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PubMed1977

Properties of strains of Staphylococcus aureus in the 94, 96 complex.

Strains of Staphylococcus aureus that are lysed by typing phages 94 or 96, or by both phages, are usually resistant to lysis by other basic-set typing phages. They are, however, sensitive to several experimental phages and show a number of different lytic patterns when tested against these phages. These differences in susceptibility are due, in part, to immunity imposed by temperate phages carried by the different strains. Resistance to lysis by other basic-set phages was not due to prophage immunity, but to at least one restriction and modification system in such strains. Restrictionless mutants were isolated from one strain in several experiments. These showed an increased sensitivity to many basic-set phages. However, all of these mutants retained the ability to modify the phages to the characteristic "94, 96" specificity. Strains in the 94, 96 complex showed a remarkable homogeneity in biological traits. The majority were non-pigmented, and produced lipase, fibrinolysin, alpha and delta haemolysins and enterotoxin B. This homogeneity may well be a reflexion of the restriction and modification systems in these strains, that prevent the acquisition of genetic material from strains outside the complex. A new lytic group V is proposed for members of the 94, 96 complex.

Anti-Bacterial Agents↗
PubMed1977

Immunogenicity and characteristics of M protein released by phage-associated lysin from group-A streptococci types 1 and 23.

A phage-associated lysin (PAL) was used to release M protein from goup-A streptococci of types 1 and 23. Much of the lysin-released-M protein (LYSIN-M) of both types was of high molecular weight, since LYSIN-M appeared just after the void volume on Sephadex G-200 gel-filtration. Some of the LYSIN-M appeared just after the void volume on Sephadex G-200 gel-filtration. Some of the LYSIN-M of both types was found to be firmly attached to group-A carbohydrate. Type-1 LYSIN-M was partially purified by ammonium-sulfate precipitation followed by absorption and elution from an immunoabsorbent column containing antibody for group-A carbohydrate. Type-23 LYSIN-M was partially purified by precipitation at its isoelectric point, pH 4-9. Rabbits immunised in the footpads with either type-1 or type-23 LYSIN-M responded by producing both precipitins and bactericidal (opsonising) antobodies. Some of the antiesera were absorbed and rendered specific for homologous acid extracts. The LYSIN-M preparations of both types 1 and 23 were originally contaminated with heat-labile antigen(s). Antibodies to these heat-labile antigen(s), which cross-react from type to type, were found in the type-specific antisera distributed by the Center for Disease Control. The specificity of Lancefield typing antisera depends on their being tested with extracts of streptococci prepared at pH 2 and 100 degree C for 10 min. Although LYSIN-M is more difficult to prepare and purify then acid-heat released M protein, it might prove useful for studying the nature of native streptococcal M protein.

Antigens, Bacterial↗
PubMed1977

The activity of polymyxins against Escherichia coli in an in-vitro model of the urinary bladder.

The activities against a strain of Escherichia coli of polymyxin B, colistin (polymyxin E) and their sulphomethyl derivatives sulphomyxin and colistin sulphomethate have been examined in an in-vitro model of the urinary bladder under conditions similar to those that may operate in the therapeutic situation. In the dynamic conditions of the model, polymyxins exhibited a reduced activity against E. coli in comparison with activity against exponentially growing cultures in a static system. Nevertheless, long-term suppression of bacterial growth was achieved with levels of polymyxin B and colistin that can be attained during therapy, whereas sulphomethylpolymyxins had little effect on bacterial growth even on prolonged exposure.

Bacteriolysis↗
PubMed1985

The contribution of a capsule to survival of staphylococci within bovine neutrophils.

The encapsulated strain M of Staphylococcus aureus and the encapsulated strain 76 of S. simulans survived incubation with bovine neutrophils in media containing heated bovine serum 0.5% v/v or milk whey 10% v/v. With two unencapsulated strains of S. aureus, M12 and M60, less than 5% of the original inoculum survived. When the concentrations of bovine serum and milk whey were increased to 2% and 50% respectively, survival of the encapsulated strains was similar to that of the unencapsulated strains. The ability of skimmed milk 50% v/v to opsonise strain M was found in milk from 95% of 62 cows. The individual values for percentage intracellular survival of strains of S. aureus phagocytosed by bovine neutrophils in the presence of bovine serum 2% v/v or milk whey 50% v/v were 0.48, 0.30 and 0.24 for strains M60, M and M12 respectively. Intracellular survival of strain M60 was significantly greater than that of strains M12 and M. The encapsulated coagulase-negative strain 76 (S. simulans) was not susceptible to lysis by lysostaphin, and it was not possible to destroy extracellular staphylococci to measure intracellular survival. It is concluded that the capsule of S. aureus strain M does not contribute to intracellular survival.

Animals↗
PubMed1986

Bactericidal, bacteriolytic and opsonic activity of human serum against Escherichia coli.

The effect of human serum on Escherichia coli was studied with serum-sensitive and serum-resistant strains. The bactericidal effect of human serum on serum-sensitive strains of E. coli depended on the activation of the classical complement pathway. The role of activation of the alternative pathway was less important. After incubation in sub-bactericidal concentrations of serum these strains were also easily phagocytosed by polymorphonuclear leukocytes (PMNL). Strains of E. coli of certain O-types required not only an intact classical pathway but also the presence of specific antibodies for effective killing by serum and effective phagocytosis by PMNL, despite rapid activation of complement and rapid deposition of C3 on the bacterial surface in the absence of antibody. Capsulate strains O1K1 and O78K80 resisted the bactericidal effect of serum even in the presence of specific antibodies; phagocytosis by PMNL only occurred after opsonisation with specific antibodies.

