Has the licensing of respiratory quinolones for adults and the 7-valent pneumococcal conjugate vaccine (PCV-7) for children had herd effects with respect to antimicrobial non-susceptibility in invasive Streptococcus pneumoniae?

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Abstract

Objectives

The aim of the study was to analyse the evolution of antibiotic non-susceptibility in Spanish invasive Streptococcus pneumoniae after licensure of respiratory-quinolones for adults and 7-valent pneumococcal conjugate vaccine (PCV-7) for immunization of children.

Methods

All invasive pneumococci received in the Reference Laboratory (January 2000–August 2007; n=12 957 isolates) were serotyped, and susceptibility to penicillin/erythromycin/levofloxacin was determined. Antibiotic consumption and PCV-7 doses/year were provided by IMS and the manufacturer, respectively.

Results

In 2000–07, PCV-7 distribution (doses/1000 inhabitants ≤59 months age/year) increased from 0.0 to 411.90, and antibiotic consumption (DDD/1000 inhabitants/day) was maintained for β-lactams (≈16), decreased for macrolides (from 4.4 to 2.7) and increased for respiratory fluoroquinolones (from 0.3 to 2.7). The increase in PCV-7 distribution correlated with a decrease in PCV-7 serotypes prevalence among invasive isolates in children (r=−0.976; P < 0.001) and adults (r=−0.905; P=0.002). This decrease in PCV-7 serotypes correlated with a decrease in penicillin non-susceptibility in children (r=0.929; P < 0.001) and adults (r=0.905; P=0.002) and with erythromycin non-susceptibility in children (r=0.833; P=0.010). Penicillin/erythromycin non-susceptibility in 2000 was significantly higher in paediatric versus adult isolates (penicillin: 51.4% versus 29.2%; erythromycin: 39.5% versus 20.4%), but similar in 2006–07 (20% to 24%). The increase in respiratory quinolones consumption correlated with the increase in levofloxacin non-susceptibility in adults (r=0.926; P=0.008) but not in children, with different non-susceptibility rates in 2007 (1.6% versus 0.0%; P=0.013).

Conclusions

This ecological analysis suggests that PCV-7 vaccination in children had a herd effect in adults, but consumption of respiratory quinolones in adults had no effect on pneumococcal susceptibility to levofloxacin in children. Penicillin/erythromycin non-susceptibility decreased along the studied period among paediatric invasive S. pneumoniae isolates to a level similar to that seen in adults.

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