Abstract
Streptococcus pneumoniae remains as an important cause of community-acquired bacterial infections, and the nasopharynx of asymptomatic carriers is the major reservoir of this microorganism. Pneumococcal strains of serotype 14 and serogroup 9 are among the most frequently isolated from both asymptomatic carriers and patients with invasive disease living in Brazil. Internationally disseminated clones belonging to such serotypes have been associated with the emergence and spread of antimicrobial resistance in our setting, highlighting the need for epidemiological tracking of these isolates. In this scenario, Multiple Loci VNTR Analysis (MLVA) has emerged as an alternative tool for the molecular characterization of pneumococci, in addition to more traditional techniques such as Multi-Locus Sequence Typing (MLST) and Pulsed-Field Gel Electrophoresis (PFGE). In the present study, 18 VNTR loci, as well as other previously described reduced MLVA panels (7 VNTR loci), were evaluated as tools to characterize pneumococcal strains of serotypes 14, 9N and 9V belonging to international and regional clones isolated in Brazil. The 18 VNTR loci panel was highly congruent with MLST and PFGE, being also useful for indicating the genetic relationship with international clones and for discriminating among strains with indistinguishable STs and PFGE profiles. Analysis of the results also allowed deducing a novel shorter 7 VNTR loci panel, keeping a high discriminatory power for isolates of the serotypes investigated and a high congruence level with MLST and PFGE. The newly proposed simplified panel was then evaluated for typing pneumococcal strains of other commonly isolated serotypes. The results indicate that MLVA is a faster and easier to perform, reliable approach for the molecular characterization of S. pneumoniae isolates, with potential for cost-effective application, especially in resource-limited countries.
Highlights
Members of the species Streptococcus pneumoniae, usually referred as pneumococci, colonize the human nasopharynx and are frequently associated with invasive and non-invasive infections, among children, the elderly and immunocompromised hosts [1].Antimicrobial resistant pneumococci have been emerging worldwide since the 1990’s [2]
More than 90 different capsular types have already been described among pneumococcal strains [3], antimicrobial resistance is usually restricted to a smaller number of serogroups or serotypes, among which serotype 14 and serogroup 9 are prominent due to their frequent association with both invasive pneumococcal disease (IPD) and asymptomatic nasopharyngeal carriage [4,5,6,7,8,9]
The third cluster, Ery-A, included 14.9% (13/87) of the isolates and was associated with England14-9 ST9. The occurrence of this Pulsed-Field Gel Electrophoresis (PFGE) clonal complex (CC) among Brazilian pneumococcal isolates has already been documented by Mendonça-Souza et al [33]
Summary
Members of the species Streptococcus pneumoniae, usually referred as pneumococci, colonize the human nasopharynx and are frequently associated with invasive and non-invasive infections, among children, the elderly and immunocompromised hosts [1]. Emergence of antimicrobial resistant pneumococci, especially penicillin non-susceptible pneumococci (PNSP), in our country has already been linked to the dispersion of international (Spain9V-3 ST156, Tennessee ST67 and England ST9) and regional clones (ST5401) belonging to such serotypes [18] Such clones are usually characterized by using PFGE (Pulsed-Field Gel Electrophoresis) and MLST (Multilocus Sequence Typing). Subsequent studies have proposed to use subsets of this collection, comprising 7–10 VNTR loci to be included in more practical approaches [20,21,22,23] Most of these previous studies have applied MLVA for typing pneumococcal isolates recovered from IPD outbreaks [19, 20] or from IPD cases registered during short periods of time [22,23,24]. A new panel of seven loci presenting high discriminatory power was evaluated and proposed for typing pneumococci of different serotypes
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