Partial Resistance to Septoria Tritici Blotch (Mycosphaerella graminicola) in Wheat Cultivars Arina and Riband.

ABSTRACT Partial resistance to Septoria tritici blotch (STB) and its inheritance were investigated in a doubled-haploid population of a cross between cvs. Arina and Riband. The former has good partial resistance whereas the latter is susceptible. In adult plant trials in polytunnels, STB disease scores were negatively correlated with heading date. Resistance was not specific to any of the three fungal isolates used in these tests. A quantitative trait locus (QTL) for partial resistance to STB was identified in Riband on chromosome 6B and is named QStb.psr-6B-1. No QTL controlling a major part of the Arina resistance was identified, suggesting that its resistance may be dispersed and polygenic. There was no correlation between the lines' mean disease scores at the seedling and adult stages, implying that partial resistance to STB is developmentally regulated. Seedling resistance to the isolate IPO323 was isolate-specific and controlled by a single gene in Arina, probably allelic with the Stb6 gene in cv. Flame that confers resistance to the same isolate. The implications of these results for wheat breeding programs are discussed.

The relationship between opacity factor and M protein in Streptococcus pyogenes.

Lancefield acid extracts of Streptococcus pyogenes, type 22 (T12, M22, OF positive) gave good yields of M protein and little opacity factor (OF), but sodium dodecyl sulphate (SDS) extracts contained high titres of OF (greater than 20000) and little M protein. Acid-extracted OF could be separated from M protein by Sepharose 4B chromatography, but some of the OF-positive fractions that did not precipitate with the absorbed homologous anti-M rabbit serum, were able to neutralise opsonic antibodies present in human serum. The isoelectric-focusing profiles of the two antigens showed partial similarity. Some strains of the OF-positive serotypes, e.g., M-types 22 and 49, lost both M antigen and OF activity on serial transfer in Todd-Hewitt broth, but this was not seen in a representative of M-type 60, and no M-negative OF-negative variants could be detected after six subcultures. Among the OF-negative serotypes some, e.g., M-types 5 and 6, were completely stable, whereas others, e.g., M-types 12, 55 and 57, lost their M antigens after serial subculture. One explanation is that the genes that code for M antigen are plasmid borne in some serotypes and, moreover, are carried on the same plasmid as the gene for OF in some OF-positive serotypes. However, analysis of cell lysates by agarose-gel electrophoresis failed to demonstrate the presence of plasmid DNA in any of the strains tested.

The opacity factor of group-A streptococci.

Cell-bound opacity factor (OF) was extracted with sodium dodecyl sulphate (SDS) to yield stable extracts with titres of greater than 20 000. The mol.-wt distributions of extracellular and SDS-extracted OF, determined by ultrafiltration or chromatography on Sepharose 4B, suggested that the high mol. wt (1 x 10(6)) of extracellular OF is due to aggregation, because cell-bound and extracellular OF in the presence of SDS had an average mol. wt of only 2 x 10(5). At least four apparent multiple-molecular forms (mol. wt 7.4-12.0 x 10(4)) of OF were detected by SDS polyacrylamide-gel electrophoresis. It seemed more probable that these were due to aggregation rather than the existence of different stable conformations. To explain the molecular-size distribution, the subunit would have to be as small as 1 x 10(4) but this was supported by the finding that OF can be detected after passing through a dialysis membrane provided that its "substrate", alpha 1-lipoprotein, is present on the other side. This raises the possibility that OF is associated with a carrier molecule. The isoelectric-focusing profiles of OF were complex and differed markedly with the method used to prepare OF. Extracellular OF had a simple profile with an isoelectric point of 4.0, whereas Triton-extracted OF was the most complex and formed three peaks, the position of which varied depending on whether the detergent was present or absent during focusing runs.

Minimum amount of penicillin prophylaxis required to control Streptococcus pyogenes epidemic in closed community.

The prophylaxis required to control an epidemic of Streptococcus pyogenes throat infection in a junior detention centre has been reported. In a further epidemic an attempt was made to determine the minimum amount of penicillin required to control the outbreak. Oral penicillin (0.5 g) given as a single daily dose for 10 days to all boys after entry proved effective. The added risk of relatively deprived adolescent boys developing rheumatic fever is stressed.

Streptococcal antibodies in patients with burn injuries.

