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PubMed1989

Sources of low-molecular-weight host factors that phenotypically increase the resistance of Haemophilus influenzae type b to bacteriolysis: non-identity with a factor active in gonococci.

Both gonococci and Haemophilus influenzae type b (Hib) in response to incubation with low-molecular-weight components of blood are converted to a relative resistance to killing by antibody and complement in vitro. Recently, cytidine 5'-mono-phospho-N-acetylneuraminic acid (a sialyl donor present in mammalian tissues) was found to convert gonococci. Here we report that this compound was inactive in Hib. In further contrast, the Hib-converting activity of serum was not retained by 500-M, filters, not sensitive to pH 2, and not active in the presence of growth media. Thus the phenotypic resistance in Hib and gonococci appear to have a different metabolic basis. The low-Mr serum factors active in Hib remain to be identified. Filtrates of human nasopharyngeal washes were also active, further suggesting that the converted form resembles the phenotype of Hib in vivo.

Blood Bactericidal Activity↗
PubMed2000

Susceptibility of Vibrio cholerae O139 to antibody-dependent, complement-mediated bacteriolysis.

Volunteer studies with Vibrio cholerae O1 have shown that the best correlate of a vaccine's protective efficacy is its propensity to elicit serum bactericidal responses in its recipients. Attempts to detect such responses following infection with V. cholerae O139, however, have met with varying success. Using a tube-based assay which involves viable counting, we now report that strains of serogroup O139 can appear to be sensitive or resistant to a fixed concentration of complement in the presence of antibody, depending on assay conditions. Susceptibility to lysis is critically dependent on the availability of complement, but with O139 indicator strains this is not simply determined by the concentration of serum added to the reaction mix. The nature of the assay diluent and the concentration of indicator bacteria can also dramatically affect bactericidal end points, whereas such variables have minimal significance with O1 indicator bacteria. Although some laboratories use unencapsulated mutant strains to seek evidence of seroconversion following exposure to V. cholerae O139, this is not necessary, and our findings question the significance of capsule expression as a determinant of complement sensitivity when antibody is present. The medium used for growth of the indicator strain and the particular strain used appeared to be unimportant. Each of seven O139 isolates tested was found to be lysed by antibody and complement in our standard assay system, which allowed the detection of significant serum bactericidal responses in 9 of 11 cases of O139 disease.

Antibodies, Bacterial↗
PubMedDate not supplied

Relationship between the bactericidal and bacteriolytic activity of cephalosporins and changes in the cell volumes of Escherichia coli cultures.

The bactericidal effect of cefoxitin and cefotaxime in relation to concentration and exposure time, as demonstrated by the killing curve diagrams of Escherichia coli cultures, was compared with the degree of bacteriolysis and the cell volume increase measured by the coulter counter-channel analyser system. Human plasma ultrafiltrate was used as the growth medium. Cefoxitin has a higher bactericidal activity than cefotaxime. With increasing concentrations the bactericidal efficacy of cefoxitin increases more rapidly in the lower range of concentrations (2-10 mg/l) than in the higher range (10-40 mg/l). In contrast, the bactericidal effect of cefotaxime in the range 0.06-1.2 mg/l is virtually constant and can only be increased by high levels (10-40 mg/l). The morphometric effect of cefoxitin on E. coli cultures, as demonstrated by volume distribution curves, is characterized by intensive and rapidly appearing bacteriolysis 20 min after exposure to the antibiotic without a preceding increase in bacterial cell volume. Higher concentrations result in an earlier onset of bacteriolysis. In contrast, the application of cefotaxime reveals a massive increase in bacterial cell volume (more than five-fold) with a delayed (greater than 2 h) onset of bacteriolysis. High cefotaxime concentrations reduce the extent of bacterial cell volume increase, associated with an earlier and more intensive onset of bacteriolysis. With both cephalosporins, the bacterial cell alterations are particularly dependent on the exposure time. There is evidently a close correlation between bactericidal and bacteriolytic activity. This is valid both for the two cephalosporins and generally for the concentration-activity relationships.

