Bacterial Interference Research Articles

Effect of Bacterial Interference on Biofilm Development by Legionella pneumophila

In the ecology of Legionella pneumophila a crucial role may be played by its relationship with the natural flora; thus we investigated the interactions between Legionella and other aquatic bacteria, particularly within biofilms. Among 80 aquatic bacteria screened for the production of bacteriocin-like substances (BLSs), 66.2% of them were active against L. pneumophila. The possible effect of some of these aquatic bacteria on the development and stability of L. pneumophila biofilms was studied. Pseudomonas fluorescens, the best BLS producer, showed the greatest negative effect on biofilm formation and strongly enhanced the detachment of Legionella. Pseudomonas aeruginosa, Burkholderia cepacia, Pseudomonas putida, Aeromonas hydrophila, and Stenotrophomonas maltophilia, although producing BLSs at different levels, were less active in the biofilm experiments. Acinetobacter lwoffii did not produce any antagonistic compound and was the only one able to strongly enhance L. pneumophila biofilm. Our results highlight that BLS production may contribute to determining the fate of L. pneumophila within ecological niches. The interactions observed in this study are important features of L. pneumophila ecology, which knowledge may lead to more effective measures to control the persistence of the germ in the environment.

Bacterial interference for the prevention and treatment of infections

Bacterial interference refers to the antagonism between bacterial species during the process of surface colonisation and acquisition of nutrients. The clinical evidence on the potential applications of microorganisms for the prevention and/or treatment of infections in the upper respiratory, urogenital and gastrointestinal tracts was reviewed through the PubMed and Scopus databases. Data regarding factors that may affect the human microflora, thus contributing to tissue colonisation from potential pathogens, were also retrieved. The clinical evidence for application of the interfering ability of non-virulent bacteria to prevent or treat infections has been rather limited, although promising for certain purposes. A number of relevant preliminary trials suggest that in the upper respiratory tract the rate of recurrence of otitis media or streptococcal pharyngotonsillitis appears to decrease using selected bacteria with inhibitory ability against common pathogens of upper respiratory tract in combination with appropriate antibiotic treatment. Regarding the urogenital tract, specific non-pathogenic strains of Escherichia coli and probiotic organisms were successfully applied to decrease the recurrence of local infections. The interfering ability of specific probiotic organisms (strains of Lactobacilli and Bifidobacteria) within the gastrointestinal tract against common pathogens was also demonstrated. In conclusion, randomised controlled trials are warranted to investigate the effectiveness and safety of potential applications of the principle of bacterial interference in the prevention and treatment of infections of various sites. Such trials should initially employ selected strains of probiotics for which there are preliminary data regarding their effectiveness and lack of common or serious toxicity.

Cyclic Peptide Inhibitors of Staphylococcal Virulence Prepared by Fmoc-Based Thiolactone Peptide Synthesis

Virulence factor production in Staphylococcus aureus is largely under the control of the accessory gene regulator (agr) quorum sensing system. There are four agr groups, all of which exhibit bacterial interference: each agr type synthesizes a cyclic autoinducing peptide (AIP) with a distinct sequence that activates its cognate AgrC receptor and inhibits activation of others. To better understand inhibitory AIP-AgrC interactions, we aimed to identify the minimal molecular determinants required to inhibit both non-cognate and cognate receptors. This minimization of the AIP pharmacophore also may have therapeutic relevance as the use of native AIPs to block virulence of non-cognate agr strains can prevent the establishment of an infection in vivo. We synthesized and evaluated the inhibitory activities of 10 AIP derivatives based on a truncated AIP analogue that inhibits all four agr types. To carry out the rapid, parallel synthesis of these peptides, we employed a new linker for Fmoc-based thioester peptide synthesis. Our results identify key structural elements that are necessary for AgrC inhibition and reveal key differences between non-cognate and cognate inhibitory requirements.

Lactobacillus rhamnosus strain GG restores alkaline phosphatase activity in differentiating Caco-2 cells dosed with the potent mycotoxin deoxynivalenol

