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PubMed2005

Experimental comparison of excision and swabbing microbiological sampling methods for carcasses.

Bovine sides, ovine carcasses, and porcine carcasses were individually inoculated by dipping in various suspensions of a marker organism (Escherichia coli K-12 or Pseudomonas fluorescens), alone or in combination with two meat-derived bacterial strains, and were sampled by two standard methods: cotton wet-dry swabbing and excision. The samples were examined for bacterial counts on plate count agar (PCA plate counts) and on violet red brilliant green agar (VRBGA plate counts) by standard International Organization for Standardization methods. Average bacterial recoveries by swabbing, expressed as a percentage of the appropriate recoveries achieved by excision, varied widely (2 to 100%). Several factors that potentially contributed to relatively low and highly variable bacterial recoveries obtained by swabbing were investigated in separate experiments. Neither the difference in size of the swabbed area (10, 50, or 100 cm2 on beef carcasses) nor the difference in time of swabbing (20 or 60 min after inoculation of pig carcasses) had a significant effect on the swabbing recoveries of the marker organism used. In an experiment with swabs preinoculated with the marker organism and then used for carcass swabbing, on average, 12% of total bacterial load was transferred inversely (i.e., from the swab to the carcass during the standard swabbing procedure). In another experiment, on average, 14% of total bacterial load was not released from the swab into the diluent during standard swab homogenization. Use of custom-made swabs with abrasive butts, around which metal pieces of pan scourers were wound, markedly increased PCA plate count recoveries from noninoculated lamb carcasses at commercial abattoirs compared with cotton swabs. In spite of the observed inferiority of the cotton wet-dry swabbing method compared with the excision method for bacterial recovery, the former is clearly preferred by the meat industry because it does not damage the carcass. Therefore, further large-scale evaluation of the two carcass sampling methods has been undertaken under commercial conditions and reported separately.

Abattoirs↗

PubMed2005

Suitability of the German test method for cleaning efficacy in washer-disinfectors for flexible endoscopes according to prEN ISO 15883.

In Europe, the evaluation of processing flexible endoscopes in washer-disinfectors (WDs) is performed in compliance with prEN ISO 15883-1 which includes determination of the efficacy of the cleaning process. Recent data suggest that cleaning processes show large differences when the prEN ISO 15883-1 German test model is applied. Hence, we analysed a total of 72 experiments in order to evaluate the test method. Transparent test tubes as test pieces (length 2 m, lumen 2 mm) were contaminated with a mixture of blood and Enterococcus faecium. Three set-ups were used: WD 425 with soft water, WD 425 with hard water and WD 440 with demineralized water. WDs were set to perform the cleaning stage of the programme alone. Seven cleaning agents were used according to the manufacturers' instructions (21 cleaning processes); in addition, three cleaning processes were carried out without a cleaning agent (i.e. with water alone). Each cleaning process was assessed by means of three experiments. Suspensions of test organism had 9.2x10(10) colony-forming units (cfu)/mL E. faecium (mean of 24 processes). Controls (recovery) contained 1.0x10(6) cfu/mL E. faecium (mean of 71 experiments). Mean log(10) reduction factors (RFs) for each process, i.e. the difference in microbial loads on the control and the processed tubes, were calculated. Cleaning processes led to RFs of 0-4.1, but no process led to residual bacterial loads below the limit of detection (1.8l gcfu/mL). Standard deviations for a cleaning process were small (< or =0.6 in 79% of the processes) indicating adequate reproducibility. The test model led to reproducible results and revealed large differences between the individual processes. If a cleaning process is intended to result in a bioburden reduction (i.e. RF> or =4), the control must carry a minimum bioburden of 6.5x10(5) cfu/mL. This was achieved in 58% of the processes. However, controls with a bioburden <6.5x10(5) cfu/mL never yielded a residual bacterial load below the limit of detection. We found that the prEN ISO 15883-1 German test method is suitable to determine the cleaning efficacy in WDs and leads to reproducible and valid results.

Decontamination↗

PubMed2006

Roles of macrophages and neutrophils in the early host response to Bacillus anthracis spores in a mouse model of infection.

