Changes in the pattern of infection caused by Streptococcus pyogenes.

Area of Science:

• Microbiology
• Epidemiology
• Immunology

Background:

• Streptococcus pyogenes (Group A Streptococcus) is a significant human pathogen.
• M-protein typing is crucial for understanding serotype distribution and epidemiology.
• Reference laboratories play a key role in national surveillance of bacterial pathogens.

Purpose of the Study:

• To analyze the distribution of Streptococcus pyogenes M-types over a 7.5-year period.
• To identify trends in M-type prevalence associated with different clinical manifestations.
• To monitor changes in serotype dominance in response to potential epidemiological shifts.

Main Methods:

• Analysis of 12,469 Streptococcus pyogenes isolates submitted to a reference laboratory from January 1980 to June 1987.
• M-protein antigen typing of isolates.
• Correlation of M-type with patient source (hospital, staff, community) and clinical outcome (nephritis, rheumatic fever, serious infections, deaths, scarlet fever, erysipelas, puerperal sepsis, pyoderma).

Main Results:

• A shift in M-type prevalence was observed, with types 6, 49, and 81 declining and types 1, 3, and 28 increasing.
• M-types 4 and 12 remained stable in prevalence.
• M-type 1 was strongly associated with fatal infections (80% of fatal cases since 1985) and erysipelas.
• M-type 3 was also associated with fatal infections.
• Specific M-types predominated in scarlet fever (3, 4), nephritis (1, 4, 12, 49), skin infections (49, 81), and puerperal sepsis (28).
• The M-typability rate was high at 97%.

Conclusions:

• Significant epidemiological shifts in Streptococcus pyogenes M-types occurred during the study period.
• Certain M-types, particularly M-type 1 and M-type 3, are increasingly associated with severe and fatal infections.
• Ongoing surveillance and characterization of M-antigens are necessary, especially for strains causing pyoderma.