An 5 Group A Streptococcal Outbreak Among Workers in a Factory Manufacturing Telephone Accessories.

Ranked among the top10 infectious causes of death worldwide, group A (GAS) causes small- and large-scale outbreaks, depending on the trigger as transmission of a GAS strain or expansion of predominant clones. In China, GAS infections other than scarlet fever are not notifiable. In Shanghai, an epidemiological investigation was initiated after two successive severe pneumonia cases with one death in a digital factory, from where outbreaks are less widely reported. The investigation was performed using typing, pulsed-field gel electrophoresis (PFGE) typing, superantigen profiling, and genome analysis. This enabled characterization of relatedness among the outbreak isolates and identification of the mobile genetic elements present. Among 57 patients with respiratory symptoms investigated in the factory, 5 GAS strains were isolated from 8 patients. The eight GAS infection cases comprising one fatal severe pneumonia case, six influenza-like illness cases, and one pharyngitis case. Two risk factors were identified: adult with an age of 18-20 years and close contact with a GAS patient or carrier. GAS attack rate was 14.0% (8/57), and GAS carriage rate was probably around 2.7% (14/521) based on surveys in two nearby districts. All the 10 outbreak associated isolates were assigned to 5 and sequence type ST-99 (5/ST-99), harbored superantigen genes , and , and were assigned to two similar PFGE patterns (clones). Among the outbreak associated isolates, all carried with resistance to erythromycin and inducible resistance to clindamycin, and eight (80%) carried a gene with resistance to tetracycline. Among the 14 carriage isolates, 12 were 12/ST-36, and 2 were 1/ST-28, all with superantigen genes , and . All the carriage isolates harbored and with resistance to erythromycin, clindamycin, and tetracycline. Genome analysis showed the two outbreak clones were closely related and possessed new prophages carrying virulence gene and antibiotic resistance genes of and , which were not found in the 5 reference strain Manfredo. This is the first report of a GAS outbreak in this type of workplace. The outbreak was caused by two closely related 5 clones that differed from the predominant types circulating in China.