Antibiotic consumption and resistance selection in Streptococcus pneumoniae.

Selection of antibiotic-resistant Streptococcus pneumoniae is an inescapable consequence of antibiotic use. The correlation between antibiotic consumption and selection of resistant organisms can be shown at every ecological level: patient, community, region or country. In the case of multiple resistance, the intensity of antibiotic selection is increased. However, different antibiotics may exert different selective powers. Because of this, co-selection of macrolide and beta-lactam resistance is an asymmetrical phenomenon: macrolides select more efficiently strains resistant to both macrolides and beta-lactams than aminopenicillins. The difference in rates of antibiotic resistance is also influenced by the local spread of susceptible or resistant clones; it is suggested that under mild antibiotic selection, the susceptible organisms that are more fit for host-to-host transmission could be favoured. Subsequent acquisition of resistance in these clones may rapidly increase the prevalence of resistance, and that may lead to an increase in the use of antibiotics. The reasons for antibiotic resistance are mainly the reasons explaining antibiotic consumption. A number of possible sociobiological determinants of antibiotic consumption can be identified: genetic factors in the human populations (for instance, involving different symptomatic types of infection), cultural factors and attitudes of patients towards antibiotics, sociological factors or public health factors, including incidence of other infectious diseases in the human population. Only 'excess' in the use of antibiotics should be controlled; for such a purpose, the concept, 'appropriate demand for antibiotics' (ADA) is proposed.