Abscesses In Mice Research Articles

A β‐Lactone‐Based Antivirulence Drug Ameliorates Staphylococcus aureus Skin Infections in Mice

Skin infections caused by Staphylococcus aureus are a major clinical concern, especially if they are caused by multi-resistant strains. In these cases, a spread into deeper soft tissues or the bloodstream results in life-threatening conditions that are difficult to treat by conventional antibiotics. Previous in vitro experiments with a small β-lactone-based molecule demonstrated that antibiotic-sensitive and -resistant S. aureus strains are effectively disarmed in their virulence and corresponding pathogenicity. In this work, in vivo mouse studies show that this methodology is effective for the treatment of skin abscesses in mice. A single dose of the β-lactone significantly decreased abscess size even when applied 6 h post-infection. Although the molecule requires pharmacological optimization (improved stability, for example), this study emphasizes the potential value of antivirulence therapies.

TREM-1 Promotes Survival during Klebsiella pneumoniae Liver Abscess in Mice

Klebsiella pneumoniae liver abscess (KPLA) is prevalent in East Asia. Liver abscess can develop after translocation of K. pneumoniae from a patient's bowel into the liver via the portal circulation. TREM-1 (triggering receptor expressed on myeloid cells 1) amplifies inflammatory signaling during infection, but its role in KPLA is poorly understood. We used an animal study to characterize the role of TREM-1 in KPLA. We compared survival rates, bacterial burdens in tissues, inflammatory cytokine levels, and histology findings between wild-type and Trem-1 knockout (KO) mice after oral inoculation of capsular type K1 K. pneumoniae. Translocation of K. pneumoniae to mesenteric lymph nodes and liver was examined, and intestinal permeability, antimicrobial peptide expression, and the clearance of K. pneumoniae in the small intestine were determined. In the absence of TREM-1, KPLA model mice showed increased K. pneumoniae dissemination, enhanced liver and systemic inflammation, and reduced survival. Impaired bacterial clearance in the small intestine causes enhanced K. pneumoniae translocation, which renders Trem-1 KO mice more susceptible to K. pneumoniae oral infection. In conclusion, TREM-1-mediated bacterial clearance in the small intestine is an important immune response against K. pneumoniae. TREM-1 deficiency enhances K. pneumoniae translocation in the small intestine and increases mortality rates in mice with KPLA.

The Protective Effect of Recombinant FomA-expressing Lactobacillus acidophilus Against Periodontal Infection

A number of studies have shown that the outer membrane protein FomA found in Fusobacterium nucleatum demonstrates great potential as an immune target for combating periodontitis. Lactobacillus acidophilus is a useful antigen delivery vehicle for mucosal immunisation, and previous studies by our group have shown that L. acidophilus acts as a protective factor in periodontal health. In this study, making use of the immunogenicity of FomA and the probiotic properties of L. acidophilus, we constructed a recombinant form of L. acidophilus expressing the FomA protein and detected the FomA-specific IgG in the serum and sIgA in the saliva of mice through oral administration with the recombinant strains. When serum containing FomA-specific antibodies was incubated with the F. nucleatum in vitro, the number of Porphyromonas gingivalis cells that coaggregated with the F. nucleatum cells was significantly reduced. Furthermore, a mouse gum abscess model was successfully generated, and the range of gingival abscesses in the immune mice was relatively limited compared with the control group. The level of IL-1β in the serum and local gum tissues of the immune mice was consistently lower than in the control group. Our findings indicated that oral administration of the recombinant L. acidophilus reduced the risk of periodontal infection with P. gingivalis and F. nucleatum.

