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H Ceri

Publications and source records attributed to H Ceri.

At least 19 recordsLinked to original sources
PubMed2005

Quorum-sensing mutations affect attachment and stability of Burkholderia cenocepacia biofilms.

Biofilm formation in Burkholderia cenocepacia has been shown to rely in part on acylhomoserine lactone-based quorum sensing. For many other bacterial species, it appears that both the initial adherence and the later stages of biofilm maturation are affected when quorum sensing pathways are inhibited. In this study, we examined the effects of mutations in the cepIR and cciIR quorum-sensing systems of Burkholderia cenocepacia K56-2 with respect to biofilm attachment and antibiotic resistance. We also examined the role of the cepIR system in biofilm stability and structural development. Using the high-throughput MBEC assay system to produce multiple equivalent biofilms, the biomasses of both the cepI and cepR mutant biofilms, measured by crystal violet staining, were less than half of the value observed for the wild-type strain. Attachment was partially restored upon providing functional gene copies via multicopy expression vectors. Surprisingly, neither the cciI mutant nor the double cciI cepI mutant was deficient in attachment, and restoration of the cciI gene resulted in less attachment than for the mutants. Meanwhile, the cciR mutant did show a significant reduction in attachment, as did the cciR cepIR mutant. While there was no change in antibiotic susceptibility with the individual cepIR and cciIR mutants, the cepI cciI mutant biofilms were more sensitive to ciprofloxacin. A significant increase in sensitivity to removal by sodium dodecyl sulfate was seen for the cepI and cepR mutants. Flow cell analysis of the individual cepIR mutant biofilms indicated that they were both structurally and temporally impaired in attachment and development. These results suggest that biofilm structural defects might be present in quorum-sensing mutants of B. cenocepacia that affect the stability and resistance of the adherent cell mass, providing a basis for future studies to design preventative measures against biofilm formation in this species, an important lung pathogen of cystic fibrosis patients.

Anti-Bacterial Agents↗
PubMed2001

Characterization of biofilm growth and biocide susceptibility testing of Mycobacterium phlei using the MBEC assay system.

The importance of non-tuberculosis mycobacterial biofilm species in medicine, industry and the environment has recently gained attention. Our objectives were to characterize biofilm growth of Mycobacterium phlei M4, as a model of rapidly growing mycobacteria using the minimal biofilm eradication concentration (MBEC) and to compare biocide susceptibility of planktonic and biofilm organisms. Scanning electron microscopy was also carried out to observe biofilm morphology. With the exception of Sporicidin and Virkon the minimum bactericidal concentration values for all biocides tested were lower than the MBEC values. The MBEC assay system was seen to produce multiple and reproducible biofilms of M. phlei and to be a useful tool for susceptibility studies.

Anti-Bacterial Agents↗
PubMed2001

Pseudomonas aeruginosa GacA, a factor in multihost virulence, is also essential for biofilm formation.

We have investigated a potential role for GacA, the response regulator of the GacA/GacS two-component regulatory system, in Pseudomonas aeruginosa biofilm formation. When gacA was disrupted in strain PA14, a 10-fold reduction in biofilm formation capacity resulted relative to wild-type PA14. However, no significant difference was observed in the planktonic growth rate of PA14 gacA(-). Providing gacA in trans on the multicopy vector pUCP-gacA abrogated the biofilm formation defect. Scanning electron microscopy of biofilms formed by PA14 gacA(-) revealed diffuse clusters of cells that failed to aggregate into microcolonies, implying a deficit in biofilm development or surface translocation. Motility assays revealed no decrease in PA14 gacA(-) twitching or swimming abilities, indicating that the defect in biofilm formation is independent of flagellar-mediated attachment and solid surface translocation by pili. Autoinducer and alginate bioassays were performed similarly, and no difference in production levels was observed, indicating that this is not merely an upstream effect on either quorum sensing or alginate production. Antibiotic susceptibility profiling demonstrated that PA14 gacA(-) biofilms have moderately decreased resistance to a range of antibiotics relative to PA14 wild type. This study establishes GacA as a new and independent regulatory element in P. aeruginosa biofilm formation.