The development of new approaches to combat anthrax requires that the pathogenesis and host response to Bacillus anthracis spores be better understood. We investigated the roles that macrophages and neutrophils play in the progression of infection by B. anthracis in a mouse model. Mice were treated with a macrophage depletion agent (liposome-encapsulated clodronate) or with a neutrophil depletion agent (cyclophosphamide or the rat anti-mouse granulocyte monoclonal antibody RB6-8C5), and the animals were then infected intraperitoneally or by aerosol challenge with fully virulent, ungerminated B. anthracis strain Ames spores. The macrophage-depleted mice were significantly more susceptible to the ensuing infection than the saline-pretreated mice, whereas the differences observed between the neutropenic mice and the saline-pretreated controls were generally not significant. We also found that augmenting peritoneal neutrophil populations before spore challenge did not increase resistance of the mice to infection. In addition, the bacterial load in macrophage-depleted mice was significantly greater and appeared significantly sooner than that observed with the saline-pretreated mice. However, the bacterial load in the neutropenic mice was comparable to that of the saline-pretreated mice. These data suggest that, in our model, neutrophils play a relatively minor role in the early host response to spores, whereas macrophages play a more dominant role in early host defenses against infection by B. anthracis spores.

Animals↗

PubMed2005

Relationships among bacteria, upper airway, lower airway, and systemic inflammation in COPD.

STUDY OBJECTIVE: The upper and lower airways are continuous. While upper airway symptoms are common in COPD patients, with accumulating evidence to suggest increased nasal inflammation, the relationships among upper airway, lower airway, and systemic inflammatory indexes have not been studied. We aimed to confirm that there is heightened nasal inflammation in COPD patients, to test the hypothesis that the degree of upper airway inflammation relates to the degree of lower airway inflammation, and to investigate the underlying associations with bacterial carriage and the systemic inflammatory response. DESIGN: Prospective cohort study. SETTING: Outpatient Department, London Chest Hospital, London, UK. PARTICIPANTS: Forty-seven patients with COPD and 12 control subjects of similar age, sex, and smoking status. MEASUREMENTS: Serum, nasal wash fluid, and sputum samples were obtained from 47 stable patients with COPD for the analysis of inflammatory indexes and bacterial colonization. Nasal wash fluid specimens were obtained from 12 control subjects. RESULTS: COPD patients had an increased nasal interleukin (IL)-8 concentration compared to control subjects (difference, 97.2 pg/mL; p = 0.009). The nasal IL-8 concentration in COPD patients correlated with that in sputum (r = 0.30; p = 0.039). In both the upper and lower airways of patients with COPD, the IL-8 concentration was associated with indexes of bacterial colonization. Patients colonized with a sputum potentially pathogenic microorganism had a higher total nasal bacterial load (difference, 1.5 log cfu/mL; p = 0.016). We did not find significant relationships between the degree of upper or lower airway inflammation, or bacterial carriage, and the systemic inflammatory response. CONCLUSIONS: COPD is associated with an increased nasal concentration of the neutrophil chemoattractant protein IL-8, the degree of which reflects that present in the lower airway. A relationship between lower airway bacterial colonization, postnasal drip, and higher nasal bacterial load may suggest a mechanism underlying this finding. This study is the first to report a correlation between the degree of upper and lower airway inflammation in COPD.

Aged↗

PubMed2005

Effect of a stannous fluoride dentifrice on the sulcular microbiota: a prospective cohort study in subjects with various levels of periodontal inflammation.

