Showing papers on "Pathogenic bacteria published in 2008"

Bacteria Subsisting on Antibiotics

Abstract: Antibiotics are a crucial line of defense against bacterial infections. Nevertheless, several antibiotics are natural products of microorganisms that have as yet poorly appreciated ecological roles in the wider environment. We isolated hundreds of soil bacteria with the capacity to grow on antibiotics as a sole carbon source. Of 18 antibiotics tested, representing eight major classes of natural and synthetic origin, 13 to 17 supported the growth of clonal bacteria from each of 11 diverse soils. Bacteria subsisting on antibiotics are surprisingly phylogenetically diverse, and many are closely related to human pathogens. Furthermore, each antibiotic-consuming isolate was resistant to multiple antibiotics at clinically relevant concentrations. This phenomenon suggests that this unappreciated reservoir of antibiotic-resistance determinants can contribute to the increasing levels of multiple antibiotic resistance in pathogenic bacteria.

Targeted photothermal lysis of the pathogenic bacteria, Pseudomonas aeruginosa, with gold nanorods.

Abstract: Increases in the prevalence of antibiotic resistant bacteria require new approaches for the treatment of infectious bacterial pathogens. It is now clear that a nanotechnology-driven approach using nanoparticles to selectively target and destroy pathogenic bacteria can be successfully implemented. We have explored this approach by using gold nanorods that have been covalently linked to primary antibodies to selectively destroy the pathogenic Gram-negative bacterium, Pseudomonas aeruginosa. We find that, following nanorod attachment to the bacterial cell surface, exposure to near-infrared radiation results in a significant reduction in bacterial cell viability.

Interplay of commensal and pathogenic bacteria, genetic mutations, and immunoregulatory defects in the pathogenesis of inflammatory bowel diseases.

Abstract: Enteric microbiota can contribute to Crohn's disease and ulcerative colitis in several ways. Pathogenic or functionally altered commensal bacteria with increased mucosal adherence, invasion and intracellular persistence can activate pathogenic T cells and chronic intestinal inflammation. Compositional changes in intestinal microbiota can lead to decreased protective and increased aggressive species. Genetic polymorphisms resulting in increased mucosal permeability, decreased microbial killing, ineffective clearance of bacteria, biased TH1 and TH17 immune responses and loss of immunological tolerance are probably key contributors to IBD. Future therapies for these heterogeneous diseases should be individualized based on the patient-specific subset.

Plants as a Habitat for Beneficial and/or Human Pathogenic Bacteria

Abstract: Non-plant pathogenic endophytic bacteria can promote plant growth, improve nitrogen nutrition, and, in some cases, are human pathogens. Recent work in several laboratories has shown that enteric bacteria are common inhabitants of the interior of plants. These observations led to the experiments that showed the entry into plants of enteric human pathogens such as Salmonella and E. coli O157:H7. The extent of endophytic colonization by strains is regulated by plant defenses and several genetic determinants necessary for this interior colonization in endophytic bacteria have been identified. The genomes of four endophytic bacteria now available should promote discovery of other genes that contribute to this phenotype. Common virulence factors in plant and animal pathogens have also been described in bacteria that can infect both plant and animal models. Future directions in all of these areas are proposed.

Genomic fluidity and pathogenic bacteria: applications in diagnostics, epidemiology and intervention

Abstract: The increasing availability of DNA-sequence information for multiple pathogenic and non-pathogenic variants of individual bacterial species has indicated that both DNA acquisition and genome reduction have important roles in genome evolution. Such genomic fluidity, which is found in human pathogens such as Escherichia coli, Helicobacter pylori and Mycobacterium tuberculosis, has important consequences for the clinical management of the diseases that are caused by these pathogens and for the development of diagnostics and new molecular epidemiological methods.