Testosterone Increases Susceptibility to Amebic Liver Abscess in Mice and Mediates Inhibition of IFNγ Secretion in Natural Killer T Cells

Amebic liver abscess (ALA), a parasitic disease due to infection with the protozoan Entamoeba histolytica, occurs age and gender dependent with strong preferences for adult males. Using a mouse model for ALA with a similar male bias for the disease, we have investigated the role of female and male sexual hormones and provide evidence for a strong contribution of testosterone. Removal of testosterone by orchiectomy significantly reduced sizes of abscesses in male mice, while substitution of testosterone increased development of ALA in female mice. Activation of natural killer T (NKT) cells, which are known to be important for the control of ALA, is influenced by testosterone. Specifically activated NKT cells isolated from female mice produce more IFNγ compared to NKT cells derived from male mice. This high level production of IFNγ in female derived NKT cells was inhibited by testosterone substitution, while the IFNγ production in male derived NKT cells was increased by orchiectomy. Gender dependent differences were not a result of differences in the total number of NKT cells, but a result of a higher activation potential for the CD4− NKT cell subpopulation in female mice. Taken together, we conclude that the hormone status of the host, in particular the testosterone level, determines susceptibility to ALA at least in a mouse model of the disease.

Serum Lysozyme (Muramidase) Levels in Intra-Abdominal Abscesses: An Experimental Study.

The role of serum lysozyme in the presence of intra-abdominal sepsis was studied to act as an adjunct to various other modalities used for diagnosing intra-abdominal abscesses. Lysozyme (muramidase) is a bacteriolytic enzyme located within phagocytic cells including leukocytes. We measured serum concentrations of lysozyme by a standard turbidimetric method on three groups of murine models. One group underwent caecal ligation and puncture (CLP), the second group underwent a sham operation, and the third group was used as controls. In mice with intra-abdominal abscesses secondary to caecal ligation and perforation (n = 30), the serum lysozyme levels were increased compared to the sham-operated mice (n = 30) and controls (n = 30) (p = <0.001). In this study, serum lysozyme levels have a high sensitivity and specificity related to the presence of an intra-abdominal abscess in mice. Clinical studies are required to demonstrate its role in humans.

Pathogenicity of exopolysaccharide‐producing Actinomyces oris isolated from an apical abscess lesion

AimTo demonstrate a capacity for producing exopolysaccharides (EPSs) and an ability to form biofilm on abiotic materials of Actinomyces oris strain K20.MethodologyThe productivity of EPSs and the ability to form biofilm of strain K20 were evaluated by measuring viscosity of spent culture media and by scanning electron microscopy (SEM) and the biofilm assay on microtitre plates, respectively. High-performance liquid chromatography was used to determine the chemical composition of the viscous materials. To examine the role of the viscous materials attributable to the pathogenicity in this organism, the ability of strain K20 to induce abscess formation was compared in mice to that of ATCC 27044.ResultsThe viscosity of the spent culture media of K20 was significantly higher than that of ATCC 27044. Strain K20 showed dense meshwork structures around the cells and formed biofilms on microtitre plates, whereas ATCC 27044 did not. Chemical analysis of the viscous materials revealed that they were mainly composed of neutral sugars with mannose constituting 77.5% of the polysaccharides. Strain K20 induced persistent abscesses in mice lasting at least 5 days at a concentration of 108 cells mL−1, whereas abscesses induced by ATCC 27044 healed and disappeared or decreased in size at day 5.ConclusionsStrain K20 produced EPSs, mainly consisting of mannose, and formed biofilms. This phenotype might play an important role for A. oris to express virulence through the progression of apical periodontitis.

Virulence mechanisms of Tannerella forsythia.

