Optochin Resistance among Streptococcus pneumoniae Strains Colonizing Healthy Children in Portugal

Abstract

Two percent of 1,973 pneumococcus strains isolated from carriers since 2001 in Portugal were found to be optochin resistant. These strains belonged to eight serotypes (and some were nontypeable), and they had diverse genetic backgrounds. Novel optochin-resistant lineages were detected over time, suggesting that there was a continuous, although sporadic, emergence of optochin resistance.

Phenotypic and Molecular Characterization of Optochin-Resistant Streptococcus pneumoniae Isolates from Brazil, with Description of Five Novel Mutations in the atpC Gene

“…Opt MICs ranged from 8 to 64 g/ml for the Opt r S. pneumoniae strains (Fig. 1), which is in agreement with earlier reports on Opt resistance (2,7,11). On the other hand, the 16 Opt s subpopulations derived from heterogeneous cultures, as well as the susceptible reference strains S. pneumoniae ATCC 49619 and R6, showed MIC values of 1 to 2 g/ml, which were 4-to 64-fold lower than those obtained for their respective Opt r counterparts.…”

“…1). Most of the 16 different capsular types (1, 6A, 6B, 6C, 9N, 10A, 11A, 12F, 13, 14, 15C, 16F, 18C, 19A, 23A, and 23F) observed among the isolates included in the present study corresponded to types commonly found in our region (30,31), reinforcing the concept that serotype distribution among Opt r S. pneumoniae strains is mostly dependent on the epidemiological profile of each area (2,3,10,11,12). Identical serotypes were observed for the Opt r and Opt s subpopulations derived from the same culture.…”

“…Except for one, those five Opt r S. pneumoniae strains were recovered from cases of invasive pneumococcal disease, and two of them were nonsusceptible to penicillin, with one being multidrug resistant. Likewise, the occurrence of strains related to some of the PMEN clones, including Spain 9V -3 and Colombia 23F -26, was also reported among Portuguese Opt r S. pneumoniae isolates (3,11). Heterogeneity was also revealed by analysis of the pspA genes.…”

“…Moreover, Opt s subpopulations derived from heterogeneous cultures showed PFGE profiles, MLVA types, and pspA gene family types identical to those of their respective Opt r counterparts. Although this is, to our knowledge, the first report on the use of MLVA and pspA gene typing to characterize Opt r isolates, indistinguishable PFGE profiles between Opt r and Opt s subpopulations deriving from a single culture have been observed by others (2,8,11).…”

“…Since then, the isolation of Opt r S. pneumoniae from a variety of clinical sources has sporadically been reported from different locations, with an apparent increasing incidence in the last decade (2,3,7,8,9,10,11,12). The occurrence of such an atypical variant is a potential cause of misidentification of this important agent, raising questions about the accuracy of laboratory diagnosis when a single identification procedure based on Opt susceptibility testing is used.…”