Virulence blockers as alternatives to antibiotics : type III secretion inhibitors against Gram-negative bacteria

Abstract: In recent years mounting problems related to antibiotic-resistant bacteria have resulted in the prediction that we are entering the preantibiotic era. A way of preventing such a development would be to introduce novel antibacterial medicines with modes of action distinct from conventional antibiotics. Recent studies of bacterial virulence factors and toxins have resulted in increased understanding of the way in which pathogenic bacteria manipulate host cellular processes. This knowledge may now be used to develop novel antibacterial medicines that disarm pathogenic bacteria. The type III secretion system (T3SS) is known to be a potent virulence mechanism shared by a broad spectrum of pathogenic Gram-negative bacteria that interact with human, animal and plant hosts by injecting effector proteins into the cytosol of host cells. Diseases, such as bubonic plague, shigellosis, salmonellosis, typhoid fever, pulmonary infections, sexually transmitted chlamydia and diarrhoea largely depend on the bacterial proteins injected by the T3SS machinery. Recently a number of T3SS inhibitors have been identified using screening-based approaches. One class of inhibitors, the salicylidene acylhydrazides, has been subjected to chemical optimization and evaluation in several in vitro and ex vivo assays in multiple bacterial species including Yersinia spp., Chlamydia spp., Salmonella spp. and Pseudotuberculosis aeruginosa. Reports published up to date indicate that T3SS inhibitors have the potential to be developed into novel antibacterial therapeutics.

Evaluation of in vitro antibacterial property of seaweeds of southeast coast of India

Abstract: The in vitro antibacterial activities of seaweeds belong to Chlorophyceae (Caulerpa racemosa and Ulva lactuca), Rhodophyceae (Gracillaria folifera and Hypneme muciformis) and Phaeophyceae (Sargassum myricocystum, Sargassum tenneerimum and Padina tetrastomatica) were studied against both Gramnegative and Gram-positive pathogenic bacteria. Methanolic extracts of all seaweed extracts tested in the present study exhibited broad spectrum of antibacterial activity. Chlorophyceae members showed high antibacterial activity than other members of the algae tested in the present investigation. Escherchia coli alone resistant to all the seaweed extracts except S. teneerimum. Results of the present study confirmed the potential use of seaweed extracts as a source of antibacterial compounds.

Comparative antimicrobial activity of tannin extracts from perennial plants on mastitis pathogens

Abstract: Three strains of pathogenic bacteria were treated with condensed tannins (CT) purified from eight different woody plant species to investigate their inhibition effect on the growth of these bacteria in vitro. Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were tested against low (0, 2, 4 and 8 mg CT/ml) and high dose levels (0, 50, and 100 mg CT /ml) of CT extracted from different plant species. When exposed to purified tannin extracts at 4 mg extract/ml dosage, growth inhibition of S. aureus was dose dependent manner and observed in the following order: Shinnery oak > Post oak >

Selective antimicrobial activity of maggots against pathogenic bacteria.

Abstract: Maggot therapy, also known as biosurgery, is an ancient method for the healing of chronic infected wounds. Although clinicians have reported on the beneficial activities of the Lucilia sericata larvae that have been used for healing chronic wounds, the selectivity of this therapy against the different pathogenic micro-organisms that are found in chronic wounds has never been analysed. In the present study, we have investigated the in vitro activities of larval excreta/secreta both against selected bacterial strains that frequently occur in chronically infected wounds, and against bacteria isolated directly from the larvae and their excreta/secreta. Additionally, the antibacterial activities were investigated in in vivo studies, by comparing bacterial diversity in wounds before and after the application of L. sericata larvae. In conclusion, larval therapy is highly recommended, particularly for the treatment of wounds infected with Gram-positive bacteria, like Staphylococcus aureus, but less so for wounds infected with Gram-negative bacteria, especially Proteus spp. and Pseudomonas spp. strains. Bacteria from the genus Vagococcus were resistant to the maggot excreta/secreta.