The subgingival periodontal pocket of humans harbors more than 500 bacterial species. Periodontitis is a chronic inflammation of the periodontium with multi-factorial etiology. It is initiated due to colonization as subgingival biofilms by a group of gram-negative anaerobes. The disease progresses as a result of the direct effects of bacterial virulence factors on host tissues as well as the self-damaging host responses to the colonizing bacteria (83). While no single species has been implicated as the primary pathogen and the available evidence is consistent with a polymicrobial disease etiology, the red-complex bacteria consisting of Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia has been strongly implicated in the onset of periodontitis (83). On the other hand, investigations utilizing the 16S ribotyping have also implicated novel phylotypes in the absence of detectable red-complex bacteria associated with periodontal lesions (44). In support of T. forsythia as being a suspected periodontal pathogen, the organism satisfies the necessary criteria postulated by Socransky and co-workers (82, 83). For instance: (i) its association and increased levels in periodontitis (83), (ii) evidence of host responses to its antigens (2, 81, 94) (iii) its ability to cause disease in animal models (2, 40, 79, 84), and (iv) expression of virulence factors which can potentially contribute to the disease process (described in detail in this review). T. forsythia is an anaerobic gram-negative member of the Cytophaga-Bacteroides family which was initially described as Bacteroides forsythus by Tanner et al. (87) and later reclassified as Tannerella forsythia by Sakamoto et al. (74) based on 16S rRNA phylogenetic analysis. T. forsythia is associated more frequently and/or in higher levels with various forms of the disease, including gingivitis, chronic and aggressive periodontitis, than with health (for review see Ref. (86)). Several studies have also implicated T. forsythia in the progression of clinical attachment loss associated with periodontitis (11, 18, 19, 50, 85). Moreover, a recent study has suggested that T. forsythia infection is more likely to cause periodontitis in overweight women than in normal weight women (7). According to another recent study, overweight or obese individuals have an overgrowth of T. forsythia compared to normal weight individuals, thus subjecting overweight and obese individuals to a higher risk of developing periodontal disease (20). In spite of the overwhelming evidence implicating T. forsythia in pathogenesis, this bacterium remains an understudied organism. This is partly due to the fastidious growth requirement for culturing this bacterium, as well as the fact that genetic manipulations of this organism are difficult to perform (30, 73). Moreover, there are no gene complementation systems currently available for the organism. While T. forsythia is the sole member of the new genus Tannerella, uncultivated oral phylotypes BU045, BU063, 97 and 997 are its closest relatives (95). These phylotypes have long rod-like segmented structure, and though they are frequently found in various periodontal disease-associated plaques, they are present only in low numbers, do not proliferate to high densities and therefore, are considered not relevant to disease pathogenesis (95). Studies in animal models have demonstrated the virulence potential of T. forsythia. For example, T. forsythia caused skin abscesses in rabbits (84) and mice (2, 93) as well as alveolar bone loss in mice (79) and rats (40). These in vivo studies also showed that the pathogenic potential of T. forsythia was enhanced in the presence of other bacteria. For instance, abscess formation in rabbits and in mice was enhanced synergistically when Fusobacterium nucleatum or P. gingivalis were the coinfecting partners of T. forsythia. Similarly, a synergy was observed relative to alveolar bone loss in rats following oral infection with the red-complex consortium, P. gingivalis, T. denticola and T. forsythia (40). These results demonstrate that T. forsythia is a pathogenic organism which might play synergistic roles in inflammation along with other periodontal pathogens. Therefore, in order to fully understand the mechanisms underlying the pathogenesis associated with T. forsythia, it would be important to identify the virulence functions of the organism and determine how these factors are regulated in response to coexisting bacteria and to host-derived factors. It is likely that T. forsythia might influence the physiology and virulence of coexisting periodontal pathogens. For this purpose, physical, chemical, and metabolic interactions are expected to occur, which might further involve bacterial two component sensor-regulator systems. So far, only a few putative virulence factors have been identified in T. forsythia: trypsin-like (17) and PrtH proteases (72), sialidases SiaH (6, 35) and NanH (88), a leucine-rich repeat cell-surface-associated and secreted protein BspA (81), an apoptosis-inducing activity (61), alpha-D-glucosidase and N-acetyl-beta-glucosaminidase (32), a hemagglutinin (59), components of the bacterial S-layer (71, 73), and methylglyoxal production (53).

