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.

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Biofilms: microbial life on surfaces.

Many microorganisms, especially bacteria, produce biosurfactants when grown on water-immiscible substrates. Biosurfactants are more effective, selective, environmentally friendly, and stable than many synthetic surfactants. Most common biosurfactants are glycolipids in which carbohydrates are attached to a long-chain aliphatic acid, while others, like lipopeptides, lipoproteins, and heteropolysaccharides, are more complex. Rapid and reliable methods for screening and selection of biosurfactant-producing microorganisms and evaluation of their activity have been developed. Genes involved in rhamnolipid synthesis (rhlAB) and regulation (rhlI and rhlR) in Pseudomonas aeruginosa are characterized, and expression of rhlAB in heterologous hosts is discussed. Genes for surfactin production (sfp, srfA, and comA) in Bacillus spp. are also characterized. Fermentative production of biosurfactants depends primarily on the microbial strain, source of carbon and nitrogen, pH, temperature, and concentration of oxygen and metal ions. Addition of water-immiscible substrates to media and nitrogen and iron limitations in the media result in an overproduction of some biosurfactants. Other important advances are the use of water-soluble substrates and agroindustrial wastes for production, development of continuous recovery processes, and production through biotransformation. Commercialization of biosurfactants in the cosmetic, food, health care, pulp- and paper-processing, coal, ceramic, and metal industries has been proposed. However, the most promising applications are cleaning of oil-contaminated tankers, oil spill management, transportation of heavy crude oil, enhanced oil recovery, recovery of crude oil from sludge, and bioremediation of sites contaminated with hydrocarbons, heavy metals, and other pollutants. Perspectives for future research and applications are also discussed.

Microbial production of surfactants and their commercial potential.

INTRODUCTION 149 TAXONOMY 149 Historical Features 149 Current Taxonomic Status 149 Delineation of Species 149 Species of Clinical Importance 150 LABORATORY IDENTIFICATION 150 Isolation from Clinical Specimens 150 Morphological, Cultural, and Metabolic Characteristics 151 Species Identification 151 NOSOCOMIAL INFECTIONS CAUSED BY ACINETOBACTER SPP. 152 Overview 152 Respiratory Infection 152 Bacteremia 153 Meningitis 153 Urinary Tract Infection 154 Other Miscellaneous Infections 154 PATHOGENESIS OF ACINETOBACTER INFECTIONS 154 Predisposing Factors 154 Virulence of Acinetobacter spp. 154 EPIDEMIOLOGY 155 Human Carriage 155 Persistence in the Hospital Environment 155 TYPING SYSTEMS 156 Biotyping 156 Antibiograms 156 Serotyping 156 Phage Typing 157 Bacteriocin Typing 157 Protein Profiles 157 Multilocus Enzyme Electrophoretic Typing 157 Plasmid Profiles 157 Analysis by Pulsed-Field Gel Electrophoresis 157 Ribotyping 157 PCR-Based Methods 158 CLINICAL ANTIBIOTIC RESISTANCE 158 BIOCHEMICAL AND GENETIC MECHANISMS OF ANTIBIOTIC RESISTANCE 158 Genetics of Resistance 158 b-Lactams 159 Aminoglycosides 159 Quinolones 160 Other Antibiotics 160 THERAPY OF ACINETOBACTER INFECTIONS 160 CONCLUSIONS 160 ACKNOWLEDGMENTS 161 REFERENCES 161

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Acinetobacter spp. as nosocomial pathogens: microbiological, clinical, and epidemiological features.

Surfactants are surface-active compounds capable of reducing surface and interfacial tension at the interfaces between liquids, solids and gases, thereby allowing them to mix or disperse readily as emulsions in water or other liquids. The enormous market demand for surfactants is currently met by numerous synthetic, mainly petroleum-based, chemical surfactants. These compounds are usually toxic to the environment and non-biodegradable. They may bio-accumulate and their production, processes and by-products can be environmentally hazardous. Tightening environmental regulations and increasing awareness for the need to protect the ecosystem have effectively resulted in an increasing interest in biosurfactants as possible alternatives to chemical surfactants. Biosurfactants are amphiphilic compounds of microbial origin with considerable potential in commercial applications within various industries. They have advantages over their chemical counterparts in biodegradability and effectiveness at extreme temperature or pH and in having lower toxicity. Biosurfactants are beginning to acquire a status as potential performance-effective molecules in various fields. At present biosurfactants are mainly used in studies on enhanced oil recovery and hydrocarbon bioremediation. The solubilization and emulsification of toxic chemicals by biosurfactants have also been reported. Biosurfactants also have potential applications in agriculture, cosmetics, pharmaceuticals, detergents, personal care products, food processing, textile manufacturing, laundry supplies, metal treatment and processing, pulp and paper processing and paint industries. Their uses and potential commercial applications in these fields are reviewed.

Potential commercial applications of microbial surfactants.

Research and development of antimicrobial materials for food applications such as packaging and other food contact surfaces is expected to grow in the next decade with the advent of new polymer materials and antimicrobials. This article reviews the different types of antimicrobial polymers developed for food contact, commercial applications, testing methods, regulations and future trends. Special emphasis will be on the advantages/disadvantages of each technology.