Effects of Pulsed Electric Fields on Pathogenic Microorganisms of Major Concern in Fluid Foods: A Review

Abstract: Pathogenic microorganisms such as Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni have been implicated in foodborne diseases and outbreaks worldwide. These bacteria have been associated with the consumption of fresh fruit juices, milk, and dairy products, which are foodstuff, highly demanded by consumers in retails and supermarkets. Nowadays, consumers require high quality, fresh-like, and safe foods. Pulsed electric field (PEF) is a non-thermal preservation method, able to inactivate pathogenic microorganisms without significant loss of the organoleptic and nutritional properties of food. The PEF treatment effectiveness to destroy bacteria such as Listeria innocua, E. coli, Salmonella Typhimurium, E. coli O157:H7 and E. coli 8739 at pasteurization levels (> or = 5.0 log(10) cycles) in some fluid foods was reported. However, data on the inactivation of some microorganisms such as Bacillus cereus, Staphylococcus aureus, Yersinia enterocolitica, and Campylobacter jejuni in fluid foods by PEF processing is very limited. Therefore, future works should be focused toward the inactivation of these pathogenic bacteria in real foods.

Symbiotic association between hoopoes and antibiotic- producing bacteria that live in their uropygial gland

Abstract: Summary 1. It has been recently showed that one bacterial strain isolated from the uropygial gland of a nestling hoopoe Upupa epops produced antimicrobial peptides active against a broad spectrum of pathogenic bacteria. These bacteria might thus mediate antimicrobial properties of the uropygial secretions as a consequence of the symbiotic association with hoopoes. 2. We study antimicrobial properties of white (from males and non-breeding females) and brown (from nestlings and breeding females) uropygial gland secretions of hoopoes Upupa epops , as well as the association with the presence of bacteria living inside their uropygial gland. 3. We found that brown, but not white secretions contained bacteria and showed antimicrobial activity against the feather degrading bacterium Bacillus licheniformis . The antagonistic activity of bacterial colonies was mediated by antimicrobial peptides because protease inhibited antimicrobial properties. 4. All except one identified bacterium in aerobic cultures were of the genus Enterococcus , and the microscopic study of uropygial secretions and glands confirmed a high density of bacteria within the gland. 5. Furthermore, we studied potential benefits of antimicrobial peptides produced by symbiotic bacteria of hoopoes by adding protease to incubating nests. 6. The experiment increased bacterial growth and hatching failures in hoopoes but not in spotless starlings Sturnus unicolor , a species that does not harbour bacteria in its uropygial gland. 7. Thus, microbiological, anatomical and ecological results suggest a tight symbiotic interaction between bacteria that produce antibiotic substances and the hoopoes.

The Interplay between Entamoeba and Enteropathogenic Bacteria Modulates Epithelial Cell Damage

Abstract: Background Mixed intestinal infections with Entamoeba histolytica, Entamoeba dispar and bacteria with exacerbated manifestations of disease are common in regions where amoebiasis is endemic. However, amoeba–bacteria interactions remain largely unexamined. Methodology Trophozoites of E. histolytica and E. dispar were co-cultured with enteropathogenic bacteria strains Escherichia coli (EPEC), Shigella dysenteriae and a commensal Escherichia coli. Amoebae that phagocytosed bacteria were tested for a cytopathic effect on epithelial cell monolayers. Cysteine proteinase activity, adhesion and cell surface concentration of Gal/GalNAc lectin were analyzed in amoebae showing increased virulence. Structural and functional changes and induction of IL-8 expression were determined in epithelial cells before and after exposure to bacteria. Chemotaxis of amoebae and neutrophils to human IL-8 and conditioned culture media from epithelial cells exposed to bacteria was quantified. Principal Findings E. histolytica digested phagocytosed bacteria, although S. dysenteriae retained 70% viability after ingestion. Phagocytosis of pathogenic bacteria augmented the cytopathic effect of E. histolytica and increased expression of Gal/GalNAc lectin on the amoebic surface and increased cysteine proteinase activity. E. dispar remained avirulent. Adhesion of amoebae and damage to cells exposed to bacteria were increased. Additional increases were observed if amoebae had phagocytosed bacteria. Co-culture of epithelial cells with enteropathogenic bacteria disrupted monolayer permeability and induced expression of IL-8. Media from these co-cultures and human recombinant IL-8 were similarly chemotactic for neutrophils and E. histolytica. Conclusions Epithelial monolayers exposed to enteropathogenic bacteria become more susceptible to E. histolytica damage. At the same time, phagocytosis of pathogenic bacteria by amoebae further increased epithelial cell damage. Significance The in vitro system presented here provides evidence that the Entamoeba/enteropathogenic bacteria interplay modulates epithelial cell responses to the pathogens. In mixed intestinal infections, where such interactions are possible, they could influence the outcome of disease. The results offer insights to continue research on this phenomenon.