4-Butyrolactone↗
PubMed2001

Multidrug efflux pumps: expression patterns and contribution to antibiotic resistance in Pseudomonas aeruginosa biofilms.

Pseudomonas aeruginosa biofilms are intrinsically resistant to antimicrobial chemotherapies. At present, very little is known about the physiological changes that occur during the transition from the planktonic to biofilm mode of growth. The resistance of P. aeruginosa biofilms to numerous antimicrobial agents that are substrates subject to active efflux from planktonic cells suggests that efflux pumps may substantially contribute to the innate resistance of biofilms. In this study, we investigated the expression of genes associated with two multidrug resistance (MDR) efflux pumps, MexAB-OprM and MexCD-OprJ, throughout the course of biofilm development. Using fusions to gfp, we were able to analyze spatial and temporal expression of mexA and mexC in the developing biofilm. Remarkably, expression of mexAB-oprM and mexCD-oprJ was not upregulated but rather decreased over time in the developing biofilm. Northern blot analysis confirmed that these pumps were not hyperexpressed in the biofilm. Furthermore, spatial differences in mexAB-oprM and mexCD-oprJ expression were observed, with maximal activity occurring at the biofilm substratum. Using a series of MDR mutants, we assessed the contribution of the MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY efflux pumps to P. aeruginosa biofilm resistance. These analyses led to the surprising discovery that the four characterized efflux pumps do not play a role in the antibiotic-resistant phenotype of P. aeruginosa biofilms.

Anti-Bacterial Agents↗
PubMed2001

Cytotoxic necrotizing factor type 1-positive Escherichia coli causes increased inflammation and tissue damage to the prostate in a rat prostatitis model.

Infection of rat prostates with cytotoxic necrotizing factor type 1 (CNF1)-positive uropathogenic Escherichia coli caused more inflammation-mediated morphological and histological tissue damage than did infection with isogenic CNF1-negative mutants. These striking differences occurred despite the finding that bacterial counts for the strain pairs were indistinguishable. We conclude that CNF1 contributes to E. coli virulence in a model of acute prostatitis. To our knowledge, the results of this study provide the first demonstration of a role for any uropathogenic E. coli virulence factor in acute prostatitis.

Animals↗
PubMed2001

Interspecies biofilms of Pseudomonas aeruginosa and Burkholderia cepacia.

The leading cause of morbidity and mortality in cystic fibrosis (CF) continues to be lung infections with Pseudomonas aeruginosa biofilms. Co-colonization of the lungs with P aeruginosa and Burkholderia cepacia can result in more severe pulmonary disease than P. aeruginosa alone. The interactions between P. aeruginosa biofilms and B. cepacia are not yet understood; one possible association being that mixed species biofilm formation may be part of the interspecies relationship. Using the Calgary Biofilm Device (CBD), members of all genomovars of the B. cepacia complex were shown to form biofilms, including those isolated from CF lungs. Mixed species biofilm formation between CF isolates of P. aeruginosa and B. cepacia was readily achieved using the CBD. Oxidation-fermentation lactose agar was adapted as a differential agar to monitor mixed biofilm composition. Scanning electron micrographs of the biofilms demonstrated that both species readily integrated in close association in the biofilm structure. Pseudomonas aeruginosa laboratory strain PAO1, however, inhibited mixed biofilm formation of both CF isolates and environmental strains of the B. cepacia complex. Characterization of the soluble inhibitor suggested pyocyanin as the active compound.

Biofilms↗
PubMed2000

Rat model of experimentally induced abacterial prostatitis.