OBJECTIVES: To assess the effects of an experimental 0.454% stannous fluoride (SnF2) dentifrice on the oral sulcular microbiota in patients with various stages of oral diseases using checkerboard DNA-DNA hybridization. MATERIAL AND METHODS: In the present one-month, single center, single product, prospective cohort trial, 37 adults (mean age 37.6) were assigned to one of four oral health condition cohorts with seven to 10 subjects each: 1. mild gingivitis, 2. marked generalized gingivitis to moderate periodontitis, 3. caries-prone and 4. treated moderate to advanced chronic periodontitis in supportive periodontal care. All four groups were asked to use the test dentifrice and a power toothbrush twice a day for one minute during a four-week test period. Before and after the trial period, Plaque Indices (PII, Silness and Löe, 1964) and Gingival Indices (GI, Löe and Silness, 1963) were recorded. Subgingival plaque samples were collected from all patients at Baseline, as well as after two and four weeks. These samples were analyzed for content of 40 bacterial species using checkerboard DNA-DNA hybridization. RESULTS: As a result of the only one minute brushing with the stannous fluoride dentifrice, the mean PII at Baseline was significantly lower (p < 0.05) from the mean PII at four weeks. No statistically significant differences were found between premolar and molar mean values. Moreover, no statistically significant differences were found between the mean GI at Baseline and at four weeks. The microbiological analysis showed that at baseline subjects in groups 2 and 4 had significantly higher bacterial loads of bacteria than groups 1, and 3 (i.e. A. actinomyctemcomitans P. gingivalis, T. forsythia, and T. denticola. Over the study period, the total bacterial load did not change in groups 2, 3 and 4. In groups 1 and 3, however, an increase in the loads of Streptococci spp. were noticed (p < 0.05) including S. mitis, S. intermedius, and S. sanguis (p < 0.01) suggesting an increase in the presence of early colonizing and health associated bacteria. CONCLUSION: One minute brushing with a 0.454% stannous fluoride dentifrice did--after four weeks--not affect the subgingival microbial profiles in patients with moderate periodontitis and treated moderate to advanced periodontitis. However, the sulcular microbial profiles of mild gingivitis and caries-prone patients were affected, indicating a shift towards a gingival health associated microbiota in the sulcular region of patients not affected by attachment loss. RUNNING HEAD: Effect of stannous fluoride on sulcular microbiota.

Adult↗

PubMed2001

Screening evaluation of an ionized nanocrystalline silver dressing in chronic wound care.

The successful topical treatment of chronic wounds requires adequate debridement, bacterial balance, and moisture balance. An ionized nanocrystalline silver dressing was evaluated through an uncontrolled, prospective study of a case series of 29 patients with a variety of chronic nonhealing wounds. The four arms of the study included nine patients with foot ulcers, six patients with venous stasis ulcers, two patients with pressure ulcers, and 12 patients with miscellaneous wounds. All wounds were assessed for the usual signs of clinical infection, with most of these parameters being measured and recorded. Microbiologically, bacterial load was determined via quantitative biopsies and semi-quantitative swabs. In general, the results showed a marked clinical improvement for the majority of wounds treated with the dressing. Among improved parameters included decreased exudate and decreased purulence. The quantitative bacterial biopsies did not show any decrease in organism numbers, although the semi-quantitative swabs indicated a decrease in the wound surface bacterial loading. This was indicative of the dressing's ability to reduce surface bacteria and achieve an element of bacterial balance in the superficial dermal compartment. The proposed mechanism of action for this ionized nanocrystalline based dressing is through bacterial and moisture balance within the superficial wound space compartment.

Algorithms↗

PubMed1994

Bacterium-host cell interactions at the cellular level: fluorescent labeling of bacteria and analysis of short-term bacterium-phagocyte interaction by flow cytometry.

Flow cytometry is a potentially powerful tool for analyzing the interactions of facultative intracellular bacteria and macrophages on a cellular level, particularly when fluorochromes are used to label the bacteria. We labeled Listeria monocytogenes and Salmonella typhimurium with a lipophilic dye, PKH-2, and used flow cytometry to investigate phagocytosis by J774A.1 cells and short-term bacterial survival. Labeled and unlabeled bacteria were identical in terms of viability, growth kinetics, and survival within macrophages, although recovery per macrophage was much greater for L. monocytogenes than for S. typhimurium. Using L. monocytogenes as a prototypical facultative intracellular bacterium, we estimated bacterial survival during phagocytosis on the basis of linear fluorescence measurements of infected J774A.1 cells and recovery of L. monocytogenes from sorted cells. The lower percentage of surviving L. monocytogenes in macrophages containing higher bacterial loads indicated the accumulation of nonviable bacteria within phagocytes. Removal of the external source of viable bacteria by washes and gentamicin treatment reduced the percentage of surviving intracellular L. monocytogenes to a baseline level, and all baseline levels were similar, regardless of bacterial load. Listeria enrichment recoveries, derived from individually sorted J774A.1 cells, demonstrated the heterogeneity of macrophages in intracellular bacterial survival, especially within heavily infected cells. These results indicated that survival of L. monocytogenes was dependent on the adaptations of a small fraction of bacteria within a population of macrophages which permit intracellular growth.

