Influence of cultivation conditions on the production of extracellular proteins by Staphylococcus aureus

Effect of mild acid on gene expression in Staphylococcus aureus

During staphylococcal growth in glucose-supplemented medium, the pH of a culture starting near neutrality typically decreases by about 2 units due to the fermentation of glucose. Many species can comfortably tolerate the resulting mildly acidic conditions (pH, approximately 5.5) by mounting a cellular response, which serves to defend the intracellular pH and, in principle, to modify gene expression for optimal performance in a mildly acidic infection site. In this report, we show that changes in staphylococcal gene expression formerly thought to represent a glucose effect are largely the result of declining pH. We examine the cellular response to mild acid by microarray analysis and define the affected gene set as the mild acid stimulon. Many of the genes encoding extracellular virulence factors are affected, as are genes involved in regulation of virulence factor gene expression, transport of sugars and peptides, intermediary metabolism, and pH homeostasis. Key results are verified by gene fusion and Northern blot hybridization analyses. The results point to, but do not define, possible regulatory pathways by which the organism senses and responds to a pH stimulus.

Quantitative spectrophotometric assay for staphylococcal lipase

We report the development of a specific spectrophotometric assay for the quantitative determination of lipase activity in Staphylococcus aureus. The assay is based on the rate of clearance of a tributyrin emulsion, and it can detect as little as 1.0 micrograms of purified Pseudomonas lipase per ml. By comparison with the reaction rates obtained with Pseudomonas lipase, we calculated that S. aureus PS54C and S6C produce approximately 15 and 60 micrograms of extracellular lipase per ml, respectively. Neither PS54, which is lysogenized with the converting bacteriophage L54a and is consequently lipase negative (Lip-), nor KS1905, a Lip- transpositional mutant of strain S6C, was positive in our spectrophotometric assay. The specificity of the spectrophotometric tributyrin assay was confirmed with a triolein plate assay; supernatants from S6C and PS54C hydrolyzed triolein, while supernatants from PS54 and KSI905 did not. In contrast to the results of the spectrophotometric tributyrin assay, all enzyme preparations tested (including commercially purified esterase) were positive when examined by a tributyrin plate assay. The lack of specificity in the tributyrin plate assay emphasizes the need to interpret the results of tributyrin lipolysis kinetically for assessing lipase activity in S. aureus.

Polyclonal B cell activation in ankylosing spondylitis

The peripheral blood lymphocyte response of patients with ankylosing spondylitis (AS) to several polyclonal B cell activators was investigated. No differences were found in the reactivity to pokeweed mitogen and protein A between patients and controls; in contrast, the peripheral blood lymphocyte response to Staphylococcus aureus strain Cowan I (SAC) was significantly higher in patients with AS than in controls. This responsiveness was not influenced either by the presence of the HLA-B27 antigen or by environmental factors or associated diseases, and it was higher in patients with active AS than in those with inactive disease. The percentage of circulating B cells was normal. The responses to T cell mitogens and the percentages of T cell subpopulations were similar in patients and in controls. The peripheral blood lymphocyte hyperactivity of patients with AS to SAC was associated with an increased in vitro production of immunoglobulins.

Mechanisms for the microbicidal activity of cationic proteins of human granulocytes

One oxygen-independent antimicrobial system of human granulocytes consists of granular chymotropsin-like cationic proteins possessing heat-stable microbicidal activity. For elucidation of the mode of action of the cationic protein, effects on bacterial synthesis of macromolecules, ion transport, and oxygen consumption have been studied. Inhibition of incorporation of radioactive precursors into protein, ribonulceic acid, and deoxyribonucleic acid of both Staphylococcus aureus and Escherichia coli was found concomitantly with inhibition of colony formation. Cationic protein inhibited 86Rb+ influx but did not increase the leakage of intracellular 86Rb+, indicating inhibition of energy-dependent membrane transport without a breakdown of the semipermeable character of the membrane. Oxygen consumption was inhibited. Mg2+ and Ca2+ displayed a protective effect against the microbicidal activity, indicating the operation of charge interactions between cationic protein and bacterial surface. The various effects of cationic protein were more pronounced with S. aureus than with E. coli, parallelling the microbicidal activity.

