, the endogenous fluorescence of materials and the model bacterium permitted direct quantification of surface contamination by using CSLM and it is a promising tool for hygienic safety evaluation.

Wood materials for limiting the bacterial reservoir on surfaces in hospitals: would it be worthwhile to go further?

Aim: To assess the activity of Quercus petraea (oak) on five bacterial species/genus frequently involved in hospital-acquired infections for evaluating the interest of going further in exploring the possibilities of using untreated wood as a material in the hospital setting. Materials & methods: We studied the activity of Q. petraea by the disk diffusion method. Results: Q. petraea was active on Staphylococcus aureus and Acinetobacter coalcoaceticus-baumannii complex, two bacterial species particularly resistant in the hospital environment, independently from their resistance to antibiotics, and was slightly active on Pseudomonas aeruginosa. Concurrently, Q. petraea was not active on Enterococci and Escherichia coli. Conclusion: Overall, untreated wood material presented antimicrobial properties that could have an impact on the cross-transmission of certain bacterial species in healthcare settings.

Experimental Parameters Influence the Observed Antimicrobial Response of Oak Wood (Quercus petraea)

The present investigation aimed to utilize a direct wood disc diffusion method to study the influence of plane of cutting, cutting method, sterilization method, and origin of tree on the antimicrobial activity of wood material. Six oak wood trees (Quercus petraea) were collected from 3 different locations in France. They were cut into 4 mm thick slices with either transverse (RT), tangential (LT) or radial (LR) faces. Round discs (diameter 9.95 ± 0.1 mm) were cut from the slices via a laser machine or a manual punch machine, and were sterilized with gamma irradiation (25 kGy) or autoclaving (121 °C). The antimicrobial activity of wood was tested using a direct diffusion method against Staphylococcus aureus and Acinetobacter baumannii isolates. The zone of inhibition around the wooden disc was recorded following the recommendations used for antibiotics tests. The results showed that S. aureus was more susceptible than A. baumannii, to the chemicals that diffused from the wood. The transverse face discs exhibited higher antimicrobial activity. Samples that had been sterilized by autoclaving showed significantly (p < 0.05) lower antimicrobial activity, whereas the cutting method and origin of tree did not influence the antimicrobial activity of wood material. Therefore, the choice of sterilization method and cutting planes must be taken into account while studying and interpreting the antibacterial properties of wood material.

Testing the Antimicrobial Characteristics of Wood Materials: A Review of Methods

Some wood species have antimicrobial properties, making them a better choice over inert surfaces in certain circumstances. However, the organic and porous nature of wood raises questions regarding the use of this material in hygienically important places. Therefore, it is reasonable to investigate the microbial survival and the antimicrobial potential of wood via a variety of methods. Based on the available literature, this review classifies previously used methods into two broad categories: one category tests wood material by direct bacterial contact, and the other tests the action of molecules previously extracted from wood on bacteria and fungi. This article discusses the suitability of these methods to wood materials and exposes knowledge gaps that can be used to guide future research. This information is intended to help the researchers and field experts to select suitable methods for testing the hygienic safety and antimicrobial properties of wood materials.

Waterborne Leptospirosis: Survival and Preservation of the Virulence of Pathogenic Leptospira spp. in Fresh Water

Many studies have implicated fresh water as a source of leptospirosis outbreaks. To estimate the survival and the preservation of the virulence of pathogenic Leptospira spp. maintained in water, we selected five still waters with various pH and mineral profiles. The water samples were artificially inoculated with a culture of a pathogenic strain belonging to serovar Icterohaemorrhagiae. Samples were stored for 20 months at 4, 20 or 30 °C. The survival and preservation of virulence of this pathogenic strain was estimated by subculturing these stored samples. After 14 and 20 months of storage, the strain Icterohaemorrhagiae was re-isolated, and its virulence was determined using an animal model. In these waters, the mean survival was 130 days for storage at 4 °C, 263 days at 20 °C, and 316 days at 30 °C. Unexpectedly, the mean survival was 344 days for a final pH < 7 and 129 days for pH ≥ 7. Moreover, the pathogenic strain remained fully virulent and was able to induce a lethal disease in gerbils even when the pH of the contaminated waters decreased to <6. These data showed that despite unfavourable storage conditions such as cold, nutrient-poor acidic waters, the survival and virulence of pathogenic Leptospira spp. was fully preserved over at least 20 months.