Nitric Oxide Releasing Nanoparticles Are Therapeutic for Staphylococcus aureus Abscesses in a Murine Model of Infection

Staphylococcus aureus (SA) is a leading cause of a diverse spectrum of bacterial diseases, including abscesses. Nitric oxide (NO) is a critical component of the natural host defense against pathogens such as SA, but its therapeutic applications have been limited by a lack of effective delivery options. We tested the efficacy of a NO-releasing nanoparticle system (NO-np) in methicillin-resistant SA (MRSA) abscesses in mice. The results show that the NO-np exert antimicrobial activity against MRSA in vitro and in abscesses. Topical or intradermal NO-np treatment of abscesses reduces the involved area and bacterial load while improving skin architecture. Notably, we evaluated pro- and anti-inflammatory cytokines that are involved in immunomodulation and wound healing, revealing that NO-np lead to a reduction in angiogenesis preventing bacterial dissemination from abscesses. These data suggest that NO-np may be useful therapeutics for microbial abscesses.

A prospective study of macrophage migration inhibitory factor as a marker of inflammatory detection

This study was to evaluate whether macrophage migration inhibitory factor (MIF) can be used as a better marker of inflammatory detection through the biodistribution and inflammatory imaging study with 131I-labelled anti-MIF McAb and control antibody in inflammatory model mice. The mRNA and protein expression of MIF in inflammatory lesions were proved by RT-PCR and immunohistochemistry. The model mice were injected with 3.7 MBq of each agent and killed at 24, 48 and 72 hrs after injection. Whole-body images were obtained with storage phosphor screen. The organs, blood, abscesses muscles were removed, weighed and counted with a γ counter. The percentage of uptake by organs and per gram tissues and abscess/normal tissue (%ID/g) concentration ratios were calculated. The abscesses in mice were well visualized from 24 hrs. The target-to-non-target (T/NT) ratios were 6.71 ± 1.09 (24 hrs), 8.57 ± 0.81 (48 hrs) and 11.41 ± 0.37 (72 hrs) for 131I-labelled anti-MIF McAb group; while in control group of 131I-IgG, T/NT ratios were 4.65 ± 0.63 (24 hrs), 6.44 ± 0.60 (48 hrs) and 8.23 ± 0.35 (72 hrs) (P < 0.05). MIF mRNA expression was threefold increased in inflammatory tissues at 24 hrs compared with normal tissues, and twofold increased at 48 hrs. MIF protein expression was stronger in the inflammatory tissues at 48 hrs after focal inflammation occurred. Our findings suggest that the 131I-labelled anti-MIF McAb appears to be more specific and suitable than 131I-labelled IgG for targeting focal inflammation, which means MIF can be used as a better marker of inflammatory detection.

Genetic Requirements for Klebsiella pneumoniae -Induced Liver Abscess in an Oral Infection Model

Klebsiella pneumoniae is the predominant pathogen of primary liver abscess. However, our knowledge regarding the molecular basis of how K. pneumoniae causes primary infection in the liver is limited. We established an oral infection model that recapitulated the characteristics of liver abscess and conducted a genetic screen to identify the K. pneumoniae genes required for the development of liver abscess in mice. Twenty-eight mutants with attenuated growth in liver or spleen samples out of 2,880 signature-tagged mutants that produced the wild-type capsule were identified, and genetic loci which were disrupted in these mutants were identified to encode products with roles in cellular metabolism, adhesion, transportation, gene regulation, and unknown functions. We further evaluated the virulence attenuation of these mutants in independent infection experiments and categorized them accordingly into three classes. In particular, the class I and II mutant strains exhibited significantly reduced virulence in mice, and most of these strains were not detected in extraintestinal tissues at 48 h after oral inoculation. Interestingly, the mutated loci of about one-third of the class I and II mutant strains encode proteins with regulatory functions, and the transcript abundances of many other genes identified in the same screen were markedly changed in these regulatory mutant strains, suggesting a requirement for genetic regulatory networks for translocation of K. pneumoniae across the intestinal barrier. Furthermore, our finding that preimmunization with certain class I mutant strains protected mice against challenge with the wild-type strain implied a potential application for these strains in prophylaxis against K. pneumoniae infections.