Serum samples from 14 patients whose burns had become infected with streptococci of groups A (11 patients), C (one patient) or G (two patients), and from 19 burned patients without bacteriological evidence of streptococcal infection were examined for anti-streptococcal antibodies. Tests were made for anti-streptolysin O (ASO), anti-hyaluronidase (AH), anti-deoxyribonuclease B (anti-DNAase B) and antibody against M-associated protein (MAP). Sera from the patients with streptococcal infections were also examined, when this was practicable, for 'bactericidal' (anti-M) antibody and for antibody against the opacity factor (OF) of the infecting serotype. In patients infected with group A streptococci, the ASO response was generally poor, except in patients infected with strains of type T12/M12, and the AH response was rather similar, but most of the patients gave a rapid and vigorous anti-DNAase B response, except when the burn was small or colonization occurred very late. Antibody to the M and MAP antigens, and to OF (when the infecting strain formed this), was weak and transient, or absent, except in three of four patients infected with streptococci of type T12/M12.

Streptococcal infection in a Junior Detention Centre: a five-year study.

In 1972 more than 20% of boys admitted to a closed community (Junior Detention Centre) developed acute tonsillitis and group-A streptococci were isolated from more than 40% of all boys at some time during their stay of two months. The most common serotype was M-type 5, which has frequently been associated with rheumatic fever in other epidemics; four cases of rheumatic fever occurred between 1972 and 1977. Various methods were tried to eliminate the infection, but only full penicillin prophylaxis (0.25 g oral penicillin 4 times a day for 10 days) to all boys on entry appeared to be effective. In a sample of cases of acute tonsillitis, group-A haemolytic streptococci were isolated from 31.7% by the use of dry swabs or unenriched transport medium, but with enrichment medium duplicate swabs, 77.6% yielded positive results. We question the current practice in some laboratories of reporting positive cultures only when more than ten colonies of beta-haemolytic streptococci are present. In this survey viruses did not appear to be an important cause of acute tonsillitis. High titres of streptococcal antibodies (antistreptolysin O, anti-desoxyribonuclease B and anti-M associated protein) were found, not only in cases and carriers, but in boys on entry to the centre. This supports epidemiological evidence that adolescent boys are particularly prone to streptococcal throat infections.

Predominance of immunoglobulin G sub-class 3 among the complement-fixing antibodies to streptococcal M-associated protein.

During investigation of the absorption of group-A streptococcal antibodies from human sera by a protein A-positive Staphylococcus aureus strain, we found that the complement-fixing antibodies to M-associated protein (MAP) were only partially absorbed from the majority of sera tested, although they were shown to belong to the immunoglobulin G (IgG) class by density gradient centrifugation. In contrast, other streptococcal antibodies: anti-streptolysin O (ASO), anti-deoxyribonuclease B (anti-DNAase B), 'bactericidal' M antibody and anti-opacity factor (anti-OF), were completely absorbed from all but a minority of sera. We suggest that the complement-fixing antibodies to MAP may be of restricted heterogeneity and have an abnormal IgG sub-class distribution, with a marked predominance of IgG3 (the only sub-class that does not interact with protein A) over the IgG1 and IgG2 sub-class; IgG4 does not participate in complement fixation. The concentration and relative porportions of IgG sub-classes are believed to be genetically influenced, so our findings may have some bearing on the immune responsiveness of different individuals to streptococcal infection, and possibly have important implications in the development of the secondary sequelae.

Inhibition of beta-haemolysis by opacity factor in group A streptococci.

Group-A streptococci belonging to opacity-factor (OF)-positive M types were poorly haemolytic on horse-blood agar, but members of OF-negative M types, and M-negative variants of OF-positive strains gave good haemolysis. Horse-serum extracts of strains of OF-negative serotypes 6 and 12, and M-negative variant cultures of OF-positive serotypes 4 and 49, had higher titres of streptolysin S than did similar extracts of OF-positive, M-positive cultures of types 4 and 49. However, much larger amounts of streptolysin S could be extracted with ribonuclease (RNAase)-digested yeast ribonucleic acid (RNA) and M-positive OF-positive cultures treated in this way gave extracts at least as strong as did their M-negative variants or the OF-negative strains. Extraction of streptolysin S from OF-negative strains by serum could be inhibited by previous incubation of the serum with extracellular OF, suggesting that the production of diffusable OF by M-positive variants of OF-positive serotypes interferes with the extraction of streptolysin S by serum and leads to poor haemolysis on blood agar. The haemolysis of all strains on blood agar was greatly improved by the incorporation of 0-1% (w/v) RNAase-digested yeast RNA into the medium, but the improvement was most marked in OF-positive serotypes.

