Diarrhoea remains one of the commonest illnesses among infants, and is also one of the major causes of mortality in developing countries (1). Infants who are not breast-fed exhibit a higher incidence and severity of diarrhoeal illnesses, demonstrating the connection between infant feeding practices and the risk of diarrhoea (2). The relative risk of diarrhoea-associated death among completely weaned infants(a) is 14 times higher than of their exclusively breast-fed counterparts (3). The introduction of complementary foods is concomitant with an increased risk of diarrhoea (4, 5). Food, particularly milk, may serve as a medium for the multiplication of enteric bacterial pathogens and/or the production of enterotoxins (6-8), accounting for a substantial proportion of diarrhoeal diseases and associated malnutrition among infants. (9). Nevertheless, the importance of safe food preparation practices in the prevention of diarrhoeal diseases has often been neglected (10), even though numerous studies have demonstrated that complementary foods prepared under unhygienic conditions are frequently and grossly contaminated (4, 6-8, 11-16).
Most of the studies on contamination of complementary foods have evaluated rural communities (4, 6, 8, 11), where living conditions are quite different from those in metropolitan areas of developing countries. In the latter, the low-income population can benefit from easier access to basic infrastructures, as well as to education and health care, which could influence household food preparation practices.
The present study investigated bacterial contamination in the lacteal contents of feeding bottles of infants belonging to families of high (HSE) and low (LSE) socioeconomic levels in the metropolitan area of Sao Paulo, Brazil. The relationships between contamination, socioeconomic level and feeding bottle preparation practices were also evaluated.
Materials and methods
The study was carried out in the metropolitan area of Sao Paulo (population, 15 million) in south-eastern Brazil, the most industrialized city in Latin America. Sao Paulo has adequate water and electricity supplies, good solid waste collection but deficient sewerage. It also experiences the usual range of urban problems, including pollution, overcrowding, traffic-jams, crime, and unemployment.
In Brazil, socioeconomic class is frequently associated with a particular type of health care system. Individuals from higher socioeconomic classes generally attend private clinics, those from the middle classes often make use of various health insurance companies, while those from the lower classes usually attend public hospitals and outpatient clinics. The study used this tendency to define the two socioeconomic groups.
A total of 100 mothers who brought their infants to the outpatient clinic of the Department of Pediatrics, Universidade Federal de Sao Paulo, which provides free regular clinical checks, routine immunizations and health education to the low-income population, were interviewed and allocated to the LSE group. The HSE group comprised 32 mothers attending private paediatric clinics. The criteria for selection in both groups were that the child should not exceed 2 years of age and that the mother should be bottle-feeding her infant and be able to provide a feeding bottle for sampling.
There were 47 boys and 53 girls in the LSE group, and 18 boys and 14 girls in the HSE group; the median (25th and 75th percentiles) age was respectively 7.0 (4.0-10.0) months and 5.5 (4.0-9.0) months (P = 0.26, Mann-Whitney test). The mean ([+ or -] SD) of the birth weight was 3023 [+ or -] 547 g in the HSE group and 2857 [+ or -] 625 g in the LSE group (P = 0.18, Student's t-test). The median age at weaning was 1.0 month for both groups. The median number of children per family was 2.0 for both groups.
The mothers were requested to give specific details of how they prepared the feeding bottles: the type of milk powder used, whether they boiled the water used to dilute the powder, whether they added other ingredients, and who prepared the feeding bottle. …