Bacteria in nature often exist as sessile communities called biofilms. These communities develop structures that are morphologically and physiologically differentiated from free-living bacteria. A cell-to-cell signal is involved in the development of Pseudomonas aeruginosa biofilms. A specific signaling mutant, a lasI mutant, forms flat, undifferentiated biofilms that unlike wild-type biofilms are sensitive to the biocide sodium dodecyl sulfate. Mutant biofilms appeared normal when grown in the presence of a synthetic signal molecule. The involvement of an intercellular signal molecule in the development of P. aeruginosa biofilms suggests possible targets to control biofilm growth on catheters, in cystic fibrosis, and in other environments where P. aeruginosa biofilms are a persistent problem.

https://science.sciencemag.org/content/sci/280/5361/295.full.pdf

The involvement of cell-to-cell signals in the development of a bacterial biofilm

The issue of whether low-level tolerance to germicides selects for antibiotic-resistant strains is unsettled but might depend on the mechanism by which tolerance is attained. For example, changes in the permeability barrier or efflux mechanisms might affect susceptibility to both antibiotics and germicides, but specific changes to a target site might not. Some researchers have suggested that use of disinfectants or antiseptics (e.g., triclosan) could facilitate development of antibiotic-resistant microorganisms 334, 335, . Although evidence in laboratory studies indicates low-level resistance to triclosan, the concentrations of triclosan in these studies were low (generally <1 μg/mL) and dissimilar from the higher levels used in antimicrobial products (2,000–20,000 μg/mL) 364, . Thus, researchers can create laboratory-derived mutants that demonstrate reduced susceptibility to antiseptics or disinfectants. In some experiments, such bacteria have demonstrated reduced susceptibility to certain antibiotics . There is no evidence that using antiseptics or disinfectants selects for antibiotic-resistant organisms in nature or that such mutants survive in nature. ). In addition, the action of antibiotics and the action of disinfectants differ fundamentally. Antibiotics are selectively toxic and generally have a single target site in bacteria, thereby inhibiting a specific biosynthetic process. Germicides generally are considered nonspecific antimicrobials because of a multiplicity of toxic-effect mechanisms or target sites and are broader spectrum in the types of microorganisms against which they are effective 344, .

/pdf/guideline-for-disinfection-and-sterilization-in-healthcare-1gzqhqy6ow.pdf

Guideline for disinfection and sterilization in healthcare facilities, 2008

Disinfection, Sterilization Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008

Emerging pathogens in drinking water have become increasingly important during the decade. These include newly-recognized pathogens from fecal sources such as Cryptosporidium parvum, Campylobacter spp., and rotavirus, as well as pathogens that are able to grow in water distribution systems, like Legionella spp., mycobacteria, and aeromonads. To perform a risk analysis for the pathogens in drinking water, it is necessary to understand the ecology of these organisms. The ecology of the drinking-water distribution system has to be evaluated in detail, especially the diversity and physiological properties of water bacteria. The interactions between water bacteria and (potential) pathogens in such diverse habitats as free water and biofilms are essential for the survival or growth of hygienically relevant organisms in drinking water. Results of epidemiological studies together with ecological data are the basis for effective resource protection, water treatment, and risk assessment.

Microbiological safety of drinking water.

Biofilm formation by salmonella spp. on food contact surfaces and their sensitivity to sanitizers.

Biofilm-embedded bacteria are generally more resistant to antimicrobial agents than are planktonic bacteria. Two possible mechanisms for biofilm resistance are that the glycocalyx matrix secreted by cells in a biofilm reacts with and neutralizes the antimicrobial agent and that the matrix creates a diffusion barrier to the antimicrobial agent. This study was therefore conducted to examine the relationship between glycocalyx and enhanced povidone-iodine resistance in biofilms of Pseudomonas aeruginosa (ATCC 27853). Biofilms were generated by inoculation of polycarbonate membranes with broth-grown cells and incubation of them on the surfaces of nutrient agar plates. The quantities of glycocalyx material per cell were found not to be significantly different between biofilm and planktonic samples. Transmission electron microscopy showed that the distributions of glycocalyx material around cells differed in biofilm and in planktonic samples. Addition of alginic acid to planktonic cell suspensions resulted in a slight increase in resistance to povidone-iodine, suggesting some neutralizing interaction. However, the iodine demands created by biofilm and planktonic samples of equivalent biomass were not significantly different and, therefore, do not explain the contrast in resistance observed between biofilm and planktonic samples. Examination of the relationship between cell death and biomass detachment from the glycocalyx matrix revealed that most cell death occurred in the fraction of biomass that detached from a biofilm during treatment. The overall rate of iodine diffusion through biofilms was not different from that of planktonic cells collected on a polycarbonate membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

H C Aldrich

Papers

Relationship between glycocalyx and povidone-iodine resistance in Pseudomonas aeruginosa (ATCC 27853) biofilms.