Use of the probiotic Lactobacillus plantarum 299 to reduce pathogenic bacteria in the oropharynx of intubated patients : a randomised controlled open pilot study

Abstract: Introduction Ventilator-associated pneumonia (VAP) is usually caused by aspiration of pathogenic bacteria from the oropharynx. Oral decontamination with antiseptics, such as chlorhexidine (CHX) or antibiotics, has been used as prophylaxis against this complication. We hypothesised that the probiotic bacteria Lactobacillus plantarum 299 (Lp299) would be as efficient as CHX in reducing the pathogenic bacterial load in the oropharynx of tracheally intubated, mechanically ventilated, critically ill patients. Methods Fifty critically ill patients on mechanical ventilation were randomised to either oral mechanical cleansing followed by washing with 0.1% CHX solution or to the same cleansing procedure followed by oral application of an emulsion of Lp299. Samples for microbiological analyses were taken from the oropharynx and trachea at inclusion and at defined intervals thereafter. Results Potentially pathogenic bacteria that were not present at inclusion were identified in oropharyngeal samples from eight of the patients treated with Lp299 and 13 of those treated with CHX (p = 0.13). Analysis of tracheal samples yielded similar results. Lp299 was recovered from the oropharynx of all patients in the Lp299 group. Conclusions In this pilot study, we found no difference between the effect of Lp299 and CHX used in oral care procedures, when we examined the effects of those agents on colonisation of potentially pathogenic bacteria in the oropharynx of intubated, mechanically ventilated patients.

Antibacterial Activity of Important Medicinal Plants on Human Pathogenic Bacteria-a Comparative Analysis

Abstract: he use of plants in treatment of burns, dermatophytes and infectious diseases is common in traditional medicine. Based on ethno pharmacological and taxonomic information, antibacterial activities of aqueous and methanol extracts of some medicinal plants were determined by in vitro by agar diffusion-method against some human pathogenic bacteria. The leaves of five different plants,belonging to the different family and which have some ethnomedicinal applications were studied for antibacterial activity. Powdered leaf materials of all selected plants were extracted with aqueous and methanol. The solvent extracts were evaporated to dryness using rotary flash evaporator. Dry residue was dissolved in methanol (1:10 w/v) and tested for antibacterial activity. The antibacterial screening of aqueous and methanol extract carried out in vitro on the following bacteria viz.,Bacillus cereus, Bacillus megaterium, Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, Streptococcus faecalis and Yersinia enterocolitica. It has been showed that the methanol extracts had wider range of activity on these organisms than the aqueous extracts, which indicates that the methanol extracts of all selected plants may contain the active components. This study supports, the traditional medicines (herbal extracts) to cure many diseases like diarrhea, intestinal tract, throat, ear infections, fever and skin diseases

Isolation of naturally associated bacteria of necromenic Pristionchus nematodes and fitness consequences.