Antibodies, Bacterial↗
PubMed1987

Effects of mucopolysaccharides on penicillin-induced lysis of Staphylococcus aureus.

Effects of four mucopolysaccharides and dextran sulphate on penicillin-induced lysis of Staphylococcus aureus FDA 209P were studied. Heparin and dextran sulphate inhibited lysis, whereas hyaluronic acid enhanced it. Chondroitin sulphates A and C had no effect. Incubation of S. aureus suspended in 0.03 M phosphate buffer (pH 7.0) with dextran sulphate inhibited autolysis of the bacteria, whereas incubation with hyaluronic acid enhanced autolysis. Both extracellular and cell-associated autolysin activities of S. aureus were suppressed by dextran sulphate and high concentrations of heparin. The addition of hyaluronic acid enhanced autolysin activity. The release of lipoteichoic acid (LTA), a modulator of autolysin activity, from penicillin-treated bacteria was inhibited by heparin and dextran sulphate. However, hyaluronic acid had no effect on release of LTA. These results suggest that inhibition of penicillin-induced lysis of S. aureus by heparin results mainly from inhibition of LTA release while dextran sulphate inhibits both autolysin activity and LTA release. Hyaluronic acid appears to enhance penicillin-induced lysis through activation of the autolysins.

Bacteriolysis↗
PubMed1993

Detection of penicillin tolerance in Streptococcus pyogenes.

Three traditional assays were used to determine the minimal bactericidal concentration (MBC) and minimal inhibitory concentration (MIC) for Streptococcus pyogenes (group A streptococci) in two phases of growth and the time taken to kill the organisms. Three other methods were used for the determination of penicillin tolerance: a cell-lysis assay, the beta-lactamase disk method and the replication method. Twenty strains, comprising penicillin-tolerant clinical isolates and two laboratory mutants, were used to evaluate the six tests. Results indicated that two groups of S. pyogenes can be distinguished--four highly tolerant and three moderately tolerant strains. The moderately tolerant strains were not recognised when rapidly growing instead of stationary cultures were used for the MBC and MIC determinations. The MBC/MIC ratio for tolerant strains was > 100. Tolerance percentage ranged from 0.30 to 1.07 and 0.29 to 3.96 for cultures in the mid-logarithmic and stationary phases of growth, respectively. The cell-lysis assay, the beta-lactamase disk method and the replication method may be used to screen for tolerance. Detection of high or moderate tolerance by determining the MBC/MIC ratio for mid-logarithmic or stationary cultures is recommended.

Analysis of Variance↗
PubMed1999

Elucidation of the antistaphylococcal action of lactoferrin and lysozyme.

The cationic tear proteins lactoferrin and lysozyme exhibit co-operative antistaphylococcal properties. The purpose of this study was to determine the mechanism of action of this co-operation on Staphylococcus epidermidis. Following blocking of lipoteichoic acid (LTA) binding sites, the effects on binding of lactoferrin and susceptibility to lactoferrin and lysozyme were determined. The effect of lactoferrin on autolysis and LTA release was also examined. Maximal susceptibility occurred on addition of lactoferrin first followed by lysozyme. Blocking the LTA binding sites both reduced lactoferrin binding and decreased susceptibility. Autolytic activity decreased and LTA release increased in the presence of lactoferrin. These results suggest that binding of lactoferrin to LTA is important in its synergy with lysozyme and interferes with the autolysins present on the LTA. It is proposed that, on binding to the anionic LTA of S. epidermidis, the cationic protein lactoferrin decreases the negative charge, allowing greater accessibility of lysozyme to the underlying peptidoglycan.

Anti-Bacterial Agents↗
PubMed1975

Lysis enhancement: a novel form of interaction between beta-lactam antibiotics.

A novel form of synergy has been observed to occur between cephalexin and certain other beta-lactam antibiotics. In the presence of cephalexin a reduction was found in the concentration of other beta-lactam agents needed to induce lysis of Escherichia coli; the effect was particularly marded when cephalexin was allowed to act for a short time before the addition of the second agent. The basis of this type of synergy--which is not likely to be of therapeutic value--is discussed in terms of a theroy perviously put forward, whcih suggests that penicillins and cephalosporins have two distinct sites of action in Gram-negative bacilli.

Ampicillin↗
PubMed1975

The nature and incidence of lysogeny in Mycobacterium fortuitum.

Ten of 28 strain of Mycobacterium fortuitum (ranae) were found to be associated with bacteriophage; three were pseudolysogenic, one liberated a phage that lysed a sensitive indicator strain, two liberated morphologically complete phages that did not lyse any of the strains used in this study and four liberated morphologically defective phages. The lysogenic and defectively lysogenic strains showed anomalies in cultural, biochemical and antigenic properties and in susceptibility to superinfecting phages. In view of the high frequency of lysogeny found in M. fortuitum, the role of bacteriophage in the variation of properties, including pathogenicity, of mycobacteria of greater clinical importance merits further consideration.

Bacteriolysis↗