Unilateral lymphadenitis caused by community-associated methicillin-resistant Staphylococcus aureus ST834 strain

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a global concern, primarily as a cause of skin and soft tissue infections, particularly in young people. Here, we describe a case of unilateral multiple lymphadenitis caused by the CA-MRSA sequence type (ST) 834 strain. A previously healthy 15-year-old girl was referred to our hospital with fever and swollen lymph nodes in the right axillary, cubital, and groin regions. Imaging examinations revealed enlargement of the lymph nodes in these areas but no swelling in any other lymph nodes. The patient had self-destructive lymph nodes in her groin. MRSA was detected in all swollen lymph node samples. Antimicrobial susceptibility tests showed that MRSA was susceptible to clindamycin and levofloxacin, leading to the suspicion of CA-MRSA. Genetic analysis revealed that all strains were ST834 and carried the staphylococcal cassette chromosome mec IV and the toxic shock syndrome toxin-1 gene but not the Panton-Valentine leukocidin gene. The patient was treated with linezolid followed by oral clindamycin. This was a rare case of unilateral multiple lymphadenitis caused by ST834 CA-MRSA. Although ST834 strains are rarely reported, lymphadenitis has been frequently reported and is considered more likely to cause lymphadenitis than other CA-MRSA strains.