Staphylococcal protein A; its preparation and an application to rubella serology

Good yields of staphylococcal protein A are obtained by growing the staphylococcus Cowan type 1 on cellophane agar. The activity of these preparations in removing immunoglobulin G (IgG) from human serum can be readily measured by the Mancini radial-diffusion technique and the correct in-use dilution determined. Treatment with protein A of sera from women with a history of rubella may help in the identification of those having specific antibody in the IgM and IgA fractions. This relatively simple procedure may have worthwhile application in the diagnosis of rubella.

Staphylococcal enterotoxin B and nuclease production under controlled dissolved oxygen conditions

Enterotoxin B, nuclease, and total exoprotein production by Staphylococcus aureus strain S-6 was studied in a 0.5-liter fermentor system. While these extracellular products were elaborated over a wide range of aeration rates, maximal production occurred within the very narrow range of 125 to 150 cm(3) of air per min. The levels attained at the optimal aeration rate were not increased by maintaining a constant pH, although yield of enterotoxin:cell mass was highest at a constant pH of 7.0. During the growth cycle of the cultures, when aeration rate alone or aeration rate and pH were held constant, the dissolved oxygen (DO) levels, initially set at 100% of saturation, decreased to 5 to 10% 4 to 5 h after inoculation. The oxygen demand of the culture then maintained this level for an additional 4 to 6 h. This interval of low DO was characterized by maximal growth and exoprotein production. When the DO was controlled at a constant value throughout growth (by increasing or decreasing the airflow rate as appropriate), the culture demonstrated different optima for maximal growth and exoprotein production. A constant DO of 100% stimulated growth to extremely high densities, but the accumulation of toxin and nuclease was not observed. On the other hand, maintaining constant DO levels at 50 or 10% raised exoprotein levels higher than those achieved in a culture grown at the optimal aeration rate. Compared to the optimal aeration rate culture, the 10% DO culture yielded 20% more nuclease, 25% more toxin, and 40 to 50% more total exoprotein. These results indicate that it is the DO and not the aeration rate, per se, that is influential in controlling growth, toxin, nuclease, and total exoprotein production.

Slide agglutination method for the serological identification of Neisseria gonorrhoeae with anti-gonococcal antibodies adsorbed to protein A-containing staphylococci

A rapid slide agglutination test has been developed for the identification of Neisseria gonorrhoeae that are primarily detected as oxidase-positive colonies in gonococcal cultures. The technique is based on the specific nonimmune reactivity between the Fc portion of immunoglobulin (Ig)G and staphylococcal protein A. IgG molecules adsorbed to stabilized staphylococci will thereby become oriented with their antigen-reactive sites that are directed outwards. Protein A-containing staphylococci with unabsorbed anti-gonococcal antibodies gave positive co-agglutination reactions with gonococci but also with meningococci, some Moraxella, Haemophilus, and Pseudomonas strains. These crossreactions were eliminated by absorption of the anti-gonococcal antiserum with meningococcal and Moraxella organisms prior to the coating of reagent staphylococci. In the routine culture diagnosis of N. gonorrhoeae the use of specific gonococcal reagent staphylococci gave concordant results with fermentation procedures and immunofluorescent techniques.

New method for the serological grouping of Streptococci with specific antibodies adsorbed to protein A-containing staphylococci

A coagglutinating reagent has recently been developed and utilized in capsule typing of pneumococci. The reagent consists of stabilized staphylococci coated with specific antibody via the gamma globulin Fc-protein A reaction thereby orienting the antibody molecules with the antigen-reactive Fab parts outwards. Reagent staphylococci coated with antibodies directed against streptococcal group-specific antigens have been used in the present investigations. Overnight cultures of streptococci were treated with trypsin and then directly tested for coagglutination of selected reagent staphylococci on glass slides. In all, 179 strains of streptococci were analyzed by the method described. The results were compared with grouping by using Lancefield extracts in counter-immunoelectrophoresis and were shown to agree completely. The coagglutination method described proved to be accurate, rapid, and simple.