Deoxynivalenol (DON) contamination of cereal crops occurs frequently, and may cause acute exposure at high levels or chronic more moderate exposure. DON has proven toxicity including restriction of enterocyte differentiation, which may play a part in DON induced gastroenteritis. The probiotic bacteria Lactobacillus rhamnosus strain GG (GG) can bind DON, and therefore potentially restrict bioavailability of this toxin. Binding efficacy is not significantly altered by heat treatment, and therefore this in vitro study evaluated whether heat inactivated GG could restore the differentiation process in Caco-2 cells, using alkaline phosphatase (ALP) activity as a marker of differentiation. DON (200ng/mL) caused a significant (p<0.001) 36% reduction in ALP activity (1598±137U/mg protein) compared to untreated cells (2502±80U/mg). A dose dependant restoration of ALP activity was observed where DON treated cells were co-incubated with heat inactivated GG (1719±84; 2007±142; 2272±160U/mg for GG at 1×104 (p>0.9), 1×107 (p<0.001), and 1×1010CFU/mL (p<0.001), respectively). Co-incubation of the non-binding strain, LC-705 (1×1010CFU/mL), with DON did not significantly restore the ALP (1841±97U/mg, p<0.077) compared to DON only treated cells. When viable GG were co-incubated with DON a similar restoration of ALP activity was observed as seen for heat inactivated GG. These combined data suggest that the major effect of GG on restoring ALP activity, and therefore Caco-2 cell differentiation, was due to specific binding of DON, with possibly a more minor role of non-specific bacterial interference.

Bacterial genotoxins, gene methylation, and RNA interference: Pointing to colorectal cancer as an infectious disease?

Bacterial genotoxins, gene methylation, and RNA interference: Pointing to colorectal cancer as an infectious disease?

Evolution and pathogenesis ofStaphylococcus aureus: lessons learned from genotyping and comparative genomics

Staphylococcus aureus is an opportunistic pathogen and the major causative agent of numerous hospital- and community-acquired infections. Multilocus sequence typing reveals a highly clonal structure for S. aureus. Although infrequently occurring across clonal complexes, homologous recombination still contributed to the evolution of this species over the long term. agr-mediated bacterial interference has divided S. aureus into four groups, which are independent of clonality and provide another view on S. aureus evolution. Genome sequencing of nine S. aureus strains has helped identify a number of virulence factors, but the key determinants for infection are still unknown. Comparison of commensal and pathogenic strains shows no difference in diversity or clonal assignments. Thus, phage dynamics and global transcriptome shifts are considered to be responsible for the pathogenicity. Community-acquired methicillin-resistant S. aureus (C-MRSA) is characterized by a short SCCmec and the presence of a Panton-Valentine leukocidin locus, but no studies have proven their exact biologic roles in C-MRSA infection, indicating the existence of other mechanisms for the genesis of C-MRSA.

Cephalosporins in overcoming β-lactamase-producing bacteria and preservation of the interfering bacteria in the treatment of otitis, sinusitis and tonsillitis

The treatment of upper respiratory tract infections (URTIs) is complicated by the resurgence of β-lactamase-producing bacteria (BLPB) and the absence of interfering bacteria. BLPB can have a direct pathogenic impact in causing the infection as well as an indirect impact through their ability to produce the enzyme β-lactamase. BLPB may not only survive penicillin therapy but can also protect other penicillin-susceptible bacteria from penicillin. In this review, the clinical in vitro and in vivo evidence supporting the role of these organisms in the increased failure rate of penicillin in eradication of otitis, sinusitis and pharyngo-tonsillitis is outlined and the implication of that increased rate on the management of infections is discussed. Bacteria with interference capability of potential respiratory pathogens can prevent colonization and subsequent invasion by these organisms. These include α-hemolytic streptococci, nonhemolytic streptococci and Prevotella and Peptostreptococcus spp. Treatment with antimicrobials can affect the balance between the interfering organisms and potential pathogens. The role of bacterial interference in URTIs and its effect on their treatment is discussed. The use of some of the cephalosporins that are able to overcome the effect of BLPB and preserve the beneficial interfering bacteria can overcome and modulate these phenomena and achieve better cure of URTIs.

Host-Mediated Inflammation Disrupts the Intestinal Microbiota and Promotes the Overgrowth of Enterobacteriaceae

While the normal microbiota has been implicated as a critical defense against invading pathogens, the impact of enteropathogenic infection and host inflammation on intestinal microbial communities has not been elucidated. Using mouse models of Citrobacter rodentium, which closely mimics human diarrheal pathogens inducing host intestinal inflammation, and Campylobacter jejuni infection, as well as chemically and genetically induced models of intestinal inflammation, we demonstrate that host-mediated inflammation in response to an infecting agent, a chemical trigger, or genetic predisposition markedly alters the colonic microbial community. While eliminating a subset of indigenous microbiota, host-mediated inflammation supported the growth of either the resident or introduced aerobic bacteria, particularly of the Enterobacteriaceae family. Further, assault by an enteropathogen and host-mediated inflammation combined to significantly reduce the total numbers of resident colonic bacteria. These findings underscore the importance of intestinal microbial ecosystems in infectious colitis and noninfectious intestinal inflammatory conditions, such as inflammatory bowel disease.

