Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The results of the study of the effect of various concentrations of egg lysozyme on M. luteus and M. varians using 2 methods, i.e. serial dilutions in agar and turbidimetric are presented. It was found that the MIC of lysozyme for M. luteus ranged within wide limits, from less than 0.0003 to 1 mg/ml. M. varians was stable to lysozyme. The MIC for all the strains was 8 mg/ml. The turbidimetric method provided determination of general regularities in changes of the optical density in all the strains of M. luteus under the effect of various concentrations of lysozyme. On the basis of these data it was possible to consider the method as the most deep means for determining the intraspecies similarities in the surface structures of Micrococcus as compared to the method of serial dilutions in agar. The dynamics of the changes in the optical density of the M. luteus suspension markedly differed from that of M. varians.
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PMID:[Action of egg lysozyme on representatives of the family Micrococcaceae. Its action on Micrococcus]. 56 55

Two methods for determination of staphylococcal and micrococcal sensitivity to lysozyme, i.e. the method of serial dilutions in agar and the drop method developed by the authors were compared. The drop method is a modification of the procedure described by Kloos et al. Close correlation between these two methods (r = 0.97 +/- 0.018) was found. The regression curve providing determination of the lysozyme MIC with the drop method was plotted. The drop method is more simple and economical as compared to the method of serial dilutions in agar. It has an advantage in testing sensitivity of single strains.
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PMID:[Drop method of determining micrococcal and staphylococcal sensitivity to egg lysozyme]. 70 97

The interaction of bacteria with platelets at the cardiac valve surface represents a critical event in the induction of infective endocarditis. Platelets are thought to modulate induction or propagation of endocarditis via secretion of alpha-granule-derived platelet microbicidal protein (PMP) (a low-molecular-mass, cationic, heat-stable protein distinct from lysozyme). We studied representative PMP-susceptible and PMP-resistant Staphylococcus aureus isolates to determine their in vitro bacteriostatic and bactericidal susceptibilities to combinations of PMP plus antistaphylococcal antibiotics. PMP plus oxacillin exerted a synergistic bactericidal effect, in contrast to either agent alone, regardless of the intrinsic PMP susceptibility of the isolate tested. Exposure of S. aureus to PMP alone resulted in residual postexposure growth-inhibitory effects lasting from 0.9 to 1.8 h. Sequential exposure of S. aureus isolates to PMP for 30 min followed by exposure to either oxacillin or vancomycin (each at 10x the MIC for 120 min) resulted in a significant extension of the postantibiotic-effect duration compared with antibiotic exposure alone (P less than or equal to 0.05). Collectively, these findings indicate that PMP both enhances antibiotic-induced killing of S. aureus and increases the postantibiotic-effect duration in S. aureus.
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PMID:Platelet microbicidal protein enhances antibiotic-induced killing of and postantibiotic effect in Staphylococcus aureus. 141 49

The mechanism of uptake of aminoglycosides across the outer membrane of Escherichia coli was reevaluated. Porin-deficient mutants showed no alteration in gentamicin or kanamycin susceptibility. Furthermore, the influence of kanamycin on intrinsic tryptophan fluorescence of porin OmpF (Y. Kobayashi, and T. Nakae, Eur. J. Biochem. 151:231-236, 1985) was shown to be strongly influenced by protein concentration and EDTA. This led to the hypothesis that aminoglycoside-mediated increases and decreases in intrinsic tryptophan fluorescence were due to aggregation-disaggregation of OmpF mediated by interaction at a divalent cation binding site on OmpF. Gentamicin, kanamycin, and polymyxin B increased E. coli outer membrane permeability to the hydrophobic fluorescent compound 1-N-phenyl-naphthylamine (NPN) and the peptidoglycan-degrading enzyme lysozyme. Addition of Mg2+ blocked these permeabilizing activities. Furthermore, gentamicin and polymyxin B bound to Mg(2+)-binding sites on E. coli lipopolysaccharide, as determined in dansyl polymyxin displacement experiments. A polymyxin-resistant, lipopolysaccharide-altered pmr mutant of E. coli had a fourfold-lower MIC of gentamicin and kanamycin and was more poorly permeabilized to 1-N-phenylnaphthylamine than was its parent strain. These data were consistent with uptake of aminoglycosides across the E. coli outer membrane by the self-promoted uptake mechanism.
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PMID:Interaction of aminoglycosides with the outer membranes and purified lipopolysaccharide and OmpF porin of Escherichia coli. 165 59