Abstract: SUMMARY Nematodes and bacteria are major components of the soil ecosystem. Many nematodes use bacteria for food, whereas others evolved specialized bacterial interactions ranging from mutualism to parasitism. Little is known about the biological mechanisms by which nematode–bacterial interactions are achieved, largely because in the laboratory nematodes are often cultured under artificial conditions. We investigated the bacterial interactions of nematodes from the genus Pristionchus that have a strong association with scarab beetles. Pristionchus has a different feeding strategy than Caenorhabditis and meta-genomic 16S sequence analysis of Pristionchus individuals showed a diversity of living bacteria within the nematode gut and on the nematode cuticle. Twenty-three different bacterial strains were isolated from three Pristionchus–beetle associations and were used to study nematode–bacterial interactions under controlled laboratory conditions. We show a continuum of bacterial interactions from dissemination, to reduction in brood size and nematode mortality caused by bacteria derived from insect hosts. Olfactory discrimination experiments show distinct chemoattraction and fitness profiles of Pristionchus nematodes when exposed to different bacteria. For example, Pristionchus pacificus avoids Serratia marcescens possibly because of pathogenicity. Also, P. pacificus avoids Bacillus thuringiensis and insect pathogenic bacteria but is resistant to the human pathogens Staphylococcus aureus and Pseudomonas aeruginosa, unlike Caenorhabditis elegans. Pristionchus specifically recognize and respond to bacteria that cause ill health. Bringing the nematode–bacterial interaction into the laboratory allows detailed functional studies, including the genetic manipulation of the interaction in both nematodes and bacteria.

Antimicrobial activity of Nigella sativa Linn. seed oil against multi-drug resistant bacteria from clinical isolates

Abstract: An alarming increase in bacterial strains resistant to existing antimicrobial agents demands a renewed effort to seek agents effective against pathogenic bacteria resistant to current antimicrobials. Nigella sativa Linn. (Black cumin) essential oil was studied for antibacterial activity against various clinical isolates of bacteria resistant to a number of antibiotics, in varying concentrations by Disc Agar diffusion technique using impregnated filter paper discs on inoculated Muellar Hinton agar plates. The oil showed pronounced dose dependant antibacterial activity which was more against Gram positive than Gram negative bacteria. Among Gram positive bacteria tested, Staphylococcus aureus, S. epidermidis, other coagulase –ve Staphylococci and Streptococcus pyogenes were sensitive to the oil and Enterococcus faecalis, Streptococcus agalactiae were resistant. Among Gram –ve bacteria tested, only Pseudomonas aeruginosa was sensitive to oil and rest (Acinetobacter baumannii, Citrobacter freundii, Klebsiella pneumoniae, Proteus mirabilis, P. vulgaris and Vibrio cholerae) were insensitive. Out of 144 strains tested, most of which were resistant to a number of antibiotics, 97 were inhibited by the oil of black cumin. To the best of our knowledge, the activity of essential oil against coagulase negative Staphylococci (except S. epidermidis) and Streptococcus pyogenes is being reported for the first time.

Association of nasopharyngeal bacterial colonization during upper respiratory tract infection and the development of acute otitis media.

Abstract: Acute Otitis Media occurs mostly after upper respiratory tract infection; the causative bacteria are those colonized in the nasopharynx. We studied 709 URI episodes and found that children with no bacteria in NP were at low risk while those with three pathogenic bacteria were at the greatest risk for AOM.

Interactions of some common pathogenic bacteria with Acanthamoeba polyphaga

Abstract: Protozoan grazing is a major trophic pathway whereby the biomass re-enters the food web. Nonetheless, not all bacteria are digested by protozoa and the number known to evade digestion, resulting in their environmental augmentation, is increasing. We investigated the interactions of Bacillus cereus, Enterococcus faecalis, Enteropathogenic Escherichia coli (EPEC), Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and methicillin-sensitive Staphylococcus aureus (MSSA), with the amoeba, Acanthamoeba polyphaga. There was evidence of predation of all bacterial species except L. monocytogenes and S. aureus, where extracellular numbers were significantly higher when cultured with amoebae compared with growth in the absence of amoebae. Intracellular growth kinetic experiments and fluorescent confocal microscopy suggest that S. aureus survived and may even multiply within A. polyphaga, whereas there was no apparent intra-amoebal replication of L. monocytogenes and higher numbers were likely sustained on metabolic waste products released during coculture.