The role of macrophages in the innate immune response to Streptococcus pneumoniae and Staphylococcus aureus: mechanisms and contrasts.

Macrophages are critical mediators of innate immune responses against bacteria. The Gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus express a range of virulence factors, which challenge macrophages' immune competence. We review how macrophages respond to this challenge. Macrophages employ a range of strategies to phagocytose and kill each pathogen. When the macrophages capacity to clear bacteria is overwhelmed macrophages play important roles in orchestrating the inflammatory response through pattern recognition receptor-mediated responses. Macrophages also ensure the inflammatory response is tightly constrained, to avoid tissue damage, and play an important role in downregulating the inflammatory response once initial bacterial replication is controlled.

Hypoglycaemia associated with co-trimoxazole use in a 56-year-old Caucasian woman with renal impairment.

Here we present a case of refractory hypoglycaemia associated with use of the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX). This was used to treat Pneumocystis jirovecii pneumonia (PCP) infection. The patient had significant pre-existing renal impairment with a kidney transplant in situ. Refractory hypoglycaemia occurred 5 days after starting the antibiotic and persisted for 36 h after its cessation. SMX contains the same sulphanilamide structural group as the oral hypoglycaemic agents called sulphonureas. SMX could therefore act as an insulin secretagogue. The inappropriately raised insulin and c-peptide levels seen in our patient support this theory. The 5-day asymptomatic period would allow sufficient time for the drug to accumulate and the extended period seen after its cessation would be seen in a dose-dependent side effect. Following 3 days of observation and continuous glycaemic support on the High Dependency Unit she was discharged back to the ward, with no further occurrence of hypoglycaemia.

Clinical review: a systematic review of corticosteroid use in infections.

Traditional teaching suggests that corticosteroids should be avoided during acute infectious episodes for fear of compromising the immune response. However, the outcome benefit shown through steroid administration in early septic shock implies this paranoia may be misplaced. We therefore performed a systematic review of the literature to identify the current strength of evidence for the use of corticosteroids in specified infections, and to make appropriate graded recommendations.