The formation of acceptor for the N epsilon-(D-Ala)-acceptor transpeptidase is an essential feature of nascent peptidoglycan processing. In Gaffkya homari the synthesis of cross-bridges in peptidoglycan includes a variety of penicillin-sensitive enzymes, e.g., transpeptidase, DD-carboxypeptidase, and LD-carboxypeptidase. To determine the primary target, we grew cultures in the presence of the MICs of benzylpenicillin (0.2 microgram/ml), methicillin (10 micrograms/ml), cephalothin (5 micrograms/ml), and cefoxitin (25 micrograms/ml) and examined the monomer-dimer composition of each peptidoglycan by high-performance liquid chromatography after muramidase digestion. From these studies it was recognized that of all the dimers, the synthesis of the predominant cross-bridge, diamidated octapeptide (-Ala-iso-D-Gln-Lys-D-Ala -Ala-iso-D-Gln-Lys-D-Ala), is most sensitive to the action of the beta-lactam at its MIC. The enhanced deamidation of the acceptor tetrapeptide, one of the substrates for the transpeptidase, is correlated with the inhibition of this cross-bridge. For example, at the MIC of benzylpenicillin, the ratio of amidated tetrapeptide to nonamidated tetrapeptide decreased from 2.8 in the control to 1.0 in the treated culture. From these results it would appear that a decrease in preferred acceptor for the transpeptidase results in the inhibition of synthesis of this major cross-bridge. Thus, the metabolism of the amide function of the monomer peptides may represent an additional feature of processing in the assembly of cross-bridged dimers in the peptidoglycan of this organism that is sensitive to the action of beta-lactam.
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PMID:Biosynthesis of peptidoglycan in Gaffkya homari: on the target(s) of benzylpenicillin. 195 43

Previous work has shown that the side wall of a Gram-positive rod is initially laid down as a compact layer inside the older wall. It is then stretched as it comes to bear tension due to the osmotic pressure inside the cell. If the polar wall is likewise capable of a degree of expansion, then no new murein need be added while the planar cross-wall splits and converts into two poles. In Bacillus subtilis mutant strain FJ6, which is deficient in autolytic enzymes, pole formation can be caused by addition of exogenous muramidase (10 micrograms hen egg white lysozyme ml-1 for 10 min at 35 degrees C). This strain grows as long filaments with many completed cross-walls, but enzymic treatment caused the formation of many new poles of normal morphology as judged by thin section electron microscopy. Fully separated poles of normal appearance were also found when more than 100 times the MIC (1 microgram ml-1) of vancomycin was added to block wall growth totally and rapidly 10 min before the addition of lysozyme. We conclude, therefore, that no new murein is needed in the conversion of the flat septum into poles and that the unstressed cross-wall is capable of the necessary expansion.
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PMID:Normal pole formation during total inhibition of wall synthesis of Bacillus subtilis. 311 56

The effect of ceftazidime on the phagocytic and bactericidal activity of human macrophages was investigated. At concentrations of half the MIC the antibiotic caused macrophages to ingest and kill Staphylococcus aureus and Pseudomonas aeruginosa at a higher level than did macrophages without drug. Bacteria pretreated with ceftazidime became more sensitive to the bactericidal activity of macrophage lysozyme. Macrophages taken from mice receiving intravenous ceftazidime showed greater phagocytic activity than those from control mice.
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PMID:Synergy of ceftazidime and human macrophages on phagocytosis and killing of Staphylococcus aureus and Pseudomonas aeruginosa. 311 62

