Streptococcus pneunoniae resistance to erythromycin and penicillin in relation to macrolide and beta-lactam consumption in Spain (1979-1997)

Streptococcus pneumoniae resistance to penicillin and erythromycin in relat ion to beta -lactam and macrolide consumption in Spain over 19 years (1979- 1997) was studied from resistance data collected by a search of the literat ure. Antibiotic consumption was expressed in defined daily dosage (DDD)/100 0 inhabitants/day. A significant relationship (P < 0.001) between erythromy cin resistance (MIC <greater than or equal to> 1 mg/L) and global macrolide consumption (r = 0.942), as well as between high-level penicillin resistan ce (MIC greater than or equal to 2 mg/L) and global beta -lactam consumptio n (r = 0.948) was observed. The relationship between erythromycin resistanc e and macrolide consumption was due mainly to consumption of macrolides tak en twice a day (adjusted r(2) = 0.886). prevalence of high-level penicillin resistance correlated with consumption of oval cephalosporins (adjusted r( 2) = 0.877); however, there appeared to be no correlation of consumption of oral or parenteral aminopenicillins, narrow-spectrum penicillins or cephal osporins with intermediate-level penicillin resistance (MIC 0.12-1 mg/L). T he prevalence of high-level penicillin and of erythromycin resistance were also strongly correlated with each other (r = 0.903, P < 0.001). In additio n to global consumption, different categories of resistance (high or interm ediate), and the differential capability of antibiotics to select resistanc e, must be taken into account when studying antibiotic impact on bacterial populations. Although this ecological analysis is not able to demonstrate a causal relationship between antibiotic consumption and development of resi stance, it suggests that overuse of certain specific antibiotics is more li kely to be related to the increase in drug-resistant strains of S. pneumoni ae.