Adaptation, Physiological↗

PubMed1991

Helicobacter pylori in gastric biopsy specimens. Comparison of culture, modified giemsa stain, and immunohistochemistry. A retrospective study.

Antral biopsy specimens of 302 different endoscopic investigations of 200 patients with non-ulcer dyspepsia were studied for the presence of Helicobacter pylori in order to determine the most sensitive detection method. Part of the biopsy was cultured, and part stained using a modification of the Giemsa stain, and with an immunoperoxidase technique using a polyclonal rabbit anti-H. pylori antiserum. Cross-reactivity of this antiserum with other Campylobacter species was minimal. Material from 244 investigations was studied using all three detection methods. Culture was positive in 44 per cent, Giemsa in 78 per cent, and immunoperoxidase in 89 per cent of these biopsy specimens. Only five positive Giemsa stains with negative immunoperoxidase stain were found, whereas in 32 cases a negative Giemsa stain with a positive immunoperoxidase stain was seen. In the latter cases, the bacterial load was very low. The specimens revealed bacteria only sporadically, always confined to the deep layers of the gastric pits. Culture results correlated significantly with the bacterial load observed in the Giemsa stain. It is concluded that culture of H. pylori is the least sensitive detection method, whereas immunoperoxidase staining is the most sensitive. For daily practice the modified Giemsa stain, however, appears to be sufficient to diagnose the presence of the micro-organism.

Adolescent↗

PubMed2004

Estrogen receptor-alpha deficiency promotes increased TNF-alpha secretion and bacterial killing by murine macrophages in response to microbial stimuli in vitro.

In this series of studies, we determined the potential role of intracellular estrogen receptors (ER), ERalpha and ERbeta, on macrophage function in response to bacterial stimuli. The sex hormone 17beta-estradiol (E(2)) and ER have been shown to modulate inflammatory responses as well as T helper cell type 1 (TH1)/TH2 responses. The mechanisms E(2) and its receptors use to alter these immune functions remain largely unknown. ERalpha and ERbeta possess complex actions in tissues where they are expressed. We have characterized the receptor repertoire of murine dendritic cells and thioglycollate-elicited peritoneal macrophages (PM). Both cell types express mRNA for ERalpha. Neither cell type expressed detectable amounts of ERbeta mRNA, as determined by reverse transcriptase-polymerase chain reaction using exon-specific primers spanning each of the seven intron/exon junctions. Primary macrophages from ERalpha- and ERbeta-deficient severe combined immunodeficiency mice [ERalpha knockout (KO) and ERssKO, respectively] were used to delineate the effects and potential mechanisms via which steroid receptors modulate macrophage function. ERalpha-deficient PM exposed ex vivo to lipopolysaccharide or Mycobacterium avium exhibited significant increases in tumor necrosis factor alpha (TNF-alpha) secretion as well as reduction in bacterial load when compared with wild-type (WT) PM. In contrast, ERbeta-deficient PM possessed no significant difference in TNF-alpha secretion or in bacterial load when compared with WT littermates. These studies suggest that ERalpha, but not ERbeta, modulates murine PM function.

Animals↗

PubMed2002

Effective and culturally acceptable water storage in Zimbabwe: maintaining the quality of water abstracted from upgraded family wells.

Because domestic water can be a vehicle of disease transmission in the home, there is a need for intervention. In Zimbabwe. 60 rural households obtaining water from shallow wells were selected for a field study. A water urn was designed, pretested, and field-tested. Thirty households designated as the case group were given two water urns each to substitute for traditional water storage containers (paint containers, oil containers, etc.). The remaining 30 households served as a control group. Samples were collected twice, at two-week intervals, from the water supply source (upgraded family wells) and storage containers (water urn or traditional containers) of each household (228 samples). Total coliform bacteria and fecal coliform bacteria were enumerated with the membrane filtration technique. A pretest of the water urn design showed a decline in turbidity that corresponded with a decline in bacterial counts. Wells supplying the case households had higher bacterial counts than those supplying the control households, but bacterial loads in the water urns were significantly lower than those observed in the corresponding supply wells (paired t-test: t = 3.97, df = 55, p < .01). Bacterial loads in traditional containers were similar to those observed in the supply wells (paired t-test; t = 0.2, df = 57, p > .05). The case group eagerly substituted water urns for traditional containers. The use of water urns was found to prevent or to reduce further contamination of well water after collection.