Immunological heterogeneity among the M-associated protein antigens of group-A streptococci.

Different serotypes of group-A streptococci share common antigens that are closely associated with the type-specific determinant of M protein. By the use of selected human sera containing antibody to these M-associated antigens, we have shown that group-A streptococci can be divided into three categories. The majority of the opacity-factor-negative respiratory serotypes possess a shared M-associated antigen or antigens, to which high titres of antibody are common in patients with rheumatic fever, or patients recovering from upper respiratory infections with certain opacity-factor-negative serotypes. The antibody in these sera has a demonstrable but limited affinity for the M-associated antigens of strains belonging to a second category of M types, the majority of which are opacity-factor-positive serotypes of "throat" or "skin" origin. A third group, consisting mainly of opacity-factor-negative pyoderma serotypes, gave variable results and seemed to be intermediate between the other two categories. Complement-fixation-inhibition tests and absorption studies showed a marked degree of cross-reactivity between the M-associated antigens of the three categories.

Outbreak of idiopathic erysipelas in a psychiatric hospital.

In an outbreak of idiopathic erysipelas ten women patients, aged 42-74, in a long-stay unit of a psychiatric hospital were simultaneously affected. Group A streptococci M-type 1 were isolated from two isolated from two patients with erysipelas and 18 carriers, but subsequent serological tests for type-specific antibody, antistreptolysin O, and anti-deoxyribonuclease B showed that the infection had been widespread in the unit. Treatment with ampicillin proved ineffective and to prevent relapse it was substituted by a standard course of intramuscular penicillin. This seems to be the first epidemic of this type to be reported and certainly the first outbreak of idiopathic erysipelas to be investigated by modern serological techniques.

An outbreak of streptococcal sore throat and rheumatic fever in a Royal Air Force training camp; significance of serum antibody to M-associated protein.

A large outbreak of streptococcal sore throat in a Royal Air Force Training Camp resulted in five cases of rheumatic fever among the 16- to 18-year-old apprentices, and one case in a 33-year-old airman. The most prevalent type of group A streptococcus isolated from throat swabs was M-type 5 and there was serological evidence that at least four of the rheumatic fever (R.F.) cases were due to this type.Among the patients with uncomplicated throat infection the anti-streptolysin O (ASO) and anti-deoxyribonuclease B (anti-DNAase B) responses were in general rather low, even where there was evidence of protective antibody against type 5. However, a combination of the results of the ASO and anti-DNAase B tests gave an estimate of the extent of streptococcal infection 15-25% higher than did either test alone.The titres of antibody to M-associated protein (MAP) were >/= 60 in all the R.F. patients, and in about 50% of the other patients with ASO titres >/= 200. This figure is unusually high compared with data from several other outbreaks of streptococcal infection due to different serotypes and also greatly exceeds comparable figures for cases of sporadic sore throat and acute glomerulonephritis.

Antibody to streptococcal opacity factor in human sera.

Two tests are described for detecting antibody to the type-specific opacity factor (OF) of group A streptococci. This antibody was detected among patients convalescent from streptococcal sore throat in two communities in which outbreaks due to opacity factor-producing strains of group A streptococci occurred.In an outbreak due to streptococci of M-type 22 there was a close correspondence between the distribution of anti-OF and of bactericidal M-antibody for the type. In a smaller outbreak due to M-type 58 streptococci, however, M-antibody was detected more often than antibody to OF.

An M-associated protein antigen (MAP) of group A streptococci.

A streptococcal antigen that is closely associated with the M-antigen, but is not type specific can be detected by means of a complement-fixation test in extracts of M-positive, but not of M-negative, variants of group A streptococci. Purification of acid extracts results in a concomitant increase in the purity both of the type-specific M-antigen and of the M-associated protein (MAP). Antibody to MAP is present in the sera of patients who have had streptococcal infection. The highest titres are found in patients with rheumatic fever.