IsdC from Staphylococcus lugdunensis Induces Biofilm Formation under Low-Iron Growth Conditions

Staphylococcus lugdunensis is a coagulase-negative staphylococcus that is a commensal of humans and an opportunistic pathogen. It can cause a spectrum of infections, including those that are associated with the ability to form biofilm, such as occurs with endocarditis or indwelling medical devices. The genome sequences of two strains revealed the presence of orthologues of the ica genes that are responsible for synthesis of poly-N-acetylglucosamine (PNAG) that is commonly associated with biofilm in other staphylococci. However, we discovered that biofilm formed by a panel of S. lugdunensis isolates growing in iron-restricted medium was susceptible to degradation by proteases and not by metaperiodate, suggesting that the biofilm matrix comprised proteins and not PNAG. When the iron concentration was raised to 1 mM biofilm formation by all strains tested was greatly reduced. A mutant of strain N920143 lacking the entire locus that encodes iron-regulated surface determinant (Isd) proteins was defective in biofilm formation under iron-limited conditions. An IsdC-null mutant was defective, whereas IsdK, IsdJ, and IsdB mutants formed biofilm to the same level as the parental strain. Expression of IsdC was required both for the primary attachment to unconditioned polystyrene and for the accumulation phase of biofilm involving cell-cell interactions. Purified recombinant IsdC protein formed dimers in solution and Lactococcus lactis cells expressing only IsdC adhered to immobilized recombinant IsdC but not to IsdJ, IsdK, or IsdB. This is consistent with a specific homophilic interaction between IsdC molecules on neighboring cells contributing to accumulation of S. lugdunensis biofilm in vivo.     

The need for early treatment of clubfeet in peripheral hospitals in sub-Saharan Africa: a survey of clubfoot management in Zambia

In the developing world, neglected clubfoot often results in a permanent and disabling deformity with subsequent social implications. Data from the four organizations that manage clubfoot in Zambia were collected using clinic and operating room registries and analyzed using Fisher exact test. In the central hospitals in the capital city 65% (204/313 feet) of clubfeet were suitable for treatment by the Ponseti method compared with only 23% (38/166 feet) in the peripheral hospitals (P < 0.001, two-tailed Fisher's exact test). In the central hospitals only 14% (42/313 feet) of clubfeet required extensive surgery for neglected clubfeet compared with 29% (49/116 feet) in peripheral hospitals (P < 0.015, two-tailed Fisher's exact test). Patients from outside the capital have a higher percentage of neglected clubfeet that are no longer suitable for conservative management and require extensive, complex and costly surgical treatment. By allowing earlier access to less invasive procedures the burden of disability may be reduced.