Minocycline Modulates Neuroinflammation Independently of Its Antimicrobial Activity in Staphylococcus aureus-Induced Brain Abscess

Minocycline exerts beneficial immune modulatory effects in several noninfectious neurodegenerative disease models; however, its potential to influence the host immune response during central nervous system bacterial infections, such as brain abscess, has not yet been investigated. Using a minocycline-resistant strain of Staphylococcus aureus to dissect the antibiotic's bacteriostatic versus immune modulatory effects in a mouse experimental brain abscess model, we found that minocycline significantly reduced mortality rates within the first 24 hours following bacterial exposure. This protection was associated with a transient decrease in the expression of several proinflammatory mediators, including interleukin-1beta and CCL2 (MCP-1). Minocycline was also capable of protecting the brain parenchyma from necrotic damage as evident by significantly smaller abscesses in minocycline-treated mice. In addition, minocycline exerted anti-inflammatory effects when administered as late as 3 days following S. aureus infection, which correlated with a significant decrease in brain abscess size. Finally, minocycline was capable of partially attenuating S. aureus-dependent microglial and astrocyte activation. Therefore, minocycline may afford additional therapeutic benefits extending beyond its antimicrobial activity for the treatment of central nervous system infectious diseases typified by a pathogenic inflammatory component through its ability to balance beneficial versus detrimental inflammation.

Effect of Recombinant Murine Granulocyte Colony-Stimulating Factor with or without Fluoroquinolone Therapy on Mixed-Infection Abscesses in Mice

The aim of the study was to determine if immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (G-CSF) improves the efficacy of trovafloxacin or moxifloxacin in abscesses containing Bacillus fragilis ATCC 23745 and different Escherichia coli strains varying in virulence. Treatment of mice inoculated with 10(7) CFU B. fragilis and 10(5) CFU low-virulence E. coli with either trovafloxacin (150 mg/kg/day every 24 hours, days 3 to 7) or moxifloxacin (96 mg/kg/day every 12 hours, days 3 to 7), significantly reduced the number of B. fragilis to 6.9 +/- 0.35 and 5.8 +/- 0.10 and that of E. coli to 4.9 +/- 0.09 and 4.2 +/- 0.07 log CFU/abscess for trovafloxacin and moxifloxacin, respectively, compared to controls (B. fragilis 8.7 and E. coli 7.4 log CFU/abscess) on day 8. Also, moxifloxacin was more potent than trovafloxacin. Addition of G-CSF prophylaxis (1 mug once on day -1) or therapy (1 mug/day on days 3 to 7) to fluoroquinolone treatment did not improve the efficacy of fluoroquinolone therapy alone. The effect of moxifloxacin with or without G-CSF prophylaxis on abscesses with a virulent hemolytic E. coli strain was also studied. In moxifloxacin-treated mice, 75% survived infection compared to 10% of controls. Combining moxifloxacin with G-CSF prophylaxis significantly decreased survival (30%) compared to moxifloxacin alone. In addition, G-CSF prophylaxis resulted in a threefold (E. coli) to 100-fold (B. fragilis) increased outgrowth in the abscesses of surviving mice. In conclusion, the addition of G-CSF to a fluoroquinolone is not advisable since, depending on the virulence of the E. coli strains, this might detrimentally influence the outcome of therapy.

Monitoring photodynamic therapy of localized infections by bioluminescence imaging of genetically engineered bacteria

