SAA4 and bacterial arthritis: The transposon mutagenesis screen also identified a predicted glycosyltransferase gene necessary for capsule production in strain KK01, a stable nonspreading/noncorroding derivative of septic arthritis isolate 269–492, and designated csaA. Targeted deletion of csaA results in a complete absence of both intracellular and extracellular capsular polysaccharide, suggesting that this gene is involved in capsule synthesis (42).