According to a public announcement by the US National Institutes of Health
 , “Biofilms are medically important, accounting for over 80% of microbial infections in the body”. Yet bacterial biofilms remain poorly understood and strategies for their control remain underdeveloped. Standard antimicrobial treatments typically fail to eradicate biofilms, which can result in chronic infection and the need for surgical removal of afflicted areas. The need to create effective therapies to counter biofilm infections presents one of the most pressing challenges in anti-bacterial drug development. In this article, the mechanisms that underlie biofilm resistance to antimicrobial chemotherapy will be examined, with particular attention being given to potential avenues for the effective treatment of biofilms.

/pdf/understanding-biofilm-resistance-to-antibacterial-agents-pnlgfboaq5.pdf

Understanding biofilm resistance to antibacterial agents.

The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories.

Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci.

Bacterial adhesion has become a significant problem in industry and in the domicile, and much research has been done for deeper understanding of the processes involved. A generic biological model of bacterial adhesion and population growth called the bacterial biofilm growth cycle, has been described and modified many times. The biofilm growth cycle encompasses bacterial adhesion at all levels, starting with the initial physical attraction of bacteria to a substrate, and ending with the eventual liberation of cell clusters from the biofilm matrix. When describing bacterial adhesion one is simply describing one or more stages of biofilm development, neglecting the fact that the population may not reach maturity. This article provides an overview of bacterial adhesion, cites examples of how bacterial adhesion affects industry and summarises methods and instrumentation used to improve our understanding of the adhesive properties of bacteria.

/pdf/bacterial-adhesion-and-biofilms-on-surfaces-153vag9bcp.pdf

Bacterial adhesion and biofilms on surfaces

The incidence of infections caused by Candida species (candidosis) has increased considerably over the past three decades, mainly due to the rise of the AIDS epidemic, an increasingly aged population, higher numbers of immunocompromised patients and the more widespread use of indwelling medical devices. Candida albicans is the main cause of candidosis; however, non-C. albicans Candida (NCAC) species such as Candida glabrata, Candida tropicalis and Candida parapsilosis are now frequently identified as human pathogens. The apparent increased emergence of these species as human pathogens can be attributed to improved identification methods and also associated with the degree of diseases of the patients, the interventions that they were subjected and the drugs used. Candida pathogenicity is facilitated by a number of virulence factors, most importantly adherence to host surfaces including medical devices, biofilm formation and secretion of hydrolytic enzymes (e.g. proteases, phospholipases and haemolysins). Furthermore, despite extensive research to identify pathogenic factors in fungi, particularly in C. albicans, relatively little is known about NCAC species. This review provides information on the current state of knowledge on the biology, identification, epidemiology, pathogenicity and antifungal resistance of C. glabrata, C. parapsilosis and C. tropicalis.

Candida glabrata, Candida parapsilosis and Candida tropicalis: biology, epidemiology, pathogenicity and antifungal resistance

Summary: Candida parapsilosis is an emerging major human pathogen that has dramatically increased in significance and prevalence over the past 2 decades, such that C. parapsilosis is now one of the leading causes of invasive candidal disease. Individuals at the highest risk for severe infection include neonates and patients in intensive care units. C. parapsilosis infections are especially associated with hyperalimentation solutions, prosthetic devices, and indwelling catheters, as well as the nosocomial spread of disease through the hands of health care workers. Factors involved in disease pathogenesis include the secretion of hydrolytic enzymes, adhesion to prosthetics, and biofilm formation. New molecular genetic tools are providing additional and much-needed information regarding C. parapsilosis virulence. The emerging information will provide a deeper understanding of C. parapsilosis pathogenesis and facilitate the development of new therapeutic approaches for treating C. parapsilosis infections.

