Clonal Spread of Resistant Pneumococci Despite Diminished Antimicrobial Use

Abstract

The effects of community-wide interventions to reduce resistance rates are poorly understood. This study evaluated the effect of reduced antimicrobial usage on the spread of penicillin-nonsusceptible pneumococci (PNSP) in four communities in Iceland. The study was performed after interventions to reduce antimicrobial usage and compared to an identical study performed 5 years before. A randomized sample of 953 children was chosen from all 2,900 1- to 6-year-old children living in four well-defined communities. The main outcome measures were nasopharyngeal carriage of PNSP and individual and community use of antimicrobials. Pneumococci were carried by 51.7% of the 743 children enrolled, and 8.1% of the pneumococci were PNSP as opposed to 8.5% in the previous study. The antimicrobial use of participants had been reduced from 1.5 to 1.1 courses/year and the overall use among children <7 years old living in the study areas from 13.6 to 11.1 defined daily dosages/1000 children per day. The prevalence of PNSP increased in the two areas furthest away from the capital area despite reduced consumption. The major risk factors for carriage of PNSP remained the same. Interventions can be effective in reducing antimicrobial use. Pandemic multiresistant clones can also spread fast in small communities with low antimicrobial use, where their appearance may be delayed compared to highly populated urban areas. Clonal spread and herd immunity are important factors to be considered in the evaluation of intervention effects.

Otitis media, tympanostomy tube placement, and use of antibiotics

“…Our earlier studies have highlighted the risk of recent antimicrobial usage on carriage of penicillin non-susceptible pneumococci [1,12] as well as an unusually high prevalence of tympanostomy tube placements in Iceland [2]. In the present paper we observed not only an association between antimicrobial prescription rates for AOM and prevalence of tympanostomy tube placements at the community level, but also changes with time between 1998 and 2003 in relation to antimicrobial usage.…”

“…Such a policy is further supported by the documented link between high consumption of antimicrobials and development of antimicrobial resistance among common pathogens [1,10,11]. A strong association between antimicrobial use for AOM and carriage of penicillin nonsusceptible pneumococci in children has been demonstrated [12]. Further knowledge about the short-and long-term impact of different treatment strategies for otitis media is important.…”

Clonal success of piliated penicillin nonsusceptible pneumococci

“…Clonal success, as estimated by the spread of particular clones, is not well understood, and it has been suggested to be due to the presence of yet-unknown virulence factors (2). In fact, antibiotic-resistant pneumococcal clones have been shown to spread despite an overall decrease in antibiotic consumption (3), suggesting that selection of these clones may also be due to factors different from those associated with antibiotic resistance.…”

Connection between Trimethoprim-Sulfamethoxazole Use and Resistance in Streptococcus pneumoniae, Haemophilus influenzae , and Moraxella catarrhalis

“…Seppälä and coworkers (23) showed a significant decline in erythromycin resistance among Streptococcus pyogenes isolates after a reduction in macrolide use in Finland. In Iceland, the prevalence of non-penicillin-susceptible pneumococci even increased in certain areas after significant reductions in total antimicrobial use owing to the spread of a resistant clone (1). On the other hand, resistance can be extremely persistent; in England, sulfonamide resistance persisted in urinary Escherichia coli isolates as long as 9 years after prescription of SXT was formally restricted (3).…”