Disease Transmission, Infectious↗

PubMed2002

Reduction of Yersinia enterocolitica load in deliberately inoculated blood: the effects of blood prestorage temperature and WBC filtration.

BACKGROUND: Yersinia enterocolitica is known to cause severe infections in patients who receive transfusions. STUDY DESIGN AND METHODS: The aim of the study was to define the best strategy for reducing the bacterial load in blood that was deliberately contaminated with Y. enterocolitica by combining prestorage temperature and WBC filtration with conditions of blood processing close to those applied in blood banks. RESULTS: The effects of three prestorage temperatures (4 degrees C, 20 degrees C, 37 degrees C) were evaluated at various times after infection. The best reduction of bacterial load was achieved after 3 hours at 20 degrees C. In further experiments, conducted according to the former specifications, filtration of whole blood from eight and six donors with an inoculum of 100 and 500 to 1000 CFUs per mL, respectively, resulted in a total inhibition of bacterial growth up to 42 days after infection. After fractionation of blood components, in contrast to plasma and RBCs, filtration was shown to reduce dramatically the bacterial growth in buffy coats, demonstrating that the antibacterial effect of filtration was supported by the removal of infected WBCs from blood samples. CONCLUSION: These results provide support for the systematic use of blood filtration in the preparation of blood components to prevent Y. enterocolitica infection of patients receiving transfusions.

Blood Bactericidal Activity↗

PubMed1992

Differential myelopoietic responsiveness of BALB/c (Itys) and C.D2 (Ityr) mice to lipopolysaccharide administration and Salmonella typhimurium infection.

Inheritance of the Ityr or the Itys allele of the Ity murine gene confers resistance or increased susceptibility, respectively, to Salmonella typhimurium infection. Recent studies have documented that Ity gene expression may determine net intracellular replication of S. typhimurium by modulating macrophage function. The purpose of this study was to determine if Ity gene expression modulated macrophage stem cell proliferation as well. To detect possible Ity-associated alterations in macrophage stem cell proliferation during endotoxin challenge or S. typhimurium infection, the congenic strain pair BALB/c (Itys) and C.D2-Idh-1, Pep-3 N20F8 (Ityr) were injected intraperitoneally with 25 micrograms of bacterial lipopolysaccharide (LPS) or approximately 10(3) S. typhimurium, and myelopoiesis was evaluated. At 72 h after LPS injection, both BALB/c and C.D2 mice developed comparable degrees of bone marrow hypocellularity and splenomegaly, and cell sizing profiles indicated a normal response to a single injection of LPS in both strains of mice. Although an inhibitor to colony-stimulating factor activity was detected in the sera and plasma of C.D2 mice, the number of myeloid stem cells cultured from the bone marrow and spleen of each mouse strain were comparable. S. typhimurium infection resulted in earlier symptoms, a larger bacterial load, a higher mortality rate, and a greater bone marrow hypocellularity and splenomegaly in BALB/c mice compared with those in C.D2 mice. Despite a dramatic increase in bacterial load, a decrease in both bone marrow and splenic myeloid stem cell numbers was noted in BALB/c mice, while stem cell numbers remained constant in C.D2 mice between days 3 and 5 and increased dramatically at day 7 after infection. These data suggest that BALB/c and C.D2 mice may exhibit a divergent myelopoietic response to S. typhimurium infection. It appears that a paradoxical failure of myelopoiesis in Itys mice during S. typhimurium infection may contribute to the observed increase in mortality.

Animals↗

PubMed2000

Reduced formation of granulomata in gamma(delta) T cell knockout BALB/c mice inoculated with Mycobacterium avium subsp. paratuberculosis.