BACKGROUND: An experimental model in rats was developed to investigate the significance of mucosal integrity in abacterial prostatitis. METHODS: Ethanol was instilled into the ventral prostates of male rats to reduce mucosal integrity; dinitrobenzenesulfonic acid (DNBS) was added as an irritant to induce inflammation. Controls received no treatment, ethanol only, DNBS only, or a suspension of bacteria. After various time points, rats were sacrificed, and their prostates were assayed for gross morphology, histological appearance, and cytokine levels. RESULTS: Prostates subjected to ethanol plus DNBS showed significant inflammation, most notably after 12, 24, and 48 hr. Inflammation judged by gross and histological observations and interleukin-1beta levels correlated well at these times. Rats given only ethanol, DNBS, or no treatment, acting as negative controls, displayed little or no inflammation; rats given a bacterial suspension, acting as positive controls, showed inflammation consistent with past studies. Cytokine assays revealed raised interleukin-1beta levels in this model, while tumor necrosis factor-alpha remained at a basal level. CONCLUSIONS: The loss of an intact mucosal surface in the prostate resulted in inflammation caused by an irritant. Interleukin-1beta appears to play a role in this inflammation, while tumor necrosis factor-alpha does not.

Animals↗
PubMed2000

Giardia vaccination.

Recently, a Giardia vaccine has become commercially available in the USA for prevention of clinical signs of giardiasis and reduction of cyst shedding in dogs and cats. The vaccine is based upon the current state of knowledge of Giardia antigenicity and immunology. Here, Merle Olson, Howard Ceri and Douglas Morck describe studies that led to the development of this vaccine and subsequent efficacy studies. Immunoprophylaxis and immunotherapeutic application of the vaccine are discussed.

Animals↗
PubMed2000

Apoptosis, oxidative metabolism and interleukin-8 production in human neutrophils exposed to azithromycin: effects of Streptococcus pneumoniae.

Pathogen virulence factors and the host inflammatory response cause tissue injury associated with respiratory tract infections. The azalide azithromycin has demonstrated efficacy in the treatment of these infections. It has been demonstrated previously that induction of polymorphonuclear leucocyte (PMN) apoptosis is associated with minimization of tissue damage and inflammation in the lung. We hypothesized that, in addition to its antibacterial effects, azithromycin may promote apoptosis. The aim of the study was to determine the effects of azithromycin on PMN apoptosis, oxidative function and interleukin-8 (IL-8) production in the presence or absence of Streptococcus pneumoniae, in comparison with penicillin, erythromycin, dexamethasone or phosphate-buffered saline. Human circulating PMNs were assessed for apoptosis (by annexin V labelling and ELISA), oxidative function (by nitroblue tetrazolium reduction) and IL-8 production (by ELISA). Azithromycin significantly induced PMN apoptosis in the absence of S. pneumoniae after 1 h (10.27% +/- 1.48%, compared with 2.19% +/- 0.42% in controls) to levels similar to those after 3 h induction with tumour necrosis factor-alpha (8. 73% +/- 1.86%). This effect was abolished in the presence of S. pneumoniae. Apoptosis in PMNs exposed to the other drugs was not significantly different from that in controls. Azithromycin did not affect PMN oxidative metabolism or IL-8 production. In summary, azithromycin-induced PMN apoptosis may be detected in the absence of any effect on PMN function, and the pro-apoptotic properties of azithromycin are inhibited in the presence of S. pneumoniae.

Apoptosis↗
PubMed2000

Lipopolysaccharide entry in the damaged cornea and specific uptake by polymorphonuclear neutrophils.

Bacterial lipopolysaccharide (LPS) is an important agent of induction of ocular pathology following corneal injury or wearing of contaminated contact lenses. The mechanism of LPS uptake through the corneal epithelium is unclear, and the role played by inflammatory cells in this phenomenon has not been previously assessed. Fluorescein isothiocyanate-labeled LPS from Escherichia coli was deposited onto the abraded corneas of New Zealand White rabbits. Epifluorescence microscopy of living excised corneas revealed diffuse LPS staining in the epithelial and stromal layers only in the vicinity of the abrasion. In addition, specific cellular uptake of LPS was suggested by fluorescence staining of cells along the abrasion site. In a second series of experiments, an anti-CD18 polyclonal antibody was used to block infiltration of polymorphonuclear neutrophils (PMN) into the cornea. In these experiments, a diffuse distribution of fluorescent LPS was still observed along the abrasion, but the specific cellular uptake was abolished. The findings indicate that LPS enters the cornea via diffuse penetration at sites of injury and that specific cellular uptake of LPS occurs within the cornea via PMN which have migrated into the damaged tissue.

