A Double Escapee Toll-like receptors (TLRs)—TLR2 and TLR7—are thought to contribute to the sensing of Gram-positive bacteria like Staphylococcus aureus and Streptococcus pneumoniae by the immune system. Mice deficient in these receptors, however, are still sensitive to infection with these bacteria. Oldenburg et al. (p. 1111 , published online 19 July) demonstrate that TLR13 also plays a role in detecting Gram-positive bacteria. TLR13 recognized a conserved region in the peptidyl transferase loop of bacterial 23S ribosomal RNA. Intriguingly, this same sequence is modified by specific methyltransferases that confer resistance to erythromycin. Indeed, erythromycin-resistant bacteria were no longer detectible by TLR13.

TLR13 Recognizes Bacterial 23 S rRNA Devoid of Erythromycin Resistance–Forming Modification