Reduced redox potential during growth of some Gram-negative bacteria (original) (raw)
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Infection and Immunity, 1975
The bactericidal activity, the phagocytic capacity, and the metabolic stimulation of polymorphonuclear leukocytes challenged with different strains of Escherichia coli were studied. It was found that only two strains out of 10 tested stimulated the oxygen consumption and carbohydrate metabolism of leukocytes and were readily killed by the phagocytes. The lack of killing of the other eight strains was shown to be due to absent or poor phagocytosis rather than to resistance to intracellular killing. Evidence was presented that the surface K antigen plays an important role in conferring antiphagocytic properties to some strains of E. coli. It was suggested that K antigen acts by interfering with the early step of the phagocytic process, that is, the attachment step.
Infection and Immunity
Listeria monocytogenes, a gram-positive motile bacterium which can cause severe bacterial infection in humans, is considered to be pathogenic by virtue of its ability to resist intracellular killing. Since the mechanism of intracellular survival is poorly understood, we assessed the sensitivity of L. monocytogenes to several potent antibacterial products. Phorbol myristate acetate (PMA)-stimulated polymorphonuclear cells (PMNs) produced extracellular antibacterial products which were inhibited completely by catalase, suggesting a role for oxidative agents in this process. L. monocytogenes in logarithmic (log) growth phase resisted PMA-stimulated PMN extracellular products significantly more than L. monocytogenes in stationary (stat) growth phase or Escherichia coli (three strains) in either phase of growth. The role of oxidative agents was studied further by using xanthine oxidase-xanthine, glucose oxidase-glucose, and myeloperoxidase enzyme systems to generate hydroxyl radical (. OH), hydrogen peroxide (H202), and hypochlorous acid (OCIf), respectively. L. monocytogenes in log phase resisted the antibacterial products of these enzyme systems under conditions which produced superoxide (02-) and H202 at concentrations similar to those produced extracellularly by PMA-stimulated PMNs, while stat-growth-phase L. monocytogenes and E. coli in either phase of growth were susceptible. Antibacterial activity could be blocked or inhibited by exogenous catalase (for all oxygen radical-generating systems), mannitol, or desferoxamine (for xanthine oxidase-xanthine) and alanine (for myeloperoxidase), suggesting that OH and OCI were responsible for this activity. Log-phase L. monocytogenes had 2.5-fold higher bacteria-associated catalase activity, as compared with stat-phase L. monocytogenes. These experiments, therefore, suggest that log-phase L. monocytogenes resists oxidative antibacterial agents by producing sufficient catalase to inactivate these products. This may contribute to the ability of L. monocytogenes to survive intracellularly.
Microbial Ecology in Health and Disease, 1999
Bacteroides fragilis is the Gram negative bacterium most frequently encountered in clinical infection. A range of candidate virulence determinants are implicated in the pathogenesis of this bacterium. These include encapsulating surface structures, outer membrane vesicles, fimbriae, iron-scavenging mechanisms and the production of extracellular degradative enzymes. Within strain variation of surface structure expression and antigenic variation of surface structures has been observed in both laboratory cultures 1 and pus samples 2. We have investigated the stability of expression of different antigenic types within individual strains of B. fragilis using monoclonal antibodies specific for surface polysaccharides. Our results indicate that monoclonal antibodies can be used to selectively enrich for populations expressing particular epitopes and that epitope expression in broth culture is stable on subculture. Our results indicate that the control of variation in epitope expression is at the genetic rather than the environmental level.
Acta Pathologica Microbiologica Scandinavica Series B: Microbiology, 1985
specific and hydrophobic interaction between Escherichiu coli and polymorphonuclear leukocytesinfluence of bacterial culture period. Acta path. microbiol. immunol. scand. Sect. B, 93: 125-131, 1985. The influence of culture period on mannose-specific and hydrophobic properties of the bacterial surface and on bacteria/polymorphonuclear leukocyte (PMNL) interaction was studied. Four E. coli strains, PN7 (0I:KI). ABU2 (ON:K14), CU9 (06:K14) and CU13 (08:KN) and two Sulmonellu typhimurium strains 395 MRlO and 395 MS, well characterized according to physicochemical surface properties, presence of type I fimbriae and interaction with PMNL, were used in the study. The results show that with prolonged culture period, the liability to hydrophobic interaction increases, the agglutination-strength of mannose-specific maltobionamide liposomes increases, while the agglutination-titer with guinea-pig erythrocytes remains constant. Furthermore, the mannose-specific association with and metabolic activation of PMNL is augmented, while the ingestion is unchanged. In addition, our results demonstrate differences in sensitivity between the methods used to detect exposure of mannose-specific structures on the surface of bacteria, and that the culture condition is important for bacterial surface properties. It thus appears that the culture conditions have a great influence on the surface properties of E. coli bacteria and the interaction with phagocytic cells.
