Immune challenge by bacterial lipopolysaccharide (LPS) causes short-term behavioral changes indicative of depression. The present study sought to explore whether LPS is able to induce long-term changes in depression-related behavior and whether such an effect depends on mouse strain and social context. LPS (0.83 mg/kg) or vehicle was administered intraperitoneally to female CD1 and C57BL/6 mice that were housed singly or in groups of 4. Depression-like behavior was assessed with the forced swim test (FST) 1 and 28 days post-treatment. Group-housed CD1 mice exhibited depression-like behavior 1 day post-LPS, an effect that leveled off during the subsequent 28 days, while the behavior of singly housed CD1 mice was little affected. In contrast, singly housed C57BL/6 mice responded to LPS with an increase in depression-like behavior that was maintained for 4 weeks post-treatment and confirmed by the sucrose preference test. Group-housed C57BL/6 mice likewise displayed an increased depression-like behavior 4 weeks post-treatment. The behavioral changes induced by LPS in C57BL/6 mice were associated with a particularly pronounced rise of interleukin-6 in blood plasma within 1 day post-treatment and with changes in the dynamics of the corticosterone response to the FST. The current data demonstrate that immune challenge with LPS is able to induce prolonged depression-like behavior, an effect that depends on genetic background (strain). The discovery of an experimental model of long-term depression-like behavior after acute immune challenge is of relevance to the analysis of the epigenetic and pathophysiologic mechanisms of immune system-related affective disorders.

Background and PurposeImmune challenge of mice with Bacille Calmette–Guérin (BCG) has been reported to cause transient weight loss and a behavioural sickness response. Although BCG-induced depression involves the kynurenine pathway, weight loss occurs independently of this factor. Because neuropeptide Y (NPY) and peptide YY (PYY) are involved in the regulation of food intake, we hypothesized that they play a role in the BCG-induced weight loss.Experimental ApproachMale wild-type, PYY knockout (PYY−/−), NPY knockout (NPY−/−) and NPY−/−;PYY−/− double knockout mice were injected with vehicle or BCG (approximately 108 colony-forming units per mouse), and their weight, locomotion, exploration and ingestion were recorded for 2 weeks post-treatment.Key ResultsDeletion of PYY and NPY aggravated the BCG-induced loss of body weight, which was most pronounced in NPY−/−;PYY−/− mice (maximum loss: 15%). The weight loss in NPY−/−;PYY−/− mice did not normalize during the 2 week observation period. BCG suppressed the circadian pattern of locomotion, exploration and food intake. However, these changes took a different time course than the prolonged weight loss caused by BCG in NPY−/−;PYY−/− mice. The effect of BCG to increase circulating IL-6 (measured 16 days post-treatment) remained unaltered by knockout of PYY, NPY or NPY plus PYY.Conclusions and ImplicationsThese data show that NPY and PYY are both required to protect from the action of BCG-evoked immune challenge to cause prolonged weight loss and disturb energy balance. The findings attest to an important role of NPY and PYY in orchestrating homeostatic reactions to infection and immune stimulation.

BackgroundDifferent research groups have identified microorganisms on breast implants by sonication with significant correlation to the rate of capsular contracture. This substantiated the hypothesis of an infectious etiology of capsular contracture. However, no clinical consequence has been drawn from these results yet. Aim of this study was to review sonication results from breast implants and to evaluate the current preoperative antibiotic regime for breast-implant surgery.MethodsWe compared breast implant sonication culture results from published reports and our own database. Current perioperative antibiotic recommendations were compared with the susceptibility profile of the found organisms.ResultsWe found Coagulase-negative staphylococci and Propionibacteria to be the main group of microorganism found by sonication on explanted breast implants. Most guidelines recommend cephalosporins for preoperative antibiotical prophylaxis for breast-implant surgery.ConclusionThere is a discrepancy between antibiotic activity of commonly used antibiotics for preoperative prophylaxis of surgical site infections, and microorganisms found by sonication on breast implants, suspected to trigger the formation of capsular contracture. A targeted antibiotic prophylaxis for breast implant surgery with glycopeptides (e.g. Vancomycin) should be considered for the prevention of capsular contracture.