Nasopharyngeal co-colonization with Staphylococcus aureus and Streptococcus pneumoniae in children is bacterial genotype independent

Bacterial interference between Staphylococcus aureus and Streptococcus pneumoniae in the nasopharynx has been observed during colonization, which might have important clinical implications for the widespread use of pneumococcal conjugate vaccine in young children. This study aimed to determine whether the capacity of Staph. aureus to compete with Strep. pneumoniae is dependent on bacterial genotype. Demographic and microbiological determinants of carriage of specific genotypes of Staph. aureus in children were also studied. Children (n=3198) were sampled in the nasopharynx to detect carriage of Staph. aureus, Strep. pneumoniae and Neisseria meningitidis. Staph. aureus genotypes and pneumococcal sero- and genotypes were determined. Age, gender, zip code, active smoking and co-colonization with N. meningitidis or Strep. pneumoniae, both vaccine- and non-vaccine types, were not associated with colonization by specific Staph. aureus genotypes. Based on the whole-genome typing data obtained, there was no obvious correlation between staphylococcal and pneumococcal genotypes during co-colonization. Passive smoking showed a significant association (P=0.003) with carriage of a specific Staph. aureus cluster. This study suggests that there are no major differences between Staph. aureus clones (with different disease-invoking potential) in their capacity to compete with Strep. pneumoniae subtypes. Further studies should demonstrate whether differences in bacterial interference are due to more subtle genetic changes.

Effect of Smoking Cessation on the Microbial Flora

To determine the effect of smoking cessation on the frequency of recovery of potential pathogens and aerobic and anaerobic interfering bacteria in the nasopharynges of smokers. Nasopharyngeal cultures were taken from 20 smokers before and 12 to 15 months after cessation of smoking. Potential pathogens and aerobic and anaerobic bacteria with interfering capabilities against these organisms were identified. Eleven potential pathogens (0.92 pathogens per subject) were isolated from nasopharyngeal cultures obtained from 9 individuals before smoking cessation, and 2 (0.17 per subject) were recovered from 2 individuals after smoking cessation (P < .05). Bacterial interference between 2 aerobic (alpha and nonhemolytic streptococci) and 2 anaerobic species (Prevotella and Peptostreptococcus species) and 4 potential pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pyogenes) was observed. Bacterial interference was noted in 35 instances against the 4 potential pathogens by 14 normal flora isolates that were recovered from the smokers before cessation and in 116 instances by 42 isolates after cessation (P < .01). To our knowledge, these findings illustrate for the first time that the high number of pathogens and low number of interfering organisms found in the nasopharynx of smokers revert to normal levels after complete cessation of smoking.

Development of a Premature Stop Codon-detection method based on a bacterial two-hybrid system

BackgroundThe detection of Premature Stop Codons (PSCs) in human genes is very useful for the genetic diagnosis of different hereditary cancers, e.g. Familial Breast Cancer and Hereditary Non-Polyposis Colorectal Cancer (HNPCC). The products of these PSCs are truncated proteins, detectable in vitro by the Protein Truncation Test and in vivo by using the living translation machinery of yeast or bacteria. These living strategies are based on the construction of recombinant plasmids where the human sequence of interest is inserted upstream of a reporter gene. Although simple, these assays have their limitations. The yeast system requires extensive work to enhance its specificity, and the bacterial systems yield many false results due to translation re-initiation events occurring post PSCs. Our aim was to design a recombinant plasmid useful for detecting PSCs in human genes and resistant to bacterial translation re-initiation interferences.ResultsA functional recombinant plasmid (pREAL) was designed based on a bacterial two-hybrid system. In our design, the in vivo translation of fused fragments of the Bordetella pertussis adenylate cyclase triggers the production of cAMP giving rise to a selectable bacterial phenotype. When a gene of interest is inserted between the two fragments, any PSC inhibits the enzymatic activity of the product, and translation re-initiation events post-PSC yield separated inactive fragments. We demonstrated that the system can accurately detect PSCs in human genes by inserting mutated fragments of the brca1 and msh2 gene. Western Blot assays revealed translation re-initiation events in all the tested colonies, implying that a simpler plasmid would not be resistant to this source of false negative results. The application of the system to a HNPCC family with a nonsense mutation in the msh2 gene correctly diagnosed wild type homozygous and heterozygous patients.ConclusionThe developed pREAL is applicable to the detection of PSCs in human genes related to different diseases and is resistant to translation re-initiation events. The diagnosis steps are easy, have a low cost, detect only pathologic mutations, and allow the analysis of separated alleles.

