Biomedical subjects
J O Cohen
Publications and source records attributed to J O Cohen.
Identification of Salmonella O antigens by coagglutination.
This study concerns the preparation of reagents for identifying the somatic O antigens of Salmonella enteritidis. Coagglutination reagents (COAGs) with antibody fixed to killed and stabilized protein A-bearing staphylococci were prepared with antisera which were used for identifying the somatic O antigens of S. enteritidis by the slide agglutination test. The reactions of the COAGs were compared with those obtained with the grouping antisera in routine slide agglutination tests in which 41 or more serologically different Salmonella strains, representing most of the known groups, were used. One-third of the COAGs gave identical reactions to those of the slide agglutination antisera. The reactions of the other COAGs varied from the slide agglutination antisera results, some by many reactions and others by only a few. The coagglutination procedure was more reactive than the routine slide agglutination test and resulted in cross-reactions which were not observed in the original grouping antisera. More COAGs were specific when they were tested with alcohol-treated cultures than with live cultures. Coagglutination conserves antiserum, allowing about 12 times as many tests for a given volume of group-specific glycerolized antiserum as does the slide agglutination method.
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.
Simple procedure for production by group C streptococci of phage-associated lysin active against group A streptococci.
Phage-associated lysin of high potency was prepared by growing the host group C streptococcal strain 26RP66 in a semisynthetic medium. The lysin was stabilized by adding dithiothreitol and neutralized ethylenediaminetetraacetic acid (EDTA) to facilitate further concentration and partial purification. The lysin remained active when stored at -65 C for 1 year. Lysin was active against all strains of group A streptococci tested and was more active against living cells than heat-killed cells. The procedure outlined is practicable for most bacteriological research laboratories and does not require column purification or other complex biochemical procedures. It should be useful to any laboratory which requires small amounts of lysin to produce L-forms and protoplasts or to release streptococcal antigens.
Serological typing of staphylococci for epidemiological studies.
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Effect of culture medium composition and pH on the production of M protein and proteinase by group A Streptococci.
The effects of pH, yeast extract, and neopeptone on the production of extracellular proteinase and M protein by group A streptococci were studied with a type 1 strain capable of producing both M protein and proteinase. The strain DS 2036-66 grew moderately well in a semisynthetic broth. M protein was produced without adding peptides to the medium. When added to a medium with 1% glucose, yeast extract (0.1%) was found to stimulate both growth and proteinase formation. Limiting the glucose to 0.25% prevented a drop in pH below 6.7 and prevented proteinase formation. Although less growth occurred with limited glucose, M protein of high specific activity was produced with an actual increase in acid-extractable M protein during the stationary phase of growth. When the medium was buffered at pH 7.85 with tris(hydroxymethyl)aminomethane buffer, 0.5% neopeptone prevented proteinase formation. This was true even in the presence of 1% glucose and 0.1% yeast extract, which resulted in a fall in pH to about 4.8 by 48 hr. Growth was greater than in Todd Hewitt broth, but the specific activity of M protein was considerably less than that found in the medium with glucose limited to 0.25%. Neopeptone was found to have little direct action on crude streptococcal proteinase. Instead, the evidence suggested that neopeptone somehow prevents proteinase elaboration. Yeast extract, on the other hand, appears to stimulate proteinase elaboration. To prevent proteinase formation, neopeptone must be added early, during the logarithmic phase of growth or at the start. In contrast, when yeast extract was added as late as 24 hr, it resulted in the elaboration of extracellular proteinase and in the decline of M protein. When 38 M nontypable strains from the diagnostic laboratory were tested for proteinase activity under conditions similar to those used in the diagnostic laboratory, only six produced much proteinase.
Quantitative aspects of the M protein capillary precipitin test.
A capillary procedure for quantitatively determining M protein is described. Capillaries were filled with measured amounts of serum and streptococcal extract. The capillaries were incubated, and then centrifuged to pack the precipitates. The relative sizes of the precipates were compared by a determination of the weights of their paper images (obtained by reflection from a microscope). Meaningful dilution curves were determined by this method. Variations of pH from 6 to 8 had little effect on the M protein precipitin test, and the test was not seriously affected by variations of the NaCl concentration from 0.85 to 4.67%. The addition of divalent ions (Ca(++) and Mg(++)) did not influence the results. This test can be used to make quantitative comparisons of M protein preparations and to titrate type-specific antisera.
Bacterial interference in the treatment of recurrent staphylococcal infections in a family.
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Correlation between staphylococcal serotypes with 263-1 factor and phage group 1.
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Serologic typing of staphylococci of epidemiological significance.
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