Summary
Epidemiological and clinical observations on streptococcal infections in 156 Egyptian school children aged 6 to 12 yr were obtained by prospective bacteriological, serological and clinical surveys from 1967 to 1970.
The yearly recovery rate of group-A streptococci from the throat varied from 13 per cent. to 24 per cent. The seasonal variations showed a peak during the late autumn and winter and a minimal rate in the summer months. The carrier rate in each of four school grades varied independently, an indication that the classroom, more than any other area of the school, is a primary locus of exposure and transmission.
The prevalence of the group-A streptococcal carrier state was assessed from the long-term observation of the study population. In 7 per cent. of the children, more than 25 per cent. of the monthly throat cultures were positive in a 3-yr period. Thirteen per cent. of the children had fewer than 5 per cent. of throat cultures positive. In most of the children, however, there were marked shifts in the percentage of positive monthly throat cultures from one year to the next.
The attack rate of streptococcal infections, defined as a throat culture positive for group-A streptococci with a concomitant rise of ASO, was 6 per 1000 per week.

A Three-Year Prospective Study of Streptococcal Infections in a Population of Rural Egyptian School Children

Extracellular neuraminidase production by group A streptococci was examined in 92 strains. Fourteen of these strains produced appreciable amounts of enzyme; 12 of the neuraminidase-producing strains belonged to T types 1, 4, and 12. Production of the enzyme paralleled bacterial growth in culture and was maximal in medium containing 0.2% glucose. The enzyme produced by one of these strains was partially purified by ammonium sulfate fractionation and filtration on G-200 Sephadex. Its molecular weight was estimated at 90,000. Activity was optimal at pH 5.7 and in the presence of 0.01 to 0.03 M calcium and magnesium cations. The enzyme was stable at temperatures of 4 and 37 degrees C for at least 24 h but was inactivated within 10 min at temperatures of 50 and 65 degrees C. The enzyme hydrolyzed 40% of the sialic acid in bovine submaxillary mucin, but was inactive on sialyl-lactose, porcine submaxillary mucin, oligosaccharides derived from porcine mucin, or human orosomucoid. The Km value for this enzyme with bovine submaxillary mucin as substrate was in the order of 3.6 x 10(-4) M.

Properties of extracellular neuraminidase produced by group A streptococcus.

(1976). A Review of The Microbiological Techniques for the Isolation and Identification of Streptococci. CRC Critical Reviews in Clinical Laboratory Sciences: Vol. 6, No. 4, pp. 287-317.

A review of the microbiological techniques for the isolation and identification of streptococci.

A strain of group A Streptococcus which was virulent but M-nontypable was isolated from patients in a hospital nursery during an epidemic. This strain, Boston 11, reacted in T-agglutination tests with antisera for types 9 and 11, an unusual combination. A comparison of this strain with Lancefield's M-11 strain (NCDC SS-721) and Alabama 11 (Provisional 61) revealed three serologically related but distinct strains. Antiserum produced with the Boston 11 strain exhibited similar reactivity with all three “11” strains as well as with M-9 (SS-501) as demonstrated in precipitin tests. Immunodiffusion studies indicated that the Boston 11 antigen was partially identical with the M-11 and M-9 strains and shared at least one antigen with the Alabama 11 strain. The Boston 11 antiserum could be made specific for precipitin tests, but bactericidal activity for the Alabama 11, M-11, and Boston 11 strains was essentially negative.

Antigenic variation in group A streptococci: types 11 and 9.

Immunological and epidemiological characteristics of M1T1 and M1T8 (T8, 25, Imp.19) group A streptococci isolated in Egypt have been described. Both strains possess a common M1 antigen. The M1T8 strains possess a second antigen which has the immunological and biological characteristics of M protein. The M1T1 strains do not possess this second M antigen. Absorbed rabbit antisera which are specific for this second antigen do not react with extracts of any of the known M protein serotypes. This second antigen is therefore a newly recognized M protein. The M1T1 and M1T8 strains had mutually exclusive geographical and temporal distributions. This finding may have been a consequence of the immunity which occurred after the initial occurrence of the M1T8 strain.

Newly recognized distinctive M protein associated with certain M type 1 group A streptococci.

The temperature of incubation affected the typability of beta-hemolytic group A streptococci by T-agglutination tests. When strains could not be typed after routine incubation at 30 C, they were incubated at 22 to 25 C, and nearly a 10% increase in typability was achieved. The clinical source of the strains was related to their typability. Incubation at the lower temperature was required for successful typing of higher percentages of strains from the skin and other clinical sources than from the throat. Sixty per cent of the skin strains were represented by six serotypes. Of these, 53% of the strains required incubation at 22 to 25 C before they could be typed.

Joseph F. Padula

Papers

Effect of Incubation Temperature on T-Agglutination Typing of Streptococcus pyogenes