The role of gamma(delta) T cells in the bovine immune response to Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) infection is poorly understood. Accordingly, using BALB/c mice that are innately susceptible to M. paratuberculosis, we compared wild-type and gamma(delta) T cell knockout BALB/c mice to study the protective roles of gamma(delta) T cells in M. paratuberculosis infection. Ten-week-old mice were inoculated intraperitoneally with either a low dose (4 x 10(6) colony-forming units [CFU]/mouse) or a high dose (4 x 10(9) CFU/mouse) of M. paratuberculosis strain ATCC 19698. Histopathologic and morphometric examinations showed reductions in the number and area of granulomatous lesions in the liver of the knockout mice at 18 weeks after inoculation with either the low or the high dose of the mycobacteria. Furthermore, at 18 weeks after inoculation, the bacterial load in the spleens of the knockout mice inoculated with the high dose was significantly lower than that of wild-type mice. No differences were found in bacterial load between the knockout and the wild-type mice in the low-dose groups. In contrast, in the livers of wild-type mice inoculated with either the low or high mycobacterial dose, increased areas of epithelioid granulomata were observed and the granulomata became disseminated widely during the experimental period. These findings in model mice suggest that gamma(delta) T cells, rather than restricting mycobacterial growth, may play a crucial role in development of epithelioid granulomata similar to those seen consistently in bovine paratuberculosis. The results of this study may have relevance to our understanding of the pathogenesis of paratuberculosis in ruminants, in which a prominent number of gamma(delta) T cells exist in the lymphoid system.

Animals↗

PubMed2006

Pre-treatment of central venous catheters with the cathelicidin BMAP-28 enhances the efficacy of antistaphylococcal agents in the treatment of experimental catheter-related infection.

An in vitro antibiotic susceptibility assay for Staphylococcus aureus biofilms developed on 96-well polystyrene tissue culture plates was performed to elucidate the activity of the 27 residues cathelicidin peptide BMAP-28, quinupristin/dalfopristin (Q/D), linezolid, and vancomycin. Efficacy studies were performed in a rat model of staphylococcal CVC infection. Silastic catheters were implanted into the superior cava. Twenty-four hours after implantation the catheters were filled with BMAP-28. Thirty minutes later rats were challenged via the CVC with 1.0x10(6) CFU of S. aureus strain Smith diffuse. Administration of antibiotics into the CVC at a concentration equal to the MBC observed using adherent cells, or at a much higher concentration (1024 microg/mL) began 24 h later. The inhibition activities of all antibiotics against adherent bacteria were at least two-four-fold lower that against freely growing cells. When antibiotics were used in BMAP-28 pre-treated wells, they showed higher activities. The in vivo studies showed that when CVCs were pre-treated with BMAP-28 or with a high dose of antibiotics, biofilm bacterial load was reduced from 10(7) to 10(3) CFU/mL and bacteremia reduced from 10(3) to 10(1) CFU/mL. When CVCs were treated with both BMAP-28 and antibiotics, biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected. These results suggest that CVC pre-treated with BMAP-28 represents an attractive choice for the treatment of device-related infections caused by staphylococci.

Animals↗

PubMed1982

Anaerobic and aerobic bacteria in secretions of prostate and seminal vesicles of infertile men.

A cytological and bacteriological study was made of prostatic (EPS) and vesicular (EVS) secretions from 123 infertile men who were suspected of having chronic genital tract inflammation and from 31 men with premature ejaculation (1,12,16). In the microbiological investigations samples were inoculated within 10 min on various culture media and incubated under both aerobic and anaerobic conditions. Bacterial loads of more than 10,000 colony-forming units of a single species or genus per milliliter of EPS or EVS were considered to be pathological. In the infertile subjects with proven inflammation of the seminal accessory glands, the EPS and the EVS that gave positive cultures and had bacterial loads defined as pathological contained large numbers of anaerobic or microaerophilic organisms (EPS: 51 of the 63 bacterial strains found, congruent to 81%; EVS: 19 of the 20 bacterial strains found, congruent to 95%).

Adult↗

PubMed2004

Anti-inflammatory response is associated with mortality and severity of infection in sepsis.