Blood↗
PubMed2001

Functional activity of anti-Neisserial surface protein A monoclonal antibodies against strains of Neisseria meningitidis serogroup B.

Neisserial surface protein A (NspA) is currently being investigated with humans as a candidate vaccine for the prevention of meningococcal disease. Although NspA is highly conserved, the ability of anti-NspA antibodies to bind to or elicit complement-mediated bactericidal activity against diverse Neisseria meningitidis serogroup B strains is controversial. To evaluate strain differences in NspA surface accessibility and susceptibility to bactericidal activity, we prepared murine immunoglobulin G2a anti-NspA monoclonal antibodies (MAbs) and evaluated their functional activity against 10 genetically diverse N. meningitidis serogroup B strains. By colony Western blot, all 10 strains expressed NspA as detected by one or more MAbs. By flow cytometry, two MAbs were found to bind to the bacterial surface of 6 of the 10 strains. In addition, two strains showed variable NspA surface accessibility for the MAbs despite being uniformly positive for NspA expression by colony Western blotting. Only 4 of the 10 strains were susceptible to anti-NspA complement-mediated bacteriolysis. Passively administered MAb protected infant rats from developing bacteremia after challenge with N. meningitidis serogroup B strain 8047 (surface binding positive, susceptible to anti-NspA bacteriolysis), was poorly protective against strain BZ232 (surface binding variable, resistant to bacteriolysis), and did not protect against strain M986 (surface binding negative, resistant to bacteriolysis). Finally, NspA does not appear to be critical for causing bacteremia, as an NspA knockout from strain 8047 was highly virulent in infant rats. Taken together, these findings suggest that an NspA-based vaccine will need to incorporate additional antigens to elicit broad protection against N. meningitidis serogroup B.

Animals↗
PubMed1992

The modulation of the bacteriolytic effect of beta-lactam antibiotics by non-antibiotics.

The addition of cationic proteins such as lysozyme, ribonuclease and cytochrome C enhanced the beta-lactam-induced bacteriolysis of staphylococci measured as release of wall label or by optical density. The treatment of staphylococci with penicillin plus cytochrome C resulted in a reduced viability of bacteria compared with those treated with penicillin alone. The wall autolysis and the penicillin-induced bacteriolysis of staphylococci were enhanced by the lysosomal enzyme cathepsin C. The penicillin-induced bacteriolysis was also enhanced by the D-amino acids D-alanine and D-methionine, while the comparable L-amino acids did not reveal any activity. On the other hand, some polyanionic substances were able to suppress the penicillin-induced bacteriolysis. Radiochemical and electron microscopic studies revealed the participation of bacterial wall autolysins in the first steps of degradation processes of staphylococcal walls within murine bone marrow-derived macrophages.

Amines↗
PubMed1976

The interaction of leukocytes and their hydrolases with bacteria in vitro and in vivo: the modification of the bactericidal and bacteriolytic reactions by cationic and anionic macromolecular substances and by anti-inflammatory agents.

Acid hydrolases from extracts of human blood leucocytes lyse Staph.aureus, Staph.albus and Strep.faecalis in vitro. The leucocyte enzymes can be substituted by a lytic mixture which contains crude trypsin, lysolecithin, phospholipase C and lysozyme, which lyse other bacterial species, e.g. E.coli and Listeria which are resistant to leucocyte enzymes. Bacteriolysis by the lytic agents is strongly inhibited by the anionic polyelectrolytes, heparin, chondroitin sulphate, DNA, dextran sulphate and other sulphated mucopolysaccharides, by the cationic materials, histone, protamine sulphate, leucocyte cationic proteins and polylysine. Other strong inhibitors are trypsan blue and congo red, the phospholipids phosphatidyl serine and ethanolamine, gold thiomalate, extracts of coffee and tea and the anti-inflammatory agents, ultracorten-H, and ultracortenol. Bacteriolysis is also strongly inhibited by normal human serum and by synovial fluids from patients with a variety of joint diseases. The inhibitors in these body fluids are associated with the globulin fractions. Since mixtures of anionic and cationic polyelectrolytes, at equimolar concentrations, failed to inhibit bacteriolysis by leucocyte enzymes, it is postulated that a delicate balance between positively and negatively charged inhibitors control the degradation of cell wall components of bacteria in inflamed areas. Such bacterial components, induce 'storage type' granulomas. The possible role played by polyelectrolytes in the control of the inflammatory process induced by leucocyte hydrolases will be discussed.

