Which organism is the most common cause of septic arthritis in children?

Which organism is the most common cause of septic arthritis in children?

• A. Streptococcus pneumoniae
• B. Haemophilus influenzae
• C. Staphylococcus aureus
• D. Neisseria gonorrhoeae

Answer: (C)

The main idea is recognizing which organism most commonly causes septic arthritis in children, and that is Staphylococcus aureus. It’s the leading cause because it’s a frequent inhabitant of the skin and forms of skin infection can seed the bloodstream, delivering bacteria to a joint. Once in the joint, S. aureus uses its virulence factors to adhere to and invade synovial tissue and to survive in the inflammatory environment, triggering a rapid, purulent joint infection. In kids, Staphylococcus aureus consistently stands out as the top causative organism for septic arthritis, more so than other bacteria. For context, Haemophilus influenzae used to be a common cause before Hib vaccination, but its incidence has fallen dramatically. Streptococcus pneumoniae can cause joint infections but is less common than S. aureus. Neisseria gonorrhoeae mainly affects sexually active adolescents and can cause septic arthritis, but it is not the usual pathogen in the broader pediatric population. Clinically, septic arthritis presents with a single swollen, painful joint, fever, and decreased movement. Joint fluid analysis typically shows high neutrophils, and Gram staining might reveal Gram-positive cocci in clusters consistent with Staphylococcus aureus, with culture confirming the organism.

The main idea is recognizing which organism most commonly causes septic arthritis in children, and that is Staphylococcus aureus. It’s the leading cause because it’s a frequent inhabitant of the skin and forms of skin infection can seed the bloodstream, delivering bacteria to a joint. Once in the joint, S. aureus uses its virulence factors to adhere to and invade synovial tissue and to survive in the inflammatory environment, triggering a rapid, purulent joint infection.

In kids, Staphylococcus aureus consistently stands out as the top causative organism for septic arthritis, more so than other bacteria. For context, Haemophilus influenzae used to be a common cause before Hib vaccination, but its incidence has fallen dramatically. Streptococcus pneumoniae can cause joint infections but is less common than S. aureus. Neisseria gonorrhoeae mainly affects sexually active adolescents and can cause septic arthritis, but it is not the usual pathogen in the broader pediatric population.

Clinically, septic arthritis presents with a single swollen, painful joint, fever, and decreased movement. Joint fluid analysis typically shows high neutrophils, and Gram staining might reveal Gram-positive cocci in clusters consistent with Staphylococcus aureus, with culture confirming the organism.