Broad-spectrum biofilm inhibition by a secreted bacterial polysaccharide.

The development of surface-attached biofilm bacterial communities is considered an important source of nosocomial infections. Recently, bacterial interference via signaling molecules and surface active compounds was shown to antagonize biofilm formation, suggesting that nonantibiotic molecules produced during competitive interactions between bacteria could be used for biofilm reduction. Hence, a better understanding of commensal/pathogen interactions within bacterial community could lead to an improved control of exogenous pathogens. To reveal adhesion or growth-related bacterial interference, we investigated interactions between uropathogenic and commensal Escherichia coli in mixed in vitro biofilms. We demonstrate here that the uropathogenic strain CFT073 and all E. coli expressing group II capsules release into their environment a soluble polysaccharide that induces physicochemical surface alterations, which prevent biofilm formation by a wide range of Gram-positive and Gram-negative bacteria. We show that the treatment of abiotic surfaces with group II capsular polysaccharides drastically reduces both initial adhesion and biofilm development by important nosocomial pathogens. These findings identify capsular polymers as antiadhesion bacterial interference molecules, which may prove to be of significance in the design of new strategies to limit biofilm formation on medical in dwelling devices.

Bacterial interference—is deliberate colonization with Escherichia coli 83972 an alternative treatment for patients with recurrent urinary tract infection?

The increasing microbial antibiotic resistance motivates research for non-antibiotic treatment alternatives. In recurrent urinary tract infections (UTIs), ‘bacterial interference’ has attracted interest as a possible alternative treatment option. The observation that asymptomatic bacteriuria (ABU) protects against recurrent UTI has prompted clinical trials with deliberate colonization of the human urinary tract as an alternative approach in patients with recurrent UTI. The strain used for colonization, the ABU isolate Escherichia coli 83972, has been shown to cause symptom-free colonizations for long periods of time. Patients on long-term colonization report a subjective benefit, and UTI treatments are rare in colonized patients. This report presents an update on open long-term E. coli 83972 colonization trials and describes the design of an ongoing randomized trial.

Biofilm: Its Relevance In Kidney Disease

Biofilm/bioslime is a complex, dynamically interactive multicellular community protected within a heterogeneous exopolysaccharide matrix. Its formation results in the genesis or perpetuation of infection, enhancement of inflammation, and tissue damage or death. Industrial financial losses result from biofilm/bioslime formation; however, the consequences in the medical realm are equally devastating. The relation of biofilm to patients with chronic kidney disease is often covert and extends beyond the colonization of hemodialysis circuits and vascular accesses. Urinary tract device- and vascular access-related biofilms may also increase the burden of cardiovascular risk borne by chronic kidney disease patients, synergizing with the chronic inflammatory state already incurred by these individuals. Current anti-infective strategies are aimed at rapidly killing planktonic forms of microorganisms without specifically targeting the sessile forms that perpetuate their planktonic brethren. Future treatments of infections must ultimately target these reservoirs of infection aiming for their complete eradication. Presently, included among these novel weapons of microdestruction are molecular blockading techniques, electrical enhancement of anti-infectives, and bacterial interference. Nonetheless, the best approach against biofilm formation remains the prevention of microbial colonization, which can be largely by sterile handling of patient-related devices, the most well-established biofilm reservoirs.

Bacterial Interference of Penicillin-Sensitive and -Resistant Streptococcus Pneumoniae by Streptococcus Oralis in an Adenoid Organ Culture: Implications for the Treatment of Recurrent Upper Respiratory Tract Infections in Children and Adults

The role of the viridans group of streptococci (Streptococcus oralis) in the prevention of colonization with Streptococcus pneumoniae was investigated in an adenoid organ culture system. The adenoids from 10 patients who were undergoing adenoidectomy for either hypertrophy or recurrent otitis media were used. Streptococcus oralis Parker and S. oralis Booth (two organisms isolated from the nasopharynges of patients undergoing adenoidectomy only and patients undergoing adenoidectomy and bilateral tympanostomy with tubes, respectively) uniformly inhibited both penicillin-sensitive and penicillin-resistant S. pneumoniae. Although both strains of S. oralis inhibited the growth of both S. pneumoniae strains, strain Parker provided more complete inhibition than did strain Booth. The results indicate that some strains of S. oralis may inhibit the growth of the most serious pathogens in the nasopharynx. It is therefore possible that colonization of inhibitory strains of viridans streptococci may be used in the nasopharynx as a relatively safe and inexpensive approach to prevention of recurrent otitis media in some children and of recurrent suppurative sinusitis in both children and adults.