Animals↗
PubMed2003

[Inhibitory effect of egg white lysozyme on ceftazidime-induced release of endotoxin from Pseudomonas aeruginosa].

AIM: To investigate the inhibitory effect of egg white lysozyme (LZM) on ceftazidime (CFT)-induced release of endotoxin from Pseudomonas aeruginosa. METHODS: P. aeruginosa PAO1 was inoculated in nutrition broth or diluted rabbit blood free of antibiotics in the presence or absence of LZM and incubated at 37 degrees C on a water bath shaker. beta-Lactam antibiotic, CFT, was added to cultures at 3.5 h (nutrition broth culture) or 5 h (diluted rabbit blood culture) after inoculation. After 3 h of CFT treatment, the supernatants from different bacterial cultures were prepared by centrifuge and the concentrations of endotoxin in the supernatants were measured. The bacterial supernatants were also added to a murine macrophage cell line RAW 264.7 or intravenously injected into carrageenin-sensitized mice. Tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) concentrations in RAW 264.7 supernatants or in mouse sera were tested. RESULTS: CFT treatment alone obviously inhibited the growth of P. aeruginosa PAO1 accompanied by strong and rapid bacteriolysis and released relatively high concentration of endotoxin from bacteria both in nutrition broth and in diluted rabbit blood cultures. The bacterial supernatant from CFT treatment alone yielded high concentrations of TNF alpha both in RAW 264.7 cells and in mice and high level of NO in RAW 264.7 cells. Treatment with the combination of LZM and CFT evidently blocked the lysis of bacteria and reduced the release of endotoxin without decreasing bactericidal activity of CFT. TNF alpha and NO productivity of the supernatants prepared from the LZM/CFT combinative treated bacterial cultures were significantly decreased both in RAW 264.7 cells and in mice indicating that the inflammatory activity was reduced. CONCLUSION: LZM can effectively prevent CFT-induced bacteriolysis, endotoxin release and subsequent proinflammatory factor production but without decreasing bactericidal activity of CFT, resulting in the disassociation of bactericidal activity and bacteriolysis. Thus, LZM might be important for preventing endotoxemia in Gram-negative sepsis with the treatment of antibiotics.

Animals↗
PubMed1993

Aeromonas salmonicida grown in vivo.

The virulent fish pathogen Aeromonas salmonicida was rapidly killed in vivo when restricted inside a diffusion chamber implanted intraperitoneally in rainbow trout. After a period of regrowth, the survivors had acquired resistance to host-mediated bacteriolysis, phagocytosis, and oxidative killing, properties which were subsequently lost by growth in vitro. Resistance to bacteriolysis and phagocytosis was associated with a newly acquired capsular layer revealed by acidic polysaccharide staining and electron microscopy. This capsular layer shielded the underlying, regular surface array (S-layer) from immunogold labeling with a primary antibody to the S-layer protein. Resistance to oxidative killing was mediated by a mechanism not associated with the presence of the capsular layer. An attenuated vaccine strain of A. salmonicida grown in vivo failed to express the capsular layer. Consequently, the in vivo-grown cells of this attenuated strain remained as sensitive to bacteriolysis, and as avidly adherent to macrophages, as the in vitro-grown cells. The importance of these new virulence determinants and their relation to the known virulence factors of A. salmonicida are discussed.

Aeromonas↗