The increasing occurrence of multi-antibiotic resistant microbes has led to the search for alternative methods of killing pathogens and treating infections. Photodynamic therapy (PDT) uses the combination of non-toxic dyes and harmless visible light to produce reactive oxygen species that can kill mammalian and microbial cells. Although the photodynamic inactivation of bacteria has been known for over a hundred years, its use to treat infections has not been much developed. This may be partly due to the difficulty of monitoring the effectiveness of PDT in animal models of infection. In order to facilitate this monitoring process, we have developed a procedure that uses bioluminescent genetically engineered bacteria and a light sensitive imaging system to allow real-time visualization of infections. When these bacteria are treated with PDT in vitro, the loss of luminescence parallels the loss of colony-forming ability. We have developed several models of infections in wounds and soft-tissue abscesses in mice that can be followed by bioluminescence imaging. The size and intensity of the infection can be sequentially monitored in a non-invasive fashion in individual mice in real-time. When photosensitizers are introduced into the infected tissue followed by illumination with red light, a light-dose dependent loss of luminescence is seen. If the bacterium is invasive, the loss of luminescence correlates with increased survival of the mice, whilst animals in control groups die of sepsis within five days. Healing of the PDT treated wounds is not impaired and may actually be improved. This approach can allow many animal models of localized infections to be accurately monitored for efficacy of treatment by PDT.

Experimental Abscess Formation Caused by Human Dental Plaque

Human dental plaque consists of a wide variety of microorganisms, some of which are believed to cause systemic infections, including abscesses, at various sites in the body. To confirm this hypothesis experimentally, we examined the abscess-forming ability of native dental plaque in mice, the microbial features of the infectious locus produced by the plaque, and the anti-phagocytic property of microbial isolates. Aliquots of a suspension of supragingival dental plaque containing 6 x 10(6) colony-forming unit of bacteria were injected subcutaneously into the dorsa of mice. Abscess formation was induced in 76 of 85 mice using ten different plaque samples. Thirteen microorganisms were isolated from pus samples aspirated from abscess lesions. The microbial composition of pus, examined in 17 of 76 abscesses, was very simple compared to that of the plaque sample that had induced the abscess. The majority of the isolates belonged to the Streptococcus anginosus group, normally a minor component of plaque samples. S. anginosus was the most frequently detected organism and the most prevalent in seven abscesses, and Streptococcus intermedius and Streptococcus constellatus were predominant in one and three abscess samples, respectively. Each isolate of S. anginosus group produced abscesses in mice, and heat-treated supragingival dental plaque influenced the abscess-forming ability of S. anginosus isolate. These isolates possessed a high antiphagocytic capacity against human polymorphonuclear leukocytes. Our results suggest that human supragingival dental plaque itself is a source of the infectious pathogens that cause abscess formation.

A novel exopolysaccharide from a clinical isolate of Prevotella nigrescens: purification, chemical characterization and possible role in modifying human leukocyte phagocytosis

Prevotella nigrescens, a gram-negative black-pigmented anaerobic rod, has frequently been isolated from periodontitis and periapical periodontitis lesions. We have isolated an exopolysaccharide-producing P. nigrescens, strain 22, from a chronic periodontitis lesion. The purpose of this study was to determine the chemical composition and function of the exopolysaccharide associated with this clinical isolate. The chemical composition and structure of the purified exopolysaccharide from strain 22 were determined by high performance liquid chromatography and methylation analysis. To define the biological function of this exopolysaccharide, a chemically induced exopolysaccharide nonproducing mutant, strain 328, which was derived from strain 22, was established. The biological effects of exopolysaccharide were determined by comparing the ability of strain 22, strain 328 or heat-killed strain 22 to form abscesses in mice and to interfere with the phagocytic activity of peripheral blood polymorphonuclear leukocytes. Chemical analysis showed that isolated exopolysaccharide consisted of mannose (521.6 microg/mg), glucose (25.6 microg/mg), fructose (65.8 microg/mg), galactose (12.5 microg/mg), arabinose (6.2 microg/mg), xylose (3.2 microg/mg), rhamnose (6.1 microg/mg), and ribose (0.6 microg/mg). Methylation analysis of exopolysaccharide indicated that the linkages of mannose were primarily (1-->2, 1-->6) (1-->2) (1-->6), and (1-->3). Strain 22 and, to a lesser extent, its heat-killed counterpart induced greater abscess formation in mice than strain 328, even though the enzymatic profile of strain 22 was similar to that of strain 328. The ability of strain 328 to induce abscess formation was restored by adding the purified exopolysaccharide isolated from strain 22 to the cell suspension of strain 328. Exopolysaccharide alone failed to induce abscess formation in mice. Further, strain 328 but not the untreated or heat-killed strain 22, was phagocytosed by polymorphonuclear leukocytes both in the presence and in the absence of opsonic factors. The results suggest that these polysaccharides isolated from strain 22, which primarily consisted of mannose, may play a key role in the development of the chronic inflammatory lesion from which this strain was isolated.

