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The tremendous success of Staphylococcus aureus as a pathogen is due to the controlled expression of a diverse array of virulence factors. The effects of host environments on the expression of virulence factors and the mechanisms by which S. aureus adapts to colonize distinct host tissues are largely unknown. Vertebrates have evolved to sequester nutrient iron from invading bacteria, and iron availability is a signal that alerts pathogenic microorganisms when they enter the hostile host environment. Consistent with this, we report here that S. aureus senses alterations in the iron status via the ferric uptake regulator (Fur) and alters the abundance of a large number of virulence factors. These Fur-mediated changes protect S. aureus against killing by neutrophils, and Fur is required for full staphylococcal virulence in a murine model of infection. A potential mechanistic explanation for the impact of Fur on virulence is provided by the observation that Fur coordinates the reciprocal expression of cytolysins and a subset of immunomodulatory proteins. More specifically, S. aureus lacking fur exhibits decreased expression of immunomodulatory proteins and increased expression of cytolysins. These findings reveal that Fur is involved in initiating a regulatory program that organizes the expression of virulence factors during the pathogenesis of S. aureus pneumonia.

Absent azygos vein is a rare anomaly of the venous system, which is commonly an incidental finding, with only few publications reporting it. Due to the scarcity of cases, it is rarely reported with oesophageal atresia ± tracheoesophageal fistula (OA ± TOF), which is usually accompanied with cardiac anomalies in up to 80% of the cases. This association has only been reported thrice in literature. We report a 6-day-old female who was referred to our centre after diagnosis of OA + TOF. The patient had no associated anomalies apart from small patent foramen ovale and small ventricular septal defect; however, there was no functional compromise. Upon thoracoscopic exploration, azygos vein could not be visualised. Thoracoscopic repair was performed, and the postoperative period was uneventful. On follow-up, the patient had no postoperative complications. Absent azygos vein is a rare anomaly with few cases reported throughout the literature. Azygos vein is considered an important landmark intraoperatively because it guides the surgeon to the TOF site. Moreover, it might be important in other patients with major cardiac anomalies with abnormal venous drainage who might need further surgical correction.