Candida parapsilosis, an Emerging Fungal Pathogen

The influence of surface topography on bacterial adhesion has been investigated using a range of spatially organized microtopographic surface patterns generated on polydimethylsiloxane (PDMS) and three unrelated bacterial strains. The results presented indicate that bacterial cells actively choose their position to settle, differentiating upper and lower areas in all the surface patterns evaluated. Such selective adhesion depends on the cells’ size and shape relative to the dimensions of the surface topographical features and surface hydrophobicity/hydrophilicity. Moreover, it was found that all the topographies investigated provoke a significant reduction in bacterial adhesion (30–45%) relative to the smooth control samples regardless of surface hydrophobicity/hydrophilicity. This remarkable finding constitutes a general phenomenon, occurring in both Gram-positive and Gram-negative cells with spherical or rod shape, dictated by only surface topography. Collectively, the results presented in this study de...

Studying the influence of surface topography on bacterial adhesion using spatially organized microtopographic surface patterns.

The influence of various concentrations (0.003-8 mg/mL) of N-acetylcysteine on the formation of biofilms by 15 strains of Staphylococcus epidermidis has been studied. A dose-related decrease in biofilm formation was observed, except with the lowest concentrations. The 'slime' index relative to the control was 63%, 55%, 46%, 34%, 26% and 26% in the presence of 0.25, 0.5, 1, 2, 4, and 8 mg/mL of N-acetylcysteine, respectively. These data are statistically significant. The inhibitory effect of 2 mg/mL of N-acetylcysteine on slime formation was also verified by electron microscopy.

Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis.

C. P EREZ-GIRALDO, G. C RUZ-VILLALON, R. S ANCHEZ-SILOS, R. M ARTINEZ-RUBIO, M.T. B LANCO A ND A.C. G OMEZ-GARCIA . 2003. Aims: The aim of this study is to determine the in vitro activity of allicin against Staphylococcus epidermidis and to evaluate the influence of allicin on biofilm formation. Methods and Results: In vitro activity of allicin (diallyl thiosulphinate) against 38 strains of S. epidermidis was investigated. The activity of allicin was similar against S. epidermidis methicillin susceptible and methicillin resistant strains (minimum inhibitory concentration (MIC)90 ¼ 8m g l )1 ). In general, subinhibitory concentrations (sub- MIC) of allicin diminished biofilm formation in the five strains analysed. Conclusion: The results confirm the antibacterial effect of allicin. Sub-MICs of allicin also diminished the biofilm formations by S. epidermidis. Significance and Impact of the Study: The present study shows that allicin is active in vitro against S. epidermidis and that sub-MICs of allicin may play a role in the prevention of adherence of this bacteria to medical devices.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2003.02030.x

In vitro activity of allicin against Staphylococcus epidermidis and influence of subinhibitory concentrations on biofilm formation

The purpose of this work was to study the adhesion to polystyrene of two Candida parapsilosis strains, grown at 22 and 37°C, in terms of hydrophobicity, surface charge, and interaction free energy. Growth temperature changed the surface properties of microorganisms, yielding a good correlation between thermodynamic predictions and adhesion behavior.

Thermodynamic Analysis of Growth Temperature Dependence in the Adhesion of Candida parapsilosis to Polystyrene

Secretion of hydrolytic enzymes is considered a virulence factor in Candida spp. Extracellular enzymatic activities in 29 clinical isolates of Candida tropicalis were analyzed by plate assays. C. tropicalis, similar to Candida albicans, showed elevated hemolytic and esterase activities. However, unlike C. albicans, low aspartyl protease and very low phospholipase activities were detected in C. tropicalis isolates.

/pdf/enzymatic-activities-of-candida-tropicalis-isolated-from-2ycwmbhvdd.pdf

A. C. Gómez-García

Papers

Studying the influence of surface topography on bacterial adhesion using spatially organized microtopographic surface patterns.

Influence of N-acetylcysteine on the formation of biofilm by Staphylococcus epidermidis.

In vitro activity of allicin against Staphylococcus epidermidis and influence of subinhibitory concentrations on biofilm formation

Thermodynamic Analysis of Growth Temperature Dependence in the Adhesion of Candida parapsilosis to Polystyrene

Enzymatic activities of Candida tropicalis isolated from hospitalized patients.