In Chronic Inflammation, There Exists an IL-6 Independent Pathway for the Induction of Hepcidin.

The iron regulatory hormone hepcidin is presumed to be the mediator of anemia of inflammation (AI). Patients with hepatic adenomas producing large amounts of hepcidin had severe AI that resolved when the tumors were resected (Weinstein et al, 2002). Patients with disorders associated with AI and mice with acute inflammation also have increased hepcidin. However, hepcidin deficient mice do not develop hypoferremia in response to acute inflammation (Nicolas et al, 2002). We previously showed that IL-6 was necessary for the inflammatory induction of hepcidin and the development of hypoferremia in an acute turpentine model of inflammation (Nemeth et al, 2004). In order to determine whether IL-6 was necessary for the development of AI, we induced chronic peritoneal S. epidermidis abscesses in IL-6 deficient mice (19 with abscesses, 12 controls) and wild type mice with the same genetic background (16 with abscesses, 10 controls). In contrast to our previous results, both IL-6 deficient and wild type mice had a significant rise in hepcidin-1 expression (27.6 vs. 10.9-fold, respectively) but there was no difference between the groups (p=0.939 by 2-way ANOVA). Both IL-6 deficient and control mice demonstrated a similar small but significant fall in hematocrit (49% to 44% vs. 46% to 42%, p=0.538 by 2-way ANOVA) in response to the abscesses. IL-6 is not necessary for the induction of hepcidin or the development of AI in a physiological model of infection. Experiments are underway to define which other inflammatory mediators induce hepcidin.

The role of the capsule of the Streptococcus milleri group in its pathogenicity.

Study of the pathogenicity of encapsulated strains of the Streptococcus milleri group (SMG) was performed by examination of the ability to cause subcutaneous abscesses in mice and by phagocytosis and phagocytic killing of human polymorphonuclear neutrophils (PMNs) against the organisms. All 3 encapsulated isolates from patients with pneumonia or lung abscess induced abscesses in the mice; however, only 2 of 20 unencapsulated isolates from patients with lung abscess or thoracic empyema did so. The 3 encapsulated strains inhibited more phagocytosis and phagocytic killing of PMNs than the unencapsulated strains. In addition, encapsular material separated from Streptococcus constellatus RZYK001 also inhibited phagocytosis and phagocytic killing in proportion to increasing concentrations of the capsular material. These results suggest that capsular material produced by SMG might be a pathogenic factor.

Mixed infections with Porphyromonas gingivalis and Treponema denticola cause excessive inflammatory responses in a mouse pneumonia model compared with monoinfections

Periodontopathic anaerobes such as Porphyromonas gingivalis are frequently found in aspiration pneumonia and lung abscesses. However, defense mechanisms and responses to these bacterial infections in the lung in vivo remain poorly understood. The coexistence of P. gingivalis with Treponema denticola has been found at higher levels and proportions in periodontally diseased sites. We hypothesized that mixed infections with P. gingivalis and T. denticola can cause severe respiratory disease. In the present study, inflammatory responses to mono- and mixed inoculations with P. gingivalis and T. denticola in the bronchoalveolar lavage (BAL) fluid were investigated. Acute pneumonia and lung abscesses in mice with the mixed infection resulted in a 40% mortality rate within 72 h, compared with only 10% mortality for the respective monoinfections. Pulmonary clearance of P. gingivalis was delayed in the mice with mixed infections with P. gingivalis and T. denticola. Tumor necrosis factor α (TNFα) interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels from BAL fluid of mice with mixed infections at 24 h after inoculation were significantly higher than those after P. gingivalis monoinfection (TNFα: P < 0.05, Il-1β: P < 0.001, IL-6: P < 0.05). The chemokine KC level from BAL fluid of mice at 48 h ( P < 0.05) and 72 h after mixed infection was also significantly increased when compared with that after P. gingivalis monoinfection ( P < 0.001). The present study demonstrates that a mixed infection of P. gingivalis with T. denticola in mouse causes a marked bronchopneumonia and lung abscess in the mouse model.