A re-appraisal of the biological activity of bacteroides LPS
Journal of Medical Microbiology, 1995
Lipopolysaccharides (LPS) were extracted from seven Bacteroides strains by three different techniques: the phenol-water (PW), phenol-chloroform-petroleum (PCP) and Triton-Mg2+ methods. The strains selected included two different B. fragilis strains, one of which was grown in two different media. Yields varied between the strains, growth media and extraction technique, but generally the highest yield by weight was from the PCP method and the lowest from the PW method. The PW method was selected for the greatest amounts of carbohydrate and KDO, and the PCP method for the least. Phosphorus levels were more uniform among all extraction methods. Protein contamination was found in all Bacteroides LPS extracts, with extremely low levels in PW-LPS and the highest levels in material extracted by the PCP and Triton-Mg2+ techniques. No protein contamination could be detected after proteinase K treatment. After silver staining LPS PAGE profiles showed ladder patterns characteristic of smooth LPS for B. uulgatus, B. thetaiotaomicron and the control Escherichia coli 018 : K-strains, whereas the other Bacteroides strains showed mainly rough and low M, material only. The PCP method did not select for high M, material in the B. fragilis strains; otherwise the LPS profiles for all extraction methods were identical. The biological activities of native and sodium salt form LPS were investigated on a weight for weight basis and compared to that of E. coli 0 1 8 : K-PW-LPS. Amongst the LPS from Bacteroides strains, those prepared by the PW method were found to have a significantly higher activity in a galactosamine mouse lethality model, in induction of TNF and the Limulus amoebocyte lysate (LAL) assay, than LPS extracted by the PCP or Triton-Mg2+ methods. LPS from Bacteroides strains extracted by the PCP method had consistently low activity in all assays. Comparing PW-LPS from Bacteroides strains with that from E. coli 018:K-in the galactosamine mouse model, the E. coli 018 : K-LPS was c. 5000-fold more active than the most active bacteroides LPS. However, in the LAL assay native PW-LPS from both the B. fragilis strains, and B. caccae had higher activities (up to 30-fold) than E. coli 0 18 : K-LPS, with the PW-LPS from the other Bacteroides spp. being up to 15-fold less active than the E. coli 0 1 8 : K-PW-LPS. In the TNF induction assay, E. coli 0 18 : K-PW-LPS was 4-50-fold more active than bacteroides PW-LPS. In the LAL assay and galactosamine mouse model, native LPS had more activity (c. twofold) than sodium salt form LPS. There was no clear difference in activity between native and sodium salt form LPS in the TNF induction assay. The results for the LAL and TNF induction assay were re-evaluated relative to KDO concentration. In the TNF induction assay, previously low activities seen on a weight for weight basis were due in part to less KDO being present. However, LAL activity for PCP-LPS was still low after re-evaluation relative to KDO concentration. The molecular basis for the differences in biological activity of bacteroides LPS in relation to extraction methods and chemical composition is not yet understood.
Chemiluminescence Induced by Phagocytosis of Escherichia coli by Polymorphonuclear Leucocytes
Microbiology, 1984
Chemiluminescence emitted by phagocytosing human polymorphonuclear leucocytes stimulated by Escherichia coli was measured using a liquid scintillation counter equipped with a multichannel analyser. In the presence of the amplifying agent luminol, light emission can be divided into two channels, one of which ('high energy') appears to correlate directly with phagocytic activity of the PMNL, and the other ('low energy') with the background luminol dioxygenation by the cells. Measuring in the 'high energy' window also eliminates the normal 'out of coincidence' background. The method is applicable to measuring opsonizing capacity of different sera, and responds to PMNL number, age, composition of assay medium and the integrity of the stimulating bacteria. Other bacterial strains produce a similar response, as does the artificial stimulator zymosan. Low temperature and anaerobiosis, which inhibit phagocytic killing, also suppress light emission.
Variable Bacterial Responses to Oxidative Stress in Different Bacterial Species
Al-Azhar Medical Journal
Background: Living organisms are exposed to oxidative stress due to internal or external stimuli. It results from the imbalance between the production and elimination of reactive oxygen species. This leads to loss of homeostasis. Objective: To test the effect of oxidative stress on the level of the production of reduced glutathione (GSH) as an antioxidant, malondialdehyde (MDA) as a measure of lipid peroxidation, and of the siderophore enterobactin as an oxidative stress response, in different bacterial species. Materials and Methods: H2O2 minimum inhibitory concentration (MIC) was determined in Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603, using broth-macrodilution method. The levels of GSH and MDA were measured in E. coli ATCC 25922 and K. pneumoniae ATCC 700603 and in clinical isolates of E. coli, K. pneumoniae and Staphylococcus aureus after exposure to lethal H2O2 concentration, using Glutathione Reduced Kit and Lipid Peroxide-Malondialdehyde Kit, respectively. The level of expression of entC gene, involved in enterobactin biosynthesis, in presence of 0.25 and 0.5 MIC of H2O2 was determined using quantitative reverse transcription-polymerase chain reaction. Results: H2O2 MIC for both E. coli ATCC 25922 and K. pneumoniae ATCC 700603 was 1.5 mM. Exposure of E. coli to H2O2 resulted in a significant increase in GSH (p=0.0001) and MDA (p=0.0001) levels. However, in K. pneumoniae, a significant decrease in the GSH (p=0.0001) and MDA levels (p=0.0001) was recorded upon H2O2 exposure. No change in MDA and GSH levels was detected in S. aureus isolates exposed to H2O2. The expression of entC gene in both E. coli ATCC 25922 and K. pneumoniae ATCC 700603 was reduced in presence of 0.25 and 0.5 H2O2 MIC. Conclusion: Bacteria responded differently to oxidative stress, with S. aureus bacteria as the least affected by oxidative stress. Enterobactin role in oxidative stress needs reevaluation.