Animals↗
PubMed1999

The Calgary Biofilm Device: new technology for rapid determination of antibiotic susceptibilities of bacterial biofilms.

Determination of the MIC, based on the activities of antibiotics against planktonic bacteria, is the standard assay for antibiotic susceptibility testing. Adherent bacterial populations (biofilms) present with an innate lack of antibiotic susceptibility not seen in the same bacteria grown as planktonic populations. The Calgary Biofilm Device (CBD) is described as a new technology for the rapid and reproducible assay of biofilm susceptibilities to antibiotics. The CBD produces 96 equivalent biofilms for the assay of antibiotic susceptibilities by the standard 96-well technology. Biofilm formation was followed by quantitative microbiology and scanning electron microscopy. Susceptibility to a standard group of antibiotics was determined for National Committee for Clinical Laboratory Standards (NCCLS) reference strains: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Staphylococcus aureus ATCC 29213. Growth curves demonstrated that biofilms of a predetermined size could be formed on the CBD at specific time points and, furthermore, that no significant difference (P > 0.1) was seen between biofilms formed on each of the 96 pegs. The antibiotic susceptibilities for planktonic populations obtained by the NCCLS method or from the CBD were similar. Minimal biofilm eradication concentrations, derived by using the CBD, demonstrated that for biofilms of the same organisms, 100 to 1,000 times the concentration of a certain antibiotic were often required for the antibiotic to be effective, while other antibiotics were found to be effective at the MICs. The CBD offers a new technology for the rational selection of antibiotics effective against microbial biofilms and for the screening of new effective antibiotic compounds.

Alberta↗
PubMed1999

Specific mucosal immunity in the pathophysiology of bacterial prostatitis in a rat model.

Mucosal immunity was established in the rat prostate by stimulating the common mucosal system through serosal exposure of formalin-killed Escherichia coli. Immunized but not sham-immunized rats developed bacterial specific IgG and IgA in prostatic fluid, and IgA in urine. Immunized (n = 21) and sham-immunized control rats (n = 30) were challenged by transurethral injection of E. coli into the prostate ducts. Mortality, gross and microscopic pathology, tissue bacterial counts, bacterial associated immunoglobulins, and antibody titers in serum and urine were assessed at 7 days following the challenge. Increased E. coli specific immunoglobulin titers were seen in immunized rats, and E. coli, but not Proteus, found in the prostates of immunized animals were coated with IgG and IgA. Immunization protected against toxaemia and septicemia, seen as a rare complication of acute prostatitis, but did not protect against acute prostatitis, nor alter the degree of tissue damage seen in the rat model.

Acute Disease↗
PubMed1998

Serum immune response to Giardia duodenalis in experimentally infected lambs.

Twenty-three protozoan-free lambs were experimentally infected with Giardia duodenalis trophozoites at 6 weeks of age, while 24 controls lambs were not challenged. Weekly blood samples were taken and faecal cyst counts monitored for 11 weeks following infection. All experimentally infected lambs remained infected throughout the 11 week study period and control animals remained free of the parasite. Giardia-specific serum IgM, IgG and IgA antibody titers were determined weekly in 10 infected and 10 control lambs by enzyme-linked-immunosorbent assay (ELISA). Western blot analysis of serum immunoglobulins to proteins derived from four different Giardia isolates (S2, WB, D3 and NF) was performed. Weekly mean control IgM, IgG and IgA titers did not change throughout the study. Infected lambs showed no difference in IgM titers between weeks 0 and 11, but IgG and IgA titers of infected lambs differed from the preimmune (week 0) serum titer at weeks 5, 7, 9, 11 and weeks 5, 9 and 11 respectively. SDS polyacrylamide gel electrophoresis analysis showed homogeneity in the proteins of the four Giardia isolates. Antigenic proteins were also similar for all four isolates; however, the proteins recognized by IgM, IgG and IgA antibodies differed. The weak immune response of lambs to Giardia may account for the chronic nature of this disease in sheep.

