• ​The Son​oma Department of Health Services (SDHS) and California Department of Public Health (CDPH) are investigating an Aeromonas outbreak linked to Tough Mudder adventure race events at the Sonoma Raceway on August 19 and 20, 2023.
• Healthcare providers should consider Aeromonas infections in individuals presenting with skin and soft tissue infections (SSTIs) who participated in the Tough Mudder events in Sonoma.
• Healthcare providers should c​​onsider obtaining wound cultures (and other cultures, if applicable) and performing antimicrobial susceptibility testing to guide antibiotic therapy.
  
• Initial empiric treatment should cover Aeromonas, as well as other bacteria that commonly cause SSTIs.
• Healthcare providers should report cases associated with this outbreak to their local health department.
  

​​​Background

Sonoma Department of Health Services (SDHS), in coordination with the California Department of Public Health (CDPH), is investigating an outbreak of skin and soft tissue infections (SSTIs) associated with Tough​​ Mudder, an adventure race involving extensive exposure to mud, held at the Sonoma Raceway on August 19 and 20, 2023.

Numerous race participants have experienced SSTIs (most frequently described as a pustular rash), along with other symptoms such as fever and headache. Multiple wound cultures have yielded Aeromonas.

Aeromonas are gram-negative bacteria that grow in freshwater and marine environments and can cause wound infections ranging from mild cellulitis to necrotizing fasciitis. Aeromonas strains may be resistant to antibiotics commonly used to treat SSTIs caused by other bacteria. In addition, Aeromonas infections have been associated with gastroenteritis, sepsis, and involvement of multiple extraintestinal sites.

Recommenda​​tions

Healthcare providers should ask patients presenting with SSTIs (especially folliculitis or pustular rash) about whether they participated in a Tough Mudder race at the Sonoma Raceway on August 19 and 20, 2023. In addition, healthcare providers should also​​ evaluate other symptoms among race participants as Aeromonas infections can affect other sites (e.g., respiratory, gastrointestinal). Healthcare providers caring for patients linked to this outbreak should strongly consider obtaining cultures and performing antimicrobial susceptibility testing to guide antibiotic therapy. If treatment is warranted, initial empiric treatment should cover Aeromonas, as well as other bacteria that commonly cause SSTIs. Limited antimicrobial susceptibility testing (AST) information to date has suggested that the Aeromonas isolated from patients are pan-susceptible, including to ciprofloxacin, doxycycline, and trimethoprim-sulfamethoxazole. Healthcare providers should report cases to their local public health department.

Resources

1. Aravena-Román M, Inglis TJ, Henderson B, Riley TV, Chang BJ. Antimicrobial susceptibilities of Aeromonas strains isolated from clinical and environmental sources to 26 antimicrobial agents. Antimicrob Agents Chemother. 2012 Feb;56(2):1110-2. doi: 10.1128/AAC.05387-11. Epub 2011 Nov 28. PMID: 22123695; PMCID: PMC3264277. 
   

2. Stevens DL, Bisno AL, Chambers HF, Dellinger EP, Goldstein EJ, Gorbach SL, Hirschmann JV, Kaplan SL, Montoya JG, Wade JC; Infectious Diseases Society of America. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America.​ Clin Infect Dis. 2014 Jul 15;59(2):e10-52. doi: 10.1093/cid/ciu444. Erratum in: Clin Infect Dis. 2015 May 1;60(9):1448. Dosage error in article text. PMID: 24973422. 
   

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