Review of antimicrobial food packaging

Bad breath, diagnosis and treatment.

The aim of the present study was to determine whether oral malodour and periodontal disease parameters are associated with one another in 71 Israeli subjects (mean age 36.2 ± 18.4; ages ranging from 15 to 65). Parameters measured included whole mouth odour judge scoring, Halimeter, OK to Kiss test, gingival index, plaque index and probing depth. Odour judge scores were significantly associated with Halimeter® (r = 0.55; P < 0.001), as well as the OK to Kiss test (r = 0.52; P < 0.001). However, neither gingival index, plaque index nor probing depth was significantly associated with odour judge scores or Halimeter® scores. Logistic regression analysis showed that both Halimeter® and OK to Kiss scores factored significantly (P = 0.005 and 0.018, respectively, odds ratios 14.9 and 2.7, respectively) in predicting the severity of oral malodour. Results suggest that in the population studied, periodontal health and oral malodour are not associated with one another.

Association between oral malodour and periodontal disease‐related parameters in a population of 71 Israelis

Global gene expression in Staphylococcus aureus following exposure to alcohol.

Interbacterial adhesion (coadhesion) is considered a major determinant of dental plaque ecology In this report, we studied several aspects of the adhesion of Porphyromonas (Bacteroides) gingivalis to hexadecane in order to use the liquid hydrocarbon as a convenient substratum for coadhesion assays Washed suspensions of hydrophobic P gingivalis 2561 cells were vortexed with hexadecane to yield highly stable cell-coated droplets Kinetics of coadhesion between Actinomyces viscosus cells and P gingivalis-coated hexadecane droplets (PCHD) was subsequently studied Aliquots of PCHD were added to A viscosus suspensions, and the mixtures were gently rotated Avid adhesion of A viscosus cells to the immobilized P gingivalis layer could be readily measured by the decrease in turbidity in the aqueous phase, following phase separation Despite the ability of A viscosus cells to adsorb to hexadecane following vigorous mixing, gentle mixing did not appreciably promote adhesion to bare hexadecane Moreover, extensive microscopic examinations revealed that A viscosus cells adhered exclusively to the bound P gingivalis cells rather than to exposed areas of hexadecane Coadhesion of A viscosus to the PCHD appeared to follow first-order kinetics, attaining 80% levels within 30 min Electron micrographs revealed A viscosus cells adhering to the P gingivalis cell layer adsorbed at the hexadecane-water interface Interestingly, P gingivalis cells did not appear to penetrate the hexadecane A viscosus mutants lacking type 1 or type 2 fimbriae or both were still able to bind to the PCHD No obvious correlation was observed between relative hydrophobicity of A viscosus strains and their binding to PCHD However, defatted bovine serum albumin, an inhibitor of hydrophobic interactions, was the most potent inhibitor among those tested The data suggest that this approach provides a simple, quantitative technique for studying kinetics of bacterial coadhesion which is amenable to both light and electron microscopic observation Images

Adhesion of Actinomyces viscosus to Porphyromonas (Bacteroides) gingivalis-coated hexadecane droplets.

Background: In a previous study we showed that prolonged nasogastric tube feeding is associated with pathogenic oral flora. Objective: To reexamine the impact of prolonged nasogastric tube feeding on the oral microbiota and to explore the salivary flow and composition in elderly patients in long-term care. Methods: We compared a group of elderly patients fed by nasogastric tube with a control group of elderly patients in long-term care who are fed orally. Bactenologic studies were performed by culturing samples from the oropharynx. Saliva studies included quantitative and biochemical analysis of basal and stimulated salivary flow. Results: Bacteriologic studies performed in 90 patients revealed a significantly higher prevalence of gram-negative bacteria in nasogastric tube-fed patients (73% vs. 13%, P < 0.001). It is emphasized that Pseudomonas aeruginosa and Klebsiella pneumoniae were commonly and exclusively isolated from the oral flora of the nasogastric tube-fed patients (P < 0.001. P < 0.05). In the saliva studies performed on 23 nasogastric tube-fed and 21 control patients, basal and stimulated salivary flow was not significantly different in the two groups, however the ratio of stimulated to basal flow was reduced in the nasogastric tube-fed group (P < 0.05). Significant differences were also found in the concentrations of sodium, amylase, phosphor and magnesium. Noteworthy was the concentration of uric add, the main non-enzymatic antioxidant of saliva, which was significantly lower in nasogastric-tube fed patients (P < 0.002). Conclusions: These findings suggest that prolonged nasogastric tube feeding is associated with pathologic colonization of the oropharynx and with alterations in the saliva that are related to the risk of aspiration pneumonia. Further research is called for, as well as a thorough revision of the existing oral cleansing procedures in these patients.

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Mel Rosenberg

Papers

Bad breath, diagnosis and treatment.

Association between oral malodour and periodontal disease‐related parameters in a population of 71 Israelis

Global gene expression in Staphylococcus aureus following exposure to alcohol.

Adhesion of Actinomyces viscosus to Porphyromonas (Bacteroides) gingivalis-coated hexadecane droplets.

Saliva secretion and oral flora in prolonged nasogastric tube-fed elderly patients.