In vitro and in vivo Antibacterial Activities of Telithromycin

Background: Telithromycin is one of the ketolides, characterised by a 3-keto group instead of L-cladinose and a C₁₁–C₁₂ carbamate link by an alkyl chain to a pyridinum and imidazolium ring side chain. We evaluated in vitro and in vivo antibacterial activities of telithromycin against gynaecological pathogens. Methods: In the vitro study, the antibacterial activity of telithromycin against 180 isolates (isolated in the year 2000) of Streptococcus agalactiae (n = 33), Enterococcus faecalis (n = 22), Neisseria gonorrhoeae (n = 30), Peptostreptococcus anaerobius (n = 20), Finegoldia magna (n = 20), Bacteroides fragilis (n = 25) and Prevotella bivia (n = 30) was compared with that of erythromycin A, clarithromycin, azithromycin, ampicillin and levofloxacin. In the in vivo study, the efficacy of telithromycin was evaluated using experimental intra-abdominal abscesses in mice caused by B. fragilis (minimum inhibitory concentration of telithromycin 0.5 mg/l). Results: In the in vitro study, telithromycin inhibited more than 50% of clinical isolates of S. agalactiae, E. faecalis, N. gonorrhoeae, P. anaerobius, F. magna, B. fragilis and P. bivia at concentrations of 0.016, 0.063, 0.063, 0.032, 0.032, 0.5 and 0.25 mg/l, respectively. Telithromycin inhibited more than 90% of these clinical isolates at concentrations of 0.016, 4, 0.125, 0.063, 0.063, 4 and 1 mg/l, respectively. In the in vivo study, telithromycin inhibited abscess formation and significantly decreased viable cell counts in abscesses in comparison with the untreated group. Conclusions: These in vitro and in vivo antibacterial activities suggest that telithromycin could be a potential candidate for the treatment of bacterial infections complicated by chlamydial infection.

Effect of a single percutaneous abscess drainage puncture and imipenem therapy, alone or in combination, in treatment of mixed-infection abscesses in mice.

The importance of supplementary imipenem therapy after a single percutaneous abscess drainage puncture was studied in a mouse model of established mixed-infection abscesses. Animals were treated for 3 days with daily dosing regimens of 384 to 1,536 mg/kg of body weight that took into account the short half-life of this antibiotic in mice. Imipenem therapy in conjunction with abscess drainage was significantly better than drainage alone in reducing the Escherichia coli and Bacteroides fragilis counts in the mixed infections. Furthermore, the killing of B. fragilis by the combination of imipenem therapy and abscess drainage was significantly better than that by imipenem treatment alone. The maximum reductions in E. coli and B. fragilis counts were 1.1 and 2.2 log(10) CFU/abscess, respectively. In contrast, the in vitro activity of imipenem was significantly better (maximum reduction, > or =6.2 log(10) CFU/ml) against mixed cultures of the same strains even when bacterial numbers similar to those found in the abscesses were used. Comparable in vivo activity was achieved only when treatment was started 30 min before inoculation (reduction for both strains, > or =6.1 log(10) CFU/abscess), but this killing was significantly diminished if the start of treatment was delayed until > or =12 h after inoculation. Imipenem concentrations in abscess tissue reached levels above the MIC for E. coli for >60% of the dosing interval. Possible reasons for the reduced activity of imipenem in vivo are discussed, and we conclude that standard susceptibility tests overestimate the efficacy of this antibiotic against the organisms present in these abscesses.