Most common causes of bacterial arthritis in children according to age

Age group	Most common bacteria
<3 months	Staphylococcus aureus (MSSA and MRSA)
	Group B Streptococcus (Streptococcus agalactiae)
	Gram-negative bacilli
	Neisseria gonorrhoeae
3 months to 3 years	S. aureus (MSSA and MRSA)
	Kingella kingae
	Group A Streptococcus (Streptococcus pyogenes)
	Streptococcus pneumoniae
	Haemophilus influenzae type b (Hib) (in incompletely immunized children in regions with low Hib immunization rates)
>3 years	S. aureus (MSSA and MRSA)
	Group A Streptococcus
	S. pneumoniae
	N. gonorrhoeae (in sexually active adolescents)

MSSA: methicillin-susceptible S. aureus; MRSA: methicillin-resistant S. aureus.

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