Using a murine model of sepsis, we found that the balance of tissue pro- to anti-inflammatory cytokines directly correlated with severity of infection and mortality. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Liver tissue was analyzed for levels of IL-1beta, IL-1 receptor antagonist (IL-1ra), tumor necrosis factor (TNF)-alpha, and soluble TNF receptor 1 by ELISA. Bacterial DNA was measured using quantitative real-time PCR. After CLP, early predominance of proinflammatory cytokines (6 h) transitioned to anti-inflammatory predominance at 24 h. The elevated anti-inflammatory cytokines were mirrored by increased tissue bacterial levels. The degree of anti-inflammatory response compared with proinflammatory response correlated with the bacterial concentration. To modulate the timing of the anti-inflammatory response, mice were treated with IL-1ra before CLP. This resulted in decreased proinflammatory cytokines, earlier bacterial load, and increased mortality. These studies show that the initial tissue proinflammatory response to sepsis is followed by an anti-inflammatory response. The anti-inflammatory phase is associated with increased bacterial load and mortality. These data suggest that it is the timing and magnitude of the anti-inflammatory response that predicts severity of infection in a murine model of sepsis.

Animals↗

PubMed2003

Pseudomonas aeruginosa alginate is refractory to Th1 immune response and impedes host immune clearance in a mouse model of acute lung infection.

Pseudomonas aeruginosa is an opportunistic respiratory pathogen that accounts for most of the morbidity and mortality in cystic fibrosis (CF) patients. In CF-affected lungs, the bacteria undergo conversion from a non-mucoid to a non-tractable mucoid phenotype, due to overproduction of alginate. The effect of alginate production on pathogenicity was investigated by using an acute lung infection mouse model that compared a non-mucoid P. aeruginosa strain, PAO1, to its constitutive alginate-overproducing derivative, Alg(+) PAOmucA22, and an alginate-defective strain, Alg(-) PAOalgD. Bacterial suspensions were instilled into the left bronchus and examined 24 and 48 h post-infection. The highest bacterial loads and the most severe lung pathology were observed with strain Alg(-) PAOalgD at 24 h post-infection, which may have been due to an increase in expression of bacterial elastase by the mutant. Significantly lower lung and spleen bacterial loads were found in the two non-mucoid (PAO1 and Alg(-) PAOalgD) groups, compared to the mucoid Alg(+) PAOmucA22 group, between 24 and 48 h post-infection. The positive correlation between lung bacteriology and lung macroscopic pathology in the Alg(+) PAOmucA22 group suggests that alginate production not only impedes pulmonary clearing, but also results in severe lung damage. Positive correlations between IL12 levels and lung macroscopic pathology, and between IL12 and IFN-gamma levels in the Alg(+) PAOmucA22 group, suggested a possible contribution of these pro-inflammatory cytokines to tissue damage. No significant differences were found between the three groups in lung cytokine responses at 24 or 48 h post-infection. However, on comparison within each group at 24 and 48 h post-infection, a significant increase in the pro-inflammatory cytokine IFN-gamma was observed. Higher ratios of IFN-gamma/IL4 and IFN-gamma/IL10, but lower IL10 levels, were also found in all three groups. These results indicate a Th1-predominated immune response in these animals. Such cytokine responses could have aided the clearance of non-mucoid P. aeruginosa, but were not sufficient to alleviate infection by the mucoid variants. Alginate production may promote survival and persistence of this pathogenic micro-organism in the lung.

Acute Disease↗

PubMed1993

Outcome of intra-abdominal infection in pigs depends more on host responses than on microbiology.

OBJECTIVE: To assess the effects of mortality of the presence and proliferation of bacteria, and the host's response to infection, in pigs with peritonitis. DESIGN: Laboratory study. SETTING: University hospital. MATERIAL: 71 Swedish Landrace pigs, 63 with peritonitis and 8 without (controls). INTERVENTIONS: Induction of peritonitis by intraperitoneal infusion of equal amounts of Escherichia coli and Bacteroides fragilis (10(9) to 10(11) bacteria/animal); sterile faeces were added in half the experiments. MAIN OUTCOME MEASURES: Microbiological events were quantified as the area under the bacterial concentration curve from 0-6 hours. Host responses were quantified with a score of 8 physiological variables measured between 4-6 hours after the induction of peritonitis. RESULTS: Of the 63 infected animals, 37 (59%) died within 6-24 hours and both the physiological response and the bacterial load were significantly higher in those that died. Logistic regression analysis with death as the dependent variable showed that the physiology score carried more predictive information than the quantification of bacterial load. CONCLUSION: The quantification of local events within the abdomen is of only limited predictive value compared with the extent of the physiological alterations.

Animals↗