Protein and energy metabolism in chronic bacterial infection: studies in melioidosis

Chronic infection is often accompanied by a wasting process, the metabolic basis of which is not fully understood. The aims of the present study were to measure protein and energy metabolism in patients with melioidosis (a serious and antibiotic-refractory Gram-negative bacterial infection which is endemic in South-East Asia) in order to define the metabolic abnormalities that might contribute to wasting. Whole-body protein turnover was measured using the [13C]leucine technique, both in the fasted state and while consuming a high-energy meal. Resting energy expenditure was measured by indirect calorimetry, and total energy expenditure by the bicarbonate/urea method. Results were normalized for fat-free mass, as estimated from skinfold thickness. Protein turnover was increased in melioidosis patients compared with healthy controls during fasting (170.9 compared with 124.1 µmol·kg-1·h-1; P = 0.04), but the net rate of catabolism (22.2 compared with 20.5 µmol·kg-1·h-1; P = 0.77) and the anabolic response to feeding were similar in the two groups. Resting energy expenditure was higher in melioidosis patients compared with controls (191.4 and 157.3 kJ·kg-1·day-1 respectively; P = 0.04), but total energy expenditure (measured in a separate group of eight patients with melioidosis) was low (192.1 kJ·kg-1·day-1). In conclusion, this study found no evidence of metabolic causative factors, such as accelerated net protein catabolism during fasting, a blunted anabolic response to feeding or increased daily energy expenditure, and therefore suggests that reduced energy intake is the prime cause of wasting. The observed normal response to feeding should encourage nutritional approaches to prevent wasting.