A probable food-borne outbreak of pharyngitis after a massive rainstorm in Beijing, caused by emm89 group A Streptococcus rarely found in China

On July 28, 2012, it was reported that over 20 members of staff of a film crew with pharyngitis visited a hospital in Beijing, China. We conducted a rapid investigation of this outbreak. From July 8, 2012, this film crew with 140 members of staff settled in a town, Beijing to make a film. Their accommodation and food were provided by local vendors. On July 21, the area where the film crew was located was hit by an unprecedented massive rainstorm in Beijing, and the provision of domestic water was compromised. Twenty-eight pharyngitis cases were identified in this outbreak, and the attack rate was 20% (28/140). The date of illness onset of the 28 cases was between midday of July 26 and midday of July 27. Eight group A Streptococcus (GAS) isolates were recovered from pharyngeal swabs of 15 cases. All the isolates belonged to emm89 by emm typing, with resistance to erythromycin, clindamycin, and tetracycline. The onset of illness for the cases in this GAS pharyngitis outbreak fell within a 24-h period and there were no secondary cases in the following 7 days even though no isolation measures were taken and shooting of the film continued, which suggested that this outbreak might have derived from a common-source exposure. As a rainstorm preceding the outbreak influenced the provision of domestic water in the area where the film crew were resident, the probability of contamination of their food was increased. Therefore, we presumed that this might be a food-borne outbreak. Food-borne outbreaks of GAS pharyngitis have been reported in many countries,1Levy M. Johnson C.G. Kraa E. Tonsillopharyngitis caused by foodborne group A Streptococcus: a prison-based outbreak.Clin Infect Dis. 2003; 36: 175-182Crossref PubMed Scopus (26) Google Scholar, 2Ertugrul B.M. Erol N. Emek M. Ozturk B. Saylak O.M. Cetin K. Sakarya S. Food-borne tonsillopharyngitis outbreak in a hospital cafeteria.Infection. 2012; 40: 49-55Crossref PubMed Scopus (4) Google Scholar but not in China. This outbreak was caused by emm89 GAS, rarely found in China.3Chen M. Yao W. Wang X. Li Y. Chen M. Wang G. et al.Outbreak of scarlet fever associated with emm12 type group A Streptococcus in 2011 in Shanghai, China.Pediatr Infect Dis J. 2012; 31: e158-e162Crossref PubMed Scopus (38) Google Scholar, 4Liang Y. Liu X. Chang H. Ji L. Huang G. Fu Z. et al.Epidemiological and molecular characteristics of clinical isolates of Streptococcus pyogenes collected between 2005 and 2008 from Chinese children.J Med Microbiol. 2012; 61: 975-983Crossref PubMed Scopus (43) Google Scholar, 5Jing H.B. Ning B.A. Hao H.J. Zheng Y.L. Chang D. Jiang W. Jiang Y.Q. Epidemiological analysis of group A streptococci recovered from patients in China.J Med Microbiol. 2006; 55: 1101-1107Crossref PubMed Scopus (39) Google Scholar However, emm89 GAS has been one of the most predominant emm types in invasive GAS infections in European countries,6Darenberg J. Luca-Harari B. Jasir A. Sandgren A. Pettersson H. Schalen C. et al.Molecular and clinical characteristics of invasive group A streptococcal infection in Sweden.Clin Infect Dis. 2007; 45: 450-458Crossref PubMed Scopus (146) Google Scholar, 7Plainvert C. Doloy A. Loubinoux J. et al.Invasive group A streptococcal infections in adults, France (2006–2010).Clin Microbiol Infect. 2012; 18: 702-710Crossref PubMed Scopus (72) Google Scholar and a marked expansion of emm89 strains has occurred in Canada.8Shea P.R. Ewbank A.L. Gonzalez-Lugo J.H. Martagon-Rosado A.J. Martinez-Gutierrez J.C. Rehman H.A. et al.Group A Streptococcus emm gene types in pharyngeal isolates, Ontario, Canada, 2002–2010.Emerg Infect Dis. 2011; 17: 2010-2017Crossref PubMed Scopus (58) Google Scholar All emm89 isolates in this study were resistant to erythromycin, clindamycin, and tetracycline, which is rare in other countries.7Plainvert C. Doloy A. Loubinoux J. et al.Invasive group A streptococcal infections in adults, France (2006–2010).Clin Microbiol Infect. 2012; 18: 702-710Crossref PubMed Scopus (72) Google Scholar, 9Rivera A. Rebollo M. Miro E. Mateo M. Navarro F. Gurgui M. et al.Superantigen gene profile, emm type and antibiotic resistance genes among group A streptococcal isolates from Barcelona, Spain.J Med Microbiol. 2006; 55: 1115-1123Crossref PubMed Scopus (58) Google Scholar This is the first probable food-borne outbreak of GAS pharyngitis reported in China. Given the possible role of the rainstorm in this outbreak, it is suggested that not only enteric diseases, but respiratory diseases should be closely monitored after a rainstorm. In light of the circulation of emm89 GAS in many countries and this outbreak being caused by emm89, ongoing surveillance of emm89 GAS is warranted in China, and changes to water purification and food preparation should be considered after a rainstorm. Supported by grants from the Beijing Nova Program of Beijing Science and Technology Commission (2011047) and National Key Program for Infectious Disease of China (2012ZX10004215-003-001). Ethical approval: This study was approved by the Institutional Review Board and Human Research Ethics Committee of Beijing Center for Disease Prevention and Control. Conflict of interest: No conflict of interest to declare.

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