The Role of Bacterial Interference in Otitis, Sinusitis and Tonsillitis

The Role of Bacterial Interference in Otitis, Sinusitis and Tonsillitis

Urinary tract infections: what's new?

This review provides practicing urologists with important basic information about urinary tract infections (UTIs) that can be applied to everyday clinical problems. A review is presented of provocative and controversial concepts in the current literature. Bacterial virulence mechanisms are critical for overcoming the normal host defenses. Increasing antimicrobial resistance of uropathogens has led to reconsideration of traditional treatment recommendations in many areas. For effective patient management the first issue is to define complicating urological factors. Managing complicated urinary tract infections, particularly in urology, is determined by clinical experience to define the pertinent anatomy and to determine the optimal interventions. New clinical data are summarized on UTIs in long-term care patients, behavioral risks for UTI in healthy women and anatomical differences associated with an increased risk for UTI. The rationale is presented for UTI prophylaxis using cranberry juice, immunization and bacterial interference. Current treatment trends for UTI include empiric therapy (without urine culture and sensitivity testing), short-course therapy, patient-administered (self-start) therapy and outpatient therapy for uncomplicated pyelonephritis. Recommendations for treating patients with UTIs have changed based on basic science and clinical experience.

Bacterial Interference in the Urinary Tract

Device-related bacterial colonization of the urinary tract and, occasionally, invasive infection are among the most common management problems encountered by infectious diseases consultants. Our usual response is to urge limits on catheter use, avoid treating asymptomatic infection, and anticipate occasional, sometimes life-threatening invasive infections. This advice is generally viewed as being not very helpful. During the 1960s, progress was made with the introduction of closed urinary drainage systems for patients requiring short-term catheterization and intermittent catheter use for patients with neurologically impaired bladders. Otherwise, little has changed in the past quartercentury. We have learned that pyuria accompanying bacteriuria has no particular significance, that even though we may only identify 1 pathogen in a urine culture, multiple organisms are frequently resident in the urinary tract-which is overgrown by the most rapidly grown organism-and that impregnation of catheters with antimicrobial substances has limited (if any) value in the prevention of bacteriuria.

Bacterial Interference for Prevention of Urinary Tract Infection: A Prospective, Randomized, Placebo-Controlled, Double-Blind Pilot Trial

This prospective, randomized, placebo-controlled, double-blind pilot trial examined the efficacy of bacterial interference in preventing urinary tract infection (UTI) in 27 patients with spinal cord injury. Patients whose bladders became colonized with Escherichia coli 83972 were half as likely (P=.01) than noncolonized patients to develop UTI during the subsequent year.

Recovery of Potential Pathogens and Interfering Bacteria in the Nasopharynx of Otitis Media–Prone Children and Their Smoking and Nonsmoking Parents

To study the frequency of isolation of potential pathogens and interfering bacteria in the posterior nasopharynx of otitis media-prone (OMP) children and their smoking and nonsmoking parents to possibly explain why active and passive exposure to smoking is associated with carriage of potentially pathogenic bacteria and an increased risk of respiratory tract infection in both adults and children. Outpatient clinic. Twenty OMP children and their smoking parents (smoking group) and 20 OMP children and their nonsmoking parents (nonsmoking group). Posterior nasopharynx cultures were taken from 20 OMP children and their smoking parents and 20 OMP children and their nonsmoking parents. Potential pathogens and aerobic and anaerobic bacteria with interfering capabilities against these organisms were identified. Fourteen potential pathogens were isolated from smoking parents, and 17 were recovered from their children. Concordance in isolation of a pathogen between a parent and child was noted in 11 instances. Three potential pathogens were isolated from nonsmoking parents (P<.001 compared with the parents and children in the smoking group and children in the nonsmoking group), and 16 were recovered from their children. Bacterial interference by normal flora isolates against potential pathogens was noted in 58 instances in smoking parents and in 55 instances in their children (P<.05). Bacterial interference was noted in 129 instances in nonsmoking parents (P<.05 compared with the parents and children in the smoking group and children in the nonsmoking group) and in 55 instances in their children. A high recovery rate of potential pathogens and a low number of interfering organisms were observed in OMP children. This was not related to their parents' smoking habits. The posterior nasopharynx flora of smoking parents contained more potential pathogens similar to the ones recovered from OMP children and fewer interfering organisms than nonsmoking parents.