The effects of sub-minimum inhibitory concentrations (sub-MICs) of monobactams (aztreonam and AMA1080) on the host-parasite relationship were studied in an in vitro system using an established mouse macrophage cell line. The presence of sub-MICs aztreonam or AMA1080 enhanced significantly the macrophage bactericidal activity against Escherichia coli S615, Pseudomonas aeruginosa K1, Klebsiella pneumoniae 12 and Serratia marcescens US5. Even four times the MIC of monobactams had no direct effect on macrophages. A synergistic bactericidal effect against E. coli was also observed with sub-MICs of monobactams and lysozyme or macrophage lysate. Furthermore, E. coli treated with sub-MICs of aztreonam was more sensitive to two bactericidal macrophage products, hydrogen peroxide and superoxide anion. These results suggest that the effects of monobactams are exerted on bacteria and not on macrophages; sub-inhibitory levels of monobactams may alter the bacterial cell rendering it more susceptible to bactericidal substances released by macrophages, thus favouring phagocytosis and killing by macrophages. Electron microscopic observations support these conclusions. This study provides evidence that monobactams at sub-MICs may work in partnership with host defenses against Gram-negative bacterial infections.
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PMID:Enhanced bactericidal action of mouse macrophages by subinhibitory concentrations of monobactams. 375 35

Electronmicroscopy of thin sections of log phase cells of Enterobacter cloacae NCTC 10005 grown for 4 h in the presence of sulphadiazine 250 micrograms/ml, trimethoprim 12.5 microliters/ml or the combination of sulphadiazine 250 micrograms/ml plus trimethoprim 12.5 micrograms/ml indicated that both agents caused marked morphological damage even though the MIC of sulphadiazine for the E. cloacae strain was > 3000 micrograms/ml. The damage took the form of electron-transparent areas devoid of ribosomes in the cytoplasm and detachment of the outer membrane. The latter was most marked with trimethoprim, which also caused damage to the cytoplasmic membrane. It is postulated that the synthesis of the peptidoglycan layer was affected by the antimetabolites since the morphological effects were strikingly similar to those caused by treatment of E. cloacae with disodium edetate plus lysozyme. Viable counts of cultures undergoing the same treatments as those prepared for electronmicroscopy indicated that although sulphadiazine merely partially inhibited growth it nevertheless enhanced the bactericidal action of trimethoprim over a 5-h period.
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PMID:An electronmicroscope study of the effect of sulphadiazine and trimethoprim on Enterobacter cloacae. 841 97

This study investigated the antibacterial activity of human pleural fluid (HPF) and its interaction with gentamicin (GM), meropenem (MRPM), ciprofloxacin (CPFX) and clarithromycin (CLTM) against Escherichia coli K-12, Proteus rettgeri (Sanelli) and Staphylococcus aureus. Minimal inhibitory concentrations or volumes, expressed as MIC or volume percentage (MIV, V/V%), were measured using a micro-dilution technique in microtiter plates. The antimicrobial activity of HPF combinations with antimicrobial drugs was evaluated by the chequerboard method calculating the fractional inhibitory concentration index (FIC) values. HPF MIVs (%) were: 37.54; 19.85; 1.74 for E. coli, P. rettgeri and S. aureus, respectively. FIC values indicated a synergistic effect with GM, MRPM and CPFX against E. coli and P. rettgeri and an additive effect for the combination HPF plus CLTM or indifference with HPF plus GM and CPFX against S. aureus. The presence of antibodies, complement factors, lysozyme, alpha-defensins and enzymes could explain the antimicrobial activity of HPF and its synergistic effect with certain antibiotics.
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PMID:Antibacterial activity of human pleural fluid: alone and in combination with antibiotics. 991 8


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