Animals↗
PubMed1998

Evaluation of autologous fat implantation in the rat urinary bladder submucosa.

OBJECTIVES: Autologous fat has been used as a bulking implant material for stress urinary incontinence. There is considerable controversy as to the ultimate fate of the grafted fat. This study was conducted to determine the fate of autogenous fat implanted into the bladder of rats. METHODS: Two groups of adult female rats were studied. In the test animals (group 1, n = 20), mesenteric adipose tissue (1 mL) was harvested and homogenized with an equal weight of sterile saline. Using a 25-gauge needle, 0.5 g of saline-fat mixture was injected into the dorsal bladder neck submucosa. Control animals (group 2, n = 12) were injected with sterile saline only. A subset of animals from each group were killed after 7, 35, 105, and 1 50 days, and the bladder and urethra were fixed. The fixed tissue was examined microscopically and photographed at each follow-up period. RESULTS: Seven days after injection of fat, there was a pronounced acute inflammatory reaction with numerous polymorphonuclear leukocytes and macrophages at the site of fat injection. There was minimal inflammatory reaction at the site of saline injection. By day 35, most of the fat had been eliminated by these phagocytes because of severe acute and chronic inflammation. By day 105, the submucosa tissue of the experimental rats had returned to normal visually and to a flat surface, lacking the appearance of a sizable "bulge" as shown at days 0 and 7. Histopathologic findings were also similar to the control rats. Inflammatory cells were no longer present by day 105. CONCLUSIONS: The implantation of homogenized, autologous fat in the rat urinary bladder submucosa causes acute and chronic inflammation and fat necrosis. The severe phagocytosis at the implant sites eliminates the vast majority of the devitalized implanted fat during the first month.

Adipose Tissue↗
PubMed1998

Anti-inflammatory benefits of tilmicosin in calves with Pasteurella haemolytica-infected lungs.

OBJECTIVES: To determine whether tilmicosin alters neutrophil infiltration or function, induces neutrophil apoptosis, and affects accumulation of leukotriene B4 (LTB4) or tumor necrosis factor-alpha (TNF-alpha) in lungs of calves experimentally infected with Pasteurella haemolytica. ANIMALS: 12 weight-ranked Holstein calves. PROCEDURE: Calves were given 25% propylene glycol vehicle (n = 5) or tilmicosin (10 mg/kg of body weight; n = 6) subcutaneously, 18 hours and 15 minutes before intratracheal infection with 2 x 10(8) P haemolytica organisms. Two unmanipulated calves served as controls in some experiments. Rectal temperatures were recorded 15 minutes before, and at 3-hour intervals after infection for 24 hours. Samples obtained from bronchoalveolar lavage performed 3 and 24 hours after infection were used to assess colonization by P haemolytica, and neutrophil infiltration. Neutrophil phagocytosis of P haemolytica, membrane leakage as determined by trypan blue exclusion, oxidative function as determined by nitro blue tetrazolium reduction, and apoptosis, using electron microscopy and DNA fragmentation ELISA, were determined. SOluble TNF-alpha and LTB4 were measured from supernatants from bronchoalveolar lavage samples, using ELISA. RESULTS: Treatment with tilmicosin resulted in significant (P < 0.05) clearance of P haemolytica and neutrophil apoptosis at 3 hours, and decreased concentration of LTB4 at 24 hours. Rectal temperatures, neutrophil infiltration, phagocytosis, oxidative functions, membrane leakage, and soluble TNF-alpha concentrations were not significantly affected by tilmicosin. CONCLUSION: Tilmicosin effectively controlled P haemolytica infection, induced neutrophil apoptosis, reduced pulmonary inflammation, and did not affect neutrophil infiltration or function. CLINICAL RELEVANCE: By inducing neutrophil apoptosis, tilmicosin prevents further amplification of inflammatory injury in P haemolytica-infected lungs.

Animals↗