Abstract
Pneumococcal conjugate vaccines target the limited subset of the more than 90 known serotypes of Streptococcus pneumoniae responsible for the greatest burden of pneumococcal disease and antibiotic resistance. Following the introduction of these vaccines, serotypes not targeted were able to expand and resistance became more common within these types. Here we use a stochastic dynamic model of pediatric pneumococcal carriage to evaluate potential influences on the emergence of new resistant lineages following the introduction of a vaccine targeting more common resistant types. Antibiotic pressure was the strongest driver, with no emergence at low levels and universal emergence at high levels. At intermediate levels of antibiotic pressure, higher carriage burden and a greater degree of dual carriage promoted emergence. This may have implications for current plans to introduce childhood pneumococcal vaccination in several high-burden countries.
Highlights
Streptococcus pneumoniae is a common, widespread bacterial commensal and pathogen
This is meant to reflect a hypothetical situation in which the vaccine being introduced targets the serotypes currently associated with the great majority of antibiotic resistance, similar to the situation when PCV7 was first introduced in the USA [24]
In order to assess the potential for emergence of a new resistant strain over a range of antibiotic pressures, simulations were conducted with the advantage parameter for the vaccine type (VT)-R and non-vaccine serotype (NVT)-R strains set between 1.0 and 1.05 in increments of 0.01
Summary
Streptococcus pneumoniae (the pneumococcus) is a common, widespread bacterial commensal and pathogen. PCV use has been followed by the emergence of strains of non-vaccine serotype (NVT) in carriage [3,4] and, to a lesser degree, disease [5]. Among these are some VT lineages which have evaded the vaccine by acquiring an NVT capsule by recombination, a frequent process in pneumococci [6]. The emergence of new vaccine escape variants, those exhibiting high-level antibiotic resistance, will continue to cause concern as PCV use expands. We sought to evaluate factors that may influence the emergence of a rare antibiotic-resistant pneumococcal lineage following the introduction of vaccination targeting more common resistant types. We employ a stochastic dynamic model of pneumococcal carriage to assess the role of antibiotic pressure, carriage burden, and multiple colonization in promoting this emergence
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