Methods for recovering microorganisms from solid surfaces used in the food industry: a review of the literature

Various types of surfaces are used today in the food industry, such as plastic, stainless steel, glass, and wood. These surfaces are subject to contamination by microorganisms responsible for the cross-contamination of food by contact with working surfaces. The HACCP-based processes are now widely used for the control of microbial hazards to prevent food safety issues. This preventive approach has resulted in the use of microbiological analyses of surfaces as one of the tools to control the hygiene of products. A method of recovering microorganisms from different solid surfaces is necessary as a means of health prevention. No regulation exists for surface microbial contamination, but food companies tend to establish technical specifications to add value to their products and limit contamination risks. The aim of this review is to present the most frequently used methods: swabbing, friction or scrubbing, printing, rinsing or immersion, sonication and scraping or grinding and describe their advantages and drawbacks. The choice of the recovery method has to be suitable for the type and size of the surface tested for microbiological analysis. Today, quick and cheap methods have to be standardized and especially easy to perform in the field.

Expanding the genetic toolbox for Leptospira species by generation of fluorescent bacteria

Our knowledge of the genetics and molecular basis of the pathogenesis associated with Leptospira, in comparison to those of other bacterial species, is very limited. An improved understanding of pathogenic mechanisms requires reliable genetic tools for functional genetic analysis. Here, we report the expression of gfp and mRFP1 genes under the control of constitutive spirochetal promoters in both saprophytic and pathogenic Leptospira strains. We were able to reliably measure the fluorescence of Leptospira by fluorescence microscopy and a fluorometric microplate reader-based assay. We showed that the expression of the gfp gene had no significant effects on growth in vivo and pathogenicity in L. interrogans. We constructed an expression vector for L. biflexa that contains the lacI repressor, an inducible lac promoter, and gfp as the reporter, demonstrating that the lac system is functional in Leptospira. Green fluorescent protein (GFP) expression was induced by the addition of isopropyl-β-d-thiogalactopyranoside (IPTG) in L. biflexa transformants harboring the expression vector. Finally, we showed that GFP can be used as a reporter to assess promoter activity in different environmental conditions. These results may facilitate further advances for studying the genetics of Leptospira spp.

Use of quantitative real-time PCR for studying the dissemination of Leptospira interrogans in the guinea pig infection model of leptospirosis

The dynamics of leptospirosis infection have been poorly studied. The purpose of this study was to determine the LD50, rate of bacterial dissemination, histopathology and antibody responses against leptospira following inoculation with the highly virulent Leptospira interrogans Fiocruz L1-130 strain in a guinea pig model of leptospirosis. Three routes of infection (intraperitoneal, conjunctival and subcutaneous inoculation) were used to establish disease in guinea pigs. The size and kinetics of leptospiral burdens in the blood and tissues of infected animals were determined over a 1 week course of infection using quantitative real-time PCR (qPCR). Bacteraemia peaked at day 5 post-infection reaching more than 5×104 leptospires ml−1. The highest spirochaetal load was found in the liver and kidneys, and was associated with alterations in organ tissues and a decline in liver and kidney functions. In contrast, lesions and bacteria were not detected in guinea pigs infected with an avirulent strain derived from a high-passage-number in vitro-passaged variant of the Fiocruz L1-130 strain. The use of qPCR supports the findings of earlier studies and provides an easy and reliable method for the quantification of L. interrogans in the tissues of infected animals. qPCR will be used in future studies to evaluate the efficacy of vaccine candidates against leptospirosis and the virulence of selected L. interrogans mutants relative to the parental strain.

Protection against Leptospira interrogans sensu lato challenge by DNA immunization with the gene encoding hemolysin-associated protein 1

The use of DNA constructs encoding leptospiral proteins is a promising new approach for vaccination against leptospirosis. In previous work we determined that immunization with hemolysis-associated protein 1 (Hap1) (LipL32) expressed by adenovirus induced significant protection against a virulent Leptospira challenge in gerbils. To avoid the use of the adenovirus vector, we checked for clinical protection against lethal challenge by DNA vaccination. A DNA vaccine expressing Hap1 was designed to enhance the direct gene transfer of this protein into gerbils. A challenge was performed 3 weeks after the last immunization with a virulent strain of serovar canicola. Our results show that the cross-protective effect with pathogenic strains of Leptospira, shared by Hap1, could be mediated by the DNA plasmid vector. This finding should facilitate the design and development of a new generation of vaccines against bacteria, particularly Leptospira interrogans sensu lato.

Polymerase chain reaction assay specific for pathogenic Leptospira based on the gene hap1 encoding the hemolysis-associated protein-1

In this study, we used Southern hybridization of genomic DNA with the integral hap1 gene as a probe to show that this gene is only present in pathogenic Leptospira strains. We then selected PCR primers based on the hap1 gene, and tested them on several Leptospira strains and biological samples. Specific amplification was obtained for all pathogenic strains tested. Negative PCR results were observed with all saprophytic leptospire strains used as well as with other spirochetes and bacteria commonly found in biological samples. The results of direct PCR performed on biological samples, such as blood, urine or kidneys correlated with the results obtained with the classical Leptospira tests (culture and MAT). A PCR assay based on this gene would be a very useful tool for the rapid, sensitive and specific identification of pathogenic leptospires in samples for diagnosis or epidemiological survey.